6 Sc Y the Lanthanides and the Actinides By C.J. JONES School of Chemistry University of Birmingham Edgbaston Birmingham B 15 27T 1 Introduction The arrangement of this Chapter is broadly similar to that used in previous years so that following this introduction there are three main sections. The first of these is concerned with scandium and the second with yttrium and the lanthanides. This latter section is subdivided under the topic headings ‘Oxides and Solid State Studies’ ‘Catalysts and Reagents* ‘Solution Studies* ‘Luminescence Studies’ ‘Coordination Compounds* and ‘Organolanthanide Compounds*. The third and final section on the actinide elements is subdivided under the headings ‘General and Coordination Chemistry’ and ‘Organoactinide Chemistry’. The emphasis in this report has been placed primarily on molecular species and following the precedent of previous years papers relating solely to stability constant measurements and studies of binary or ternary compounds have in the main not been included.During the year there have been two additions to Gmelin’s Handbook of Inorganic Chemistry which relate to f-block elements. The first of these is entitled ‘Alloys of Uranium with Alkali Metals Alkaline Earths and Elements of Main Groups I11 and IV’ and describes alloys and intermetallic compounds of uranium formed with some main group elements.’ Binary and some ternary systems are covered and there is a chapter on UBeI3. Cermets and alloys of the U-Alsystem important in high neutron flux research reactors are also included.The second volume is entitled ‘General Properties Spectra and Recoil Reactions’ and brings together the proper- ties of thorium including electronic structure ionic radii and ionization potentiak2 Thermodynamic properties recoil reactions and the effects of ionizing radiation on thorium alloys are also covered. Although not strictly associated with the f-block elements a book has appeared which considers the theoretical bases for predicting the stabilities of superheavy elements and the approaches used for their preparati~n.~ The design and synthesis of lanthanide(II1) complexes with 18-membered ring N,-macrocycles has been re~iewed.~ Reviews have also appeared on the preparation structures and properties of the actinide^,^ on the coordination compounds of Np Gmelin Handbook of Inorganic Chemistry 8th Edn.U-Uranium Supplement Vol. B2 Springer-Verlag Berlin 1989. * Gmelin Handbook of Inorganic Chemistry 8th Edn. Th-Thorium Supplement Vol. B4 Springer-Verlag Berlin 1989. K. Kumar Superheuuy Elements Hilger Bristol 1989. M. L. Vallarino J. Less-Common Met. 1988 149 121. M. Beauvy and J. Larroque J. Nucl. Muter. 1989 166 83. 77 78 C.J. Jones and PU,~ and on the thermodynamic properties off-element hydroxides and oxide~.~ A review of the theoretical and experimental data pertaining to the extent of covalency in f-element organometallic compounds indicates that ligand-metal orbital overlap considerations are important in rigorous descriptions of their electronic structures.' However they are rarely manifest in the chemical behaviour of the compounds.Compounds of Th and U in low ( <IV) oxidation states have also been reviewed.' Two new developments during the year are the first report of a lanthanide dihydrogen complex and the first report of a direct high resolution n.m.r. observation of an f-block element. The shift and line shape of the resonance of H2 dissolved in C6D12 change upon the incremental addition of EuCpf (Cp* = v5-C5Me5). This observation is interpreted in terms of EuCpS( q2-H2) formation." 171Yb n.m.r. spectra of YbCp?(OEt,) Y~CP,*(NC~H~)~, Yb(NR2)2(OEt2)2 (R = SiMe,) Yb(NR2)2(P-NR2)2Na [Yb"R2)(P-NR2)212 [Yb(NR,),(Me2PCH2CH2PMe2)1 and YbCp?(t.h.f.) have been obtained and the spectrum of Yb(NR2),(OEt2)2 reveals a 171Yb-14N coupling constant of 118Hz." The continuing interest in the preparation of superconducting materials incor- porating yttrium or lanthanide elements is stimulating work on alkoxide complexes as components of possible molecular precursors to superconducting materials.In a more general context a review of the use of metal alkoxides as precursors to ceramic or electronic materials has appeared.12 This describes MOCVD and Sol-gel processes and the production of volatile mixed metal alkoxide derivatives. In the medical sphere the use of Gd3+ as a contrast agent in diagnostic Magnetic Resonance Imaging is encouraging work on new coordination complexes of Gd3+ which may exhibit favourable biodistribution proper tie^.'^ Also of medical interest is the development of a system for attaching 90Yto antibodies to provide a radiotherapy agent.14 2 Scandium A prominent topic among the few publications dealing with scandium has been its interaction with small molecules.A theoretical model of CO binding to Sc+ indicates that the bonding is electrostatic in nature with no more than 10% ligand to metal a-donation and essentially no metal to ligand donation.'^ The calculated C-Sc+ distance is 2.38 A. The X-band e.s.r. spectrum of ScCO at 4 K indicates that a 41; ground state is present with a low lying 411excited state in general accord with ab initio calculations.'6 Guided ion beam mass spectrometry has been used to examine N. N. Krot and D. N. Suglobov Radiokhimiyu 1989 31 1. ' T.Sato Thennochim. Actu 1988 (Publ. 1989) 149 249. J. C. Burns and B. E. Bursten Comments Inorg. Chem. 1989 9 61. I. Santos and A. fires de Matos Adv. Inorg. Chem. 1989 34 65. 10 S. P. Nolan and T. J. Marks J. Am. Chem. Soc. 1989 111 8538. A. G. Avent M. A. Edelman M. F. Lappert and G. A. Lawless J. Am. Chem. Soc. 1989 111 3423. 12 D. C. Bradley Chem. Rev. 1989 89 1317. l3 P. H. Smith J. R. Brainard D. E. Moms G. D. Jorvinen and R. R. Ryan J. Am. Chem. Soc. 1989 111,7437. 14 J. P. L. Cox K. J. Jankowski R. Kataky D. Parker N. R. A. Beeley B. A. Boyce M. W. Eaton K. Millar A. T. Millican A. Harrison and C. Walker J. Chem. Soc. Chem. Commun. 1989 797. 15 A. Mauridis J. F. Hamson and J. Allison J. Am. Chem. Soc. 1989 111 2482. 16 R. J. Van Zee and W.Welter Jnr. 1.Am. Chem. Soc. 1989 111 4519. 79 Sc Y the Lanthanides and the Actinides the reactions of Sc+ Y+ La+ and Lu+ with CH4 and C2H6.I' The major products with CH are LnCH; at low energy and MH+ at high energy. Fourier transform mass spectrometry has been used to study the chemistry of FeSc+ which was reactive towards alkenes but not alkanes." With alkenes C-H bond activation predominates over C-C activation. Two studies of aquated Sc3+ complexes have been carried out. Aqueous solutions of Sc3+ at ca. pH4 have been shown by 45Sc n.m.r. to contain Sc(H20):+ Sc( H20)5(0H)2' and Sc2( H20)8(OH):+ as the dominant species." 45Sc n.m.r. studies of the interaction between Sc(OH)2+(aq) with serine and small peptides were also carried out.Crystals of [{SC(OH,)~)~(~-OH)~](P~SO~)~.~H~O contain seven-coordinate Sc3+ ions in a pentagonal bipyramidal coordination geometry.20 The momomer units are joined through bridging OH ligands occupying adjacent equatorial sites in the edge linked bipyramids. The additional five H20 ligands on each Sc complete the coordination sphere. In the organometallic sphere the complexes ScCpTR (R = H Me) react with MCp2(CO) (M = Mo W; Cp = v5-C5H5) to give C~,M=C(R)OSCC~?.~~ The reaction of ScCpf Me with COC~(CO)~ affords CoCp(p2,v1,v1-CO)[ =C( Me)OScCp;] which contains an almost planar six-membered -Co-C-0-Sc-0-C(Me)-ring. Complexes of scandium with cyclo-octatetraenyl ligands carrying sterically-bulky substituents have also been reported. Thus 1,4-(Me3Si)2C8H$- has been found to react with ScCl,(t.h.f.) to give {Sc[1,4- (Me3Si)2C8H6]( ~-Cl)}~(p-t.h.f.) the X-ray crystal structure of which reveals a semi-bridging t.h.f.ligand (Figure 1).22 CB 1) Figure 1 The structure of {Sc[(l,4-Me,Si),C,H,](p-Cl)}2(p-t.h.f.) Sc(1)-0 = 3.056(9) and Sc(2)-0 = 2.324(7)A (Reproduced by permission from J. Chem. SOC.,Chem. Commun. 1989 1462) 17 L. S. Sunderlin and P. B. Armentrout J. Am. Chem. SOC.,1989 111 3845. 19 L. M. Lech J. R. Gord and B. S. Freiser J. Am. Chem. SOC.,1989 111 8588. l9 D. Rehder and K. Hink Znorg. Chirn. Acta 1989 158 265. 2o F. Matsumoto Y. Ohki Y. Suzuki A. Ouchi Bull. Chem. SOC.Jpn. 1989 62 2081. 2' M. A. St. Clair D. Sontarsiero and J. E. Bercaw Organometallics 1989 8 17. 22 M.C. Burton F. G. N. Cloke P. B. Hitchcock H. C. de Lemos and A. A. Sameh J. Chem. SOC.,Cbem. Commun. 1989 1462. C. J. Jones 3 Yttrium and the Lanthanides A new and convenient synthesis of SmBr from Sm203 by reaction with COBr has been de~cribed.,~ The thermodynamically favourable elimination of CO pro- vides a driving force for this reaction. A kinetic study has been carried out to investigate the mechanism of lanthanide oxide chlorination by CCl and some physiochemical properties of PmC1 were predicted on the basis of interp~lation.~~ Fluorination of some lanthanide oxides using ammonium hydrogen fluoride affords (NH,),[LnF,]-nH,O (Ln = Y La Nd and Pr) and (NH,),[CeF,].25 Oxides and Solid State St~dies.-'~O labelling of Y203 has been demonstrated by 17 0 n.m.r.studies2 and an f.t.i.r. study of "0 labelled partially reduced cerium oxide indicates the presence of peroxide and ~uperoxide.~~ The finding that YBa2Cu,07 and La,,8Sro.2Cu0 liberate O2 upon dissolution in acid has been investigated., 'In these cases no evidence was found for the presence of peroxide nor was peroxide detected in La,CuO and La2Ni0,. In L~N~,.,CU~.~O~ core level spectroscopic studies indicate that the excess positive charge is present on oxygen rather than as Cu3+.29 The magnetic structures of Nd,CuO and Nd1.97Ce0.03C~04 have been determined at 1.6 K,30using powder neutron diffraction methods. A lower limit for the Cu ordering temperature was estimated at 170 K. The synthesis of potential superconducting mixed metal oxides continues to be of interest and homogeneous reactions are being used to prepare materials for thermal processing.Superconducting YBa2Cu307- powders have been prepared from aqueous solutions containing Y3+ Ba2+ Cu2+ and oxalic acid by homogeneous co-precipitation using urea.31 Calcination of the precipitate at 900 "C for 16 h followed by sintering at 950 "C for 16 h gave a material with T = 93 K. The copper alkoxides Cu(OR) [R = CH,CH,OMe CH2CH20CH2CH20Me, and (CH,),Me] have been used in the hydrolytic synthesis of YBa2Cu307- precursors from t.h.f. solutions also containing Ba(OPr') and Y,O(OPr'), .32 Lower formation tem-peratures for YB~,CU,O,-~ are possible from materials prepared by this route.33 X-Ray studies of YSr2Cu307-x YBaSrCu307-, and YC~S~CU,O~-~ suggest that Ca2+ ions are too small to lead to structures giving supercond~ctivity.~~ Several other mixed metal oxide systems have been described.(SrLa)(MoO,) is a complex perovskite which contains MOO octahedra.,' The material is cubic with a0 = 7.932(1) A and shows Curie-Weiss behaviour with peff= 1.72(1) pusconsistent with the presence of Mo" centres. In the complexes K,,[Ln(GaW,,039H2)2].xH20 (Ln = 23 M. J. Parkington K. R. Seddon and T. A. Ryan J. Chem. Soc, Chem. Commun. 1989 1823. 24 D. M. Laptev T. V. Kiseleva V. F. Goryushkin N. M. Kulugin and N. G. Kulagina. Russ. J. Inorg. Chem. 1989 34 27. 25 S. J. Patwe B. N. Wani U. K. Rao and K. S. Venkateswarlu Can. J. Chem. 1989 67 1815. 26 S. Yang K.D. Park and E. Oldfield J. Am. Chem. Soc. 1989 111 7278. 27 C. Li K. Domen K. Maruya and T. Onishi J. Am. Chem. Soc. 1989 111 7683. 28 D. C. Harris and T. A. Vanderah Inorg. Chem. 1989 28 1198. 29 G. R. Rao M. K. Rajumon D. D. Sarma and C. N. R. Rao J. Chem. SOC.,Chem. Commun. 1989,1536. 30 M. J. Rosseinsky K. Prassides and P. Day J. Chem. SOC.,Chem. Commun. 1989 1734. 31 R. S. Liu C. T. Chang and P. T. Wu Inorg. Chem. 1989 28 154. 32 S. C. Goel K. S. Kramer P. C. Gibbons and W. E. Buhro Inorg. Chem. 1989 28 3619. 33 H. S. Horowitz S. J. McLain A. W. Sleight J. D. Pruliner P. L. Gai M. J. Von Kavelaar J. L. Wagner B. D. Briggs and S. J. Poon Science 1989 243 66. 34 G. Nordin L. Rondaccio and E. Zangrando Inorg. Chim. Acta 1989 164 1.3s J. H. Choy and S. T. Hong J. Chem. Soc. Dalton Trans. 1989 2335. Sc Y the Lanthanides and the Actinides 81 La Ce Pr Nd Sm Eu Gd Tb Dy Tm Yb) which have been prepared from K,GaW,,O,, magnetic data are consistent with the presence of Ln3+ ions.36 The syntheses and structures of some tantalum containing compounds have also been described. La3Ta05(OH)Cl and Pr3Ta0,C1 have been prepared by chemical trans- port and studied by high resolution electron Single crystals 'LaTa,O,,' contain layers of composition [Ta22062]14- with holes partially or fully occupied by La3+ ions.38 Reports of compounds with the later transition metals include BaNiDy,05 and BaNiLu,O .39 The former contains nickel in an octahedral coordina- tion environment while the latter belongs to the BaCuLn20s structural series and contains nickel in a tetragonal pyramidal coordination environment.BaCoY20 is also of the BaCuLn,O structural family while BaCoGd20s and BaCoDy20S belong to the BaNiLn205 structural family.,' BaCoHo205 BaCoYb20, and BaCoEr,O have also been ~ynthesized.,~ The first two compounds have the BaCuSm,O,-type structure and the last a BaNiLn,O,-structure. The Dy atoms in Ba,Dy2Al4OI5 have been found42 to have an octahedral coordination environment and the synthesis and structure of Cs2Lil4[Tb3OI4] has been 151 Eu Mossbauer spectra have been reported for EuI,(t.h.f.) [EuCp,(t.h.f.)], [EuCp*(t.h.f.),(p-I)I2 EuCpT EuC~*(t.h.f.)(OEt~).~ Broad absorptions were observed arising from spherical paramagnetic relaxation at a rate approaching the Mossbauer timescale (9.7 x lo- s) except in the case of [EuCp*(t.h.f.)] which exhibited a narrow line spectrum with a quadruple interaction of -12.9 mms-'.A Curie-Weiss temperature of 3.28 K was found for EuCpT. The use of XPS to determine the Ce"'/Ce'v ratio in materials is usually limited by the small magnitude of the shift in binding energy between Ce"' and CeIV. However the use of a modified Auger parameter and the relative 4d,,,/4d,/ peak area ratio allows this ratio to be extracted from the data.45 The magnetic properties of the bis-adducts of {Ln[CF3C(0)CHC(CF3)O]3L}fl(Ln = Eu Gd; L = 1H-imidazoyl-1-oxyl-3-oxide 2-R-4,4,5,5-tetramethyl-4,5-dihydro-radical with R = Ph Et) have been investigated., In the Gd'" complex there is weak ferromagnetic coupling between the radical and the metal.The radicals are antiferromagnetically coupled to one another. Extended Huckel calculations on Er,Rh,Cl indicate that treating Er merely as a three-electron donor does not account for all the geometric features of the structure it is also necessary to include Er atomic orbitals in the P-Ln2C13N (Ln = Y Gd) have been obtained from heating LnCl, LnN and Ln in sealed container^.^' P-Y2C13N contains infinite chains of edge sharing Y octahedra 36 J. Liv Z. Zu B. Zhao and Z. Liu Inorg. Chim. Acta 1989 164 179. 37 B. Langenbach-Kuttert G. Steinmann W. Mertin and R. Gruehn Z. Anorg. Allg. Chem. 1989,573 119. 38 U. Schaffrath and G. Gruehn 2. Anorg. Allg. Chem. 1989 573 107. 39 H.K. Muller-Buschbaum and 1. Reiter 2. Anorg. AIIg. Chem. 1989 572 181 40 H. Mevs and H. K. Muller-Buschbaum 2. Anorg. AIIg. Chem. 1989 573 128. 41 H. Mevs and H. K. Miiller-Buschbaum 2. Anorg. Allg. Chem. 1989 574 172. 42 I. Riiter and H. K. Miiller-Buschbaum Z. Anorg. AIlg. Chem. 1989 573 89. 43 S. Voigt R. Werthmann and R. Hoppe 2.Anorg. Allg. Chem. 1989 574 65. 44 A. F. Williams F. Grandjean G. J. Long T. A. Ulibarri and W. J. Evans Inorg. Chem. 1989 28 4584. 45 C. A. Strydom and H. J. Strydom Inorg. Chim. Acta 1989 161 7. 46 C. Benelli A. Coneschi D. Gatteschi L. Pardi P. Rey D. P. Shum and R. L. Cardin Inorg. Chem. 1989 28 272. 47 S. Lee W. Jeitschko and R. D. Hoffmann Inorg. Chem. 1989 28 4094. 48 H. J. Meyer N. L. Jones and J.D. Corbett Inorg. Chem. 1989 28 2635. C. J. Jones as found in Y2C13 with the nitrogen atoms positioned in tetrahedral metal sites above and below the shared metal edges. Y,I,,Ru which is isostructural with Sc,Cl,,B has been prepared from the reaction between Y,Ru and Y13 at 800- 950 0C.49 The reaction also affords Y6IloRu which contains edge (p-I)bridged Y6II2 clusters centred by Ru and condensed into infinite chains uia bridging iodides (Figure 2). The Y,Ru cluster shows a tetragonal compression of 0.21 8 compared to an idealized octahedron. Calculations indicate that this arises from Y-Y inter- actions. The crystal structures of LaBr, La2Br, and LaBr3 have been determined.50 Figure 2 (a) The (110) section of Y,I,,Ru with the Y-Ru bonds emphasized; (b) A view of approximately normal to that of Figure 2(a) showing the Y,I,,Ru chains (Reproduced by permission from Znorg.Chem. 1989 28 631) T. Hughbanks and J. D. Corbett Inorg. Chem. 1989 28 631. so K. Kramer T. Sahleid M. Schulz W. Urland and G. Meyer Z. Anorg. AIIg. Chem. 1989 575 61. Sc Y the Lanthanides and the Actinides 83 LaBr has the CeCl structure while La2Br is like Pr21s. LaBr crystallizes in a 2H2-MoS type of structure with trigonal prismatically coordinated La atoms and an La-Br distance of 3.07 A. An X-ray structural study of HoAl3ClI2 shows that the Ho3+ ion is eight coordinate with a square antiprismatic arrangement of chloride ligands derived from tetrahedral AlC1 units bound as bidentate ligands in the lattice.,' Catalysts and Reagents.-Work on olefin oligomerization olefin-oxide oligomeriz- ation hydrocarbon coupling hydrogenation and oxidation catalyst systems has appeared.Kinetic stereocontrol in the polymerization of butadiene by an Nd- A1 catalyst system has been in~estigated.~~ The ratio of the formation rates of 1,4-cis and 1,4-trans units depends linearly on the current monomer concentration. The oligomerization of ethene to alkylcyclopentanes and/ or alkylcyclohexanes has been effected using YbCIJAlEtCl as a Ziegler-Natta type catalyst.53 The presence of CO during the reaction is essential otherwise only linear oligomers are obtained. High molecular weight poly(ethy1ene oxide) can be produced from ethylene oxide using the Y[OP(=O)(OCH2CH(Et)CH2Me)2]3/AlBu;/H,0 catalyst system.54 The catalytic activity is highly dependent upon the molar ratio of the three catalyst components.The oxidative conversion of methane to C2 hydrocarbons and the selectivity of this conversion has been found to be sensitive to the distribution of oxygen within La-promoted MgO catalysts.55 An increase in C2 selectivity but a decrease in methane conversion is associated with an increase in the CH4:02 ratio. A deuterium isotope effect has been observed in the coupling of CH4 over a samarium oxide catalyst; making mechanistic interpretations of earlier studies more diffi~ult.~~ Lanthanide promoted hydrogenation catalysts have been prepared from the direct reaction of Fe Ni Cu or Ag powder with Eu or Yb in liquid ammonia." The oxidation of water to O2 by Ce'" in a reaction mediated by thermally activated Ru02.H20* has been the subject of a kinetic This indicates that Ru02-yH20* particles act as microelectrodes through which electrons are irreversibly removed from water then reversibly transferred to Ce'".A synergistic effect on the reactions of CO with O2 and NO with CO is reported when LaMno.6Cuo.403 is used instead of either LaMnO or La2Cu04.59 Interest in the use of lanthanides as reagents to effect organic transformations has continued. The reactions of metallic Ln (Ln = Ce Nd Sm Yb) with olefins and aromatic ketones have been investigated and Yb found to be the most reactive of the metals tested.60 Reduction reactions and the cleavage of C-C and C-0 bonds were observed.The mechanism of formation of 2-benzoyl-1 -phenylpropanol 51 D. Hake and W. Urland Angew. Chem. In!. Ed. Eng. 1989 28 1364. 52 Z. M. Sabirov N. Kh. Minchenkova and Y. B. Monakov Inorg. Chim. Acta 1989 160 99. 53 W. Keim Z. Chen and Z. Chen J. Chem. SOC.,Chem. Commun. 1989 1923. 54 Y. Zhang X. Chen and Z. Chen Inorg. Chim. Acta 1989 155 263. 55 V. R. Choudhary S. T. Choudhari A. M. Pajput and V. H. Rone J. Chem. SOC. Chem. Commun. 1989 1526. 56 A. Ekstrom and J. A. Lopszewicz J. Am. Chem. SOC.,1989 111 8515. 57 H. Imamura T. Mihara M. Yoshinobu Y. Sakata and S. Tsuchiya J. Chem. Soc. Chem. Commun. 1989 1842. 58 A. Mills and S. Giddings Inorg. Chim. Acta 1989 158 49. 59 M. Mizuno Y. Fujiwara and M. Misono J. Chem. SOC.,Chem.Commun. 1989 316. 60 Y. Chauvin H. 0.Rivier and L. Saussino Inorg. Chim. Acta 1989 161 45. C. J. Jones in an LaBr assisted aldol reaction has been investigated.61 The reaction involves an LaBr,:benzaldehyde:t.h.f. complex. In addition CeC1 and LaCl have been found to promote the phase transfer catalysed carbonylation of benzyl bromide.62 Samarium compounds may be employed to effect coupling reactions. Thus Sm12 promotes intramolecular coupling reactions to form functionalized carbocycle~.~~ The electrochemical coupling of carbonyl compounds to give 1,2-diols in high yields is catalysed by SmCl,.64 The addition of CeC1 to Gringard reactions of ketones has been found to suppress side reactions especially enoli~ation.~~ The enantio- selective reduction of ketones (acetophenone octan-2-one and butan-2-one) with NaBH may be achieved using fac-A-tris(4-l-menthyloxy)-l-( p-tolylbutane-1,3-dionato)lanthanoid(rII) (1) as the Lewis acid catalyst.66 Me Me R = I-menthyl Me (1) Solution Studies.-Several spectroscopic studies have utilized Judd-Ofelt theory and the oscillator strengths and Judd-Ofelt parameters (ClA ) for the two hypersensitive -+ transitions of Er"' (4115/2 2H11/4 and 4115,2 + 4G11/2)have been measured and correlated with the induced chemical shift produced by Er"' in n.m.r.studies.67 In another study of the links between the hypersensitive pseudo-quadrupole transition in the electronic spectra of lanthanide ions and the induced chemical shift of lanthanide shift reagents in n.m.r.the oscillator strengths and Judd-Offelt para- meters of Nd(O,CR) (R = CH3 CH2Br) have been determined.68 The absorption 61 A. J. Fry and M. Susla J. Am. Chem. SOC.,1989 111 3225. 62 I. her and H. Alper J. Am. Chem. SOC.,1989 111 927. 63 G. A. Molander and C. Kenny J. Am. Chem. Soc. 1989 111 8236. 64 E. Leonard E. Dufiach and J. Perichon J. Chem. Soc. Chem. Commun. 1989,276. 65 T. Irnarnoto N. Takiyarna K. Nakarnura T. Hatajirna and Y. Karniya J. Am. Chem. SOC.,1989 111 4392. 66 H. Okawa T. Katsuki M. Nakarnura N. Kurnagoui Y. Shuin T. Shinrnyozu and S. Kida J. Chem. Soc. Chem. Commun. 1989 139. 67 D. F. Mullica G. A. Wilson and C. K. C. Lok Znorg. Chim. Acra 1989 163 139. 68 D. F. Mullica G. A. Wilson and C.K. C. Lok Znorg. Chim. Acta 1989 156 159. Sc Y the Lanthanides and the Actinides 85 spectra of single crystals of Na3[Ho(dpa)3]~NaC104~10H,0 (dpaH2 = pyridine-2,6-dicarboxylic acid) have been studied and f-f transition probabilities assigned on the basis of Judd-Ofelt theory.69 A comparison with the results of solution studies indicates that the mechanism of the only hypersensitive transition is vibronic. A number of n.m.r. studies of solution species have appeared. The pseudo contact shifts of the 31P and 170 nuclei in [Ln(PPP),(H20)J7- (PPPH5 = P3010H5 tri- phosphoric acid) have opposite signs indicating that the coordinated water occupies an axial site in s~lution.~’ Accordingly the PPP ligand occupies the equatorial region. The exchange of various P-diketonate ligands between Eu(P-diketonate) and free P-diketonate has been studied by ‘H n.m.r.and I9F n.m.r. spectro~copy.~~ 139La n.m.r. has been used to study the complex formed from LaCl and 18-crown-6 in MeOH.72 The results provide evidence that a C1 ion is present in the first coordination sphere. The n.m.r. data give an equilibrium constant value for complex formation which is in good agreement with previous determinations. Variable pressure 139La n.m.r. studies of La3+ complexation by 4-hydroxypyridine-2,6-dicarboxylicacid (H’dcp) have also been carried out.73 These indicate that chelation is the rate determining step in complex formation following a rapid ion-pair forming pre- equilibrium. A study of the e.s.r. and magnetic properties of Dy(hfac),( NITPh)2 (hfacH = hexafluoroacetylacetone; NITPh = 2-R-4,4,5,5-tetraphenyl-4,5-dihydro-1H-imidazoyl-1-oxyl-3-oxide indicates that coupling between the spins of metal ion and the nitronyl radical is occurring.74 Some studies of lanthanide ions in aqueous solution have appeared.The water exchange rate in octa-aqualanthanide ions from Tb3+to Tm3+ has been studied by 17 0 n.m.r. at pressures up to 250 MPa.75 A similar interchange associative mechanism was found for all the ions and the importance of steric crowding in determining water and Me,NCHO exchange rates was considered. The hydrolysis of Nd3+ in 3 mol dmP3 LiC104 at 60 “C has been studied.76 In order to explain the results at low concentrations (<0.3 mol dmP3 Nd3+) the species Nd(OH)’+ Nd2(OH)2+ and Nd,(OH)tz were proposed while at higher concentrations the latter is replaced by Nd6(0H)ko+.Potentiometric studies indicate that the hydrolysis of Pr3+ in LiC104 solution leads to Pr(OH)2+ Pr,(OH)’+ Pr2(OH)i+ and Pr,(OH):+ .77 The AKUFVE-LISOL system comprising a mixer centrifuge constantly circulating sol- vent and aqueous phases through a scintillation based analytical system provides a means of measuring partition coefficients in continuous solvent extraction processes. This apparatus has recently been used to study the extraction of Tb3+, Ho3+ and Lu3+ from 1 mole dm-’ aqueous (Na,H)C10 by acetylacetone in benzene.78 Radio- chemical methods have also been used to determine the distribution of 15,Gd ions between (BuO),PO and aqueous phosphate solutions providing formation constant 6Y A.Mondry Znorg. Chim. Acta 1989 162 131. 70 J. A. Peters A. Sinnema A. P. G. Kieboom and H. Bekkum Inorg. Chim. Acra 1989 160 7. ” V. Ya Kavum I. V. Kalinovskaya and V. E. Karasev Russ.X Inorg. Chem. 1989 34 951. 72 2. Chen H. Dettman and C. Detsellier Pol-vhedron 1989 8 2029. Y. Ducommun L. Helm G. Laurenczy and A. E. Merbach Inorg. Chim. Acta 1989 158 3. C. Benelli A. Coneschi D. Gatteschi 0.Guillou L. Pardi and P. Rey Znorg. Chim. Acra 1989 160,.1. 73 74 75 C. Cossy L. Helm and A. E. Merbach Inorg. Chem. 1989 28 2699. 76 L. Ciavatta R. Porto and E. Vasca Polyhedron 1989 8 2701. 77 L. Ciavatta R. Porto and E. Vasca Polyhedron 1989 8 983. 78 Y. Albinsson Acta Chem.Scand. 1989 43 919. 86 C.J. Jones data for Gd-phosphate complexes.79 On the basis of the results obtained the use of phosphate buffers in the study of trivalent actinide or lanthanide hydrolysis is deemed inadvisable. Ion exchange studies have provided evidence for complex formation between Eu"' and A,Ph or SbPh in benzonitrite solution.'' In contrast to the order found with high oxidation state d-block metal ions SbPh forms a stronger complex with Eu"' than does AsPh,. Measurements relating to the selectivity of crown ethers and cryptands for lan- thanide ions continue to appear. The macrocyclic effect in lanthanide complexes with 12- 15 18- and 21-membered crown ethers has been studied in propylene carbonate by stability constant measurements for the crown complexes and for the corresponding linear polyethers.81 The linear polyethers form less stable complexes than the macrocyclic ligands and no 1:2 stoichiometry complexes could be identified with the linear ligands.The colorimetric complexant 2-(2-thiazolylazo)-4-methyl-phenol has been used in a study of lanthanide complexation by 18-cr0wn-6.~~ The stability constants of the lanthanide 18-crown-6 complexes were found to decrease with increasing lanthanide atomic number. The stabilities of the 2.2.2 2.2.1 and 2.1.1 cryptate complexes of Ln'" (Ln = Eu Sm Yb) have been compared wth those of the corresponding complexes of the monocyclic ligand 1 ,lo-diaza- 18-cr0wn-6.~~ The cryptands show little selectivity among the oxidation state (III) ions but electrochemical studies reveal some selectivity among the oxidation state (11) lan-thanides.The rate of dissociation of [2.2.1]-cryptand ([2.2.1] = 4,7,13,16,21-penta oxa-l,l0-diazobicyclo-[ 8.8.51-tricosane) from La[2.2.1]( NO3) has been studied using 'H n.m.r. methods.84 The dissociation obeys first order kinetics over the pH range 1 to 13 but above pH 9 hydrolysis to La[2.2.1](OH) species occurs. Complexes of lanthanide ions with macrocyclic nitrogen containing ligands have also been studied. The 'H n.m.r. spectra of Ln,(OEP) (OEPH2 = octa-ethylporphyrin Ln = Ce Pr Nd Sm Eu) provide evidence for inter-ring steric crowding and limited rotation of the OEP alkyl groups.85 The tribasic penta- dentate 'expanded-porphyrin' ligand (2) has been used to prepare complexes with Gd"' Eu'" and Sm"' which are water stable unlike their porphyrin containing counterparts.86 The stability of the Gd"' complex offers the promise of a new type of compound for use as a contrast agent in Magnetic Resonance Imaging (MRI).Also of relevance to medical applications is a report of the synthesis of the Gd3+ complex of (3 n = n2 = 0; R = H) which offers a model for H,DOTA-protein conjugates [R' = amide linked protein; H,DOTA is (3 n = n2 = 0; R = H R' = OH)] used in MRI." The stability constant of the complex with (3) is some lo4 times lower than that with H,DOTA but the relaxivities at high field are similar. 79 L. S. Bingler and R. H. Byrne Polyhedron 1989 8 1315. 'O G. F. Payne 0. L. Keller J.Halperin and W. L. Wolsey J. Chem. SOC.,Chem. Commun. 1989 50. 81 J. C. G. Biinzli and F. Pilloud Inorg. Chem. 1989 28 2638. '*-E. Ohyoshi and S. Kohata Polyhedron 1989 9 8 1561. 83 I. Marolleau J. P. Gisselbrecht M. Gross F. Amoud-Neu and M. J. Schwing-Weill J. Chem. SOC. Dalton Trans. 1989 367. 84 R. A. Torres and P. A. Baisden Inorg. Chem. 1989 28 2807. 85 J. W. Buchler M. Kihn-Botulinski J. Loffler and M. Wicholas Inorg. Chem. 1989 28 3710. 86 J. L. Sessler T. Muroi and G. Hemmi Inorg. Chem. 1989 28 3390. 87 A. D. Sherry R. D. Brown C. F. G. C. Geroldes S. H. Koenig K. T. Kuan and M. Spiller Inorg. Chern. 1989 28 620. Sc Y the Lanthanides and the Actinides Me Me 90Y is a p-emitter with potential applications in radiotherapy.In a search for therapeutic radiopharmaceutical preparations the binding of Y3+ by differing ring size macrocyclic ligands (3 R = H,R' = OH) has been studied.14 The stability constants for complex formation were found to be log K = 24.9 (n = n2 = 0) 19.6 (n = 1 n2 = 0) and 16.3 (n = n = 1) in 0.1 mol dmP3 NMe4N0 solution^.'^ The reagent (3 n = n2 = 0; R' = OH; R = (CH2),NHC(O)CH,OCH2C5H3N-CH=CH2-2,6) has been linked to B72.3 antibodies and the antibody conjugate is being evaluated as a 90Y3+ carrier for cancer therapy. Luminescence Studies.-In doped 38% PbO-62% Si02 glass the stimulated emission cross sections of the potential laser transitions ('F, 'S2) -'I8 and 'F -.+ '1 in Ho3+ are relatively high.88 This is attributed to the narrow effective line widths produced in the presence of Pb2+ as a network modifier.After excitation to the 4f5d configur- ation of Pr3+ in a Gd202S matrix the ion relaxes rapidly to the 4f2 configuration where 3P0 and 'D2 emission occurs.89 Single crystal absorption and emission spectra have been measured from Sm(AP)J (AP = antipyrine) and Sm(AP),(C10J3 and crystal-field interaction parameters were obtained." Chiral discrimination has been observed in the intermolecular energy-transfer process from a racemic terbium tris-(dipicolinate) complex to a resolved ruthenium tris-( o-phenanthroline) com- plex." A large amplification of the optical activity of the system may be obtained through the induction of optical activity into a large population of excited racemic terbium complexes by a small population of excited ruthenium complexes.The effect of pH of the luminescence of Tb(dpa) (dpaH = pyridine-2,6-dicarboxylic acid) in aqueous media has been in~estigated.~ The tris-ligand formulation is the most emissive and the emission intensity decreases rapidly at pH values below 6. The hydration of Eu"' complexed by dicarboxylic acids has been studied by 8X F. Fermi G. Ingleto C. Aschien and M. Bettinelli Inorg. Chim.Acta 1989 163 123. a9 G. Blasse and A. Meijersink Inorg. Chim. Acta 1989 160 29. 90 M. T. Beny and F. S. Richardson Mol. Phys. 1989 66 703. 91 D. H. Metcalf S. W. Snyder S. Wu G. L. Hilmes J. P. Riehl J. N. Demas and F. S. Richardson J. Am. Chem. Soc. 1989 111 3082. 92 T. K. Trout J. M.Belloma R. A. Faltysek E. J. Parks and F. E. Brinckman Znorg. Chim. Acta 1989 155 13. C. J. Jones luminescence methods.93 The mono-malonate complex has 2.3 fewer water molecules than the free hydrated Eu3+ ion. In the cases of 1 :1 complexes with succinate glutarate and adipate 1.5 molecules of water were displaced. The effects of counter ions M+ on the fluorescence spectra of [Eu(PhC(O)CHC(Me)O),]- have been studied for M = Na K Rb and CS.~,The results are consistent with the larger ions producing a reduction in the symmetry of the anion. The structures of the three triboluminescent complexes piperidinium tetrakis(beneoylacetonoito)europate hexakis(antipyrine)terbium tri-iodide and hexa-aquodichloroterbium chloride are de~cribed.~~ The first and last of these complexes contain eight-coordinate metal ions with tetragonal antiprismatic geometries.The remaining complex contains an octahedrally six-coordinate Tb"'ion. The complexes Ln(cca)X (Ln = Sm Eu Gd Tb Dy; ccaH = coumarine-3-carboxylic acid; X = C1 ClO, NO3) and Ln(cca),X have been s~nthesized.~~ The latter compounds exhibit less luminescence than the former. Although the quantum yield for ligand luminescence increases the quantum yield of metal luminescence decreases as a result of energy transfer. A macrocyclic ligand (4) which incorporates two 2,2'-bipyridyl- 1 ,l'-dioxide units forms a stable COPh Eu"' complex which exhibits fluorescence with a total quantum yield of 0.016 when excited at 294 nm.97 LnCp (Ln = Sm Eu; n = 2,3) exhibit chemiluminescence during oxidation by O2.98 Fluorescence was observed from LnCp in frozen solutions.Room temperature luminescence from solutions of ScCpTCl has also been repor- ted.99 The quantum yield was estimated as 0.01 with an excited state lifetime of 2.0 ps in solution at 298 K. Time resolved fluorescence immunoassay (TRFIA) is an important application of lanthanide fluorescence used in medical diagnostics. In this context it has been found that improved sensitivity is obtained by multiple labelling with a Eu3+ complex in a time resolved heterogeneous immunofluorometric assay of cy -fetoprotein in serum using monoclonal antibodies."' 93 P. P. Barthelemy and G. R. Choppin Inorg. Chem. 1989 28 3354. 94 G. M. Murray L. L. Pesterfield N.A. Stump and G. K. Schweitzer Znorg. Chem. 1989 28 1994. 95 A. L. Rheingold and W. King Inorg. Chem. 1989 28 1715. 96 C. B. Castelloni and 0. Carugo Inorg. Chim. Acta 1989 159 157. 97 M. Pietraszkiewcz S. Poppalardo P. Finocchiaro A. Mamo and J. Karpiuk J. Chem. SOC.,Chem. Commun. 1989 1907. 98 R. G. Bulgakov S. P. Kuleshov V. N. Khandozhko I. P. Beletskaya G.A. Tolstikov and V. P. Kazukov Dokl. Akad. Nauk SSSJ? 1989,304 114. 99 B. W. Pfennig M. E. Thompson and A. B. Bocarsly J. Am. Chem. SOC. 1989 111 8947. 100 E. P. Diamondis R. C. Morton E. Reichstein and M. J. Khosravi Anal. Chern. 1989 61 48. Sc Y the Lanthanides and the Actinides 89 Coordination Compounds.-The order in which topics are covered in this section differs from that used last year.Boron-hydride ligands are considered first followed by monodentate ligands with nitrogen then oxygen donor atoms. Following this complexes of bi- then poly-dentate ligands are described with macrocyclic ligands appearing at the end of the section. Amongst the continuing efforts to place lanthanide coordination chemistry into a more systematic structural framework the concept of a 'steric coordination number' for a ligand has been proposed."' This parameter is derived from the solid angle comprising the Van der Waals spheres of the ligand atoms. Such 'ligand effective radii' have been defined on the basis of bond lengths in 274 structurally characterized complexes of lanthanides in oxidation states (11) and (111) and of actinides in oxidation states (111) and (IV).The steric coordination number concept may be used to assist in the comparison of structures and the prediction of bond lengths. In the synthetic sphere the borohydride complexes Ln(BH4),.4N2H (Ln = La Gd Lu) and Ln( BH4),.4( NH2CH2CH2NH2) have been rep~rted.'~~,'~~ The reactions between B10H14 and liquid ammonia solutions of Ln2+ (Ln = Eu Yb) have been investigated and Yb(p-H)2BloH12(MeCN)6 has been isolated and characterized by an X-ray study.'04 The Yb2+ ion is coordinated to six nitrogen atoms from the MeCN ligands and is described as forming two three-centre two-electron bonds to a B,,H;; ion. Structural studies of several thiocynate complexes exhibiting different lanthanide ion coordination numbers have been described.The complexes [Et,N],-[Ln(NCS)6]'SOl (Ln = Er Or Yb SO1 = C6H6 C~HSF C,H,Me Or c6H~Cl) have been prepared and are isomorphous containing six-coordinate lanthanide ions.'05 The [Yb(NCS),I3- ion contains an octahedral Yb3+ ion bound to the N-atoms of the linear NCS-ligands. The two seven-coordinate complexes [Me,N],_ [Ln(NCS)7]-C6H6 (Ln = La Pr) are also isomorphous and in [La(NCS),I4- the La3+ ion is bound to the nitrogen atoms of the NCS- ligands to give a mono-capped trigonal prismatic geometry.'06 The three complexes [Me,N],[ Ln( NCS),] (Ln = Dy Er Yb) are also isostructural and contain seven-coordinate metal ions bound to the nitrogen atoms of the NCS- ligands to give a distorted pentagonal bipyramidal geometry.lo7 The eight-coordinate complexes Et4N[Ln( NCS),( H20)4] (Ln = Nd Eu) are again isomorphous and crystals of the neodymium complex contain Nd3+ ions with a square antiprismatic coordination geometry."' Two of the four N-bonded NCS- ligands occupy mutually cis positions on one square face and the remaining two occupy mutually trans positions on the other square face water-oxygens complete eight-coordination around the Nd3+ ion.Eight-coordinate lanthanide complexes containing six NCS- ligands have also been obtained. Thus the complexes [Me,N],[Ln(NCS),(MeOH)(H,O)] (Ln = La Ce Pr Nd Sm Eu Gd Tb Dy 101 J. Marcalo and A. Pires Polyhedron 1989 8 243. 102 A. Kurbonbekov T. Kh. Alikhanova and U. Mirsaidov Russ.J. Znorg. Chem. 1989 34 347. LO3 A. Kurbonbekov T. Kh. Alikhanova U.Mirsaidov and U. I. Budnikova Russ. J. Inorg. Chem. 1989 34 624. 104 J. P. White 111 H. B. Peng and S. G. Shore J. Am. Chem. SOC.,1989 111 8946. 105 H. Arai Y. Suzuki N. Matsumura T. Takeuchi and A. Ouchi Bull. Chem. SOC.Jpn. 1989 62 2530. 106 F. Matsumoto T. Takewchi and A. Ouchi Bull. Chem. SOC.Jpn. 1989 62 2078. 107 F. Matsumoto N. Matsumura and A. Ouchi Bull. Chem. SOC.Jpn. 1989 62 1809. 108 A. Ouchi Bull. Chem. SOC.Jpn. 1989 62 2431. 90 C. J. Jones Er) are isostructural and contain lanthanide ions bound to six nitrogen atoms from the NCS- ligands and two oxygen atoms from the MeOH and H20 ligands to give a square antiprismatic geometry.'" The lanthanide amide complexes Ln[N(SiMe3),],Cl(t.h.f.) (Ln = Eu Gd or Yb) and Y[N(SiMe,),)]Cl(t.h.f.) have been prepared from LnC13 or YCl and Li[N(SiMe,),]."' Structural studies of the Gd and Yb complexes confirm the presence of dimeric Ln(p-Cl,)Ln cores in these complexes.The lanthanide ions are in an approximately trigonal bipyramidal coordination environment with one bridg- ing C1- and the oxygen of the t.h.f. occupying the axial sites. The remaining bridging C1- and two N(SiMe,) ligands occupy the equatorial sites. The reactions between LnCl and Napz (pzH = pyrazole) or NaMe2pz(Me2pzH = 3,5-dimethylpyrazole) afford polymetallic products of general formula Ln3( p -Me,pz) (q2-Me2pz),(p3-0)-Na,(L) (Ln = Y Ho Yb Lu and L = t.h.f.; or Ln = Y Ho Yb and L = Me,pzH)."O X-Ray diffraction studies of two complexes (Ln = Yb with L = t.h.f.and Ln = Ho with L = Me,pzH) reveal similar structures in which an oxygen atom lies at the centre of a trigonal bipyramid comprising three equatorial lanthanide ions bound to the oxygen and two apical sodium ions linked to the lanthanide by bridging pyrazolide ligands. Each sodium ion is also bound to either a t.h.f or a Me,pzH ligand and each lanthanide ion is also bound to an q2-Me2pz- ligand. Two reports of structural studies on compounds containing pnicnogen oxide ligands have appeared. The X-ray crystal structure of Eu( NO3),( Ph3AsO),-4H20 reveals the presence of three bidentate nitrate ligands along with the three Ph,AsO ligands giving a coordination number of nine for the Eu3+ ion. The coordination geometry may be described as distorted octahedral if the nitrate ions are presumed to occupy single coordination sites."' The Ph,AsO ligands then occupy mutually meridional positions in the octahedron.A series of phosphine oxide complexes [Ln(Ph3PO)5C1][FeC1,] (Ln = La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er and Y) has also been prepared.Il2 An X-ray study of the complex with Ln = La reveals a distorted octahedral geometry about the six-coordinate La3+ ion. The polymeric heterobimetallic mixed lanthanide-mercury complexes {[Hg2-LnL,(NO,),]} (Ln = La to Gd; L = C4H6N0 derived from 2-pyrrolidone) and (Ln = Y and Tb to Yb) have been ~ynthesized."~ {[Hg3Ln2L6(N03)6]n} The struc- tures of the complexes with Ln = Eu and Tb were determined. They contain nine-coordinate lanthanide ions in an essentially tricapped trigonal prismatic coordi- nation environment.The complete structures consist of polymeric chains cross linked by nitrate ligands and partial structures showing the chains are illustrated in Figure 3. The zero-field splitting parameters D and A were obtained from e.p.r. measure- ments. Among the compounds containing purely inorganic ligands the double lanthanum barium perxenate complex La2Ba( Xe0,),.3H20.Na2CO3 has been 109 H. C. Aspinall D. C. Bradley M. B. Hursthouse K. D. Sales N. P. C. Walker and B. Hussain J. Chem. SOC.,Dalton Trans. 1989 623. 'lo H. Schumann P. R. Lee and J. Loebel Angew. Chem. In?. Ed. Engl. 1989 28 1033. 'I1 U. Casellato R. Graziani U. Russo and B. Zarli Znorg. Chim. Acta 1989 166 9. 112 H. K. Wang M. J. Zhong X.Y. Jing J. T. Wang R. J. Wang and W. G. Wang Znorg. Chim. Acta 1989 163 19. D. M. L. Goodgme D. J. Williams and R. E. P. Winpenny J. Chem. SOC.,Dalton Trans. 1989 1439. Sc Y the Lanthanides and the Actinides ,--1. Figure 3 (a) A partial structure showing the polymer chain in [EuHg,( C4 JO),(NO3)31 with the nitrate groups omitted for clarity; (b) A partial structureshowing the polymer chain in [Tb,Hg,(C,H,No),(No,),]" with the nitrate groups omitted for clarity (Reproduced by permission from J. Chem. SOC.,Dalton Trans. 1989 1439) reported along with the preparation of La4(Xe06)3-3H20. Na2C03.'I4 A structural study has shown that the hydroxide complex Nd2(0H),(C104)2~5H20 contains eight-coordinate Nd3+ ions in an irregular coordination geometry and linked via bridging ClO ligand~."~ There has been increased interest in lanthanide alkoxide complexes and a number of papers have appeared on this topic.This is partly as a result of the search for molecular species which might form the basis of new synthetic routes to ceramic superconductors or which may be useful in other fabrication processes such as MOCVD. The direct synthesis of yttrium alkoxides from the metal and alcohols has led to polymetallic yttrium alkoxide complexes two of which have been structurally chrac- terized. The reaction between yttrium metal and 2-propanol affords Y,O(OPr'), which has been characterized by 'H I3C and ''Y n.m.r. spectroscopy."6 Crystals of the complex contain a square pyramidal Y5cluster containing a basal p,-oxygen 114 L.D. Shuslov N. S. Tokmacheva Sh. Sh. Nabiev E. K. Il'in V. D. Kilimov and V. P. Ushakov Russ. J. Znorg. Chem. 1989 34 946. 115 I. Csoregh E. Huskowska A. Ertan J. Legendzicwicz and P. Kierkegaard Acta Chem. Scand. 1989 43 829. 116 0.Poncelet W. J. Sartain L. G. Hubert-Pfalzgraf K. Folting and K. G. Caulton Znorg. Chem. 1989 28 263. C.J. Jones 012 011 Figure 4 The Y,O1 substrucrure in Y,O(OPr'), (Reproduced by permission from Inorg. Chem. 1989 28 263) as illustrated in Figure 4. In addition to the five terminal OPr' ligands there are four p3-OPr' ligands capping triangular faces and four p2-OPri ligands bridging the edges of the square base. Yttrium turnings also react directly with 2-methoxyethanol in toluene to give [Y(OC2H40Me)3]lo which contains a cyclic array of ten yttrium centres as shown in Figure 5.Il7 This compound can also be prepared by alcoholysis of Y,O(OPr'), .Atempts to synthesize Y(OBu') have failed because of heterolytic C-0 cleavage reactions leading to yttrium oxides.l18 However the more robust Si-0 bond in 0-SiPh3 allows [Y(OSiPh,),(t.h.f.),]-t.h.f.to be isolated. This complex contains three t.h.f. ligands in a mutuallyfac arrangement to give a distorted octahedral geometry about six-coordinate Y3+. The large Y -0-Si angles [average 171( l)"] and short Y-OSi distances [2.12(2) A] were taken to indicate extensive Y-O(Si) multiple bonding in the compound. A series of cerium alkoxides Ce(OBu'),(NO,)b(solvent),Nad(a = 1 to 6; b = 0 to 3; c = 2 4; d = 0 2; a + b = 4 + d) have been identified along with Ce2(OBu'),Na and Ce3(OBu')lo0.'19 In C~(OBU')~(NO~)~(HOBU')~ the Ce4+ ion is eight-coordinate and the coordination geometry may be described as distorted octahedral if the two trans bidentate nitrates are each considered to occupy one coordinate site.In Ce(OBu'),( ~-OBU')~(~~-OBU')~N~ the Na+ ion is coordinated to two terminal and the two bridging alkoxides of the binuclear cerium complex as illustrated in Figure 6. In the complex Ce(OBu'),( ~-OBU')~( ~~-0Bu')~Na~-(MeOCH2CH20Me)2 the Ce4+ ion is in a six-coordinate distorted octahedral en- vironment with Na' ions capping two O3 faces as shown in Figure 7. The thermal decomposition of Ce(OCBu\) affords [Ce(OCHBu\)J2 (90%)from isobutene elimi- nation and [Ce(OCHBu',),H] (10%) from Bu',CO elimination.'20 The structure of [Ce(OCHBu;),] contains two pseudo-tetrahedral Ce3+ ions each carrying two terminal OCHBub ligands and linked via two p2-OCHBu' ligands.The Ce202 moiety is planar with 0-Ce-0 = 74.3(1)' and Ce-0-Ce = 105.7(1)". Ce(OSiPh,),.x(MeOCH,CH20Me) (0.5 < x < 1.0) has been prepared and 117 0. Poncelet L. G. Hubert-Halzgraf J. C. Doran and R. Astier J. Chem. Soc. Chem. Commun. 1989 1846. 118 M. J. McGeary P. S. Coan K. Folting W. E. Streib and K. G. Caulton Znorg. Chem. 1989 28 3283. 119 W. J. Evans T. J. Derning J. M. Olofson and J. W. Ziller Znorg. Chern. 1989 28 4027. I20 H. A. Stecher A. Sen and A. L. Rheingold Inorg. Chem. 1989 28 3282. Sc Y the Lanthanides and the Actinides Figure 5 The structure of [Y(OC2H,0Me),], (Reproduced by permission from J.Chem. Soc. Chem. Commun. 1989 1846) Figure 6 The structure of Ce(OBu'),(p-OBu'),(p3-OBu'),Na (Reproduced by permission from Inorg. Chem. 1989 28 4027) C. J. Jones C c34 Figure 7 The structure of C~(OBU'),(~-OBU')~( p3-OBu'),Na2( MeOCH,CH,OMe) (Reproduced by permission from Inorg. Chem. 1989 28 4027) structurally characterized.121 The Ce4+ ion exhibits a distorted octahedral six-coordi- nation geometry with short Ce-O(Si) bond lengths [2.098( 10)-2.133(10) A] and longer Ce-O(C) bond lengths [2.575(10) and 2.587(10) A]. In addition to work on alkoxide complexes some results using aryloxo ligands have also been reported.The sterically demanding ligand 2,6-dimethylphenoxide (ArO-) has been used to prepare halide- and oxide-free Y3+ complexes.'22 The complex Y(OAr),(t.h.f.) contains Y3' in a distorted octahedral geometry with a mutually fac arrangement for the OAr ligands. The complex [Y(p-0Ar)-(OAr)2(t.h.f.)]2 was also obtained and contains five-coordinate Y3+ centres linked by bridging phenoxide oxygens. In this case the coordination geometry at Y is distorted square pyramidal. Some general methods for the preparation of monomeric Yb2+aryloxide complexes have been de~cribed.'~~ These involve reactions between Yb and TlOAr' (Ar' = C,H2Bu:-2,6-Me-4) or Yb{N(SiMe3)2}2(OEt2)2 and Ar'OH. The complex Yb(OAr'),( t.h.f.) has an unprecedented square pyramidal stereo- chemistry around Yb2 whereas Yb(OAr'),(Sol) (Sol = t.h.f.or OEt2) have approxi- mately tetrahedral geometries. A calixarene complex of Eu3+ has been ~ep0rted.l~~ This was obtained from the reaction between Eu3+ ions and p-tertiarybutylcalix-[4]-arene (H,L) to give [Eu2( HL),(dmf),].7 dmf (dmf = N,N-dimethylformamide) which contains two Eu3+ centres bridged by one phenoxy oxygen from each of two calixarene ligands as shown in Figure 8. The X-ray crystal structure of Ce( NO3),( MeOCH2CH20Me)2 has been deter- mined and the molecule found to contain a ten-coordinate Ce3+ ion bound to three 121 P. S. Gradeff K. Yunlu A. Gleizes and J. Galy Polyhedron 1989 8 1001. 122 W. J. Evans J. M. Olofson and J. W. Ziller Inorg. Chem. 1989 28 4308. 123 G.B. Deacon P. B. Hitchcock S. A. Holmes M. F. Lappert P. MacKinnon and R. H. Newnham J. Chem. SOC.,Chem. Commun. 1989 935. 124 B. M. Furphy J. M. Harrofield M. I. Ogden B. W. Skelton A. H. White and F. R. Wilner J. Chem. SOC.,Dalton Trans. 1989 2217. Sc Y the Lanthanides and the Actinides Figure 8 The structural arrangement of the dimeric calixarene complex [Eu(p-tertiarybutylcalix-[4]-arene)(d.m.f.),12 (Reproduced by permission from J. Chem. Soc. Dalton Trans. 1989 2217) bidentate nitrate and two bidentate dimethoxyethane ligand~.'~' The five bidentate ligands form an approximately trigonal bipyramidal array around the cerium. Isomorphic crystals of the Dy3+ and Ho3+ proline complexes [Ln(C5H9N02)2(H20)5]C13 (Ln = Dy Ho) have been prepared.The holmium com- plex contains eight-coordinate Ho3+ ions in a distorted bicapped trigonal-prismatic geometry.'26 The carboxylate groups in the proline ligands act as bridging groups linking the Ho3+ ions in polymeric chains. The effect of structural features on the hypersensitive f-f transitions of these compounds was evaluated. Several papers refer to P-diketonate complexes of the lanthanides. Studies of the mass spectral fragmentation patterns of the complexes Ln(acac) (acacH = pentane-2,4-dione) provide evidence that the complexes containing Sm Eu and Yb undergo an oxidation state change from Ln'" to Ln".'27 Complexes con- taining Ce or Gd do not exhibit this behaviour and the Ln3+ oxidation state is preserved. The crystal structure of Gd[CF,C(O)CHC(CF,)O],L (L = 2-ethyl-4,4,5,5-tetramethyl-4,5-dihydro- 1H-imidazolyl-1-0xy1-3-oxide) reveals that linear chains of Gd[CF,C(O)CHC(CF,)O] moieties linked by bridging nitroxide radicals are present.'28 Several models are described which account for the anti- ferromagnetic coupling observed in this compound.The molecular structure of 125 P. S. Gradeff K. Yunlu T. J. Deming J. M. Olofson J. W. Ziller and W. J. Evans Inorg. Chem. 1989 28 2600. 126 J. Legendziewicz T. Gtowiak E. Huskowska and D. Cong-Ngoan Polyhedron 1989 8 2139. 127 S. Lis A. S. Ptaziak and M. Elbanowski Inorg. Chim. Acta 1989 155 259. 128 C. Benelli A. Caneschi D. Gatteschi L. Pardi and P. Rey Inorg. Chem. 1989 28 275. C. J. Jones [Nd4(p3-OH)2(p2 pl-acac)6(acac)4] reveals two dinuclear Nd,(OH)(acac) units linked by two triply bridging pyramidal p-OH ligands and by two bridging-chelating acac ligand~.',~ The metal atoms are eight-coordinate with a distorted square- antiprismatic geometry as illustrated in Figure 9.The bifunctional ligands (Pr'O),P(=O)CH,S(=O),,R (R = C6Hll or C6H4Me-4 and n = 2; R = C6H4Me-4 and n = 1) and Ph,P(=0)CH2S(=0),NMe2 have been prepared and their com- plexation reactions with La( NO3) and Gd( NO3) in~estigated.'~' In the latter case Gd( NO,),[ Pri(O),P(O)CH,S(O)(C,H,Me-4)]~H2O was isolated and a structural study carried out. This revealed that the Gd3+ ion is nine-coordinate and bound to three bidentate nitrate groups ,a water molecule and the bifunctional ligand bound in a bidentate manner by the phosphoryl and sulphinyl oxygens.n Figure 9 The structure of Nd4(p-OH)2(p2,p,-acac),(acac) (Reproduced by permission from Polyhedron 1989 8 2183) A number of heteroleptic hydro-trispyrazol- 1-ylborate complexes of the lan- thanides have been described and some examples structurally characterized. The air and moisture stable complexes Ln(HBpz,),(acac) (Ln = La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Tm Lu and Y) have been prepared.131 Structural studies show that the lanthanide ions are eight coordinate and that the compound with Ln = Ce has an essentially bicapped trigonal prismatic coordination geometry as shown in Figure 10 while that with Ln = Yb has a structure more in accord with a square antiprismatic structure as shown in Figure 11.'H n.m.r. data show that intramolecular ligand reorganization occurs in solution. The heteroleptic tropolonate complexes L~(HBPZ,)~(O,C,H~) (Ln = La Ce Pr Nd Sm Eu Tb Yb Lu Y) 129 0. Poncelet and L. G. Hubert-Pfalzgraf Polyhedron 1989 8 2183. S. Karthikeyan R. R. Ryan and R. T. Paine Znorg. Chem. 1989 28 2783. M. A. J. Moss C. J. Jones and A. J. Edwards J. Chem. SOC.,Dalton Trans. 1989 1393. 130 131 Sc Y the Lanthanides and the Actinides Figure 10 The structure of Ce(HBpz,),(acac) (Reproduced by permission from J. ,Chem. SOC. Dalton Trans. 1989 1393) Figure 11 The structure of Yb(HBpz,),(acac) (Reproduced by permission from J. Chem. Soc. Dalton Trans. 1989 1393) have also been prepared and the molecular structure of the Yb complex deter- mined.'32 The Yb3+ ion is eight-coordinate with a distorted square antiprismatic geometry.The complexes are all air and moisture stable but those containing La Ce and Pr are insoluble in CH2C12. The binuclear heteroleptic oxalate complexes 13' M.A. J. Moss and C. J. Jones Polyhedron 1989 8 117. 98 C. J. Jones [{L~(HB~Z~)~]~(C~O,) Mass (Ln = Y Sm Dy Yb or Lu) have been ~ynthesized.',~ spectral data support the binuclear formulation while 'H n.m.r. data are consistent with the binding of the bridging oxalate to form a five-membered chelate ring as was the case for the tropolonate complexes. Continuing this series to incorporate bidentate monoanionic ligands with smaller 'bite angles' the heteroleptic carboxylate complexes Ln{HBpz,},(O,CR) (Ln = Y Sm Eu Yb Lu and R = Ph; Ln = Y Yb Lu and R = Me) were prepared.', Yb[Hbpz3I2(O2CPh) is monomeric in the solid state containing an eight-coordinate Yb3+centre with a coordination geometry which lies on the geometric pathway from square antiprismatic to dodecahedral.The hexanuclear mixed metal copper-lanthanide complexes Cu,Ln2L8-(LH)4(OH)2(N03)4(Hz0)2 (Ln = Dy or Gd; LH = 2-(1H)-pyridone C5H,NO) have been prepared and their solid state structures determined.',' The lanthanide ions are nine-coordinate with a coordination geometry approximating to face-capped square-antiprismatic. The copper ions occupy two different sites both being five- coordinate. The 2-pyridone ligand is trinucleating with the oxygen bound to lan- thanide and one copper ion and the nitrogen bound to a second copper ion.A number of papers have been concerned with the use of amino acids or their derivatives as ligands for lanthanide ions. The crystal structures and fluorescence spectra of Ln2(~-Glu)2(C104)4-9Hz0 (L-Glu = glutamate; Ln = Nd Eu Dy Ho) have been investigated and the absorption spectra analysed on the basis of Judd-Ofelt Crystals of Ho( ~-Asp)C1,-6H,0 (L-As~= aspartate) contain eight-coor- dinate Ho3+ ions bound to five H20 molecules and three carbonyl oxygens from different bridging L-As~ ligands.',' o-Hydroxyacetophenone-(N-benzoy1)gly-cinehydrazone (abzgH,) forms the complexes [Ln(ab~gH~)C1~(H~0)~]ClLa, (Ln = Pr Nd Sm and Eu) and Ln(abzg)(OH)(H,O) in which the ligand is proposed to be neutral and bidentate or dianionic and tridentate re~pectively.'~~ The complexes [Ln(b~gH)~[C1~(0H,)-nH~0 (Ln = La Pr Nd Sm Eu Gd Tb Dy or Y n = 1 or 2 and bzgH = N-benzoylglycine hydrazide) have been re~0rted.l~~ The ligand bzgH is thought to be bidentate in all the complexes.Other polydentate ligand complexes which have been reported include [Ln(Hapfh),Cl]Cl (Ln = La Pr Nd Sm Eu Gd and Dy; Hapfh = 2-acetylpyridine-2'-furoylhydrazone, 2-OC4H,C( =O)NHN=C( Me)C5H4N-2') and Ln(apfh),(OH).'40 Infra red studies indicate that in both cases the ligand is bound in a tridentate manner. Potentiometric spectroscopic and t.g.a. data have been reported for trivalent lanthanide complexes of 1,5-bis(o-carboxyphenyl)-3-acetyl and formazan (o-H0,CC6H,N=N-C(COMe)=NNH-C6H4-o-Co2H) 1-(0-carboxypheny1)-5-(o-hydroxyphenyl)-3-acetyl formazan (o-H02CC6H4N=N-C(COMe)=NNHC6H4-o-OH).'41Ferrocene has appeared as a component of ligand 133 M.A. J. Moss and C. J. Jones Polyhedron 1989 8 2367. 134 M. A. J. Moss and C. J. Jones Polyhedron 1989 8 555. 135 D. M. L. Goodgame D. J. Williams and R. E. P. Winpenny Polyhedron 1989 8 1531. 136 I. Csoregh M. Czugler P. Kierkegaard J. Legendzicwicz and E. Huskowska Acfa Chem. Scand. 1989 43 735. 137 I. Csoregh P. Kierkegaard J. Legendzicwicz and E. Huskowska Acta Chem. Scand. 1989,43 636. 138 T. R. Rao and G. Singh Transition Met. Chem. 1989 14 471. 139 T. R. Rao G. Singh and I. A. Khan Transition Met. Chem. 1989 14 15. 140 B. Singh and P.K. Singh Transition Met. Chem. 1989 14 411. 141 S. S. Badawy Y. M. Issa and H. M. Abdel-Fattah Transition Met. Chem. 1989 14 401. Sc Y the Lanthanides and the Actinides systems for lanthanide ions. Formylferrocene benzoylhydrazone (CpFeCq5-C5H4CH=NNHC(0)Ph = LH) forms complexes of formula LnL,-nH,O (Ln = Y or a lanthanide element) in which the ligand binds in the deprotonated enolate form.142 The binding of alkaline earth and lanthanide ions to the ferrocenyl contain- ing cryptand (5) has been studied by electro~hemistry.'~~ The binding an electron Fe transfer processes are summarized in Scheme 1. A linear correlation was found between LnK and the radius :charge ratio of the bound cation. Pyridinaldazine (paa) and pyrrolaldazine (pyaaH,) complexes of lanthanide ions have been described.14 [Ln(L)Cl,(H20),]C1~rnH20 (Ln = Ce Nd Sm Yb; L = paa or pyaaH, n = 2,4,rn = 0 1,2,3.5) were prepared from LnC13.The reaction between YbC13.6H20 and pyaaH afforded Yb,(pyaa)Cl,( H20)4.2H20. (5) + M"+ K [(5):M"+] (f) = free cryptand potential (c) = cryptate redox potential Scheme 1 The first structural study of a lanthanide complex with a tetradentate ligand has appeared.'45 The crystal structure of [C5H,,NH2][Er(sa12en)2] (sal,enH = N,N'-ethylenebissalicylaldimine) shows that the metal ion is eight-coordinate with a distorted square antiprismatic geometry. The sa1,en ligands are coordinated in part to both square faces as illustrated schematically in Figure 12. The structures of Ca[ Er(egta)(OH,)],.12H,0.Me2C0 (egtaH = 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioicacid) and Ca[ Nd(egta)( OH2)I29H20 have also been determined.'46 The former complex contains nine-coordinate erbium while the latter contains ten-coordinate neodymium. There has been increasing interest in complexes of the lanthanides with macro- cyclic ligands and a number of new compounds of this type have been reported. 142 M. Yongxiang M. Zhongqian Z. Gang M. Yun and Y. Min Polyhedron 1989 8 2105. 143 C. D. Hall N. W. Sharpe I. P. Danks and Y. P. Sang J. Chem. SOC.,Chem. Commun. 1989 419. 144 M. M. Dawod F. I. Khalili and A. F. Seyam Polyhedron 1989 8 21. 145 S. Mangani A. Takeuchi S. Yamada and P. Orioli Inorg. Chim. Acta 1989 155 149.146 C. K. Shaver and 0.P. Anderson J. Chem. SOC.,Dalton Trans. 1989 185. 100 C. J. Jones Figure 12 A schematic diagram of the coordination environment of the Er3+ ion in (C H1oN H2)Ed42en 2 The complexes LII(NCS)~L[Ln = Y or Eu L = (6) R = Me] contain two kinds of nine-coordinate molecule with different macrocycle conformations as shown in Figure 13.14' Yttrium ions can be used in the template synthesis of the N4macrocycle (7) from 2,6-diacetylpyridine and hydrazine to give [Y(7)( N03)3]-2H20.'48 Varying the reaction conditions can lead to the formation of the open chain ligands (8) and (9) found in the complexes [Y(8)(H20)2]C13.2H20 and [Y(9)(N03),].2H20 and [Y(9)2]C1,.[Y(9),]Cl3.2H2O. A structural study of the yttrium complex of (6) (R = Me) [Y(C22H26N6)(02CMe)2H200.5]C104 reveals two different structures in Me &Me N N \ Me Me (6) R = H Me (7) Me &Me N 0 \ Me 147 G.Bombieri F. Benetollo A. Polo L. deCola W. T. Hawkins and L. M. Vallarino Polyhedron 1989 8 2157. 148 W. Radecko-Paryzek Polyhedron 1989 8 1217. Sc Y the Lanthanides and the Actinides C(1011 Figure 13 The two diflerent macrocycle conformations found in Eu"' (NCS) . (Reproduced by permission from Polyhedron 1989 8 2157) the crystal 1atti~e.l~~ The metal is nine-coordinate with a coordination geometry best described as a monocapped square antiprism. Yttrium acetate is effective in stimulat- ing the template synthesis of the macrocyclic ligand (6) from 1,2-diarninoethane and the dicarbonyl substituted pyridine precursor.A series of bis-porphyrin complexes of Ce4+ has been prepared from cerium acetylacetonate complexes and tetraphenylporphyrin or tetra-p-chlorophenylp~rphyrin.~~~ In the case of hexadecahydrotetrabenzorphyrin a bis-cerium (111) 'triple-decker' complex is also found. The crystal structure of Ce(OEP)(TPP) (OEPH2 = octaethylporphyrin L 49 G. Bombieri F. Benetollo W. T. Hawkins A. Polo and L. M. Vallarino Polyhedron 1989 8 1923. I50 J. W. Buchler A. D. Cian J. Fischer P. Hamrnerschmitt J. Loffler B. Scharbert and R. Weiss Chern. Ber. 1989 122 2219. 102 C. J. Jones TPPH2 = tetraphenylporphyrin) reveals a staggered conformation for the two por- phyrin ligands giving a square antiprismatic coordination geometry for Ce4+.The Eu and Gd complexes of the macrocyclic Schiff base (6) (R = Me) have been prepared and the complex Gd(6)(02CMe)2Cl.4H20 characterized by X-ray crystal- 10graphy.I~ The Gd3+ ion is ten-coordinate being bound to the six nitrogen atoms of the macrocycle and to two bidentate acetate ligands. The complex exhibits a relaxivity in aqueous solution comparable with that of the Gd3+ aqua ion and is thus of interest as a potential contrast agent in MRI. The template condensation of f7-n /-N 0 0 NT 2,6-diformyl-p-creso1 with 3,6-dioxa- 1,8-0ctanediamine to give ( 10) may be effected by Ln3+ (Ln = La to Tb).15' The structure of the Gd complex shown in Figure 14 reveals that a homobinuclear complex is formed within the macrocycle.Lumines- cence studies of the Eu complex provided evidence of Eu-Eu interactions. The Pr3+ complex of the hexadentate macrocycle (1 1) have been ~ynthesi2ed.l~~ The crystal Figure 14 The structure of Gd,(lO)(NO,),-H,O (Reproduced by permission from J. Chem. Soc. Chem. Commun. 1989 1531) 151 I. A. Kohwa S. Folkes D. J. Williams S. V. Ley C. A. O'Mahoney and G. L. McPherson J. Chem. Soc. Chem. Cornmun. 1989 1531. 152 F. Benetollo G. Bombieri L. DeCola A. Polo D. L. Smailes and L. M. Vallanno Inorg. Chem. 1989 28,3447. Sc Y the Lanthanides and the Actinides SmCp (t.h.f.) Me Cp (t.h.f.) Sm (11) (12) structure of [Pr( NO,),( MeOH)( 12)]C10,-0.5MeOH~0.5H20 has been determined and reveals a saddle shaped conformation for the ligand with an 11-coordinate P8' ion bound also to methanol and two bidentate nitrate ions.0rganolanthanides.-Once again reports of organolanthanide compounds are domi- nated by complexes containing cyclopentadienide or a derivative of cyclopen- tadienide as a ligand. Attempts have been made to prepare Ce4+ complexes of cyclopentadienide by the reaction of NaCp with (NH4)2[ce(No3)6].125 The reaction involving respective 1:1 equivalents of these reagents results in reduction of Ce4+ to Ce3+ and the 6 1 reaction affords CeCp3(t.h.f.) in high yield. The 5:1 reaction affords thermally unstable CeCp,( NO,),Na( t.h.f.) . More success was achieved by using OBu' as a co-ligand and CeCp,(OBu') may be prepared in high yield from Ce(OBut),( NO,),(t.h.f.) and NaCp.The trinitrate Ce( NO,),(OBu')t.h.f. reacts to give a mixture of CeCp,(OBu') and CeCp3(0Bu').153 The X-ray structure of the latter complex reveals a distorted tetrahedral arrangement of the four ligands around the Ce4+ ion. The tetrakis-cyclopentadienyl anions Na[LnCp,].t.h.f. (Ln = La Nd) Na[ PrCp,] and NaCp.Na[CeCp,].t.h.f. have been prepared.154 Structures based on LnCp,(p,q'-C,H,)Na(t.h.f.) (n = 0,l) are proposed. In the solid state the structure of Yb( q5-C5H4Me) consists of a Yb3+ ion trigonally coordinated to the centroids of three q5-C5H,Me ligands.', Other complexes of monosubstituted cyclopen-tadienide ligands include La( ButC5H4),(t.h.f.) Sm( ButC5H4), [Sm( ButC5H4),C1] [Lu( Bu'C,H~)~C~] and Lu( Bu'C,H4)C1,.2t.h.f.which have been prepared by the reactions between the appropriate lanthanide trichloride and NaBu'C,H4 .156 The 2,4-dimethyl-penta-l,4-dienyl complex Nd(C7HI ,)C12.0.33t.h.f. has also been pre- pared and crystallizes with a hexameric Nd6(C,H,,)&1,,.t.h.f. unit which contains two Nd3C1 units connected by two chloride bridges.'57 The C7H11 ligands are bound in the q5-mode. Synthetic routes to mono-pentamethylcyclopentadienyl-yttrium,-lanthanum and -cerium complexes have been explored.'58 Reaction of LnR (R = hydrocarbyl) 153 W. J. Evans T. J. Deming and J. W. Ziller Organornetallics 1989 8 1581. 154 K. Jacob M. Glanz K. Tittes K. H. Thiels I. Pavlik and A. LyEka Z. Anorg. A&. Chern. 1989 577 145. 155 A. Hammel W. Schwarz and J.Weidlein J. Organomet. Chem. 1989 363 C29. 156 A. L. Wayda J. Organornet. Chem. 1989 361 73. 157 J. Sieler A. Simon K. Peters R. Taube and M. Geitner J. Organornet. Chem. 1989 362 297. 158 M. Booiu N. H. Kiers H. J. Heeres and J. H. Teuben J. Organornet. Chern. 1989 364,79. 104 C.J. Jones with Cp*H generally gave LnCpzR. However YCp*(C6H4CH2NMe2-2)2 was obtained from Y(C6H4CH2NMe2-2),and Cp*H. The heteroleptic cyclopentadienyl- idenyl lanthanide complexes LnCp,Ind (Ln = Sm Dy Ho Er Yb; Ind = C9H7) have been prepared from LnCp,Cl and are less air sensitive than their counterparts LnCp Other heteroleptic complexes have been prepared which contain a steri- cally bulky hydrocarbyl ligand and the X-ray structures of LaCp"[CH(SiMe,),] (Figure 15) and LaCp*[CH( SiMe3)2]2(t.h.f.) have been determined.I6' The former n V Figure 15 The structure of LaCp*[CH(SiMe,),] showing the methyl hydrogens ofthe Me groups associated with the agostic interactions but omitting the other methyl hydrogens for clarity.(Reproducedby permission from Organometallics 1989 8 255) constitutes the first structurally characterized example of a salt-free and solvent-free monocyclopentadienyl lanthanide alkyl complex and is prepared by reaction of the latter complex with Me,SiI. Both complexes contain unusual agostic Si-C bonds which help to stabilize the sterically unsaturated lanthanum ion. Agostic interactions were also found between yttrium and the C-H bonds of the N-CH groups in YCp*( o-C6H4CH2HMe2) .I6' Thermolysis of this compound affords N,N-dimethyl-benzylamine and YCp*[o-C,H4CH2NMe(CH2-~)][~-o-(C6H4CH2NMe(CH2-~)] YCp*(t.h.f.) in which both aryl and N-methylene bridging groups have been formed as shown in Figure 16.The lanthanoid alkyl complexes Ln[CH(SiMe,),],(p-Me)Li(pmdeta) (Ln = La or Sm,pmdeta = N,N N',N",N"-pentamethyl-diethylenetriamine)have been pre- pared.'62 A structural study shows that the samarium complex has approximately tetrahedral coordination environments around Sm and Li with a near linear (174(2)") Sm-Me-Li unit. Alcoholysis of LnCpT[CH(SiMe,),] (Ln = La or Ce) by Bu'OH 159 Z. Zhennan W. Zhongzhik D. Baohu and Y. Zhongwen Polyhedron 1989,8 17. 160 H. van der Heijden C. J. Schaverien and A. G. Orpen Organometallics 1989 8 255.161 M. Booij N. H. Kiers A. Moefsma J. H. Teuben W. J. J. Smeets and A. L. Spek Organometallics 1989 8 2454. 162 P. B. Hitchcock M. F. Lappert and R. G. Smith J. Chem. SOC. Chem. Commun. 1989 369. Sc Y the Lanthanides and the Actinides n Figure 16 The structure of YCp*[o-C,H4CH2NMe(~-CH*)][~-o-C,H,CH,N-CH*)]-YCp*t.h.f. (Reproduced by permission from Organornetallics 1989 8 2454) affords [LnCp*( p2-OBu')(OBu')]2 .163 The X-ray structure of the Ce compound reveals a pseudo-tetrahedral geometry about each Ce atom based on the Cp* ligand a terminal OBu' ligand and two p,-OBu' ligands. The two terminal OBu' ligands are in a cis orientation with respect to the Ce(p-OBu'),Ce unit. The aryloxy derivatives Ce( R)(OAr) (R = Cp* or 1,3-diphenyl-2-methylindene; Ar = 2,6-Bu\C6H3) may be prepared from Ce(OAr) and LiR.'64 The reaction of CeCp*(OAr) with LiCH(SiMe3)2 or NaN(SiMe3)2 affords CeCp*(R')2 [R'= CH(SiMe3) or N(SiMe,),] of which the former is a catalyst for ethene but not propene polymerization.The X-ray structures of CeCp*(R2) (R2 = OAr R') show that in each case the metal is trigonally coordinated to a Cp* ligand and the two ligands R2. A series Of complexes YbCp2(02CR) (R = Me CF3 Ph c6F6 C6Br5 MeO2CC6F4 C6H2Me,-2,4,6 NC5H4-2) have been prepared by oxidation of YbCp,(MeOCH,CH,OMe) with M(02CR) (M = Hg" n = 2 or M = Tl' n = l)? The complexes with R = Me CF3 Ph or C6F5appear to be dimeric. Other heteroleptic complexes containing bidentate uninegative oxygen ligands include LnCp,(sal)3- and LnCp,(fur),- (Ln = Nd Yb; n = 1,2; salH = salicylaldehyde; furH = furfuryl alcohol) have been synthesized and shown to be 163 H.J. Heeres J. H. Teuben and R. D. Rogers J. Organornet. Chern. 1989 364,87. 164 H. J. Heeres A. Meetsma J. H. Teuben and R. D. Rogers Organornetallics 1989 8 2637. 165 G. B. Deacon and D. L. Wilkinson Aust. J. Chem. 1989 42 845. 106 C. J. Jones thermally unstable with respect of disproportionation according to equations (1) and (2) where L = sal or fur.'66 2LnCpL + LnCp,L + LnL (1) 3LnCp,L -+ 2LnCp + LnL (2) Mass spectral studies of YbCp,L and YbCpL2 (LH = acetylacetone 2,2,6,6-tetramethylheptane-3,5-dione 1,l,l-trifluoroacetylacetone benzoylacetone 4-benzoyl-3-methyl-l-phenyl-5-pyrazolone and trifluoroacetyl-a-thiophene) indicate that thermal disproportionation reactions occur to give YbCpf and YbLf The structures of [YbCp,Cl] and [YbCp2BrI2 have been determined and show a pseudo-tetrahedral arrangement of the two p-halide and two Cp ligands about Yb.168The magnetic properties of the complexes are explained by ligand field splitting of the Yb3+ free-ion 2F,,2 ground state and a small molecular field parameter.The first example of a ?r-bonded phosphacyclopentadienyl complex of a lan- thanide ion has been rep01ted.l~~ The complexes Ln(Me4C4P),(p-C1),Li(Sol),(Ln = Y Sol = MeOCH2CH,0Me; Ln = Lu Sol = OEt,) were prepared from LnC1 and LiPC,Me4. The complex with Ln = La could not be prepared. There is continuing interest in the synthesis and reactivity of lower oxidation state lanthanide compounds.The syntheses and solid state structures of the solvated Sm" complexes Cp,*Sm(0CSH8) (OCSH8 = dihydropyran) and SmCpq (OC5HI0) have been reported.'70 The disolvate exhibits a pseudo-tetrahedral coordination environ- ment around the Sm" ion whereas the monosolvate has a trigonal coordination environment counting the Cp* ring centroids as occupying single coordination sites. The unsolvated complexes LnCpq . (Ln = Eu or Sm) may be prepared from their diethyl ether adducts by heating to 100°C in toluene under reduced pressure."' The desolvated species LnCpT (Ln = Yb Sm) react with N20 to give (LnCpf),(p-0). The chalchogenide bridged complexes (YbCpT),(p-E) (E = S Se Te) were also prepared and exhibit no magnetic exchange across the chalchogenide bridge.The X-ray structure of (YbCp,*),(p-Se) reveals a near linear Yb-Se-Yb bridge (171.1') with the YbCp moieties mutually staggered about the bridge. The average Yb-Se distance is 2.621 A. Evidence for ethylene binding to EuCpT has been obtained from n.m.r. studies." Absolute metal-ligand bond disruption enthalpies have been measured for bis-pentamethylcyclopentadienylsamarium hydrocarbyl hydride dialkylamide alkoxide halide thiolate and phosphide cornple~es.'~~ Hydrocarbon functionaliz- ation by dinuclear Sm"/Sm"' oxidative addition is only expected to be exothermic in special cases. Alkyl halides are more reactive and YbCpTOEt undergoes atom- abstractive oxidative addition with the alkyl and aryl halides RX (R = hydrocarbyl) to give YbCpfX and YbCp*X2 along with Cp*H and R-R RH or R(-H) (ie.166 Z. Wu Z. Ye and Z. Zhou Polyhedron 1989 8 2109. 167 L. Yang L. Doi H. Ma and Z. Ye Organometallics 1989 8 1129. 168 H. Lueken J. Schmite W. Lamberts P. Hannibal and K. Hondrick Inorg. Chim. Acta 1989 156 119. 169 F. Nief and F. Mathey J. Chem. Soc. Chem. Commun. 1989 800. 170 W. J. Evans and T. A. Ulibarri Polyhedron 1989 8 1007. 171 D. J. Berg S. J. Burns R. A. Andersen and A. Zalkin Organometallics 1989 8 1865. 172 S. P. Nolan D. Stem and T. J. Marks J. Am. Chem. Soc. 1989 111 7844. Sc Y the Lanthanides and the Actinides ~lefins).'~~ This reaction is 103-106 times faster than typical d-block atom abstrac- tion reactions.YbCpf R is formed from radical trapping of R by the Yb" compound. This reacts further with YbCp;X in what are described as 'Yb'*'-Gringard' reactions. Mechanistic studies indicate the dominance of inner-sphere mechanisms in these reactions. Addition of C6F6 among other unsaturated fluorocarbons to YbCp? gives the mixed oxidation state complex Yb,(p-F)Cpt which has an asymmetric Yb"-F-Yb"' bond with Yb-F distances of 2.317(2) and 2.084(2) The two YbCpf moieties are mutually staggered about the Yb-F-Yb axis. The reactions of Sm" complexes with nitrogen containing organic substrates have also been investigated. SmCpft.h.f. reacts with pyridazine to give (~~CP*~.~.~.),[~,~]~-(CH=NNCH=CHCH-),], (12) in which a bridging bipyridazine moiety has formed through coupling at the 4-po~ition.l~~ Benzaldehyde azine PhHC=N-N=CH=Ph is also reductively coupled to give (SmCp,*),[p3 ,T~-(PhHC=N-N-CHPh-),I.Bipyridine reacts with SmCpft.h.f. to give the Sm"' complex SmCpf(r]2-N2CloH8). These compounds were all charac- terized by X-ray structural studies. Dimerization of the phosphaethyne derivative Bu+C=P has also been found in a reaction with SmCpft.h.f.2.176 This afforded (Cp,*Sm),(p-Bu'C=P-P=CBu') (13) in which the phosphaethyne moiety has dimerized and is bound to Sm via both the phosphorus and carbon atoms of the resulting diphosphabutadienyl moiety. Bu' -A phosphine oxide complex of Ybz+ has been prepared in the reaction between YbCp,(MeOCH,CH,OMe) and Ph3P0 which affords YbCp,(OPPh,) .177 The X-ray crystal structure of this compound reveals a pseudo-tetrahedral arrangement of the Cp and OPPh3 ligand groups about the Yb2+ion.The Yb-0 distances are unusually short at 2.30(2) and 2.33(2) A. Use of a diphenylphosphine substituted cyclo- pentadienide ligand has led to the synthesis of the heterobimetallic complex Yb(t.h.f.)2(C5H4PPh2)zPtMe2.t.h.f.178 The X-ray crystal structure reveals a pseudo tetrahedral environment about the Ybz+ ion comprising two oxygen atoms from the t.h.f. ligands and two r]5-C5H4PPh ligands. The -PPh2 moieties in turn bind to the PtMe moiety to give a near square planar environment around the Pt. Several compounds incorporating cyclo-octatetraenide ligands have been repor- ted. The sterically bulky ligand 1,4-( Me3Si),C,H;- reacts with YCl,(t.h.f.) to give 173 R.G. Finke S. R. Keenan and P. L. Watson Organometallics 1989 8 263. I74 C. J. Burns and R. A. Andersen J. Chem. SOC.,Chem. Commun. 1989 136. I75 W. J. Evans and D. K. Drummond J. Am. Chem. SOC.,1989 111 3329. 176 A. Recknagel D. Stalke H. W. Roesky and F. T. Edelman Angew. Chem. Int. Ed. Engl. 1989 28 445. 177 G. B. Deacon B. M. Gatehouse and P. A. White Polyhedron 1989 8 1983. 178 G.B. Deacon A. Dietrich C. M. Forsyth and H. Schumann Angew. Chem. Inr. Ed. Engl. 1989,28,1370. 108 C.J. Jones Y[ 1,4-(Me3Si),C8H,](CL-Cl),(t.h.f.), .22 The amide complex Li[ Lu( T~-C,H,BU)- (NMeCH2CH,NMe2),] has also been synthesized along with Li{Ln[ N(Me)CH,-CH2NMe2I4} (Ln = Y Ho Lu) and Li[YCp2(NMeCH2CH2NMe2)2].'79 The crystal structure of the holmium compound shows that two chelating NMeCH2CH2NMe2 ligands are bound to Ho3+ along with two monodentate amide ligands which also coordinate to Li (14).The reactions of Ln(C8Hg)Cl(t.h.f.) (Ln = Pr Sm Gd Tb Dy Er and Lu) with NaCp* affords Ln(CgH8)Cp*(t.h.f.),.180 The X-ray structure of the Lu complex reveals a slightly bent sandwich structure with the angle at Lu between the ring centroids being 173".Examples of formally Ln( 0) complexes have been obtained by co-condensation of atoms of the lanthanide elements with 1,3,5-tri-t-butylbenzeneto give the thermally stable bis( 7-arene)lanthanide( 0) sandwich compounds for the lanthanides Nd Tb Dy Ho Er and Lu.181 Thermally unstable complexes are obtained for La Pr and Sm and unisolable materials for Ce Eu Tm and Yb.This pattern was rationalized in terms of a bonding model in which the promotion energy from f"s2 to f"-ld's2 is an important factor. Where this energy is large stable complexes are not formed. The low stability of compounds of the early lanthanides despite their favourable electronic properties is attributed to the inability of the BU\C,H ligand to sterically saturate these larger ions. 4 Actinides This section is divided into two parts the first covers the general and coordination chemistry of the actinides and the second covers organoactinide chemistry. In the first of these parts the early actinides are considered first with compounds involving inorganic ligands and monodentate ligands preceding compounds with polydentate and macrocyclic ligands.The later actinides are included at the end of this part. In general lower oxidation state compounds appear after higher oxidation state compounds. General and Coordination Chemistry.-In a theoretical study iterative relativistic extended Huckel energy parameters are given for the elements Th to Np and the reasons why Tho has a bent structure and UO;' a linear structure are explored.'82 179 H. Schumann P. R. Lee and J. Loebel Chem. Ber. 1989 122 1897. 180 H. Schumann R. D. Kohn F. W. Reier A. Dietrich and J. Pickardt Organometallics 1989 8 1388. 181 D. M. Anderson F. G. N. Cloke P. A. Cox N. Edelstein J. C. Green T. Pang A. A. Sameh and G. Shalimoff J. Chem. Soc. Chem.Commun. 1989 53. 182 P. Pyykko L. J. Laakkonen and K. Tatsumi Inorg. Chem. 1989 28 1801. Sc Y the Lanthanides and the Actinides 109 In the synthetic field a new and convenient synthesis of UOBr3 by reaction of U03 with COBr2 has been described.23 The thermodynamically favourable elimination of CO provides a driving force for the reaction. The thermal decomposition of uranium and thorium carboxylates to form oxides has also been studied.'83 By varying the formulation of the precursor complex it is possible to control the composition of the oxides produced. A series of peroxothorates has been synthe- sized.'84 The compounds obtained include A,[Th(0,)F,(OH)2].nHz0 (A = NH4 n = 3; A = Na or K n = l) [Th2(02)3(C204)(H20)4]-5H20 and [Th,(o& (so& (H20)4].5H20.A route to phosphine oxide and arsine oxide complexes of UO',+ has been described in which U14 is oxidized by Me2S0 in MeC202Et.'85 This reaction affords U0214L2 [L = Ph3As=0 (Me2N)3P=0 (Me2N),C=O] and [Ph,P],[ U0214]. U0212L4 [L = Ph3As=0 (Me,N),P=O] can also be synthesized using this reaction. Some intercalation compounds of the actinides have been reported. These include [Cu( LL),],[ BA]~,-,~U02E04-2H20 (LL = 2,9-dimethyl-l,lO-phenanthrolineor 2,9-dimethyl-4,7-diphenyl-1,1O-phenanthroline; E = P As and x -0.2) in which the [Cu(LL),]+ quenches the uranyl photoluminescence.'86 The Cu' centres in these materials may be oxidized by Br then photochemically re-reduced. Dioxo-actinide(v1) ions can also form intercalates so that UO',+ or NpO;+ ions can be intercalated into HU02P04 or HNp02P04 to give layered hydrated ~olids.'~' In the aqueous reactions of AnO;+ with HAn02P04 (An = either U or Np in both reagents) the hydrated layered solids (AnO,),(PO4) are produced.Cross reactions involving two different actinides lead to substitution of actinide sites in the host lattice in addition to intercalation. The crystal structures of NMe4[U02S04~2H20]C1 and NH4[UO2F(SeO4)].H2O have been determined.'88*'89 Fast atom bombardment mass spectra of U02X2 (X = NO3 or CH3C02) have been obtained and provide evidence for the formation of oligomers (UO,) (n = 1 to 5) and 0 atom adducts (UO,),(O) (rn = 0 to 5) which pose interesting structural problems.'90 E.s.r. and magnetic studies of the Uv chloride derivative UCl,PPh3 indicate that a thermally accessible intramolecular electron transfer equilibrium exists according to equation (3):19' UVCI,PPh + U'"C1,PPh; (3) In solution studies the enthalpies and entropies of complexation of UO',+ and Th4+by aspartic acid have been determined.19' The results are in accord with actinide binding to only one carboxylate moiety in the amino acid.The effect of the substituent on the thermodynamic stability of 1:1 complexes of ten monosubstituted salicyclic acid derivatives with UO;+ has been studied in aqueous media.'93 In a 'H n.m.r. 183 K. M. Dunaeva and V. I. Sinitsyn Russ. J. Inorg. Chem. 1989 34 247. 184 C. B. Bhattacharjee M. K. Chaudhuri and R. N. D. F'urkayastha Znorg. Chim. Actu 1989 160 147.J. G. H. DuPreez and B. Zeelie Znorg. Chim. Actu 1989 161 187. 186 A. T. Jacob and A. B. Ellis Znorg. Chem 1989 28 3846. 187 P. K. Dorhout R. J. Kissane K. D. Abney L. R. Avens P. G. Eller and A. B. Ellis Inorg. Chem. 1989 28 2926. I 88 L. B. Serezhkina and V. K. Trunov Russ. J. Znorg. Chem. 1989 34 543. 189 V. A. Blatov L. B. Serezhkina V. N. Serezhkin and V. K. Trunov Russ. J. Znorg. Chem. 1989 34 91. 190 K. R. Jennings T. J. Kernp and P. A. Read Znorg. Chim. Actu 1989 157 157. 191 C. Miyake M. Hirose and H. Ohya-Nishigucti Znorg. Chim. Actu 1989 165 179. 192 A. Bismondo and L. Rizzo Polyhedron 1989 8 2233. 193 Y. Z. Yousif and F. J. M. A1 Imarah Transition Met. Chem. 1989 14 123. 110 C. J. Jones study of the kinetics of acac (acacH = pentane,2,4-dione) exchange between acacH and Th(acac) in CD3CN a deuterium isotope effect was found.’94 This is consistent with a proton transfer process being the rate determin-ing step.The mechanism of acetylacetonate substitution by P-diketonate in UO,[Me,C(O)CHC(Me)O],[( MeO),P=O] has also been studied.‘95 The syntheses and X-ray crystal structures of [N%][UO,(S,CNR~),] (R = Et R’ = (CH,), (CH,), Me2; R = Me R’ = Et) have been reported and all four complexes exhibit approximately hexagonal bipyramidal structure^.'^^ The equatorial s6 donor atom set is distorted from planarity by puckering to accommo- date the six large sulphur atoms. Interligand S-S distances are in the range 2.911(4)-3.109(4) A. The peroxo complexes [Th(o,)L] (L = C6H4(NH2)2-1,2; CSH4N(NH2)-2) [Th(02)C6H4(C02)2*20PPh,l,[Th(02)Li] (L’H = NH2CH2-CH20H and C6H4NH20H) [UO(O,),L] [UO(02)Lk] and [U0(O),LH20] (L”H2= HOCH2CH,CH20H and CH2(C02H),) have been prepared and found to oxidize PPh3 or AsPh3 to their corresponding 0~ides.l~’ In other work with bi- dentate ligands the complexes UO,L:(HL) (HL”’ = Ph,P(O)CH,C(O)Ph) and U02(U04),( HL’”),.2H20 were prepared.’98 The crystal structure of U02( NO3),( HL”’),! shows a distorted hexagonal bipyramidal coordination geometry about uranium with bidentate nitrate and HL”’ ligands bound uiu the phosphoryl oxygen.The bifunctional ligands (Pr’O),P( =O)CH,S( =O),R (R = C6Hll or C6H4Me-4 and n = 2; R = C6H,Me-4 and n = 1)and Ph2P( =O)CH,S( =0),NMe2 have also been prepared and their complexation reactions with U02( N03)2 investi- gated.’30 U02(NO,),{( Pr’0)2P(0)CH2S(0)2C6H contains a UO’,+ moiety equatorially coordinated to two bidentate nitrate ions and a phosphoryl oxygen from each of the two bifunctional ligands which bind in a monodentate manner.A series of Th4+ and UOz+ complexes containing Schiff base ligands has been de~cribed.’~~ The complexes are formulated as ThL2(N03)4 (L = N-(pyridine-2-carboxaldehyde)isonicotinylhydrazone,N-(pyridine-2-carboxalde-hyde)benzhydrazone (pcbh) N-(pyridine-2-carboxaldehyde)salicyoylhydrazone (pcsh) 3 N-(pyridine-2-carboxy1dine)aminophenol (pcap) and 4N-pyridine-2-carboxy1idene)aminoantipyrine U02L2( N03)2 (L = pcbh and pcsh) and U02-(pcap)(NO,) . The uranyl complexes U02(L)A [LH = S-methyl-1,Cbis-(salicylidene)isothiosemicarbazide,A = MeOH EtOH or Me,NCHO] have also been synthesized and the nature of the complex with A .= Me2NCH0 determined by an X-ray crystallographic study.200 An oxygen from the ligand A occupies an equatorial site in an approximately pentagonal bipyramidal coordination arrange- ment in which the four donor atoms of L also occupy equatorial sites about the trans-dioxo-uranium(v1) centre.In studies of compounds containing macrocyclic or cyclic polyether ligands the presence of benzo-groups or carboxylic acid substituents on crown ethers or of 194 N. Fujiwara T. NaKagawa H. Tomiyasu and H. Fukutomi Bull. Chern. SOC.Jpn. 1989 62 2087. 195 Y. Udagawa H. Tomiyasu W. S. Jung,T. Y. Eom and H. Fukutomi Bull.Chern. Soc. Jpn. 1989,62,2802. 196 N. W. Alcock and M. Pennington J. Chern. SOC.,Dalton Trans. 1989 471. 197 M. T. H. Tarafder M. B. H. Howlander B. Nath R. Khan and A. A. M. A. Islam Polyhedron 1989 8 977. 198 R. Babecki A. W. G. Platt J. C. Tebby J. Fawcett D. R. Russell and R. Little Polyhedron 1989,8 1357. 199 B. Kuncheria G. S. Devi and P. Indrasenan Znorg. Chirn. Acta 1989 155 255. 2oo V. M. Leovac E. Z. Iveges N. Galesic and D. Horvatic Znorg. Chirn. Acta 1989 162 277. Sc Y the Lanthanides and the Actinides alkyl substituents on diaza-crown ethers has been found to have only a small effect on the complexation of UOz+.201 The uranium crown ether complexes U02C12- (OH2)2L.L (L = 1,4,7,10-tetraoxacyclododecane)and U02C1,(OH2)(3,6,9,12,15-pentaoxaheptadecane- 1,17-diol) have been synthesized and their molecular struc- tures determined.202 The former complex contains two crown ether ligands only one of which is bound directly to the UO$+ ion by one of its oxygen atoms.The second crown ether molecule is hydrogen bonded to a coordinated water molecule as shown in Figure 17. In the latter complex the polyether is bound to the UO’,+ centre by one of the diol hydroxy groups. Again a coordinated water molecule is hydrogen bonded to internal ether oxygens in the diol. Both compounds contain an approximately pentagonal bipyramidal uranium centre with the equatorial donor atom set bound to the UO;’ core comprising two chlorides two water molecules and one oxygen from the polyether.C(9) A Figure 17 The structure of U0,C12(OH,),( 12-crown-4). 12-crown-4 (Reproduced by permission from J. Chem. SOC.,Chem. Commun. 1989 1586) Turning to the actinide elements in lower oxidation states thermal lensing spec- trometry has been applied to an investigation of the hydrolysis of U1+.’03 At 25 “C with 0 6 -log[H+] d 2.8 in 3 mole dm-3 (Na,H)ClO the data could be described by the following model U4+ + H,O U(OH)3++ H+ log*pl = -1.65(*0.05) (4) U4+ + 2H2O U(OH):+ + 2H+ lOg*p = <-4.5 (5) The UIV alkoxide complex UCl,(0CB~:)~(t.h.f.) has been prepared and may be used as a precursor to the compounds U(OCBu:),X [X = BH4 MeC(0)- CHC( Me)O v3-C3Hs CH2Ph].204 In addition the first structurally characterized neutral homoleptic aryl-oxo complex of UrVhas been de~cribed.~” An X-ray crystal structure reveals that U(O-2,6-Bu&H3) has a near tetrahedral U04 core with 201 J.Lagrange J. P. Metabanzoulou P. Fux and P. Lagrange Polyhedron 1989 8 2251. 202 R. D. Rogers M. M. Benning R. D. Etzenhouser and A. N. Rollins J. Chem. Soc. Chem. Commun. 1989 1586. 203 I. Grenthe G. Bidoglio and M. Omenetto Znorg. Chem. 1989 28 71. 204 C. Boudin and M. Ephritikhine J. Organomet. Chem. 1989,364 C1. 205 W. G. Von der Sluys A. P. Sattelberger W. E. Streib and J. C. Huffman Polyhedron 1989 8 1247. 112 C. J. Jones U-0 = 2.135(4)A and 0-U-0 angles of 110.2(1) and 108.0(2)". The U-0-C( ipso)angle is 154.0(6).6 In studies involving bidentate ligands it has been found that the extraction of La"' Ce"' Eu"' ThIV,and UIV from aqueous media into 4-methyl-2-pentanone containing 3-phenyl-4-acetyl-5-isoxazalone is greater than for related systems con- or taining l-phenyl-3-methyl-4-benzoyl-5-pyrazolone thenoyltrifluoroacetone as additives.206 Other UIV complexes which have been reported include UC14( 0-C6H4CH=NC6H4X-p) (n = 2,X = CI Br OH and Me; n = 3 X = One report of a complex of UIV with a macrocyclic ligand has appeared.Electrochemical and spectroelectrochemical studies of An(0EP) (acac) (An = U Th; OEPH = octaethylporphyrin; acacH = pentane-2,4-dione) reveal a reversible ring centred reduction process for both compounds.20g However whilst the Th complex also exhibits a first oxidation process associated with the porphyrin ring the U complex appears to undergo oxidation at the metal centre.There are two reports describing U"' compounds. Lewis base adducts of U13 have been found to offer a useful synthetic route to U"' complexes.209 The reaction of U turnings with I in t.h.f. affords UI,(t.h.f.) which has a pentagonal bipyramidal structure with one equatorial and two axial iodide ligands. This material reacts readily with anionic ligands X- to give UX,(t.h.f.) (X = N(SiMe,) or 2,4- dimethylpentadienyl and n = 0; X = CSHs or OC6H3Me,-2,6 and n = 1). In another study 'H n.m.r. measurements have shown that U(OC6H3Bu\-2,6) binds CNBu' to form U(OC6H3Bu\-2,6),(CNBu') which exchanges CNBu' with free ligand in solution via the intermediate U(OC6H3Bu\)3(CNBu') which may be detected at low Among papers describing the chemistry of the later actinides a report of the oxidation of Pd''to hIV by XeF and by SO,F-in 1 mol.dm- HC104 solutions has appeared.211 In both cases two molecules of Pu'I' are consumed per molecule of oxidant and mechanisms are proposed which involve a sequence of two one- electron steps since no evidence was found for the formation of pUv or hv1. The enthalpies of formation of 1 :1 complexes of Am'" with acetate and a series of aminocarboxylate ligands have been determined.,' The values obtained provide no evidence of significant differences in the bonding of Am"' Eu"' and Cm"' to the ligands studied. The solvent extraction of M3+ (M = Am Cm La Eu Lu) by thenoyltrifluoroacetone (Htta) in xylene has also been studied and evidence obtained for the extraction of M(OH)(tta) at higher pH values.213 Also of relevance to solvent extraction processes is a study of the protonation constants and stability constants with lanthanide ions of diethylene triamine-N,N,N',N"-tetraacetic acid-"'-propionic This ligand could provide a basis for separating Am3+ from lanthanides.206 A. Jyothi and G. N. Rao Polyhedron 1989,8 1111. 207 W. I. Azeez and A. I. Abdulla Transition Met. Chem. 1989 14 425. 208 K. M. Kadish Y. H. Liu J. E. Anderson A. Dormond M. Belkalem and R. Guilard Inorg. Chim. Acta 1989 163 201. 209 D. L. Clark A. P. Sattelberger S. G. Bott and R. N. Vrtis Inorg. Chem. 1989 28 1771. 210 W. G. Van der Sluys and A. P. Sattelberger Inorg. Chem. 1989 28 2496.211 R. L. Cook M. Woods J. C. Sullivan and E. H. Appelman Inorg. Chem. 1989 28 3349. 212 E. N. Rizkalla J. C. Sullivan and G. R. Chopin Inorg. Chem. 1989 28 909. 213 P. K. Mohapatra and P. K. Khopkar Polyhedron 1989 8 2071. 214 D. J. Sawyer and J. E. Powell Polyhedron 1989 8 1425. Sc Y the Lanthanides and the Actinides 113 0rganoactinides.-Some theoretical work on organolanthanides has appeared. Iter- ative relativistic extended Huckel energy parameters which give realistic metal orbital populations for organo-actinides are given for the elements Th to Np and energy levels are calculated for An(C8H,)z.'82 Quasi-relativistic Xa-Sw calculations on AnCp (An = U Th) which unlike AnCp,L (L = neutral two-electron ligand) in which all of the An d-orbitals are used as acceptors have a low lying dz2 orbital which competes with the 5f orbitals for metal electron^.'^^ Results for AnCp (An = Pa Np Pu)are also presented.Thermodynamic studies have examined the correlation between the standard enthalpies of formation for complexes of the type AnCpTL2 (An = Th'" or U'"; L = hydrocarbyl or OBu') and the enthalpies of formation of LH or LHn.'16 Also the effectiveness of U and Th complexes as catalysts for decoupling phenyl silane has been ~tudied.~'' ThCpr Me2 selectively catalyses the dimerization of phenyl silane in diethyl ether but the reaction with UCp:Mez is less selective and may involve U"' intermediates. Among the synthetic work reported a number of papers describe complexes involving Cp or related ligands.Treatment of triindenylthorium chloride with potassium metal in benzene affords tetraindenylthorium( IV)."~ No Th"' compounds were detected in this reaction. The reaction between U(BH,),.nt.h.f. and c~,*Th(pPh~)~ affords [Na(t.h.f.),][cp*(BH,),1 which contains chains of indepen- dent Cp*U(BH4) moieties.219 The three boron atoms and the Cp* ligand define an approximately tetrahedral coordination geometry about the U atom. The stoichiometry of the compound and black colour of the crystals suggest a mixed oxidation state species with an average U oxidation state of 3.5. In reactions involving monodentate hydrocarbyl ligands U(O-2,6-Bu:C6H,) reacts with LiCH(SiMe3)2 to give the royal blue complex U[CH(SiMe3)2]3.220 The X-ray structure of this com- pound reveals a pyramidal structure involving a y-agostic interaction with the silyl methyl groups.The reaction with CNBU' affords U(O-~,~-BU:C,H,)~(CNBU') which exchanges CNBu' with free ligand in solution via the intermediate U(OC6H3Bu~)3(CNBu')2 which may be detected at low temperature.'" The formation of a U-Si bond was achieved in the reaction between UCp,CI and LiSiPh which gave UCP,S~P~,.~~~ This compound in turn reacts with 2,6- Me2C6H3NC to give an insertion product UCp,[ C( NC,H3Me2-2,6)SiPh3] which contains an q2-isocyanide ligand. The reaction between UCp3[C( NC6H3Me2- 2,6)SiPh3] and HOSiPh affords UCp3(OSiPh3) which contains a near linear U-0-Si bond angle of 172.6(6)' and a short U-0 distance of 2.135(8) A. With OSiPh the three Cp ligands complete a distorted tetrahedral arrangement about the U atom.The chelating phosphorus ylide complexes AnCpgC1[CH2(CH2)PRR'] (An = U Th; R = R' = Me Ph; R = Me R' = Ph) have been prepared.222 'H 215 B. E. Burslen L. F. Rhodes and R. J. Strittmatter J. Am. Chem. Soc. 1989 111 2756. 216 A. R. Dias J. A. Martino Simiies C. Teixeira A. Airoldi and A. P. Chagas J. Organomet. Chem. 1989 361 319. 217 C. Aitken J. P. Barry F. Gauvin J. F. Harrod,A. Malek and D. Rousseau Organomeiallics 1989,8,1732. J. Goffart and S. Bettonville J. Organomet. Chem. 1989 361 17. R. R. Ryan K. V. Salazar N. M. Saver and J. M. Ritchey Inorg. Chim. Acta 1989 162 221. W. G. Van der Sluys C. J. Bums and A. P. Sattelberger Organornetallics 1989 8 855.M. Porchia N. Bnanese U. Cosellato F. Ossola G. Rossetto P. Zaneila and R. Graziani J. Chem. 218 219 220 221 SOC.,Dalton Trans. i989 677. 222 R. E. Cramer S. Roth F. Edelmann M. A. Bruck,K. C. Cohn and J. W. Gilje Organornetallics 1989 8 1192. 114 C.J. Jones n.m.r. studies of the Th'" compounds reveal dynamic behaviour for the ylide ligand involving Th-C bond breaking rotation and recombination processes. The X-ray structures of. UCp;Cl[CH,(CH,)PPhR] (R = Me; Ph) reveal an average U-C(y1ide) distance of 2.60 A as shown in Figure 18. The phosphinimine complex UCp?C12(HNPPh3) is formed in the reaction between UCpTCl and HNPPh3 .223 The X-ray structure of the molecule shows an agostic interaction between the uranium and the imino hydrogen and a U-N distance of 2.43A as shown in Figure 19.Figure 18 The Structure of UCpqCl[CH2(CH2)PPh2] (Reproduced by permission from Organometallics 1989 8 1192) Figure 19 The structure of UCpfC12(HNPPh,) (Reproduced by permission from OrganometaNics 1989 8 2327) R. E. Cramer S. Roth and J. W. Gilje Organometallics 1989 8 2327. Sc Y the Lanthanides and the Actinides Two reports describe complexes which contain a cyclo-octatetraenyl ligand or a derivative thereof. Th(C8H8)C12*n (t.h.f.)reacts with MgCp"C1t.h.f. to give Th(C9H8)Cp*Cl(t.h.f.),. Reaction of this compound with Bu'CH2MgC1 affords T~(C~H~)C~*(CL-C~)~M~~H~BU~ (t.h.f.) which desolvates at 100 "c to give [Th(C8H8)Cp*C1]2.224 This material in turn reacts with LiCH(SiMe3)2 to give Th(C8H8)Cp"[CH(SiMe3)2]7 the X-ray structure of which reveals the presence of V8-C8H8 and q5-C5Me5 ligands.The sterically bulky cyclo-octatetraenyl ligand 1,4-(Me3Si),C8H;- has been used to synthesize An[1,4-(Me3Si)&H& (An = Th U) from AnC14.22 The reaction of 1,4-(Me$i)2C&;- with UC12(BH4)2 affords U[ 174( Me3Si)2C8H,]( K~-BH,)~. T. M. Gilbert R. R. Ryan and A. P. Sattelberger Organometallics 1989 8 857.