5 Nitrogen, phosphorus, arsenic, antimony and bismuth K. K. Hiia and T. P. Keeb aDepartment of Chemistry, King’s College London, The Strand, London, UK WC2R 2LS bSchool of Chemistry, University of Leeds, UK LS2 9JT 1 Introduction This report covers important aspects in the development of Group 15 chemistry during the year 1998.1 Since a comprehensive review is unfortunately beyond the remit of this particular article, attention has been focused on the twin areas of metalloorganic and co-ordination chemistry.Within the vast areas of nitrogen and phosphorus chemistry, only synthetic work on novel ligand systems, especially asymmetric systems, has been described with concomitant emphasis on applications in asymmetric catalysis. 2 Nitrogen The co-ordination and organometallic chemistry of tris(2-pyridyl) tripod ligands which use nitrogen, phosphorus, arsenic or carbon as the central bridging atoms, including polypyrazolylborate ligands, has been reviewed.2 Chloro– and methyl–aluminium complexes with the tridentate nitrogen ligand (RNHCH 2 CH 2 ) 2 NR@ (R\R@\SiMe 3 ; R\SiMe 3 , R@\Me; R\Pr*, R@\Me) have been reported.Single-crystal X-ray di§raction studies revealed that the tridentate nitrogen donor atoms enforce an approximately trigonal-monopyramidal co-ordination geometry for neutral and cationic four-co-ordinate aluminium complexes.The cationic aluminium derivatives and the neutral aluminium chloride brought about the ring-opening oligomerization of propylene oxide, giving low molecular weight polymers consisting exclusively of head-to-tail linkages.Methyl– and hydrido–aluminium as well as aluminium alkoxide, initiated the polymerization of (D,L)-lactide in benzene at 80 °C to give high molecular weight polymers.3 The interaction of MnII, FeII and CoII with the ligand taci 1 has been studied in the solid state and in aqueous solution.4 Magnetic susceptibility measurements revealed a high-spin electron configuration for the Mn and the Fe complexes.All three structures exhibited distorted octahedral MN 6 co-ordination. The stability constants for the complexes [M(taci)]2` (M\Mn, Fe, Co) and [M(taci) 2 ]2` (M\Fe, Co) in aqueous media have been evaluated by potentiometric titration. Comparison with other Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 57divalent cations showed that the order of stability increases MnII\CoII[FeII\ZnII\CoII\CuII\NiII.A new isomeric form of a bis-taci cobalt(III) complex was formed, where one of the taci ligands co-ordinates the metal cation by one nitrogen and two oxygen atoms. The hexamethylideneimino (hmi) derivative [Co(taci) 2 (hmi)]3` reacts with nitromethane and base and results in the formation of [Co(hebdoc)]`, where the two fragments are fused by two anionicN––CH–C(––NO 2 ~)–CH 2 –NHbridges.5 Two major diastereoisomers were formed from fifteen possibilities which possessed di§erent con- figurations at co-ordinated methylamino groups and were incorporated in a disordered manner in the crystal structure of [Co(hebdoc)] 2 Cl 2 ·3.5H 2 O.In the base-catalyzed reaction of [Co(tmca) 2 ]3` with an appropriate mixture of formaldehyde and acetaldehyde, the condensation process was followed by a coupling reaction.After reduction with NaBH 4 and air oxidation, a cobalt(III) complex with the novel hexadentate ligand N-(q@-amino-8@,10@,11@-trimethoxy-2@,6@-diazabicyclo[5.3.1]undec-4@-ylmethyl)-2,4,6- trimethoxycyclohexane-1,3,5-triamine was formed as the major product.Direct treatment of [Co(taci) 2 (hmi)]3` and [Co(tmca) 2 (hmi)]3` with NaBH 4 resulted in the liberation of the new triamines 1,3,5-trideoxy-1,3,5-tris(methylamino)-cis-inositol and all-cis-2,4,6–trimethoxytris(N-methyl)cyclohexane-1,3,5-triamine. A phenol-based ‘end-o§’ compartmental ligand, 2-[N,N-di(2- pyridylmethyl)aminomethyl]-6-MN-[2-(dimethylamino)ethyl]iminomethylN-4-methylphenol 2 (HL), forms dinuclear nickel complexes [Ni 2 (L)(AcO)(NCS) 2 ], [Ni 2 (L)(AcO) 2 (MeOH)]PF 6 , and [MNi 2 (L)(OH)(MeOH)N2 (CO 3 )](PF 6 ) 2 .The complexes react with urea in ethanol to form the isocyanate complexes [Ni 2 (L)(AcO)(NCS)(NCO)], [Ni 2 (L)(AcO)(NCO)(EtOH)]PF 6 and [MNi 2 (L)- (NCO)(EtOH)N2 (CO 3 )](PF 6 ) 2 , respectively.6 The co-ordination chemistry of the bis(benzimidazolyl) ligands 3 [X\S, O, S(CH 2 ) 3 S, S(CH 2 ) 2 S; R1, R2, R3\H, Me) has been studied for a series of soft-toborderline metal ions such as zinc, mercury, cadmium and silver.7 The ligand bis(2-benzimidazolyl)propane 4 co-ordinates to NiII with chloride as an anion forming a dinuclear compound with the formula [NiCl 2 (tbz) 2 ] 2 ·2EtOH.8 Each NiII ion has a distorted trigonal bipyramidal environment consisting of two asymmetrically bridging chloride anions, two nitrogen atoms of the ligand and a Ni–Ni bond.Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 58This compound appears to be the second example of a five-co-ordinated ferromagnetic dinuclear nickel(II) compound of this type, and its magnetic properties appear to correlate with the ligand structure.Octaethylformylbiliverdin (H 2 OEFB) 5 was found to form low-spin complexes with CuII, NiII and CoII. Both CuII(OEFB) and CoII(OEFB) can be converted to the heme analogues, [CuII(OEOP)]` and [CoII(OEOP)]`, where OEOP is the anion of octaethyl- 5-oxaporphyrin.9 The geometric and electronic structural properties of these complexes of formylbiliverdin were compared to those of analogous compounds of biliverdin and of porphyrins.The (aminoferrocenyl)phosphine 1-diphenylphosphino-2,1@-(1-dimethylaminopropanediyl) ferrocene, 6, was used to synthesize new palladium complexes [Pd(L)(DMFU)] and [Pd(L)(MA)] and the allyl complex [Pd(g3-2-MeC 3 H 4 )(L)] [OTf]. All these compounds exist in solution as mixtures of two diastereoisomers, with either the alkene or the allyl group di§erently oriented with respect to the aminophosphine ligand.Other palladium(II) derivatives of formulae [PdRR@(L)] (R\Cl, R@\Me; R\R@\Me; R\R@\C 6 F 5 ) were also prepared. Pd–N bond rupture in the new complexes was analyzed along with the influence of ferrocenyl aminophosphine and ancillary ligands. The oxidation state of the palladium centre on this process was discussed.10 A simple synthesis has been devised for the tripodal 3,3,4-tetraamine ligand NM(CH 2 ) 3 NH 2N2M(CH 2 ) 4 NH 2N (L).This ligand forms a copper(II) complex, [Cu(HL)Cl 2 ]ClO 4 , the structure of which has been determined by X-ray di§raction. The cation contains a five-co-ordinate copper atom, bonded to two chloride ions, the two propylamine groups and the tertiary nitrogen atom of the ligand adopt a distorted trigonal bipyramidal arrangement in which the two primary amine groups occupy the axial positions.The butylamine group of the ligand does not co-ordinate to copper but is protonated.11 Reaction of the bidentate compound 2-(2-aminophenyl)pyridine with p-toluenesulfonyl chloride a§orded the new bidentate compound HL which contains potentially chelating pyridyl and (protonated) sulfonamide N-donor binding sites.The crystal structure of the latter molecule shows that the sulfonamideNHproton is involved in a hydrogen-bonding interaction with the pyridyl nitrogen atom, resulting in a near co-planar arrangement of the pyridyl and phenyl rings. Reaction of HL with various metal(II) acetates (M\Cu, Co, Pd) a§ords the neutral complexes [ML 2 ] in which the sulfonamide is deprotonated.All of these have been crystallographically characterised; the copper(II) and palladium(II) complexes are planar, whereas the cobalt(II) complex is Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 59pseudo-tetrahedral with the two CoN 2 planes at 85° to one another. Appropriate spectroscopic and electrochemical studies on the complexes were described.12 Reaction of (C 5 H 4 Me) 3 Ln and HTz in THF a§ords the complexes [(C 5 H 4 Me) 2 LnTz] 2 (Ln\Yb, Er).13 An organopalladium complex containing orthometallated (S)-[1- (dimethylamino)ethyl)]naphthalene as a chiral auxiliary has been used successfully to promote the asymmetric [4]2] Diels–Alder reaction between 3,4-dimethyl-1- phenylphosphole and 2-vinylpyridine.14 The pyridyl group in the resulting phosphanorbornene cycloadducts can be located stereospecifically in the exo or endo position by controlling the electronic properties of the organopalladium promoter.In the exo-cycloaddition process, the P–N bidentate ligand ([)-2-M[1-a,2-a-(S),4-a,7(S)]- 5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-en-2-ylNpyridine 7 was produced stereoselectively. However, in the endo-cycloaddition process, a pair of separable diastereomeric palladium template complexes containing the naphthylamine auxiliary and the enantiomeric forms of 2-M[1-a,2-b(R/S),4-a,7(R/S)]-5,6-dimethyl-7- phenyl-7-phosphabicyclo[2.2.1]hept-5-en-2-ylNpyridine 8 were obtained.In these diastereoisomeric complexes, the endo-cycloadducts co-ordinated to palladium as monodentate ligands via only their phosphorus donor atoms.The pyridyl-nitrogen atoms are not involved in metal complexation. The absolute configurations and the co-ordination properties of the exo- and endo-pyridylphosphines have been established by single-crystal X-ray analyses. 3 Phosphorus Abrief review article on the synthetic and structural aspects of dialkyldithiophosphate, alkylenedithiophosphate and dialkyldithiophosphinate derivatives of arsenic, antimony and bismuth and their organometallic moieties has been published.15 Organophosphorus boranes R 3 P·BH 3 (R\Ph, Me, OMe, o-anisyl) react with amine pentacarbonyltungsten complexes under mild conditions to a§ord the corresponding W(CO) 5 (PR 3 ) derivatives in 63–92% yields.The use of piperazine as a diamine tungsten substituent permits a tandem reaction which removes the borane group and leads to the formation of the corresponding organophosphorus tungsten complex. The stereochemistry of pentacarbonyltungsten complex formation from tertiary chiral organophosphorus borane compounds has been shown to proceed with high stereoselectivity and retention of configuration at the chiral phosphorus centre.16 Reaction of the amino acid derivate (S)-N-tolylsulfonylvaline with PhPCl 2 and NEt 3 gives, in [90% yield, a novel chiral phosphorus heterocycle 9 as a [7: 1 mixture of diastereoisomers.The X-ray crystal structure of the major isomer shows that the isopropyl and phenyl groups are mutually cis.The IR spectrum of the W(CO) 5 Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 60adduct of this isomer shows that the N-sulfonyl and carboxylate moieties make it a strongly electron-withdrawing ligand.17 Optical resolution of the asymmetric chelating agent (^)-Ph 2 PCH 2 S(O)Me has been achieved via fractional crystallization of a pair of diastereomeric palladium(II) cationic complexes containing the sulfinyl-substituted ligand and orthometallated (S)-[1-(dimethylamino)ethyl]naphthalene. Optically pure (R)-(])-Ph 2 PCH 2 S(O)Me was displaced from the resolving palladium complex with 1,2-bis(diphenylphosphino) ethane.18 Chelating phosphorus ligands 4,6-bis(diphenylphosphanyl)-2,8-dimethylphenoxathiine 10 (Thixantphos) and 11 with a rigid backbone and a large natural bite angle have been used in the in the nickel-catalysed hydrocyanation of styrene. The para-substituents in the diphenylphosphanyl moiety of the Thixantphos ligands were varied and their electronic e§ects on the activity and selectivity of the catalytic experiments were investigated.19 Recent progress in copper-catalyzed enantioselective Michael additions using new phosphorus ligands have been described.20 A novel enantiomerically pure 2-[2(diphenylphosphino)phenyl]-4,5-(2-deoxy-a-Dglucopyrano) oxazoline ligand 12 has been prepared from glucosamine. The stereodifferentiating potential of the ligand was demonstrated in palladium-catalyzed intermolecular allylic substitutions of symmetrical and asymmetrical substituted allyl acetates which give products in high yields and high enantioselectivity (up to 98% ee).21 A series of novel N,N-disubstituted aminophosphines 13 have been prepared.The new P,N-binaphthyls were utilized as chiral ligands in palladium-catalyzed allylic substitution and enantioselectivities of up to 71–73% ee were achieved at room temperature.22 The sterically demanding binaphthyl backbone has continued to be exploited to make new chiral ligands which have been applied to the copper-catalyzed asymmetric conjugate addition of diethylzinc to cyclic enones with high enantioselectivity.23,24 Cationic allyl palladium complexes of the diasteriomerically pure chiral-at-phos- Annu. Rep.Prog. Chem., Sect. A, 1999, 95, 57–66 61phorus ligand tert-butyl(menthyl-O)phenylphosphinite have been prepared and characterized by X-ray crystallography. Asymmetric co-dimerization of styrene and ethylene was successfully applied.High enantioselectivities of up to 86% ee have been obtained at room temperature. The co-dimer 3-phenylbut-1-ene was formed in high selectivity (up to 96%) with only small amounts of the isomerization products (E)- and Z)-2-phenylbut-2-ene.By addition of various co-ordinating solvents, the catalyst system was e¶ciently stabilized. Variation of the complex counter anion had a significant e§ect on enantioselectivity.23 4 Arsenic and antimony The synthesis of various diorganodithiophosphate (and dialkyldithiophosphinate) derivatives with arsenic, antimony and bismuth and their corresponding organometallic moieties and mixed derivatives as well as their properties and reactions have been described.24 The syntheses of mixed bis(dialkyl dithiocarbamate) dialkyl dithiophosphate complexes of antimony(III) of the type (XCS 2 ) 2 SbS 2 P(OR) 2 (X\NMe 2 , NEt 2 , N(CH 2 ) 4 ; R\Pr/, Pr*, Bu/ and Bu*) have also been described.25 Synthetic routes to arsenic(III) dithiolate [PhAs(HlipS 2 )] and related compounds have been reported.The reactions indicate pathways by which mono- and diorganoarsenic compounds of various arsenic oxidation states (I, III and V) may inhibit enzymes that contain lipoic acid as a co-factor.26 The synthesis and structure of a cyclic polyarsenic ring ligand [MoAs 8 ]2~, which is the first example of a free binary transition metal pnictide ion, have been reported. A preliminary study of its gas phase co-ordination chemistry with alkali metal ions was carried out through negative ion electrospray mass spectroscopy.27 The reaction of Group 15 trichlorides of ECl 3 with the anion [Mo 2 Cp 2 (CO) 4 (l- PH 2 )]~ resulted in the isolation of a complex featuring a hetero l,g2-PE ligand (E\As, Sb).28 Antimony has been found to co-ordinate as a symmetrically bridged ligand in a novel neutral complex [LW–Sb–WL] [L\N(CH 2 CH 2 NCH 2 CMe 3 ) 3 ] 14.29 Reaction of equimolar amounts of the metalloarsaalkene [(g5- C 5 Me 5 )(CO) 2 FeAs––C(NMe 2 ) 2 ] with the carbonyl complexes [Ni(CO) 4 ], [Fe 2 (CO) 9 ] and [M(Z)-C 8 H 14NCr(CO) 5 ] (C 8 H 14 \cyclooctene), respectively, a§ords the adducts [(g5-C 5 Me 5 )(CO) 2 FeAsMM(CO)nN–C(NMe 2 ) 2 ] M[M(CO)n]\[Ni(CO) 3 ], [Fe(CO) 4 ] or [Cr(CO) 5 ]N.These feature g1 co-ordination of the arsaalkene ligand via the arsenic atom.30 (1,2,3,4-Tetraisopropylcyclopenta-2,4-dien-1-yl) arsenic(III) dihalides, TipCpAsX 2 Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 62(X\Br, I), have been prepared by direct metathesis reaction between the corresponding arsenic(III) trihalides with 1 equivalent of TipCpK at low temperature in good yields.The crystal structures were determined by X-ray di§raction methods and the AsX 2 -moiety in both complexes found to occupy an allylic position neighbouring to an isopropyl substituent. The arsenic fragment is r-bound to the cyclopentadienyl ligand, indicating remarkable p interactions with the diene part of the cyclopentadienyl ring.31 The new cyclopentadienylarsanes (CpRAsR 2 ) (CpR\C 5 Me 5 ; R\H, Et, Pr*, Bu5; CpR\C 5 H 2 Me 3 -1,2,4; R\Cl, Et, Pr*) were synthesized via metathesis reactions in satisfactory to good yields.Pyrolysis studies on the cyclopentadienyldialkyls show their potential suitability as precursors in MOCVD processes.32 The photolysis reactions of cyclo-methylarsathiane, cyclo-(MeAsS)n (n\3 or 4) with Group 6 metal carbonyls M(CO) 6 (M\Cr, W) in THF give the complexes [Cr(CO) 5Mg1-cyclo-(MeAsS) 4N], [Cr(CO) 3Mg3-cyclo-(MeAsS) 5N] and [W(CO) 3Mg3- cyclo-(MeAsS) 6N] in which the As–S ring system expands to give metal-stabilized rings of eight, ten and twelve alternating arsenic and sulfur atoms.33 A preference for arsenic over sulfur is shown in all three complexes.Bonding to sulfur occurs only when octahedral symmetry is best accomodated at the metal atom. The main-group ring structures expand as required to fulfil the more demanding electronic and geometrical requirements of the metallic group. The reaction of cyclo-(MeAsO)n (n\2–5) with MCl 3 ·xH 2 Oin acetonitrile at 100 °C a§ords [MCl 2Mcyclo-(MeAsO) 8N] (M\Ru, Os) in which cyclooctamers (MeAsO) 8 are stabilised in a j4As1,As3,As5,As7 As 4 binding mode in the equatorial co-ordination sphere of the Group 8 metals.Octa- or deca-nuclear cagelike platinum complexes [Pt 2Mcyclo-[As(Me)OAsMNC(O)MeNO 2 ] 2N] and [Pt 2M[MMeC(O)NN2 As 5 Me 5 O 4 ] 2N] were also prepared. k5-AsIII atoms in these complexes participate in square-planar PtII co-ordination and themselves exhibit distorted trigonal bipyramidal co-ordination geometries.34 The reaction of Group 15 trichlorides of type ECl 3 with the anion [Mo 2 Cp 2 (CO) 4 (l-PH 2 )]~ has a§orded the first complex featuring a hetero l,g2-PE ligand (E\As, Sb).35 Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 63The heterobimetallic antimony(III)–alkali metal complexes [MSb 2 (NC 6 H 11 ) 4N2 Na 4 ] and M[M(C 6 H 11 NH)Sb(l-NC 6 H 11 ) 2N2 Sb]·2thf (M\K or Rb) have been prepared.Comparison of the crystal structures of these species with those of the lithium complexes [MSb 2 (NC 6 H 11 ) 4N2 Li 4 ] and Li[M(C 6 H 11 NH)Sb(l-NC 6 H 11 ) 2N2 Sb] reveals that the geometries of these heterobimetallic cages are fundamentally dictated by the rigidity of the [Sb 2 (NC 6 H 11 ) 4 ]2~ 15 and [M(C 6 H 11 NH)Sb(l-NC 6 H 11 )N2 Sb]~ 16 anions. 36 The synthesis and characterisation of two bis(triphenylantimony)oxo-4-acylpyrazol- 5-ones (4-Me, 4-Ph) and of an analogous derivative of the isomeric ligand 1-acetylpyrazol-5-one have been reported.37 The structure of one compound, [Ph 3 Sb(L)] 2 O (L\1-phenyl-3-methyl-4-benzoylpyrazol-5-one),has been determined and each antimony found to be in a six-co-ordinated Ph 3 SbO 3 environment with a mer-arrangement of the ligand sets.Eleven antimony compounds of the type RSb[(CH 2 ) 3 ] 2 NR@ (R\Cl, I, NCS, OSiPh 3 , Ph; R@\NMe,NCH 2 Ph, NBu*) have been synthesized. The compounds were compared to their arsenic, antimony and bismuth analogues taken from the literature.Evidence was provided for 1,5-chelation of Sb and N via crystal structure determinations, 13C and 29Si NMR chemical shifts, 121Sb and 127I Mo� ssbauer data, cyclic voltammetry, and semi-empiricalMO calculations at the extended Huckel level.38 The reaction of the lithium amide M[2-(6-methyl)pyridyl]trimethylsilylamidoNlithium, with antimony(III) or bismuth(III) trichloride gave the bis-amido antimony(III) or bismuth(III) chloride [M2-(6-Me)C 5 H 3 NNNSiMe 3 ]MCl (M\Sb, Bi).The antimony complex is monomeric in the solid state whereas the bismuth complex is dimeric with bridging chlorides.39 5 Bismuth Synthetic, spectroscopic (IR, Raman, NMR, APCI (atmospheric pressure chemical ionisation)-MS), and X-ray crystallographic studies demonstrate that the highly favorable thiolation of bismuth can be controlled by manipulating stoichiometric conditions for the reactions of BiCl 3 or Bi(NO 3 ) 3 with aminoethanethiolate anions.With this approach, the first homologous series of mono-, bis- and tris-thiolated Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 64bismuth complexes have been isolated and compre-hensively characterized.These include tris(aminoethanethiolato)bismuth(III), bis(aminoethanethiolato)bismuth(III) nitrate, and bis(aminoethanethiolato)bismuth(III) chloride, the corresponding dimethylaminoethanethiolato derivatives and (dimethylaminoethanethiolato)bismuth( III) chloride. The acyclic (dimethylammoniumethanethiolato)bismuth(III) chloride extends the series and represents decoupling of the amine by protonation with the retention of monothiolation.The synthetic guidelines have been postulated to be applicable to other metals and other asymmetric ligands.40 The structure of a very unusual bismuth(III) thioether complex [Bi 4 Cl 12 (MeSCH 2 CH 2 CH 2 SMe) 4 ]·nH 2 O has been reported, where the BiCl 12 (g1- MeSCH 2 CH 2 CH 2 SMe) 4 tetrameric units are linked by bridging dithioether ligands to give a three-dimensional polymeric network; the Bi 4 Cl 4 core is an eight-membered heterocycle which adopts an open cradle conformation.41 The new pentavalent bismuth(V) alkoxide complexes Ph 3 Bi(OR) 2 , Ph3 BiBr(OR) and Ph 4 Bi(OR), (R\C 6 F 5 , C 6 Cl 5 ) have been prepared.42 These compounds were characterized spectroscopically and by single-crystal X-ray di§raction.In the solid state, they possess distorted trigonal bipyramidal co-ordination geometries. The mixed species Ph 3 BiBr(OR) very rapidly redistributes in solution to give equilibrium mixtures of Ph 3 Bi(OR) 2 and Ph 3 BiBr 2 . Trends observed in the values of K%2 correlate with di§erences in the electronegativity of the mixed X species. The thermal stabilities of Ph 3 Bi(OR) 2 have been examined in toluene solution and in the solid state.A number of main group element–transition metal cluster compounds based upon a hexa-capped M 8 cube have been reported in two configurations: empty and with interstitial metal atoms in the center of the cube. Related structures such as [N(PPh 3 ) 2 ] 2 [Bi 4 Co 9 (CO) 16 ]·2thf and [N(PPh 3 ) 2 ] 2 [Bi 8 Co 14 (CO) 20 ]·1.08thf have been characterized by single-crystal X-ray di§raction.A thorough theoretical analysis of these two compounds was undertaken.43 The syntheses and single-crystal X-ray structure determinations have been reported for a number of adducts of bismuth(III) nitrate with the aromatic bidentate base systems 2,2@-bipyridine and 1,10-phenanthroline,44 as well as their halide analogues.45 Vibrational spectroscopic studies of the bismuth(III) halide N,N@-aromatic bidentate base systems were subsequently reported.46 References 1 K.K.Hii and T. P. Kee, Annu. Rep. Prog. Chem., Sect. A, 1998, 94, 99. 2 L.F. Szczepura, L. M. Witham and K. J. Takeuchi, Coord. Chem. Rev., 1998, 174, 5. 3 N. Emig, H. Nguyen, H. Krautscheid, R. Reau, J. B. Cazaux and G.Bertrand, Organometallics, 1998, 17, 3599. 4 M. Ghisletta, L. Hausherr Primo, K. Gajda Schrantz, G. Machula, L. Nagy, H. W. Schmalle, G. Rihs, F. Endres and K. Hegetschweiler, Inorg. Chem., 1998, 37, 997. 5 K. Hegetschweiler, M. Weber, V. Huch, R. J. Geue, A. D. Rae, A. C. Willis and A. M. Sargeson, Inorg. Chem., 1998, 37, 6136. 6 S. Uozumi, H. Furutachi, M. Ohba, H. Okawa, D.E. Fenton, K. Shindo, S. Murata and D. J. Kitko, Inorg. Chem., 1998, 37, 6281. 7 C. J. Matthews, W. Clegg, S. L. Heath, N. C. Martin, M. N. S. Hill and J. C. Lockhart, Inorg. Chem., 1998, 37, 199. 8 G.A. van Albada, J. J. A. Kolnaar, W. J. J. Smeets, A. L. Spek and J. Reedijk, Eur. J. Inorg. Chem., 1998, 1337. 9 R. Koerner, M. M. Olmstead, A. Ozarowski, S. L. Phillips, P. M. van Calcar, K. Winkler and A.L. Balch, J. Am. Chem. Soc., 1998, 120, 1274. Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 6510 F. Gomez de la Torre, F. A. Jalon, A. Lopez Agenjo, B. R. Manzano and A. Rodriguez, Organometallics, 1998, 17, 4634. 11 H. Keypour, R. G. Pritchard and R. V. Parish, Transition Met. Chem., 1998, 23, 121. 12 C. A. Otter, S. M. Couchman, J. C. Je§ery, K.L. V. Mann, E. Psillakis and M. D. Ward, Inorg. Chim. Acta, 1998, 278, 178. 13 X. G. Zhou, Z. E. Huang, R. F. Cai, L. X. Zhang, X. F. Hou, X. J. Feng and X. Y. Huang, J. Organomet. Chem., 1998, 563, 101. 14 G. S. He, S. K. Loh, J. J. Vittal, K. F. Mok and P. H. Leung, Orgometallics, 1998, 17, 3931. 15 H. P. S. Chauhan, Coord. Chem. Rev., 1998, 173, 1. 16 N. Brodie and S. Juge, Inorg.Chem., 1998, 37, 2438. 17 W.H. Hersh, P. Xu, C. K. Simpson, T. Wood and A. L. Rheingold, Inorg. Chem., 1998, 37, 384. 18 P. H. Leung, G. H. Quek, H. Lang, A. M. Liu, K. F. Mok, A. J. P. White, D. J. Williams, N. H. Rees and W. McFarlane, J. Chem. Soc., Dalton Trans., 1998, 1639. 19 W. Goertz, W. Keim, D. Vogt, U. Englert, M.D. K. Boele, L. A. van der Veen, P. C. J. Kamer and P.W.N. M. van Leeuwen, J. Chem. Soc., Dalton Trans., 1998, 2981. 20 N. Krause, Angew. Chem., Int. Ed., 1998, 37, 283. 21 B. Glaser and H. Kunz, Synlett, 1998, 53. 22 S. Vyskocil, M. Smrcina, V. Hanus, M. Polasek and P. Kocovsky, J. Org. Chem., 1998, 63, 7738. 23 R. Bayersdorfer, B. Ganter, U. Englert, W. Keim and D. Vogt, J. Organomet. Chem., 1998, 552, 187. 24 H. P. S. Chauhan, Coord.Chem. Rev., 1998, 173, 1. 25 H. P. S. Chauhan, B. Nahar and R. K. Singh, Synth. React. Inorg. Metal-Org. Chem., 1998, 28, 1541. 26 A. von Dollen and H. Strasdeit, Eur. J. Inorg. Chem., 1998, 61. 27 B.W. Eichhorn, S. P. Mattamana, D. R. Gardner and J. C. Fettinger, J. Am. Chem. Soc., 1998, 120, 9708. 28 J. E. Davies, L. C. Kerr, M. J. Mays, P. R. Raithby, P. K. Tompkin and A.D. Woods, Angew. Chem., Int. Ed., 1998, 37, 1428. 29 M. Scheer, J. Muller, G. Baum and M. Haser, Chem. Commun., 1998, 2505. 30 L. Weber, M.H. Sche§er, H. G. Stammler and B. Neumann, Eur. J. Inorg. Chem., 1998, 55. 31 K. Megges, E. V. Avtomonov, R. Becker and J. Lorberth, Z. Naturforsch., Teil B, 1998, 53, 371. 32 P. Jutzi, S. Pilotek, B. Neumann and H. G. Stammler, J. Organomet.Chem., 1998, 552, 221. 33 O.M. Kekia and A. L. Rheingold, Organometallics, 1998, 17, 726. 34 I. M. Muller and W. S. Sheldrick, Eur. J. Inorg. Chem., 1998, 1999. 35 J. E. Davies, L. C. Kerr, M.J. Mays, P. R. Raithby, P. K. Tompkin and A. D. Woods, Angew. Chem., Int Ed., 1998, 37, 1428. 36 A. Bashall, M. A. Beswick, C. N. Harmer, A. D. Hopkins, M. McPartlin, M. A. Paver, P. R. Raithby and D. S. Wright, J. Chem. Soc., Dalton Trans., 1998, 1389. 37 M.F. Mahon, K. C. Molloy, B. A. Omotowa and M. A. Mesubi, J. Organomet. Chem., 1998, 560, 95. 38 E. Brau, A. Zickgraf, M. Drager, E. Mocellin, M. Maeda, M. Takahashi, M. Takeda and C. Mealli, Polyhedron, 1998, 17, 2655. 39 C. L. Raston, B.W. Skelton, V. A. Tolhurst and A. H. White, Polyhedron, 1998, 17, 935. 40 G. G. Briand, N. Burford, T. S. Cameron and W. Kwiatkowski, J. Am. Chem. Soc., 1998, 120, 11 374. 41 A. R. J. Genge, W. Levason and G. Reid, Chem. Commun., 1998, 2159. 42 S. Hoppe and K. H. Whitmire, Organometallics, 1998, 17, 1347. 43 B. Zouchoune, F. Ogliaro, J. F. Halet, J. Y. Saillard, J. R. Eveland and K. H. Whitmire, Inorg. Chem., 1998, 37, 865. 44 L. J. Barbour, S. J. Belfield, P. C. Junk and M. K. Smith, Aust. J. Chem., 1998, 51, 337. 45 G. A. Bowmaker, F. M. M. Hannaway, P. C. Junk, A. M. Lee, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 331. 46 G. A. Bowmaker, P. C. Junk, A. M. Lee, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 317; G. A. Bowmaker, F. M. M. Hannaway, P. C. Junk, A. M. Lee, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 325; G. A. Bowmaker, J. M. Harrowfield, P. C. Junk, B. W. Skelton and A. H. White, Aust. J. Chem., 1998, 51, 285. Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 57–66 66