摘要:

DALTON J. Chem. Soc. Dalton Trans. 1997 Pages 4651–4655 4651 Synthesis and X-ray powder diVraction characterization of (OC)2RhCl2Rh(cod) (cod 5 cycloocta-1,4-diene) Eleonora Corradi,a Norberto Masciocchi,a Gyula Pályi,*,b Renato Ugo,c Anna Vizi-Orosz,d Claudia Zucchi b and Angelo Sironi *,†,a a Dipartimento di Chimica Strutturale e Stereochimica Inorganica and Centro CNR CSSMTBO Università di Milano via Venezian 21 20133 Milano Italy b Dipartimento di Chimica Università di Modena via Campi 183 41100 Modena Italy c Dipartimento di Chimica Inorganica Metallorganica ed Analitica and Centro CNR CSSMTBO Università di Milano via Venezian 21 20133 Milano Italy d Research Group for Petrolchemistry Hungarian Academy of Sciences Egyetem u. 8 8200 Veszprém Hungary In order to elucidate the nature and the structure of the elusive (OC)2Rh(Ph3SiO)2Rh(cod) (cod) = cycloocta-1,5- diene) complex an important model compound for surface catalysis (OC)2RhCl2Rh(cod) has been synthesized and structurally characterized by ab initio X-ray powder diffraction.Crystals of (OC)2RhCl2Rh(cod) are monoclinic space group P21/c a = 6.659(1) b = 12.274(1) and c = 16.096(1) Å b = 92.176(5)8 Z = 4 rcalc = 2.209 g cm23. The structure has been solved from powder diffraction data only by Patterson and Fourier-difference methods and has been ultimately refined by the Rietveld method down to Rp = 0.116 and Rwp = 0.154 for 4050 data points collected in the 12–938 (2q) range. The molecule contains two square-planar rhodium atoms one bearing two terminal carbonyls and the other bound to the chelating cod fragment and two chlorine atoms bridging the Rh ? ? ? Rh vector.The Rh2Cl2 core is markedly non-planar the dihedral angle about the Cl ? ? ? Cl hinge being 135.4(6)8. The ‘two-dimensional chemistry’ 1 observed with transitionmetal complexes supported on oxides is one of the most active sectors of research dealing with transition-metal catalysts.2 In particular many aspects of the surface chemistry of rhodium one of the most effective catalysts,3 were studied including the synthesis of model complexes of supposed surface species 4 and the interconversion of Rh complexes on oxide surfaces.4c,5 Recently these latter studies have proved to be the basis of an efficient cluster synthesis.6 In the course of our earlier efforts in preparing models of surface species of rhodium we observed 7 that the complexes (OC)2Rh(Ph3SiO)2Rh(CO)2 and (cod)Rh(Ph3SiO)2Rh(cod) (cod = cycloocta-1,5-diene) are easily interconvertible.Now we report on the formation of an intermediate of this reaction (OC)2Rh(Ph3SiO)2Rh(cod) which is fairly unstable in solution and cannot be satisfactorily characterized by spectroscopic methods. We were unable to grow suitable single crystals (for X-ray diffraction) of such an important intermediate; therefore as indirect evidence of its nature we decided to synthesize and structurally characterize its dichloro-bridged analogue i.e. (OC)2RhCl2Rh(cod). Unfortunately this latter compound did not afford crystals of suitable quality but given its lower complexity it was decided to attempt its complete structural analysis on the basis of ab initio powder diffraction analysis which has been recently shown to be a powerful technique for assessing the crystal and molecular structures of molecular and/or polymeric co-ordination compounds.8,9 Experimental All operations 10 were carried out under a carefully dried deoxygenated and CO2-free Ar or CO atmosphere using dried deoxygenated solvents.Infrared spectra were recorded on IR-75 (Carl Zeiss Jena Germany) and Bruker FT-IR IFS 113V † E-Mail angelo@csmtbo.mi.cnr.it instruments. Proton and 13C NMR spectra were obtained with Bruker AMX and AC200 spectrometers. Starting materials were of commercial origin except for (Ph3SiO)2Rh(CO)4,7 (Ph3SiO)2Rh2(cod)2,7 Cl2Rh2(CO)4,11 Cl2Rh2(cod)2 12 (from commercial RhCl3?xH2O) and Ph3- SiONa,13 which were prepared according to published procedures. Preparation of Cl2Rh2(CO)2(cod) 5 by reaction (i) The complex Cl2Rh2(cod)2 (100 mg 0.20 mmol) was dissolved in dry n-hexane (50 cm3) while being stirred under an Ar atmosphere at 50 8C in a Schlenk vessel which was then left to cool to room temperature (r.t.).To this stirring solution was added at once a solution of Cl2Rh2(CO)4 (78 mg 0.20 mmol) in n-hexane (10 cm3). The color of the initial yellow solution immediately turns orange and the IR n(CO) spectrum of a sample shows almost exclusively the emergence of a new twocomponent band system and some remaining (<10%) signals of Cl2Rh2(CO)4.14 The solution was then cooled to 280 8C for 4 h. Orange-yellow microcrystals were obtained. They were subsequently recrystallized from n-pentane (two to three times) to yield pure crystalline Cl2Rh2(CO)2(cod).Yield 160–170 mg (90– 96%) for the crude and 140-150 mg (79–84%) for the recrystallized product (Found C 28.1; H 2.9; Cl 15.7; Rh 46.5. Calc. for C10H12Cl2O2Rh2 C 27.24; H 2.74; Cl 16.08; Rh 46.68%). IR [n(CO) n-hexane] 2089vs 2022vs cm21. 1H NMR (C6D6 vs. SiMe4) d 4.2 (s br 4 H CH) 2.0 (m 4 H CHH) 1.3 (m 4 H CHH). 13C-{1H} NMR (C6D6 vs. SiMe4) d 179.0 (CO JC]Rh 73) 79.2 (CH JC]Rh 11 Hz) 30.2 (CH2). Preparation of (Ph3SiO)2Rh2(CO)2(cod) 6 by reaction (i) The complex (Ph3SiO)2Rh2(CO)2(cod) 6 was prepared similarly to 5 from 0.2 mmol quantities of (Ph3SiO)2Rh2(cod)2 and (Ph3SiO)2Rh2(CO)4. Yields >90% for the crude and 75–80% for the recrystallized product (Found C 60.3; H 4.8; Rh 22.3. 4652 J. Chem. Soc. Dalton Trans. 1997 Pages 4651–4655 Fig. 1 Rietveld refinement plot for polycrystalline (OC)2RhCl2Rh(cod) in the 12 < 2q < 938 range.Reflection markers and difference plot are also included. The insert shows the full raw data Calc. for C46H42O4Rh2Si2 C 60.00; H 4.60; Rh 22.35%). IR [n(CO) n-hexane] 2078vs 2015vs cm21. 1H NMR (C6D6 vs. SiMe4) d 7.97 7.66 7.24 (m 30 CH Ph) 4.18 (br s 4 H CH) 1.97 (br m 4 H CHH) 1.24 (br m 4 H CHH). 13C-{1H} NMR (C6D6 vs. SiMe4) d 180.1 (CO JC]Rh 76) 138.0 136.8 136.1 130.8 (CH Ph) 79.8 (CH JC]Rh 13 Hz) 31.3 (CH2). Preparation of (Ph3SiO)2Rh2(CO)2(cod) 6 by reaction (ii) The complex (Ph3SiO)2Rh2(CO)4 4 (4 mg 0.05 mmol) was dissolved in dry n-hexane (10 cm3). To this solution while stirring at r.t. under an Ar atmosphere cycloocta-1,5-diene C8H12 (52.0 ml 45.9 mg 0.085 mmol 1.7 equivalents with respect to Rh2) was added in three to four portions during 10 min periods.The reaction mixture was then stirred for an additional 15–20 min. A sample taken for spectroscopic analysis [IR n(CO) region] showed almost complete disappearance of the absorption bands of 4 while the n(CO) bands of 6 were practically those of the sole metal carbonyl species observed. The (spectroscopic) yield was calculated to be higher than 90%. Complex 5 could be prepared analogously from 3 and 1.5–1.7 molar excess of cod yield >95%. Preparation of Cl2Rh2(CO)4 3 by reaction (iii) The complex Cl2Rh2(CO)2(cod) 5 (44 mg 0.1 mmol) was dissolved in dry n-hexane (10 cm3) under an Ar atmosphere. Over this solution while stirring at r.t. the atmosphere was changed to a 1 1 mixture of Ar 1 CO. An immediate color change to orange was observed.The infrared spectroscopic analysis of the reaction mixture showed complete conversion of 5 into 3 after 10 min. The same method for transforming 6 into 4 yielded 30– 40% of complex 6 accompanied by the formation of 20–30% of Rh6(CO)16.15 We observed that if the gases were not perfectly dry humidity caused the formation of even higher quantities of Rh6(CO)16. Using non-diluted CO also favoured the formation of the latter compound. Preparation of (Ph3SiO)2Rh2(CO)2(cod) 6 by ion metathesis [reaction (iv)] The complex Cl2Rh2(CO)2(cod) 5 (44 mg 0.1 mmol) was dissolved in dry n-hexane (10 cm3) under an Ar atmosphere. To this solution while stirred at r.t. Ph3SiONa (66 mg 0.22 mmol) was added in two to three portions during 15–20 min. The solution was analysed by infrared n(CO) spectroscopy after 20 40 and 60 min.After 40 min the spectra showed the formation of ca. 80% of 6 which did not change after 60 min. Reaction (iv) was also followed by 1H NMR spectroscopy using C6D6 as solvent. X-ray powder diVraction of (OC)2RhCl2Rh(cod) The orange powder was deposited with the aid of silicon grease on a silicon monocrystal cut normal to 511 minimizing the scattering from the substrate. Given the limited amount of the available material the ‘infinitely thick’ limit which allows absorption corrections in Bragg–Brentano geometry to be neglected could not be reached; therefore the average isotropic ‘thermal’ parameter which is known to absorb most qdependent systematic errors may be slightly overestimated. The sample was rotated at about 60 rpm about the scattering vector in order to minimize preferred orientation effects.The spectrum was collected under a nitrogen atmosphere to prevent sample decomposition. X-Ray powder diffraction (XRPD) data were taken with Cu-Ka radiation (l = 1.5418 Å) on a Rigaku D III/ MAX horizontal scan powder diffractometer equipped with parallel Soller slits and a graphite monochromator in the diffracted beam. Data were collected in the 3 < 2q < 938 range in the q–2q mode and step scan with D2q = 0.028 and t = 12 s. Slits used DS 1.08; AS 1.08; RS 0.158. Standard peak-search methods were used to locate the diffraction maxima. Indexing was performed using DICVOL 9116 [a = 6.66 b = 12.27 c = 16.10 Å; b = 92.188; M(15) = 34.4; F(15) = 71.1 (0.007 28)]. The space group P21/c was chosen from systematic absences and subsequently confirmed by satisfactory refinement.The integrated intensities were extracted by Le Bail’s method,17 using EXTRA;18 the Rh atoms were located from a Patterson synthesis while the Cl C O and N atoms were located from Fourier-difference maps and model building techniques. The final refinements were performed using the Rietveld method of GSAS19 and restraining Rh]C]O and Rh]cod fragments to known geometries. A single isotropic atomic displacement parameter was refined from the rhodium and chlorine atoms [Uiso = 0.067(2) Å2] while light(er) atoms were J. Chem. Soc. Dalton Trans. 1997 Pages 4651–4655 4653 assigned the same value arbitrarily raised by 0.020 Å2. A more detailed description of the ab initio XRPD methodology applied to moderately complex molecular crystals can be found in ref.20. Crystal data and refinement details are reported in Table 1. A final plot of the Rietveld refinement is shown in Fig. 1. CCDC reference number 186/722. Results and Discussion Synthesis Scheme 1 pictorially shows the different routes and alternative methods employed in the preparation of complexes Cl2Rh2- (CO)2(cod) and (Ph3SiO)2Rh2(CO)2(cod) together with the numbering scheme adopted for all reactants and products. The high yield syntheses from symmetrically substituted bis(diolefinic) (1 or 2) and tetracarbonyl (3 or 4 respectively) Scheme 1 Rh X Rh X OC X CO OC Rh X Rh CO 1 X = Cl 2 X = OSiPh3 3 X = Cl 4 X = OSiPh3 Rh X Rh X OC OC 5 C = Cl 6 X = OSiPh3 OC X CO OC Rh X Rh CO 3 X = Cl 4 X = OSiPh3 Rh Cl Rh Cl OC OC Rh O Rh O OC OC SiPh3 SiPh3 ( i) ( ii) ( iii) ( iv) 5 6 Table 1 Crystal data and refinement details for (OC)2RhCl2Rh(cod) Compound Formula Mr/g mol21 System Space group a/Å b/Å c/Å b/8 U/Å3 ZF (000) rcalc/g cm23 Radiation (l/Å) 2q Range/8 Scan mode No.of parameters No. of reflections Rp Rwp RF (OC)2RhCl2Rh(cod) C10H12Cl2O2Rh2 440.8 Monoclinic P21/c 6.659(1)* 12.274(1) 16.096(1) 92.176(5) 1314.7(2) 4 840 2.209 Cu-Ka (1.5418) 12–93 q:2q 4050 1133 0.116 0.154 0.085 * Estimated standard deviations of lattice parameters are derived from the whole-pattern Rietveld refinement. derivatives clearly indicate that compounds 5 and 6 are the thermodynamically favoured products in the reaction mixture to an extent which is significantly larger than that foreseen by purely entropic (configurational i.e. ‘mixing’) arguments.This implies a small enthalpic stabilization of 5 (and 6) possibly due to the larger polarity of the mixed-ligand derivatives. The observed ‘instability’ to moisture and/or air contamination (in solution and in the solid state) which increases with the carbonyl content in the order 1 < 5 < 3 (and similarly for siloxy derivatives 2 < 6 < 4) could be related to the availability of easy degradation paths leading to stable carbonyl clusters [e.g. Rh6(CO)16] but not to homoleptic poly(olefinic) derivatives. Crystallography As repeated attempts to grow single crystals of 5 suitable for conventional X-ray diffraction methods failed affording either very small (maximum dimensions 20 × 20 × 100 mm) thus poorly diffracting and untreatable (single?) crystals or macroscopic aggregates of polycrystalline nature we decided to characterize 5 via XRPD.Note that in principle we could also have attempted an XRPD characterization of 6; however the foreseen asymmetric unit volume of its crystalline phase (1015 Å3 obtained by averaging that of 2 and 4) 7 was discouraging while that of 5 (328 Å3 obtained by averaging that of 1 and 3) 21 was not. X-Ray powder diffraction methods revealed that 5 contains two square-planar Rh atoms (see Fig. 2) one bearing two terminal carbonyls and the other bound to the chelating cod fragment (chelating four-electron donors h2,h2-cod ligands being idealized by two pseudo-atoms located at the midpoints of the C]] C bonds) joined by two chlorine atoms bridging the Rh ? ? ? Rh vector [Rh ? ? ? Rh 3.252(7) Å; average Rh]Cl 2.40(1) Å].The Rh2Cl2 core is markedly non-planar the dihedral angle about the Cl ? ? ? Cl hinge being 135.4(6)8 thus resembling much more of the geometry of (OC)2RhCl2Rh(CO)2 [126.8(3)8],22a rather than that of the (cod)RhCl2Rh(cod) (1808) 22b analogues. Note that L2M(m-X)2ML2 fragments (M = Co Rh or Ir; X = Cl Br I OR SR or PR2; L = any two-electron donor ligand) based on square-planar metal centers are known to belong to two distinct structural types containing essentially planar or markedly bent M2X2 cores respectively while intermediate conformers are lacking; this bimodal distribution shows two well separated peaks a very sharp one for ‘planar’ conformations and a broader one for bent fragments mainly reflecting the variety of bridging (m-X) and ancillary (L) ligands. As a consequence since 5 does not belong to the ‘planar’ class (for reasons which are not yet understood) it is not surprising that it shows a dihedral angle similar to that of (OC)2RhCl2Rh(CO)2.If the presence of short Rh ? ? ? Rh intermolecular contacts is taken as a criterion of similarity 5 which packs as ‘dimers’ [Rh(2) ? ? ? Rh(29) 3.55(1) Å] is intermediate between Fig. 2 An ORTEP21 drawing of the (OC)2RhCl2Rh(cod) molecule with partial labelling scheme. Relevant bond distances (Å) and angles (8) Rh(1) ? ? ? Rh(2) 3.252(7) Rh(2) ? ? ? Rh(29) 3.55(1) Rh(1)]Cl(1) 2.409(4) Rh(1)]Cl(2) 2.400(4) Rh(2)]Cl(1) 2.396(13) Rh(2)]Cl(2) 2.409(13); Rh(1)]Cl(1)]Rh(2) 85.2(4) Rh(1)]Cl(2)]Rh(2) 85.1(3) [Rh(29) is centrosymmetrically related to Rh(2)] 4654 J. Chem. Soc. Dalton Trans. 1997 Pages 4651–4655 (OC)2RhCl2Rh(CO)2 and (cod)RhCl2Rh(cod).Indeed while the former is a ‘polymer’ with Rh ? ? ? Rh contacts of 3.31 Å no short interactions are observed in the latter. A closer analysis shows that short contacts invariably involve the Rh atoms bound to carbonyls thus suggesting that the presence of (bulky) cod ligands requires long(er) Rh ? ? ? Rh contacts. As meaningful Rietveld XRPD refinements require introduction of numerous constraints on the geometrical values of chemically known fragments at least when working with conventional instrumentation only the packing and conformations of the molecules together with the heavy atom locations can be assessed with reasonable accuracy. The introduction of constraints normally drives the ‘molecular’ shape toward an idealized conformation with loss of structural details (which are anyway unaccessible by PD) but hardly control intermolecular contacts.For instance at the end of the refinement we still observe a rather short packing contact [namely O(1) ? ? ? O(19) 2.67(6) Å] which could be easily relaxed by small but unpredictable structural changes. For this reason we have further checked the obtained results by minimizing the steric energy of different molecular conformations in the actual crystal lattice with a locally developed 23 version of Allinger’s MM3 program.24 On adopting the empirical force field for p-bonding ligands discussed in ref. 25 avoiding any bias toward the planar or bent conformations at the intramolecular level all deformation paths of the central Rh2Cl2 butterfly from the geometry determined by XRPD substantially raised the overall (intramolecular 1 packing) steric energy; this is pictorially shown in Fig.3(a) which contains a section of the potential energy hypersurface along the Cl ? ? ? Cl and Rh ? ? ? Rh coordinates all other degrees of freedom being optimized at each (hyper)point. This does not imply that the observed stereochemistry is dictated by packing constraints but rather that the experimentally accessible lattice parameters and symmetry alone may contain useful information on the molecular stereochemistry. For instance in the present case at the resolution stage where only the Rh2Cl2 core was known we could immediately devise which rhodium atom was Fig. 3 (a) A three-dimensional view of the potential energy hypersurface (kcal mol21 cal = 4.184 J) projected onto the Rh ? ? ? Rh vs.Cl ? ? ? Cl plane (values in Å); (b) and (c) monodimensional cuts of the Rwp hypersurface along the Rh ? ? ? Rh and Cl ? ? ? Cl directions respectively bound to cod by simple packing considerations. Such information could be in principle exploited by joint Rietveld/steric energy/packing energy refinements but this feature has not been implemented on currently available programs. The common use of restraints in complex Rietveld refinements (ensuring chemical significance to the derived parameters) normally obtained by introducing new observational equations of geometrical nature may be interpreted as a very rough approach of optimization of a few intramolecular degrees of freedom. Within the GSAS approach this corresponds to harmonic potential wells for stretching modes (bond distances) with arbitrary force constants; since bond angles and torsions cannot be restrained 1,3 and 1,4 distances may be in principle included.However if the minima of the two cost functions (Rwp in the Rietveld refinement and Etot in the MM program) are close as in the present case [compare Fig. 3(a) with the monodimensional cuts of Rwp surface reported in Fig. 3(b) and 3(c)] even independent Rietveld and steric energy/packing energy refinements can be used to confirm the reliability of the proposed molecular conformation. A similar approach involving only intermolecular (i.e. packing and electrostatic) energies and very limited diffraction data sets (2q < 308 Cu-Ka radiation) has been used for structural analysis of the monoclinic polymorph of titanophthalocyanine.26 Note that our computations represent only a shortcut to the correct approach (the joint refinement) since even if the two minima match (which is not always true mainly because of the intrinsic weakness of the force field) their curvatures may not. Indeed Rwp is much more sensitive to the Rh ? ? ? Rh than to the Cl ? ? ? Cl deformation [compare Fig. 3(b) and 3(c)] since it is more ‘expensive’ to displace high Z atoms contributing the most to the diffraction pattern. Conversely from Fig. 3(a) it is clear that the potential energy hypersurface is softer along the Rh ? ? ? Rh direction rather than along the Cl ? ? ? Cl. Conclusion The preparation of complexes 5 and 6 complements our earlier observations about the formation of dinuclear rhodium carbonyl complexes with two different anions in the bridging position.4b The existence of complexes 5 and especially 6 is of an additional significance since it shows that the greatest care should be taken on formulating the Rh-containing surface species; indeed as demonstrated earlier 7 and in this work the actual ligand environment of rhodium is found to be very sensitive to the reaction conditions.Once again XRPD (from conventional laboratory equipment) has been proven to be a useful tool in addressing structural problems which have no easy solution with standard techniques. As a matter of fact it is likely that new instrumentation and sources (high brilliance synchrotrons and time of flight neutrons) will soon raise the complexity of the organometallic molecules which can be characterized by PD. Nevertheless even in the future it will be the daily use of easily accessible conventional instrumentation which will provide the organometallic chemistry community with otherwise inaccessible structural results,8 well beyond the conventional use of XRPD as an ‘analytical’ tool.Acknowledgements Support of this work by the (Italian) Ministry of University and Research (MURST 40%) is acknowledged. The technical support of Mrs. G. Mezza and P. Illiano is also acknowledged. References 1 G. A. Somorjai Chemistry in Two Dimensions Surfaces Cornell University Press Ithaca 1981; G. A. Somorjai Introduction to Surface Chemistry and Catalysis Wiley New York 1994. J. Chem. Soc. Dalton Trans. 1997 Pages 4651–4655 4655 2 R. Psaro and R. Ugo Metal Clusters in Catalysis eds. B. C. Gates L. Guczi and H.Knötzinger Elsevier Amsterdam 1986 p. 427; H. H. Lamb B. C. Gates and H. Knötzinger Angew. Chem. Int. Ed. Engl. 1988 27 1127; J. M. Basset B. C. Gates J. P. Candy A. Choplin M. Lecomte F. Quignard and C. Santini (Editors) Surface Organometallic Chemistry Molecular Approaches to Surface Catalysis Kluwer Dordrecht 1988; R. Psaro D. Roberto R. Ugo C. Dossi and A. Fusi J. Mol. Catal. 1992 74 391. 3 L. Marko Aldehyde (methoden der Organischen Chemie Houben- Weyl) ed. J. Falbe Thieme Stuttgart 1983 vol. E3 p. 224; F. H. Jardine The Chemistry of the Metal-Carbon Bond ed. F. R. Hartley J. Wiley New York 1987 vol. 4 p. 733 1049; D. Parker ibid. p. 979; F. R. Hartley ibid. p. 1163; V. Ponec New Trends in CO Activation ed. L. Guczi Elsevier Amsterdam 1991 p. 117; C. H. Batholomew ibid. p.158; H. M. Colquhoun D. J. Thompson and M. W. Twigg Carbonylation Plenum Press New York 1991; R. J. Farruto R. M. Heck and B. K. Speronello Chem. Eng. News 1992 (Sept. 7) 34. 4 (a) A. Vizi-Orosz G. Pályi and L. Marko J. Organomet. Chem. 1973 57 379; (b) G. Pályi A. Vizi-Orosz L. Marko F. Marcati and G. Bor J. Organomet. Chem. 1974 66 295; (c) A. Theolier A. K. Smith M. Lecomte J. M. Basset G. M. 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Sironi J. Chem. Soc. Dalton Trans. 1993 471; N. Masciocchi P. Cairati F. Ragaini and A. Sironi Organometallics 1993 12 4499; N. Masciocchi M. Moret P. Cairati A. Sironi G. A. Ardizzoia and G.La Monic J. Am. Chem. Soc. 1994 116 7768; N. Masciocchi M. Moret P. Cairati A. Sironi G. A. Ardizzoia and G. La Monica J. Chem. Soc. Dalton Trans. 1995 1671; N. Masciocchi M. Moret A. Sironi G. A. Ardizzoia S. Cenini and G. La Monica J. Chem. Soc. Chem. Commun. 1995 1955; N. Masciocchi G. A. Ardizzoia G. La Monica M. Moret and A. Sironi Inorg. Chem. 1997 36 449. 10 D. F. Shriver and M. A. Drezdon The Manipulation of Air-Sensitive Compounds Wiley New York 2nd edn. 1986. 11 J. A. McCleverty and G. Wilkinson Inorg. Synth. 1966 8 211. 12 G. Giordano and R. H. Crabtree Inorg. Synth. 1979 19 218. 13 L. H. Sommer E. W. Petrusza and F. C. Whitemore J. Am. Chem. Soc. 1946 68 2283. 14 B. F. G. Johnson J. Lewis and P. W. Robinson J. Chem. Soc. A 1969 2693. 15 E. R. Corey L. F. Dahl and W. Beck J.Am. Chem. Soc. 1963 85 1202; L. Malatesta G. Caglio and M. Angoletta Chem. Commun. 1970 532. 16 A. Boultif and D. Louër J. Appl. Crystallogr. 1991 24 987. 17 A. Le Bail H. Duroy and J. L. Fourquet Mater. Res. Bull. 1988 23 447. 18 A. Altomare G. Cascarano C. Giacovazzo A. Guagliardi A. G. G. Moliterni M. C. Burla and G. Polidori J. Appl. Crystallogr. 1995 28 738. 19 A. C. Larson and R. B. Von Dreele LANSCE Ms-H805 Los Alamos National Laboratory NM 1990. 20 N. Masciocchi P. Cairati and A. Sironi Powder Diffr. 1997 in the press. 21 C. K. Johnson ORTEP Report ORNL-5138 Oak Ridge National Laboratory Oak Ridge TN 1976. 22 (a) Cl2Rh2(CO)4 L. F. Dahl C. Martell and D. L. Wampler J. Am. Chem. Soc. 1961 83 1761; L. Walz and P. Scheer Acta Crystallogr. Sect. C 1991 47 640; (b) Cl2Rh2(cod)2 J. A. Ibers and R. G. Snyder Acta Crystallogr. 1962 15 923; J. C. A. Boeyens L. Denner S. W. Orchard I. Rencken and B. G. Rose S. Afr. J. Chem. 1986 32 229. 23 P. Mercandelli M. Moret and A. Sironi unpublished work. 24 N. L. Allinger Y. H. Yuh and J. H. Lii J. Am. Chem. Soc. 1989 111 8551. 25 P. Mercandelli and A. Sironi J. Am. Chem. Soc. 1996 118 11 548. 26 K. Oka O. Okada and K. Nukada Jpn. J. Appl. Phys. Part 1 1992 31 2181. Received 2nd July 1997; Paper 7/04688E

ISSN:1477-9226    

DOI:10.1039/a704668e

出版商:RSC    

年代:1997

数据来源: RSC