No abstract

The 31 P chemical shift anisotropies have been measured at 293 K for the triphenylphosphine ligands in solid pentacarbonyl(triphenylphosphine)chromium(0), Cr(CO) 5 (PPh 3 ) (1), and cis-and trans-tetracarbonyl(triphenylphosphine)(thiocarbonyl)chromium(0), Cr(CO) 4 (PPh 3 )(CS) (2 and 3). The major changes in the shift tensors occur for the δ 11 and δ 22 components perpendicular to the Cr-P bond direction. The individual tensor components of the 31 P chemical shifts are clearly more important than are the isotropic values in providing information on the chromium-phosphorus bonding. The crystal structure of 3 has been determined by single-crystal X-ray diffraction. The complex crystallizes in the monoclinic P2 1 /n (No. 14) space group with cell constants (at 293 K) a ) 9.558(5) Å, b ) 15.275(2) Å, c ) 15.341(2) Å, ) 96.66(2)°, V ) 2225(1) Å 3 and Z ) 4; R ) 0.069 and R w ) 0.067. The crystal structure of 1 has been reported previously and most of the structural features are quite similar to those for 3. For instance, the Cr-P distances are 2.422(4) Å for 1 and 2.424(4) Å for 3. The P-Cr-C(S) and Cr-C-S linkages in 3 are almost linear with the angles being 178.4(4) and 174.

Vibrational assignments are reported for the room-temperature IR and Raman spectra of three series of solid group 6B metal(0) carbonyl-tert-butyl isocyanide complexes of the general formula M(CO), -,(CNBu-t), , where M = Cr, Mo, W and n = 1-3. Sequential replacement of the CO groups by CNBu-t leads to gradual shifts of the V(CN) bands to higher energies, while the V(C0) bands shift to lower energies. These results provide good evidence for the stronger a-donor and weaker n-acceptor capacities of the CNBu-t ligand compared with those of CO.

The 31P chemical shift anisotropies have been measured for solid triphenyl phosphite, P(OPh)3 (at 128 K), and the complex with the tricarbonyl(thiocarbonyl)chromium(0) moiety, me/V/-ti/M-Cr(CO)3(CS) [P(OPh)3] 2 (at 298 K). The shift tensor is axially symmetric in the phosphite ligand, and the major change upon complexation occurs for the components of the shift tensor perpendicular to the bond direction. The crystal structure of the chromium complex has been determined by single-crystal X-ray diffraction at 293 K. The complex crystallizes in the centric P2\/n (No. 14) space group with cell constants (at 20 °C) a = 8.166(3) Á, b = 11.530(2) Á, c = 20.183(2) Á, ß = 96.43(1)°, and Z = 2. The molecule is disordered on a crystallographically imposed inversion center so that the thiocarbonyl ligand is superimposed on the trans carbonyl ligand (50:50).

A convenient method for embedding organometallic complexes in polymer films has been developed and the FT-IR spectra of these films have been investigated at room temperature. Infrared data in the v(C0) stretching region are reported for M(CO), (M=Cr, Mo, W), CpMn(CO), (Cp=q5-CsH,), q-C6H6Cr(CO),L [L= co, P(n-Bu)31, ($6-C6HSNH2)Cr(C0)3, [q6-O-c~H,(NH,)M~c~(co),I, C pFe( CO) LR [L=CO, PPh,; R=Me, C(O)Me] embedded in poly(methy1 methacrylate) (PMMA), polystyrene (PS), polystyrene-poly(methy1 methacrylate) (PS-PMMA), and polystyrene-polyacrylonitrile(PS-AN) plastic films. These matrices appear to approximate the common solvents ethyl acetate, toluene, toluene-ethyl acetate, and toluene-acetonitrile, respectively, with respect to v( CO) vibrational band behavior. Several of the films have been subjected to UV irradiation and the photoproducts formed have been identified by FT-IR spectroscopy. PS-AN effectively traps photogenerated coordinatively unsaturated species via coordination of its pendant nitrile groups.