PHOSPHINE ADDITION AND SUBSTITUTION-REACTIONS ON UNUSUALLY REACTIVE TRIOSMIUM CLUSTERS - (MU-H)(MU-3-ETA-2-C=NCH2CH2CH2)OS3(CO)9 AND (MU-H)(MU-3-ETA-2-CH3CH2C=NCH2CH2CH3)OS3(CO)9

The reactions of (mu-H)(mu-3-eta-2- activated C = NCH2CH2CH2)Os3(CO)9 (1), (mu-H)(mu-3-eta-2-CH3CH2C = NCH2CH2CH3)-Os3(CO)9 (2), (mu-H)(mu-eta-2- activated C = NCH2CH2CH2)Os3(CO)10 (3), and (mu-H)(mu-eta-2-CH3CH2C = NCH2CH2CH3)Os3(CO)10 (4) with trialkylphosphines at 25-100-degrees-C have been studied. At room temperature 1 gives a phosphine addition product (mu-H)(mu-eta-2- activated C = NCH2CH2CH2)Os3(CO)9P(C6H5)3 (5) where the phosphine has added to the metal atom formerly pi-bound to the C = N bond of the mu-3-imidoyl ligand; 5 exists as two isomers in solution. Compound 5 rearranges to the isomeric 6a and 6b at 100-degrees-C in which the phosphine is at one of the two metal atoms bridged by the hydride and the imidoyl ligand. At 100-degrees-C 3 substitutes phosphine for carbonyl to also give 6a and 6b, which on further thermolysis at 125-degrees-C decarbonylate to give (mu-H)(mu-3-eta-2- activated C = NCH2CH2CH2)Os3(CO)8P(C6H5)3 (7). In contrast, reaction of 2 with triphenylphosphine at room temperature gives (mu-H)(mu-eta-2-CH3CH2C = NCH2CH2CH3)Os3(CO)9P(C6H5)3) (8), which exists as a mixture of five of six possible positional isomers with respect to location of the phosphine, hydride, and imidoyl ligands in solution. The reaction of 4 with triphenylphosphine at 100-degrees-C gives this same mixture of isomers. Decarbonylation of 8 proceeds at 125-degrees-C to give (mu-H)(mu-3-eta-2-CH3CH2C = NCH2CH2CH3)Os3-(CO)8P(C6H5)3) (9) and the dihydrido orthometalation product (mu-H)2(mu-eta-2-CH3CH2C = NCH2CH2CH3)Os3(CO)8(mu-eta-2-(C6H5)2P(omicron-C6H4)) (10). Reaction of 2 with trimethylphosphine or trimethyl phosphite gives the addition products (mu-H)(mu-eta-2-CH3CH2C = NCH2CH2CH3)Os3(CO)9PR3 (R = CH3, 11; R = OCH3, 12), which are structurally analogous to 5 in solution. The origin of the structural differences between the addition products obtained from the reaction of 1 and 2 with P(C6H5)3 and from 2 with the different phosphorous ligands is discussed in terms of steric interactions between the imidoyl ligand and the phosphorous ligand. All compounds reported were characterized by H-1 NMR, infrared spectroscopy, and elemental analysis. In addition, solid-state structures for 5, 6a, 8a, and 9 were determined. Compound 5 crystallizes in the triclinic space group P1BAR (No.2) with unit cell parameters a = 10.762 (2) angstrom, b = 17.442 (2) angstrom, c = 8.595 (2) angstrom, alpha = 97.38 (1)-degrees, beta = 94.04 (1)-degrees, gamma = 97.44 (1)-degrees, V = 1580 (1) angstrom 3, and Z = 2. Subsequent least-squares refinement of 5058 reflections gave a final agreement factor of R = 0.032 (R(w) = 0.041). Compound 6a crystallizes in the monoclinic space group P2(1)/c (No. 14) with unit cell parameters a = 9.307 (2) angstrom, b = 15.601 (3) angstrom, c = 21.773 (4) angstrom, beta = 97.59 (2)-degrees, V = 3134 (2) angstrom 3, and Z = 4. Least-squares refinement of 4316 reflections gave a final agreement factor of R = 0.029 (R(w) = 0.036). Compound 8a crystallizes in the triclinic space group P1BAR (No. 2) with unit cell parameters a = 12.684 (3) angstrom, b = 16.254 (3) angstrom, c = 9.561 (2) angstrom, alpha = 99.53 (1)-degrees, beta = 96.69 (2)-degrees, gamma = 112.57 (2) angstrom, V = 1760 (1) angstrom 3, and Z = 2. Least-squares refinement of 4236 reflections gave a final agreement factor of R = 0.031 (R(w) = 0.038). Compound 9 crystallizes in the orthorhombic space group P2(1)2(1)2(1) (No. 19) with unit cell parameters a = 9.626 (1) angstrom, b = 15.342 (2) angstrom, c = 22.849 (3) angstrom, V = 3374 (1) angstrom 3, and Z = 4. Least-squares refinement of 2841 reflections gave a final agreement factor of R = 0.031 (R(w) = 0.027).