SYNTHESIS, STRUCTURE, AND LIGAND DYNAMICS OF TRIOSMIUM IMIDOYL CLUSTERS AND THEIR ISOCYANIDE DERIVATIVES

The synthesis of (mu-H)(mu-eta2-C=NCH2CH2CH2)Os3(CO)10 (10), the copro duct (mu-H)(mu-eta1-NCH2CH2CH2CH2)Os3(CO)10 (9) and the related imidoy l cluster (mu-H)(mu-eta2-CH3CH2C=NCH2-CH2CH3)Os3(CO)10 (11) are report ed. Thermolysis of 9 at 98-degrees-C yields 10 quantitatively, and bot h 10 and 11 are decarbonylated thermally or photochemically to yield m u3-imidoyl clusters (mu-H) (mu3-eta2-C=NCH2CH2CH2)Os3(CO)9 (2) and (mu -H) (mu3-eta2-CH3CH2C=NCH2CH2CH3)Os3(CO)9 (3), respectively. The react ions of 2 and 3 with RNC (R = CH3, C(CH3)3) are reported, and in both cases initial adducts (mu-H)(mu-eta2-C=NCH2CH2CH2)Os3(CO)9(CNR) (R = C H3, 12; R = C(CH3)3, 13) and (mu-H)(mu-eta2-CH3CH2C=NCH2CH2CH3)Os3(CO) 9(CNR) (R = CH3, 14; R = C(CH3)3,15) are isolated in high yield. Therm olysis of 12-15 at 128-degrees-C yields the mu3-imidoyl complexes (mu- H)(mu3-eta2-C=NCH2CH2CH)2Os3(CO)8(CNR) (R = CH3, 16; R = C(CH3)3, 17) and (mu-H)(mu3-eta2-CH3CH2C=NCH2CH2CH3)Os3(CO)8(CNR)(R = CH3,18; R = C (CH3)3,19). Variable temperature H-1- and C-13-NMR and H-1- and C-13-E XSY experiments are reported for 2, 10, and 16-19 which reveal, in det ail, the multistage nature of the ligand exchange processes. In soluti on, complexes 12-19 exist as a large number of positional isomers whic h do not interconvert in the case of 12-15 but which are interconverte d by the motion of the mu3-imidoyl ligand and axial-radial exchange in 16-19. Solid-state structures for 2, 9, 12, 13, and 16 are reported. Compound 2 crystallizes in the monoclinic space group P2(1)/m with uni t cell parameters a = 7.681(1) angstrom, b = 14.801(2) angstrom, c = 8 .157(2) angstrom, beta = 106.06(l)-degrees, V = 891(1) angstrom3, and Z = 2. Least-squares refinement of 2179 reflections gave a final agree ment factor of R = 0.044 (R(w) = 0.043). Compound 9 crystallizes in th e triclinic space group P2(1) with unit cell parameters a = 9.294(3) a ngstrom, b = 15.758(5) angstrom, c = 7.406(2) angstrom, alpha = 81.10( 2)-degrees, beta = 76.47(2)-degrees, gamma = 74.88(2)-degrees, V = 992 (1) angstrom3, and Z = 2. Least-squares refinement of 2677 reflections gave a final agreement factor of R = 0.037 (R(w) = 0.044). Compound 1 2 crystallizes in the monoclinic space group P2(1)/n with unit cell pa rameters a = 8.987(2) angstrom, b = 16.067(2) angstrom, c = 14.436(3) angstrom, beta = 93.06(1)-degrees, V = 2081(1) angstrom3, and Z = 4. L east-squares refinement of 2579 reflections gave a final agreement fac tor of R = 0.051 (R(w) = 0.057). Compound 13 crystallizes in the monoc linic space group P2(1)/c with unit cell parameters a = 9.216(1) angst rom, b = 19.372(5) angstrom, c = 15.176(3) angstrom, beta = 116.38(2)- degrees, V = 2427(2) angstrom3, and Z = 4. Least-squares refinement of 4673 reflections gave a final agreement factor of R = 0.044 (R(w) = 0 .053). Compound 16 crystallizes in the triclinic space group P2(1)/c w ith unit cell parameters a = 8.574(4) angstrom, b = 15.660(6) angstrom , c = 8.437(2) angstrom, a = 80.69(4)-degrees, beta = 67.12(4)-degrees , gamma = 74.09(4)-degrees, V = 1002(1) angstrom3, and Z = 2. Least-sq uares refinement of 3738 reflections gave a final agreement factor of R = 0.058 (R(w) = 0.061).