TRIOSMIUM AND TRIRUTHENIUM CLUSTERS CONTAINING DIAZAHETEROCYCLES

The reactions of Os-3(CO)(11)(MeCN) with 1-vinylimidazole, imidazole and pyrazole (L-H) result in the formation of Os-3(CO)(11)(L-H) (1, L-H = 1-vinylimidazole; 2, L-H = imidazole; 3, L-H = pyrazole) in good yields. Thermolysis of these complexes at 98 degrees C gives two separable isomers of (mu-H)Os-3(CO)(10)(mu-L). In the case of 1 and 2, these isomers are farmed by the activation of the two C-H bonds adjacent to the imino nitrogen atom whereas for 3 they are formed by either a C-H or a N-H activation. These isomers interconvert at 128 degrees C. The reaction of Ru-3(CO)(12) with 1-vinyl-imidazole and imidazole in the presence of sodium benzophenone ketyl at 67 degrees C yields the cyclodimetallated compounds (mu-H)Ru-3(CO)(10)(mu-2, 3-eta(2)-C=NCH=CHNR) (7, R = CH=CH2; 8, R = H) in the same isomeric form as the minor isomers in the osmium series. All the new compounds are characterized by IR, H-1-NMR and elemental analysis together with the X-ray crystal structures of 2 and 7. Compound 2 crystallizes in the monoclinic space group P2(1)/c with unit cell parameters a = 12.081(2) Angstrom, b = 10.539(2) Angstrom, c = 15.834(2) Angstrom, beta = 102.61(2)degrees, V = 1959(1) Angstrom(3) and Z = 4. Least-squares refinement of 3570 reflections gave a final agreement factor of R = 0.0655 (R(w) = 0.0728). Compound 7 crystallizes in the monoclinic space group P2(1)/c with unit cell parameters a = 14.665(4) Angstrom, b = 7.5311(9) Angstrom, c = 18.291(4) Angstrom, beta = 96.14(1)degrees, V = 2008.5(7) Angstrom(3) and Z = 4. Least-squares refinement of 3042 reflections gave a final agreement factor of R = 0.0407 (R(w) = 0.0749).