CARBONYLATION OF THE RU-ME BOND OF RU(ME)(I)(CO)2(IPR-N=CHCH=N-IPR) CATALYZED BY RU(CO)4(PR3), ZNCL2, AND H+

Reaction of the dimetallic compound Ru2(Me)(1)(CO)4(PR3)((i)Pr-DAB) ((i)Pr-DAB = (i)Pr-N=C(H)C-(H)=N-(i)Pr; PR3 = P(Bu(n))3 (2a), PMe2Ph (2b), PMePh2 (2c), PPh3 (2d), P(OMe)3 (2e), P(OPh)3 (2f)) with carbon monoxide afforded a mixture of the monomeric complexes Ru(R)(I)(CO)2((i)Pr-DAB) (R - Me (3); R = C(O)Me (4)) and Ru(CO)4(Pr3) (5a-f). It was found that with increasing basicity of the phosphine there is a stronger tendency to form the acetyl product 4, although 3 is formed initially for all phosphines used. Mechanistic studies showed that the conversion of 3 to 4 is catalyzed by RU(CO)4(PR3), provided PR3 is sufficiently basic. The use of (CO)-C-13-enriched Ru(CO)4(PR3) led to the incorporation of (CO)-C-13 into bo the acetyl CO group and the terminal CO groups of 4, indicating the presence of a dimetallic in-termediate, by which intermetallic CO exchange becomes possible. Further evidence for this was obtained from the observation that the conversion of 3 to 4 can also be effected in the absence of free CO, by reaction of 3 with Ru(CO)4(PMe2Ph) (5b) and L' (L' = PPh3, P(OPh)3). In addition to 4 the complex Ru(CO)3-(PMe2Ph)(L') is also formed under these conditions. Interestingly, reaction of 3 with Sb in the absence of both CO and L' also gave carbonylation of the Ru-Me bond, which, however, was accompanied by transfer of a H-atom from an (i)Pr-CH group to an imine C-atom, with formation of Ru(C(O)Me)(I)(CO)2((i)Pr-N=CH-CH2-N=C(Me)2) (7). Reaction of 3 with AgOTF yielded [Ru(Me)(CO)2((i)Pr-DAB)][OTF] (8), which in the presence of CO is rapidly converted to [Ru(C(O)Me)(CO)2((i)Pr-DAB)][OTF] (9), whereas 8 with (t)Bu isocyanide and PMe2Ph PVe [RU(Me)(CO)2(L)((i)Pr-DAB)][OTF] (L = (t)Bu-NC (10), PMe2Ph (11)). Attempts to carbonylate the Ru-Me bond in complexes 10 and 11 were not successful. Finally it was shown that the carbonylation of the Ru-Me bond of 3 could also be promoted by H+ and ZnCl2. Single-crystal X-ray structure determinations of complexes 4 and 8 have been carried out, and their molecular structures are discussed. Salient features are that 4 has a configuration similar to that of 3; i.e., the acetyl group is trans to 1. The trifluorosulfonate anion in 8 is found to be eta1-coordinated to the ruthenium center and trans to the methyl group. Crystals of 4 (C12H19N2O3RuI) are monoclinic, space group P2(1)/n, with a = 8.556 (1) angstrom, b = 18.510 (2) angstrom, c = 10.500 (1) angstrom, beta = 94.90 (1)-degrees, V = 1656.7 (3) angstrom3, Z = 4, and final R = 0.0435 for 2565 reflections with I > 2.5sigma(I) and 188 parameters. Crystals of 8 (C12H19F3N2O5RuS) are monodinic, space group P2,/c, with a = 8.288 (1) angstrom, b = 25.839 (2) angstrom, c = 17.994 (1) angstrom, beta = 100.47 (1)-degrees, V = 3789.1 (6) angstrom3, Z = 8, and final R = 0.0476 for 3917 reflections with I > 2.5 sigma(I) and 500 parameters.