HETERODINUCLEAR COMPLEXES CONTAINING S2CPR3 AS ASYMMETRIC BRIDGES BETWEEN COBALT AND METALS OF GROUP-7 (MANGANESE, RHENIUM) OR GROUP-6 (MOLYBDENUM, TUNGSTEN) - SELECTIVE COBALT CARBON BOND FORMATION - X-RAY STRUCTURES OF [MNCO(CO)5(MU-SU2CPCY3)] AND [MOCO(ETA(3)-C3H5)(CO)4(MU-S2CPCY3)].CH2CL2

The reaction of [M(CO)3(S2CPR3)Br] (M = Mn, Re) with CO2(CO)8 produces the heterobinuclear complexes [MCo(CO)5(mu-S2CPR3)] (2). An X-ray determination of the derivative with M = Mn, and R = Cy [2a, triclinic, space group P1BAR, a = 11.074(3) angstrom, b = 11.156(3) angstrom, c = ll.769(3) angstrom, alpha = 74.64(l)-degrees, beta = 35.36(l)-degrees, gamma = 83.44(2)-degrees, Z = 2, R = 0.042, R(w) = 0.043] showed the formation of a Mn-Co bond, and the presence of the S2CPR3 ligand coordinated as a eta2(S,S') chelate to Mn and as a eta3(S,C,S') pseudoallyl to Co. The structure of 2a, and the spectroscopic data of all derivatives 2a-d indicate that the central carbon of the S2CPR3 ligand shows a definite preference for attachment to cobalt rather than to manganese or rhenium and that the reaction produces specifically the compounds with the carbon bonded to the cobalt atom. Although the reactions could be considered as involving the disproportionation of CO2(CO)8 into Co(-I) and Co(II), it is noticeable that the direct reaction of the starting [M(CO)3(S2CPR3)Br] with CO(CO)4- gives complexes 2 only for M = Re, but not for M = Mn. The method can be extended to prepare complexes containing Mo-Co and W-Co bonds. ThUS, Co2(CO)8 reacts with [M(eta3-C3H5)(CO)2(S2-CPR3)Br] (3; M = Mo, W) to produce [MCo(eta3-C3H5)(CO)4(mu-S2CPR3)] (4a-d) in moderate yields; An X-ray structure determination of the derivative with M = Mo, R = Cy [4a-CH2Cl2, triclinic, space group P1BAR, a = 10.301(1) angstrom, b = 11.347(7) angstrom, c = 15.723(2) angstrom, alpha = 90.08(2)-degrees, beta = 102.46(4)-degrees, gamma = 112.84(l)-degrees, Z = 2, R = 0.062, R(w) = 0.070] established the existence of a direct Mo-Co bond, and the presence of the S2CPCY3 ligand bonded as eta2(S,S') chelate to Mo and as a eta3(S,C,S') pseudoallyl to Co, in the same fashion observed for the structure of the Mn-Co derivative 2a. Again there is a selective formation of a C-Co bond, which indicates a definite preference of the central carbon to bind cobalt rather than molybdenum. In this case, the formal oxidation states are Mo(I) and CoO and the preference observed is consistent with our previous observations, which can be rationalized assuming that the central carbon Of S2CPR3 prefers to bind the metal atom with the lower oxidation state. A common feature of the structures of 2a and 4a is the occurrence of a CO(CO)2 fragment which is bonded to a MSCS' ring which donates formally 5 e. In this sense, the molecules of 2a and 4a are isoelectronic to CPCO(CO)2. Some geometric parameters of the structures of 2a and 4a compare well with those in CpCo-(CO)2, suggesting that there is a close analogy between the two types of molecules.