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 det ermination of the derivative with M = Mn, and R = Cy [2a, triclinic, s pace 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 coord inated 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 derivat ives 2a-d indicate that the central carbon of the S2CPR3 ligand shows a definite preference for attachment to cobalt rather than to manganes e or rhenium and that the reaction produces specifically the compounds with the carbon bonded to the cobalt atom. Although the reactions cou ld 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 st arting [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 complex es 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 determinati on 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 = 15.72 3(2) angstrom, alpha = 90.08(2)-degrees, beta = 102.46(4)-degrees, gam ma = 112.84(l)-degrees, Z = 2, R = 0.062, R(w) = 0.070] established th e existence of a direct Mo-Co bond, and the presence of the S2CPCY3 li gand bonded as eta2(S,S') chelate to Mo and as a eta3(S,C,S') pseudoal lyl 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, w hich indicates a definite preference of the central carbon to bind cob alt rather than molybdenum. In this case, the formal oxidation states are Mo(I) and CoO and the preference observed is consistent with our p revious observations, which can be rationalized assuming that the cent ral carbon Of S2CPR3 prefers to bind the metal atom with the lower oxi dation state. A common feature of the structures of 2a and 4a is the o ccurrence 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 is oelectronic to CPCO(CO)2. Some geometric parameters of the structures of 2a and 4a compare well with those in CpCo-(CO)2, suggesting that th ere is a close analogy between the two types of molecules.