ALKYNYL-SUBSTITUTED CHLOROSILANES AS CLUSTER UNITS

The reaction of phenylethynyl-substituted chlorosilanes with dicobaltoctacarbonyl is discussed. Co2(CO)8 (II) yields selectively with (R)(PhC = C)Si(H)(Cl) (R = Me: I; R = C = CPh: V) (R)[(eta-2-C = CPh)Co2(CO)6]Si(H)(Cl) (R = Me: III; R = C = CPh: VI), in which the phenylethynyl group is eta-2 side-on co-ordinated to "Co2(CO)6". III affords with further Co2(CO)8 under oxidative addition (Me)[(eta-2-C = CPh)Co2(CO)6]Si(Cl)[Co(CO)4] (IV); IV may also be obtained directly by the reaction of I with 1.5 equivalents of II. VI contains a non-coordinated C = CPh group and yields with one equivalent of II the tetranuclear complex [(eta-2-C = CPh)Co2(CO)6]2Si(H)(Cl) (VII) in which the two C = CPh ligands form sterically-hindered carbon-cobalt tetrahedrane cluster units. Compounds VIII and X show the same reaction behaviour as I and V: (R)(PhC = C)Si(Cl)2 (R = Ph: VIII; R = H: X) reacts with one equivalent of II to yield in the first step (R)[(eta-2-C = CPh)Co2(CO)6]Si(Cl)2 (R = Ph: IX; R = H: XI). Addition of 0.5 parts of II to XI affords in high yields complex [Co(CO)4][eta-2-C = CPh)Co2(CO)6]Si(Cl)2 (XII). In a similar manner, compound (Me)(PhC = C)Si(H)2 (XIII) yields with one equivalent of II the dinuclear complex (Me)[(eta-2-C = CPh)Co2(CO)6]Si(H)2 (XIV) which slowly decompose to form oligomeric compounds as well as (eta-2-PhC = CH)Co2(CO)6 (XV). All new compounds were characterized by analytical and spectroscopic data (IR, H-1, C-13 NMR, MS), and (Me)[(eta-2-C = CPh)Co2(CO)6]Si(Cl)[Co(CO)4] (IV) by X-ray analysis.