UNUSUAL REACTIVITIES OF (MU-ETA-2-ETA-2-FP-C-EQUIVALENT-TO-C-H)CO2(CO)6, THE ADDUCTS OF FP-C-EQUIVALENT-TO-C-H TO CO2(CO)8 - PHOTOLYSIS, THERMOLYSIS AND REDUCTION WITH HYDROSILANES GIVING POLYNUCLEAR COMPLEXES, (CP)2FE2CO3(MU-5-C=CH)(CO)10, (MU-CH=CH)[(-MU-3-C)CO3(CO)9]2 AND CPFECO3(MU-C=CH2)(CO)9

The properties and reactivities of (mu-eta2:eta2-FP-C=C-H)Co2(CO)6 (3) [the FP-C=C-H adducts to Co2(CO)8: 3a (FP = Fp), 3b (FP = Fp*)] have been compared with those of alkyne adducts (mu-eta2:eta2-R-C=C-R)Co2(CO)6 and the Ph analogue (mu-eta2:eta2-Fp-C=C-Ph)Co2(CO)6 (5). Compound 3 has been shown to serve as a.building block for polynuclear complexes. (CO)-C-13-labelling experiments on 3a and 5 have revealed an intramolecular exchange between the Fe-CO and Co-CO ligands. Photolysis of 3a, b produces pentanuclear clusters (CP)2Fe2Co3(mu5-C-CH)(CO)10 (11a,b), respectively, via an apparent addition reaction of a (CP)FeCo(CO)n fragment to 3. On the other hand, thermolysis of 3a gives the Fe-free hexacobalt cluster compound (mu-CH=CH)-[(-mu3-C)Co3(CO)9]2 (13) which consists of two alkylidyne tricobalt units linked by the CH=CH bridge, whereas 3b is thermolyzed to give the Fe-Co dimer without the C2H ligand, Cp*Fe(CO)(mu-CO)2Co(CO)3 (14), in addition to the photolysis product 11b. Reduction of 3 with hydrosilanes gives a mixture containing 1,2-disilylethylene (16) and the tetranuclear mu-vinylidene cluster CpFeCo3(mu4-C=CH2)(CO)9 (12) formally by way of hydrosilylation and hydrometallation (with a HCo(CO)n species) of the C2H ligand, respectively. In the case of the Pauson-Khand reaction and catalytic cyclotrimerization 3a exhibits reactivities similar to alkyne adducts to give the tricyclic cyclopentenone derivatives 18 (from norbornene and norbornadiene) and triphenylbenzenes, respectively.