Unusual reactivities of (μ-η 2:η 2-FPCCH)Co 2(CO) 6, the adducts of FPCCH to Co 2(CO) 8: photolysis, thermolysis and reduction with hydrosilanes giving polynuclear complexes, (CP) 2Fe 2Co 3(μ 5-CCH)(CO) 10, (μ-CHCH)[(−μ 3-C)Co 3(CO) 9] 2 and CpFeCo 3(μ-CCH 2)(CO) 9

Abstract

The properties and reactivities of (μ-η 2:η 2-FPCCH)Co 2(CO) 6, ( 3) [the FPCCH adducts to Co 2(CO) 8: 3a (FP  Fp), 3b (FP  Fp★)] have been compared with those of alkyne adducts (μ-η 2:η 2-RCCR)Co 2(CO) 6 and the Ph analogue (μ-η 2:η 2-FpCCPh)Co 2(CO) 6 ( 5). Compound 3 has been shown to serve as a building block for polynuclear complexes. 13CO-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) 2Fe 2CO 3(μ 5-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 (μ-CHCH)-[(-μ 3-C)Co 3(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 C 2H ligand, Cp★Fe(CO)(μ-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 μ-vinylidene cluster CpFeCo 3(μ 4-CCH 2)(CO) 9 ( 12) formally by way of hydrosilylation and hydrometallation (with a HCo(CO) n species) of the C 2H 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.