Synthesis and electrochemical study of cobalt carbonyl complexes of trimethylsilyl-substituted 1,3,5-triethynylbenzene

Treatment of 1,3,5-tris(trimethylsilylethynyl)benzene or 1,3,5-triethynylbenzene with Co2(CO)8 or Co2(CO)6(dppm) produced the formation of substituted ethynylcobalt complexes with one, two or three Co2(CO)6 or Co2(CO)4(dppm) units, [{X3(Co2(CO)6)C2}n(XCC)m(1,3,5-C6H3)] (X=H or SiMe3) (n=1, 2 or 3; m=3−n) and [{SiMe3(Co2(CO)4dppm)C2}n(SiMe3CC)m(1,3,5-C6H3)] (n=1 or 2; m=3−n), in a high yield. Desilylation of the non-metallated alkynes in [{SiMe3(Co2(CO)4dppm)C2}(SiMe3CC)2(1,3,5-C6H3)] occurred on treatment with KOH. Electrochemical results provide evidence for communication between the C2Co2 centres. Crystals of [{SiMe3(Co2(CO)4dppm)C2}2(SiMe3CC)(1,3,5-C6H3)] suitable for single-crystal X-ray diffraction were grown and the molecular structure of this compound is discussed.