Electronic communication through a poly-yne carbonyldicobalt complex containing an open linear triosmium cluster.

The oxidative coupling of 2-[Co(2)(CO)(4)(micro-X){micro(2)-eta(2)-(SiMe(3)C(2))}]-5-(C[triple bond]CH)C(4)H(2)S (X = dppa (1), dppm (2)) and 3-[Co(2)(CO)(4)(micro-dmpm){micro(2)-eta(2)-(SiMe(3)C(2))}]-4-(C[triple bond]CH)C(4)H(2)S (3) using standard Eglinton-Glaser conditions yielded 2,2'-Co(2)(CO)(4)(micro-X){micro(2)-eta(2)-(SiMe(3)C(2))}C(4)H(2)S-5,5'-(C[triple bond]C)(2) (X = dppa (4), dppm (5)) and 3,3'-Co(2)(CO)(4)(micro-dmpm){micro(2)-eta(2)-(SiMe(3)C(2))}C(4)H(2)S-4,4'-(C[triple bond]C)(2) (6), respectively (dppa = (Ph(2)P)(2)NH; dmpm = (Me(2)P)(2)CH(2); dppm = (Ph(2)P)(2)CH(2)). The reaction of 5 with [Os(3)(CO)(11)(CH(3)CN)] afforded 2,2'-Co(2)(CO)(4)(micro-dppm){micro(2)-eta(2)-(SiMe(3)C(2))}C(4)H(2)S-5,5'-[Os(3)(CO)(11)(micro(3)-eta(4)-(C[triple bond]C)(2)] (7), where the triosmium cluster is open and coordinated as a linear chain to both triple bonds. The electrochemical study of 7 shows that the "Os(3)" unit significantly enhances the electronic communication between the "Co(2)" redox centres as compared with 5. Complex 6 was characterized by single-crystal X-ray diffraction analyses.