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

Abstract

The oxidative coupling of 2-[Co₂(CO)₄(μ-X){μ₂-η²-(SiMe₃C₂)}]-5-(CCH)C₄H₂S (X = dppa (1), dppm (2)) and 3-[Co₂(CO)₄(μ-dmpm){μ₂-η²-(SiMe₃C₂)}]-4-(CCH)C₄H₂S (3) using standard Eglinton-Glaser conditions yielded 2,2′-[Co₂(CO)₄(μ-X){μ₂-η²-(SiMe₃C₂)}C₄H₂S]₂-5,5′-(CC)₂ (X = dppa (4), dppm (5)) and 3,3′-[Co₂(CO)₄(μ-dmpm){μ₂-η²-(SiMe₃C₂)}C₄H₂S]₂-4,4′-(CC)₂ (6), respectively (dppa = (Ph₂P)₂NH; dmpm = (Me₂P)₂CH₂; dppm = (Ph₂P)₂CH₂). The reaction of 5 with [Os₃(CO)₁₁(CH₃CN)] afforded 2,2′-[Co₂(CO)₄(μ-dppm){μ₂-η²-(SiMe₃C₂)}C₄H₂S]₂-5,5′-[Os₃(CO)₁₁(μ₃-η⁴-(CC)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 “Os₃” unit significantly enhances the electronic communication between the “Co₂” redox centres as compared with 5. Complex 6 was characterized by single-crystal X-ray diffraction analyses.