Intramolecular Cyclization of Butadiyne Functionalized Ligands coordinated to Triosmium‐Carbonyl Cluster

Reactions between diynes and [Os 3 (CO) 11 (CH 3 CN)] in the presence of water give rise to the formation of intriguing hydride triosmium clusters [Os 3 (μ‐H)(CO) 9 {μ 3 ,η 1 :η 3 :η 1 ‐ R C 2 COHC≡C R }] ( 1a – 1c ) under mild conditions in high yields. When these allylic alcohol compounds 1a – 1c are dissolved in dry polar and donor solvents, an intramolecular cyclization process takes place to give [Os 3 (μ‐H)(CO) 9 {μ 3 ,η 1 :η 3 :η 1 ‐ R C 2 CH=COC R }] ( 2a – 2c ) in quantitative yield. The utilization of [Os 3 (CO) 11 (CH 3 CN)] as starting material together with the addition of water can replace the inconvenient use of [Os 3 (μ‐H) 2 (CO) 10 ]. This method of synthesis provides a facile pathway for diyne cyclizations and has a clear advantage over those described to date in the literature. Additionally, the analogous cyclized mixed‐metal complex [Os 3 (μ‐H)(CO) 9 {μ 3 ,η 1 :η 3 :η 1 ‐FcC 2 CH=COCFc}] ( 2d ) (Fc = ferrocenyl), was synthesized in order to carry out a comparative electrochemical study with the related compounds [Os 3 (CO) 11 (μ 3 ‐FcC 4 Fc)] ( I ) and [Os 3 (CO) 10 (μ 3 ‐FcC 4 Fc)] ( II ), which were previously reported by R. D. Adams .