• Kabir, Shariff E.
• Al-Mamun, Md Rafique
• Ghosh, Shishir
• Hogarth, Graeme

Abstract

The reactivity of 2-vinylpyrazine and 2-vinylpyridine at different triosmium clusters has been investigated. Room temperature reaction of 2-vinylpyrazine with formally unsaturated [Os3(CO)10(μ-H)2] or lightly-stabilized [Os3(CO)10(NCMe)2] leads to the formation of [HOs3(CO)10(μ-C4H3N2CH=CH)] (1) through β-vinyl C─H bond activation. In contrast, direct reaction between [Os3(CO)12] and 2-vinylpyrazine at elevated temperatures affords [Os3(CO)10(μ-C4H2N2CH=CH2)(μ-H)] (2) via aryl C─H bond activation. The metalated 2-vinylpyrazine ligand acts as a five-electron donor in 1, but serves as a three electron donor in 2. The high temperature reaction between 2-vinylpyrazine with the bis(diphenylphsophino)methane (dppm) substituted cluster [Os3(CO)8(μ-H)2(μ-dppm)] furnishes [Os3(CO)8(μ-C4H3N2CH=CH){μ-Ph2PCH2P(Ph)C6H4}] (3) and [Os3(CO)6(η2-C4H3N2CH=CH2)(μ3-C4H3N2CH=C)(μ-dppm)] (4) through single and double β-vinyl C─H bond activation, respectively. The metalated 2-vinylpyrazine ligand acts as five- and six-electron donors in 4 and 5, respectively. Cluster 5 also contains an intact 2-vinylpyrazine ligand coordinating to an osmium like an olefin using the vinylic double bond thus serving as a two-electron donor. A similar reaction between [Os3(CO)8(μ-H)2(μ-dppm)] and 2-vinylpyridine affords the analogous [Os3(CO)8(μ-C5H4NCH=CH){μ-Ph2PCH2P(Ph)C6H4}] (5) and [Os3(CO)6(η2-C5H4NCH=CH2)(μ3-C5H4NCH=C)(μ-dppm)] (6). The solid-state molecular structures of 1–6 have been determined by single crystal X-ray diffraction analysis.

Topics

• single crystal X-ray diffraction
• cluster
• single crystal
• activation
• molecular structure
• Osmium