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Reactions of Tungsten Acetylide–Silylene Complexes with Pyridines: Direct Observation of Silylene/Silyl Migration in Tungsten Acetylide and Carbyne/Vinylidene Frameworks

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posted on 2012-12-10, 00:00 authored by Hiroyuki Sakaba, Hiroyuki Oike, Yasuhiro Arai, Eunsang Kwon
Reaction of acetylide–silylene complex Cp*­(CO)2W­(SiPh2)­(CCtBu) (1a) with 4-(dimethylamino)­pyridine (DMAP) gave an equilibrium mixture of DMAP-stabilized silylene acetylide complexes trans- and cis-Cp*­(CO)2W­(SiPh2·DMAP)­(CCtBu) (trans-4 and cis-4). The corresponding reaction using Cp*­(CO)2W­(SiPh2)­(CCSiMe3) (2) produced the novel DMAP-coordinated silenylcarbyne/silylvinylidene complex Cp*­(CO)2W­[CC­(SiPh2·DMAP)­(SiMe3)] (6a) as a major product, which was equilibrated with trans- and cis-Cp*­(CO)2W­(SiPh2·DMAP)­(CCSiMe3) (trans-5a and cis-5a) via silylene/silyl migration. The novel structures of cis-4 and 6a were revealed by X-ray crystallography. A mixture of 2 and pyridine exhibited interesting temperature-dependent NMR spectral changes, indicating the formation of trans- and cis-Cp*­(CO)2W­(SiPh2·py)­(CCSiMe3) (trans-5b and cis-5b) and Cp*­(CO)2W­[CC­(SiPh2·py)­(SiMe3)] (6b) at low temperature, while a mixture of 1a and pyridine showed no such spectral changes.

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