Metal-carbon multiple bonds: [2 + 2] cycloaddition of nitrilium salts across a metal-carbon triple bond; synthesis and structure of iminocarbene complexes of tungsten

Abstract

The aminocarbyne complex Cp ∗( CO) 2 W≡ CNEt 2 ( Cp ∗ = C 5 Me 5) ( 1) undergoes a selective [2 + 2] cycloaddition reaction with the nitrilium salt [MeC≡NMe]B 4 to afford the iminocarbene complex [ Cp ∗( CO) 2 W{ = C( NEt 2) C( Me) = NMe}] BF 4 ( 2). Alternatively, the analogous iminocarbene complexes [ Cp ∗( CO) 2 W{ = C( NMe 2) C( Me) = NEt}] BF 4 ( 5: M = Mo; 6: M = W ) can be obtained by methylation of the η 2-1,4-diaza-3-methylbutadien-2-yl complexes Cp ∗( CO) 2 M[ C( NMe) C( Me) NEt] ( 3: M = Mo; 4: M = W ) with [Me 3O]BF 4. The solid-state structure of 2 suggests the presence of an η 3-bonded iminocarbene ligand and reveals a close electronic relationship between 2, 5 and 6 and Mo II or W II η 3-vinylcarbene complexes.