Different inertness of titanocene [Cp2Ti] and decamethyltitanocene [Cp*2Ti] in reactions with N,N-bis(trimethylsilyl)sulfurdiimide - Elimination of tetramethylfulvene and formation of half-titanocene complexes

Abstract

The reaction of the titanocene alkyne complex [Cp* 2Ti(η2-Me3SiC2SiMe3)] (1) (Cp* = η5-pentamethylcyclopentadienyl) with N,N-bis(trimethylsilyl)sulfurdiimide (2) results in the formation of 1,2,3,4-tetramethylfulvene (3) as well as three titanium complexes 4, 5 and 6. During the reaction, formal elimination of one Cp* ligand induces a series of C-H and N-S bond activation steps, thus yielding the products. The molecular structures of complex 5 and of the free fulvene were determined by X-ray crystallographic analysis. Evidently, in these reactions [Cp* 2Ti] is less stable than [Cp2Ti]; a possible reason was found to be the well-known intramolecular C-H activation yielding the tautomeric tetramethylfulvene hydride species, from which 1,2,3,4-tetramethylfulvene (3) can dissociate. Reaction of decamethyltitanocene complex [Cp* 2Ti(η2-Me3SiC2SiMe3)] with N,N-bis(trimethylsilyl)sulfurdiimide results in the formation of three titanium complexes as well as 1,2,3,4-tetramethylfulvene (3) as the organic byproduct. The molecular structures of metallacyclic half-sandwich titanium complex 5 and - most remarkably - of free 3 (co-crystallised with Me 3SiC2SiMe3) were determined by X-ray crystallographic analysis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.