Synthons for Coordinatively Unsaturated Complexes of Tungsten, and Their Use for the Synthesis of High Oxidation-State Silylene Complexes

Reduction of Cp*WCl4 afforded the metalated complex (η6-C5Me4CH2)(dmpe)W(H)Cl (1) (Cp* =
C5Me5, dmpe = 1,2-bis(dimethylphosphino)ethane). Reactions with CO and H2 suggested that 1 is in
equilibrium with the 16-electron species [Cp*(dmpe)WCl], and 1 was also shown to react with silanes
R2SiH2 (R2 = Ph2 and PhMe) to give the tungsten(IV) silyl complexes Cp*(dmpe)(H)(Cl)W(SiHR2) (6a, R2
= Ph2; 6b, R2 = PhMe). Abstraction of the chloride ligand in 1 with LiB(C6F5)4 gave a reactive species that
features a doubly metalated Cp* ligand, [(η7-C5Me3(CH2)2)(dmpe)W(H)2][B(C6F5)4] (4). In its reaction with
dinitrogen, 4 behaves as a synthon for the 14-electron fragment [Cp*(dmpe)W]+, to give the dinuclear
dinitrogen complex {[Cp*(dmpe)W]2(μ-N2)}{B(C6F5)4}2 (5). Hydrosilanes R2SiH2 (R2 = Ph2, PhMe, Me2,
Dipp(H); Dipp = 2,6-diisopropylphenyl) were shown to react with 4 in double Si−H bond activation reactions
to give the silylene complexes [Cp*(dmpe)H2WSiR2][B(C6F5)4] (8a−d). Compounds 8a,b (R2 = Ph2 and
PhMe, respectively) were also synthesized by abstraction of the chloride ligands from silyl complexes 6a,b.
Dimethylsilylene complex 8c was found to react with chloroalkanes RCl (R = Me, Et) to liberate
trialkylchlorosilanes RMe2SiCl. This reaction is discussed in the context of its relevance to the mechanism
of the direct synthesis for the industrial production of alkylchlorosilanes.