E-H Bond Activation and Insertion Processes in the Reactions of the Unsaturated Hydride [W2Cp2(μ-H)(μ-PPh2)(NO)2].

The reactions of the title complex (1) with different p-block element (E) molecules was examined. Compound 1 reacted with BH3·THF at room temperature to give the trihydride [W2Cp2(μ-H)H2(μ-PPh2)(NO)2], which formally results from hydrogenation of 1, a reaction that actually does not take place when neat dihydrogen is used. Clean E-H bond oxidative addition, however, took place when 1 was reacted with HSnPh3, to give the related dihydride stannyl derivative [W2Cp2(μ-H)H(μ-PPh2)(NO)2(SnPh3)]. In contrast, the reaction of 1 with HSPh involved H2 elimination to give the thiolate-bridged complex [W2Cp2(μ-SPh)(μ-PPh2)(NO)2], while that with (p-tol)C(O)H resulted in insertion of the aldehyde to yield the related alkoxide complex [W2Cp2{μ-OCH2(p-tol)}(μ-PPh2)(NO)2]. Insertion also prevailed in the reactions of 1 with CNtBu, which, however, involved the competitive formation of new C-H or N-H bonds, to give a mixture of formimidoyl and aminocarbyne derivatives, [W2Cp2(μ-κ1:η2-HCNtBu)(μ-PPh2)(NO)2] (W-W = 3.0177(2) Å) and [W2Cp2{μ-C(NHtBu)}(μ-PPh2)(NO)2] (W-W = 2.9010(4) Å), respectively, even though the latter was thermodynamically preferred, according to density functional theory calculations. The former represents the first structurally characterized complex displaying a formimidoyl or iminoacyl ligand in the alkenyl-like μ-κ1:η2 coordination mode. The reaction of 1 with diazomethane proceeded with N2 elimination and C-H coupling to yield the agostic methyl-bridged complex [W2Cp2(μ-κ1:η2-CH3)(μ-PPh2)(NO)2] (calculated W-W = 2.923 Å), whereas the reaction with N2CH(SiMe3) proceeded with insertion of the diazoalkane to give the corresponding hydrazonide complex [W2Cp2{μ-NH(NCHSiMe3)}(μ-PPh2)(NO)2] (W-W = 2.8608(4) Å). The latter was converted under alkaline conditions to the methyldiazenide derivative [W2Cp2{μ-N(NMe)}(μ-PPh2)(NO)2] (W-W = 2.8730(2) Å), in a process involving hydrolysis of the C-Si bond coupled with a 1,3-H shift from N to C.