Synthesis and Characterization of 5-Coordinate Tungsten Hydride Anions: [(tBu3SiNH)(tBu3SiN=)2HWR]M

Treatment of (^tBu₃SiNH)(^tBu₃SiN=)₂WH ( 1 -H) with small alkyl anions (RM) afforded tungsten alkyl hydride anions (^tBu₃SiNH)(^tBu₃SiN=)₂HWR)]M ( 3 -(R)M: R=CH₃, M=Li; R=ⁿBu, M=Li; R=^neoPe, M=Li; R=CH₂Ph (Bn), M=K (two isomers); R=CCH, M=Na; R=CH=CH₂ (Vy), M=Li). The saturated alkyl anions 3 -(R)M ( 3 -(R)M: R=CH₃, M=Li; R=ⁿBu, M=Li; R=^neoPe, M=Li; R=CH₂Ph (Bn), M=K) degraded via apparent 1,2-RH-elimination to produce the known (^tBu₃SiN=)₃WH]M ( 2 -HM), but the acetylide ( 3 -(C₂H)Na) and vinyl ( 3 -(Vy)Li) anions converted to their hydrogenated isomers, (^tBu₃SiN=)₃WVy]Na ( 2 -VyNa) and (^tBu₃SiN=)₃WEt]Li ( 2 -EtLi), respectively. The structure of 3 -(ⁿBu)Li is reported, and a discussion of tungsten-hydride coupling constants in ^tBu₃SiX-ligated (X=O, NH, N) systems is given.