Alkane Binding Implicated in Reactions of ( t Bu 3 SiN═) 3 WHK and Alkyl Halides

The reduction of alkyl, benzyl, allyl, and propargyl halides by [((Bu3SiN)-Bu-t=)(3)WH]K (2-H-M) was assayed via analysis of the product distributions. For unhindered sp(3) substrates (MeX, EtX, BnX, CH2=CHCH2X, RCCCH2X, etc.), the observed products were RH loss and [((Bu3SiN)-Bu-t=)(3)WX]M (2-X-M) or MX elimination and ((Bu3SiNH)-Bu-t)((Bu3SiN)-Bu-t=)(2)WR (1-R), which was derived from 1,2-RH-addition to an imide of the intermediate alkane (arene) complex ((Bu3SiN)-Bu-t=)(3)W(RH) (2-RH). Solvent activation or binding was also seen, consistent with the trapping of (tBu3SiN=)3W (2) generated from RH loss from 2-RH. The radical clocks (PrCH2Br)-Pr-c and 5-hexenyl bromide yielded the unrearranged products ((Bu3SiNH)-Bu-t)((Bu3SiN)-Bu-t=)(2)W(trans-(c)(CHCH2CHMe)) (1-(PrMe)-Pr-c) and ((Bu3SiNH)-Bu-t)((Bu3SiN)-Bu-t=)(2)W(trans-CH=(CHBu)-Bu-n) (1-CH=(CHBu)-Bu-n), respectively. When hindered sp(3) substrates were employed, halogenated products [((Bu3SiN)-Bu-t=)(3)WX]M (2-X-M) and ((Bu3SiNH)-Bu-t)((Bu3SiN)-Bu-t=)(2)WX (1-X) were prominent, suggesting that radical paths were operable. KlEs derived from product ratios involving CD3I or CD3CH2I and 2-H-K supported the intermediacies of ((Bu3SiN)-Bu-t=)(3)W(CHD3) (2-CHD3) and ((Bu3SiN)-Bu-t=)(3)W(CH3CD3) (2-CH3CD3), respectively. X-ray crystal structures of ((Bu3SiNH)-Bu-t)(tBu3SiN=)(2)WR (1-R; R = Me, (PrMe)-Pr-c, CH=C=CH2) are presented, and the results are placed in the context of 1,2-RH-addition to d(0) early-transition-metal imido species.