Reactions of Sn(Si(^sup t^Bu)^sub 2^Me)^sub 3^ with HM(CO)^sub 3^C^sub 5^R^sub 5^ (M = Cr or Mo, R = H or CH3) and Hg. Ionic, covalent, and µ-CO bonding patterns between transition metals and tin

Hydrogen atom transfer (HAT) reactions to the planar triorganotin radical ∙Sn(Si(tBu)2Me)3 from HMo(CO)3C5H5 and HCr(CO)3C5R5 (R = H, Me) have been investigated at room temperature in toluene or pentane solution. ∙Sn(Si(tBu)2Me)3 and HMo(CO)3C5H5 react rapidly to yield the previously unreported tin hydride HSn(Si(tBu)2Me)3 and [Sn(Si(tBu)2Me)3]+[Mo(CO)3C5H5]−. Similarly, ∙Sn(Si(tBu)2Me)3 and HCr(CO)3C5H5 react at a slower rate to produce HSn(Si(tBu)2Me)3 and a complex formulated as Cp(CO)2Cr-C=O-Sn(Si(tBu)2Me)3 based on its solubility in toluene, infrared spectrum, and computational studies. A product with identical spectroscopic properties to the proposed Cp(CO)2Cr-C=O-Sn(Si(tBu)2Me)3 is obtained rapidly in the reaction of ∙Sn(Si(tBu)2Me)3 and [Cr(CO)3C5H5]2. Reaction of ∙Sn(Si(tBu)2Me)3 and HCr(CO)3C5Me5 does not occur at a significant rate at room temperature nor does reaction of ∙Cr(CO)3C5Me5 and HSn(Si(tBu)2Me)3. Fast exchange between HCr(CO)3C5H5 and [Cr(CO)3C5H5]2 results in a single broad peak in the cyclopentadienyl area for mixtures of these two complexes in toluene-d8 at room temperature implying that Cr–Cr bond cleavage and also hydrogen atom transfer (HAT) are faster than the NMR time scale. Computational studies accurately reflect experimental observations. The computed Sn–H bond dissociation enthalpy (BDE) of only 66.7 kcal/mol in HSn(Si(tBu)2Me)3 places it near the values for M-H BDE in HM(CO)3C5H5 (M = Cr, Mo) leading to a near equilibrium situation with respect to HAT. Reaction of ∙Sn(Si(tBu)2Me)3 and elemental Hg forms the linear trinuclear HgSn2 cluster Hg[Sn(Si(tBu)2Me)3]2. The crystal structures of Hg[Sn(Si(tBu)2Me)3]2 and BrSn(Si(tBu)2Me)3 are reported.