Silicon Tetrahydroborate and Silylene Dihydroborate with Interelement B–H–Si and BSi Bonds

Reactions
of laser-ablated boron atoms with SiH4 molecules
gave silylene dihydroborate (H2BSiH2) in excess
argon, which rearranged to silicon tetrahydroborate [Si­(μ-H)2BH2] upon 300–350 nm irradiation. These
reaction products were identified by functional group infrared frequencies,
isotopic shifts, and comparison to infrared frequencies calculated
by using density functional theory. It is found that H2BSiH2 has planar doublet ground state with electron-deficient
B–Si double-bond character. Bonding analysis for Si­(μ-H)2BH2 shows that 3c–2e B–H–Si
bond is formed by accepting electrons donated from B–H σ
bond.

激光烧蚀硼原子与硅烷（SiH4）分子在过量氩气环境中发生反应，生成亚甲硅基二氢硼酸酯（silylene dihydroborate，H2BSiH2）；该产物经300~350 nm辐照后，会重排为四氢硼酸硅[Si(μ-H)2BH2]。通过官能团特征红外频率、同位素位移以及与密度泛函理论（density functional theory）计算得到的红外频率进行比对，对上述反应产物进行了鉴定表征。研究发现，H2BSiH2具有平面型二重态基态，且呈现缺电子B-Si双键特征。对Si(μ-H)2BH2的成键分析表明，其3中心2电子（3c–2e）B-H-Si键是通过接受B-H σ键所提供的电子而形成的。