Unexpected differential sensitivity of nuclear spin–spin-coupling constants to bond stretching in BH4−, NH4+, and SiH4

摘要: Correlated ab initio calculations are reported, which show that stretching one of the Si–H bonds in silane from its equilibrium value increases one-bond coupling J(Si, H) other three by more than increase stretched bond. This “unexpected differential sensitivity” is considerably greater terms reduced constants same effect discovered previously methane. UDS also found to occur BH4− and NH4+ ions comes overwhelmingly Fermi contact term. For proton–proton due stretch a single bond, earlier methane, occurs NH4+, just fails appear absent BH4−. The origins signs constant derivatives discussed.