Convergence of nuclear magnetic shieldings and one‐bond ^{11 J( 1111 B 11 H) indirect spin–spin coupling constants in small boron molecules}

摘要

> Self‐consistent field Hartree–Fock (SCF‐HF), density functional theory (B3LYP, KT1, KT2, and KT3), and coupled‐cluster calculations of the nuclear magnetic shielding constants of BH and BH ₃ molecules have been conducted to characterize the convergence of individual results obtained with correlation‐ and polarization‐consistent basis sets. The individual 11 B and 1 H NMR parameters were estimated in the complete basis set limit and compared with benchmark literature results. The SCF‐HF and density functional theory B3LYP predicted boron shieldings and shielding anisotropies of BH significantly differed from the results obtained by coupled‐cluster with single, double, and perturbative treatment of triple excitations, CCSD(T) approach. The best agreement between the CCSD(T)/complete basis set limit estimated boron shieldings was obtained for KT3 density functional (~5.7?ppm). The 1 H NMR parameters predicted at B3LYP and CCSD(T) levels of theory differed by less than 1?ppm, and the SCF‐HF calculated proton shieldings and shielding anisotropies also nicely agreed with our coupled‐cluster results. The 1 J( 11 B 1 H) parameters, calculated with B3LYP and KT3 functionals, accurately reproduced the earlier reported benchmark value for BH molecule. The SCF‐HF, B3LYP, and KT3 calculated boron shieldings of BH ₃ differed from the CCSD(T) values by 13.2, ?16.8, and ?2.1?ppm, respectively.