A Hypervalent Pentacoordinate Boron Compound with an N−B−N Three-Center Four-Electron Bond

Abstract

For the purpose of synthesizing and characterizing hypervalent boron compounds with strong hypervalent interaction, we have prepared a boron compound with a tridentate ligand bearing two pyrimidine rings as nitrogen donors. X-ray analysis and molecular orbital calculations suggested that the boron compound was of hypervalent pentacoordinate structure with an N-B-N hypervalent bond. Thus, we have prepared the first hypervalent second row element compound with apical N coordination. A breakdown of energy contributions by DFT calculations revealed that the N-B-N bond energy of the pentacoordinate state ground state (13) was 2.8 kcal mol(-1). Implications were that the conjugation energy difference of 6.6 kcal mol(-1) (14.2-7.6 kcal mol(-1)) with the tetracoordinate state was a crucial factor for shifting stability toward the pentacoordinate structure.

Correlation among the Gas-Phase, Solution, and Solid-Phase Geometrical and NMR Parameters of Dative Bonds in the Pentacoordinate Silicon Compounds. 1-Substituted Silatranes

“…The structure of molecules 1a – c was studied using the resource-intensive high-level coupled-cluster singles and doubles (CCSD) approach in conjunction with the 6-31G(d) and 6-311G(d,p) basis sets and the MP2 method with the 6-311G(2d,p), 6-311G(d,p), 6-311++G(d,p), and cc-pvTZ basis sets. In addition, we invoked three density functional methods with the 6-31G(d), 6-311G(d,p), and 6-311++G(d,p) basis sets: one-parameter hybrid-GGA exchange-correlation functional PBE0, hybrid GGA functional B3PW91, having recommended itself well for studying nonclassical structures, and new generation hybrid meta-GGA functional M06-2X . The correspondence of the DFT and MP2 optimized structures to the minima on the potential energy surface (PES) was confirmed by the positive eigenvalues of the corresponding Hessians.…”

A Pentacoordinate Boron-Containing π-Electron System with Cl–B–Cl Three-Center Four-Electron Bonds

“…5 In contrast, organoboron compounds with pentacoordination are still limited to only a few examples, as the second-row boron atom with its small size preferentially forms tetracoordinate species upon interaction with inter-or intramolecular coordinating groups. 6 In 1984, Martin's group succeeded in the synthesis of 1 as the first example of a pentacoordinate organoboron compound. 7 The vacant p orbital of its boron atom interacts with two sets of alkoxylate lone-pair electrons at the axial positions of the TBP geometry.…”

Radical anions of hypervalent silicon compounds: 1-substituted silatranes

“…23,24 Effects of potassium ions on the structure of 1 À were also examined. It is worth noting that the hybrid GGA functional B3PW91 20,21 has recommended itself well for studying the intramolecular complexes of hypervalent compounds, [25][26][27][28] including silatranes. 29 The correspondence of the optimized structures to the minima on the potential energy surface (PES) was confirmed by the positive eigenvalues of the corresponding Hessians.…”