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. 2008 Sep 11;112(36):8446-54.
doi: 10.1021/jp800125p. Epub 2008 Aug 15.

A computational characterization of boron-oxygen multiple bonding in HN=CH-CH=CH-NH-BO

Joseph D Larkin  1 , Krishna L Bhat, George D Markham, Tony D James, Bernard R Brooks, Charles W Bock
Affiliations

A computational characterization of boron-oxygen multiple bonding in HN=CH-CH=CH-NH-BO

Joseph D Larkin et al. J Phys Chem A. .

Abstract

Structures, relative energies, and bonding characteristics for various conformers of 3-imino-N-(oxoboryl)prop-1-en-1-amine, HN=CH-CH=CH-NH-BO, and the corresponding borocycle (-HN=CH-CH=CH-NH-B-)O are discussed using results from second-order Møller-Plesset (MP2) perturbation theory with the Dunning-Woon correlation-consistent cc-pVDZ, aug-cc-pVDZ, and cc-pVTZ basis sets. These MP2 results are compared to those from computationally efficient density functional theory (DFT) calculations using the LDA, PBE, TPSS, BLYP, B3LYP, BVP86, OLYP, O3LYP, and PBE1PBE functionals in conjunction with the economical Pople-type 6-311++G(d,p) basis set to evaluate the suitability of these DFT/6-311++G(d,p) levels for use with larger boron-containing systems. The effects of an aqueous environment were incorporated into the calculations using COSMO methodology. The calculated boron-oxygen bond lengths, orbital compositions, and bond orders in all the (acyclic) HN=CH-CH=CH-NH-BO conformers were consistent with the presence of a boron-oxygen triple bond, similar to that found in H-BO and H2N-BO. The (-HN=CH-CH=CH-NH-B-)O borocycle is predicted to be planar (C2v symmetry), and it is approximately 30 kcal/mol lower in energy than any of the (acyclic) HN=CH-CH=CH-NH-BO conformers; the boron-oxygen bond in this borocycle has significant double bond character, a bonding scheme for which there has been only one experimental structure reported in the literature (Vidovic, D. ; et al. J. Am. Chem. Soc. 2005, 127, 4566- 4569).

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Figures

Figure 1
Figure 1
Optimized structures of HBO, H2NBO and H2NB(OH)2. (Distances are in Å).
Figure 2
Figure 2
Optimized structures of the acyclic conformers 1a and 1b of NH=CH−CH=CH−NH−BO and the borocycle 1c (−NH=CH−CH=CH−NH−B−)O. (Distances are in Å). (AIM calculations using the MP2/cc-pVDZ density find the expected molecular graph for 1c (12 attractors, 12 critical points on attractor interaction lines, and 1 ring point.)
Figure 3
Figure 3
Optimized structures of the borocycle (−N(C6F5)=C(CH3)−CH=C(CH3)−N(C6F5)−B−)O and the acyclic conformer N(C6F5)=C(CH3)−CH=C(CH3)−N(C6F5)−BO at the MP2/cc-pVDZ computational level.
Scheme 1
Scheme 1
See this image and copyright information in PMC

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