Issue 18, 2016

Homopolar dihydrogen bonding in ligand stabilized diberyllium hydride complexes, Be2(CH3)2H2L2 (L = H, CO, N-heterocyclic carbene and CN)

Abstract

The structure and bonding of diberyllium hydride complexes Be2(CH3)2H2L2, where L = H (2), CO (3), NHC (4) and CN (5) were studied in detail and compared with isostructural diborane (1). The bonding in Be2(CH3)2H2L2 was analyzed considering the interaction of two Be(CH3)L fragments with the bridging (μ-H)2 fragment. The geometrical and molecular orbital (MO) analyses indicate that the extent of back donation from Be→L (L = CO, NHC and CN) is less in Be2(CH3)2H2L2 as compared to that in Be(CH3)L fragments. The NBO, MO and QTAIM analyses indicate a significant charge concentration at the bridging (μ-H)2 in Be2(CH3)2H2L2, whereas charge depletion is observed at the (μ-H)2 fragment in diborane. The accumulation of electron density at the bridging (μ-H)2 is duly reflected in the detection of a (μ-H)−(μ-H) bond path in Be2(CH3)2H2L2, in spite of having longer (μ-H)−(μ-H) distances. The interaction between the bridging H-atoms in diberyllium hydride complexes can be considered as homopolar hydride–hydride dihydrogen bonding. The direction of the charge flow is from (μ-H)2 to BH2 in diborane, whereas from Be(CH3)L to (μ-H)2 in Be2(CH3)2H2L2. Hence, the bridging (μ-H)2 fragments in Be2(CH3)2H2L2 are electron rich as compared to the (μ-H)2 fragment in diborane. The experimental report of the ring opening of the ArNHC (Ar = 2,4,6-trimethylphenyl) ligand through hydride transfer from [Be(CH3)H(ArNHC)]2 corroborates well with the presence of electron rich bridging (μ-H)2 in diberyllium hydride complexes.

Graphical abstract: Homopolar dihydrogen bonding in ligand stabilized diberyllium hydride complexes, Be2(CH3)2H2L2 (L = H−, CO, N-heterocyclic carbene and CN−)

Supplementary files

Article information

Article type
Paper
Submitted
01 nov 2015
Accepted
19 mar 2016
First published
21 mar 2016

Dalton Trans., 2016,45, 7836-7846

Homopolar dihydrogen bonding in ligand stabilized diberyllium hydride complexes, Be2(CH3)2H2L2 (L = H, CO, N-heterocyclic carbene and CN)

K. Nijesh, S. De and P. Parameswaran, Dalton Trans., 2016, 45, 7836 DOI: 10.1039/C5DT04293C

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