title: 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(-) (), CO (), NHC () and CN(-) () were studied in detail and compared with isostructural diborane (). 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 (Ar)NHC (Ar = 2,4,6-trimethylphenyl) ligand through hydride transfer from [Be(CH3)H((Ar)NHC)]2 corroborates well with the presence of electron rich bridging (μ-H)2 in diberyllium hydride complexes.
authors.affiliation: Department of Chemistry, National Institute of Technology Calicut, Kozhikode, Kerala, 673 601 India. param@nitc.ac.in susmitade1980@gmail.com.
authors.forename: Karikkeeriyil
authors.initials: K
authors.lastname: Nijesh
authors.affiliation: Department of Chemistry, National Institute of Technology Calicut, Kozhikode, Kerala, 673 601 India. param@nitc.ac.in susmitade1980@gmail.com.
authors.forename: Susmita
authors.initials: S
authors.lastname: De
authors.affiliation: Department of Chemistry, National Institute of Technology Calicut, Kozhikode, Kerala, 673 601 India. param@nitc.ac.in susmitade1980@gmail.com.
authors.forename: Pattiyil
authors.initials: P
authors.lastname: Parameswaran