title: B-H···π Interaction: A New Type of Nonclassical Hydrogen Bonding.
abstract: For the first time, nonclassical hydrogen (H)-bonding involving a B-H···π interaction is described utilizing both quantum chemical predictions and experimental realization. In the gas phase, a B-H···π H-bond is observed in either B2H6···benzene (ΔE = -5.07 kcal/mol) or carborane···benzene (ΔE = -3.94 kcal/mol) complex at reduced temperatures. Ir-dimercapto-carborane complexes [Cp*Ir(S2C2B10H10)] are designed to react with phosphines PR3 (R = C6H4X, X = H, F, OMe) to give [Cp*Ir(PR3)S2C2B10H10] for an investigation of B-H···π interactions at ambient temperatures. X-ray diffraction studies reveal that the interaction between the carborane BH bonds and the phosphine aryl substituents involves a BH···π H-bond (H···π distance: 2.40-2.76 Å). (1)H NMR experiments reveal that B-H···π interactions exist in solution according to measured (1)H{(11)B} signals at ambient temperatures in the range 0.0 ≤ δ ≤ 0.3 ppm. These are high-field shifted by more than 1.5 ppm relative to the (1)H{(11)B} signals obtained for the PMe3 analog without B-H···π bonding. Quantum chemical calculations suggest that the interaction is electrostatic and the local (B)H···ring stretching force constant is as large as the H-bond stretching force constant in the water dimer.
authors.affiliation: State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing, Jiangsu 210093, China.
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing, Jiangsu 210093, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing, Jiangsu 210093, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yan
authors.affiliation: Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University , Dallas, Texas 75275-0314, United States.
authors.forename: Wenli
authors.initials: W
authors.lastname: Zou
authors.affiliation: Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University , Dallas, Texas 75275-0314, United States.
authors.forename: Dieter
authors.initials: D
authors.lastname: Cremer