Halogen bonds link Lewis basic centers to electropositive halogens that act as Lewis acids. Such interactions can be considered as analogues of hydrogen bonds. It is a remarkable feature of metal hydride complexes that they form dihydrogen bonds to N-H and O-H donors, M-H...H-X. These dihydrogen bonds play an important role in reactivity. We now demonstrate that metal hydride complexes can form halogen bonds RFI...H-M and determine the energetics of binding by 1H NMR titrations [1]. The hydrides investigated are drawn from the isoelectronic series Cp2TaH3, Cp2WH2 and Cp2ReH, together with Cp2Ta(H)CO. The halogen bond donors are C6F5I and C6F13I. The enthalpy of interaction of C6F5I and Cp2TaH3 is -10.9 kJ/mol. Strikingly, the equilibrium constant for formation of this halogen-bonded complex is greater than that for the dihydrogen bonded complex indole...Cp2TaH3. The geometries of interaction are determined by DFT calculations.  [1] Smith D. A.; Brammer, L.; Hunter, C. A.; Perutz, R. N. J. Am. Chem. Soc. 2014  , 136, 1288.

Halogen bonds to transition metal hydride complexes

248th National Meeting (2014)

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