A predicted new type of directional noncovalent interaction

The electrostatic potentials computed on the surfaces of a series of molecules RX, where X is a Group V atom, show that some of these atoms have regions of positive potential on their outer surfaces, approximately on the extensions of the R-X bonds. This suggests the likelihood of weak, directional noncovalent interactions between such atoms and nucleophiles, paralleling what has already been established for Groups VI and VII. The origins and relative strengths of the positive regions are explained in terms of the sigma-hole concept, supported by natural bond orbital analyses. MP2/6-311++G(3df,2p) calculations confirm the formation of stable complexes between five such Group V molecules and the model nucleophile HCN. (c) 2007 Wiley Periodicals, Inc.