Abstract
Recent discovery of an unusual bond between Na and B in NaBH(3)(-) motivated us to look for potentially similar bonds, which remained unnoticed among systems isoelectronic with NaBH(3)(-). Here, we report a novel family of collective interactions and a measure called exchange-correlation interaction collectivity index (ICI(XC); [Formula: see text]) to characterize the extent of collective versus pairwise bonding. Unlike conventional bonds in which ICI(XC) remains close to one, in collective interactions ICI(XC) may approach zero. We show that collective interactions are commonplace among widely used organometallics, as well as among boron and aluminum complexes with the general formula [M(a+)AR(3)](b-) (A: C, B or Al). In these species, the metal atom interacts more efficiently with the substituents (R) on the central atoms than the central atoms (A) upon forming efficient collective interactions. Furthermore, collective interactions were also found among fluorine atoms of XF(n) systems (X: B or C). Some of organolithium and organomagnesium species have the lowest ICI(XC) among the more than 100 studied systems revealing the fact that collective interactions are rather a rule than an exception among organometallic species.