Collective interactions among organometallics are exotic bonds hidden on lab shelves

Abstract

Recent discovery of an unusual bond between Na and B in NaBH3− motivated us to look for potentially similar bonds, which remained unnoticed among systems isoelectronic with NaBH3−. Here, we report a novel family of collective interactions and a measure called exchange-correlation interaction collectivity index (ICIXC; $${ICI}\in \left[{{{{\mathrm{0,1}}}}}\right]$$ I C I ∈ 0, 1 ) to characterize the extent of collective versus pairwise bonding. Unlike conventional bonds in which ICIXC remains close to one, in collective interactions ICIXC 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 [Ma+AR3]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 XFn systems (X: B or C). Some of organolithium and organomagnesium species have the lowest ICIXC among the more than 100 studied systems revealing the fact that collective interactions are rather a rule than an exception among organometallic species.

Theoretical investigation of borane compounds mimicking transition metals for N2fixation and activation

“…As a result, this synergetic effect results in a linear equation between Δ E bin and the number of the B–X σ bonds. This finding is in accordance with recent studies 22 which suggest substituents on boron do play an important role in the formation of chemical bonds between boron and other substituents.…”

Atoms in molecules in real space: a fertile field for chemical bonding

“…One of the characteristic features of IQA, the assessment on an equal-footing of all metal⋯ligand, ligand⋯ligand and/or metal⋯metal pairwise interactions can shed further light on complex bonding effects involving either direct or through-space interactions. A striking example is found in the recent analysis 172 of the [M n + ⋯CR 3 ] 1− n pyramidal adducts constituted by alkaline and alkaline-earth cations (M n + = Li + ,Na + ,Ca 2+ ,…) and various anionic fragments ( e.g. , C(CN) 3 − ,CF 3 − ,C(Ph) 3 − ).…”

On the existence of collective interactions

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Recently, Sowlati-Hashjin et al 1 have used the exchange-correlation interaction collectivity index (ICIXC; ICIXC  [0,1]) to conclude that the nature of the Li-C chemical bond in LiCF3 differs significantly from that in LiCPh3 (Ph = phenyl).Whereas the Li-C bond of LiCF3 is classified as a conventional two-center two-electron bond (ICIXC = 0.910, ICIXC > 0.9 and close to 1), that of LiCPh3 is categorized as a collective bond (ICIXC = 0.393). The authors claim that collective bonds take place in systems composed of MAR3 (M = metal; A = C, B or Al; R = substituent) when M forms a stronger bond with the substituents R than with the central atom A.

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“…Recently, Sowlati-Hashjin et al 1 have used the exchange-correlation interaction collectivity index (ICIXC; ICIXC  [0,1]) to conclude that the nature of the Li-C chemical bond in LiCF3 differs significantly from that in LiCPh3 (Ph = phenyl).…”

“…the opposite. The small ICIXC, calculated as VXC(Li-C)/VXC(Li-{T}) where T stands for the set of all atoms of the system except the C directly attached to Li, of LiCPh3 of Sowlati-Hashjin et al1 is likely the result of dividing a relatively low VXC(Li-C), because of the high polarity of this bond, by a large number of small long-range VXC(Li-CPh) and VXC(Li-HPh) contributions. It does not reflect any special chemical bond in this species, let alone a strong through-space interaction between the Li and the phenyl groups that could indicate collective bonding.…”