Structural and electronic effects of cation binding (Li+, Na+, K+, Mg2+ and Ca2+) to the π system of the (η6-benzene)-Cr(Co)3 complex: A theoretical study

Abstract

Cation binding to the π-electrons of benzene is known to show a periodic trend in interaction energies. In the present work, the chemistry of cation-π interaction in a benzene ring bound with tripodal Cr(CO) 3 (BC) was considered. In contradiction to the anticipated destabilisation due to competition between two Lewis acids towards a common sandwiched base, cation binding with BC showed a similar trend as that to benzene. Furthermore, it was found to activate the benzene ring by reducing the frontier orbital energy gap substantially. The NICS zz index adds sufficient evidence to the arguments. In addition, TDDFT studies indicate a bathochromic shift upon cation binding as an immediate consequence of the reduction in the energy of the Frontier orbital.

Does alkali cation binding to aromatic ring retard the fluxional haptotropic migration? Evidences from density functional study

“…These isomers are fortunately interconvertible through the haptotropic shift of Cr(CO) 3 from one ring to another. The thermodynamic stability of the isomers MNCA and B are of interest since it would clarify the role of extended aromaticity in affecting the stability of the so called πacid base interacting sandwich molecules (which has been explored in terms of role of cations in our earlier paper 19 ). Also the subtle insights of role of cationπ interaction in influencing the fluxional haptotropic behaviour is studied by locating the haptotropic transition state (MNC-TS) ( Figure 1).…”

“…[5][6][7][8][9][10] η 6 -arene-Cr(CO) 3 systems are the most extensively studied half-sandwich complexes. [11][12][13][14][15][16][17][18][19] Many experimental and theoretical investigations have extensively explored the conformational biasing, barrier to tripodal rotation, aromaticity, structural and energetics of such complexes. [11][12][13][14][15][16][17][18][19] Exclusively, the π-complexes of polycyclic aromatics with metal moiety has the ability to undergo haptotropic rearrangements.…”

“…[11][12][13][14][15][16][17][18][19] Many experimental and theoretical investigations have extensively explored the conformational biasing, barrier to tripodal rotation, aromaticity, structural and energetics of such complexes. [11][12][13][14][15][16][17][18][19] Exclusively, the π-complexes of polycyclic aromatics with metal moiety has the ability to undergo haptotropic rearrangements. There are two ways in which haptotropic rearrangements may * For correspondence proceed; (i) when the metal moiety changes its πcoordination to the arene ligand within the same ring (intra-ring haptotropic) and (ii) when it involves migration of metal moiety from one of the aromatic ring to the other (inter-ring haptotropic).…”

“…41,43,44 In our previous theoretical work we have reported the structural and electronic effects of cation binding to π system of η 6 -benzene-Cr(CO) 3 . 19 Although many factors that affect the haptotropicity have been reported to the best of our knowledge, effect of cation binding on the aromatic ring on the haptotropic energetics and stability have not been explored. We consider it is worth exploring because we have already reported that the cation binding modulates the stability of the sandwich complex involving the Pearson's Hard and Soft Acid Base (HSAB) concept.…”

“…We consider it is worth exploring because we have already reported that the cation binding modulates the stability of the sandwich complex involving the Pearson's Hard and Soft Acid Base (HSAB) concept. 19 Therefore, assertively presuming the contribution of cation on fluxional haptotropic behaviour of Cr(CO) 3…”