Heterotrimetallic compounds containing Mo–M–Li [M = K, Rb and Cs] clusters: synthesis, structure, bonding, aromaticity and theoretical investigations of Li2M2 [M = K and Rb] and Cs4 rings

Abstract

A new polydentate fac-trioxo molybdenum complex, [MoO(3)L](3-) {LH(3) = nitrilotriacetic acid}, has been synthesized by the reaction of lithium molybdate with iminodiacetic acid. The trinegative complex anion coordinates the alkali metal cations, K(+), Rb(+) or Cs(+). The potassium, rubidium and cesium complexes, [Li{K(H(2)O)(2)}MoO(3)L](n) (1), [Li{Rb(H(2)O)(2)}MoO(3)L](n) (2) and [Cs{Li(H(2)O)}(2)MoO(3)L](n) (3), form heterotrimetallic coordination chains, containing planar rings of Li(2)M(2) (M = K or Rb) and Cs(4). Theoretical investigations on these rings were carried out using NICS calculations and ab initio ring current maps, revealing aromaticity to be of limited significance.