449810-79-1Relevant academic research and scientific papers
Coordinating properties of mixed pyrrolyl/dicarbollide cobalt metallocene-type complexes
Llop, Jordi,Vinas, Clara,Teixidor, Francesc,Victori, Lluis
, p. 1559 - 1565 (2002)
Mixed-sandwich Co(III) complexes incorporating an η5 pyrrolyl unit [η5-NC4H4]- are very stable when the second η5 moiety is a dicarbollide [η5-C2B9H11]2-. The existence of a lone pair on N in the neutral closo-[3-Co(η5-NC4H4)-1,2-C2B 9H11] (1) has allowed for the first time a study of the N-σ bonding capacity of a pyrrolyl ligand η5 bonded to a metal in an oxidation state higher than two. This capacity has been proven by reacting closo-[3-Co(η5-NC4H4)-1,2-C2B 9H11] with Lewis acids (BH3, BF3 and Ag+) and a Co(III) macrocycle. In all cases the reaction went to completion proving the strength of the σ bond generated. The stability of the [3-Co(η5-NC4H4)-1,2-C2B9 H11] complexes vs. oxidation state Co(III)/Co(II) was studied by cyclic voltammetry. It was found that [3-Co(η5-NC4H4)1,2-C2B9 H11]- is not as stable as [3-Co(η5-NC4H4)-1,2-C2B9 H11]; however, when coordinated to cobalt(III), both [3-Co(η5-NC4H4)-1,2-C2B9 H11]- and [3-Co(η5-NC4H4)-1,2-C2B9 H11] are of comparable stability. The stability of the reduced form Co(II) in the mixed pyrrolyl/dicarbollide is enhanced when an electron withdrawing group is bonded to the cluster carbon atom in the dicarbollide.
