Unsaturation and variable hapticity in binuclear azulene manganese carbonyl complexes?

Dalton Transactions Pub Date: 2010-10-18 DOI: 10.1039/C0DT00807A

Abstract

Azulene is reported to react with Mn2(CO)10 to give trans-C10H8Mn2(CO)6, which has been shown by X-ray crystallography to have a bis(pentahapto) structure with no metal-metal bond. This structure is found by density functional theory to be the lowest energy C10H8Mn2(CO)6 structure. However, a corresponding bis(pentahapto) cis-C10H8Mn2(CO)6 structure, also without an Mn?Mn bond, lies within ～1 kcal mol?1 of this global minimum. The lowest energy C10H8Mn2(CO)5 structure is singlet cis-η5,η5-C10H8Mn2(CO)5 with an Mn→Mn dative bond from the Mn(CO)3 group to the Mn(CO)2 group. However, a singlet cis-η6,η4-C10H8Mn2(CO)5 structure with a normal Mn–Mn single bond lies within ～6 kcal mol?1 of this global minimum. The lowest energy structures of the more highly unsaturated C10H8Mn2(CO)n (n = 4, 3, 2) systems all have cis geometries and manganese-manganese bonds of various orders. The corresponding global minima are triplet cis-η5,η3-C10H8Mn2(CO)3(η2-μ-CO) for the tetracarbonyl with a four-electron donor bridging carbonyl group, singlet cis-η5,η5-C10H8Mn2(CO)3 for the tricarbonyl, and triplet cis-η6,η4-C10H8Mn2(CO)(η2-μ-CO) for the dicarbonyl.

Graphical abstract: Unsaturation and variable hapticity in binuclear azulene manganese carbonyl complexes
Recommended Literature