Facile Hapticity Changes in (1-Hydronaphthalene)manganese Complexes, Ligand Addition and Photochemical Ligand Cleavage

Abstract

Tricarbonyl(2–4,4a,8a‐η‐1‐hydronaphthalene)manganese (1) reacts readily with trimethyl phosphite to afford tricarbonyl(2–4‐η‐1‐hydronaphthalene)(trimethyl phosphite)manganese (2), by a simultaneous η5‐η3‐hapticity change. Upon UV irradiation, one carbonyl ligand is preferentially cleaved from 2 to yield dicarbonyl(2–4,4a,8a‐η‐1‐hydronaphthalene)(trimethyl phosphite)manganese (3), with a η5‐coordinated 1‐hydronaphthalene ligand. In a similar fashion 3 also reacts with trimethyl phosphite and forms dicarbonyl(2–4‐η‐1‐hydronaphthalene)bis(trimethyl phosphite)manganese (4), which loses carbon monoxide upon UV irradiation to afford carbonyl(2–4,4a,8a‐η‐1‐hydronaphthalene)bis(trimethyl phosphite)manganese (5). All compounds were characterized by IR and NMR spectroscopy. The η5‐1‐hydronaphthalene complexes 1, 3 and 5 show hindered 1,4‐H shifts of 1‐Hendo. Considerable energy barriers were also found for the rotation of the 1‐hydronaphthalene ligand in 2–5.