Mono- and di-nuclear complexes of molybdenum carbonyl derivatives with pyridine-2-carbaldehyde azine and phosphines: Syntheses, structure, spectroscopic and electrochemical characterisation and solvatochromic effects

Complexes containing phosphorus-donor ligands, [Mo(CO)(3)(PPh(3))(pa)](pa = pyridine-2-carbaldehyde azine), [Mo-2(Co)(6)(PPh(3))(2)(mu-pa)], [Mo-2(CO)(7)(PPh(3))(mu-pa)] and [Mo-2(CO)(6)(mu-dppe)(mu-pa)][dppe = 1,2-bis(diphenylphosphino)ethane], have been characterised by infrared and electronic spectroscopy, cyclic voltammetry and for the [Mo-2(CO)(6)(mu-dppe)(mu-pa)] complex a single crystal X-ray structure. All of the complexes show strong solvatochromism which has been analysed both by using the empirical parameter E*(MLCT) and by using McRae's equation. The results are compared with those of their parent complexes [Mo(CO)(4)(pa)] and [Mo-2(CO)(8)(mu-pa)], and with the results of extended-Huckel calculations with charge iteration.