Manganese carbonyl compounds of N,N-bidentate di-2-pyridylketone (dpk) and N,O,N-tridentate hydroxybis(2-pyridyl)methanolato (dpkO,OH). The structure of fac-[Mn(CO) 3(dpkO,OH)

Abstract

Electrochemical measurements on fac-[Mn(CO) 3(dpk)Br] and fac-[Mn(CO) 3(dpkO,OH)] revealed solvent dependence and rich redox properties and X-ray studies on fac-[Mn(CO) 3(dpkO,OH)] show distorted octahedral geometry around manganese with the major distortion is due to the binding of hydroxybis(2-pyridyl)methanolato (dpkO,OH) anion and anti-parallel tapes of fac-[Mn(CO) 3(dpkO,OH)] interlocked via a network of hydrogen bonds. When di-2-pyridyl ketone (dpk) was allowed to react with [Mn(CO) 5Br] in dry diethyl ether under ultrasonic conditions fac-[Mn(CO) 3(dpk)Br] was isolated in good yield and when the same reaction was carried out under reflux conditions in toluene fac-[Mn(CO) 3(dpkO,OH)] was isolated. Infrared spectra of the isolated compounds confirmed their fac-geometry and the presence and absence of the ketonic group of dpk. Electrochemical measurements on fac-[Mn(CO) 3(dpk)Br] reveal sensitivity to solvents and the presence of reversible and irreversible electronic transfers. In contrast to fac-[Re(CO) 3(dpk)Cl] where noteworthy electrochemical reactions with CO 2 were observed, the electrochemical reactions of CO 2 with fac-[Mn(CO) 3(dpk)Br] disclosed no significant reaction. However, when fac-[Mn(CO) 3(dpk)Br] was allowed to electrochemically interact with group I and II metal ions considerable electrochemical changes were noted on the second reduction wave that may point to the possible use of fac-[Mn(CO) 3(dpk)Br] as an electrochemical sensor for group I and II metal ions. The electrochemical properties of fac-[Mn(CO) 3(dpkO,OH)] show the presence of closely spaced irreversible oxidations and probable electrochemical oxidation of coordinated dpkO,OH anion to dpk in dmf. Crystals of fac-[Mn(CO) 3(dpkO,OH)] obtained from dimethyl sulfoxide (dmso) solution of fac-[Mn(CO) 3(dpkO,OH)] are in the monoclinic C2/c space group. Structural analysis on fac-[Mn(CO) 3(dpkO,OH)] disclosed distorted octahedral coordination about manganese with the major distortion due to the tridentate coordination of dpkO,OH anion and the packing of molecules show stacks of anti-parallel tapes of fac-[Mn(CO) 3(dpkO,OH)] interlocked via a network of hydrogen bonds.