Study of reactions of molybdenum (ii) and tungsten (ii) halocarbonyls with nitrogen bases.
Nyawade, Adhiambo Eunice
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The study focused on the possible oxidation of various nitrogen bases by molybdenum(II) and tungsten(II) halocarbonyls, formation of zerovalent aminecarbonyl metal complexes and mode of coordination of nicotine to molybdenum and tungsten. Aminecarbonyls of the type M(CO)3L3 (M=Mo, W; L= CH3NH2, CH3CH2)2NH), M(CO)4TMEDA and M(CO)5nicotine were prepared by a reaction of the halocarbonyls [M(CO)4X2]2 (M=Mo, W; X=Br or Cl) with selected nitrogen bases. The crystal structure of Mo(CO)4TMEDA and W(CO)5nicotine well obtained by X-ray diffraction confirming the structures of the compounds Nicotine coordinated to the metal through the imine nitrogen, as shown seen in the crystal structure, to form M(CO)5(nicotine) (M=Mo, W). The amine carbonyl compounds were isolated by filtration while the organic by-products, were isolated from the filtrate by column chromatography. The nitrogen bases were oxidized by the halocarbonyls to imines which may have been hydrolyzed by water to an amine and an aldehyde or a ketone. This was shown by the presence of IR bands in the region of 1740cm-I in the infrared spectra of all the oily by-products from reaction of M(CO)4X2 (M=Mo, W; X=Br or Cl) with N,N-methylamine. The ethyleiiamine was hydrolysed to methanal and methylamine. The presence of a new IR band at 1651.9cm-1 in the IR spectrum of the oily by-product from reaction of nicotine with the tetrahalocarbonyls suggested that nicotine was oxidized by the tetrahaIooctacarbonyImetaI(11) M(CO)4X2 (M=Mo, W; X=Br or Cl). 11I NMR, "C NMR, infrared spectroscopy, melting point and elemental analysis were used to characterize the products. The halides were determined gravimetrically as the silver halides, AgX (X=Br or Cl) while molybdenum and tungsten were determined by weighing as the oxides M03 (M=Mo, W). The results confirmed that the reactions of the halocarbonyls [M(CO)4X2]2 (M=Mo, W; X=Br or CI) with the nitrogen bases studied takes place via a redox mechanism. All preparative work was done in an atmosphere which was dry and oxygen-free