Synthesis and some reactivity of amidinato(pyridine) complexes of molybdenum and tungsten formulated as [M(η3-allyl)(amidinato)(CO)2(NC5H5)]

Bis(pyridine) complexes of molybdenum and tungsten, [M(η3-allyl)Cl(CO)2(NC5H5)2] (M=Mo; 3-Mo, M=W; 3-W), reacted with an equimolar amount of lithiated amidinate, Li[(PhN)2CR] (R=H; 4a-Li, R = CH3; 4b-Li), to yield corresponding amidinato(pyridine) complexes, [M(η3-allyl){(PhN)2CR}(CO)2(NC5H5)] (M=Mo, R=H; 5a-Mo, M=Mo, R=CH3; 5b-Mo, M=W, R=H; 5a-W), as a yellow solid. The dissociation of pyridine ligand from the central metal in complexes 5a was observed in a polar solvent such as acetonitrile. In these cases, although the formation of amidinato(acetonitrile) complexes, [M(η3-allyl){(PhN)2CH}(CO)2(NCMe)] (M=Mo; 6a-Mo, M=W; 6a-W), was suggested spectroscopically, isolation of complexes 6a was not successful but the re-formation of pyridine complexes 5a was observed. In the reactions of complexes 5a with PEt3 and with P(OMe)3, the substitution reactions easily took place to give [M(η3-allyl){(PhN)2CH}(CO)2(PEt3)] (M=Mo; 7a-Mo, M=W; 7a-W) and [M(η3-allyl){(PhN)2CH}(CO)2{P(OMe)3}] (M=Mo; 8a-Mo, M=W; 8a-W), respectively. These complexes were characterized spectroscopically as well as, in some cases, by X-ray analyses.