OPTICAL RESOLUTION AND REACTIVITY OF CHIRAL TUNGSTEN ALKYNE COMPLEXES

Displacement of a carbonyl ligand from a cationic dicarbonyltungsten complex, [Tp'W(CO)2(PhC=CMe)] [X] (Tp' = hydridotris(3,5-dimethylpyrazolyl)borate; X = BF4-, PF6-, and OTf-), by the counterion is effected by allowing the complex to reflux in THF. Substitution of the triflate ligand in Tp'(CO)(PhC=CMe)WOTf (= [W]-OTf) with (S)-(-)-alpha-methylbenzylamine yields a pair of tungsten amido diastereomers [W]-NHR*, 5-(RS) and 5-(SS), which are separable by crystallization. Protonation of each tungsten amido diastereomer yields optically pure cationic tungsten amine complexes. Acidification of the optically pure tungsten amine diastereomers, 6-(RS) and 6-(SS), in the presence of acetonitrile yields enantiomerically pure [W]-N=CMe+ complexes, (-)-7 and (+)-7. Displacement of the resolving amine in 6-(RS) and 6-(SS) by iodide yields optically pure [W]-I, (+)-8 and (-)-8. An X-ray structure of 6-(RS)-{[W]-NH2R*}{BF4} (space group P2(1)2(1)2(1), a = 16.130 (2) angstrom, b = 16.576 (4) angstrom, c = 15.256 (3) angstrom, Z = 4, R = 0.044, R(w) = 0.063) establishes the absolute configuration of the complex.