Group VIB Chromium, Molybdenum, and Tungsten

Although many stable cycloolefin complexes of the group VIB metals have been reported (47, 268), it is only recently that tt complexes of the simple monoolefins such as ethylene have been isolated (148, 195, 203, 572). 

With several functionally substituted ethylenes, stable it complexes of molybdenum and tungsten of the general form L M(CO)g 2 can be prepared, according to Eq. (1)  

From the reaction of vinyl methyl ketone with (CH3CN)3M(CO)3, (M = Cr or Mo), King (348) has isolated the complexes, (vinyl methyl ketone)sM, as yellow volatile solids. Although the molybdenum complex 

The failure to obtain complexes containing more than two acrylonitrile ligands by displacement of carbon monoxide from M(CO)g may be due to the fact that either the complex or the ligands cannot withstand the rigorous reaction conditions. It is possible, however, to prepare the series (AN) M(CO)g n=l, 2, or 3 AN = acrylonitrile M = Cr, Mo, or W) in good yields by displacement of acetonitrile under mild conditions from its corresponding complexes (508, 571). 

The CT-allyl complexes of Mo (148) and W (258) react readily with hydrogen chloride in petroleum ether to produce with high yield a cation (9), which contains a TT-complexed propylene molecule (257). The chloride (M = Mo) is readily soluble in water, reacting to form (C5H5)Mo(CO)3Cl. 

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