REACTIONS OF COMPOUNDS CONTAINING NI-NI, NI-MO, AND NI-W BONDS WITH ALLENE AND 1,1-DIMETHYLALLENE - X-RAY-DIFFRACTION STUDIES OF THE PI-ALLYLIC COMPLEXES NIMO(CO)2(MU-ETA-3,ETA-3-C9H12)(ETA-5-C5H5)(ETA-5-C5H4ME) AND NIMO(MU-CO)(CO)(MU-ETA-1,ETA-3-C(ME)-C(ME)-CH2)(ETA-5-C5H5)(ETA-5-C5H4ME) (NI-MO)

The reactions of the dinickel species [Ni(mu-CO)(eta-5-C5H5)]2 (Ni-Ni) and of the mixed-metal complexes (eta-5-C5H5)(CO)Ni-M(CO)3(eta-5-C5H4Me) [1a, M = Mo; 1b, M = W] with propa-1,2-diene (allene) and 3-methyl-1,2-butadiene (1,1-dimethylallene) are described. When [Ni(mu-CO)(eta-5-C5H5)]2 (Ni-Ni) is treated with allene, the nickel-nickel bond is ruptured and two allene units couple forming the 2,2'-bis(allyl) species (eta-5-C5H5)Ni(mu-eta-3,eta-3-C9H8)Ni(eta-5-C5H5) (2). No reaction ensues when the Ni2 complex is treated 1,1-dimethylallene. 1a and 1b react with allene, but the only heterobimetallic product characterized was (eta-5-C5H5)Ni{mu-eta-3,eta-3-C9H12}Mo(CO)2(eta-5-C5H4Me) (3), whose structure was determined by an X-ray diffraction study. Complex 3 contains no metal-metal bond, and the mu-eta-3,eta-3-C9H12 ligand that tethers the two metal centers together, derived from the trimerization of three allene units, is eta-3-coordinated in a pi-allyl fashion to each metal. Both 2 and 3 exhibit interesting CIMS: when isobutane is used as the ionization gas, a butyl cation adds on to the parent molecule of both species, forming (M + 57)+ ions for both species. 1,1-Dimethylallene reacts with complexes 1a, 1b, and (eta-5-C5H4Me)(CO)Ni-Mo(CO)3(eta-5-C5H5) (1a') to form the 2-nickel-substituted allylic complexes (eta-5-C5H4Me)Ni{mu-eta-1,eta-3-C(CMe2)(CH2)}M(CO)2(eta-5-C5H4R) (Ni-M) [4a, M = Mo; 4b, M = W] and (eta-5-C5H4Me)Ni{mu-eta-1,eta-3-C(CMe2)(CH2)}Mo(CO)2(eta-5-C5H5) (Ni-Mo) (4a'), respectively. On silica gel, isomerization to the 1-nickel-substituted allyl species (eta-5-C5H5)Ni{mu-eta-1,eta-3-C(Me)-C(Me)-CH2}(mu-2-CO)M(CO)(eta-5-C5H4Me) (Ni-M) [5a, M = Mo; 5b, M = W] and (eta-5-C5H4Me)Ni{mu-eta-1,eta-3-C(Me)-C(Me)-CH2}(mu-2-CO)Mo(CO)(eta-5-C5H5) (Ni-M) (5a'), respectively, takes place. Complex 4b reductively eliminates a nickel atom in a side reaction to form an isomeric mixture of 2-substituted 1,3- and 1,4-cyclopentadienyl-1,1-dimethylallyl species W(CO)2{eta-3-(CH2-C(C5H5)-CMe2)}(eta-5-C5H4Me) (6b). Related allene derived isomers W(CO)2{eta-3-(CH2-C(C5H5)-CH2)(eta-5-C5H4Me) (6) were isolated from the reaction of allene with 1b. Labeling studies using 1,1-dimethylallene-3-d1 or acetic acid-d1 demonstrated that an effective 1,4-proton shift and not a 1,2-methyl group migration was operative in the isomerization of 4a-d1 to 5a-d1. In contrast to the reactivity exhibited toward cumulated dienes, neither 1a nor 1b reacted with isoprene.