Synthetic and NMR studies of neutral and cationic dinuclear fulvalene zirconium complexes containing the "Zr-2(mu-(CNBu)-Bu-t)" unit

Methylation of the previously. described isocyanide-bridged complex [{Zr(et a(5)-C5H5)Cl}(2)(mu-(CNBu)-Bu-t)(mu-eta(5)-C5H4-eta(5)-C5H4)] with 2 equiv of MgClMe in toluene at 80 degrees C afforded the dinuclear dimethyl comple x [{Zr(eta(5)-C5H5)(CH3}(2)(mu-(CNBu)-Bu-t)(mu-eta 5-C5H4)]. The same react ion with I or 2 equiv of MgClMe at room temperature gave a mixture of compo unds containing the dimethyl derivative 1 and two isomers of the monomethyl derivative [{Zr(eta(5)-C5H5)}(2)-(CH3)(Cl)(mu-(CNBu)-Bu-t)(mu-eta(5)-C5H4- eta(5)-C5H4)], 2a, 2b, identified by NMR spectroscopy. Analogous methylatio n of the related compound [{Zr(eta(5)-1,3-(Bu2C5H3)-Bu-t)Cl}(2)(mu-(CNBu)-B u-t)(mu-eta(5)-C5H4-eta(5)-C5H4)], isolated by reaction of the zirconium(II I) derivative [{Zr(eta(5)-1,3-(Bu2C5H3)-Bu-t)(mu-Cl)}(2)(mu-eta(5)-C5H4-eta (5)-C5H4)] With 1 equiv of (CNBu)-Bu-t in toluene, gave a mixture of uniden tified compounds. Treatment of the dimethyl complex [{Zr(eta(5)-C5H5)(CH3)} (2)(mu-(CNBu)-Bu-t)(mu-eta(5)-C5H4)] 1, with 1 equiv of the Lewis acid B(C6 F5)(3) in dichloromethane at -78 degrees C affords the new yellow crystalli ne zirconium cationic derivative [{Zr(eta(5)-C5H5)}(2)(mu-CH3)(mu-(CNBu)-Bu -t)(mu-eta(5)][BMe(C6F5)(3)], 4. Hydrolysis of the mu-methyl compound 4 led to the mu-hydroxo cationic derivative [{Zr(eta(5)-C5H5)}(2)(mu-OH)(mu-(CNB u)-Bu-t)(mu-eta(5)-C5H4-eta(5)-C5H4)][BMe(C6F5)(3)], 5. Compound 4 reacts w ith an excess of isocyanides CNR in dichloromethane at -78 degrees C to giv e the cationic species [{Zr(eta(5)-C5H5)}(2)(CH3)(CNR)(mu-CNR)(mu-eta(5)-C5 H4)][BMe(C6F5)(3)] (R = Bu-t, 6;2,6-Me2C6H3, 7). All of the reported compou nds were characterized by the usual analytical and NMR spectroscopic method s, which are discussed.