Developing a fulvene route to C1-bridged "constrained geometry" Ziegler catalyst systems

6-dimethylamino-6-methylfulvene (7) was converted to the [(C5H4)-CMe2-NMe2](-) ligand system (8) by treatment with methyllithium. Its reaction with MCl4 (M = Zr, Ti) followed by treatment with CH3Li gave the respective [(C5H4)-CMe2-NMe2](2)M(CH3)(2) complexes (12). Their reaction with B(C6F5)(3) led to reactive metallocene cation complexes that instantaneously underwent CH activation at a N-CH3 group to yield the metallacyclic cation complexes 15. (tert-butylaminomethyl)fluorene was prepared by the addition of tert-butylisocyanate to fluorenyllithium followed by hydride reduction. Deprotonation by a variety of bases gave rise to a series of competing and consecutive reactions to yield several unusually structured products, among them a fluorenyl-anellated eta(5)-1-azapentadienyl anion equivalent (25) and [(flu)-CH2-NCMe3]Li-2 (23). An improved way of generating synthetically useful C-1-linked [Cp-C-1(R)(n)-NR1](2-) dianion equivalents was developed starting from 6-amino-6-methylfulvene (26). N-silylation followed by double deprotonation with, e.g., lithium diisopropylamide cleanly furnished the respective [(C5H4)-C(=CH2)-NSiMe3](2-) dianion 33 (isolated as the dilithio derivative). Its reaction with Cl2Zr(NEt2)(2) in THF gave [eta(5):kappa-N-(C5H4)-C(=CH2)-NSiMe3]Zr(NEt2)(2) 36. Activation of 36 with methylalumoxane in toluene led to the formation of a C-1-linked "constrained geometry" Ziegler catalyst that polymerized ethylene similarly as the [(C5Me4)SiMe2NCMe3]ZrCl2 derived literature system.