Publication Details (including relevant citation information):
Todd W. Graham, James Kickham, Silke Courtenay, Pingrong Wei, and Douglas W. Stephan Organometallics, 2004, 23 (13), 3309
The redox chemistry of phosphinimide-containing group IV metal complexes has been investigated. Reaction of the simple phosphinimide species CpTi(NPR3)Cl2 (R = Me 1, i-Pr 2) with Mg affords complexes formulated as [CpTiCl(μ-NPR3)]2 (R = Me 3, i-Pr 4). In contrast, CpTi(NPt-Bu3)Cl2 (5) is reduced by Mg to a putative Ti(II) species that can be intercepted by a variety of reagents including 2,3-dimethyl-1,3-butadiene, diphenylacetylene, phenylacetylene, bis(trimethylsilyl)acetylene, ethylene, and propylene to give monometallic metallacyclic complexes. In this fashion, the Ti(IV) metallacycles CpTi(NPt-Bu3)(CH2C(Me)C(Me)CH2), 6, CpTi(NPt-Bu3)(CPh)4, 7, CpTi(NPt-Bu3)(C(Ph)CHC(Ph)CH), 8, CpTi(NPt-Bu3)(η2-C2(SiMe3)2), 9, CpTi(NPt-Bu3)(CH2)4, 10, CpTi(NPt-Bu3)(CH2CHMe)2, 15, and CpTi(NPt-Bu3)(CH2)2(CPh)2, 16, were prepared. Related intramolecular formation of metallacycle complexes was achieved upon reduction of Cp‘Ti(t-Bu2(2-C6H4Ph)PN)Cl2 (Cp‘ = Cp 18, Cp* 19). The products [Cp‘Ti(NPtBu2(2-C6H4Ph)] (Cp‘ = Cp 20, Cp* 21) contained η6-interactions between Ti and the 2-phenyl substituent of the biphenyl unit. While Ti(II)-phosphinimide complexes have proven difficult to handle due to their reactivity, an unequivocal example of a Ti(II) species was obtained via reduction of Cp*Ti(NPt-Bu3)Cl2 (11) with Mg in the presence of CO, affording the species Cp*Ti(NPt-Bu3)(CO)2 (22). X-ray data for 4, 6, 7, 9, 10, 15, and 17−22 are reported.
Address (URL): http://pubs.acs.org/doi/abs/10.1021/om049826q