Synthesis and structures of titanium and yttrium complexes with N,N '-tetramethylguanidinate ligands: different reactivity of the M-N bonds toward phenyl isocyanate

A salt elimination reaction of bis(cyclopentadienyl) titanium dichloride (C5H5)(2)TiCl2 with one equiv. of N,N'-tetramethylguanidinate lithium [LiN=C(NMe2)(2)] proceeded in THF at room temperature to yield a bis(cyclopentadienyl) titanium mono-guanidinate chloride (C5H5)(2)TiCl(N=C(NMe2)(2)) (1). However, treatment of two equiv. of LiN= C(NMe2)(2) with (C5H5)(2)TiCl2 under the same conditions resulted in the elimination of one cyclopentadienyl ring to form an unexpected mono(cyclopentadienyl) titanium bis(guanidinate) chloride (C5H5) TiCl[N=C(NMe2)(2)](2) (2), in which only one Ti-Cl bond is broken, with the other Ti-Cl bond retained. Reaction of [(C5H5)(2)YCl](2) with LiN= C(NMe2)(2) gave the corresponding product {(C5H5)(2)Y[mu-eta(1): eta(2)-N=C(NMe2)(2)]}(2) (3). On further investigations on the reactivity of 1-3 toward phenyl isocyanate, we found phenyl isocyanate only inserts into the Y-N(mu-Gua) bonds of 3 to yield [(C5H5)(2)Y(mu-eta(1): eta(2)-OC(N=C(NMe2)(2))NPh)](2) (4). Complexes 1-4 were characterized by elemental analysis and spectroscopic properties and their solid-state structures were determined by X-ray single-crystal diffraction.