Synthesis and structure of Cp*2TiH, Cp*2TiH2Li(tmed), and [Cp*2TiOLi(THF)](2)

The solid-state crystal structure of the d(1) hydride Cp*2TiH shows that it has a bent sandwich structure with an open Cp*(centroid)-Ti-Cp*(centroid) angle of 150 degrees. The crystal structure contains two molecules in the a symmetric unit, and the hydridic hydrogen atom is located and refined with isotropic thermal parameters to a Ti-H distance of 1.69(5) and 1.84(4) Angs trom in each independent molecule; the average Ti-H distance is 1.76 Angstr om. In each molecule, the Ti-H vector lies on the idealized C-2 axis of the bent metallocene. The addition of n-BuLi and Me2NCH2CH2NMe2 (tmed) in hexa ne to Cp*2TiH or the addition of [Li(tmed)](2)C10H8 to Cp*2TiCl gives the a nionic dihydride Cp*Ti-2(mu-H)(2)Li(tmed). The hydride atoms are not locate d in the X-ray diffraction experiment, but electron paramagnetic resonance spectra show coupling to two equivalent hydrogen nuclei, A(H)(iso) = 9.6 G. In addition, coupling to Li-7, confirmed by the preparation of the Li-6 is otopomer, shows that the unpaired electron couples with each;hydridic hydro gen and lithium nucleus. The proposed structure has two hydride ligands bri dging the Cp*Ti-2 and Li(tmed) fragments. Water in tetrahydrofuran (THF) re acts with Cp*Ti-2(mu-H)(2)Li(tmed) to give the dimer, [Cp*2TiOLi(THF)](2). Its X-ray structure shows that the two Cp*2TiO fragments are joined togethe r by the Li(THF) fragments such that the Li2O2 unit; is a square as found i n dimeric lithium alkoxides; in this case, the alkoxide is the metallocene Cp*2TiO-. Variable-temperature magnetic susceptibility shows that the unpai red electrons on each Cp*2TiO- fragment are not coupled down to 5 K.