Organometallic Complexes of Bulky, Optically Active, C3-Symmetric Tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate(ToP*).

A bulky, optically active monoanionicscorpionate ligand, tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate(ToP*), is synthesized from the naturally occurring aminoacid l-valine as its lithium salt, Li[ToP*] (1). That compound is readily converted to the thallium complexTl[ToP*] (2) and to the acid derivative H[ToP*] (3). Group 7 tricarbonyl complexes ToP*M(CO)3(M = Mn (4), Re (5))are synthesized by the reaction of MBr(CO)5and Li[ToP*] and are crystallographically characterized. The νCObands in their infrared spectra indicate that π back-donationin the rhenium compounds is greater with ToP* than withnon-methylated tris(4S-isopropyl-2-oxazolinyl)phenylborate(ToP). The reaction of H[ToP*] and ZnEt2gives ToP*ZnEt (6), while ToP*ZnCl (7) is synthesized from Li[ToP*] and ZnCl2. The reaction of ToP*ZnCl andKOtBu followed by addition of PhSiH3providesthe zinc hydride complex ToP*ZnH (8). Compound 8is the first example of a crystallographically characterizedoptically active zinc hydride. We tested its catalytic reactivityin the cross-dehydrocoupling of silanes and alcohols, which providedSi-chiral silanes with moderate enantioselectivity. [ABSTRACT FROM AUTHOR]