Organometallic Complexes of Bulky, Optically Active, <i>C</i>₃‑Symmetric Tris(4<i>S</i>‑isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (To^P*)

A bulky, optically active monoanionic scorpionate ligand, tris­(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)­phenylborate (ToP*), is synthesized from the naturally occurring amino acid l-valine as its lithium salt, Li­[ToP*] (1). That compound is readily converted to the thallium complex Tl­[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)5 and Li­[ToP*] and are crystallographically characterized. The νCO bands in their infrared spectra indicate that π back-donation in the rhenium compounds is greater with ToP* than with non-methylated tris­(4S-isopropyl-2-oxazolinyl)­phenylborate (ToP). The reaction of H­[ToP*] and ZnEt2 gives ToP*ZnEt (6), while ToP*ZnCl (7) is synthesized from Li­[ToP*] and ZnCl2. The reaction of ToP*ZnCl and KOtBu followed by addition of PhSiH3 provides the zinc hydride complex ToP*ZnH (8). Compound 8 is the first example of a crystallographically characterized optically active zinc hydride. We tested its catalytic reactivity in the cross-dehydrocoupling of silanes and alcohols, which provided Si-chiral silanes with moderate enantioselectivity.