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(4<i>S</i>-isopropyl-5,5-dimethyl-2-oxazolinyl)­phenylborate (To^P*), is synthesized from the naturally occurring amino acid l-valine as its lithium salt, Li­[To^P*] (<b>1</b>). That compound is readily converted to the thallium complex Tl­[To^P*] (<b>2</b>) and to the acid derivative H­[To^P*] (<b>3</b>). Group 7 tricarbonyl complexes To^P*M­(CO)₃ (M = Mn (<b>4</b>), Re (<b>5</b>)) are synthesized by the reaction of MBr­(CO)₅ and Li­[To^P*] and are crystallographically characterized. The ν_CO bands in their infrared spectra indicate that π back-donation in the rhenium compounds is greater with To^P* than with non-methylated tris­(4<i>S</i>-isopropyl-2-oxazolinyl)­phenylborate (To^P). The reaction of H­[To^P*] and ZnEt₂ gives To^P*ZnEt (<b>6</b>), while To^P*ZnCl (<b>7</b>) is synthesized from Li­[To^P*] and ZnCl₂. The reaction of To^P*ZnCl and KO<i>t</i>Bu followed by addition of PhSiH₃ provides the zinc hydride complex To^P*ZnH (<b>8</b>). Compound <b>8</b> 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

Selective Dialkylation of a Doubly Linked Dicyclopentadiene Ligand and the Ensuing Ruthenium Complexes

The selective alkylation (Me or <i>tert</i>-butyl) of a doubly linked dicyclopentadiene ligand is presented. The reaction of (C₅H₃(<i>t</i>-Bu))₂(CMe₂)₂ (<b>4a</b>,<b>b</b>), the di-<i>tert</i>-butyl-substituted ligand, with RuCl₃·3H₂O in MeOH at 140 °C for 15 min, followed by heating in CHCl₃, gave the chloro-bridged complex <i>cis</i>-{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(μ-Cl)₂Cl₂ (<b>5</b>) in 28% yield. Reduction of <b>5</b> with Zn in MeCN gave the chloro-bridged tetrakis­(acetonitrile) complex <i>cis</i>-[{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(MeCN)₄(μ-Cl)]⁺ (<b>6</b>) in 62% yield. Addition of AgOTf to <b>6</b> in MeCN removed the bridging chloro ligand and gave [<i>cis</i>-{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(MeCN)₆]­[OTf]₂ (<b>7</b>) in 38% yield. The X-ray crystal structures of <b>5</b> and <b>6</b> are reported