Reactivity of Strontium Hydride Supported by the Superbulky Hydrotris(pyrazolyl)borate Ligand

Hydrogenolysis of [(Tp^{Ad,<i>i</i>Pr})Sr{CH(SiMe₃)₂}] (<b>1</b>) (Tp^Ad,<i>ⁱ</i>^Pr = hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate) in hexane solution under 20 atm of H₂ allowed for the isolation of strontium hydride [(Tp^{Ad,<i>i</i>Pr})Sr(μ-H)]₂ (<b>2</b>) in good yield. Complex <b>2</b> exhibits the dimeric nature in solid state, featuring two different bond modes between the Sr center and Tp^{Ad,<i>i</i>Pr} ligand. Treatment of complex <b>2</b> with PhC(H)═N<i>^t</i>Bu or PhCH₂Bpin (Bpin = pinacolateborane) afforded the strontium amide complex [(Tp^{Ad,<i>i</i>Pr})Sr{N(CH₂Ph)(<i>^t</i>Bu)}] (<b>4</b>) and hydroborate complex [(Tp^{Ad,<i>i</i>Pr})Sr{μ-HBpin(CH₂Ph)}] (<b>5</b>), respectively. Reactions of complex <b>2</b> with 2-picoline, 2-phenylquinoline, or 2-phenylpyridine led to the formation of strontium 2-pyridylmethylene/2-picoline complex [(Tp^{Ad,<i>i</i>Pr})Sr(2-CH₂-Py)(2-picoline)] (<b>6</b>), reductively coupling diphenyl-biquinolide complex [{(Tp^{Ad,<i>i</i>Pr})Sr}₂(2,2'-Ph₂-4,4'-dihydro-4,4'-biquinolide)] (<b>7</b>), and diphenyl-bipyridyl radical complex [(Tp^{Ad,<i>i</i>Pr})Sr(6,6'-Ph₂-2,2'-bipyridyl)] (<b>8</b>), separately. All of the complexes have been well characterized, including NMR spectrum and single-crystal X-ray analysis.