Access to Monomeric Lead(II) Hydrides with Remarkable Thermostability and Their Use in Catalytic Hydroboration of Carbonyl Derivatives

We report on the remarkable stability of unprecedented, monomeric lead­(II) hydrides M + [LPb­(II)­H] – (M­[1-H]), where L = 2,6-bis­(3,5-diphenylpyrrolyl)­pyridine and M = (18-crown-6)potassium or ([2.2.2]-cryptand)­potassium. The half-life of [K18c6]­[1-H] of ∼2 days in tetrahydrofuran at 25 °C is significantly longer than those reported for dimeric lead­(II) hydrides supported by bulky terphenyl ligands (few hours at low temperatures), which are the only examples known for lead­(II) hydride compounds. The presence of a Pb–H bond in [1-H] – was unambiguously identified by multinuclear NMR spectroscopy. Remarkably, a 1H resonance of the hydride ligand was found at δ = 41.43 ppm (1 J PbH = 1312 Hz). For reactivity study, [1-H] – serves as an excellent hydroboration catalyst with high turnover numbers and turnover frequencies for several carbonyl compounds.