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

Abstract

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.

London Dispersion Effects on the Stability of Heavy Tetrel Molecules

“…[33] It was later shown that these diplumbynes could also be accessed by the reduction of the parent Pb(II) halide. It should be noted that very few lead(II) hydride complexes have been isolated or detected, (see reports from Liu and Wesemann) [49,50] and LD effects likely play a role in their stabilization. [51] Certainly, for the diplumbynes, interligand dispersion interactions between each of Pb(II) fragments play a crucial role in their stability.…”

A Bis-Cyclopentadienyl Ligand-Supported Di-Iron Trihydride Motif as a Synthon for Access to Heterobimetallic Trinuclear Complexes

“…Driven by our interest in metal hydride chemistry and multimetallic structures, we have previously employed pyrrolesligands that are isoelectronic and nitrogen analogues of Cp R to stabilize low-valent main group Sn and Pb hydrides and multimetallic frameworks containing metal–metal bonds. , Given the extensive applications of this specific set of donors in organometallic and inorganic chemistry, and considering the frequent occurrence of multiple metal clusters in their reactions, our objective was to develop compounds in which an iron hydride cluster is supported by two prearranged Cp donors with sufficient steric protection to maintain low coordination numbers on iron centers. Tethering two Cp R groups together results in a bis-Cp ligands that are suitable for accommodating two metal centers, forming two half-sandwiched metal complexes.…”

“…Examples of such complexes include (Cp′Fe) 2 (μ-H) n (n = 3, A; n = 4, B; Cp′ = 1,2,4-C 5 H 2 t Bu 3 ), 20 (Cp*Fe) 2 (μ-H) 4 (C; Cp* = C 5 Me 5 ), 21 ( 5 CpFe) 2 (μ-H) 4 (D; 5 Cp = C 5 i Pr 5 ), 22 and ( 4 CpFe) 2 (μ-H) 4 (E; 4 Cp = C 5 H i Pr 4 ). 23 Driven by our interest in metal hydride chemistry and multimetallic structures, we have previously employed pyrroles�ligands that are isoelectronic and nitrogen analogues of Cp R �to stabilize low-valent main group Sn 24 and Pb 25 hydrides and multimetallic frameworks containing metal− metal bonds. 26,27 Given the extensive applications of this specific set of donors in organometallic and inorganic chemistry, and considering the frequent occurrence of multiple metal clusters in their reactions, our objective was to develop compounds in which an iron hydride cluster is supported by two prearranged Cp donors with sufficient steric protection to maintain low coordination numbers on iron centers.…”

LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

“…Yet another hallmark of pincer ligands, including the carbazolide pincer, is its ability to solubilize complexes otherwise insoluble in most solvents, as was the case for a recently reported class of lead­(II) complexes . The chemistry of molecular lead is overshadowed by reports of metallic lead formation due to the decomposition of its organometallic complexes, in addition to its poor solubility generally forming insoluble precipitates. − However, the carbazolide sufficiently stabilizes various lead­(II) halide complexes ( 11 – 13 , Scheme ), while it was reported that these complexes are well soluble in solvents of low polarity, such as aromatic hydrocarbon and ether solvents . A rare example of a molecular lead­(II) fluoride 15 was isolated by reacting 14 with the fluorinating reagent Me 3 SnF for 7 days at 85 °C (Scheme ).…”