3-Center-4-Electron Bonding in [(silox)₂MoN^tBu]₂(μ-Hg) Controls Reactivity while Frontier Orbitals Permit a Dimolybdenum π-Bond Energy Estimate

Abstract

Na/Hg reduction of (silox)2Cl2MoNtBu (3) afforded C 2 h [(silox)2MoNtBu]2(μ-Hg) (1 2-Hg), which consists of two distorted trigonal monoprisms with Hg at the each apex (d(MoHg) = 2.6810(5) Å). Calculations reveal 3c4e bonding in the linear MoHgMo linkage that renders 1 2-Hg susceptible to nucleophilic cleavage. Exposure to PMe3 and pyridine rapidly (<5 min) affords (silox)2(tBuN)MoL n (L = PMe3, n = 1 (1-PMe3); py, n = 2 (1-py2)), while poorer nucleophiles (L = C2H4, 2-butyne) yield adducts (e.g., 1-C2H4 and 1-C2Me2) after prolonged heating. The HOMO and LUMO of 1 2-Hg are “stretched” π and π* orbitals from which four states arise: 1Ag (GS), 3Bu, 1Bu, and 1Ag. ΔE = E(1Bu) − E(3Bu) = 2K, where K is the exchange energy. Magnetic studies indicate E(3Bu) − E(1Ag) ≈ 550 cm-1 (calcd 1744 cm-1), and a UV−vis absorption at 10 000 cm-1 is assigned to 1Ag → 1Bu, permitting K to be evaluated as 4725 cm-1. With the π → π* transition in Schrock's [Mo(NAr)(CH2 tBu)(OC6F5)]2 (4) assigned at 528 nm, this estimation places its π-bond energy as {E(π2 → ππ*1 in 4) − E(1Ag → 1Bu in 1 2-Hg)} + E(1Ag → 3Bu in 1 2-Hg) = 27 kcal/mol.

DFT Study on the Mechanism of Formic Acid Decomposition by a Well-Defined Bifunctional Cyclometalated Iridium(III) Catalyst: Self-Assisted Concerted Dehydrogenation via Long-Range Intermolecular Hydrogen Migration

“…To make a comparison, Figure also shows calculated WBIs and the 3c-4e bond diagram of F – ···H + ···F – . Clearly, the unusual O2···H–O1 H-bond in TS 11 ‑ 12 possess a large similarity to the 3c-4e bond in the F – ···H + ···F – system. − A similar 3c-4e bond between a formate and a formic acid has been reported by Wang et al Such a 3c-4e bond in TS 11 – 12 may be mainly responsible for stabilizing the transition state structure.…”

Highly Efficient Photo- and Electroluminescence from Two-Coordinate Cu(I) Complexes Featuring Nonconventional N-Heterocyclic Carbenes

“…Bond lengths to the ligands (Cu–C NHC = 1.868(2)–1.902(2) Å, Cu–N Cz = 1.852(1)–1.855(2) Å) are comparable to the values reported for mononuclear Cu–C NHC and Cu–Cz complexes. − ,, Dihedral angles between ligand planes are in the range between 1–16° and lead to a near parallel orientation of 2p orbitals on C NHC and N Cz . This geometric arrangement, in light of the close distance between these 2p orbitals on the ligated atoms (C NHC ···N Cz = 3.719(2)–3.762(2) Å), suggests that a long-range π interaction could be present across the metal center. , …”

“…This geometric arrangement, in light of the close distance between these 2p orbitals on the ligated atoms (C NHC ••• N Cz = 3.719(2)−3.762(2) Å), suggests that a long-range π interaction could be present across the metal center. 48,49 The electrochemical properties of the complexes and their precursors (carbene−CuCl) were examined by cyclic voltammetry and differential pulse voltammetry in acetonitrile solution (Table 1). The redox potentials are referenced to an internal ferrocene (Fc + /Fc) couple, and converted to HOMO and LUMO energies.…”

Eliminating nonradiative decay in Cu(I) emitters: >99% quantum efficiency and microsecond lifetime

“…The nature of the frontier molecular orbitals and coplanar orientation of the ligands allow for a simplified representation of the valence structure ( Fig. 1D) as a donor-bridge-acceptor linear system, wherein the metal d orbitals act as a weak electronic bridge between the parallel donor (N amide 2p z ) and acceptor (C carbene 2p z ) orbitals, thereby illustrating the potential for long-range p interaction (33,34). The ground state of these complexes is marked by a large permanent dipole, m g~1 1.3 D, in close agreement with the report by Föller and Marian for an isoelectronic Au complex (35).…”