A Homoleptic Molybdenum(IV) Enolate Complex:  Synthesis, Molecular and Electronic Structure, and NCN Group Transfer To Form a Terminal Cyanoimide of Molybdenum(VI)

• Published in: Journal of the American Chemical Society Vol. 126; no. 36; pp. 11370 - 11376
• Main Authors: Soo, Han Sen, Figueroa, Joshua S, Cummins, Christopher C
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 15.09.2004; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Condensed matter: structure, mechanical and thermal properties; Coordination compounds; Exact sciences and technology; Inorganic chemistry and origins of life; Inorganic compounds; Metal complexes; Physical Sciences; Physics; Preparations and properties; Science & Technology; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; LOCALIZATION; MONOMERIC TUNGSTEN(IV) PHENOXIDE; ENERGY; ACTIVATION; APPROXIMATION; SUSCEPTIBILITY; REACTIVITY; CRYSTAL; BOND; SOLID-STATE; Electronic structure; Alkoxy complex; Molecular structure; Electron charge distribution; Inorganic synthesis; Transition metal Complexes; Electron localization; X ray diffraction; Molybdenum Complexes; Crystalline structure
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0472533

A monomeric molybdenum(IV) tetrakis enolate complex Mo(OC[Ad]Mes)4, 1, where Ad = 2-adamantylidene and Mes = 2,4,6-Me3C6H2, has been synthesized and characterized structurally by X-ray diffraction, chemically through NCN group-transfer reactivity, and computationally to investigate the origins of the observed structure that is intermediate between tetrahedral and square planar. No prior examples of Mo(OR)4 have been structurally characterized despite having been the subject of both experimental and theoretical interest. Complex 1 has a singlet ground state and thus a metal-based lone pair of electrons. The latter has been visualized with the aid of the electron localization function (ELF) and appears as a two-bladed propeller with D 2 d symmetry. Complex 1 makes a simple 1:1 adduct with t-BuNC that is trigonal bipyramidal with an axial isocyanide as demonstrated by X-ray crystallography. This trigonal bipyramidal 1:1 adduct has a triplet ground state and provides a model for the way in which 1 interacts with NCN group donor dbabhCN prior to NCN group transfer to form the terminal cyanoimide complex 1-NCN. The calculated Mo−N bond dissociation enthalpy for 1-NCN is 104 kcal mol-1, 30 kcal mol-1 greater than that for the corresponding dissociation of NCN from cyanophosphiniminato NCNPMe3.