Homoleptic Permethylpentalene Complexes: “Double Metallocenes” of the First-Row Transition Metals

Ashley, Andrew E., Cooper, Robert T., Wildgoose, Gregory, Green, Jennifer C. and O’Hare, Dermot (2008) Homoleptic Permethylpentalene Complexes: “Double Metallocenes” of the First-Row Transition Metals. Journal of the American Chemical Society, 130 (46). pp. 15662-15677. ISSN 0002-7863

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The synthesis of the bimetallic permethylpentalene complexes Pn*2M2 (M = V, Cr, Mn, Co, Ni; Pn* = C8Me6) has been accomplished, and all of the complexes have been structurally characterized in the solid state by single-crystal X-ray diffraction. Pn*2V2 ( 1 ) and Pn*2Mn2 ( 3 ) show very short intermetallic distances that are consistent with metal-metal bonding, while the cobalt centers in Pn*2Co2 ( 4 ) exhibit differential bonding to each side of the Pn* ligand that is consistent with an ?5:?3 formulation. The Pn* ligands in Pn*2Ni2 ( 5 ) are best described as ?3:?3-bonded to the metal centers. 1H NMR studies indicate that all of the Pn*2M2 species exhibit D2h molecular symmetry in the solution phase; the temperature variation of the chemical shifts for the resonances of Pn*2Cr2 ( 2 ) indicates that the molecule has an S = 0 ground state and a thermally populated S = 1 excited state and can be successfully modeled using a Boltzmann distribution (?H° = 14.9 kJ mol-1 and ?S° = 26.5 J K-1 mol-1). The solid-state molar magnetic susceptibility of 3 obeys the Curie-Weiss law with µeff = 2.78µB and ? = -1.0 K; the complex is best described as having an S = 1 electronic ground state over the temperature range 4-300 K. Paradoxically, attempts to isolate the “double ferrocene” equivalent, Pn*2Fe2, led only to the isolation of the permethylpentalene dimer Pn*2 ( 6 ). Solution electrochemical studies were performed on all of the organometallic compounds; 2-5 exhibit multiple quasi-reversible redox processes. Density functional theory calculations were performed on this series of complexes in order to rationalize the observed structural and spectroscopic data and provide estimates of the M-M bond orders.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Related URLs:
Depositing User: Rachel Smith
Date Deposited: 29 Mar 2011 16:21
Last Modified: 21 Apr 2020 17:50
URI: https://ueaeprints.uea.ac.uk/id/eprint/27486
DOI: 10.1021/ja8057138

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