Electronic structure and spectroscopy of the cycloheptatrienyl molybdenum halide complexes [MoBrL2(η-C7H7)]n + (L2 = 2CO, n = 0; L2 = 2,2′-bipyridyl, n = 0 or 1)

K.A.E. Roberts, N.J. Brown, H.N. Roberts, J.J.W. Mcdouall, Paul Low, M.W. Whiteley

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Abstract

© 2014 Elsevier Ltd. All rights reserved. DFT calculations at the B3LYP/Def2-SVP level have been conducted on the half-sandwich cycloheptatrienyl molybdenum complexes [Mo(CO)3(η-C7H7)]+, [1]+ and [MoBrL2(η-C7H7)]n + (L2 = 2 CO, n = 0, 2; L2 = bpy, n = 0, 3; L2 = bpy, n = 1, [3]+; bpy = 2,2′-bipyridyl). In all cases, strong δ-bonding interactions operate between the e2 level of the C7H7 ring and metal dxy and d x2-y2 orbitals resulting in a metal-centred HOMO with substantial d z2 character in the 18-electron, closed shell systems. The experimental electronic UV-Vis spectra of [1]+, 2 and 3 are accurately reproduced by TD-DFT methods. For complexes 2 and 3, assignments made with the assistance of calculated spectra indicate that absorptions in the region 390-770 nm originate from a series of MLCT (metal-ligand charge transfer) or ILCT (inter-ligand charge transfer) transitions in which carbonyl, C7H7 and 2,2′-bipyridyl ligands act as acceptor systems from the metal or mixed metal and bromide donor groups. The metal-centred, one-electron oxidation of 3 to 3[PF6] results in almost complete quenching of the visible region MLCT/ILCT absorptions of 3 and replacement with weak transitions probably arising from bromide to metal LMCT (ligand to metal charge transfer) processes.
Original languageEnglish
Pages (from-to)89-97
JournalPolyhedron
Volume86
DOIs
Publication statusPublished - Jan 2015

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