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Investigation of metal-dithiolate fold angle effects: implications for molybdenum and tungsten enzymes.

ABSTRACT: Gas-phase photoelectron spectroscopy and density functional theory have been used to investigate the interactions between the sulfur pi-orbitals of arene dithiolates and high-valent transition metals as minimum molecular models of the active site features of pyranopterin MoW enzymes. The compounds (Tp*)MoO(bdt) (compound 1), Cp(2)Mo(bdt) (compound 2), and Cp(2)Ti(bdt) (compound 3) [where Tp* is hydrotris(3,5-dimethyl-1-pyrazolyl)borate, bdt is 1,2-benzenedithiolate, and Cp is eta(5)- cyclopentadienyl] provide access to three different electronic configurations of the metal, formally d(1), d(2), and d(0), respectively. The gas-phase photoelectron spectra show that ionizations from occupied metal and sulfur based valence orbitals are more clearly observed in compounds 2 and 3 than in compound 1. The observed ionization energies and characters compare very well with those calculated by density functional theory. A "dithiolate-folding-effect" involving an interaction of the metal in-plane and sulfur-pi orbitals is proposed to be a factor in the electron transfer reactions that regenerate the active sites of molybdenum and tungsten enzymes.

SUBMITTER: Joshi HK

PROVIDER: S-EPMC152988 | biostudies-literature | 2003 Apr

REPOSITORIES: biostudies-literature

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Investigation of metal-dithiolate fold angle effects: implications for molybdenum and tungsten enzymes.

Joshi Hemant K HK Cooney J Jon A JJ Inscore Frank E FE Gruhn Nadine E NE Lichtenberger Dennis L DL Enemark John H JH

Proceedings of the National Academy of Sciences of the United States of America 20030324 7

Gas-phase photoelectron spectroscopy and density functional theory have been used to investigate the interactions between the sulfur pi-orbitals of arene dithiolates and high-valent transition metals as minimum molecular models of the active site features of pyranopterin MoW enzymes. The compounds (Tp*)MoO(bdt) (compound 1), Cp(2)Mo(bdt) (compound 2), and Cp(2)Ti(bdt) (compound 3) [where Tp* is hydrotris(3,5-dimethyl-1-pyrazolyl)borate, bdt is 1,2-benzenedithiolate, and Cp is eta(5)- cyclopentad ...[more]

PMID: 12655066

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Project description:New square-pyramidal bis(ene-1,2-dithiolate)MoSe complexes, [Mo(IV)Se(L)(2)](2-), have been synthesised along with their terminal sulfido analogues, [Mo(IV)S(L)(2)](2-), using alkyl (L(C(4)H(8))), phenyl (L(Ph)) and methyl carboxylate (L(COOMe)) substituted dithiolene ligands (L). These complexes now complete three sets of Mo(IV)O, Mo(IV)S and Mo(IV)Se species that are coordinated with identical ene-1,2-dithiolate ligands. The [alkyl substituted Mo(S/Se)(L(C(4)H(8)))(2)](2-) complexes were reported in prior investigations (H. Sugimoto, T. Sakurai, H. Miyake, K. Tanaka and H. Tsukube, Inorg. Chem. 2005, 44, 6927, H. Tano, R. Tajima, H. Miyake, S. Itoh and H. Sugimoto, Inorg. Chem. 2008, 47, 7465). The new series of complexes enable a systematic investigation of terminal chalcogenido and supporting ene-1,2-dithiolate ligand effects on geometric structure, electronic structure, and spectroscopic properties. X-ray crystallographic analysis of these (Et(4)N)(2)[MoEL(2)] (E = terminal chalocogenide) complexes reveals an isostructural Mo centre that adopts a distorted square pyramidal geometry. The M?E bond distances observed in the crystal structures and the ?(M?E) vibrational frequencies indicate that these bonds are weakened with an increase in L?Mo electron donation (L(COOMe) < L(Ph) < L(C(4)H(8))), and this order is confirmed by an electrochemical study of the complexes. The (77)Se NMR resonances in MoSeL complexes appear at lower magnetic fields as the selenido ion became less basic from MoSeL(C(4)H(8)), MoSeL(Ph) and MoSeL(COOMe). Electronic absorption and resonance Raman spectroscopies have been used to assign key ligand-field, MLCT, LMCT and intraligand CT bands in complexes that possess the L(COOMe) ligand. The presence of low-energy intraligand CT transition in these MoEL(COOMe) compounds directly probes the electron withdrawing nature of the -COOMe substituents, and this underscores the complex electronic structure of square pyramidal bis(ene-1,2-dithiolate)-Mo(IV) complexes that possess extended dithiolene conjugation.

Dataset Information

Investigation of metal-dithiolate fold angle effects: implications for molybdenum and tungsten enzymes.

Publications

Investigation of metal-dithiolate fold angle effects: implications for molybdenum and tungsten enzymes.

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