Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors.

Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors. Research Abstract Details 

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Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors. Abstract Text:

Anasuya Sanyal,Sudipta Chatterjee,Alfonso ,Biprajit Sarkar,Priti Singh,Jan Fiedler,Stanislav ,Wolfgang Kaim,Sreebrata Goswami,Anasuya Sanyal,Sudipta Chatterjee,Alfonso ,Biprajit Sarkar,Priti Singh,Jan Fiedler,Stanislav ,Wolfgang Kaim,Sreebrata Goswami,Anasuya Sanyal,Sudipta Chatterjee,Alfonso ,Biprajit Sarkar,Priti Singh,Jan Fiedler,Stanislav ,Wolfgang Kaim,Sreebrata Goswami,Anasuya Sanyal,Sudipta Chatterjee,Alfonso ,Biprajit Sarkar,Priti Singh,Jan Fiedler,Stanislav ,Wolfgang Kaim,Sreebrata Goswami,

The homoleptic diamagnetic complexes M(mer-L)(2), M = Cr, Mo,W (1a,b, 2a,b, and 4a,b), were obtained by reacting the hexacarbonyls M(CO)(6) with the tridentate ligands 2-[(2-N-arylamino)phenylazo]pyridine (HL = NH(4)C(5)N=NC(6)H(4)N(H)C(6)H(4)(H) (HL(a)) or NH(4)C(5)N=NC(6)H(4)N(H)C(6)H(4)(CH(3)) (HL(b))) in refluxing n-octane. In the case of M = Mo, the dinuclear compounds [Mo(L)(pap)](2)(mu-O) (3a,b) (pap = 2-(phenylazo)pyridine), were obtained as second products in moist solvent. X-ray diffraction analysis for Cr(L(b))(2) (1b), Mo(L(a))(2) (2a), and W(L(a))(2) (4a) reveals considerably distorted-octahedral structures with trans-positioned azo-N atoms and cis-positioned 2-pyridyl-N and anilido nitrogen atoms. Whereas the N(azo)-M-N(azo) angle is larger than 170 degrees, the other two trans angles are smaller, at about 155 degrees (M = Cr, 1b) or 146 degrees (M = Mo, W; 2a, 4a), due to the overarching bite of the mer-tridentate ligands. The bonds from M to the neutral 2-pyridyl-N atoms are distinctly longer by more than 0.08 A than those to the anilido or azo nitrogen atoms, reflecting negative charge on the latter. The N-N bond distances vary between 1.339(2) A for 1b and 1.373(3) A for 4a, clearly indicating the azo radical anion oxidation state. Considering the additional negative charge on anilido-N, the mononuclear complexes are thus formulated as M(IV)(L*(2-))(2). The diamagnetism of the complexes as shown by magnetic susceptibility and (1)H NMR experiments is believed to result from spin-spin coupling between the trans-positioned azo radical functions, resulting in a singlet diradical situation. The experimental structures are well reproduced by density functional theory calculations, which also support the overall electronic structure indicated. The dinuclear 3a with N-N distances of 1.348(10) A for L(a) and 1.340(9) A for pap is also formulated as an azo anion radical-containing molybdenum(IV) species, i.e., [Mo(IV)(L*(2-))(pap*-)](2)(mu-O). All compounds can be reversibly reduced; the Cr complexes 1a,b are also reversibly oxidized in two steps. Electron paramagnetic resonance spectroscopy indicates metal-centered spin for 1a+ and 1a- and g approximately 2 signals for 2a-, 3a+, 3a-, and 4a-. Spectroelectrochemistry in the UV-vis-NIR region showed small changes for the reduction of 2a, 3a, and 4a but extensive spectral changes for the reduction and oxidation of 1a.

Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors. Publishing Authors By Initials

A Sanyal,S Chatterjee,A ,B Sarkar,P Singh,J Fiedler,S ,W Kaim,S Goswami,A Sanyal,S Chatterjee,A ,B Sarkar,P Singh,J Fiedler,S ,W Kaim,S Goswami,A Sanyal,S Chatterjee,A ,B Sarkar,P Singh,J Fiedler,S ,W Kaim,S Goswami,A Sanyal,S Chatterjee,A ,B Sarkar,P Singh,J Fiedler,S ,W Kaim,S Goswami,

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Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: Inorganic chemistry

VOLUME: 46

Page Numbers: 8584-93

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ISSN: 0020-1669

DAY: 22

MONTH: 09

YEAR: 2007

Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors. Information

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LANGUAGE: eng

NlmUniqueID: 366543

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Grant and Affiliation Information for Singlet diradical complexes of chromium, molybdenum, and tungsten with azo anion radical ligands from M(CO)6 precursors.

AFFILIATION: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India.

Country: United States

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MEDLINETA: Inorg Chem

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