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Dimolybdenum bis((S,S,S)-triisopropanolaminate(3-)): A blue compound with an unusual Mo-Mo triple bonds

Chisholm, MH; Macintosh, AM; Huffman, JC; Wu, DD; Davidson, ER; Clark, RJH; Firth, S; (2000) Dimolybdenum bis((S,S,S)-triisopropanolaminate(3-)): A blue compound with an unusual Mo-Mo triple bonds. Inorganic Chemistry , 39 (16) 3544 - 3550.

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Abstract

Mo-2((OBu)-Bu-t)(6) and Mo-2(NMe2)(6) each react with (S,S,S)- triisopropanslamine (2 equiv) in benzene to yield dimolybdenum bis((S,S,S)-isopropanolaminate(3-)), Mo-2[(OC-(S)- HMeCH2)(3)N](2) (M equivalent to M), as a blue crystalline solid. Cell parameters at -160 degrees C: a =17.389(6) Angstrom, b = 10.843(3) Angstrom, c = 10.463(3) Angstrom, beta = 125.28(1)degrees, Z = 2 in space group C2. The molecular structure involves an Mo-2 unit inside an O6N2 distorted cubic box. The Mo-2 axis is disordered about three positions with occupancy factors of ca. 45%, 45% and 10%. Despite this disorder, the molecular structure is shown to contain a central Mo equivalent to Mo unit of distance 2.15(3) A coordinated to two triolate ligands which each have two chelating arms and one;that spans the Mo equivalent to Mo bond. The local Mo2O6N2 moiety has approximate C-2h symmetry, and the Mo-N distances are long, 2.4 Angstrom. The H-1 and C-13{H-1} NMR spectra recorded in benzene-d(6) are consistent with the geometry found in the solid-state structure. The blue color arises from weak absorptions, epsilon similar to 150 dm(3) mol(-1) cm(-1), at 580 and 450 nm in the visible region of the electronic absorption spectrum: Raman spectra recorded in KCl reveal pronounced resonance effects with excitation wavelengths of 488.0, 514.5, and 568.2 nm, particularly for the 322 cm(-1) band, which can probably be assigned to v(Mo equivalent to Mo). The electronic structure of this compound is. investigated by B3LYP DFT calculations, and a comparison is made with the more typical ethane-like (D-3d) Mo-2(OR)(6) compounds is presented. The distortion imposed on the molecule by the triisopropanolaminate(3-) ligands removes the degeneracy of the M-M pi molecular orbitals. The HOMO and SHOMO are both M-M pi and M-O sigma* in character, while the LUMO is M-M pi* and-the SLUMO is predominantly M-O sigma* with metal sp character. The calculated Single;-singlet transition energies are compared with those implicit in the observed electronic spectrum

Type:Article
Title:Dimolybdenum bis((S,S,S)-triisopropanolaminate(3-)): A blue compound with an unusual Mo-Mo triple bonds
Additional information:Journal Article AUG 7 343TN Chisholm MH Indiana Univ, Dept Chem, Bloomington, IN 47405 USA INORG CHEM
Keywords:absorption, ALKOXIDES, ARM, As, BENZENE, BOND, BONDS, cell, chemistry, comparison, D(3)-D(3) DIOLATE COMPLEXES, DISORDER, Distance, effects, ELECTRONIC-STRUCTURE, energy, Excitation, factors, Geometry, H1, HOMOLOGS, LIGAND, ligands, local, LONG, METAL, METAL- METAL, MH, MM, Molecular, Molecular Structure, MOLECULAR-STRUCTURE, MOLYBDENUM, MULTIPLE BONDS, NMR, PARAMETER, PARAMETERS, POSITION, REGION, resonance, RESONANCE-RAMAN-SPECTRA, Space, SPECTRA, SPECTRUM, STRUCTURAL CHARACTERIZATION, Structure, SYMMETRY, transition, TUNGSTEN, USA
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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