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Oxalate-bridged complexes of dimolybdenum and ditungsten supported by pivalate ligands: (tBuCO2)3M2(-O2CCO2)M2(O2CtBu)3. Correlation of the solid-state, molecular, and electronic structures with raman, resonance raman, and electronic spectral data

Bursten, B.E.; Chisholm, M.H.; Clark, R.J.H.; Firth, S.; Hadad, C.M.; MacIntosh, A.M.; ... Zaleski, J.M.; + view all (2002) Oxalate-bridged complexes of dimolybdenum and ditungsten supported by pivalate ligands: (tBuCO2)3M2(-O2CCO2)M2(O2CtBu)3. Correlation of the solid-state, molecular, and electronic structures with raman, resonance raman, and electronic spectral data. Journal of the American Chemical Society , 124 (12) pp. 3050-3063. 10.1021/ja011786j.

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Abstract

The compounds (tBuCO2)3M2(-O2CCO2)M2(O2CtBu)3 (M4OXA), where M = Mo or W, are shown by analysis of powder X-ray diffraction data to have extended lattice structures wherein oxygen atoms from the oxalate and pivalate ligands of one M4OXA molecule are linked to metal atoms of neighboring molecules. Raman, resonance Raman, electronic absorption (2-325 K in 2-MeTHF), and emission spectra are reported, together with corresponding spectra of the -O213C13CO2 isotopomers. To aid in the assignment, the Raman spectra of K2C2O4·H2O and K213C2O4·H2O have also been recorded. The visible region of the electronic spectra is dominated by intense, fully allowed MLCT transitions, M2 to oxalate *, which show pronounced thermochromism and extensive vibronic progressions associated with the oxalate ligand at low temperatures. With excitation into these charge-transfer bands, strong resonance enhancement is seen for Raman bands assigned to the oxalate 1(ag) and, to a lesser extent, 2(ag) modes. Electronic structure calculations for the model compounds (HCO2)3M2(-O2CCO2)M2(O2CH)3, employing density functional theory (gradient corrected and time-dependent) with the Gaussian 98 and ADF 2000 packages, predict the planar oxalate D2h configuration to be favored, which maximizes M2 to oxalate * back-bonding, and indicate low barriers (<8 kcal mol-1) to rotation about the oxalate C-C bonds.

Type:Article
Title:Oxalate-bridged complexes of dimolybdenum and ditungsten supported by pivalate ligands: (tBuCO2)3M2(-O2CCO2)M2(O2CtBu)3. Correlation of the solid-state, molecular, and electronic structures with raman, resonance raman, and electronic spectral data
DOI:10.1021/ja011786j
Publisher version:http://dx.doi.org/10.1021/ja011786j
Language:English
Additional information:Please see article for missing diagram from abstract.
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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