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Microwave spectra, ab initio and DFT calculations and molecular structure for (η7-cycloheptatriene)Ti(η5-cyclopentadienyl) and (η7-cycloheptatriene)Cr(η5-cyclopentadienyl)

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Title: Microwave spectra, ab initio and DFT calculations and molecular structure for (η7-cycloheptatriene)Ti(η5-cyclopentadienyl) and (η7-cycloheptatriene)Cr(η5-cyclopentadienyl)
Authors: Daly, Adam M.1, Lavin, Catherine M.1, Weidenschilling, Erika S., Holden, Alison M., Kukolich, Stephen G. kukolich@u.arizona.edu
Source: Journal of Molecular Spectroscopy. May2011, Vol. 267 Issue 1/2, p172-177. 6p.
Subjects: Microwave spectroscopy, Molecular structure, Cyclic compounds, Organometallic compounds, Titanium compounds, Molecular rotation, Density functionals
Abstract: Abstract: Microwave spectra of 1-d-(η7-cycloheptatriene)48Ti(η5-cyclopentadienyl) (CHT–Ti–Cp) and two singly substituted 13C isotopomers were measured and gas phase structural parameters were determined. Rotational transitions were also measured for (η7-cycloheptatriene)52Cr(η5-cyclopentadienyl). Rotational constants for the Ti complex were found to be A =1720(4)MHz, B =769.269(1)MHz and C =766.131(1)MHz and for [13CC6H7–48Ti–C5H5], A =1773(2)MHz, B =769.6931(4)MHz and C =761.1789(5)MHz and for [1-d-C7H6 48TiC5H5] and A =1270(5)MHz, B =767.0142(9)MHz and C =765.323(1)MHz for [C7H7 48Ti13CC4H5]. A structural analysis for the (CHT–Ti–Cp) data showed that the cycloheptatriene ring protons droop towards titanium as predicted by DFT and MP2 calculations. The droop of the protons toward the metal was experimentally determined to be 8.0(2)° out of the plane of the cycloheptatriene ring. The ring center distance to titanium was found to be 2.01(3)Å for Ti–Cp and 1.48(3)Å for Ti–CHT using a least squares fit to the measured rotational constants and fixing many of the structural parameters to the calculated values. The spectrum of the normal isotopomer (η7-cycloheptatriene)Ti(η5-cyclopentadienyl) was re-measured and a discussion of the possible 47Ti quadrupole coupling constants is presented. The chromium analog K =0 spectrum was analyzed to obtain B =851.229MHz, and D J =0.028(6)kHz. Results from structure calculations are reported and discussed for (CHT–M–Cp) complexes with M=Ti, Cr, Zr, Hf, Mo, W using MP2, B3PW91 and B3LYP methods. [Copyright &y& Elsevier]
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Abstract:Abstract: Microwave spectra of 1-d-(η7-cycloheptatriene)48Ti(η5-cyclopentadienyl) (CHT–Ti–Cp) and two singly substituted 13C isotopomers were measured and gas phase structural parameters were determined. Rotational transitions were also measured for (η7-cycloheptatriene)52Cr(η5-cyclopentadienyl). Rotational constants for the Ti complex were found to be A =1720(4)MHz, B =769.269(1)MHz and C =766.131(1)MHz and for [13CC6H7–48Ti–C5H5], A =1773(2)MHz, B =769.6931(4)MHz and C =761.1789(5)MHz and for [1-d-C7H6 48TiC5H5] and A =1270(5)MHz, B =767.0142(9)MHz and C =765.323(1)MHz for [C7H7 48Ti13CC4H5]. A structural analysis for the (CHT–Ti–Cp) data showed that the cycloheptatriene ring protons droop towards titanium as predicted by DFT and MP2 calculations. The droop of the protons toward the metal was experimentally determined to be 8.0(2)° out of the plane of the cycloheptatriene ring. The ring center distance to titanium was found to be 2.01(3)Å for Ti–Cp and 1.48(3)Å for Ti–CHT using a least squares fit to the measured rotational constants and fixing many of the structural parameters to the calculated values. The spectrum of the normal isotopomer (η7-cycloheptatriene)Ti(η5-cyclopentadienyl) was re-measured and a discussion of the possible 47Ti quadrupole coupling constants is presented. The chromium analog K =0 spectrum was analyzed to obtain B =851.229MHz, and D J =0.028(6)kHz. Results from structure calculations are reported and discussed for (CHT–M–Cp) complexes with M=Ti, Cr, Zr, Hf, Mo, W using MP2, B3PW91 and B3LYP methods. [Copyright &y& Elsevier]
ISSN:00222852
DOI:10.1016/j.jms.2011.03.013