Article

63Cu NMR Study of Copper(I) Carbonyl Complexes with Various Hydrotris(pyrazolyl)borates:  Correlation between 63Cu Chemical Shifts and CO Stretching Vibrations

Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226, Japan, and Institute for Life Support Technology, Yamagata Technopolis Foundation, 2-2-1 Matsuei, Yamagata 990, Japan
Inorg. Chem., 1998, 37 (12), pp 3066–3070
DOI: 10.1021/ic970138r
Publication Date (Web): May 20, 1998
Copyright © 1998 American Chemical Society

Synopsis

Sharp 63Cu NMR signals are observed for copper(I) carbonyl complexes with hydrotris(pyrazolyl)borate ligands. Their chemical shifts correlate with the electron density at the copper center, which is supported by the good correlation between the δ(63Cu) value and C⋮O stretching vibration. 63Cu NMR measurement may be a potential tool to provide the electronic state of the copper center.

Abstract

Abstract Image

Copper(I) carbonyl complexes with a series of hindered LR1,R2 ligands (L:  hydrotris(pyrazolyl)borate, R1 and R2 are substituents at the 3- and 5-positions of the pyrazole ring, respectively), LR1,R2CuCO [R1, R2 = Me, Me (1), i-Pr, i-Pr (2), t-Bu, Me (3), t-Bu, i-Pr (4), Ph, i-Pr (5), Ph, Ph (6)] have been synthesized and characterized by 1H NMR and IR spectroscopy and elemental analysis. The molecular structures of 3 and 6 have been determined by X-ray crystallography. The electronic structures of copper(I) sites are characterized by means of 63Cu NMR spectroscopy and by the C⋮O stretching vibration. The sharp 63Cu NMR signals are observed for LR1,R2CuCO complexes in toluene at room temperature. The 63Cu NMR signals of copper(I) complexes with alkyl-substituted ligands (14) are observed in lower field than those of the phenyl derivatives (5, 6) correlating with the electron-density at the copper center. This argument is supported by the good correlation between the δ(63Cu) value and C⋮O stretching vibration which is a sensitive indicator of the extent of back-donation of the Cu d electrons to the antibonding C⋮O orbitals.

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Article Views: 549 Times
Received 6 February 1997
Published online 20 May 1998
Published in print 1 June 1998
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