A C-13 and N-15 Solid-State NMR Study of Structural Disorder and Aurophilic Bonding in Au-I and Au-III Cyanide Complexes

作者：Harris Kristopher J; Wasylishen Roderick E^*

来源：Inorganic Chemistry, 2009, 48(5): 2316-2332.

DOI：10.1021/ic8022198

Solid-state nuclear magnetic resonance has been used to study several cyanoaurates. Carbon-13 and nitrogen-15 NMR spectra of samples enriched with isotopically labeled C-13, N-15 cyanide ligands were recorded for stationary samples and samples spinning at the magic angle. Several salts of the dicyanoaurate (1) anion, M[Au(CN)(2)], where M = n-butylammonium, potassium, and thallium, were studied via solid-state NMR. A gold(III) cyanide, K[Au(CN)(4)], was also investigated. Carbon-13 and nitrogen-15 chemical shift tensors are reported for each salt, as are the measured C-13, N-15 direct dipolar coupling constants together with the related derived cyanide bond lengths, r(C,N). The value for r(C,N) in [(n-C4H9)(4)N][Au(CN)(2)], 1.17(5) angstrom, was determined to be more realistic than a previously reported X-ray diffraction value of 1.03(4) angstrom. Large C-13 NMR line widths from TI[Au(CN)(2)], 250-315 Hz, are attributed to coupling with Au-197 (I = 3/2) and/or (TI)-T-203/205 (I = 1/2), as confirmed by measurements of the transverse relaxation constant, T-2. Investigation of the carbon-13 chemical shifts for cyanide ligands bound to gold involved in a variety of metallophilic bonding environments demonstrates that the chemical shift is sensitive to metallophilic bonding. Differences in Au-TI metallophilic bonding are shown to cause a difference in the isotropic carbon-13 chemical shift of up to 15.7 ppm, while differences in Au-Au aurophilic bonding are found to be responsible for a change of up to 5.9 ppm. The disordered polymeric material gold(I) monocyanide, AuCN, was also investigated using C-13 and N-15 SSNMR. Two-dimensional C-13, C-13 double-quantum dipolar-recoupling spectroscopy was used to probe connectivity in this material. The C-13 NMR site multiplicity in AuCN is explained on the basis of sensitivity of the carbon-13 chemical shift to aurophilic bonding of the directly bonded gold atom. This assignment allows estimation of the position of the linear [-M-CN-1](infinity) chain's position with respect to the neighboring polymer chain. For the samples studied, a range of 7 +/- 2% to 25 +/- 5% of the AuCN chains are found to be "slipped" instead of aligned with the neighboring chains at the metal position.

• 出版日期2009-3-2