Synthesis of Mixed NHC/L Platinum(II) Complexes:  Restricted Rotation of the NHC Group

Abstract

The use of (NHC)AgX salts as transmetallating agents for platinum can be tuned to introduce either one or two NHC ligands per platinum in high yield. Complexes with a single NHC ligand are prepared with an additional DMSO ligand, which can conVeniently be replaced by other ligands such as phosphines to giVe mixed cis NHC/phosphine complexes. Variable-temperature NMR and DFT haVe been used to probe the nature of the restricted rotation of the NHC ligand about the square planar platinum center: experimentally, the barrier has been established as at least 85 kJ mol -1 , and the computational Value has been determined to be 92 kJ mol -1 .

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

“…R ≠ R') two signals (each of relative integral three) are seen for the DMSO protons at room temperature, consistent with the plane of the NHC ligand being perpendicular to the coordination plane of the platinum, together with restricted rotation about the NHC-Pt bond. 25,27 Gentle heating of the new complexes 5a-c results in a C-H activation reaction of the phenyl ring, similar to that seen before. 26,28,29 Cyclometallated products 6a-c are now seen, presumably accompanied by the elimination of methane, Scheme 4.…”

“…Using our previously described methodology, 25 we can selectively introduce either one or two NHC ligands at a platinum centre, via silver complexes, Scheme 2. We had hoped that we could induce one or both of the complexes 3 or 4 to undergo a cyclometallation reaction, but we were unable to find suitable conditions and reagents to facilitate such transformations.…”

Synthesis, Structure, and Polymerization Activity of Cyclopentadienylnickel(II) N‐Heterocyclic Carbene Complexes: Selective Cross‐Metathesis in Metal Coordination Spheres

“…EI (70 eV) mass spectra were recorded with an AMD-604 spectrometer and ESI mass spectra with an ESI Mariner spectrometer. Unless otherwise noted, NMR spectra were recorded at ambient temperature with a Mercury 400BB spectrometer at 400 MHz for 1 H and at 101 MHz for 13 C with chemical shifts reported relative to the residual deuterated solvent. M w and M n of polymers were determined with a LabAlliance liquid chromatograph equipped with a Jorgi Gel DVB Mixed Bed column (250 mm ϫ 10 m) with thf (polystyrenes) or CHCl 3 (polyphenylacetylenes) as the mobile phase.…”

Anticancer Gold N‐Heterocyclic Carbene Complexes: A Comparative in vitro and ex vivo Study

“…[49][50][51] As am atter of fact, only one carbenic carbon signal at chemical shift typical of trans-bis(NHCs)PtX 2 complexes is present( d = 167.3 ppm). [48] The formation of the cis isomer can therefore be excluded, as it would have given ac arbenic carbon signal at significantly upfield shiftedc hemical shift as reported for similar compounds (d % 132-150 ppm). [52,53] The stability of gold compounds 3 and 4 was monitored by 1 HNMR spectroscopy of mixtures of water and [D 6 ]DMSO during 7d ays at room temperature.…”