Experimental evaluation of the electron donor ability of a gold phosphine fragment in a gold carbene complex

Abstract

X-ray analysis of the gold cyclopropyl(methoxy)carbene complex [(P)AuC(OMe)(c-Pr)](+) SbF6(-) [P = P(t-Bu)2o-biphenyl] and comparison to extant protonated cyclopropyl ketones indicates that electron donation from the (P)Au fragment to the electron-deficient C1 atom is similar to that provided by a cyclopropyl group.

Quantitative assessment of the carbocation/carbene character of the gold–carbene bond

“…16 If L contains at least one symmetry plane, the whole complex can be conveniently constrained to C s symmetry, using the carbene plane as the symmetry plane, without any significant change of the geometrical parameters of S. In fact, the d C 1 C 2 and Δd parameters derived from constrained and unconstrained optimizations are practically identical (see Fig. Such a geometrical arrangement well resembles the solid-state structure of [(JP)AuS] + .…”

“…We consider here different phosphines, such as the ligand used in the Widenhoefer's paper 16 (JP), including aromatic (PPh 3 ), aliphatic (PCy 3 ), fluorinated (PAr F ) 24 and dicationic (ACPP) ones. We consider here different phosphines, such as the ligand used in the Widenhoefer's paper 16 (JP), including aromatic (PPh 3 ), aliphatic (PCy 3 ), fluorinated (PAr F ) 24 and dicationic (ACPP) ones.…”

“…11 In particular, we recently synthesized a series of ten [LAu-NAC] 0/+ complexes, having a pyrrolidine moiety bound to the carbenic carbon. 16 According to previous theoretical work, 17 they related the distortion of a cyclopropyl ring with the electron density at the C 1 , assuming that the electronic structure of [(JP)AuS] + can be seen as a combination of the Valence Bond (VB) limit resonance structures R1-3 (Scheme 2). 12 A recent contribution to the debate on the carbocationic/ carbene nature of the Au-C bond [13][14][15] has come from work by Brooner and Widenhoefer, who reported the synthesis and X-ray crystal structure of a gold cyclopropyl(methoxy)carbene complex [(JP)AuS] + SbF 6 − [JP = P(t-Bu) 2 (o-biphenyl), S = C(OMe)-(c-Pr)].…”

Isolierung eines nicht‐Heteroatom‐stabilisierten Goldcarbens

“…Strukturell charakterisierte Goldcarben-Komplexe mit überwiegendem Iminio-Ylid-(linke Seite), [2a, 3] Oxonio-Ylid-(Mitte links und Mitte rechts) [4,5] und phenylogem Oxonio-Ylid-Ligandcharakter (rechte Seite). [5] Das 13 C{ 1 H}-NMR-Spektrum unterstreicht den deutlichen Unterschied des Iminio-Ylid-ähnlichen N-heterocyclischen Carbenliganden mit einer chemischen Verschiebung von d = 185.1 ppm und dem Carbenliganden mit einem Signal bei d = 321.3 ppm (Abbildung 3). Ohne p-Rückbindung sollte die Au-CMes 2 -Bindung also länger sein.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…Use of triphenylarsine as a ligand additive allowed for a significant catalyst load M a n u s c r i p t 149 reduction for various enyne cycloisomerization processes [1176]. The carbocation stabilizing ability of a phosphine-gold fragment was estimated to be better than that of a methyl or phenyl group and similar to a cyclopropyl group based on the analysis of structural effects for cyclopropylcarbene gold complexes, a commonly proposed intermediate in many of these transformations [1177]. A computational study of enyne cycloisomerization using alkyne-alkene groups connected through silicon was also reported [1178].…”