Two Amphoteric Silver Carbene Clusters

Abstract

Two highly labile silver carbene cluster complexes are described, which are unique in that they mark the transition point at which the carbene center transmutes from a fairly common NHC‐like nucleophilic behavior to an electrophilic character befitting reactive silver carbene intermediates of relevance in various catalytic transformations. This amphoteric character is the distinguishing attribute of a μ‐bridged donor/donor carbene entity that connects two silver atoms of triangular or tetrahedral metallic core units.

Gold Difluorocarbenoid Complexes: Spectroscopic and Chemical Profiling

“…These data suggest that difluorocarbene complexes of type A are likely at the edge of being observable. [22] This supposition is in line with aprevious study which showed that treatment of compound 6 with BF 3 ·Et 2 Os olely afforded the carbonyl complex 8 (Scheme 1). [23] Thet ransient gold difluoro-carbene species 7,a st he likely intermediate of this reaction, could not be detected by 19 FNMR at À80 8 8C; hydrolysis must be extremely fast even under such notably mild conditions.…”

Alkyne gem‐Hydrogenation: Formation of Pianostool Ruthenium Carbene Complexes and Analysis of Their Chemical Character

“…It is important to recognize, however, that this terminology denotes only the extremes of a continuum: it is not necessarily intuitive by looking at the molecular structure to which category a given metal carbene complex may belong. The famous Grubbs catalysts, which have revolutionized the practice of olefin metathesis, may perhaps be cited in this context …”

Alkyne gem‐Hydrogenation: Formation of Pianostool Ruthenium Carbene Complexes and Analysis of Their Chemical Character

“…Thef amous Grubbs catalysts,w hich have revolutionized the practice of olefin metathesis,may perhaps be cited in this context. [6][7][8][9][10] Pianostool ruthenium complexes of type D are isoelectronic with Grubbs carbenes.Although such species had been invoked as reactive intermediates in an umber of different transformations including cyclopropanation, [11,12] little was known about structure and bonding until very recently.O ur current interest was invigorated by the finding that carbenes of this type can be generated by gem-hydrogenation of ordinary alkynes using [Cp*RuCl] 4 as the catalyst. [13,14] This unorthodox transformation, in which both H-atoms of H 2 are delivered to one and the same C-atom of the triple bond, has no precedent in the classical canon of homogeneous catalysis; it constitutes the early phase of areaction pathway that allows alkynes to be converted into E-alkenes H by trans-selective semi-reduction (Scheme 1).…”