Salts of a copper and a silver carbene complex were prepared from dimesityl diazomethane, made possible by the steric shielding of the N-heterocyclic carbene (NHC) ancillary ligand IPr**. The mint-green complex [IPr**Ag=CMes2 ](+) [NTf2 ](-) is the first isolated silver carbene complex without heteroatom donor substituents. Single-crystal X-ray diffraction provides evidence for a predominant carbenoid character, and supports the postulation of such reactive species as intermediates in silver-catalyzed C-H activation reactions. The greenish yellow copper carbene complex [IPr**Cu=CMes2 ](+) [NTf2 ](-) has spectroscopic properties in between the isostructural silver complex and the already reported emerald green gold carbene complex. A comparison in the Group 11 series indicates that relativistic effects are responsible for the strong σ bond and the significant π back-bonding in the gold carbene moiety.

À liegen zwischen denen des isostrukturellen Silberkomplexes und denen des schon beschriebenen smaragdgrünen Goldcarben-Komplexes.E in Vergleichd er Elemente der Kupfertriade weist darauf hin, dass relativistische Effekte für die starke s-Bindung und die signifikante pRückbindung in der Goldcarben-Einheit verantwortlichs ind.

Aether liislich. In seinem Verhalten gegen chemische Agentien zeichnet es sich durch grosse Bestandigkeit aus.Die freie Base wie die Salze wirken in den verdiinntesten Lijsungen heftig brennend auf die ernpfindlicheren Theile d r r Haut; besonders die Schlein. &Ute werden Btark angcgriffen. Der Staub derselben in geringster Menge eingeathmet, verursacht einen starken Reiz zurn Niesen.Die Analyse der Base fiihrt zur Formel Cl2H,N.

No abstract

…the carbenoid character of isostructural Group 11 metal carbene complexes increases in the order Au ! Cu < Ag as shown by B. F. Straub et al. in their Communication on page 10331 ff.The silver snow leopard breaking abar of its cage symbolizes the marginal silver-to-carbene back-bonding and the high carbenoid character. Thee scaping copper lynx shows the short lifetime of the copper carbene complex. Thegold tiger symbolizes the remarkable stability of the gold carbene complex. The" E= mc 2 "r efers to the relativistic effects in golds valence shell.