Substitution Effects on the Formation of T‐Shaped Palladium Carbene and Thioketone Complexes from Li/Cl Carbenoids

Abstract

The preparation of palladium thioketone and T-shaped carbene complexes by treatment of thiophosphoryl substituted Li/Cl carbenoids with a Pd(0) precursor is reported. Depending on the steric demand, the anion-stabilizing ability of the silyl moiety (by negative hyperconjugation effects) and the remaining negative charge at the carbenic carbon atom, isolation of a three-coordinate, T-shaped palladium carbene complex is possible. In contrast, insufficient charge stabilization results in the transfer of the sulfur of the thiophosphoryl moiety and thus in the formation of a thioketone complex. While the thioketones are stable compounds the carbene complexes are revealed to be highly reactive and decompose under elimination of Pd metal. Computational studies revealed that both complexes are formed by a substitution mechanism. While the ketone turned out to be the thermodynamically favored product, the carbene is kinetically favored and thus preferentially formed at low reaction temperatures.

Synthesis and Electronic Structure of Carbene Complexes Based on a Sulfonyl-Substituted Dilithio Methandiide

“…This complex was found to be also accessible via an alternative route using a carbenoid analogue of 1, [Ph 2 PS(SO 2 Ph)C(Cl)-Li], and the Pd(0) precursor [Pd(PPh 3 ) 4 ]. 18,19 However, 3 is not stable at room temperature in solution and decomposed in the course of the workup procedure to form protonated species as well as a thioketone complex by sulfur transfer from the phosphorus to the carbenic carbon atom. This instability of complex 3 can probably be referred to the weak coordination ability of the sulfonyl moiety.…”

“…The solvent was evaporated in vacuo, and the orange residue was washed three times with n-pentane and cold diethyl ether, leaving an orange solid (57.7 mg, 0.08 mmol, 52%). For spectroscopic data see ref 18.…”

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

“…This mechanistic pathway was consistent with deuterium labeling studies. complex, accompanied by the η 2 -thioketone complex 1160 [1136]. The reaction pathways were studied by DFT and the carbene complex was determined to be the kinetic product while the thioketone complex was the thermodynamic product.…”

ADUC‐Preise: Tanja Gaich, Viktoria H. Däschlein‐Geßner und Michael Sommer / Carl‐Duisberg‐Gedächtnispreis: K. Ray / Horst‐Pracejus‐Preis: F. D. Toste / Leibniz‐Preis: H. Dietz, S. Grimme und C. Hertweck / Präsidentin der Königlich‐Schwedischen Akademie der Wissenschaften: C. Moberg / Yoshida‐Preis: K. Ding

“…In jüngster Zeit hat sie sich dem Einsatz von Carbenoiden und Carbenkomplexen zur Bindungsaktivierung und für Katalysen gewidmet. In Chemistry—A European Journal hat sie über die Bildung von Palladiumcarben‐ und ‐thioketonkomplexen2a und über Methandiid als nicht unschuldigen Liganden in Carbenkomplexen berichtet 2b …”