Pyridine-derived N-heterocyclic carbenes: an experimental and theoretical evaluation of the bonding in and reactivity of selected normal and abnormal complexes of nickel(II) and palladium(II)

Stander-Grobler, Elzet; Schuster, Oliver; Heydenrych, Greta; Cronje, Stephanie; Tosh, Evangeline; Albrecht, Martin; Frenking, Gernot; Raubenheimer, Helgard G.

doi:10.1021/om100431u

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Pyridine-derived N-heterocyclic carbenes: an experimental and theoretical evaluation of the bonding in and reactivity of selected normal and abnormal complexes of nickel(II) and palladium(II)

Stander-Grobler, Elzet Department of Chemistry and Polymer Science, University of Stellenbosch, South Africa
Schuster, Oliver Department of Chemistry and Polymer Science, University of Stellenbosch, South Africa - Department of Chemistry, University of Fribourg, Switzerland
Heydenrych, Greta Fachbereich Chemie, Philipps-Universitt Marburg, Germany
Cronje, Stephanie Department of Chemistry and Polymer Science, University of Stellenbosch, South Africa
Tosh, Evangeline Inorganic Chemistry Department, Technische Universität München, Garching, Germany
Albrecht, Martin Department of Chemistry, University of Fribourg, Switzerland
Frenking, Gernot Fachbereich Chemie, Philipps-Universitt Marburg, Germany
Raubenheimer, Helgard G. Department of Chemistry and Polymer Science, University of Stellenbosch, South Africa

22.10.2010

Published in:

Organometallics. - 2011, vol. 29, no. 22, p. 5821–5833

English We report a thorough investigation of a series of isomeric complexes with the general formula trans-(pyridylidene)M(PPh₃)₂Cl (M = Pd, Ni). For the first time, a systematic comparison of normal, abnormal, and remote bonding modes is presented. X-ray structural and ¹³C NMR data indicate the importance of carbenoid mesomeric contributions in their compound class. The catalytic performance of the palladium complexes trans-(pyridylidene)Pd(PPh₃)₂Cl as precursors in Suzuki−Miyaura-type cross-coupling suggests a correlation of remote bonding with catalyst robustness and effectivity. When metal precursors M(PPh₃)₄ are reacted with 2,4-dichloropyridinium salts, preferential formation of remote carbene complexes occurs and indications are that electronic parameters rather than steric influences are responsible for the observed selectivity. Calculations at the BP86/TZ2P level of theory support interpretation of the results.

Faculty

Faculté des sciences et de médecine

Department

Département de Chimie

Language