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Synthesis and Bonding in Carbene Complexes of an Unsymmetrical Dilithio Methandiide: A Combined Experimental and Theoretical Study
Author(s) -
Gessner Viktoria H.,
Meier Florian,
Uhrich Diana,
Kaupp Martin
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201303115
Subject(s) - carbene , geminal , transition metal carbene complex , nucleophile , zirconium , chemistry , ionic bonding , polymer chemistry , combinatorial chemistry , photochemistry , computational chemistry , organic chemistry , catalysis , ion
Herein, we report the preparation of a new unsymmetrical, bis(thiophosphinoyl)‐substituted dilithio methandiide and its application for the synthesis of zirconium‐ and palladium‐carbene complexes. These complexes were found to exhibit remarkably shielded 13 C NMR shifts, which are much more highfield‐shifted than those of “normal” carbene complexes. DFT calculations were performed to determine the origin of these observations and to distinguish the electronic structure of these and related carbene complexes compared with the classical Fischer and Schrock‐type complexes. Various methods show that these systems are best described as highly polarized Schrock‐type complexes, in which the metal–carbon bond possesses more electrostatic contributions than in the prototype Schrock systems, or even as “masked” methandiides. As such, geminal dianions represent a kind of “extreme” Schrock‐type ligands favoring the ionic resonance structure M + CR 2 − as often used in textbooks to explain the nucleophilic nature of Schrock complexes.