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Formation of Ruthenium−Aminocarbene Complexes from Aldimines and Aminals
Author(s) -
StandfestHauser Christina M.,
Mereiter Kurt,
Schmid Roland,
Kirchner Karl
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200200695
Subject(s) - chemistry , aldimine , carbene , imine , protonation , deprotonation , pyridine , ruthenium , medicinal chemistry , stereochemistry , catalysis , organic chemistry , ion
Specific pyridine‐based aldimines and aminals act as chelating ligands towards the RuCpL and RuTpL (Tp = hydrido trispyrazolylborate) fragments giving κ 2 N , N′ ‐coordinated cyclic imine complexes. Under particular conditions, as elucidated in this paper, these complexes rearrange into cyclic aminocarbene complexes. Thus, the reaction of [RuCp(L)(CH 3 CN) 2 ]PF 6 (L = CH 3 CN, PMe 3 , SbPh 3 ) with 1 equiv. of py−N=CHR [R = Ph (phenyl), Fc (ferrocenyl), Np (naphthyl)] affords the cyclic aminocarbene complexes [RuCp(L)(=C(R)NH−py)]PF 6 , whereas when L = PPh 3 , P i Pr 3 , and CO the reaction stops at the stage of the imine complex [RuCp(L)(κ 2 N , N′ ‐py−N=CHR)]PF 6 . Analogously, [RuTp(COD)Cl] (COD = 1,5‐cyclooctadiene) also reacts readily with the imines py−N=CHR (R = Ph, p MeOC 6 H 4 , Np) at elevated temperatures to yield the aminocarbene complexes [RuTp{=C(R)NH−py}Cl]. This process may open a new synthetic route for obtaining carbene complexes. The mechanism of the imine−aminocarbene conversion was analyzed by DFT/B3LYP calculations. Accordingly, the operation of a direct 1,2 hydrogen shift can be ruled out; the reaction seems to involve hydrido iminoacyl intermediates resulting from C−H bond activation and deprotonation/protonation steps. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)