![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)
Phosphine-NHC-Phosphonium Ylide Pincer Ligand: Complexation with Pd(II) and Unconventional P-Coordination of the
Mohammad Ameskal1, Rachid Taakili1, Ekaterina S Gulyaeva1,2
1LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne, 31077 Toulouse cedex 4, France.
Abstract:
An efficient synthesis of two pincer preligands [Ph2PCH(R)ImCH2CH2CH2PPh3]X2 (R = H, X = OTf; R = Ph, X = BF4) was developed. Subsequent reactions with PdCl2 and an excess of Cs2CO3 led to the formation of highly stable cationic ortho-metalated Pd(II) complexes [(P,C,C,C)Pd]X exhibiting phosphine, NHC, phosphonium ylide, and σ-aryl donor extremities. The protonation of one of the latter complexes with R = H affords the Pd(II) complex [(P,C,C)Pd(MeCN)](OTf)2 bearing an unprecedented nonsymmetrical NHC core pincer scaffold with a 5,6-chelating framework. The overall donor properties of this phosphine-NHC-phosphonium ylide ligand were estimated using the experimental νCN stretching frequency in the corresponding [(P,C,C)Pd(CNtBu](OTf)2 derivative and were shown to be competitive with the related bis(NHC)-phosphonium ylide and phenoxy-NHC-phosphonium ylide pincers. The presence of a phenyl substituent in the bridge between phosphine and NHC moieties in the ortho-metalated complex [(P,C,C,C)Pd](BF4) makes possible the deprotonation of this position using LDA to provide a persistent zwitterionic complex [(P,C,C,C)Pd] featuring a rare P-coordinated phosphonium ylide moiety in addition to a conventional C-coordinated one. The comparison of the 31P and 13C NMR data for these C- and P-bound phosphonium ylide fragments within the same molecule was performed for the first time, and the bonding situation in both cases was studied in detail by QTAIM and ELF topological analyses.
Related Concept Videos
02:42Valence Bond Theory
02:51Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
02:34Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
02:54Coordination Compounds and Nomenclature
01:19Aldehydes and Ketones to Alkenes: Wittig Reaction Overview
03:35Hybridization of Atomic Orbitals II