Group 10 Metal Complexes Supported by Pincer Ligands with an Olefinic Backbone

The coordination chemistry of 2,2′-bis­(di-iso-propyl­phosphino)-trans-stilbene (tPCHCHP) with group 10 metal centers in a variety of oxidation states is reported; different coordination modes were observed depending on the oxidation state of the metal. With metal centers in the 0 or +1 oxidation state ((tPCHCHP)­Ni, [(tPCHCHP)­Pd]2, (tPCHCHP)­NiCl, (tPCHCHP)­NiI), η2 coordination of the olefin occurs, whereas, with metals in the +2 oxidation state, C–H activation of the backbone, followed by rapid H–X reductive elimination, was observed, leading to an η1 coordination of the backbone in (tPCCHP)­MCl (M = Ni, Pd, Pt). Employing the methyl-substituted analogue, 2,2′-bis­(di-iso-propylphosphino)-trans-diphenyl-1,2-dimethylethene (tPCMeCMeP), forced an η2 coordination of the olefin in [(tPCMeCMeP)­NiCl]2­[NiCl4]. The synthesis of the hydride complex (tPCCHP)­NiH was attempted, but, instead, led to the formation of (tPCHCHP)­Ni, indicating that the vinyl form of the backbone can function as a hydrogen acceptor. All metal complexes were characterized by multinuclei NMR spectroscopy, X-ray crystallography, and elemental analysis.