Synthesis and Structural Characterization of Group 10 Metal Complexes Bearing an Amidodiphosphine Pincer Ligand

Abstract

Deprotonation of 3,6-di-tert-butyl-1,8-bis((diisopropylphosphanyl)-methyl)-9H-carbazole [(Cbzdiphos iPr )H] (1) with LiHMDS and reaction with (cod)PtCl 2 yielded the corresponding platinum chloride complex (Cbzdiphos iPr )PtCl (2), which was converted quantitatively into the bromide 3 and iodide 4 analogues by treatment 1011 with TMS-Hal (Hal = Br, I). Moreover, it was possible to prepare a Pt IV species by oxidative addition of CsBr 3 to compound 3. Furthermore, the hydride complexes of all group 10 metals were obtained by treatment of compound 1 with the M(0) precursors Ni(cod) ARTICLE Results and DiscussionReaction of (cod)PtCl 2 with the previously reported lithiated protioligand (Cbzdiphos iPr )Li yielded the corresponding platinum chlorido complex (Cbzdiphos iPr )PtCl (2). The corresponding bromido (3) and iodido (4) complexes were obtained in quantitative yield by reaction of compound 2 with an excess of TMS-Hal (Hal = Br, I; Scheme 1). These halogenido compounds were suitable starting materials for the preparation of the hydrido complex 8 (vide infra) by hydride substitution with NaBH(OMe) 3 . However, as is detailed below, the route via oxidative addition of the protioligand to a Pt 0 precursor gave rise to improved yields. Scheme 1. Overview of the syntheses of platinum halogenido complexes 2-5.

LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

“…The complexes have isomorphic structures in which the BIMCA ligand is meridionally coordinated to the metal center, the square planar coordination of which is completed by the hydrido ligand trans to the carbazolide-nitrogen. The origin of the hydrido ligand in 95 – 97 was not clear, but several options were considered as the proton source, including the BIMCA ligand itself, in contrast to the analogous group 10 metal (Ni, Pt, Pd) hydrido complexes formed unambiguously from the N–H oxidative addition of the PNP-carbazole precursor 312 ( vide infra , section ) to M 0 precursors (M = Ni, Pt, Pd) . The formation of the hydrido complexes was explained by the partial deprotonation of the bis­(imidazolium) salt 92 , leading to a monodeprotonated lithiated species 94 (Scheme ).…”

“…The origin of the hydrido ligand in 95−97 was not clear, but several options were considered as the proton source, including the BIMCA ligand itself, 185 in contrast to the analogous group 10 metal (Ni, Pt, Pd) hydrido complexes formed unambiguously from the N−H oxidative addition of the PNP-carbazole precursor 312 (vide infra, section 4.1) to M 0 precursors (M = Ni, Pt, Pd). 191 The formation of the hydrido complexes was explained by the partial deprotonation of the bis(imidazolium) salt 92, leading to a monodeprotonated lithiated species 94 (Scheme 14). 185 As this intermediate reacts further with the M 0 precursor, an anionic M 0 complex is formed, where the BIMCA ligand is κ 2 -coordinated to the metal via the C atom of the NHC moiety and the N atom of anionic carbazole, resulting in a very basic metal complex.…”