Pincer ligands with an all-phosphorus donor set: subtle differences between rhodium and palladium

Abstract

The synthesis of a new, all-phosphorus pincer PP(NEt2)P ligand L3(NEt2), which is derived from 2-indolylphosphine and features a central N(2)P(NEt(2)) core, is described. This 'PPP' species shows coordination toward Rh as a neutral trisphosphine ligand. Tridentate diphenylphosphine-derived PP(H)P ligands L1(H) and L2(H), featuring a secondary phosphine core, show 'ambivalent' coordination, acting as persistent neutral triphosphine ligands with Rh, and as easily-formed monoanionic phosphido(bisphosphine) pincer ligands toward Pd. These subtle differences, which might be more general for group 9 and 10 metal complexes with this ligand set, are explained by comparative DFT calculations (BP86; def2-TZVP level of theory) for the Rh and Pd species involved, including those with the structurally related PN(H)P ligands. The optimized structure for complex PdCl(L2) indicates minimal overlap of available Pd d-orbitals with the lone pair of the central, deprotonated phosphorus atom (formally a phosphido fragment), suggesting that it behaves predominantly like a bulky phosphine instead of a phosphido fragment.

Reactivity of Iridium Complexes of a Triphosphorus-Pincer Ligand Based on a Secondary Phosphine. Catalytic Alkane Dehydrogenation and the Origin of Extremely High Activity

“…[41][42][43][44][45][46][47][48][49][50][51] Scheme 1. Pincer ligands of the type used in this work R PCP R P H PP R = i Pr [45][46][47][48] , Ph [48][49][50][51] , t Bu (this work)…”

“…34,52 To this end, we have synthesized bis(2-di-t-butyl-phosphinophenyl)phosphine ( tBu P H PP; Scheme 1), the bulky analogue of previously reported triphosphorus proligands iPr P H PP and Ph P H PP. 45,[49][50][51] Iridium complexes of tBu P H PP and the corresponding phosphido ( tBu PPP) derivatives were synthesized and their stoichiometric and catalytic chemistry investigated.…”

Cooperative Catalysis with First‐Row Late Transition Metals

“…Peters has developed dinuclear copper species based on the same PNP ligand scaffold as well as its close structural PPP derivative [PPP = bis(2-diisopropylphosphanyl)phenylphosphane], [80] which showed very interesting electronic behaviour, allowing the isolation of mixed-valent states as well as spectacular, long-lived luminescence. [71,72] Using the same PNP framework (Scheme 15), Mindiola disclosed the synthesis and follow-up reduction of the mononuclear CoCl(PNP) complex, which revealed some interesting chemistry, most notably the fact that the one-electron reduced Co I species Co(PNP) rapidly dimerized, with the PNP ligand acting as a bridging dinucleating scaffold in the resulting diamanoid structure. [73] Under an atmosphere of CO, the related mononuclear species was again obtained.…”

The Mechanism of Alkane Selective Oxidation by the M1 Phase of Mo–V–Nb–Te Mixed Metal Oxides: Suggestions for Improved Catalysts

“…A metal-carbon bond is formed in the reaction by binding directly with thewhich the metal binds direction to the P=O. Several such an organometallic structures have been synthesized recently, [42][43][44][45][46][47][48][49] but we find that none leads to a particularly strong bond of H to the P=O. For such a motif, after hydrogen binds with O=P, P-M σ-bond becomes a donor-acceptor bond and metal is reduced by one electron (Scheme 4).…”