Validating the Biphilic Hypothesis of Nontrigonal Phosphorus(III) Compounds

Abstract

Constraining s 3 -P compounds in nontrigonal, entatic geometries has proven to be an effective strategy for promoting biphilic oxidative addition reactions more typical of transition metals.A lthough qualitative descriptions of the impact of structure and symmetry on s 3 -P complexes have been proposed, electronic structure variations responsible for biphilic reactivity have yet to be elucidated experimentally. Reported here are PK-edge XANES data and complementary TDDFT calculations for aseries of structurally modified P(N) 3 complexes that both validate and quantify electronic structure variations proposed to give rise to biphilic reactions at phosphorus.T hese data are presented alongside experimentally referenced electronic structure calculations that reveal nontrigonal structures predicted to further enhance biphilic reactivity in s 3 -P ligands and catalysts.

Trimerization and cyclization of reactive P-functionalities confined within OCO pincers

“…13 Fortunately, by distorting phosphines away from their classic three-fold symmetry, their frontier orbitals can become energetically accessible. 14 For example, C s -symmetric phosphorus triamide A can promote oxidative addition of alcohols and amines. [15][16][17] Related C 2v -symmetric B, 18 describable by numerous resonance structures including B 0 and B 00 due to extensive conjugation within the ONO ligand 19 will oxidatively add H 2 from H 3 N-BH 3 and transfer that hydrogen equivalent to azobenzene in a catalytic fashion, producing hydrazines (Fig.…”

Metal–Ligand Role Reversal: Hydride-Transfer Catalysis by a Functional Phosphorus Ligand with a Spectator Metal

“…Although tricoordinate phosphorus (σ 3 -P) ligands are largely seen as archetypal spectator ligands within the foregoing continuum, the literature shows sporadic reference to reactions invoking their conversion to higher P-coordinate intermediates . In this vein, we have recently established that nontrigonal σ 3 -P compounds − exhibit enhanced electrophilicity at P that enables access to stable higher coordinate (σ 4 -P)–M complexes by “nonspectator” reactivity. − Based on these findings, we hypothesized that a new opportunity might be realized for useful catalysis based on a “functional” σ 3 -P ligand if paired with an inert, coordinatively and electronically saturated metal guest. We report here the realization of this vision using a nontrigonal σ 3 -P-containing chelate in combination with a spectator (Me 5 C 5 )­Ru + fragment to drive hydride transfer reductions of organic acceptors and chloroalkanes without chemical or redox reactions at Ru.…”