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.

Recent developments in the chemistry of non-trigonal pnictogen pincer compounds: from bonding to catalysis

“…TDDFT calculation reveal that this energy shi is directly linked to the energetic lowering of one of the s* P-N orbitals due to geometric distortion towards C s symmetry. 32 The effect of geometric perturbation on the total electronic energy, the LUMO energy and the HOMO/LUMO gap is shown by the calculated heat maps in Fig. 2 employing P(NH 2 ) 3 as a model compound.…”

“…The distortion towards C s -symmetry induces a liing of degeneracy in these antibonding orbitals while the lone-pair energy is not signicantly affected. Full perturbation towards a T-shaped geometry results in a considerably reduced HOMO/LUMO gap, reminiscent of the electronic conguration of transition metals, 32 and related main-group compounds such as cyclic alkyl amino carbenes, 33,34 which display biphilic reactivity.…”

Tricoordinate Nontrigonal Pnictogen‐Centered Radical Anions: Isolation, Characterization, and Reactivity

“…Consequently,t he reduction with astrong reducing agent led to the cleavage of the EÀCbond rather than the formation of the stable radical anion. [8] Recently,several R 3 Ecompounds with nontrigonal geometry were reported. [9] They have emerged as new candidates for small molecule activation and catalysis akin to transitionmetal complexes.…”

A Nontrigonal Tricoordinate Phosphorus Ligand Exhibiting Reversible “Nonspectator” L/X‐Switching

“…coordination to the presence of a low-energy P-based orbital made accessible by the nontrigonal local environment. 21 The presence of the low-lying P-centered orbital in A and related compounds raised the prospect of accentuated intermolecular electrophilic reactivity of such nontrigonal σ 3 -P ligands. We report here the reversible addition of an exogenous nucleophile to the P-center of an unsupported (σ 3 -P)-M complex C that demonstrates a nonspectator behavior of ligands A.…”

“…NOCV deformation density channels Δρ2 and Δρ3 correspond to the backflow of electron density from an Fe dπ orbital into P-based π-acceptor orbitals with two distinct interaction energies (ΔE 2 orb = -10.7 kcal/mol, ΔE 3 orb = -7.35 kcal/mol), consistent with the lifting of pπ degeneracy at nontrigonal 1a shown by previous XAS evidence. 21 By way of comparison, EDA-NOCV partitioning of the Fe-P bond in 1b•Fp + gives donation σ(P→Fe) = -65.8 kcal/mol (70.8% of Eorb) and back-donation π(P←Fe) = -13.2 kcal/mol (14.2% of Eorb). This analysis therefore quantifies the relatively weaker σ-donating ability of nontrigonal σ 3 -P compound 1a as compared to a compositionally related phosphorous triamide 1b evident from spectroscopy (vide supra).…”