Stabilization of the Triphosphallyl Ligand η³‐P₃{P(O)H} at Iridium via Alkaline Activation of P₄

Abstract

The selective functionalization of the polyphosphorus moiety Ph2PCH2PPh2PPPP present as a tetrahapto-ligand in complex [Ir(dppm)(Ph2PCH2PPh2PPPP)](+) (1, dppm=Ph2PCH2PPh2) was obtained by reaction of 1 with water under basic conditions at room temperature. The formation of the new triphosphaallyl moiety η(3)-P3{P(O)H} was determined in solution by NMR spectroscopy, and confirmed in the solid state by a single-crystal X-ray structure of the stable product [Ir(κ(2)-dppm)(κ(1)-dppm)(η(3)-P3{P(O)H})] (2). In solution, 2 has a fluxional behavior attributable to the four P atoms belonging to the tetraphosphorus moiety in 1 and exhibits a chemical exchange process involving the two PPh2 moieties of the same bidentate ligand, as determined by 1D and 2D NMR spectroscopy experiments carried out at variable temperature. The mechanism of the reaction was investigated at the DFT level, which suggested a selective attack of an in-situ generated OH(-) anion on one of the non-coordinated phosphorus atoms of the P4 moiety. The reaction then evolves through an acid-assisted tautomerization, which leads to the final compound 2. Bonding analysis pointed out that the new unsubstituted P3-unit in the η(3)-P3{P(O)H} moiety behaves as a triphosphallyl ligand.

Activation of White Phosphorus by Low-Valent Group 5 Complexes: Formation and Reactivity of cyclo-P4 Inverted Sandwich Compounds

“…Gratifyingly, the solid-state 31 P MAS NMR spectrum recorded at 293 K for 1 displayed two sets of signals (δ iso = +251(2) and +84(2) ppm with large chemical shift anisotropy; see Supporting Information (SI)), corresponding to the two non-equivalent P atoms in the cyclo -P 4 ligand, in agreement with the asymmetric μ-η 3 :η 3 coordination mode observed by X-ray crystallography (see below). In contrast, the previously reported {[(ODipp) 3 Nb] 2 ­(μ‑η 3 :η 3 P 4 )} complex featured a sharp singlet resonance at +124 ppm in its solution 31 P­{ 1 H} NMR spectrum . Analysis of the solid-state 31 P MAS NMR spectrum for 2 was more difficult because of substantial line-broadening, and we were only able to identify one type of signal at δ iso = +208(8) ppm (see SI).…”

“…In contrast, the previously reported {[(ODipp) 3 Nb] 2 (μ-η 3 :η 3 P 4 )} complex featured a sharp singlet resonance at +124 ppm in its solution 31 P{ 1 H} NMR spectrum. 26 Analysis of the solid-state 31 P MAS NMR spectrum for 2 was more difficult because of substantial line-broadening, and we were only able to identify one type of signal at δ iso = +208(8) ppm (see SI ).…”

“…A classic methodology for activating white phosphorus involves using well-identified or in situ generated reduced metal complexes. − Depending on the reducing ability, nature, and coordination environment, a wide array of metal–phosphide species can be generated. ,,− Despite several recent achievements in the subsequent transformation of these activated metal–phosphorus species, ,− direct incorporation of P atoms from P 4 under mild conditions both stoichiometrically and catalytically remains a great challenge for contemporary main group and transition metal organometallic chemists. This notably requires a deeper understanding of the nature of the metal–phosphide interaction and the reaction processes involved.…”

Transformations of the cyclo-P4 ligand in [Cp′′′Co(η4-P4)]

“…A similar reaction was reported by Peruzzini and co-workers for the reaction of [Ir(dppm)(Ph 2 PCH 2 PPh 2 PPPP)] + with water under basic conditions. 37…”

Metal‐Assisted Opening of Intact P4 Tetrahedra

“…Remarkably, there are very few examples in literature of a “naked” tetraphosphorus moiety η 3 ‐coordinated to a metal center, such as the bimetallic complex [LNi(η 3 ‐P 4 )NiL] (L: L Et =CH[CMeN(2,6‐Et 2 C 6 H 3 )] 2 , L i Pr =CH[CMeN(2,6‐ i Pr 2 C 6 H 3 )] 2 ) featuring a doubly trihapto‐coordinated P 4 . The optimized structure of the intermediate shows an asymmetric coordination of the new tetraphosphorus moiety to the cobalt center with two shorter (2.20 Å) and one longer 2.27 Å Co−P distance(s), reminiscent of the iridium complex [Ir(κ 2 ‐dppm)(κ 1 ‐dppm)(η 3 ‐P 3 {P(O)H})] (dppm=(Ph 2 P) 2 CH 2 ) and the Mo complex [Cp′Mo(CO) 2 {(η 3 ‐P 4 ){Cr(CO) 5 } 4 (H)}] (Cp′=η 5 ‐C 5 H 4 t Bu), in which a naked P 3 unit (coming from P 4 as well) behaves as a stable triphosphaallyl group and possesses an asymmetric structure.…”