Copper(I) Complexes of Pyridine-Bridged Phosphaalkene-Oxazoline Pincer Ligands

Abstract

The synthesis of enantiomerically pure pyridine-bridged phosphaalkene-oxazolines ArP═C(Ph)(2,6-C5H3NOx) (1, Ar = Mes/Mes*, Ox = CNOCH(i-Pr)CH2/CNOCH(CH2Ph)CH2) is reported. This new ligand forms a κ(P), κ(2)(NN) dimeric complex with copper(I) (7) that dissociates into a cationic κ(3)(PNN) monomeric complex upon addition of a neutral ligand {[1a·CuL]OTf (8a-e): L = PPh3 (a), P(OPh)3 (b), 2,6-lutidine (c), 4-DMAP (d), 1-methylimidazole (e)}. The P-Cu bond lengths in 8 are influenced by the π-accepting/σ-donating properties of L, and this can be observed by changes in the δ(31)PP═C NMR shift. The donor-acceptor properties in complexes of type 8 have also been investigated by UV/vis spectroscopy and density functional theory calculations.

Isolable Phosphaalkenes Bearing 2,4,6-Trimethoxyphenyl and 2,6-Bis(trifluoromethyl)phenyl as P-Substituents

“…Remarkably, the metrical parameters are overwhelmingly similar, perhaps implying that in triarylphosphaalkenes the P-substituent has little effect provided it is bulky enough to inhibit dimerization. The PC bond length of 1a [1.689(2) Å] is at the longer end of the range typical for C-substituted phosphaalkenes (1.61–1.71 Å) and does not differ considerably from those of P-Mes phosphaalkenes (1.68–1.71 Å) ,,,, or P–Ar* (Ar* = Mes* or 2,6-Mes 2 C 6 H 3 ) phosphaalkenes (1.68–1.70 Å). , The P–C TMOP bond for 1a [1.822(2) Å] is at the shorter end of the range typical for P-Mes phosphaalkenes (range: 1.82–1.84 Å) ,,,, and P–Ar* phosphaalkenes (range: 1.83–1.86 Å). , A slight elongation of the PC bond and shortening of the P–C TMOP bond has been observed for related phosphaalkenes) , and may reflect π-conjugation between the TMOP group and the PC bonds. On the other hand, the angle between the plane of the PC bond and the plane of the aromatic ring of the TMOP-group in 1a is 76.42(7)° and suggests minimal π-conjugation.…”

Triphenylphosphaalkenes in Chemical Equilibria

“…We recently reported a modified protocol for the phospha ‐Peterson reaction, to synthesize P ‐Mes‐phosphaalkenes. Prior to our work, the starting material MesP(Li)TMS was made in situ by treating MesP(TMS) 2 with one equivalent of MeLi in THF . The so‐formed MesP(Li)TMS was then reacted in THF with ketones to afford the corresponding P ‐Mes‐phosphaalkenes .…”

Thorium(IV) and Uranium(IV) Phosphaazaallenes

“…The reactivity of metal-phosphido complexes is of interest for the development of hydrophosphination catalysts as well as the synthesis of phosphorus-element multiple bonds. For example, phosphaalkenes, P=C, have attracted interest for building blocks in organophosphorus chemistry [1][2][3], ligands to transition metal complexes [4,5], as well as potential applications as functional materials [6][7][8][9][10]. After nearly 20 years of dormancy [11][12][13][14][15], actinide-phosphorus has received greater attention recently [16][17][18][19] with researchers examining similarities and differences in the molecular and electronic structure of its more studied congener, nitrogen.…”