Synthesis, Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines

Abstract

The experimental and computational characterization of a series of dialkylterphenyl phosphines, PR2Ar′ is described. The new P‐donors comprise five compounds of general formula PR2ArDtbp2 (R=Me, Et, iPr, c‐C5H9 and c‐C6H11); ArDtbp2 = 2,6‐C6H3‐(3,5‐C6H3‐(CMe3)2)2), and another five PR2Ar′ phosphines containing the bulky alkyl groups iPr, c‐C5H9 or c‐C6H11, in combination with Ar′=ArXyl2 , ArXyl'2 , or ArPh2 (L1–L10). Steric and electronic parameters have been determined computationally and from IR and X‐ray data obtained for the phosphines and for some derivatives, including tricarbonyl and dicarbonyl nickel complexes, Ni(CO)3(PR2Ar′) and Ni(CO)2(PR2Ar′). In the solid state, the free phosphines PR2Ar′ adopt one of the three possible structures formally related by rotation around the Cipso−P bond. Details on their relative energies and on the influence of the free phosphine structure on its coordination chemistry towards Ni(CO)n (n = 2, 3) fragments has been obtained by experimental and computational methods.

Group 9 and 10 Metal Complexes of an Ylide-Substituted Phosphine: Coordination versus Cyclometalation and Oxidative Addition

“…The signal of the carbon atom of the carbonyl ligands resonates at 196.2 ppm, in the typical range of known terminal nickel carbonyls. 13 The CO stretching frequency of 2060.2 cm –1 determined by IR spectroscopy confirms the strong donor property of the YPhos ligand, as recently reported based on the [LRh(acac)Cl] complex. 7 The stronger donor property of 2 compared to 1 (TEP( 1 ) = 2066.5 cm –1 ) is probably also the reason for the selective formation of the tricarbonyl complex.…”

Dialkylterphenyl Phosphine‐Based Palladium Precatalysts for Efficient Aryl Amination of N‐Nucleophiles

“…As stated above, their 31 P{ 1 H} NMR spectra contain only one 31 P resonance, which is shifted by approximately 47 ppm to higher frequencies relative to the uncoordinated phosphines. Again, such a change in the 31 P chemical shift seems to indicate that terphenyl phosphines in these compounds could be coordinated in a bidentate fashion . In fact, the NMR features of the phosphine ligands in complexes 3 seem to support this hypothesis, because, in both instances, the two flanking xylyl rings of the terphenyl fragment and the two P−R groups appear inequivalent at room temperature.…”

“…The resonance due to the phosphorus nucleus in the cationic derivatives 2 experiences a shift to higher frequency (Δ δ ≈13 ppm) with respect to that of the neutral complexes 1 a and 1 b . Such a shift may be indicative of a bidentate coordination mode of the phosphine ligand involving the P atom and one of the flanking aryl ring of terphenyl moiety . The complexity of the 1 H and 13 C{ 1 H} NMR spectra of 2 a and 2 b at 25 °C attests for the low symmetry exhibited by these compounds.…”

“…Solvents were rigorously dried and degassed before use. Ligands L1 – L5 and [Pd(2‐aminobiphenyl)X] 2 (X=Cl, OMs) were synthesized by following previously reported procedures. Reagents were purchased from commercial suppliers and used without further purification.…”

“…With the aim of investigating the properties of this type of ligands, we prepared a series of dialkylterphenyl phosphines with a variety of substituents both on the phosphorus atom and on the terphenyl moiety and evaluated their electronic and steric parameters . These studies highlighted their strong basicity and their superior steric protection when compared to dicyclohexylbiaryl phosphines . Moreover, the coordination properties of terphenyl phosphines towards a variety of late transition metals including Rh, Ir, Ni, Pt, and Au proved their ability to adopt different coordination modes involving the P atom and one of the flanking aryl rings of the terphenyl fragment .…”