Air-Stable Platinum and Palladium Complexes Featuring Bis[2,4-bis(trifluoromethyl)phenyl]phosphinous Acid Ligands

Coordination chemistry and catalysis with secondary phosphine oxides

Review on synthesis, coordination chemistry and catalysis with secondary phosphine oxides.

Palladium-catalyzed microwave-assisted Hirao reaction utilizing the excess of the diarylphosphine oxide reagent as the P-ligand; a study on the activity and formation of the “PdP2” catalyst

The microwave-assisted Hirao reaction of bromobenzene and diarylphosphine oxides was performed at 120 °C using triethylamine as the base, and 5% of palladium acetate as the catalyst in ethanol. 5% Excess of the >P(O)H reagent served as the reducing agent, while another 10% as the preligand (in the >POH tautomeric form). It was found that the P–C coupling reaction was significantly faster with (2-MeC6H4)2P(O)H (A) and (3,5-diMeC6H3)2P(O)H (B), than with Ph2P(O)H (C) and (4-MeC6H4)2P(O)H (D). Moreover, species A and B could be applied as selective P-ligands in the reaction of bromobenzene with C or D. Dependence of the effectiveness of “PdP2” catalysts with diarylphosphine oxide preligands on the methyl substituents followed a reversed order as the reactivity of the diarylphosphine oxide species in the P–C coupling itself. Formation of the “PdP2” catalyst from palladium acetate and diarylphosphine oxide has never been studied, but now it was evaluated by us at the B3LYP level of theory applying 6-31G(d,p) for C,H,P,O and SDD/MW28 for Pd including the explicit-implicit solvent model. The novel mechanism requiring three equivalents of the >P(O)H species for each of the palladium acetate molecule was in agreement with the preparative experiments. The ligation of palladium(0) with different P(III) species comprising the >POH form of the >P(O)H reagent was also studied, and the critical role of the steric hindrance on the ligation, and hence on the activity of the “PdP2” catalyst was substantiated. Last but not least, the influence of the Me substituents in the aromatic ring of the P-reagents on the energetics of the elemental steps of the Hirao reaction itself was also evaluated.

Synthesis of chiral supramolecular bisphosphinite palladacycles through hydrogen transfer-promoted self-assembly process

P-Chiral secondary phosphine oxides react with Pd2(dba)3 in an acidic medium to provide chiral supramolecular bisphosphinite palladacycles through a H-transfer-based self-assembly process prior to SPO-promoted oxidative addition of an acid to a Pd(0) centre. The one-pot methodology allows variations of the X-type ligand as desired. Eight complexes have been characterised by X-ray diffraction.

Phosphinito palladium(ii) complexes as catalysts for the synthesis of 1,3-enynes, aromatic alkynes and ynones

An air-stable phosphinito palladium(ii) complex has been found to be an efficient catalyst in the formation of C–C bonds.

Crystal structure of bis(μ 2-chlorido)-bis(di-p-tolylhydroxyphosphine-κP)-bis(di-p-tolylphosphite-κP)dipalladium(II), C56H58Cl2O4P4Pd2

C56H58Cl2O4P4Pd2, monoclinic, P21/c (no. 14), a = 12.736(2) Å, b = 18.187(2) Å, c = 12.335(2) Å, β = 109.053(4)°, V = 2700.63 Å3, Z = 2, R gt(F) = 0.034, wR ref(F 2) = 0.0955, T = 100 K.

Transition Metal Complexes of Phosphinous Acids Featuring a Quasichelating Unit: Synthesis, Characterization, and Hetero-bimetallic Complexes

Diorganophosphane oxides were employed as preligands for the synthesis of catalytically active transition metal complexes of the phosphinous acids (CF3)2POH and (C2F5)2POH. Their reactions with solid PtCl2 and PdCl2 led to the formation of mononuclear phosphinous acid complexes [Cl2M{P(R(f))2OH}2] (M = Pd, Pt; R(f) = C2F5, CF3), which can be crystallized, for example, as its pyridinium salts, 2[HPy](+)[Cl2Pd{P(CF3)2O}2](2-). In vacuo HCl is liberated from the neutral palladium complexes affording mixtures of di- and polynuclear complexes. Moreover, (C2F5)2POH was reacted with several β-diketonato complexes of palladium, platinum, and nickel yielding air- and moisture-stable complexes [(acac)M{[P(R(f))2O]2H}], featuring a quasichelating phosphinous acid phosphinito unit {P(R(f))2O···H···O(R(f))2P}(-). Treatment of [Ni(Cp)2] (Cp = cyclopentadienyl) and [(cod)RhCl]2 (cod = 1,5-cyclooctadiene) with (C2F5)2POH leads to the substitution of one Cp or chloro ligand by a quasichelating unit. The novel coordination compounds were characterized by NMR and IR spectroscopies, mass spectrometry, and X-ray diffraction analysis. The platinum complex [(acac)Pt{[P(C2F5)2O]2H}] (acac = acetylacetonato) was used for the construction of hetero-bimetallic complexes by the treatment with [(cod)RhCl]2 and [Ni(Cp)2]. The trinuclear bimetallic complex [{(acac)Pt[P(C2F5)2O]2}2Ni] is the first structurally characterized hetero-bimetallic species containing a bis(perfluoroalkyl)phosphinito bridge.