Search

A series of bidentate ligands associating an iminophosphorane and a phenoxide were synthesized and coordinated to nickel(II), leading initially to bimetallic KNi adducts. Replacement of the potassium by another metal allowed the isolation and characterization of bimetallic LiNi and AlNi complexes, while addition of one equivalent of triphenylphosphine gave access to monometallic complexes. The same type of complex was obtained with the coordination of a tridentate ligand incorporating a supplementary amine donor. These paramagnetic complexes were characterized by elemental analysis, and some of them by X-ray diffraction, evidencing a tetrahedral nickel center. They were shown to efficiently catalyze the oligomerization of ethylene in the presence of Et2AlCl (Al/Ni = 22.5) with TOF up to 72 000 mol(C2H4)/mol(Ni)/h, giving selectively butene (more than 97%) with at best 93% of 1-C4.

We report the synthesis of a unique class of luminescent heterotrinuclear complexes of the general formulas [Pt(terpy)\Cp*Ir-p-(?4-C6H4Se2)\Pt(terpy)][X]4 (X = OTf, 3a; PF6, 3b; BF4, 3c; ClO4, 3d; BPh4, 3e). In these coordination assemblies two Pt(terpy) moieties are held by a stable ?4-diseleno-p-benzoquinone complex [Cp*Ir-p-(?4-C6H4Se2)]. The molecular structures of solvates of 3a and 3b were ascertained by single-crystal X-ray diffraction study and confirmed the formation of the target molecules. The solid-state packing of two of these complexes confirms the presence of π?π and Pt···Pt interactions among individual units providing a 1D supramolecular chain for 3a, while a dimer species is obtained for 3b, illustrating the effect of the counterion on directing the crystal packing of the individual molecules. All compounds show phosphorescence in the red region (685?705 nm) in fluid solution and in the solid state at room temperature, unlike the analogous compound Pt(terpy)\Cp*Ir-p-(?4-C6H4S2)\Pt(terpy)][CF3SO3]4 obtained with a dithiobenzoquinone organometallic linker, which is only luminescent at low temperature.

International audience; A series of highly active yttrium phosphasalen initiators for the heteroselective ring-opening polymerization of rac-lactide are reported. The initiators are yttrium alkoxide complexes ligated by iminophosphorane analogues of the popular "salen" ligand, termed "phosphasalens". A series of novel phosphasalens have been synthesized, with varying substituents on the phenoxide rings and ethylene, propylene, rac-cyclohexylene, R,R-cyclohexylene, phenylene, and 2,2-dimethylpropylene groups linking the iminophosphorane moieties. Changing the substituents on the phosphasalen ligands results in changes to the rates of polymerization (kobs) and to the PLA heterotacticity (Ps = 0.87). Generally, the initiators have high rates, excellent polymerization control, and a tolerance to low loadings.

The LiCH2PPh2═NPh derivative 2 was cleanly prepared from the aminophosphonium salt [PhNH−PPh3+][Br−] (1) and MeLi. After formation of the iminophosphorane PPh3═NPh, nucleophilic displacement of one...

Bis(iminophosphoranyl)methanide ({CH(PPh2NR)}−, R = iPr or Ph) neodymium(III) complexes were prepared from NdI3(THF)3.5. The steric bulk of the ligand controlled the stoichiometry of the resulting complexes. Thus, three new complexes, bearing one or two ancillary ligands, were prepared and characterized using various spectroscopic techniques and by single-crystal X-ray diffraction. Reaction of the heteroleptic neodymium iodide complexes with amido groups yielded viable initiators for the ring-opening polymerization of lactide. The polymerizations were conducted using either the heteroleptic neodymium amido complexes or the in situ generated alkoxide complexes. Using such conditions, the neodymium complexes showed very fast and well-controlled polymerizations, with complete conversion being obtained in only a few minutes and yielding polylactide with controlled molecular weight and narrow polydispersity index. An initiating system comprising a rare neodymium-alkyl-carbene complex [Nd{C(PPh2NiPr)2}{CH(PPh2N...

The novel tetradentate ligand 1, associating two phosphines and two iminophosphorane moieties, was easily synthesized from commercially available bis(diphenylphosphino)methane and ethylenediamine via the preparation of the bis(phosphine−aminophosphonium) adduct 1-(HBr)2. Deprotonation of this salt afforded the corresponding tetradentate P2N2 phosphine−iminophosphorane ligand 1. Coordination to Ni(II) and Pd(II) metal centers afforded complexes 2 and 3, respectively, characterized by multinuclear NMR and X-ray analysis. Both cationic complexes adopt a square-planar geometry around the metal, all phosphorus and nitrogen atoms being coordinated. In contrast to most iminophosphorane complexes, 2 and 3 could be handled in water without any apparent decomposition. Their catalytic activity was evaluated in Suzuki−Miyaura coupling. These reactions were conducted in toluene, water, or a biphasic toluene/water medium in the presence of a phase-transfer agent. Under these last conditions, the Pd catalyst 3 (0.1 mol ...

Reaction of 1-bromo-2,5-diphenylphosphole with 10,11-dihydro-5H-dibenzo[b,f]azepine resulted in the formation of the corresponding aminophosphole 3, which was structurally characterized. Reaction of 3 with [Rh2(μ-Cl)2(C2H4)4] and [Rh(COD)2][BF4] afforded the complexes [Rh2(μ-Cl)2(3)2] (4) and [Rh(COD)(3)][BF4] (5), respectively. In both complexes, characterized by NMR as well as by X-ray crystallography, ligand 3 behaves as a chelate through coordination of the phosphorus atom and the olefinic part of the ligand to the rhodium center. The activity of both complexes was tested in the hydroformylation of mono- and disubstituted olefins at 20 bar of CO/H2 pressure. Complex 5 proves to be the most efficient catalyst.