Nickel and Palladium Complexes of New Pyridine-Phosphine Ligands and Their Use in Ethene Oligomerization

A cavity-shaped cis-chelating P,N ligand for highly selective nickel-catalysed ethylene dimerisation

The presence of a permethylated α-cyclodextrin (α-CD) cavity in a chelating P,N ligand promotes exclusive formation of 1 : 1 ligand/metal complexes. In MX₂ complexes, one of the two halido ligands is forced to reside inside the CD hollow while the second one is pointing outside. Unlike its cavity-free analogue, a Ni(II) complex of the CD ligand is a highly selective precatalyst for ethylene dimerisation (96% C₄ selectivity with up to 95% of 1-butene within the C₄ fraction).

Boron Lewis Acid-Catalyzed Hydrophosphinylation of N-Heteroaryl-Substituted Alkenes with Secondary Phosphine Oxides

We report the boron-catalyzed hydrophosphinylation of N-heteroaryl-substituted alkenes with secondary phosphine oxides that furnishes various phosphorus-containing N-heterocycles. This process proceeds under mild conditions and enables the introduction of a phosphorus atom into multisubstituted alkenylazaarenes. The available mechanistic data can be explained by a reaction pathway wherein the C-P bond is created by the reaction between the activated alkene (by coordination to a boron catalyst) and the phosphorus(III) nucleophile (in tautomeric equilibrium with phosphine oxide).

Ni-Based Complexes in Selective Ethylene Oligomerization Processes

Linear alpha-olefins are widely used in the petrochemical industry and the world demand for these compounds increases annually. At present, the main method for producing linear alpha-olefins is the homogeneous catalytic ethylene oligomerization. This review presents modern nickel catalysts for this process, mainly systems for obtaining of one of the most demanded oligomer—1-butene—which is used for the production of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE). The dependence of the catalytic performance on the composition and the structure of the used activated complexes, the electronic and coordination states of the nickel center was considered.

Palladacycles of sulfated and selenated Schiff bases of ferrocene-carboxaldehyde as catalysts for O-arylation and Suzuki–Miyaura coupling

Palladacycles of Schiff-bases having a ferrocene core catalyze O-arylation of ArBr and Suzuki–Miyaura coupling of ArBr/Cl with a yield up to 93%.

Ring-tension adjusted ethylene polymerization by aryliminocycloheptapyridyl nickel complexes

The 9-aryliminocycloheptapyridyl nickel chlorides, activated by Et₃Al₂Cl₃ or MAO, exhibited high activities toward ethylene polymerization and produced highly branched PE in narrow polydispersity.

Synthesis, structure, and optical properties of Pt(II) and Pd(II) complexes with oxazolyl- and pyridyl-functionalized DPPM-type ligands: a combined experimental and theoretical study

New square-planar complexes [Pt(1(-H))2] (2a) [1(-H) = (oxazolin-2-yl)bis(diphenylphosphino)methanide] and [Pd(1(-H))2] (2b), of general formula [M{(Ph2P)2C---C---NCH2CH2O}2] (M = Pt, 2a; M = Pd, 2b), result from deprotonation of 2-{bis(diphenylphosphino)methyl}oxazoline (1) at the PCHP site. The new, functionalized dppm-type ligand 4-{bis(diphenylphosphino)methyl}pyridine, (Ph2P)2CH(4-C5H4N) (4), was prepared by double lithiation and phosphorylation of 4-picoline. In the presence of NEt3, the reactions of 2 equiv of 4 with [PtCl2(NCPh)2] and [Pd(acac)2] (acac = acetylacetonate) afforded [Pt(4(-H))2] (5a) [4(-H) = bis(diphenylphosphino)(pyridin-4-yl)methanide] and [Pd(4(-H))2] (5b), of general formula [M{(Ph2P)2C(4-C5H4N)}2] (M = Pt, 5a; M = Pd, 5b), respectively. In the absence of base, the reactions of 2 equiv of 4 with [PtCl2(NCPh)2] and [PdCl2(NCPh)2] afforded (5a·2HCl) (6a) and (5b·2HCl) (6b), respectively, in which the PCHP proton of 4 has migrated from carbon to nitrogen to give a pyridinium derivative of general formula [M{(Ph2P)2C(4-C5H4NH)}2]Cl2 (M = Pt, 6a; M = Pd, 6b). The complexes 3a, 5a·2MeOH, and 6b·4CH2Cl2 have been structurally characterized by X-ray diffraction. The absorption/emission properties of the Pt(II) complexes 2a and 5a and the Pd(II) complexes 2b and 5b have been investigated by UV-vis spectroscopy and theoretical analysis based on density functional theory. The UV-vis absorption spectra of the neutral complexes recorded in dilute N,N'-dimethylformamide solutions are dominated by intense spin-allowed intraligand transitions in the region below 350 nm. The complexes exhibit charge-transfer bands between 350 and 500 nm. The experimental and theoretical absorption spectra agree qualitatively and point to two low-lying ligand-to-metal charge transfer states that contribute to the bands observed between 350 and 500 nm. The complexes are emissive in frozen solutions at 77 K, in the pure solid state, and when doped into films of poly(methyl methacrylate) but are nonemissive in solution. A red shift is observed when Pt(II) is replaced by Pd(II).

The synthesis and application of novel Ni(ii) N-alkyl dipyridylaldiminato complexes as selective ethylene oligomerisation catalysts

A series of dinuclear Cl-bridged Ni(ii) complexes, 1a–1e, ligated by N-alkyl 2,2′-dipyridylamine ligands displayed high activity in ethylene oligomerisation, when activated with alkyl aluminium reagents. Steric and electronic effects as well as activation pathways were found to have a significant impact on catalyst activity and selectivity.

New bis(aryloxy)-Ti(IV) complexes and their use for the selective dimerization of ethylene to 1-butene

New titanium complexes of general formula [(ArO)(n)Ti(Oi-Pr)((4-n))] were synthesized and used as pre-catalysts for the selective dimerization of ethylene to 1-butene. The complexes were prepared in cyclohexane using [Ti(Oi-Pr)(4)] and one or two equivalents of the corresponding phenols (ArOH) at room temperature. In this work, both monodentate and chelating phenols were evaluated. For alkyl-substituted phenols, it was demonstrated that large steric hindrance at both ortho and ortho' positions selectively yielded the mono-substituted complexes [(ArO)Ti(Oi-Pr)(3)]. Substitution at only one of the ortho positions allowed both the mono- and the di-substituted Ti complexes to be isolated. When a heteroatom was introduced on the phenol backbone, di-substitution systematically occurred except with phenols presenting a hemilabile -CH(2)NR(2) group at the ortho position. Upon activation with 3 equiv. of AlEt(3) at 20 bar and 60 °C, all the complexes selectively dimerized ethylene to 1-butene (>86% of butenes among which 99% of 1-butene). An increase of the steric bulk at the ortho position of the ligand or the introduction of a functional group led to decreased activity compared to [Ti(Oi-Pr)(4)].

Acetonitrile-[2-(1-{bis-[2,4,6-tris-(trifluoro-meth-yl)phen-yl]phosphan-yloxy}-1-methyl-eth-yl)pyridine]-methyl-palladium(II) hexa-fluoridoanti-monate dichloro-methane hemisolvate

In the title compound, [Pd(CH(3))(C(26)H(14)F(18)NOP)(C(2)H(3)N)][SbF(6)]·0.5CH(2)Cl(2), the Pd(2+) cation has a distorted square-planar environment, being coordinated by the acetonitrile [Pd-N = 2.078 (8) Å] and methyl [Pd-C = 2.052 (9) Å] groups and the bidentate ligand 2-(1-{bis-[2,4,6-tris-(trifluoro-meth-yl)phen-yl]phosphan-yloxy}-1-methyl-eth-yl)pyridine (L). In L, one -CF(3) group is rotationally disordered between two orientations in a 1:1 ratio. The solvent mol-ecule was treated as disordered between two positions related by an inversion center with occupancies fixed at 0.5. The crystal packing exhibits weak inter-molecular C-H⋯F contacts.