Synthesis, characterization, solution chemistry and anticancer activity of [NiCl2(Ph2P-N(R)-PPh2)] (R = 2-CH2Py, CH2Ph and p-tol) complexes

In this work three Ni²⁺ complexes with general formula [NiCl₂(Ph₂P-N(R)-PPh₂)], R = 2-CH₂Py (Py = pyridine) - 1, CH₂Ph (Ph = phenyl) - 2 and p-tol (p-tol = p-tolyl) - 3, were synthesized and characterized. These complexes were obtained in high yield by the reaction of NiCl₂.6H₂O and the corresponding diphenylphosphinoamine ligand (Ph₂P-N(R)-PPh₂) in CH₂Cl₂/MeOH (1:1) solution, at room temperature (∼25 °C), and characterized by ¹H and ³¹P {¹H} NMR, vibrational spectroscopy in the infrared region, electronic spectroscopy in the UV-Vis regions, elemental analysis (%C, %H, %N) and single-crystal X-ray diffraction. The solution chemistry was studied in CDCl₃/dmso-d⁶ (dimethylsulfoxide) or neat dmso-d⁶ using complex 2 as a model. The complexes were evaluated as cytotoxic agents against two cancer cells lines, A549 (lung cancer cells), B16F10 (melanoma cells) and the health cells HaCaT (human epithelial keratinocytes).

Effects of the halogenido ligands on the Kumada-coupling catalytic activity of [Ni{ t BuN(PPh2)2-κ2P}X2], X = Cl, Br, I, complexes

Novel nickel(ii) complexes bearing ( t butyl)bis(diphenylphosphanyl)amine and different halogenido ligands, [Ni(P,P)X2] = [Ni{ t BuN(PPh2)2-κ2P}X2], (X = Cl, Br, I) are prepared, characterized by IR and NMR spectroscopy, mass spectrometry and X-ray crystallography, and tested as catalysts in the Kumada cross-coupling reaction of model substituted iodobenzenes and p-tolylmagnesium bromide. The data obtained together with DFT calculations indicate that these new catalysts operate in the Ni(i)-Ni(iii) mode. The highest catalytic activity and selectivity are exhibited by [Ni(P,P)Cl2], which is most easily reduced by the used Grignard reagent to the Ni(i) state. This process is much more energy demanding in the case of the bromido and iodido complexes, causing the appearance of the induction period. [Ni(P,P)Cl2] is also very active in the cross-couplings of substrates with iodine atoms sterically shielded by ortho substituents. The data obtained are in good accordance with the described positive effect of the increased electron-releasing power of N-substituents R' on the overall catalytic performance of [Ni{R'N(PPh2)2-κ2P}X2] complexes.

Nickel Catalyzed Olefin Oligomerization and Dimerization

Brought to life more than half a century ago and successfully applied for high-value petrochemical intermediates production, nickel-catalyzed olefin oligomerization is still a very dynamic topic, with many fundamental questions to address and industrial challenges to overcome. The unique and versatile reactivity of nickel enables the oligomerization of ethylene, propylene, and butenes into a wide range of oligomers that are highly sought-after in numerous fields to be controlled. Interestingly, both homogeneous and heterogeneous nickel catalysts have been scrutinized and employed to do this. This rare specificity encouraged us to interlink them in this review so as to open up opportunities for further catalyst development and innovation. An in-depth understanding of the reaction mechanisms in play is essential to being able to fine-tune the selectivity and achieve efficiency in the rational design of novel catalytic systems. This review thus provides a complete overview of the subject, compiling the main fundamental/industrial milestones and remaining challenges facing homogeneous/heterogeneous approaches as well as emerging catalytic concepts, with a focus on the last 10 years.

Tetracarbonyl[N-(diphenylphosphanyl-κP)-N,N′-diisopropyl-P-phenylphosphorus diamide-κP]molybdenum(0) with an unknown solvent

The title complex, [Mo(C24H30N2P2)(CO)4], contains a molybdenum centre bearing a P,P′-cis-chelating Ph2PN( i Pr)P(Ph)NH( i Pr) and four carbonyl ligands in a distorted octahedral coordination geometry. This results in a nearly planar four-membered metallacycle. In the crystal, molecules are linked by N—H...O and C—H...O hydrogen bonds to form layers parallel to the ac plane. For the final refinement, the contributions of disordered solvent molecules were removed from the diffraction data with SQUEEZE in PLATON [Spek (2015). Acta Cryst. C71, 9–18]. The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s).

Chromium complexes bearing amidinato-phosphino ligand: synthesis, characterization, and catalytic properties of ethylene tri-/tetramerization and polymerization

An amidinato-phosphino ligand ArN[double bond, length as m-dash]C(R)NH(o-Ph₂PC₆H₄) (Ar = 2,4,6-Me₃C₆H₂, R = Ph (1); Ar = 2,6-iPr₂C₆H₃, R = Ph (2); Ar = 2,6-iPr₂C₆H₃, R = tBu (3)) was prepared. The ligand reacted with CrCl₃(THF)₃ to yield the N,P-chelation complex [ArNHC(R)[double bond, length as m-dash]N(o-Ph₂PC₆H₄)]CrCl₃(THF) (4-6), and the ligand's lithium salt ArN[double bond, length as m-dash]C(R)N(o-Ph₂PC₆H₄)Li reacted with the respective CrCl₃(THF)₃ and CrCl₂(THF)₂ to give the N,N,P-chelation complexes [ArN[double bond, length as m-dash]C(R)N(o-Ph₂PC₆H₄)]CrCl₂(THF) (7-8) and {[ArN[double bond, length as m-dash]C(R)N(o-Ph₂PC₆H₄)]Cr(μ-Cl)}₂ (9-11). Complexes 1-11 were characterized by IR, NMR (for 1-3), EPR (for 4-11) spectroscopy and CHN elemental analysis, of which 3, 5, 8, and 11 were further studied by X-ray crystallography. Upon activation with an organoaluminum cocatalyst, complexes 4-6 were all catalytically active in ethylene tri-/tetramerization along with ethylene polymerization, and complexes 7-11 functioned as well but in ethylene polymerization. The correlation between the structure and the catalytic properties of the catalyst system is discussed.

Zwitterionic Cobalt Complexes with Bis(diphenylphosphino)(N-thioether)amine Assembling Ligands: Structural, EPR, Magnetic, and Computational Studies

The coordination of two heterofunctional P,P,S ligands of the N-functionalized DPPA-type bearing an alkylthioether or arylthioether N-substituent, (Ph2P)2N(CH2)3SMe (1) and (Ph2P)2N(p-C6H4)SMe (2), respectively, toward cobalt dichloride was investigated to examine the influence of the linker between the PNP nitrogen and the S atoms. The complexes [CoCl2(1)]2 (3) and [CoCl2(2)]2 (4) have been isolated, and 3 was shown by X-ray diffraction to be a unique dinuclear, zwitterion containing one CoCl moiety bis-chelated by two ligands 1 and one CoCl3 fragment coordinated by the S atom of a thioether function. The FT-IR, UV-vis, and EPR spectroscopic features of 3 were analyzed as the superposition of those of constitutive fragments identified by a retrosynthetic-type analysis. A similar approach provided insight into the nature of 4 for which no X-ray diffraction data could be obtained. A comparison between the spectroscopic features of 4 and of its constitutive fragments, [CoCl(2)2]PF6 (7) and [H2']2[CoCl4] (8) (2' = NH2(p-C6H4)SMe), and between those of 4 and 3 suggested that 4 could either have a zwitterionic structure, similar to that of 3, or contain a tetrahedral dicationic bis-chelated Co center associated with a CoCl4 dianion. Magnetic and EPR studies and theoretical calculations were performed. Doublet spin states were found for the pentacoordinated complexes [CoCl(1)2]PF6 (5) and 7 and anisotropic quadruplet spin states for the tetrahedral complexes [CoCl3(H1')] (6) (1' = NH2(CH2)3SMe) and 8. A very similar behavior was observed for 3 and 4, consisting in the juxtaposition of noninteracting doublet and quadruplet spin states. Antiferromagnetic interactions explain the formation of dimers for 6 and of layers for 8. The EPR signatures of 3 and 4 correspond to the superposition of low-spin nuclei in 5 and 7 and high-spin nuclei in 6 and 8, respectively. From DFT calculations, the solid-state structure of 4 appears best described as zwitterionic, with a low-spin state for the Co1 atom.

Highly active chromium-based selective ethylene tri-/tetramerization catalysts supported by PNPO phosphazane ligands

Cr(iii) catalysts supported by PNPO ligands are highly active for ethylene tri-/tetramerization with considerable selectivity upon activation with MMAO-3A and a highest activity of 316.7 kg (g Cr h⁻¹)⁻¹.

Comparative study of new chromium-based catalysts for the selective tri- and tetramerization of ethylene

Small changes in ligand structure and conditions make a chromium ethylene oligomerization catalyst to switch from 1-hexene to 1-octene selectivity.

Crystal structure of tricarbon-yl(N-di-phenyl-phosphanyl-N,N'-diisopropyl-P-phenyl-phospho-nous di-amide-κ(2) P,P')cobalt(I) tetra-carbonyl-cobaltate(-I) toluene 0.25-solvate

The title compound {Co(CO)₃[Ph₂PN(i-Pr)P(Ph)N(H)i-Pr]}[Co(CO)₄] is an ionic species consisting of a Co(CO)₃[Ph₂PN(i-Pr)P(Ph)N(H)i-Pr] cation and a [Co(CO)₄] anion.

The asymmetric unit of the title compound, [Co(C₂₄H₃₀N₂P₂)(CO)₃][Co(CO)₄]·0.25C₇H₈, consists of two crystallographically independent cations with similar conformations, two anions, and one-half of a toluene mol­ecule disordered about an inversion centre. In the cations, a Co/P/N/P four-membered slightly bent metallacycle is the key structural element. The pendant NH group is not coordinated to the Co^I atom, which displays a distorted trigonal–bipyramidal coordination geometry. Weak inter­ionic hydrogen bonds are observed between the NH groups and a carbonyl group of the tetrahedral [Co(CO)₄]⁻ anions.

Isolation of a hexanuclear chromium cluster with a tetrahedral hydridic core and its catalytic behavior for ethylene oligomerization

A chromium complex [2-(NHCH2PPh2)C5H4N]CrCl3·THF2 (1) of the ligand PyNHCH2PPh2 has been synthesized, characterized, and examined for its catalytic behavior toward ethylene oligomerization. When complex 1 was treated with (i-Bu)3Al, an unprecedented divalent polyhydride chromium cluster μ,κ(1),κ(2),κ(3)-N,N,P-{[2-(NCH2PPh2)C5H4N]Cr(μ-H)}4[(μ-Cl)Cr(μ-Cl)Al(i-Bu)2Cl]2 (2) was obtained. The complex contains a Cr4H4 core, which is expected to be diamagnetic, and which remains coordinated to two additional divalent high-spin Cr atoms via bridging interactions. Two aluminate residues remain bonded to the peripheral chromium atoms. The structure, magnetism, and electronic configuration are herein discussed.

A survey of pendant donor-functionalised (N,O) phosphine ligands for Cr-catalysed ethylene tri- and tetramerisation

Selected phosphine-based ligands plus chromium have been found to be promising candidates for MAO-free trimerisation and tetramerisation of ethylene.