Iminophosphines: synthesis, formation of 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and N-(pyridin-2-yl)-2-diphenylphosphinoylaniline, coordination chemistry and applications in platinum group catalyzed Suzuki coupling reactions and hydrosilylations

Enantioselective hydrosilylation of unsaturated carbon-heteroatom bonds (C[double bond, length as m-dash]N, C[double bond, length as m-dash]O) catalyzed by [Ru-S] complexes: a theoretical study

A detailed theoretical study on the mechanism of enanthioselective hydrosilylation of imines and ketones catalyzed by the ruthenium(ii) thiolate catalyst [Ru–S] ([L*-Ru(SDmp)]⁺[BAr₄^F]⁻) with a chiral monodentate phosphine ligand is carried out in this work. We elucidate all the pathways leading to the main products or by products mediated by the [Ru–S] complex in order to have deep understanding of the chemoselectivity and enantioselectivity. The DFT (Density Functional Theory) calculations show that the reaction mechanism including: (1) Si–H bond cleavage by the dual activity of Ru–S bond; (2) the generation of a sulfur-stabilized silane cation; (3) the electrophilic attack of silane cation to NC/OC; (4) hydrogen transfer from Ru to carbon cation. The hydrosilylation products are found to be the final products rather than the dehydrogenative ones, which is consistent with the experimental results. The dehydrogenative silylation reaction pathways which give N- or O-silylated enamine/enol ether are reversible according to our calculations. The computational results also show that the electrophilic attack of silicon to NC/OC is the rate-determining step and the ee value can be improved significantly with more bulky model phosphine ligand based on the same calculation methods.

A detailed theoretical study on the mechanism of enanthioselective hydrosilylation of imines and ketones catalyzed by the ruthenium(ii) thiolate catalyst with a chiral monodentate phosphine ligand is carried out in this work.

Versatile Coordination and C-C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0)

Ligands that can adapt their coordination mode to the electronic properties of a metal center are of interest to support catalysis or small molecule activation processes. In this context, the ability of imine moieties to bind in either an η¹(N)-fashion via σ-donation of the lone pair or, less commonly, in an η²(C,N)-fashion via π-coordination is potentially attractive for the design of new metal–ligand cooperative systems. Herein, the coordination chemistry of chelating ligands with a diphosphine imine framework (PCNP) to nickel is investigated. The imine moiety binds in an η¹(N)-fashion in a Ni(II)Cl₂ complex. The uncommon η²(C,N)-interaction is obtained in Ni(0) complexes in the presence of a PPh₃ coligand. Increasing the bulk on the phosphine side-arms in the Ni(0) complexes, by substituting phenyl for o-tolyl groups, leads to a distinct binding mode in which only one of the phosphorus atoms is coordinated. In the absence of a coligand, a mixture of two different dimeric Ni(0) complexes is formed. In one of them, the imine adopts an uncommon η¹(N)η²(C,N) bridging mode of the ligand to nickel, while the second one may involve reactivity on the ligand by the formation of a new C–C bond by oxidative coupling. The latter is supported by the isolation and structural characterization of a crystalline bis-CO derivative featuring a C–C bond formed by oxidative coupling of two imine moieties.

The coordination chemistry of a series of diphosphine-imine ligands (PCNP) to Ni is investigated, with the purpose of developing systems that present metal−ligand cooperativity. The ligands bind in versatile ways, adapting to the oxidation state and coordination environment of the metal center. Additionally, a dimeric derivative undergoes oxidative C−C coupling in the presence of CO, resulting in an unusual mixed valence Ni(II)/Ni(0) dinuclear complex.

An imidazolium ionic compound-supported palladium complex as an efficient catalyst for Suzuki–Miyaura reactions in aqueous media

A water soluble and efficient ionic compound-supported palladium complex was prepared.

Phosphine-iminopyridines as platforms for catalytic hydrofunctionalization of alkenes

A series of phosphine-diimine ligands were synthesized by the condensation of 2-(diphenylphosphino)aniline (PNH2) with a variety of formyl and ketopyridines. Condensation of PNH2 with acetyl- and benzoylpyridine yielded the Ph2P(C6H4)N═C(R)(C5H4N), respectively abbreviated PN(Me)py and PN(Ph)py. With ferrous halides, PN(Ph)py gave the complexes FeX2(PN(Ph)py) (X = Cl, Br). Condensation of pyridine carboxaldehyde and its 6-methyl derivatives with PNH2 was achieved using a ferrous template, affording low-spin complexes [Fe(PN(H)py(R))2](2+) (R = H, Me). Dicarbonyls Fe(PN(R)py)(CO)2 were produced by treating PN(Me)py with Fe(benzylideneacetone)(CO)3 and reduction of FeX2(PN(Ph)py) with NaBEt3H under a CO atmosphere. Cyclic voltammetric studies show that the [FeL3(CO)2](0/-) and [FeL3(CO)2](+/0) couples are similar for a range of tridentate ligands, but the PN(Ph)py system uniquely sustains two one-electron reductions. Treatment of Fe(PN(Ph)py)X2 with NaBEt3H gave active catalysts for the hydroboration of 1-octene with pinacolborane. Similarly, these catalysts proved active for the addition of diphenylsilane, but not HSiMe(OSiMe3)2, to 1-octene and vinylsilanes. Evidence is presented that catalysis occurs via iron hydride complexes of intact PN(Ph)py.

Highly efficient hydrogenation of carbon dioxide to formate catalyzed by iridium(iii) complexes of imine-diphosphine ligands

A new iridium catalyst containing an imine-diphosphine ligand has been developed, which showed high efficiency for the hydrogenation of CO₂ to formate (yield up to 99%, TON up to 450 000). A possible catalytic mechanism is proposed, in which the imine group of the catalyst plays a key role in the cleavage of H₂ and the activation of CO₂.

Dichlorido{N-[2-(diphenylphosphanyl)benzylidene]-2-methylaniline}palladium(II) acetonitrile monosolvate

The title imino–phosphine compound, [PdCl2(C26H22NP)]·CH3CN, was prepared by reaction ofN-[2-(diphenylphosphanyl)benzylidene]-2-methylaniline with dichlorido(cycloocta-1,5-diene)palladium(II) in dry CH2Cl2. The PdIIcation is coordinated by the P and N atoms of the bidentate chelating ligand and by two chloride anions, generating a distorted square-planar coordination geometry. There is a detectabletransinfluence for the chloride ligands. The methyl group present in this structure has an influence on the crystal packing.

Dichlorido{2-[(2,6-diethylphenyl)iminomethyl]quinoline-κ2N,N′}palladium(II) acetonitrile monosolvate

The title complex, [PdCl2(C20H20N2)]·CH3CN, was synthesized by the reaction of 2-[(2,6-diethylphenyl)iminomethyl]quinoline with dichlorido(cycloocta-1,5-diene)palladium(II) in dry CH2Cl2. The PdIIion is coordinated by two N atoms of the bidentate quinoline ligand and by two chloride anions, generating a distorted square-planar coordination geometry around the metal centre. There is a detectabletransinfluence for the chloride ligands. The crystal packing is characterized by π–π stacking between the quinoline rings. The use of acetonitrile as the crystallization solvent was essential for obtaining good-quality crystals.

Dichlorido[2-(phenyl-imino-meth-yl)quinoline-N,N']palladium(II)

In the title complex, [PdCl(2)(C(16)H(12)N(2))], the Pd(II) ion is coordinated by two N atoms [Pd-N 2.039 (2), 2.073 (2) Å] from a bidentate ligand and two chloride anions [Pd-Cl 2.2655 (7), 2.2991 (7) Å] in a distorted square-planar geometry. In the crystal, π-π inter-actions between the six-membered rings of the quinoline fragments [centroid-centroid distances = 3.815 (5), 3.824 (5) Å] link two mol-ecules into centrosymmetric dimers.

Dichlorido{2-[(thio-phen-2-ylmeth-yl)imino-meth-yl]pyridine-κN,N'}palladium(II)

In the title compound, [PdCl₂(C₁₁H₁₀N₂S)], the Pd^II ion is four-coordinated in a distorted square-planar environment by two N atoms of the chelating 2-[(thio­phen-2-ylmeth­yl)imino­meth­yl]pyridine ligand and two chloride anions. The thio­phene ring is rotationally disordered over two orientations in a 1:1 ratio. The crystal packing exhibits weak inter­molecular C—H⋯Cl and C—H⋯S hydrogen bonds.

Dichlorido{[2-(diphenyl-phosphino)phenyl-imino-meth-yl]ferrocene-κN,P}palladium(II) dichloro-methane hemi-solvate

There are two independent Pd(II) complex mol-ecules in the asymmetric unit of the title compound, [PdCl(2){Fe(C(5)H(5))(C(24)H(19)NP)}]·0.5CH(2)Cl(2). One ferrocenyl ring of one complex mol-ecule is disordered over two sites with half-occupancy for each component. Both Pd(II) cations adopt a distorted square-planar coordination geometry with a bidentate [2-(diphenyl-phosphino)phenyl-imino-meth-yl]ferrocene ligand and two chloride anions.

Synthesis of a chelating hexadentate ligand with a P3N3 donor set. Crystal and molecular structure of [OC-6-22]-[Co{(RP*,RP*,RP*)-CH3C(CH2PPhC6H4NH2-2)3}](PF6)3

The first structurally authenticated example of a hexadentate chelating tertiary phosphine in which all six donors are bound to a single metal centre is described. The multidentate ligand (RP*,RP*,RP*)- and (RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3 has been prepared in 80% yield via the reaction of five equivalents of sodium (2-aminophenyl)phenylphosphide (generated in situ from (2-aminophenyl)phenylphosphine and sodium in thf) with 1,1,1-tri(bromomethyl)ethane in thf. The diastereomeric mixture has been complexed to cobalt(III) and the resulting pair of complexes, viz. [Co{(RP*,RP*,RP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl3 and [CoCl{(RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl2, separated by ion exchange chromatography. The structure of the former (as the corresponding hexafluorophosphate salt) has been confirmed by X-ray crystallography and clearly shows all six donors of the P3N3 ligand coordinated to a single cobalt(III) centre. The related hexadentate ligand with internal N donors and terminal diphenylphosphino groups, viz. CH3C(CH2NHC6H4PPh2-2)3, has also been synthesised, albeit in low yield, via the reaction of [Li(tmeda)][2-NHC6H4PPh2] (generated in situ from (2-aminophenyl)diphenylphosphine, n-butyllithium and tmeda in diethyl ether) with 1,1,1-tri(iodomethyl)ethane in thf. No formation of a P3N3 ligand has been observed when either Na[2-PPhC6H4NH2] or [Li(tmeda)][2-NHC6H4PPh2] is reacted with the related tripodal substrate 1,1,1-tris(tolyl-4-sulfonyloxymethyl)ethane in thf. Rather the P-methyloxetane (+/-)-[3-{(2-aminophenyl)phenylphosphinomethyl}]-3-methyloxetane and the sulfonamide 2-(4-CH3C6H4SO2)NHC6H4PPh2 and the corresponding N-methyloxetane [3-{(2-diphenylphosphinophenyl)aminomethyl}]-3-methyloxetane have been isolated from the respective reactions. The structure of the sulfonamide has been confirmed by an X-ray analysis of the platinum(II) complex trans-[PtCl(CH3){2-PPh2C6H4NH(SO2C6H4CH(3-4)}2].