New chiral P-N ligands for the regio- and stereoselective Pd-catalyzed dimerization of styrene

Enantioselective Hydrophosphination of Terminal Alkenyl Aza-Heteroarenes

This paper presents a Mn(I)-catalysed methodology for the enantioselective hydrophosphination of terminal alkenyl aza-heteroarenes. The catalyst operates through H-P bond activation, enabling successful hydrophosphination of a diverse range of alkenyl-heteroarenes with high enantioselectivity. The presented protocol addresses the inherently low reactivity and the commonly encountered suboptimal enantioselectivities of these challenging substrates. As an important application we show that this method facilitates the synthesis of a non-symmetric tridentate P,N,P-containing ligand like structure in just two synthetic steps using a single catalytic system.

Coinage Metal Complexes of Bis(quinoline-2-ylmethyl)phenylphosphine-Simple Reactions Can Lead to Unprecedented Results

The different coordination behavior of the flexible yet sterically demanding, hemilabile P,N ligand bis(quinoline‐2‐ylmethyl)phenylphosphine (bqmpp) towards selected Cu^I, Ag^I and Au^I species is described. The resulting X‐ray crystal structures reveal interesting coordination geometries. With [Cu(MeCN)₄]BF₄, compound 1 [Cu₂(bqmpp)₂](BF₄)₂ is obtained, wherein the copper(I) atoms display a distorted square planar and square pyramidal geometry. The steric demand and π‐stacking of the ligand allow for a short Cu⋅⋅⋅Cu distance (2.588(9) Å). Cu^I complex 2 [Cu₄Cl₃(bqmpp)₂]BF₄ contains a rarely observed Cu₄Cl₃ cluster, probably enabled by dichloromethane as the chloride source. In the cluster, even shorter Cu⋅⋅⋅Cu distances (2.447(1) Å) are present. The reaction of Ag[SbF₆] with the ligand leads to a dinuclear compound (3) in solution as confirmed by ³¹P{¹H} NMR spectroscopy. During crystallization, instead of the expected phosphine complex 3, a tris(quinoline‐2‐ylmethyl)bisphenyl‐phosphine (tqmbp) compound [Ag₂(tqmbp)₂](SbF₆)₂4 is formed by elimination of quinaldine. The Au(I) compound [Au₂(bqmpp)₂]PF₆ (5) is prepared as expected and shows a linear arrangement of two phosphine ligands around Au^I.

Investigation of Structural Changes of Cu(I) and Ag(I) Complexes Utilizing a Flexible, Yet Sterically Demanding Multidentate Phosphine Oxide Ligand

The syntheses of a sterically demanding, multidentate bis(quinaldinyl)phenylphosphine oxide ligand and some Cu(I) and Ag(I) complexes thereof are described. By introducing a methylene group between the quinoline unit and phosphorus, the phosphine oxide ligand gains additional flexibility. This specific ligand design induces not only a versatile coordination chemistry but also a rarely observed and investigated behavior in solution. The flexibility of the birdlike ligand offers the unexpected opportunity of open-wing and closed-wing coordination to the metal. In fact, the determined crystal structures of these complexes show both orientations. Investigations of the ligand in solution show a strong dependency of the chemical shift of the CH₂ protons on the solvent used. Variable-temperature, multinuclear NMR spectroscopy was carried out, and an interesting dynamic behavior of the complexes is observed. Due to the introduced flexibility, the quinaldinyl substituents change their arrangements from open-wing to closed-wing upon cooling, while still staying coordinated to the metal. This change in conformation is completely reversible when warming up the sample. Based on 2D NMR spectra measured at -80 °C, an assignment of the signals corresponding to the different arrangements was possible. Additionally, the copper(I) complex shows reversible redox activity in solution. The combination of structural flexibility of a multidentate ligand and the positive redox properties of the resulting complexes comprises key factors for a possible application of such compounds in transition-metal catalysis. Via a reorganization of the ligand, occurring transition states could be stabilized, and selectivity might be enhanced.

Catalytic Approach toward Chiral P,N-Chelate Complexes Utilizing the Asymmetric Hydrophosphination Protocol

A synthetic procedure for obtaining a chiral P,N ligand was developed by exploiting the versatility of the asymmetric hydrophosphination protocol catalyzed by a phosphapalladacycle complex. The addition of the synthesized ligand to various metal sources led to the generation of chiral and enantioenriched chelate complexes, which can be useful prototypes for catalyst design in the future. The resulting coordination compounds were comprehensively characterized by solid-state (X-ray crystallography) and solution-based (one- and two-dimensional NMR spectroscopy) techniques and natural bond orbital (density functional theory) analysis to determine their structural and key electronic features.

Versatile Coordination Modes of Triphospha-1,4-pentadiene-2,4-diamine

1,3,5-Triphospha-1,4-pentadiene-2,4-diamine reacts with [M(CO)₄L] (M = Mo, L = nbd (norbornadiene); M = W, L = 2 CH₃CN) to give the chelate complexes [M(CO)₄(PMes{C(NHCy)PMes}₂-κ P¹ ,P³)]. In contrast, an unusual intramolecular rearrangement occurred with [Cu(CH₃CN)₄]PF₆ leading to the dimeric copper(I) complex [Cu(CNCy){PHMesPMesC(NHCy)PMes-κ P¹ ,P³}]₂(PF₆)₂. The mechanism of the rearrangement was supported by quantum-mechanical calculations. The transition-metal complexes were characterized by multinuclear NMR spectroscopy, mass spectrometry, infrared spectroscopy, and X-ray crystallography.