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 CuI , AgI and AuI 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). CuI complex 2 [Cu4 Cl3 (bqmpp)2 ]BF4 contains a rarely observed Cu4 Cl3 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 31 P{1 H} NMR spectroscopy. During crystallization, instead of the expected phosphine complex 3, a tris(quinoline-2-ylmethyl)bisphenyl-phosphine (tqmbp) compound [Ag2 (tqmbp)2 ](SbF6 )2 4 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 AuI .

The Formation of P-C Bonds Utilizing Organozinc Reagents for the Synthesis of Aryl- and Heteroaryl-Dichlorophosphines.

Aryl- and heteroaryl-dichlorophosphines are mildly and selectively made in a one-pot synthesis in moderate to good yields starting from the respective aryl bromides or five-membered heterocycles, following lithiation with nBuLi, transmetalation with ZnCl2, and subsequently the reaction with PCl3. Selected aryl- and heteroaryl-dichlorophosphines were successfully synthesized using this reaction method and could easily be purified after isolation. The intermediate formation of the organozinc species is essential, as it prevents the formation of multiple substitution products. Important are also the reaction conditions: the usage of the proper solvent for the respective aromatic precursors and removal of the remaining salts by addition of a dioxane/pentane mixture. Depending on the solvent and steric demand of the substituent, mono- and bis-substitution products can be formed but formation also prevented. Hereby, different organozinc species might play an important role.

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.

Investigating Unusual Homonuclear Intermolecular "Through-Space" J Couplings in Organochalcogen Systems.

Although the electron-mediated spin-spin or J coupling is conventionally viewed as transmitted via covalent bonds, examples of J couplings between atoms that are not formally bonded but are in close proximity (termed "through-space" J couplings) have been reported. In this work, we investigate the observation of homonuclear 31P J couplings in organochalcogen heterocycles, which occur between 31P in two separate molecules, confirming without doubt their through-space nature. The presence of this interaction is even more surprising for one compound, where it occurs between crystallographically equivalent species. Although crystallographically equivalent species need not be magnetically equivalent in the solid state, owing to the presence of anisotropic interactions, we demonstrate that it is not the shielding anisotropy that lifts magnetic equivalence, in this case, but the presence of heteronuclear couplings to 77Se. We support our experimental observations with periodic scalar-relativistic density functional theory calculations and coupling density deformation plots to visualize the mechanism of these interesting interactions.

Diphosphane 2,2'-binaphtho[1,8-de][1,3,2]dithiaphosphinine and the easy formation of a stable phosphorus radical cation.

A convenient synthesis route to 2,2'-binaphtho[1,8-de][1,3,2]di-thiaphosphinine () was found. Its stable radical cation 3˙(+) was accessed easily through one-electron oxidation with NOBF4.