Sandra Loss

Phosphiranes as Ligands for Platinum Catalysed Hydrosilylations

Abstract The stability of phosphiranes can be enhanced by inclusion of the PC2 ring into a polycyclic framework. BABAR-Phos type phosphiranes are easily prepared in high yield, they are thermally stable and allow the synthesis of various platinum(0) complexes. In contrast to other platinum(0) phosphine complexes, these are active hydrosilylation catalyst precursors. The reversible insertion of an electron rich metal centre into one P–C bond of the phosphirane ring was demonstrated for the first time.

VERY STABLE PHOSPHIRANES

Zero-valent platinum complexes as precursors for hydrosilylation catalysts have been prepared for the first time with the new BABAR-Phos ligands (the structure of one such complex is depicted). These rather stable phosphiranes can be obtained when the three-membered PC2 ring is incorporated into a polycyclic cage.

Strong P=P π Bonds: The First Synthesis of a Stable Phosphanyl Phosphenium Ion

A 35-fold excess of methyl triflate (2) is required to quantitively prepare 3, the first phosphanyl phosphenium ion, from diphosphene 1. Experimental data and calculations indicate that the P=P bond becomes stronger upon alkylation.

Coordination chemistry of phosphanyl amino acids: solid state and solution structures of neutral and cationic rhodium complexes

Copper phosphide or arsenide complexes, [Cu(EPh(2))(neo)] (E = P, As, neo = 2,9-dimethyl-1,10-phenanthroline; trivial name: neocuprine) react selectively with the N-protected brominated serine derivatives, 2-(S)-(alkoxycarbonylamino)-3-bromomethylpropionates ((ROCO)SerBr, : R = PhCH(2), : tBu, : Me) to give the corresponding phosphanylated or arsanylated amino acids, (ROCO)SerPhos (: Phos = PPh(2)) and (Z)SerArs (Ars = AsPh(2), Z = PhCH(2)OCO). The dipeptide (Z)AlaSerPhos was likewise prepared. The phosphanes , and the arsane reacted cleanly with [Rh(2)(micro-Cl)(2)(cod)(2)] to give the rhodium(I) complexes [RhCl(cod)((Z)SerPhos)] , [RhCl(cod)((Boc)SerPhos)] (Boc = tBuOCO), [RhCl(cod)((Z)AlaSerPhos)] , and [RhCl(cod)((Z)SerArs)] which were characterized by X-ray diffraction studies. A common structural feature is an intramolecular (N)H[dot dot dot]Cl(Rh)-hydrogen bridge which according to NMR investigations remains intact in solution. The abstraction of chloride from the coordination sphere of Rh(I) in or has a profound structural impact. While in and , the ligands bind in a monodentate fashion, via the phosphorus atom only, they serve as bidentate ligands via the phosphorus centre and the peptidic C=O group in [Rh(cod)(kappa(2)-(Z)SerPhos)]PF(6) and [Rh(cod)(kappa(2)-(Z)AlaSerPhos)]PF(6). This causes also the amino acid residue structures to change from alpha-helix type in and to a beta-sheet type in both. Addition of chloride to and fully re-establishes the structures of both. The complexes [RhCl(cod)((Z)SerPhos)] and [RhCl(cod)((Boc)SerPhos)] show good activities in homogeneously catalyzed hydrogenations of olefins while the dipeptide complex is less active. Phosphane addition to greatly diminishes the catalytic activity. The cationic complex [Rh(cod)(kappa(2)-(Z)AlaSerPhos)]PF(6) shows low activity which, however, is greatly increased by addition of one equivalent of phosphane.

Starke P=P‐π‐Bindungen: die erste Synthese eines stabilen Phosphanylphospheniumions

Erst ein 35facher Uberschus an Methyltriflat 2 bei der Reaktion mit dem Diphosphen 1 fuhrt zur quantitativen Bildung von 3, dem ersten Phosphanylphospheniumion. Experimentelle und theoretische Befunde sprechen dafur, das die P=P-Bindung durch Alkylierung verstarkt wird.

AN UNUSUAL REACTION OF HEXAFLUOROACETONE WITH METHYLENEDIPHOSPHANES : FACILE SYNTHESIS OF CARBODIPHOSPHORANES

The oxidation of the methylenediphosphanes 3a,b with hexafluoroacetone does not lead to the expected dioxaphospholane heterocycles, but yields quantitatively the carbodiphosphoranes 5a,b. Compounds 5a,b easily add HCl, HF or Cl2 to the ylidic bonds. The chloro derivative 14b, and its analogue 17 were used for the synthesis of phosphonium substituted carbenes.

Ligands Make the Catalyst: Synthesis of Novel Functionalized Phosphines

Many catalytic active transition metal complexes contain phosphines as ligands which control decisively the activity and selectivity of the catalyst. Therefore synthetic methods which allow the preparation of highly functionalized phosphines are needed to match the increasing demands for higher activity and selectivity in catalytic processes. In this report we introduce a simple general new method for the synthesis of phosphines, arsines, and stibines. This allowed for example the preparations of phosphines based on serine and thymine derivatives (SerPhos and ThymPhos, respectively).

Synthesis of stable monomeric iridium(0) and iridium(–1) complexes

Using the troppPh ligand 1, stable monomeric d8-Ir+I, d9-Ir0 and d10-Ir–I complexes could be isolated and structurally characterized; in all complexes, the metal centre lies within a coordination sphere intermediate between a square plane and a tetrahedron.

Synthesis and Coordination Chemistry of Novel Phosphiranes

Abstract Three-membered PC2 heterocycles may find interesting applications in tansition metal catalysis but are intrinsically unstaMelll. We developed an efficient simple synthesis of a tricydic phosphirane 3 (BABAR-Phos) which is indefinitely stable in substance at room temperature and may be handled on air (Scheme 1).