Synthesis and coordination chemistry of enantiopure t-BuMeP(O)H.

Both enantiomers of the optically pure Secondary Phosphine Oxide (SPO) t-BuMeP(O)H (1) have been obtained by deboronation of phosphinous acid-borane t-BuMeP(O)H·BH3 (3) with HBF4 followed by hydrolysis of the intermediate adduct t-BuMeP(O)H·BF3 (1·BF3), which has been isolated and crystallographically characterised. Complexes [MCl(COD)(κP-(R)-1)] (M = Ir, Rh; 4 and 7 respectively) have been detected in solution but could not be isolated while trans-[RhCl(CO)(κP-(S)-1)2] (9) has been successfully obtained in good yield. Gold complex [AuCl(κP-(S)-1)] (10) has been prepared and its crystal structure shows the presence of aurophilic interactions. Three new ruthenium complexes ([RuCl2(η6-p-cymene)(κP-(R)-1)], 12), ([RuCl2(CO)3(κO-(S)-1)], 13) and trans-([RuCl2(CO)2(κP-(S)-1)2], 14) have been synthesised and fully characterised, including the crystal structure of 12. Four palladium coordination compounds have been prepared: trans-[PdCl2(κP-(S)-1)2] (trans-15), [Pd(µ-Cl)(κP-(S)-1)2]2 (16·OH and 16·BF2) and [Pd(µ-OAc)(κP-(S)-1)2] (17) and the crystal structure of complex 16·OH proves the pseudobidentate coordination of the two molecules of 1. Three organometallic allylpalladium complexes have been prepared namely [Pd(η3-Ph2C2H3)Cl(κP-(S)-1)] (18) and [Pd(η3-Ph2C2H3)(κP-(S)-1)2] (19·OH and 19·BF2). The crystal structure of 19·BF2 constitutes the first allylpalladium-SPO complex reported to date.

Highly Enantioselective Iridium-Catalyzed Hydrogenation of Cyclic Enamides.

The MaxPHOX-Ir catalyst system provided the highest selectivity ever reported for the reduction of cyclic enamides derived from α- and ß-tetralones. This result indicates that iridium catalysts are also proficient in reducing alkenes bearing metal-coordinating groups. In the present system, selectivity was pressure-dependent: In most cases, a decrease in the H2 pressure to 3 bar resulted in an increase in enantioselectivity. Moreover, the process can be carried out in environmentally friendly solvents, such as methanol and ethyl acetate, with no loss of selectivity.

Stereospecific S(N)2@P reactions: novel access to bulky P-stereogenic ligands.

The stereospecific hydrolysis of bulky aminophosphine boranes is reported for the first time. The resulting phosphinous acid boranes, upon activation, undergo stereospecific nucleophilic substitution reaction at the phosphorous center with amine nucleophiles. The combination of these two processes provides a novel access to bulky P*-ligands.

Asymmetric intermolecular cobalt-catalyzed Pauson-Khand reaction using a P-stereogenic bis-phosphane.

The asymmetric intermolecular and catalytic Pauson-Khand reaction has remained an elusive goal since Khand and Pauson discovered this transformation. Using a novel family of P-stereogenic phosphanes, we developed the first catalytic system with useful levels of enantioselection for the reaction of norbornadiene and trimethylsilylacetylene. The results demonstrate that Co-bisphosphane systems are sufficiently reactive and that they lead to high selectivity in the intermolecular process.

Borane as an efficient directing group. Stereoselective 1,2-addition of organometallic reagents to borane P-stereogenic N-phosphanylimines.

In non-coordinating solvents, borane was shown to be an efficient directing group for the stereoselective 1,2-addition of organolithium reagents to P-stereogenic N-phosphanylimines. Selectivity was reversed in coordinating solvents. This process can lead to novel ligand scaffolds for asymmetric catalysis.