Ana M. Martín Castro

Cluster build-up reactions via the ionic coupling of tetraosmium anions and the [RhCp*(NCMe)3]2+ cation; the crystal and molecular structures of [Os4Rh(μ-H)3(MeCNH)(CO)11(η5-Cp*)], [Os4Rh(μ-H)2(CO)13(η5-Cp*)] and [Os4Rh2(μ-H)2(CO)11(η5-Cp*)2] (Cp*C5Me5)

Abstract The reaction of [Os4H4(CO)11]2− 2, formed by the reduction of [Os4H4(CO)12] 1 with K/Ph2CO, with the cation [Rh(η5-Cp*)(MeCN)3]2+ (Cp*C5Me5) 3, affords a number of penta- and hexanuclear mixed-metal clusters depending on the reaction conditions. If only sufficient K/Ph2CO is added to dissolve all of 1, and the dication 3 added, a low yield of a blue cluster [Os4Rh(μ-H)3(MeCNH)(CO)11(η5-Cp*)] (Cp*C5Me5) 4 is obtained in addition to large quantities of 1. If an excess of K/Ph2CO is added so that reduction of 1 is complete, and then the dication 3 added, two new products [Os4Rh(μ-H)2(CO)13(η5-Cp*)] 5 and [Os4Rh2(μ-H)2(CO)11(η5-Cp*)2] 6 are obtained in low yield. The three new complexes have been characterised spectroscopically and crystallographically. Cluster 4 contains the uncommon MeCNH group coordinated to an edge-bridged tetrahedral metal framework. The metal framework in 5 is also a Rh edge-bridged Os4 tetrahedron while that of 6 is a bicapped tetrahedron, with two Rh atoms face capping two faces of an Os4 tetrahedron.

Cluster Build-Up Reactions Using Di-gold Cationic Fragments: Synthesis and Structural Characterization of [Os~7(CO)~1~9(Au~2dppm)]

The reaction of the di-gold cation [Au2(dppx)]2+ with the heptanuclear cluster dianion [Os7(CO)20]2− affords the mixed metal cluster [Os7(CO)20{Au2(dppx)}] (x=m (1), e (2), b (3)). On standing, in solution, this complex undergoes decarbonylation to give the cluster [Os7(CO)19{Au2(dppx)}] (x=m (4), e (5), b (6)). The complexes have been characterised spectroscopically, and an X-ray structure determination of the dppm derivative shows that it contains a metal core based on an Os7 edge-bridged bicapped tetrahedron with the two μ3-Au atoms capping adjacent triangular Os3 faces of the central tetrahedron. In an analogous reaction, the carbido anion [Os7(H)C(CO)19]− affords the neutral cluster [Os7C(CO)19{Au2(dppm)}] (7) when treated with [Au2(dppm)]2+ in the presence of base.

Highly stereoselective additions of sulfur stabilized carbanions to [(S)R]-2-(p-tolylsulfinyl)cyclohexanones

Abstract We describe the addition reactions of α-thiocarbanions derived from sulfoxides, thioethers, and sulfones to 2-(p-tolylsulfinyl)cyclohexanones. The high stereoselectivity observed in the formation of the chiral hydroxylic carbon is controlled by the configuration of the sulfinyl group at the substrate, but it is modulated by the nature of the sulfur function at the reagent (SOTol>SO2Ph>SPh). The highly stereoselective formation of the second stereogenic center generated in these reactions from prochiral anions is only achieved with sulfinylcarbanions, the configuration of which controls that of such a center.

Efficient Enantioselective Synthesis of Cyclopropanes from Sulfonylpyrazolines

Abstract