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Tetsuro Murahashi

Publications and source records attributed to Tetsuro Murahashi.

8 recordsLinked to original sources
PubMed2006

Discrete sandwich compounds of monolayer palladium sheets.

Despite the abundance of "sandwich" complexes, in which two cyclic aromatic hydrocarbon ligands flank a metal center, this motif has not been extended to sheets of multiple metal atoms. We prepared and isolated two such compounds. In the first, three palladium centers form a planar triangular array, capped by chlorides, between two cycloheptatrienyl ligands. In the second, a pentapalladium sheet adopts an edge-sharing triangle-trapezoid skeleton between two naphthacene rings. The compounds were characterized by x-ray crystallography and nuclear magnetic resonance spectroscopy. The nature of bonding in the clusters was analyzed by quantum calculations.

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PubMed2006

Stereoretentive elimination and trans-olefination of the dicationic dipalladium moiety [Pd2Ln]2+ bound on 1,3,5-trienes.

The reaction of [Pd(2)(CH(3)CN)(6)][BF(4)](2) (1) with 1,3,5-hexatriene, 1,6-diphenyl-1,3,5-hexatriene (DPHT), or 2,2,9,9-tetramethyl-3,5,7-decatriene (DBHT) afforded bi-eta(3)-allyldipalladium complexes 3, 4, or 5. The reaction of 1 and DBHT proceeded in a stereospecific (syn) manner when the reaction was carried out in CD(2)Cl(2) under aerobic conditions, while a mixture of two diastereomers was formed under N(2) atmosphere. The two diastereomers (5-E,Z,E-antifacial and 5-E,E,E-antifacial) formed from DBHT were isolated, and the structure of 5-E,Z,E-antifacial, which was kinetically formed from the reaction of 1 and (E,E,E)-DBHT, was determined by X-ray diffraction analysis. Addition of phosphine ligands (PPh(3) or dppm) to the dinuclear adduct 5-E,Z,E-antifacial or 5-E,E,E-antifacial in acetonitrile resulted in the stereospecific (syn) elimination of [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][BF(4)](2) (2) or [Pd(2)(dppm)(2)(CH(3)CN)(2)][BF(4)](2) (6). During the PPh(3)-induced dinuclear elimination, the phosphine adducts 7 that retain bi-eta(3)-allyldipalladium structure were observed initially. The phosphine adduct generated from 5-E,E,E-antifacial was isolated and structurally characterized by X-ray diffraction analysis. The reaction of 1 and DPHT in CH(2)Cl(2) afforded unique dipalladium sandwich compounds [Pd(2)(mu-eta(3):eta(3)-DPHT)(2)][BF(4)](2) (8). Interconversion between the sandwich complexes and half-sandwich complexes occurred in a stereoretentive manner. The structure of the sandwich complex 8-E,Z,E formed from 4-E,E,E-antifacial and (E,Z,E)-DPHT was determined by X-ray diffraction analysis. Transfer of the dipalladium moiety [Pd(2)(CH(3)CN)(4)](2+) from DPHT ligand of 4-E,E,E-antifacial onto DBHT ligand proceeded in a stereoretentive manner. The observed stereoretentive dinuclear process is featured by the pairwise behavior of two palladium atoms sitting on the triene pi-plane. In the dinuclear elimination, the two Pd atoms that are initially in the divalent state and bound on the opposite faces (antifacial) come to the synfacial positions to form a Pd-Pd bond prior to dissociation. These results represent the unique property of conjugated olefin as the multidentate ligands for metal-metal moieties.

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PubMed2003

Perylene-tetrapalladium sandwich complexes.

Bis-perylene-tetrapalladium sandwich complexes are synthesized and structurally characterized. These are the first examples of bis-arene sandwich complexes having metal-metal bond chains. X-ray crystallographic analyses showed that the tetrapalladium chain is bound to perylene ligands at the C8 edge position.

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PubMed2003

New direction in organopalladium chemistry: structure and reactivity of unsaturated hydrocarbon ligands bound to multipalladium units.

Examination of the manner of interaction between Pd(0) and allylpalladium(II) complexes, both being involved as key intermediates in Pd-catalyzed allylic coupling, led us to discover a new role for such combinations in affecting the stereochemistry of the transformations. A similar investigation of the system involving Pd(0) and allenyl/propargyl complexes of Pd(II) led to the discovery of dinuclear Pd(I)bond;Pd(I) complexes containing bridging allenyl/propargyl ligands, which exhibited novel structural and reactivity aspects of great synthetic significance. A systematic comparison was made between the structure, stability, and reactivity of allyl and allenyl/propargyl ligands in dinuclear complexes and those in mononuclear counterparts. On the basis of MO calculations, coordination behavior specific to the ligands of the dinuclear complex is attributed to the occurrence of the back-donating interaction from filled Pdbond;Pd bonding orbitals to vacant ligand pi* orbitals. Similar bonding features are the origin of the ready synthesis of novel one-dimensional sandwich complexes composed of conjugated polyene ligands and linear polypalladium chains. A substitutionally labile dipalladium complex reacts with an equimolar amount of trienes or alkynes to give formal [4pi + 2sigma] or [2pi + 2sigma] adducts, respectively, which undergo further unique transformations with additional unsaturated substrates.

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PubMed2002

Photoinduced face-inversion of conjugated tetraene ligands on a Pd-Pd-Pd moiety.

The linear sandwich tripalladium complexes [Pd3{Ar(CH=CH)4Ar}2[BArf]2 (Ar = Ph, p-t-Bu-C6H4, p-styryl-C6H4) undergo photoinduced isomerization involving face-inversion of the tetraene ligands. Irradiation of these complexes with visible light (>510 nm) resulted in rac (staggered sandwich) to meso (eclipsed sandwich) isomerization. The structures of rac and meso isomers are determined by X-ray crystallographic analyses.

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