Showing papers by "Martin Murray published in 1988"

Stereochemical course of the action of the cellobioside hydrolases I and II of Trichoderma reesei

Abstract: With β-cellobiosyl fluoride as substrate, CBHI gives β-cellobiopyranose as the first product, whereas CBHI gives α-cellobiopyranose (CBH = cellobioside hydrolase).

The heteronuclear cluster chemistry of the group 1B metals. Part 9. Stereochemical non-rigidity of the metal skeletons of cluster compounds in solution. 109Ag-{1H} INEPT nuclear magnetic resonance studies on [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1, 2, or 4) and X-ray crystal structure of [Ag2Ru4(µ3-H)2(µ-Ph2PCH2PPh2)(CO)12]

Abstract: A combination of spectroscopic data and an X-ray diffraction study on [Ag2Ru4(µ3-H)2(µ-Ph2PCH2PPh2)(CO)12][Ag–Ag 2.756(6), Ag–Ru 2.820(6)–3.151(6), Ru–Ru 2.775(7)—2.998(6)A] shows that the clusters [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1–6) all adopt a capped trigonal-bipyramidal metal core geometry. However, although there are two distinct silver sites in the ground-state structures, ambient temperature 109Ag-{1H} INEPT n.m.r. spectra of the clusters in which n= 1, 2, or 4 show a single averaged silver resonance in each case. These studies provide the first direct evidence for stereochemical non-rigidity of the metal skeletons of Group 1B metal heteronuclear clusters in solution. In addition, values of 1J(107,109Ag107,109Ag) have been measured for the first time. The results of 31P-{109Ag} and 109Ag INEPT and DEPT n.m.r. studies on [AgRu4(µ3-H)3(CO)12(PPh3)] are also reported.

The heteronuclear cluster chemistry of the group 1B metals. Part 10. Synthesis, structures, and dynamic behaviour of the bimetallic hexanuclear group 1B metal cluster compounds [M2Ru4(µ3-H)2{µ-Ph2As(CH2)nEPh2}(CO)12](M = Cu or Ag; E = As or P; n= 1 or 2). X-Ray crystal structure of [Cu2Ru4(µ3-H)2{µ-Ph2As(CH2)2PPh2}(CO)12]

Abstract: Treatment of a dichloromethane solution of the salt [N(PPh3)2]2[Ru4(µ-H)2(CO)12] with two equivalents of the complex [M(NCMe)4]PF6(M = Cu or Ag) at –30 °C, followed by the addition of one equivalent of the appropriate bidentate ligand Ph2As(CH2)nEPh2(E = As or P; n= 1 or 2) affords the mixed-metal cluster compounds [M2Ru4(µ3-H)2{µ-Ph2As(CH2)nEPh2}(CO)12][M = Cu, E = P, n= 1 (1) or 2 (2); M = Ag, E = P, n= 1 (3) or 2 (4); M = Cu, E = As, n= 1 (5) or 2 (6); M = Ag, E = As, n= 1 (7) or 2 (8)] in ca 60–75% yield A single-crystal X-ray diffraction study on (2) reveals that the metal skeleton consists of a tetrahedron of ruthenium atoms capped by a Cu atom [Group 1B metal site M(2)], with one of the CuRu2 faces of the CuRu3 tetrahedron so formed further capped by the second Cu atom [Group 1B metal site M(1)] to give a capped trigonal-bipyramidal metal core geometry The other two CuRu2 faces of the cluster are both capped by triply bridging hydrido ligands, each ruthenium atom carries three terminal CO groups, and the Ph2As(CH2)2PPh2 ligand bridges the Cu–Cu vector Disorder between As and P atoms suggests that two distinct structural isomers, the major one with the As atom attached to Cu(2) and the minor one with the As atom bonded to Cu(1), exist in the solid state Spectroscopic data imply that (1) and (3)–(8) all adopt similar metal framework structures to (2) Variable-temperature 1H and 31P-{1H} nmr studies demonstrate that two structural isomers exist in solution at low temperatures for both copper–ruthenium clusters (1) and (2) and that each of these pairs of isomers undergoes interconversion at ambient temperature by a dynamic process involving an intramolecular metal core rearrangement The silver–ruthenium clusters (3) and (4) undergo similar dynamic behaviour at –30°C, but no spectra consistent with the ground-state structures could be obtained at lower temperatures At higher temperatures, (3) and (4) both undergo two additional dynamic processes The first involves a novel intramolecular exchange of the arsenic and phosphorus atoms in the Ph2As(CH2)nPPh2 ligands between the two silver atoms in each cluster and, as the temperature is raised further, the bidentate ligands undergo intermolecular exchange between clusters Nmr spectroscopic data suggest that (6)–(8), which contain Ph2As(CH2)nAsPh2 ligands, also undergo fluxional processes involving Group 1B metal site-exchange at ambient temperature in solution and this behaviour has been directly observed for (7) by 109Ag-{1H} INEPT nmr spectroscopy

The Reaction of a Zwitterionic Diphosphorus Compound with the Platinum(0) Complex, (C2H4)Pt(PPh3)2.

Abstract: The oxidation—reduction reaction between a zwitterionic diphosphorus compound, involving the grouping ClP(−)P(+)NEt2 with the platinum(0) complex, (C2H4)Pt(PPh3)2, has furnished a novel platinum(II) complex with a PP four-membered ring as the central feature. The identity and structure of this platinum complex has been established by NMR spectroscopy and by a single-crystal X-ray structure determination.