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Crystal and molecular structures of some transition metal phosphine complexes, and their relevance to homogeneous catalysis.

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posted on 2015-11-19, 08:45 authored by Ursula Anne. Gregory
Homogeneous catalysis of organic reactions by transition metal complexes, is thought to involve some or all of the following: 1) Formation of M-H bonds 2) Formation of M-C sigma bonds (M-C-) 3) Formation of M-C "olefinic" bonds (M-? ) 4 ) C (0- ) - C () equilibria, and hydrogen transfers 5) Coordination of small molecules. Structural information relevant to these processes has been obtained by study of the crystal structures of some appropriate model compounds. In the system RuH(C10H7) (Me2P.C2H4.PMe2)2 is octahedrally coordinated, with cis hydride and (o-C10H7). Ru-C is 2.16 and Ru-P (average) 2.30; the phosphine ligands are disordered. The Ru-H observed distance of 1.7 agrees with other reported Ru-H bond lengths. The isostructural reported Ru-H bond lengths. The isostructural OsH(C10H7) (Me2P.C2H4.PMe2)2 has Os-C 2.13. The structure analysis of Ru(Me2.PC2H4.PMe2)2 was unsuccessful. The structure of a dihydride complex, FeH2(Ph2P.C2H2.PPh2)2, could not be solved. A spectral reinvestigation of the solvated complex OsHCl(Ph2P.CH2.PPh2)2.C6H6, has shown that the reported interaction between the hydridic hydrogen and the benzene molecule, does not occur. The structure of [IrH (COOMe) (Me2P.C2H4.PMe2)2] BPh4, formed by addition of MeOH across IrCO(Me2P.C2H4.PMe2)2+, shows the cation to have a trans octahedral configuration with Ir-C 2.10, Ir-P (average) 2.31. Ir-H was not measured. The structures, at -70 °C, of the isomorphous NiHCl(PPr3i)2 and PdHCl(PPr3i)2, are trans-planar, and exhibit the typical distortions found in transition metal complex hydrides. Ni-P is 2.19A; Ni-Cl 2.21A; Pd-P 2.30A; Pd-Cl 2.39A. These results are discussed in terms of cis and trans effects. The observed Ni-H distance, 1.4A, is short compared to reported M-H bonds. The structures of [MoCl2(Ph2P.C2H4.PPh2)2] and [MoOC1(Ph2P.C2H4.PPh2)2] [ZnC13.acetone] were studied at -70 °C. MoCl2(Ph2P.C2H4.PPh2)2 is the product of N2 loss from the dinitrogenyl complex Mo(N2)Cl2(Ph2P.C2H4.PPh2)2, while [MoOC1(Ph2P.C2H4.PPh2)2] [ZnC13.acetone] is an intermediate in the formation of Mo(N2)C12(Ph2P.C2H4.PPh2)2. The cation is trans octahedrally coordinated, with Mo=0 1.69, Mo.-Cl 2.46A, Mo-P (average) 2.57. The tetrahedral anion has Zn-Cl (average) 2.23A, Zn-O 2.12A. The complex is solvated with one molecule of acetone.


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University of Leicester

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  • Doctoral

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  • PhD



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