Download Free Molybdenum Iv Imido Silylamido And Hydride Complexes Book in PDF and EPUB Free Download. You can read online Molybdenum Iv Imido Silylamido And Hydride Complexes and write the review.

This thesis describes studies on the synthesis and reactivity of a variety ofmolybdenum thiolate hydride complexes; tungsten complexes were also prepared forcomparison. The original purpose of this research was to examine the behaviour of sulphurligatedmolybdenum complexes as models for the molybdenum site in nitrogenase, but thiswork has demonstrated that the 5-coordinated complexes [MoH(SC6H2R3-2,4,6)3(PR1Ph2)] (R= Me or Pr'; R1 = Me or Et) are very reactive versatile starting materials for thepreparation of a wide range of derivatives, some of which model aspects of the chemistry ofother molybdenum enzymes such as xanthine oxidase.It is known that the reaction of thiols HSC6H2R3-2,4,6 with [MoH4(PR'Ph2)4] or trans-[Mo(N2)2(PMePh2)4] produces unsaturated thiolato-hydride complexes of molybdenum(IV)[MoH(tipt)3(PMePh2)] (A) (tipt = SC6H2PrV-2,4,6). Here we report an extension of thesestudies in which we have prepared the oxygen-sensitive, five- and six-coordinated complexes[MoH(SC6H4F)3(PMePh2)] (2.3) and [MoH(SC6HF4-2,3,5,6)3(PMePh2)2] (2.1) and[MoH(SC6F5)3(PMePh2)2] (2.4).Some reactions of (2.3), (2.1) and (2.4) have been investigated, including the reactionof (2.4) with carbon monoxide which yields [Mo(SC6F5)2(CO)2(PMePh2)2] (6.7). Thereaction of (2.1) with pyridine gives [MoH(SC6HF4-2,3,5,6)3(C5H5N)(PMePh2)] (6.1).The reaction of the electron-deficient hydride thiolate complex [MoH(tipt)3(PMe2Ph)2](B) with phenylacetylene gives the novel square pyramidal, diamagnetic phosphoniumalkylidenecomplex[MoO{=C(Ph)CH=C(Ph)CH2PMe2Ph)(SC6H2Pri3-2,4,6)3](3E), whereasthe reaction of /Molylacetylene with (A) yields the novel phosphonium ylide complex[MoO(SC6H2Pri3)2(HC=CC6H4Me-4){(C6H4Me-4) (C=CHPMePh2)}](3D),thathas relevanceto the species derived from xanthine oxidase when it is inhibited by aldehydes. These twocomplexes have been characterised by X-ray structure determination. [WH(tipt)3(PMe2Ph)2j(C) with phenylacetylene and p-tolylacetylene gives products resulting from oligomerisationreactions.In the reaction o f [MoH(tipt)3(PMePh2)] (A) with hydrazines, both binding of hydrazineto Mo and disproportionation/reduction have been observed. The bright green andtemperature- and oxygen-sensitive complex [MoH(tipt)3(NH3)(PMePh2)J (4.1) has beenobtained from the reaction of NH2NH2 with (A). Its X-ray structure determination at -10°Cshows that it is a hydride ammonia complex with trigonal bipyramidal geometry. Thereaction of phenylhydrazine with (A) gives dark green single crystals that have been thesubject of an X-ray crystallographic analysis. This compound crystallised in a much-distortedtrigonal bipyramidal geometry and is formulated as [MoH(tipt)3(NH2NHPh)(PMePh2)] (4.4).Isocyanides are substrates or inhibitors of nitrogenase. The interaction of isocyanides withthe five- and six-coordinate hydride complexes has been investigated. The reaction of[MoH(tipt)3(PMePh2)] (A) with MeNC and t-BuNC and also the reaction of[WH(tipt)3(PMe2Ph)2] (C) with MeNC, produce [MoH(tipt)2(MeNC)4] (5.1), [MoH(tipt)2('-BuNC)4] (5.3) and [WH(tipt)2(MeNC)4] (5.2) respectively. The structures of these complexeshave been confirmed by X-ray structure determination.The reaction of molybdenum hydride complexes with carboxylic acids give productswhich show carboxylate groups in their IR and NMR spectra.
Hardbound. Molybdenum is an element with an extremely rich and interesting chemistry having very versatile applications in various fields of human activity. It is used extensively in metallurgical applications. Because of their anti-wear properties, molybdenum compounds find wide applications as lubricants - particularly in extreme or hostile environmental situations. Many molybdates and heteropolymolybdates are white and therefore used as pigments. In addition, they are non-toxic and act as efficient corrosion inhibitors and smoke suppressants. Hydroprocessing of petroleum is one of the largest industries employing heterogeneous catalysts. Molybdenum catalysts have shown great promise in the liquefaction of coal and this may develop into one of its most important catalytic uses. The use of molybdenum compounds in homogeneous catalysis is also significant.Three important classes of molybdenum compounds in the solid state are reviewed, viz., oxides, sul
Chapter 1. A general introduction is given. Chapter 2. The biscarboxylate species, Mo(NR)(CHCMe 2Ph)(O 2CPh3)2 (R = 2,6-i-Pr2C6H3, 2,6- Me2C6H3, 2-t-BuC 6H4, or 1 -adamantyl) are compared to newly synthesized bis(terphenylcarboxylate) species, Mo(NR)(CHCMe 2Ph)(O 2CTer)2 (Ter = 2,6-diphenyl-4- methylphenyl or 2,6-diphenyl-4-methoxyphenyl). Preparation of bis(terphenylcarboxylate) species was accomplished through protonolysis of Mo(NR)(CHCMe2R')(Me2Pyr)2 with two equivalents of TerCO2H and one of them was characterized through X-ray crystallography. Photolysis experiments of many of the biscarboxylate complexes led to rate constants for the converstion of anti to syn species, which are much slower than bisalkoxide species. Trimethylphosphine adducts of selected triphenylacetate complexes have been isolated and studied in solution. Protonolysis of Mo(NAr)(CHCMe 2R')(Me 2Pyr)2 (Ar = 2,6-i-Pr 2C6H3) with one equivalent of TerCO2H led to the isolation of a handful of monocarboxylate species, Mo(NAr)(CHCMe 2Ph)(O 2CAr')(Me2Pyr). An X-ray structure of one of them was also characterized. Several of the bis(triphenylacetate) complexes and all of the monocarboxylates are active initiators for the regioselective polymerization of diethyl dipropargylmalonate (DEPDM). In the case of the latter compounds, activity towards olefins is also observed and briefly mentioned.
(Cont.) Chapter 4. Reactivity of Molybdenum Imido Alkylidene Bis(pyrrolyl) Complexes. The Lewis amphoteric nature of the bis(pyrrolyl) complexes reported in chapter 3 is examined by demonstrating that these complexes react with both trimethylphosphine (at the molybdenum center) and B(C6Fs)3 (at a q5 pyrrolyl nitrogen). A structure of a trimethylphosphine adduct is reported. The bis(pyrrolyl) complexes are found to serve as excellent precursors for the in situ generation of olefin metathesis catalysts at room temperature and millimolar concentration. Furthermore, catalysts not accessible via traditional routes may now be accessed from bis(pyrrolyl) precursors. The bis(pyrrolyl) complexes also react with simple olefins such as ethylene and isobutylene to yield what are proposed to be a bimetallic dimer [Mo(NAr)(NC4H4)2]2 and a 2-propylidene complex via olefin metathesis. The impact of in situ synthesis on syn and anti isomer ratios is discussed as is reactivity with protic reagents other than alcohols.