10284-49-8Relevant academic research and scientific papers
Suppression of unwanted heterogeneous platinum(0)-catalyzed reactions by poisoning with mercury(0) in systems involving competing homogeneous reactions of soluble organoplatinum compounds: Thermal decomposition of bis(triethylphosphine)-3,3,4,4-tetramethylplatinacyclopentane
Whitesides, George M.,Hackett, Marifaith,Brainard, Robert L.,Lavalleye, Jean-Paul P. M.,Sowinski, Alan F.,Izumi, Alan N.,Moore, Stephen S.,Brown, Duncan W.,Staudt, Erin M.
, p. 1819 - 1830 (2008/10/08)
Thermal decomposition of bis(trialkylphosphine)-3,3,4,4-tetramethylplatinacyclopentanes in hydrocarbon solvents yields two major products: 2,2,3,3-tetramethylbutane and 1-methyl-1-tert-butylcyclopropane. The former appears to be generated by heterogeneous process(es) catalyzed by platinum(0) (colloidal and/or solid) formed during the decomposition; the latter is the product of a homogeneous reaction sequence. The existence of competing heterogeneous and homogeneous reaction pathways complicates the study of this thermal decomposition. The addition of mercury(0) to the system selectively suppresses the heterogeneous reaction by poisoning the bulk platinum (0). This technique has been tested in one well-defined model system - the homogeneous hydrogenation of dineopentylbis(triethylphosphine)platinum(II) to dihydridobis(triethylphosphine)platinum(II) and neopentane in the presence of the heterogeneous platinum(0)-catalyzed hydrogenation of 1-methylcyclopentene to methylcyclopentane - and found to eliminate the heterogeneous reaction while leaving the homogeneous one essentially unaffected. Application of this technique to the thermal decomposition of 3,3,4,4-tetramethylplatinacyclopentane simplifies the reaction by eliminating 2,2,3,3-tetramethylbutane as a product. Similarly, addition of mercury(0) to solutions containing H2 and (1,5-cyclooctadiene)dimethylplatinum(II) in cyclohexane suppresses the autocatalytic, heterogeneous platinum-catalyzed conversion of the organoplatinum compound to (inter alia) cyclooctane, methane, and platinum (0). In other reactions examined - especially the high-temperature thermal decompositions of (1,5-cyclooctadiene)dineopentylplatinum(II) and of cis-bis(cyclopentyldimethylphosphine)dimethylplatinum(II) in hydrocarbon solvents - mercury poisoning does not successfully separate homogeneous and heterogeneous reactions. In the latter instance, an additional complicating process - apparent reaction of mercury(0) with the organoplatinum compound - introduces reaction paths which seem to generate methyl radicals. The paper includes a simple preparation of 1,4-dihalo-2,2,3,3-tetramethylbutane and illustrates the use of this material as a reagent for the preparation of 3,3,4,4-tetramethylmetallacyclopentanes via the corresponding di-Grignard reagents.
MULTINUCLEAR NMR SPECTROSCOPY OF (METALLA)NEOPENTYL DERIVATIVES OF TIN AND MERCURY
Mitchell, Terence N.,Fabisch, Bodo
, p. 249 - 254 (2007/10/02)
Proton, carbon-13, tin-119 and mercury-199 chemical shift and element-metal coupling constant data are presented for compounds of the types Sn(CH2MMe3)4, Hg(CH2MMe3)2, Me3SnCH2MMe3 and i-BuHgCH2MMe3 (M = C, Si, Ge, Sn).In almost all cases the NMR paramete
NUCLEOPHILIC SUBSTITUTION IN ORGANOMERCURY HALIDES BY A FREE RADICAL CHAIN PROCESS
Russel, Glen A.,Hershberger, James,Owens, Karen
, p. 43 - 56 (2007/10/02)
Primary and secondary alkylmercury halides react with the salts of secondary nitroalkanes to afford tertiary nitroalkanes, mercury metal, and halide ion.The reaction is light initiated and is strongly inhibited by radical scavengers.Cyclized products resu
Mechanism of Thermal Decomposition of Dineopentylbis(triethylphosphine)platinum(II): Formation of Bis(triethylphosphine)-3,3-dimethylplatinacyclobutane
Foley, Paul,DiCosimo, Robert,Whitesides, George M.
, p. 6713 - 6725 (2007/10/02)
The thermal decomposition of dineopentylbis(triethylphosphine)platinum(II) (1) in cyclohexane solution at 157 deg C yields bis(triethylphosphine)-3,3-dimethylplatinacyclobutane (4) by a reaction which involves dissociation of 1 equiv of triethylphosphine, intramolecular oxidative addition of the C-H bond of a neopentyl methyl group to platinum (3), and reductive elimination of neopentane.Carbon-carbon bond formation resulting in production of dineopentyl is a detectable side-reaction.The overal reaction has Arrenius activation parameters: Ea ca. 49 kcal mol-1, log A ca. 20.The activation energy for phosphine dissociation is 27 - 35 kcal mol-1.Transfer of a hydrogen atom from the triethylphosphine group to aneopentyl moiety occurs at a rate approximately 3percent that of transfer of hydrogen from the methyl of one neopentyl group to the methylene of the other.Any processes which abstract α-methylene hydrogens from the neopentyl group occur at less than 1percent the rate of processes which abstract hydrogens from the neopentyl methyl groups.Substitution of deuterium for hydrogen in either the neopentyl methyl groups or the triethylphosphine groups slows the decomposition reactions (kH/kD ca. 3.0).The mechanism proposed for generation of 4 is based in part on deuterium-labeling experiments: comparison of results by using different labeling patterns for 1 demonstrates the special utility of "inverted" experiments in which hydrogen transfer from a specific site is examined in a system which is otherwise perdeuterated.The driving force for the conversion of 1 to 4 is not obvious: it may be relief of steric strain in 1 , changes in electronic energy due to reorganization of ligands around platinum, or changes in entropy.
