- Catalytic conversion of isocyanates to carbodiimides by cyclopentadienyl manganese tricarbonyl and cyclopentadienyl iron dicarbonyl dimer
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Isocyanates are catalytically converted to the corresponding carbodiimides in the presence of low valent transition metal complexes. The best conversions and yields were accomplished using [(C5R5)Fe(CO)2]2 (R = H or Me) or MeCpMn(CO)3 as catalysts.
- Rahman, A.K. Fazlur,Nicholas, Kenneth M.
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- Preparation and characterization of the disjoint diradical 4,4′-bis(1,2,3,5-dithiadiazolyl) [S2N2C-CN2S2] and its iodine charge transfer salt [S2N2C-CN2S2][I]
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Condensation of oxamidrazone with sulfur dichloride in acetonitrile affords 4,4′-bis(1,2,3,5-dithiadiazolium) dichloride in moderate yield. Reduction of this salt with triphenylantimony yields the diradical 4,4′-bis(1,2,3,5-dithiadiazolyl) [S2N2C-CN2S2], which has been isolated and characterized in the solid state as its dimer [S2N2C-CN2S2]2. The diradical is disjoint, and ab initio molecular orbital methods confirm a very small energy gap (3 at 273 K) of a simple five-line pattern (aN = 0.50 mT, g = 2.011), i.e., there is no observable exchange coupling between the two centers. In the solid state, the dimer [S2N2C-CN2S2]2 forms a slipped stack structure, with a mean intradimer S-S distance of 3.078 ? and mean interdimer S- - -S contact of 3.761 ?. Cosublimation of the diradical with iodine produces the charge-transfer salt [S2N2C-CN2S2][I], orthorhombic space group Ccmm, a = 11.909(3) ?, b = 3.271(2) ?, c = 19.860(6) ?, Z = 4 (at 293 K). In this structure the heterocyclic rings form perfectly superimposed and evenly spaced stacks along the y direction, with channels of disordered iodines. The iodine-doped material is metallic at ambient temperatures, with a single-crystal conductivity of 460 S cm-1 at 300 K; variable temperature conductivity and magnetic measurements reveal a phase transition near 270 K, with the onset of semiconducting behavior. Transport data for the neutral and doped materials are discussed in the light of Extended Hückel band calculations.
- Bryan,Cordes,Goddard,Haddon,Hicks,MacKinnon,Mawhinney,Oakley,Palstra,Perel
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- Synthesis and degradation of nucleic acid components by formamide and iron sulfur minerals
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We describe the one-pot synthesis of a large panel of nucleic bases and related compounds from formamide in the presence of iron sulfur and iron-copper sulfur minerals as catalysts. The major products observed are purine, 1H-pyrimidinone, isocytosine, adenine, 2-aminopurine, carbodiimide, urea, and oxalic acid. Isocytosine and 2-aminopurine may recognize natural nucleobases by Watson-Crick and reverse Watson-Crick interactions, thus suggesting novel scenarios for the origin of primordial nucleic acids. Since the major problem in the origin of informational polymers is the instability of their precursors, we also investigate the effects of iron sulfur and iron-copper sulfur minerals on the stability of ribooligonucleotides in formamide and in water. All of the iron sulfur and iron-copper sulfur minerals stimulated degradation of RNA. The relevance of these findings with respect to the origin of informational polymers is discussed.
- Saladino, Raffaele,Neri, Veronica,Crestini, Claudia,Costanzo, Giovanna,Graciotti, Michele,Di Mauro, Ernesto
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- Reactivity of bis(2,2,5,5-tetramethyl-2,5-disila-1-azacyclopent-1-yl)tin with CO2, OCS, and CS2 and comparison to that of bis[bis(trimethylsilyl)amido]tin
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The heterocumulenes carbon dioxide (CO2), carbonyl sulfide (OCS), and carbon disulfide (CS2) were treated with bis(2,2,5,5-tetramethyl-2,5-disila-1-azacyclopent-1-yl)tin {[(CH 2)Me2Si]2N}2Sn, an analogue of the well-studied bis[bis(trimethylsilyl)amido]tin species [(Me3Si) 2N]2Sn, to yield an unexpectedly diverse product slate. Reaction of {[(CH2)Me2Si]2N}2Sn with CO2 resulted in the formation of 2,2,5,5-tetramethyl-2,5-disila-1- oxacyclopentane, along with Sn4(μ4-O){μ2- O2CN[SiMe2(CH2)2]} 4(μ2-N=C=O)2 as the primary organometallic Sn-containing product. The reaction of {[(CH2)Me2Si] 2N}2Sn with CS2 led to formal reduction of CS2 to [CS2]2-, yielding [{[(CH 2)Me2Si]2N}2Sn]2CS 2{[(CH2)Me2Si]2N}2Sn, in which the [CS2]2- is coordinated through C and S to two tin centers. The product [{[(CH2)Me2Si]2N} 2Sn]2CS2{[(CH2)Me 2Si]2N}2Sn also contains a novel 4-membered Sn-Sn-C-S ring, and exhibits a further bonding interaction through sulfur to a third Sn atom. Reaction of OCS with {[(CH2)Me2Si] 2N}2Sn resulted in an insoluble polymeric material. In a comparison reaction, [(Me3Si)2N]2Sn was treated with OCS to yield Sn4(μ4-O)(μ2- OSiMe3)5(n1-N=C=S). A combination of NMR and IR spectroscopy, mass spectrometry, and single crystal X-ray diffraction were used to characterize the products of each reaction. The oxygen atoms in the final products come from the facile cleavage of either CO2 or OCS, depending on the reacting carbon dichalogenide.
- Stewart, Constantine A.,Dickie, Diane A.,Parkes, Marie V.,Saria, Josephat A.,Kemp, Richard A.
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experimental part
p. 11133 - 11141
(2011/02/16)
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- TRIMETHYLSILYL CARBODIIMIDO FLUOROPHOSPHINES
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N,N'-Bis(trimethylsilylcarbodiimido)fluorophosphine, 3 was obtained in the reaction of N,N'-bis(trimethylsilyl)carbodiimide, 1 with dichlorofluorophosphine.Compound 3 is unstable, both thermally and in solution.Upon warming neat 3 to 50 deg C, 1 and other
- Gruber, Matthias,Schmutzler, Reinhard
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p. 113 - 116
(2007/10/02)
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- A New Mode of Formation of a Phosphorus-Phosphorus Bond. X-ray Crystal Structure of Tetramethyldiphosphane Monosulfide
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Tetraphenyldiphosphane monosulfide (7) was formed during an attempt to synthesize the diphenylphosphino-substituted thioureas 5 and 6 by the reaction of thiourea (1) or N,N'-bis-(trimethylsilyl)thiourea (2) with chlorodiphenylphosphane.The attempted distillation of the dimethylphosphino-substituted N,N'-dimethylthiourea 9 furnished tetramethyldiphosphane monosulfide (10).These reactions provide a new mode of formation of phosphorus-phosphorus bonds. - According to an X-ray analysis, 10 crystallizes in the space group P21/n.The molecule adopts a trans configuration, with the S atom antiperiplanar to the lone pair.
- Gruber, Matthias,Jones, Peter G.,Schmutzler, Reinhard
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p. 1313 - 1317
(2007/10/02)
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- Borylated Carbodiimides
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The borylated carbodiimides 3a, 3b and 4 can be synthesized by reaction of the 2-chloro-1,3,2-diazaborolidines 2a, 2b with Me3Si-N=C=N-SiMe3 (1) or Me3Si-N=C=N-tBu respectively.In the reaction of the non cyclic haloboranes R2BHal (R = Ph, Me, M
- Einholz, Wolfgang,Haubold, Wolfgang
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p. 1367 - 1372
(2007/10/02)
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