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61.
T. Chivers S. W. Liblong J. F. Richardson 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract The reactions of (Me3SiNR)PPh2 (NSiMe3) (R=H, SiMe3) with (NSCl)3 or SxCl2 (x=1, 2) provide improved preparative routes to mixed phosphazene-thia-zene ring systems, e.g. (Ph2PN) (SN)2, 1,3- and 1,5-(Ph2PN)2(SN)2. The interaction of these heterocycles with protonic and Lewis acids, e.g. HBF4, BCl3, MeSO3CF3, has been investigated in order to determine the site of attack and the effect of adduct formation on the molecular and electronic structures of these ring systems. These reactions have been monitored by UV-visible and 31P NMR spectroscopies and the structures of crystalline adducts have been determined by X-ray crystallography. For example, the interaction of 1,3-(Ph2PN)2(SN)2 with MeSO3CF3 gives a product in which the methyl group is attached to a nitrogen atom between phosphorus and sulfur. The resulting structural distortion in this and related adducts will be analyzed in the context of the electronic structures of mixed phosphazene-thiazene systems and their adducts with Lewis acids. 相似文献
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64.
R. A. Chivers P. J. Barham J. Martinez-Salazar A. Keller 《Journal of Polymer Science.Polymer Physics》1982,20(9):1717-1732
This article is part of the general project laid out in Part I (ref. 9) and is concerned with obtaining information on primary (unthickened) crystals of polyethylene formed at low supercoolings. For this, a technique had to be devised by which crystallization could be speeded up so as to eliminate or at least reduce lamellar thickening. Indeed we were able to increase the rate of crystallization by an order of magnitude using a technique which we have called enhanced self-nucleation. Using this technique we find that when viewed under an optical microscope, spherulites crystallize uniformly over the field of view, and not, as is usual, by a radial growth process. Isothermal crystallization in bulk linear polyethylene has been studied by means of the enhanced self-nucleation technique as a function of crystallization time by using Raman LAM and melting points to assess variations of fold length Data have been obtained at very much shorter times than before. At short times, we find a constant fold length; at longer times the crystals thicken linearly with the logarithm of time. Values of the initial fold length for crystallization temperatures between 118 and 130°C are presented. Associated with the thickening at short times we find an induction time which increases with temperature. 相似文献
65.
Two synthetic routes to compounds of the type π-Cp2TiIIIR (R=CH3, CH2Si(CH3)3, C6F5) have been investigated: (a) chemical reduction of π-Cp2TiIV(R)Cl by zinc or aluminum metal in tetrahydrofuran, and (b) conventional organometallic syntheses using organo-lithium or -magnesium reagents and [π-Cp2TiIIICl]2. The preferred route is via an organolithium reagent, since chemical reduction gives a mixture of products. Green, monomeric complexes (R = CH2Si(CH3)3, C6F5) were isolated and characterised. From the reaction of π-Cp2TiIVCl2 and trimethylsilylmethyllithium in a 1/1 ratio, π-CpTiIV [CH2Si(CH3)3]3 was obtained. Unlike π-Cp2TiIIIC6F5, π-Cp2TiIIICH2Si(CH3)3 does not form a blue complex with molecular nitrogen. 相似文献
66.
Tiina Maaninen Heikki M. Tuononen Katja Kosunen Raija Oilunkaniemi Johanna Hiitola Risto Laitinen Tristram Chivers 《无机化学与普通化学杂志》2004,630(12):1947-1954
Supermesityl selenium diimide [Se{N(C6H2tBu3‐2, 4, 6)}2; Se{N(mes*)}2] can be prepared in a good yield from the reaction of SeCl4 and (mes*)NHLi. The molecule adopts an unprecedented anti, anti‐conformation, as deduced by DFT calculations at PBE0/TZVP level of theory and supported by 77Se NMR spectroscopy and a crystal structure determination. An analogous reaction involving (C6H2Me3‐2, 4, 6)NHLi [(mes)NHLi] unexpectedly lead to the reduction of selenium and afforded the selenium diamide Se{NH(mes)}2 that was characterized by X‐ray crystallography and 77Se NMR spectroscopy. The Se‐N bonds of 1.847(3) and 1.852(3) Å show normal single bond lengths. The <NSeN bond angle of 109.9(1)° also indicates a tetrahedral AX2E2 bonding arrangement around selenium. Two N‐H···N hydrogen bonds link the Se{NH(mes)}2 molecule with two discrete (mes)NH2 molecules. In the solid state selenium diamide adopts the anti‐conformation, whereas in solution the presence of both syn‐ and anti‐isomers could be observed. PBE0/TZVP calculations of the shielding tensors of 28 different types of selenium‐containing molecules, for which the 77Se chemical shifts are unambiguously known, were carried out to assist the spectral assignment of Se{N(mes*)}2 and Se{NH(mes)}2. 相似文献
67.
The reaction of Ph2P(S)N(SiMe3)2 with potassium tert-butoxide in a 1:1 molar ratio produces K[Ph2P(S)NSiMe3], which was converted to the AsPh4+ salt by metathesis with [AsPh4]Cl. The X-ray crystal structure of [AsPh4][Ph2P(S)NSiMe3] · 0.5 THF consists of noninteracting AsPh4+ and Ph2P(S)NSiMe3? ions with d(P? S) = 1.980(4) Å and d(P? N) = 1.555(8) Å. The PNSi bite angle in the anion is 136.3(5)°. Electrophilic attack by Ph2P(S)Cl occurs at the sulfur atom of Ph2P(S)NSiMe3?. The oxidation of the anion with iodine produces a disulfide which regenerates K[Ph2P(S)NSiMe2] upon treatment with potassium tert-butoxide. 相似文献
68.
Armstrong A Chivers T Krahn M Parvez M Schatte G 《Chemical communications (Cambridge, England)》2002,(20):2332-2333
The treatment of Me3SiN=P(NHBut)3 with three equivalents of LiBun in toluene produces (Li3(P(NBut)3(NSiMe3)))2 comprised of a Li6N6 cyclic ladder capped on the two hexagonal faces by mu 3-PNSiMe3 groups; the corresponding reaction of O=P(NHBut)3 yields the face-sharing double-cubane (Li2(THF)P(O)(NBut)2(NHBut))2 with a central Li2O2 ring. 相似文献
69.
The reaction of (t)BuNHLi with TeCl(4) in toluene at -78 degrees C produces (t)BuNTe(&mgr;-N(t)Bu)(2)TeN(t)Bu (1) (55%) or [((t)BuNH)Te(&mgr;-N(t)Bu)(2)TeN(t)Bu]Cl (2) (65%) for 4:1 or 7:2 molar ratios, respectively. The complex {Te(2)(N(t)Bu)(4)[LiTe(N(t)Bu)(2)(NH(t)Bu)]LiCl}(2) (5) is obtained as a minor product (23%) from the 4:1 reaction. It is a centrosymmetric dimer in which each half consists of the tellurium diimide dimer 1 bonded through an exocyclic nitrogen atom to a molecule of LiTe(N(t)Bu)(2)(NH(t)Bu) which, in turn, is linked to a LiCl molecule. Crystals of 5 are monoclinic, of space group C2/c, with a = 27.680(6) ?, b = 23.662(3) ?, c = 12.989(2) ?, beta = 96.32(2) degrees, V = 8455(2) ?(3), and Z = 4. The final R and R(w) values were 0.046 and 0.047. At 65 degrees C in toluene solution, 5 dissociates into 1, LiCl, and {[LiTe(N(t)Bu)(2)(NH(t)Bu)](2)LiCl}(2) (4), which may also be prepared by treatment of [Li(2)Te(N(t)Bu)(3)](2) (6) with 2 equiv of HCl gas. The centrosymmetric structure of 6 consists of a distorted hexagonal prism involving two pyramidal Te(N(t)Bu)(3)(2)(-) anions linked by four Li atoms to give a Te(2)N(6)Li(4) cluster. Crystals of 6 are monoclinic, of space group P2(1)/c, with a = 10.194(2) ?, b = 17.135(3) ?, c = 10.482(2) ?, beta = 109.21(1) degrees, V = 1729.0(5) ?(3), and Z = 2. The final R and R(w) values were 0.026 and 0.023. VT (1)H and (7)Li NMR studies reveal that, unlike 1, compounds 2, 4, and 6 are fluxional molecules. Possible mechanisms for these fluxional processes are discussed. 相似文献
70.
The geometries and energetics of different conformations of sulfur and selenium diimides E(NR)(2) (E = S, Se; R = H, Me, (t)Bu, C(6)H(3)Me(2)-2,6, SiMe(3)) have been studied by using various ab initio and DFT molecular orbital techniques. The syn,syn conformation is found to be most stable for parent E(NH)(2), but in general, the preferred molecular conformation for substituted chalcogen diimides is syn,anti. In the case of E(NH)(2) the present calculations further confirm that syn,syn and syn,anti conformations lie energetically close to each other. From the three different theoretical methods used, B3PW91/6-31G proved to be the most suitable method for predicting the geometries of chalcogen diimides. The optimized geometrical parameters are in a good agreement with all available experimental data. While qualitative energy ordering of the different conformations is independent of the level of theory, the quantitative energy differences are dependent on the method used. The performance and reliability of higher level ab initio calculations and DFT methods using large basis sets were tested and compared with experimental information where available. All of the higher level ab inito methods give very similar results, but the use of large basis sets with the B3PW91 method does not increase the reliability of the results. The combination of CCSD(T)/cc-pVDZ with the B3PW91/6-31G-optimized geometries is found to be the method of choice to study energetic properties of chalcogen diimides. 相似文献