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1.
1H, 13C and 29Si NMR data for the compounds (CH 3) xSi(CH 2CHCH 2) 4-x are reported. The 1H resonances from the π system are indicative of the electron-supplying inductive effect (+I) of the (CH 3SiCH 2, moiety but the corresponding 13C π chemical shifts seem to be influenced by a sterically induced polarization of the C-H bonds. The 13C All, 13C Me and 29Si chemical shift data reveal an important neighbour anisotropy contribution originating from the π system. Ultraviolet study of the compounds mentioned above gives indication of a σ—π conjugation in accordance with PES and ab initio results [1—5]. The trend observed in the various coupling constants is too small to be Interpreted. 相似文献
2.
The photolysis of alkyl metallocene derivatives of vanadium and niobium in hydrocarbon solvents results in cleavage of the carbon—metal σ-bond. In the cases of (η 5-C 5H 5) 2VCH 3 and (η 5-C 5H 5) 2Nb(CH 3) 2, only methane (>99%) is produced photochemically. (η 5-C 5H 5) 2V(CH 3) 2, prepared on a convenient new synthesis from (η 5-C 5H 5) 2VCl 2 and methyllithium in toluene, degrades under photochemical conditions to yield both methane and ethane in a 2 : 1 ratio. The ethane arises from intra- and intermolecular methyl dimerization. Deuterium labeling studies have shown that the methyl group, the cyclopentadienyl ring, and the solvent are all sources of hydrogen in the formation of methane in these photolyses. The extent to which each source participates in the hydrogen abstraction process cannot be quantitatively determined because of the influence of an isotope effect. Chemical reactions with carbon monoxide during the photolyses give low yields of (η 5-C 5H 5)V(CO) 4 from (η 5-C 5H 5) 2VCH 3 or (η 5-C 5H 5) 2V(CH 3) 2, and of (η 5-C 5H 5) 2Nb(CO)CH 3 from (η 5-C 5H 5) 2Nb(CH 3) 2. 相似文献
3.
A CNDO-2 study of 29Si NMR chemical shifts for compounds of the type (CH 3) nSiX 4-n (X = H, F, Cl) is reported. The paramagnetic screening constants σ p are given. The general variation in σ p with n agrees fairly well with the variation of the observed chemical shifts for X = H and F, but the correlation is not so good for X = Cl. 相似文献
4.
The crystal and molecular structure of the complex Th[η 5-(CH 3) 5C 5] 2[CH 2-Si(CH 3) 3] 2, which undergoes facile intramolecular cyclometalation to the thoracyclobutane Th[η 5-(CH 3) 5C 5] 2(CH 2) 2Si(CH 3) 2, is reported. While the Th[η 5-(CH 3) 5C 5] 2 ligation is unexceptional, the Th[CH 2Si(CH 3) 3] 2 fragment is highly unsymmetrical having Th-C (corresponding angle Th-C-Si) 2.51(1) Å (132.0(6)°) and 2.46(1) Å (148.0(7)°). This conformation, which appears to result from severe intramolecular non-bonded contacts, allows a methyl hydrogen atom of one CH 2Si(CH 3) 3 ligand to approach within ca. 2.3 Å of the α-carbon atom of the other CH 2Si(CH 3) 3 ligand. 相似文献
5.
Various preparative routes for the synthesis of (CH 3) 3SiP(CF 3) 2 are discussed. The most favourable method, reaction of (CH 3) 3MPH 2 with HE(CF 3) 2, provides a good yield of (CH 3) 3ME(CF 3) 2 compounds (M = Si, Ge, Sn; E = P, As). The reaction rate is dependent on M (Si < Ge <Sn) und E (P < As). The stability and reactivity of the (CH 3) 3ME(CF 3) 2 compounds are discussed. The new compounds were characterized by NMR and IR spectra and by cleavage reactions of the M-E bond. 1H, 19F NMR and IR spectral data are reported. 相似文献
6.
An ab initio calculation has been carried for the carbene tetrel bonded complexes CH3Y???CH2 (Y = F, CN, NC, and NO2), CH3F???CZ2 (Z = Cl and CH3), XH3F???CF2 (X = C, Si, Ge, and Sn), SiF4???CF2, and XH3F???NHC (N-heterocyclic carbene), where carbene is treated as a Lewis base and XH3Y is a Lewis acid. Formation of the tetrel bond is mainly attributed to charge transfer from the lone pair on the C atom in the carbene toward the σ* X–Y orbital and also the σ* X–H one in the strong tetrel bond. The carbene tetrel bond is strengthened/weakened by the electron-withdrawing group in the tetrel donor/acceptor and enhanced by the methyl group in C(CH3)2. NHC forms a stronger carbene tetrel bond in XH3F???NHC (X = Si, Ge, and Sn) where it exceeds that of the majority of H-bonds. Interestingly, the tetrel bond becomes stronger in the order of X = C < Ge < Sn < Si in XH3F???NHC and the largest interaction energy occurs in SiH3F???NHC, amounting to ?103 kJ/mol. The carbene tetrel bond can be strengthened by cooperative effect with the N???M interaction in trimers H2C???CH3CN???M (M = CH3CN, HCN, ICN, SbH2F, LiCN, and BeH2) and has doubled in H2C???CH3CN???BeH2. 相似文献
7.
By measuring the relative CO quantum yields from ketene photolysis as a function of photolysis wavelength we have determined the threshold energy at 25° for CH 2CO( 1A 1) → CH 2( 3B 1) + CO( 1Σ +) to be 75.7 ± 1.0 kcal/mole. This corresponds to a value of 90.7 ± 1.0 kcal/mole for Δ Hf2980[CH 2( 3B 1)]. By measuring the relative ratio of CH 2( 1A 1)/CH 2( 3B 1) from ketene photolysis as a function of photolysis wavelength we have determined the threshold energy at 25°C for CH 2CO( 1A 1) → CH 2( 1A 1) + CO( 1Σ +) to be 84.0 ± 0.6 kcal/mole. This corresponds to a value of 99.0 ± 0.6 kcal/mole for Δ Hf2980[CH 2( 1A 1)]. Thus a value for the CH 2( 3B 1) ? CH 2( 1A 1) energy splitting of 8.3 ± 1 kcal/mole is determined, which agrees with three other recent independent experimental estimates and the most recent quantum theoretical calculations. 相似文献
8.
A straightforward method for the preparation of metallo carbosiloxanes of type Si(OCH 2CH 2CH 2SiMe 2[OCH 2PPh 2M(CO) n]) 4 ( n = 3, M = Ni, 7a; n = 4, M = Fe, 7b; n = 5: M = Mo, 7c; M = W, 7d), Si(OCH 2CH 2CH 2SiMe[OCH 2PPh 2Ni(CO) 3] 2) 4 ( 8) and Me 2Si(OCH 2CH 2CH 2SiMe[OCH 2PPh 2Ni(CO) 3] 2) 2 ( 11) is described. The reaction of Si(OCH 2CH 2CH 2SiMeXCl) 4 ( 1: X = Me, 2: X = Cl) or Me 2Si(OCH 2CH 2CH 2SiMeCl 2) 2 ( 9) with HOCH 2PPh 2 ( 3) produces Si(OCH 2CH 2CH 2SiMe 2(OCH 2PPh 2)) 4 ( 4), Si(OCH 2CH 2CH 2SiMe(OCH 2PPh 2) 2) 4 ( 5) or Me 2Si(OCH 2CH 2CH 2SiMe(OCH 2PPh 2) 2) 2 ( 10) in presence of DABCO. Treatment of the latter molecules with Ni(CO) 4 ( 6a), Fe 2(CO) 9 ( 6b), M(CO) 5(Thf) ( 6c: M = Mo; 6d: M = W), respectively, gives the title compounds 7a- 7d, 8 and 11 in which the PPh 2 groups are datively bound to a 16-valence-electron metal carbonyl fragment.The formation of analytical pure and uniform branched and dendritic metallo carbosiloxanes is based on elemental analysis, and IR, 1H, 13C{ 1H}, 29Si{ 1H} and 31P{ 1H} NMR spectroscopic studies. In addition, ESI-TOF mass spectrometric studies were carried out. 相似文献
9.
From the reaction of 1,8-bis(bromomethyl)naphthalene with diphenyl(trimethylsilyl)phosphine a cyclic phosphonium salt IX is formed which can be rearranged with (CH 3) 3PCH 2 to yield the cyclic ylide X. Its metallation with t-butyllithium gives 2,2-diphenyl-2λ 5-phospha-phenalenyl-lithium XI. The anion of XI cannot be seen as a delocalized phospha-phenalenyl π-system but rather as a phosphonium-bis-ylide similar to the diphenylphosphonium-bis-benzylide.From 1,2-bis(chloromethyl)benzene and (C 6H 5) 2PSi(CH 3) 3 or from 1,2-bis(chloromagnesiummethyl)benzene and CH 3PCl 2, followed by quaternization using CH 3Br, cyclic phosphonium salts (XII and XV, respectively) can also be obtained, which may again be rearranged to form the ylides XIII or XVI. XVI gives with (CH 3) 3CLi 2,2-dimethyl-2λ 5-phospha-indenyl-lithium XVII, containing a dimethyl-phosphonium-bis-ylide anion (“isophosphindolyl-lithium”). 相似文献
10.
UV irradiation of η 5-C 5H 5Nb(CO) 4 in the presence of the phosphine ligands L (L = 2 PEt 3, Ph 2P(CH 2) 2PPh 2 (p 2( n), n = 1–5), cis-Ph 2PCH=CHPPh 2 (c-dpe)), and the mixed arsine-phosphine ligands Ph 2AsCH 2CH 2PPh 2 (arphos) and o-C 6H 4(AsPh 2)(PPh 2) (pab) yields the well defined complexes cis-[η 5-C 5H 5Nb(CO) 2L]. The monosubstituted species η 5-C 5H 5Nb(CO) 3L have been characterized spectroscopically. P 2Ph 4 forms mono- and dinuclear, mono- and biligate carbonylniobium complexes.Shielding of the 93Nb nucleus increases in the sequences (i) Ph 2As- < Ph 2P-, (ii) chelate 4-ring < chelate 5-ring and (iii) η 5-C 5H 5Nb(CO) 2L < η 5-C 5H 5Nb(CO) 3L < η 5-C 5H 5Nb(CO) 4, and 31P coordination shifts decrease in the order c-dpe > pab > arphos > p 2(2) > p 2(5) > p 2(4) ~ PEt 3 > p 2(3) > p 2(1). The trends generally parallel those for the corresponding NMR parameters of the vanadium complexes. Paramagnetic contributions to the overall shielding are smaller for the 93Nb than for the 51V nucleus, and this is explained in terms of increased covalency and decreased π-interaction in the niobium complexes. 相似文献
11.
New stable heteroleptic germanium(II) and tin(II) compounds [(SiMe 3) 2N-E 14-OCH 2CH 2NMe 2] n (E 14 = Ge, n = 1 ( 1), Sn, n = 2 ( 2)) have been synthesized and their crystal structures have been determined by X-ray diffraction analysis. While compound 1 is monomer stabilized by intramolecular Ge ← N coordination, compound 2 is associated to dimer via intermolecular dative Sn ← O interactions. 相似文献
12.
The products of the reaction of Me 3SiCl with PhTeMgBr in THF have been identified with the aid of high resolution 29Si and 129Te NMR spectroscopy. In addition to the expected product Me 2SiTePh (40%), the symmetrical telluride (Me 3Si) 2Te (10%) and the ether Me 3SiO(CH 2) 4TePh (45%) are also formed. The latter results from ring-opening of the solvent THF by Me 3SiCl followed by reaction of the product with PhTeMgBr. 相似文献
13.
The reduction of MoCl 4(DPPE) (DPPE = PPh 2CH 2CH 2PPh 2) with Mg or Na/Hg in the presence of 2 PPhR 2 under Ar results in the formation of the new complexes Mo(η 6-PhPR 2)(PPhR 2)(DPPE) when R is Ph (Ia) or Et(II). No η 6-PhPR 2 complex is obtained when R is Me because this small ligand forms strong MoP σ-bonds; nor is one obtained for R = Cy because of too much steric crowding. The limits for η 6-complexation can be quantified in terms of cone angle sums.Complex Ia is very similar to Mo(η 6-PhPMePh)(PMePh 2) 3 (IIIa) in that both react at similar rates with a variety of small ligands L = PMePh 2, PMe 2Ph, PMe 3, P(OMe) 3, N 2, CO, CNBu t and H 2 via dissociation of a labile σ-bonded ligand. Several other less crowded η 6-arylphosphinemolybdenum complexes including II do not have labile ligands at 25°C. The new complexes Mo(η 6-PhPPh 2)(L)(DPPE) have been characterized by 31P and 1H NMR, IR and gas uptake measurements, Ia has a higher affinity for H 2 than IIIa possibly because Mo(η 6-PhPPh 2)(H) 2(DPPE) adopts a non-fluxional trans-configuration. The 31P chemical shift of the σ-bonded ligand in 8 derivatives of Ia and 12 of IIIa correlate with the sum of the cone angles of the three σ-bonded ligands in each complex. 相似文献
14.
Product and kinetic studies on the reactions of hydrogen chloride in methanol solution with the substrates (CH 3) 3SnM(CH 3) 3 (M = Sn; Ge and Si) show that both SnM and SnCH 3 cleavage reactions occur, at similar rates, and are followed by other reactions giving complex but explicable mixtures of products. Similar behaviour is observed for trifluoroacetolysis in carbon tetrachloride solution, and some intermediates are observable. Trifluoroacetolysis of (CH 3) 3SnC(CH 3) 3 results in exclusive SnCH 3 cleavage. The very slow apparent solvolysis in acetic acid solution is thought to involve reaction with dissolved oxygen. 相似文献
15.
Five new hetero-organotellurium (IV) dithiocarbamates O[Si(CH 3) 2CH 2] 2TeIS 2CN(CH 2CH 2) 2 ( 1), O[Si(CH 3) 2CH 2] 2TeIS 2CN(CH 2CH) 2 ( 2), O[Si(CH 3) 2CH 2] 2TeIS 2CN(CH 2CH 2) 2O ( 3), O[Si(CH 3) 2CH 2] 2-TeIS 2CN(CH 2CH 2) 2S ( 4) and O[Si(CH 3) 2CH 2] 2TeIS 2CN(CH 2CH 2) 2CH 2 ( 5) were prepared from the 2,2,6,6-tetramethyl-1-oxa-4,4-diiodo-4-tellura-2,6-disilacyclohexane and the corresponding dithiocarbamate (dtc) sodium salts in ethanol. The compounds were characterized by means of Elemental Analyses, FAB MS, IR, 1H, 13C, 125Te NMR spectroscopy. The crystal structures of 1, 3 and 4 were determined. Dithiocarbamate ligands display an anisobidentate chelating coordination mode on interacting with the tellurium center in all compounds. The Te(IV) immediate environment can be described as that of a sawhorse structure in which the lone pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. The two methylene groups occupy the other equatorial positions with a sulfur atom of the dithiocarbamate group and the iodine atom occupying the axial positions. The solid state structures of 3 and 4 exhibit important intermolecular interaction Te?S(2B). This interaction results in the formation of a dimer, which is better described as a distorted octahedron with an apparently inactive lone pair. 相似文献
16.
The stereochemistry of several 2-R-1,3,6,2-trioxaphosphocanes (R = Cl, OCH 3, CH 3, N(CH 3) 3 has been investigated by 1H, 13C and 31P n m r spectroscopy. 相似文献
17.
The synthesis and 119Sn NMR characteristics of new five-coordinate tris(trichlorostannato) complexes of Rh I, Ir I and Pt II are reported. The Rh I and Ir I complexes are complex dianions of the form (PPN) 2[M(SnCl 3) 3L 2] where L can be CO, CN (cyclohexyl) or L 2, a diolefin such as 1,5-COD or NBD (norbornadiene). The anionic platinum complexes (PPN)[Pt(SnCl 3) 3L 2] contain similar L ligands. A number of neutral monotrichlorostannato complexes of type [M(SnCl 3)L 4] including [Ir(SnCl 3)(NBD)(1,5-COD)] have been prepared and characterized. Their δ( 119Sn), δ( 13C), δ( 195Pt) as well as 1J( 103Rh, 119Sn), 1J( 195Pt, 119Sn), 2J( 119Sn, 117Sn) and 2J( 119Sn, 13C) data are given. A trans influence series, based on 1J( 195Pt, 119Sn), reveals the following sequence: H ? > PR 3 > AsR 3 > SnCl 3? > olefin > Cl ?. 相似文献
18.
A new metal-metal bonded binuclear iron system [Me 2SiCH 2CH 2SiMe 2][η 5-C 5H 4Fe(CO) 2] 2 ( 2) has been prepared by treating two equivalents of NaCp with one equivalent of ClSi(Me) 2CH 2CH 2SiClMe 2 obtaining the intermediate (C 5H 5)Si(Me) 2CH 2CH 2Si(Me) 2(C 5H 5) which then is directly allowed to react with Fe(CO) 5 given 2 in 30% yield. From this cyclopentadienyldisilyl linked system three new binuclear irom complexes are formed. Treatment of 2 with Na/Hg in THF produced the dianion [Me 2SiCH 2CH 2SiMe 2][η 5-C 5H 4Fe(CO) 2?] 2 which is quenched with CH 3I giving [Me 2SiCH 2CH 2SiMe 2][η 5-C 4H 4Fe(CO) 2CH 3] 2 ( 4) in 76% yield. Complex 2 is oxidized with 1.2 equivalent of I 2 to give [Me 2SiCH 2CH 2SiMe 2][η 5-C 5H 4Fe(CO) 2I] 2 ( 5) in 85% yield. Photolysis of 5 (1 equiv.) and PPh 3 (3 equiv.) results in the formation of the bis-substituted compound [Me 2SiCH 2CH 2SiMe 2][η 5-C 5H 4Fe(CO)(PPh 3)I] 2 ( 6). These four new binuclear iron complexes are characterized by 1H, 13C, and 31P NMR and IR spectroscopy. 相似文献
19.
A series of novel first-generation silicon-centred tin dendrimers Si(CH 2CH 2SnR 3) 4 [R = CH 3 ( 3), iBu ( 4), CCCH 3 ( 5), C 6H 4CH 3-4 ( 6), C 6H 4OCH 3-4 ( 7), (CH 2) 4OCH 2CH 2OCH 3 ( 8), CH 2SiMe 3 ( 9)] was prepared by the reaction of Si(CH 2CH 2SnBr 3) 4 ( 2) with the appropriate Grignard reagent or LiCH 2SiMe 3 in tetrahydrofuran. The new compounds were characterized by multinuclear NMR studies ( 1H, 13C, 119Sn), mass spectrometry (MALDI-TOF, EI) and elemental analyses. The molecular structure of Si[CH 2CH 2SnBr 3(THF) 2] 2[CH 2-CH 2SnBr 3(THF)] 2 ( 2a) was determined by single-crystal X-ray diffraction. 相似文献
20.
The emission systems produced in He(2 3S)/SO 2, Ne( 3P 0,2)/SO 2 and Ar( 3P 0,2)/SO 2, afterglows have been investigated in the ultraviolet and visible spectral ranges. In all three afterglows we have identified previously unknown long—wavelenght progressions in the SO(A 3Π → X 3 σ ?) system and have assigned several new bands in the SO(B 3σ ? → X 3σ ?)system. Reducing the temperature of the helium gas flowing through a hollow cathode discharge source to 118K effectively removes helium ions from the stream, thus facilitating spectral studies in uncontaminated metastable afterglows. A further effect of cooling the rare gases He, Ne, and Ar is an improvement in the resolution of the emission spectra and an enhanced signal-to-noise ratio. bl 相似文献
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