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1.
The reaction of Ln(AlMe(4))(3) with bulky hydrotris(pyrazolyl)borate (Tp(t)(Bu,Me))H proceeds via a sequence of methane elimination and C-H bond activation, affording unprecedented rare-earth metal ligand moieties including Ln(Me)[(micro-Me)AlMe(3)] and X-ray structurally characterized "Tebbe-like" Ln[(micro-CH(2))(2)AlMe(2)].  相似文献   

2.
Two silylene nickel carbonyl complexes of composition L·Ni(CO)(3) (1) {L = PhC(NtBu)(2)SiCl} and L'(2)·Ni(CO)(2) (2) { L' = RSiCl(2), R = (1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene)} were prepared by reacting 1 equivalent of Ni(CO)(4) with 1 equivalent of heteroleptic chlorosilylene L for 1 and with 2 equivalents of carbene stabilized dichlorosilylene L' for 2 in toluene at room temperature. Both complexes 1 and 2 were characterized by single-crystal X-ray analysis, NMR and IR spectroscopy, EI-MS spectrometry, and elemental analysis.  相似文献   

3.
The abstraction of the Lewis acid from [W(CO)(5)(PH(2)BH(2)NMe(3))] (1) by an excess of P(OMe(3))(3) leads to the quantitative formation of the first Lewis base stabilized monomeric parent compound of phosphanylborane [H(2)PBH(2)NMe(3)] 2. Density functional theory (DFT) calculations have shown a low energetic difference between the crystallographically determined antiperiplanar arrangement of the lone pair and the trimethylamine group relative to the P-B core and the synperiplanar conformation. Subsequent reactions with the main-group Lewis acid BH(3) as well as with an [Fe(CO)(4)] unit as a transition-metal Lewis acid led to the formation of [(BH(3))PH(2)BH(2)NMe(3)] (3), containing a central H(3)B-PH(2)-BH(2) unit, and [Fe(CO)(4)(PH(2)BH(2)NMe(3))] (4), respectively. In oxidation processes with O(2), Me(3)NO, elemental sulfur, and selenium, the boranylphosphine chalcogenides [H(2)P(Q)BH(2)NMe(3)] (Q = S 5 b; Se 5 c) as well as the novel boranyl phosphonic acid [(HO)(2)P(O)BH(2)NMe(3)] (6 a) are formed. All products have been characterized by spectroscopic as well as by single-crystal X-ray structure analysis.  相似文献   

4.
Silyl enol ethers of ketones can be successfully selenoalkylated by Lewis acid activated seleno-ketals; the product β-seleno-ketones undergo interesting oxidation-deselenation reactions.  相似文献   

5.
L.I. Bosch  T.D. James 《Tetrahedron》2004,60(49):11175-11190
Cumulative formation constants for the association of three boronic acids (phenylboronic acid and its ortho-anilinomethyl and ortho-benzylaminomethyl derivatives) with four saccharides (fructose, glucose, mannitol, and sorbitol) were determined by potentiometric titration. Similarly, the constants for the formation binary complexes of the three boronic acids with (hydrogen) phosphate, (hydrogen) citrate, or imidazole were determined. Finally, the formation of ternary complexes of the boronic acids, phosphate, citrate or imidazole, and the saccharides were determined based on the determined values of the binary complexes. The previously unrecognized ternary complexes are significant in all systems investigated, and under some solution compositions, they can be the dominant species in solution over a wide pH range. A value of 15-25 kJ mol−1 was determined for the energy of the B-N interaction in the benzylmethyl derivative based on the relative stabilities of the ternary phosphate complexes of the three boronic acids. The data are used to rationalize the medium dependence of stepwise formation constants and the apparent acidity constants of previous literature reports.  相似文献   

6.
13C NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability. The β-carbon of acrylonitrile and methacrylonitrile showed a downfield shift due to the complex formation with the Lewis acid, while the α-carbon showed an upfield shift and the nitrile carbon showed no significant shift. The degree of shift of olefinic carbons decreased in the following order: AlCl3 > EtAlCl2 > Et1.5AlCl1.5 > Et2AlCl > SnCl4, EtOAlCl2 > Et(EtO)AlCl, which seems to run parallel to the Lewis acidity and acid strength. On the other hand, the chemical shift of olefinic carbons of methyl acrylate, methyl methacrylate, and olefinic diesters was influenced little by complex formation with Lewis acids, whereas the carbonyl and alkoxyl carbons were deshielded significantly by the complex formation. These results are discussed in terms of electron distribution on the carbons and an alternating polymerization mechanism.  相似文献   

7.
Divinyl ketones bearing alpha-ester or alpha-amide groups undergo Nazarov cyclizations to give cylopentenones using copper-bisoxazoline Lewis acid complexes with moderate to good ees. [reaction: see text]  相似文献   

8.
While reinvestigating the published synthesis of OPI(3), it became evident from the experiments that phosphoryl triodide may only be formed as an intermediate and that the end products of the reaction of OPCl(3) with LiI are P(V) oxides, PI(3), I(2), and LiCl. This is also in agreement with MP2/TZVPP calculations, which assign Delta(r)H degrees (Delta(r)G degrees ) [Delta(r)G degrees in CHCl(3)] for the disproportionation of OPI(3) as -7 (-18) [-17 kJ mol(-1)] (assuming P(4)O(10) as the P(V) oxide). The first products of this reaction visible in a low-temperature in situ (31)P NMR experiment are P(2)I(4) and PI(3), as well as traces of a compound that may be OPCl(2)I. By contrast, it was possible to prepare and structurally characterize Lewis acid [A] stabilized [A]<--OPX(3) adducts, where [A] is Al(OR(F))(3) for X=Br and Al(OR(F))(2)(mu-F)Al(OR(F))(3) for X=I (R(F)=C(CF(3))(3)). These adducts are formed on decomposition of PX(4) (+)[Al(OR(F))(4)](-); high yields of Br(3)PO-->Al(OR(F))(3) (delta((31)P)=-65) were obtained, while I(3)PO-->Al(OR(F))(3) (delta((31)P)=-337) and I(3)PO-->Al(OR(F))(2)(mu-F)Al(OR(F))(3) (delta((31)P)=-332) are only formed as by-products. The main product of the room-temperature decomposition of PI(4) (+)[Al(OR(F))(4)](-) is PI(4) (+)[(R(F)O)(3)Al(mu-F)Al(OR(F))(3)](-), which was also characterized by X-ray crystallography and was independently prepared from Ag(+)[(R(F)O)(3)Al(mu-F)Al(OR(F))(3)](-), PI(3), and I(2).  相似文献   

9.
Formation and characterization of thorium methylidene CH2=ThHX complexes   总被引:1,自引:0,他引:1  
Lyon JT  Andrews L 《Inorganic chemistry》2005,44(23):8610-8616
Laser-ablated thorium atoms react with methyl fluoride to give the CH2=ThHF molecule as the major product observed and trapped in solid argon. Infrared spectroscopy, isotopic substitution, and density functional theoretical frequency calculations confirm the identification of this methylidene complex. The four strongest computed absorptions (Th-H stretch, Th=C stretch, CH2 wag, and Th-F stretch) are the four vibrational modes observed. The CH2=ThHCl and CH2=ThHBr species formed from methyl chloride and methyl bromide exhibit the first three of these modes in the infrared spectra. The computed structures (B3LYP and CCSD) show considerable agostic interaction, similar to that observed for the Group 4 CH2=MHX (M = Ti, Zr, Hf) methylidene complexes, and the agostic angle and C=Th bond length decrease slightly in the CH2=ThHX series (X = F, Cl, Br).  相似文献   

10.
11.
The [ε-PMo(V)(8)Mo(VI)(4)O(36)(OH)(4){Ln(III)(H(2)O)}(4)](5+) (Ln=La, Ce, Nd, Sm) polyoxocations, called εLn(4), have been synthesized at room temperature as chloride salts soluble in water, MeOH, EtOH, and DMF. Rare-earth metals can be exchanged, and (31)P NMR spectroscopic studies have allowed a comparison of the affinity of the reduced {ε-PMo(12)} core, thus showing that the La(III) ions have the highest affinity and that rare earths heavier than Eu(III) do not react with the ε-Keggin polyoxometalate. DFT calculations provide a deeper insight into the geometries of the systems studied, thereby giving more accurate information on those compounds that suffer from disorder in crystalline form. It has also been confirmed by the hypothetical La→Gd substitution reaction energy that Ln ions beyond Eu cannot compete with La in coordinating the surface of the ε-Keggin molybdate. Two of these clusters (Ln=La, Ce) have been tested to evidence that such systems are representative of a new efficient Lewis acid catalyst family. This is the first time that the catalytic activity of polyoxocations has been evaluated.  相似文献   

12.
A potassium carbonate promoted addition of 2-bromonitroalkanes to methylidenemalonic and methylidenecyanoacetic acid derivatives and N-benzylmaleimide leads to the functionalized nitrocyclopropanes. In the case of less active olefins, it is reasonable to use the phase-transfer catalyst Bu4NPF6 (10 mol.%), whereas in the case of N-benzylmaleimide, to carry out the process in the ionic liquid [bmim]BF4.  相似文献   

13.
14.
Unsolvated, trinuclear, homometallic, rare-earth-metal multimethyl methylidene complexes [{(NCN)Ln(μ(2)-CH(3))}(3)(μ(3)-CH(3))(μ(3)-CH(2))] (NCN = L = [PhC{NC(6)H(4)(iPr-2,6)(2)}(2)](-); Ln = Sc (2a), Lu (2b)) have been synthesized by treatment of [(L)Ln{CH(2)C(6)H(4)N(CH(3))(2)-o}(2)] (Ln = Sc (1a), Lu (1b)) with two equivalents of AlMe(3) in toluene at ambient temperature in good yields. Treatment of 1 with three equivalents of AlMe(3) gives the heterometallic trinuclear complexes [(L)Ln(AlMe(4))(2)] (Ln = Sc (3a), Lu (3b)) in good yields. Interestingly, 2 can also be generated by recrystallization of 3 in THF/toluene, thereby indicating that the THF molecule can also induce C-H bond activation of 2. Reaction of 2 with one equivalent of ketones affords the trinuclear homometallic oxo-trimethyl complexes [{(L)Ln(μ(2) -CH(3))}(3) (μ(3)-CH(3))(μ(3)-O)] (Ln = Sc(4a), Lu(4b)) in high yields. Complex 4b reacts with one equivalent of cyclohexanone to give the methyl abstraction product [{(L)Lu(μ(2) -CH(3) )}(3) (μ(3) -OC(6)H(9))(μ(3)-O)] (5b), whereas reaction of 4b with acetophenone forms the insertion product [{(L)Lu(μ(2)-CH(3))}(3){μ(3)-OCPh(CH(3))(2)}(μ(3)-O)] (6b). Complex 4a is inert to ketone under the same conditions. All these new complexes have been characterized by elemental analysis, NMR spectroscopy, and confirmed by X-ray diffraction determination.  相似文献   

15.
16.
Novel boron-ammonia complexes, wherein an NH(3) molecule is tightly bound through all four of its atoms, have been prepared and studied. The solid-state structure of ortho MOM-phenyllithium is reported. [reaction: see text]  相似文献   

17.
The ligation of a N-heterocyclic carbene (NHC) to group 11 metal salts (Cu, Ag) was explored as an alternative to PR(3) ligands for the formation of copper- and silver-chalcogenolate cluster complexes. AgOAc and CuCl salts ligate with the NHC 1,3-di-isopropylbenzimidazole-2-ylidene ((i)Pr(2)-bimy) forming [Ag(OAc)((i)Pr(2)-bimy)] 1, [Ag(OAc)((i)Pr(2)-bimy)(2)] 2, [CuCl((i)Pr(2)-bimy)](2)3 and [CuCl((i)Pr(2)-bimy)(2)] 4 depending on the ratio of ligand to metal used. These have been characterized via spectroscopic and crystallographic methods. Complexes 1 and 3 were reacted with S(Ph)SiMe(3) and Se(Ph)SiMe(3) to form the polynuclear metal-chalcogenolates [Ag(4)(μ-EPh)(4)((i)Pr(2)-bimy)(4)] (5, E = S; 6, E = Se) and [Cu(3)(μ-EPh)(3)((i)Pr(2)-bimy)(3)] (7, E = S; 8, E = Se) in good yields. The structures of 5-8, as determined by single crystal X-ray crystallography, are described.  相似文献   

18.
19.
New magnesium complexes, [Et2Mg3(dmamp)4] (1) and [(CH2=CH)2Mg3(dmamp)4] (2), were prepared by the reaction of alkylmagnesium bromide with sodium 1-dimethylamino-2-methyl-2-propoxide [Na(dmamp)] in THF. Complexes 1 and 2 were characterized by 1H and 13C NMR spectroscopies, FTIR spectroscopy, elemental analysis, and single-crystal X-ray diffraction (XRD) analysis. The XRD analysis showed that these complexes are trinuclear where the alkoxy O is the μ2-O bridge between the Mg ions. Among the three metal centers, the two terminal Mg ions are five coordinate and have a square–pyramidal geometry, whereas the central Mg is four coordinate with a distorted tetrahedral geometry. The combination of ethyl and vinyl groups with sterically bulky aminoalkoxide ligands plays an important role in stabilizing the molecule.  相似文献   

20.
The reaction of [Ti(NR)Cl(2)(py)(3)](R = (t)Bu, p-tolyl, 2,6-C(6)H(3)(i)Pr(2)) with [{Li(bdmpza)(H(2)O)}(4)][bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] and [{Li(bdmpzdta)(H(2)O)}(4)][bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate] affords the corresponding complexes [Ti(NR)Cl(kappa(3)-bdmpzx)(py)](x = a, R = (t)Bu 1, p-tolyl 2, 2,6-C(6)H(3)(i)Pr(2) 3; x = dta, R =(t)Bu 4, p-tolyl , 2,6-C(6)H(3)(i)Pr(2) 6), which are the first examples of imido Group 4 complexes stabilized by heteroscorpionate ligands. The solid-state X-ray crystal structure of 1 has been determined. The titanium centre is six-coordinate with three fac-sites occupied by the heteroscorpionate ligand and the remainder of the coordination sphere being completed by chloride, imido and pyridine ligands. The complexes are 1-6 fluxional at room temperature. The pyridine ortho- and meta-proton resonances show evidence of dynamic behaviour for this ligand and variable-temperature NMR studies were carried out in order to study their dynamic behaviour in solution. The complexes [Nb(NR)Cl(3)(py)(2)](R = (t)Bu, p-tolyl, 2,6-C(6)H(3)(i)Pr(2)) reacted with [{Li(bdmpza)(H(2)O)}(4)] and (Hbdmpze)[bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide], the latter with prior addition of (n)BuLi, to give the complexes [Nb(NR)Cl(2)(kappa(3)-bdmpzx)](x = a, R =(t)Bu 7, p-tolyl 8, 2,6-C(6)H(3)(i)Pr(2) 9; x = e, R = (t)Bu 10, p-tolyl 11, 2,6-C(6)H(3)(i)Pr(2)) 12 and these are the first examples of imido Group 5 complexes with heteroscorpionate ligands. The structures of these complexes have been determined by spectroscopic methods.  相似文献   

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