C-H...N and C-H...S hydrogen bonds--influence of hybridization on their strength

Simple complexes connected through C-H...S and C-H...N interactions are investigated: CH4...NH3, C2H4...NH3, C2H2...NH3, CH4...SH2, C2H4...SH2, and C2H2...SH2. Ab initio and DFT calculations are performed (SCF, MP2, B3LYP) using different basis sets up to the MP2/aug-cc-pVQZ//MP2/aug-cc-pVDZ level of approximation. The Bader theory is applied since MP2/6-311++G(d,p) wave functions are used to find and to characterize bond critical points in terms of electron densities and their Laplacians. The influence of hybridization on the properties of C-H...S and C-H...N systems is also studied showing that the strength of such interactions increases in the following order: C(sp3)-H...Y, C(sp2)-H...Y, C(sp)-H...Y, where Y = S, N--it is in line with the previous findings on C-H...O hydrogen bonds. The results also show that CH4...SH2 and C2H4...SH2 complexes should be rather classified as van der Waals interactions and not as hydrogen bonds. The frequency associated with the C-H stretch of C(sp3)-H...S is blue-shifted.     

sp carbon chains surrounded by sp(3) carbon double helices: directed syntheses of wirelike Pt(CC)(n)Pt moieties that are spanned by two P(CH(2))(m)P linkages via alkene metathesis

Reactions of trans-(C6F5)(Ph2P(CH2)m'CH=CH2)2PtCl (1; m' = a, 6; b, 7; c, 8; d, 9; e, 10) and H(CC)2H (HNEt2, cat. CuI) give trans-(C6F5)(Ph2P(CH2)m'CH=CH2)2Pt(CC)2H (3a-e, 80-95%). Oxidative homocouplings of 3a-d under Hay conditions (O2, cat. CuCl/TMEDA, acetone) yield trans,trans-(C6F5)(Ph2P(CH2)m'CH=CH2)2Pt(CC)4Pt(Ph2P(CH2)m'CH=CH2)2(C6F5) (4a-d, 64-84%). Treatment of 3c-e with excess HCCSiEt3 under Hay conditions gives trans-(C6F5)(Ph2P(CH2)m'CH=CH2)2Pt(CC)3SiEt3 (56-73%). Homocouplings (n-Bu4N+ F-, Me3SiCl, Hay conditions) afford trans,trans-(C6F5)(Ph2P(CH2)m'CH=CH2)2Pt(CC)6Pt(Ph2P(CH2)m'CH=CH2)2(C6F5) (13c-e, 59-64%). Reactions of 4a-d and 13c-e with Grubbs' catalyst, followed by hydrogenation, give mixtures of trans,trans-(C6F5)(Ph2P(CH2)mPPh2)Pt(CC)nPt(Ph2P(CH2)mPPh2)(C6F5) with termini-spanning diphosphines and trans,trans-(C6F5)(Ph2P(CH2)mPPh2)Pt(CC)nPt(Ph2P(CH2)mPPh2)(C6F5) with trans-spanning diphosphines (m = 2m' + 2; n = 4, 6). The latter (n = 4) are independently synthesized by similar metatheses/hydrogenations of 1a-d to give trans-(C6F5)(Ph2P(CH2)mPPh2)PtCl (49-59%), followed by analogous introductions of (CC)4 chains (66-77%). Crystal structures of complexes with termini-spanning diphosphines show sp3 chains with both double-helical (m/n = 20/4) and nonhelical (m/n = 20/6) conformations, and highly shielded sp chains. The sp3 chains of complexes with trans-spanning diphosphines exhibit double half-clamshell conformations. The dynamic properties of both classes of molecules are analyzed in detail.     

Experimental study and detailed modeling of toluene degradation in a low-pressure stoichiometric premixed CH4/O2/N2 flame

Temperature and mole fraction profiles have been measured in laminar stoichiometric premixed CH4/O2/N2 and CH4/1.5%C6H5CH3/O2/N2 flames at low pressure (0.0519 bar) by using thermocouple, molecular beam/mass spectrometry (MB/MS), and gas chromatography/mass spectrometry (GC/MS) techniques. The present study completes our previous work performed on the thermal degradation of benzene in CH4/O2/N2 operating at similar conditions. Mole fraction profiles of reactants, final products, and reactive and stable intermediate species have been analyzed. The main intermediate aromatic species analyzed in the methane-toluene flame were benzene, phenol, ethylbenzene, benzylalcohol, styrene, and benzaldehyde. These new experimental results have been modeled with our previous model including submechanisms for aromatics (benzene up to p-xylene) and aliphatic (C1 up to C7) oxidation. Good agreement has been observed for the main species analyzed. The main reaction paths governing the degradation of toluene in the methane flame were identified, and it occurs mainly via the formation of benzene (C6H5CH3 + H = C6H6 + CH3) and benzyl radical (C6H5CH3 + H = C6H5CH2 + H2). Due to the abundance of methyl radicals, it was observed that recombination of benzyl and methyl is responsible for main monosubstitute aromatic species analyzed in the methane-toluene flame. The oxidation of these substitute species led to cyclopentadienyl radical as observed in a methane-benzene flame.     

Coordination-driven self-assembly, structures, and dynamic properties of diplatinum hexatriynediyl and butadiynediyl complexes in which the sp carbon chains are shielded by sp3 carbon chains: towards endgroup-endgroup interactions

Sequential reactions of trans-(C6F5)(p-tol3P)2Pt(C[triple chemical bond]C)3SiEt3 (PtC6SiEt3) with nBu4N+ F(-) (THF/methanol), PtCl, KPF6/tBuOK, and CuCl give trans,trans-[(C6F5){(p-tol3P)2}Pt(C[triple chemical bond]C)3Pt{(Pp-tol3)2}(C6F5)] (PtC6Pt) in 95 % yield on multigram scales. Reactions of PtC6Pt and Ar2P(CH2)mPAr2 afford substitution products trans,trans-[(C6F5){(Ar2P(CH2)mPAr2)}Pt(C[triple chemical bond]C)3Pt{(Ar2P(CH2)mPAr2)}(C6F5)] (PtC6Pt-m/Ar; m/Ar=8/p-tol, 78 %; 10/Ph, 82 %; 11/Ph, 69 %; 12/Ph, 57 %; 14/p-tol, 57 %; 14/p-C6H4-tBu, 71 %), in which the diphosphines span the square planar platinum endgroups. An analogous reaction with PEt3 gives a tetrakis PEt3 complex Pt'C6Pt' (72 %). The crystal structures of PtC6Pt, Pt'C6Pt', PtC6Pt-10/Ph, PtC6Pt-11/Ph, and PtC6Pt-14/p-tol or solvates thereof are compared. In PtC6Pt, the endgroups can avoid van der Waals contact, and define angles of 0 degrees . In PtC6Pt-14/p-tol, the sp3 chains twist around the sp chain in a chiral double-helical motif, with an endgroup/endgroup angle of 189 degrees . The sp3 chains are too short to adopt analogous conformations in the other complexes, but laterally shield the sp chain. NMR spectroscopy shows that the helical enantiomers of PtC6Pt-14/p-tol rapidly interconvert in solution at low temperature. A crystal structure of PtC4Pt shows endgroups that are in van der Waals contact and define an angle of 41 degrees . Reactions with Ar2P(CH2)8PAr2 give PtC4Pt-8/Ar (Ar=Ph, 53 %; p-tol, 87 %). Low-temperature NMR spectroscopy establish non-helical chiral conformations. Electrochemical oxidations of the diplatinum complexes are analyzed, the reversibilities of which decrease with increasing sp chain length.     

Electronic and molecular structure of aminimides (1-acyl-2,2,2-trimethyldiazan-2-ium-1-ide). 1. Formaminimide (HCON- N+ Me3)

The electronic structure and geometries of (Z)- and (E)-H-CON- N+(CH3)3 have been examined at two levels of theory: B3LYP (basis sets 6-311+G(d,p), 6-311++G(d,p), and 6-311G(3df,3pd)) and MP2(full)/6-311++G(d,p). The (Z) conformation about the C(O)-N(-) bond is thermodynamically preferred over the (E) configuration. Natural bond orbital calculation locates one lone pair of the N- in the HOMO, which is the p(z) natural hybrid orbital (perpendicular to the O=CN- N+ plane). The second lone pair (of lower energy) of N- occupies the HOMO-3, which is the natural hybrid orbital sp(1.12) (sp(1.01) for the (E) conformation, sp(1.74) in the rotational transition state). The carbonyl pi bond is the HOMO-2. The charge-transfer ability of the negative nitrogen in H-CON- N+ (CH3)3 is more powerful than that of the neutral amidic nitrogen in dimethylformamide. The following facts convincingly sustain this view: (1) the higher rotational barrier (stronger C-N(-) bond) in the case of H-CON- N+ (CH3)3, (2) natural resonance theory analysis predicts almost equal weights for the (Z)-H-C(=O)N- N+ (CH3)3 and the (Z)-H-C(O-)=NN+ (CH3)3 canonical resonance structures whereas the weight of the HCON(CH3)2 structure is almost twice as large as that of HC(O-)=N+ (CH3)2, and (3) the second-order perturbation stabilization, as a result of the donor (N-)/acceptor (carbonyl) interaction, is 101.3 kcal/mol for H-CON- N+ (CH3)3 and only 64.4 kcal/mol for dimethylformamide.     

(tBu2PCH2SiMe2)2N]RuCH3: the origin of extremely facile, double H-C(sp3) activation generating a "hydrido-carbene" complex

The four-coordinate compound [(tBu2PCH2SiMe2)2N]RuCH3 undergoes rapid double H-C(sp3) activation at -78 degrees C to generate a "hydrido-carbene" complex. DFT calculations suggest that the origin of the low barrier to methane elimination is an alpha-agostic interaction in the low-lying singlet state of the highly unsaturated (PNP)RuMe. The hydrido-carbene complex can be viewed as a "masked" resting state of the four-coordinate cyclometalated alkyl complex, [(tBu2PCH2SiMe2)N(Me2SiCH2P(tBu)(C(CH3)2CH2)]Ru, where hydride migration from metal to carbon occurs before any subsequent reactivity.     

ENDOR/HYSCORE studies of the common intermediate trapped during nitrogenase reduction of N2H2, CH3N2H, and N2H4 support an alternating reaction pathway for N2 reduction

Enzymatic N(2) reduction proceeds along a reaction pathway composed of a sequence of intermediate states generated as a dinitrogen bound to the active-site iron-molybdenum cofactor (FeMo-co) of the nitrogenase MoFe protein undergoes six steps of hydrogenation (e(-)/H(+) delivery). There are two competing proposals for the reaction pathway, and they invoke different intermediates. In the 'Distal' (D) pathway, a single N of N(2) is hydrogenated in three steps until the first NH(3) is liberated, and then the remaining nitrido-N is hydrogenated three more times to yield the second NH(3). In the 'Alternating' (A) pathway, the two N's instead are hydrogenated alternately, with a hydrazine-bound intermediate formed after four steps of hydrogenation and the first NH(3) liberated only during the fifth step. A recent combination of X/Q-band EPR and (15)N, (1,2)H ENDOR measurements suggested that states trapped during turnover of the α-70(Ala)/α-195(Gln) MoFe protein with diazene or hydrazine as substrate correspond to a common intermediate (here denoted I) in which FeMo-co binds a substrate-derived [N(x)H(y)] moiety, and measurements reported here show that turnover with methyldiazene generates the same intermediate. In the present report we describe X/Q-band EPR and (14/15)N, (1,2)H ENDOR/HYSCORE/ESEEM measurements that characterize the N-atom(s) and proton(s) associated with this moiety. The experiments establish that turnover with N(2)H(2), CH(3)N(2)H, and N(2)H(4) in fact generates a common intermediate, I, and show that the N-N bond of substrate has been cleaved in I. Analysis of this finding leads us to conclude that nitrogenase reduces N(2)H(2), CH(3)N(2)H, and N(2)H(4) via a common A reaction pathway, and that the same is true for N(2) itself, with Fe ion(s) providing the site of reaction.     

N2 provides insight into the mechanism of H-C(sp3) bond cleavage

Exchange of deuterium in d6-benzene with all C-H sites in (PNP)Ru(OTf), where PNP is N(SiMe2CH2PtBu2)2 and OTf is OSO2CF3, is rapid at 22 degrees C. Although intact planar triplet (PNP)Ru(OTf) binds N2 only very weakly, these reagents are observed to react rapidly to give a diamagnetic 1:1 adduct whose structure has one tBu C-H bond cleaved: the carbon binds to Ru but the hydrogen is on the PNP nitrogen, creating a secondary amine ligand bound to RuII. It is suggested that the benzene C-D cleavage and the N2 product of tBu C-H bond heterolysis both derive from a common intermediate, [HN(SiMe2CH2PtBu2)(SiMe2CH2PtBuCMe2CH2)] Ru(OTf); the formation energy and structure of this species are discussed on the basis of DFT results.     

Titanium, zinc and alkaline-earth metal complexes supported by bulky O,N,N,O-multidentate ligands: syntheses, characterisation and activity in cyclic ester polymerisation

The reactions of the bulky amino-bis(phenol) ligand Me(2)NCH(2)CH(2)N[CH(2)-3,5-Bu(t)(2)-C(6)H(2)OH-2](2)(1-H(2)) with Zn[N(SiMe(3))(2)](2)(4), [Mg[N(SiMe(3))(2)](2)](2)(5) and Ca[N(SiMe(3))(2)](2)(THF)(2)(6) yield the complexes 1-Zn, 1-Mg and 1-Ca in good yields. The X-ray structure of 1-Ca showed the complex to be dimeric, with calcium in a distorted octahedral coordination geometry. Five of the positions are occupied by an N(2)O(3) donor set, while the sixth is taken up by an intramolecular close contact to an o-Bu(t) substituent, a rare case of a Ca...H-C agostic interaction (Ca...H distances of 2.37 and 2.41 Angstroms). Another sterically hindered calcium complex, Ca[2-Bu(t)-6-(C(6)F(5)N=CH)C(6)H(3)O](2)(THF)(2).(C(7)H(8))(2/3)(7), was prepared by reaction of 6 with the iminophenol 2-Bu(t)-6-(C(6)F(5)N=CH)C(6)H(3)OH (3-H). According to the crystal structure 7 is monomeric and octahedral, with trans THF ligands. The complex Ti[N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)O-2](2)[CH(2)CH(2)NMe(2)]](OPr(i))(2)(2-Ti) was prepared by treatment of Ti(OPr(i)(4)) with the new amino-bis(phenol) Me(2)NCH(2)CH(2)N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)OH-2](2)(2-H(2)). The reduction of 2-Ti with sodium amalgam gave the titanium(III) salt Ti[N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)O-2](2)[CH(2)CH(2)NMe(2)]](OPr(i))(2).Na(THF)(2)(8). A comparison of the X-ray structures of 2-Ti and 8 showed that the additional electron in 8 significantly reduced the intensity of the pi-bonding from the oxygen atoms of the isopropoxide groups to titanium. 1-Ca and 8 were active initiators for the ring-opening polymerisation of epsilon-caprolactone (up to 97% conversion of 200 equivalents in 2 hours) and yielded polymers with narrow molecular weight distributions.     

The heats of formation of diazene, hydrazine, N2H3+, N2H5+, N2H, and N2H3 and the Methyl Derivatives CH3NNH, CH3NNCH3, and CH3HNNHCH3

The heats of formation of N(2)H, diazene (cis- and trans-N(2)H(2)), N(2)H(3), and hydrazine (N(2)H(4)), as well as their protonated species (diazenium, N(2)H(3)(+), and hydrazinium, N(2)H(5)(+)), have been calculated by using high level electronic structure theory. Energies were calculated by using coupled cluster theory with a perturbative treatment of the triple excitations (CCSD(T)) and employing augmented correlation consistent basis sets (aug-cc-pVnZ) up to quintuple-zeta, to perform a complete basis set extrapolation for the energy. Geometries were optimized at the CCSD(T) level with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. Core-valence and scalar relativistic corrections were included, as well as scaled zero point energies. We find the following heats of formation (kcal/mol) at 0 (298) K: DeltaH(f)(N(2)H) = 60.8 (60.1); DeltaH(f)(cis-N(2)H(2)) = 54.9 (53.2); DeltaH(f)(trans-N(2)H(2)) = 49.9 (48.1) versus >/=48.8 +/- 0.5 (exptl, 0 K); DeltaH(f)(N(2)H(4)) = 26.6 (23.1) versus 22.8 +/- 0.2 (exptl, 298 K); DeltaH(f)(N(2)H(3)) = 56.2 (53.6); DeltaH(f)(N(2)H(3)(+)) = 231.6 (228.9); and DeltaH(f)(N(2)H(5)(+)) = 187.1 (182.7). In addition, we calculated the heats of formation of CH(3)NH(2), CH(3)NNH, and CH(3)HNNHCH(3) by using isodesmic reactions and at the G3(MP2) level. The calculated results for the hydrogenation reaction RNNR + H(2) --> RHNNHR show that substitution of an organic substituent for H improved the energetics, suggesting that these types of compounds may be possible to use in a chemical hydrogen storage system.     

sp carbon chains surrounded by sp(3) carbon double helices: coordination-driven self-assembly of wirelike Pt(CC)(n)Pt moieties that are spanned by two P(CH(2))(m)P linkages

Reactions of trans,trans-(C6F5)(p-tol3P)2Pt(CC)4Pt(Pp-tol3)2(C6F5) and diphosphines Ar2P(CH2)mPAr2 yield trans,trans-(C6F5)(Ar2P(CH2)mPAr2)Pt(CC)4Pt(Ar2P(CH2)mPAr2)(C6F5), in which the platinum atoms are spanned via an sp and two sp3 carbon chains (Ar/m = 3, Ph/14, 87%; 4, p-tol/14, 91%; 5, p-C6H4-t-Bu/14, 77%; 7, Ph/10, 80%; 8, Ph/11, 80%; 9, Ph/12, 36%; only oligomers form for m > 14). Crystal structures of 3-5 show that the sp3 chains adopt chiral double-helical conformations that shield the sp chain at approximately the van der Waals distance, with both enantiomers in the unit cell. The platinum square planes define angles of 196.6 degrees -189.9 degrees or more than a half twist. Crystal structures of 7-9, which have shorter sp3 chains, exhibit nonhelical conformations. Reaction of the corresponding Pt(CC)6Pt complex and Ph2P(CH2)18PPh2 gives an analogous adduct (27%). The crystal structure shows two independent molecules, one helical and the other not. Low-temperature NMR data suggest that the enantiomeric helical conformations of 3-5 rapidly interconvert in solution. Cyclic voltammograms of 3-5 show more reversible oxidations than model compounds lacking bridging sp3 chains. These are the only double-helical molecules that do not feature bonding interactions between the helix strands, or covalent bonds to templates dispersed throughout the strands, or any type of encoding. The driving force for helix formation is analyzed.     

Wire-like PtC[triple bond]CC[triple bond]CC[triple bond]CC[triple bond]CPt moieties surrounded by double-helical "insulation": new motifs featuring P(CH2)20P and P(CH2)4O(CH2)2O(CH2)4P linkages

Ring-closing alkene metatheses of trans,trans-(C6F5)(Ph2P-Z-CH=CH2)2Pt(C[triple bond]C)4Pt(Ph2P-Z-CH=CH2)2(C6F5) (Z = (CH2)9, (CH2)4O(CH2)2), followed by hydrogenation, give the title compounds; the former exhibits an exceptionally twisted conformation, and the latter establishes that functional groups can be incorporated into the flexible sp3 chain.     

Flexible N,N,N-chelates as supports for iron and cobalt chloride complexes; synthesis, structures, DFT calculations and ethylene oligomerisation studies

The aryl-substituted N-picolylethylenediamine and diethylenetriamine ligands, (ArNHCH(2)CH(2))[(2-C(5)H(4)N)CH(2)]NH and (ArNHCH(2)CH(2))(2)NH (Ar = 2,6-Me(2)C(6)H(3), 2,4,6-Me(3)C(6)H(2)), have been prepared by employing palladium-catalysed N-C(aryl) coupling reactions of the corresponding primary amines with aryl bromide. Treatment of MCl(2) with (ArNHCH(2)CH(2))[(2-C(5)H(4)N)CH(2)]NH affords [[(ArNHCH(2)CH(2))((2-C(5)H(4)N)CH(2))NH]CoCl(2)](Ar = 2,6-Me(2)C(6)H(3) 1a; 2,4,6-Me(3)C(6)H(2)) 1b and [[(ArNHCH(2)CH(2))((2-C(5)H(4)N)CH(2))NH]FeCl(2)](n)(n= 1, Ar = 2,6-Me(2)C(6)H(3) 2a; n= 2, 2,4,6-Me(3)C(6)H(2) 2b) in high yield. The X-ray structures of 1a and 1b are isostructural and reveal the metal centres to adopt distorted trigonal bipyramidal geometries with the N,N,N-chelates adopting fac-structures. A facial coordination mode of the ligand is also observed in bimetallic 2b, however, in 2a the N,N,N-chelate adopts a mer-configuration with the metal centre adopting a geometry best described as square pyramidal. Solution studies indicate that mer-fac isomerisation is a facile process for these systems at room temperature. Quantum mechanical calculations (DFT) have been performed on 1a and 2a, in which the ligands employed are identical, and show the fac- to be marginally more stable than the mer-configuration for cobalt (1a) while for iron (2a) the converse is evident. Reaction of (ArNHCH(2)CH(2))(2)NH with CoCl(2) gave the five-coordinate complexes [[(ArNHCH(2)CH(2))(2)NH]CoCl(2)](Ar = 2,6-Me(2)C(6)H(3) 3a, 2,4,6-Me(3)C(6)H(2) 3b), in which the ligand adopts a mer-configuration; no reaction occurred with FeCl(2). All complexes 1-3 act as modest ethylene oligomerisation catalysts on activation with excess methylaluminoxane (MAO); the iron systems giving linear alpha-olefins while the cobalt systems give mixtures of linear and branched products.     

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

The pyrolysis of the simplest azides HN(3) and CH(3)N(3) has been studied computationally. Nitrogen extrusion leads to the production of NH or CH(3)N. The azides have singlet ground states but the nitrenes CH(3)N and NH have triplet ground states. The competition between spin-allowed decomposition to the excited state singlet nitrenes and the spin-forbidden N(2) loss is explored using accurate electronic structure methods (CASSCF/cc-pVTZ and MR-AQCC/cc-pVTZ) as well as statistical rate theories. Nonadiabatic rate theories are used for the dissociation leading to the triplet nitrenes. For HN(3), (3)NH formation is predicted to dominate at low energy, and the calculated rate constant agrees very well with energy-resolved experimental measurements. Under thermal conditions, however, the singlet and triplet pathways are predicted to occur competitively, with the spin-allowed product increasingly favored at higher temperatures. For CH(3)N(3) thermolysis, spin-allowed dissociation to form (1)CH(3)N should largely dominate at all temperatures, with spin-forbidden formation of (3)CH(3)N almost negligible. Singlet methyl nitrene is very unstable and should rearrange to CH(2)NH immediately upon formation, and the latter species may lose H(2) competitively with vibrational cooling, depending on temperature and pressure.     

The chemical composition and bonding structure of amorphous hydrogenated carbon nitride film on aluminum surface deposited by electrodeposition

Amorphous hydrogenated carbon nitride films with excellent adhesion to the substrates were deposited on the surfaces of aluminum plates by electrodeposition with acetonitrile as carbon source. The as‐obtained films were detailed characterized by Raman, XPS and FTIR. The results show that the as‐obtained films are mainly made up of sp2 C, sp3 C, C? N, C?N bonds and a spot of sp3? CH₂, sp3? CH₃, sp3? CH and sp2? CH bonds. The atomic ratio of N/C is evaluated to be about 2.98 at.% by XPS. Raman analysis indicated that I_D/I_G ratios decreased from 0.827 to 0.675 when the deposition time increased from 10 to 20 h. At the end, on the basis of the detailed analysis, results of Raman, FTIR and XPS, the possible deposition mechanism was discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

碳氟醇对阳离子表面活性剂表面活性及胶团反离子结合度的影响

用表面张力及电动势法研究了C₁₀H₂₁N(CH₃)3Br、C₁₂H₂₅N(CH₃)3Br与C₃F₇CH₂OH混合水溶液的表面与胶团性质。结果表明,对于阳离子表面活性剂,C₃F₇CH₂OH的加入一方面增加表面活性,另一方面降低胶团反离子结合度。后者不同于阴离子表面活性剂/C₃F₇CH₂OH混合体系,可归因于C₃F₇CH₂OH略有酸性,因而具备一些类似阴离子表面活性剂的性质。     

Steric control over the formation of cis and trans bis-chelated palladium(II) complexes using a new series of flexible N,P pyridyl-phosphine ligands

The deprotection of phosphonium chloride salts [PR2(CH2OH)2]+Cl- and subsequent condensation reaction with N-methyl-2-aminopyridine has been carried out to give a series of ligands of the form PR2CH2N(CH3)C5H4N (R=Ph , Cy , t-Bu ) which have been fully characterised either as the pure ligand () or the air stable borane adducts (R=Cy , t-Bu ). The 1:1 reactions of , and with PdCl2(COD) gave the N,P chelate complexes [Pd{PR2CH2N(CH3)C5H4N}Cl2]; the Cy () and t-Bu () complexes were characterised by X-ray crystallography. The bisligated species [Pd{PCy2CH2N(CH3)C5H4N}2Cl2] () was obtained when the reaction was carried out at higher temperatures and the ligands were found to be coordinated to the metal in a trans configuration through the phosphorus donors. Abstraction of the chlorides from the bis-ligated species , using silver salts, resulted in the coordination of the pyridine ring forming the bis-chelate complex [Pd{PCy2CH2N(CH3)C5H4N}2]2+. In comparison, the palladium bis-chelate complex of ligand [Pd{PPh2CH2N(CH3)C5H4N}2]2+ () was shown to form in a cis configuration and was fully characterised by X-ray crystallography.     

A New Family of Chalcogen Bearing Macrocycles: Synthesis and Characterization of N 4 O 2 E 2 (E = Se,Te) Type Compounds

A new series of 24- and 28-membered macrocyclic systems associated with "hard" (N and O) and "soft" (Se or Te) donor atoms have been developed via template free (2 + 2) condensation reactions of bis(aminoalkyl)selenides/tellurides, {NH 2 (CH 2 ) n } 2 E (E = Se, Te; n = 2,3) with 2,6-diacetyl-4-methylphenol. A macroacycle, Se{(CH 2 ) 2 N=C(CH 3 )C 6 H 2 (OH)(CH 3 )C=O(CH 3 )} 2 , has also been obtained. These compounds have been characterized by ESMS, IR, and 1 H, 13 C, and 77 Se NMR spectroscopy.     

Chemical reaction studies in CH4/Ar and CH4/N2 gas mixtures of a dielectric barrier discharge

Chemical reactions in a dielectric barrier discharge at medium pressure of 250-300 mbar have been studied in CH(4)/Ar and CH(4)/N(2) gas mixtures by means of mass spectrometry. The main reaction scheme is production of H(2) by fragmentation of CH(4), but also production of higher order hydrocarbon molecules such as C(n)H(m) with n up to 9 including formation of different functional CN groups is observed. Formation of C(2)H(2), C(2)H(4), and C(2)H(6) molecules has been investigated in some detail. Significant differences are noted in comparison to a theoretical estimate.     

Mechanistic Insights into C(sp2)−C(sp)N Reductive Elimination from Gold(III) Cyanide Complexes

A new family of phosphine-ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary ^12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp²)−C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp³)−C(sp³), C(sp²)−C(sp²), and C(sp³)−C(sp²) bond formation processes taking place on gold(III) species.