Vanadium complexes of the N(CH2CH2S)3(3-) and O(CH2CH2S)2(2-) ligands with coligands relevant to nitrogen fixation processes

Vanadium(III) and vanadium(V) complexes derived from the tris(2-thiolatoethyl)amine ligand [(NS3)3-] and the bis(2-thiolatoethyl)ether ligand [(OS2)2-] have been synthesized with the aim of investigating the potential of these vanadium sites to bind dinitrogen and activate its reduction. Evidence is presented for the transient existence of (V(NS3)(N2)V(NS3), and a series of mononuclear complexes containing hydrazine, hydrazide, imide, ammine, organic cyanide, and isocyanide ligands has been prepared and the chemistry of these complexes investigated. [V(NS3)O] (1) reacts with an excess of N2H4 to give, probably via the intermediates (V(NS3)(NNH2) (2a) and (V(NS3)(N2)V(NS3) (3), the V(III) adduct [V(NS3)(N2H4)] (4). If 1 is treated with 0.5 mol of N2H4, 0.5 mol of N2 is evolved and green, insoluble [(V(NS3))n] (5) results. Compound 4 is converted by disproportionation to [V(NS3)(NH3)] (6), but 4 does not act as a catalyst for disproportionation of N2H4 nor does it act as a catalyst for its reduction by Zn/HOC6H3Pri2-2,6. Compound 1 reacts with NR1(2)NR2(2) (R1 = H or SiMe3; R2(2) = Me2, MePh, or HPh) to give the hydrazide complexes [V(NS3)(NNR2(2)] (R2(2) = Me2, 2b; R2(2) = MePh, 2c; R2(2) = HPh, 2d), which are not protonated by anhydrous HBr nor are they reduced by Zn/HOC6H3Pri2-2,6. Compound 2b can also be prepared by reaction of [V(NNMe2)(dipp)3] (dipp = OC6H3Pri2-2,6) with NS3H3. N2H4 is displaced quantitatively from 4 by anions to give the salts [NR3(4)][V(NS3)X] (X = Cl, R3 = Et, 7a; X = Cl, R3 = Ph, 7b; X = Br, R3 = Et, 7c; X = N3, R3 = Bu(n), 7d; X = N3, R3 = Et, 7e; X = CN, R3 = Et, 7f). Compound 6 loses NH3 thermally to give 5, which can also be prepared from [VCl3(THF)3] and NS3H3/LiBun. Displacement of NH3 from 6 by ligands L gives the adducts [V(NS3)(L)] (L = MeCN, nu CN 2264 cm-1, 8a; L = ButNC, nu NC 2173 cm-1, 8b; L = C6H11NC, nu NC 2173 cm-1, 8c). Reaction of 4 with N3SiMe3 gives [V(NS3)(NSiMe3)] (9), which is converted to [V(NS3)(NH)] (10) by hydrolysis and to [V(NS3)(NCPh3)] (11) by reaction with ClCPh3. Compound 10 is converted into 1 by [NMe4]OH and to [V(NS3)NLi(THF)2] (12) by LiNPri in THF. A further range of imido complexes [V(NS3)(NR4)] (R4 = C6H4Y-4 where Y = H (13a), OMe (13b), Me (13c), Cl (13d), Br (13e), NO2 (13f); R4 = C6H4Y-3, where Y = OMe (13g); Cl (13h); R4 = C6H3Y2-3,4, where Y = Me (13i); Cl (13j); R4 = C6H11 (13k)) has been prepared by reaction of 1 with R4NCO. The precursor complex [V(OS2)O(dipp)] (14) [OS2(2-) = O(CH2CH2S)2(2-)] has been prepared from [VO(OPri)3], Hdipp, and OS2H2. It reacts with NH2NMe2 to give [V(OS2)(NNMe2)(dipp)] (15) and with N3SiMe3 to give [V(OS2)(NSiMe3)(dipp)] (16). A second oxide precursor, formulated as [V(OS2)1.5O] (17), has also been obtained, and it reacts with SiMe3NHNMe2 to give [V(OS2)(NNMe2)(OSiMe3)] (18). The X-ray crystal structures of the complexes 2b, 2c, 4, 6, 7a, 8a, 9, 10, 13d, 14, 15, 16, and 18 have been determined, and the 51V NMR and other spectroscopic parameters of the complexes are discussed in terms of electronic effects.     

双核有机锡(Ⅳ)配合物[Ph_3Sn(CH_3OH)O_2CC_6H_4CO_2(CH_3OH)-SnPh_3]·2CH_3OH和[Ph_3SnS_2CN(CH_2CH_2)_2NCS_2SnPh_3]·2CH_3OH的合成、表征和晶体结构

利用三苯基氯化锡和对苯二甲酸二钠、哌嗪荒酸二钠在甲醇中反应 ,合成了双核有机锡 (Ⅳ )配合物 [Ph3 Sn (CH3 OH)O2 CC6H4 CO2 (CH3 OH)SnPh3 ]·2CH3 OH (1)和 [Ph3 SnS2 CN(CH2 CH2 ) 2 NCS2 SnPh3 ]·2CH3 OH (2 ) .通过元素分析、红外光谱和核磁共振氢谱对其结构进行了表征 .用X射线单晶衍射测定了这两个化合物的晶体结构 .化合物 1为单斜晶系 ,空间群P2 1/n ,a =1.5 199(5 )nm ,b =0 .90 0 0 (3)nm ,c =1.82 0 6 (6 )nm ,β =113.970 (5 )° ,Z =2 ,V =2 .2 75 5(13)nm3 ,Dc=1.413g/cm3 ,μ =1.146mm-1,F(0 0 0 ) =980 ,R1=0 .0 35 3,wR2 =0 .0 6 0 6 .化合物 2为单斜晶系 ,空间群P2 1/c,a =1.5 0 6 6 (5 )nm ,b =1.0 875 (4 )nm ,c =1.35 42 (5 )nm ,β =91.6 14(5 )°,Z =2 ,V =2 .2 178(14)nm3 ,Dc=1.498g/cm3 ,μ =1.35 1mm-1,F(0 0 0 ) =10 0 8,R1=0 .0 40 1,wR2 =0 .1148.在 1和 2的晶体中 ,锡原子呈五配位畸变三角双锥构型 .配合物 1由未配位的甲醇分子通过氢键作用形成二维网状结构     

Theoretical study for the CH3C(O)(CH2)2OH + OH reaction

The mechanisms and the kinetics of the OH radical reaction with 4-hydroxy-2-butanone (4H2B) are investigated theoretically. Five hydrogen-abstraction channels are identified for the title reaction. The first potential energy profile of the title reaction is presented. The rate constants for each reaction channel are evaluated using transition state theory method in the temperature range of 200–1,000 K. Branching ratio of the title reaction is calculated and plotted. It is shown that the “in-plane hydrogen abstraction” from the methoxy end is the dominant channel, and the other hydrogen-abstraction channels play the minor role. The comparison between theoretical and experimental results is discussed. The three-parameter Arrhenius expression for the rate constants is also provided.     

Synthesis of triamidoamine ligands of the type (ArylNHCH(2)CH(2))(3)N and molybdenum and tungsten complexes that contain an [ArylNCH(2)CH(2))(3)N]3- ligand

Aryl bromides react with (H(2)NCH(2)CH(2))(3)N in a reaction catalyzed by Pd(2)(dba)(3) in the presence of BINAP and NaO-t-Bu to give the arylated derivatives (ArylNHCH(2)CH(2))(3)N [Aryl = C(6)H(5) (1a), 4-FC(6)H(4) (1b), 4-t-BuC(6)H(4) (1c), 3,5-Me(2)C(6)H(3) (1d), 3,5-Ph(2)C(6)H(3) (1e), 3,5-(4-t-BuC(6)H(4))(2)C(6)H(3) (1f), 2-MeC(6)H(4) (1g), 2,4,6-Me(3)C(6)H(2) (1h)]. Reactions between (ArNHCH(2)CH(2))(3)N (Ar = C(6)H(5), 4-FC(6)H(4), 3,5-Me(2)C(6)H(3), and 3,5-Ph(2)C(6)H(3)) and Mo(NMe(2))(4) in toluene at 70 degrees C lead to [(ArNHCH(2)CH(2))(3)N]Mo(NMe(2)) complexes in yields ranging from 64 to 96%. Dimethylamido species (Ar = 4-FC(6)H(4), 3,5-Me(2)C(6)H(3)) could be converted into paramagnetic [(ArNHCH(2)CH(2))(3)N]MoCl species by treating them with 2,6-lutidinium chloride in tetrahydrofuran (THF). The "direct reaction" between 1a-f and MoCl(4)(THF)(2) in THF followed by 3 equiv of MeMgCl yielded [(ArNHCH(2)CH(2))(3)N]MoCl species (3a-f) in high yield. If 4 equiv of LiMe instead of MeMgCl are employed in the direct reaction, then [(ArNHCH(2)CH(2))(3)N]MoMe species are formed. Tungsten species, [(ArNHCH(2)CH(2))(3)N]WCl, could be prepared by analogous "direct" methods. Cyclic voltammetric studies reveal that MoCl complexes become more difficult to reduce as the electron donating ability of the [ArylNCH(2)CH(2))(3)N]3- ligand increases, and the reductions become less reversible, consistent with ready loss of chloride from ([(ArNHCH(2)CH(2))(3)N]MoCl)(-). Tungsten complexes are more difficult to reduce, and reductions are irreversible on the CV time scale.     

New superhindered polydentate polyphosphine ligands P(CH2CH2P(t)Bu2)3, PhP(CH2CH2P(t)Bu2)2, P(CH2CH2CH2P(t)Bu2)3, and their ruthenium(II) chloride complexes

The synthesis and characterization of the extremely hindered phosphine ligands, P(CH(2)CH(2)P(t)Bu(2))(3) (P(2)P(3)(tBu), 1), PhP(CH(2)CH(2)P(t)Bu(2))(2) (PhP(2)P(2)(tBu), 2), and P(CH(2)CH(2)CH(2)P(t)Bu(2))(3) (P(3)P(3)(tBu), 3) are reported, along with the synthesis and characterization of ruthenium chloro complexes RuCl(2)(P(2)P(3)(tBu)) (4), RuCl(2)(PhP(2)P(2)(tBu)) (5), and RuCl(2)(P(3)P(3)(tBu)) (6). The bulky P(2)P(3)(tBu) (1) and P(3)P(3)(tBu) (3) ligands are the most sterically encumbered PP(3)-type ligands so far synthesized, and in all cases, only three phosphorus donors are able to bind to the metal center. Complexes RuCl(2)(PhP(2)P(2)(tBu)) (5) and RuCl(2)(P(3)P(3)(tBu)) (6) were characterized by crystallography. Low temperature solution and solid state (31)P{(1)H} NMR were used to demonstrate that the structure of RuCl(2)(P(2)P(3)(tBu)) (4) is probably analogous to that of RuCl(2)(PhP(2)P(2)(tBu)) (5) which had been structurally characterized.     

High-temperature rate constants for CH3OH + Kr --> products, OH + CH3OH --> products, OH + (CH3)(2)CO --> CH2COCH3 + H2O, and OH + CH3 --> CH) + H2O

The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm (corresponding to a total path length of approximately 4.9 m) has been used to study the dissociation of methanol between 1591 and 2865 K. Rate constants for two product channels [CH3OH + Kr --> CH3 + OH + Kr (1) and CH3OH + Kr --> 1CH2 + H2O + Kr (2)] were determined. During the course of the study, it was necessary to determine several other rate constants that contributed to the profile fits. These include OH + CH3OH --> products, OH + (CH3)2CO --> CH2COCH3 + H2O, and OH + CH3 --> 1,3CH2 + H2O. The derived expressions, in units of cm(3) molecule(-1) s(-1), are k(1) = 9.33 x 10(-9) exp(-30857 K/T) for 1591-2287 K, k(2) = 3.27 x 10(-10) exp(-25946 K/T) for 1734-2287 K, kOH+CH3OH = 2.96 x 10-16T1.4434 exp(-57 K/T) for 210-1710 K, k(OH+(CH3)(2)CO) = (7.3 +/- 0.7) x 10(-12) for 1178-1299 K and k(OH+CH3) = (1.3 +/- 0.2) x 10(-11) for 1000-1200 K. With these values along with other well-established rate constants, a mechanism was used to obtain profile fits that agreed with experiment to within <+/-10%. The values obtained for reactions 1 and 2 are compared with earlier determinations and also with new theoretical calculations that are presented in the preceding article in this issue. These new calculations are in good agreement with the present data for both (1) and (2) and also for OH + CH3 --> products.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

Thermal decomposition of bis(dimethylglyoximate) iron(II) complexes containing axial N-heterocyclic ligands

A systematic TG and DTG study of the thermal decomposition of a series of bis(dimethylglyoximate)iron(II) complexes containing axial N-heterocyclic ligands is reported. The decomposition reaction is very exothermic, coinciding with the loss of the axial ligands. The average temperatures of decomposition correlate linearly with the basicity properties of the axial ligands.

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Zusammenfassung Es wird eine systematische TG- und DTA-Untersuchung der thermischen Zersetzung einer Reihe von Bis(dimethylglyoximat)-Komplexe von Eisen(II) mit axialem N-heterocyclischen Liganden beschrieben. Die Zersetzungsreaktion ist sehr exotherm, was mit dem Verlust der axialen Liganden zusammenfällt. Die durchschnittliche Zersetzungstemperatur ist den Basizitäts eigenschaften der axialen Liganden proportional.

     

Kinetic study of the reactions of Cl atoms with CF3CH2CH2OH, CF3CF2CH2OH, CHF2CF2CH2OH, and CF3CHFCF2CH2OH

The reaction kinetics of chlorine atoms with a series of partially fluorinated straight-chain alcohols, CF(3)CH(2)CH(2)OH (1), CF(3)CF(2)CH(2)OH (2), CHF(2)CF(2)CH(2)OH (3), and CF(3)CHFCF(2)CH(2)OH (4), were studied in the gas phase over the temperature range of 273-363 K by using very low-pressure reactor mass spectrometry. The absolute rate coefficients were given by the expressions (in cm(3) molecule(-1) s(-1)): k(1) = (4.42 +/- 0.48) x 10(-11) exp(-255 +/- 20/T); k(1)(303) = (1.90 +/- 0.17) x 10(-11), k(2) = (2.23 +/- 0.31) x 10(-11) exp(-1065 +/- 106/ T); k(2)(303) = (6.78 +/- 0.63) x 10(-13), k(3) = (8.51 +/- 0.62) x 10(-12) exp(-681 +/- 72/T); k(3)(303) = (9.00 +/- 0.82) x 10(-13) and k(4) = (6.18 +/- 0.84) x 10(-12) exp(-736 +/- 42/T); k(4)(303) = (5.36 +/- 0.51) x 10(-13). The quoted 2sigma uncertainties include the systematic errors. All title reactions proceed via a hydrogen atom metathesis mechanism leading to HCl. Moreover, the oxidation of the primarily produced radicals was investigated, and the end products were the corresponding aldehydes (R(F)-CHO; R(F) = -CH(2)CF(3), -CF(2)CF(3), -CF(2)CHF(2), and -CF(2)CHFCF(3)), providing a strong experimental indication that the primary reactions proceed mainly via the abstraction of a methylenic hydrogen adjacent to a hydroxyl group. Finally, the bond strengths and ionization potentials for the title compounds were determined by density functional theory calculations, which also suggest that the alpha-methylenic hydrogen is mainly under abstraction by Cl atoms. The correlation of room-temperature rate coefficients with ionization potentials for a set of 27 molecules, comprising fluorinated C2-C5 ethers and C2-C4 alcohols, is good with an average deviation of a factor of 2, and is given by the expression log(k) (in cm(3) molecule(-1) s(-1)) = (5.8 +/- 1.4) - (1.56 +/- 0.13) x (ionization potential (in eV)).     

Parity‐Violating Potentials for the Torsional Motion of Methanol (CH3OH) and Its Isotopomers (CD3OH, 13CH3OH,CH3OD,CH3OT,CHD2OH,and CHDTOH)

We present calculations on the parity‐conserving and the parity‐violating potentials in several MeOH isotopomers for the torsional motion by the newly developed methods of electroweak quantum chemistry from our group. The absolute magnitudes of the parity‐violating potentials for MeOH are small compared to H₂O₂ and C₂H₄, but similar to C₂H₆, which is explained by the high (threefold) symmetry of the torsional top in MeOH and C₂H₆. ‘Chiral’ and ‘achiral’ isotopic substitutions in MeOH lead to small changes only, but vibrational averaging is discussed to be important in all these cases. Simple isotopic sum rules are derived to explain and predict the relationships between parity‐violating potentials in various conformations and configurations of the several isotopomers investigated. The parity‐violating energy difference Δ_pvE=E_pv(R)?E_pv(S) between the enantiomers of chiral CHDTOH, first synthesized by Arigoni and co‐workers, is for two conformers ca. ?3.66?10^?17 and for the third one +7.32?10^?17 hc cm^?1. Thus, for Δ_pvE, the conformation is more important than the configuration (at the equilibrium geometries, without vibrational averaging). Averaging over torsional tunneling may lead to further cancellation and even smaller values.     

配合物Ni(DPBP-SAH)2·2CH3CH2OH的合成和晶体结构

A nickel(Ⅱ) complex Ni(DPBP-SAH)₂·2CH₃CH₂OH, (DPBP-SAH=N-(1,3-diphenyl-4-benzylidene-5-pyrazolone)-salicylidene hydrazone), has been synthesized and characterized by elemental analyses, IR spectra and single crystal X-ray diffraction. It belongs to monoclinic, space group C2/c with a=2.737 9(4) nm, b=1.249 2(2) nm, c=1.760 8(2) nm, β=120.212(9)°, M_r=1 065.84, V=5.204(1) nm³, Z=4. The X-ray diffraction reveals that the nickel(Ⅱ) ion in the title complex is in a slightly distorted octahedral arrangement of the ON donor atoms of two DPBP-SAH and two O-donor atoms in ethanol. CCDC: 249394.     

Computational study of the reaction of CH2(X3B1) with CH3OH

The reaction of triplet methylene with methanol is a key process in alcohol combustion but surprisingly this reaction has never been studied. The reaction mechanism is investigated by using various high-level ab initio methods, including the complete basis set extrapolation (CBS-QB3 and CBS-APNO), the latest Gaussian-n composite method (G4), and the Weizmann-1 method (W1U). A total of five product channels and six transition states are found. The dominant mechanism is direct hydrogen abstraction, and the major product channel is CH(3) + CH(3)O, involving a weak prereactive complex and a 7.4 kcal/mol barrier. The other hydrogen abstraction channel, CH(3) + CH(2)OH, is less important even though it is more exothermic and involves a similar barrier height. The rate coefficients are predicted in the temperature range 200-3000 K. The tunneling effect and the hindered internal rotational freedoms play a key role in the reaction. Moreover, the reaction shows significant kinetic isotope effect.     

Thermal analysis of some chromium(III) complexes with dicarboxylic ligands

The solid chromium(III) complexes with a series of dicarboxylic ligands were prepared as potassium salts and examined by TG, DTG and DSC. The results are discussed in terms of basicity by arranging the ligands in proper series.     

Oxorhenium(V) complexes containing bidentate N,O-donor ligands of the pyridyl type

The reaction of equimolar quantities of trans-[ReOCl₃(PPh₃)₂] and 8-hydroxyquinoline (Hhqn) in benzene led to the isolation of the six-coordinate complex [ReOCl₂(hqn)(PPh₃)] (1). With 2-pyridine-ethanol (Hhep) the compound [ReOCl₂(hep)(PPh₃)] (2) was obtained. Both hqn and hep ligands act as monoanionic bidentate N,O-donor chelates. Although the two complexes are very similar, there are some significant differences in certain bond distances and angles in them. Both complexes contain the nearly linear trans O=Re–O axis, with this angle equal to 160.9(2)° and 167.8(1)° in 1 and 2, respectively.     

NMR investigations on Stannabicycloundecanes of the type RSn(CH2CH2CH2)3N

The ¹H, ¹³C, and ¹¹⁹Sn NMR data of seven stannabicycloundecanes of the type RSn(CH₂CH₂CH₂)₃N (1, R = Cl; 2 , R = Br; 3 , R = I; 4 , R = OH; 5 , R = SPh; 6 , R = Me; 7 , R = Sn(CH₂CH₂CH₂)₃N) are reported. From ¹H NMR coalescence data at low temperature the free activation enthalpies for the racemisation of the bicyclo[3.3.3]skeleton were estimated to be 37 ± 1 kJ/mol. They are independent of the substituent R. However, it decreases when the tin atom is replaced by silicon for R = Me.     

Theoretical investigation on mechanism for OH-initiated oxidation of CH2=C(CH3)CH2OH

The mechanism of the gas-phase reaction OH with CH₂=C(CH₃)CH₂OH (2-methyl-2-propen-1-ol) has been elucidated using high-level ab initio method, i.e., CCSD(T)/6-311++g(d,p)//MP2(full)/6-311++g(d,p). Various possible H-abstraction and addition–elimination pathways are identified. The calculations indicate that the addition–elimination mechanism dominates the OH+MPO221 reaction. The addition reactions between OH radicals and CH₂=C(CH₃)CH₂OH begin with the barrierless formation of a pre-reactive complex in the entrance channel, and subsequently the CH₂(OH)C(CH₃)CH₂OH (IM1) and the CH₂C(OH)(CH₃)CH₂OH (IM2) are formed by OH radicals’ electrophilic additions to the double bond. IM1 can easily rearrange to IM2 via a 1,2-OH migration. Subsequently, rearrangement of IM2 to form (CH₃)₂C(OH)CH₂O (IM11) followed by dissociation to HCHO + (CH₃)₂COH (P21) is the most favorable pathway. The decomposition of IM2 to CH₂OH + CH₂=C(OH)CH₃ (P16) is the secondary pathway. The other pathways are not expected to play any important role in forming final products.