Thermolysis of tert-butyl phenylperacetates: delicate control of the rates through contributions from translational and rotational entropy

The first-order rate constants (k(Y)) at several temperatures in CDCl(3) were measured for thermal decompositions of YC(6)H(4)CH(2)CO(3)C(CH(3))(3) with Y being p-OCH(3), p-OPh, p-CH(3), p-Ph, p-H, p-Cl, m-Cl, and p-NO(2). The relative rates (k(Y)/k(H)) exhibit excellent rho(+)/sigma(+) Hammett correlations with rho(+) < 0, indicating a polar TS. Activation parameters (DeltaH()(Y) and DeltaS()(Y)) and their differential terms (DeltaDeltaH()(Y)(-)(H) and DeltaDeltaS()(Y)(-)(H)) were obtained from the Eyring plot. Differential activation terms (DeltaDeltaH()(Y)(-)(H) and DeltaDeltaS()(Y)(-)(H)) disclose an isokinetic relation with p-CH(3), p-Ph, p-H, p-Cl, and m-Cl (isokinetic temp, 230 K). However, p-OCH(3), and p-OPh show negative deviations, and a positive deviation occurs with p-NO(2). Plot of DeltaDeltaH()(Y)(-)(H) vs sigma(+) exhibits a good linear relation (r = 0.95) with a slope (alpha(1) = -3.34). A better linear correlation (r = 0.97) and steeper slope (alpha(2) = -5.22) were observed for TDeltaDeltaS()(Y)(-)(H) vs sigma(+). Negatively larger slope (alpha(2) = -5.22) may point to entropy control of rates. Differential activation parameters (DeltaDeltaH()(Y)(-)(H) and DeltaDeltaS()(Y)(-)(H)) reflect variations of activation process. Differential activation entropies (DeltaDeltaS()(Y)(-)(H)) are discussed in terms of contributions of translational and rotational entropies. Similar deviation behaviors of p-OCH(3), p-OPh, and p-NO(2) were again observed for the both plots. p-NO(2) can strongly destabilize the cationic site of the polar TS but serves an eminent spin delocalizer for the homolytic TS.     

Electrospray ionization mass spectrometry of tribenzyltin substituted-phenoxyacetate compounds

Hydrolysis products of organotin compounds RC(6)H(4)OCH(2)COOSn(CH(2)ph)(3) (R = o-NO(2), 1; m-NO(2), 2; p-NO(2), 3; o-CH(3), 4; o-OCH(3), 5; o-Cl, 6; o-Br, 7) and RC(6)H(3)OCH(2)COOSn(CH(2)ph)(3) (R = o,o-2CH(3), 8, o-OCH(3), p-CHO, 9; o,p-2Cl, 10), produced in aqueous acetonitrile solution, have been investigated by electrospray mass spectrometry (MS) and MS(n) techniques. The complexes [Y(2)SnXR'](-), [Y(3)SnXR'](-), [Y(3)SnX(2)R'](-), [Y(2)SnX(3)R'](-), and fragment ions of [Y(3)SnR'](-), plus abundant RC(6)H(4)(or RC(6)H(3))OCH(2)COO(-) and RC(6)H(4)(or RC(6)H(3))O(-) ions are observed in negative mode, whereas the protonated molecular ion [M + H](+), complexes [Y(2)SnXR'](+), [Y(3)SnXR'](+), [Y(2)SnX(2)R'](+), [Y(3)SnX(2)R'](+), [Y(2)SnX(3)R'](+), [Y(3)SnX(3)R'](+), as well as [YSnXR'](+), [M - CH(2)ph](+), XSn(+), (phCH(2))(3)Sn(+), phCH(2)Sn(+) (Y = &bond;CH(2)ph, X = &bond;OOCCH(2)OC(6)H(4)R(or C(6)H(3)R)) are detected in the positive mode. Water adduct ions are seen in both modes. The assignments are facilitated by agreement between observed and calculated isotopic patterns and tandem mass spectrometry studies.     

氟化钾催化取代酚与硅氢化合物的反应

本文研究了氟化物存在下, 硅氢化合物与酚类反应的规律性。选择了在KF存在下, 以DMF为溶剂, 含有不同邻, 间, 对位取代酚作为反应底物与多种含氢硅烷进行了一系列反应, 在反应活性上获得了具有一定规律性的结果, 同时得到了21个末见报道的新芳氢基有机硅化合物, 所得化合物均经元素分析, IR和1H NMR测定, 确定了结构。     

W(CO)6-catalyzed oxidative carbonylation of primary amines to N,N'-disubstituted ureas in single or biphasic solvent systems. Optimization and functional group compatibility studies

Primary amines undergo carbonylation to N,N'-disubstituted ureas using W(CO)6 as the catalyst, I2 as the oxidant, and CO as the carbonyl source. Preparation of various N,N'-disubstituted ureas from aliphatic primary amines, RNH2 (R = n-Pr, n-Bu, i-Pr, sec-Bu, or t-Bu), was achieved in good to excellent yields. Studies of functional group compatibility using a series of substituted benzylamines demonstrated broad tolerance of functionality during the carbonylation reaction. Preparation of various N,N'-disubstituted ureas from substituted benzylamines, R-C6H4CH2NH2 (R = H, p-OCH3, p-CO2H, p-CO2Et, p-CH2OH, p-SCH3, p-vinyl, p-Cl, p-Br, m-I, p-NH2, p-NO2, or p-CN), was achieved in good yields. For many substituted benzylamines, yields of ureas were higher when a two-phase CH2Cl2/H2O solvent system was used.     

Intermediates of halogen addition to phenylethynes and protonation of phenylethynyl halides. Open halovinyl cations, bridged halonium, or phenyl-bridged ions: a substituent effect study by DFT and GIAO-DFT

Formation of alpha-phenyl-beta-halovinyl cation, beta-phenyl-alpha-halovinyl cation, as well as the halogen-bridged and the spirocyclic phenyl-bridged cations as intermediates of protonation of phenylethynyl halides or by halogen addition to phenylethynes was evaluated by DFT at B3LYP/6-31+G(d) and, for comparison in representative cases, by B3LYP/6-311++G(d,p). Relative stabilities of the resulting minima were gauged as a function of substituents on the phenyl group with p-OH, p-OMe, p-H, p-CF3, p-CN, and p-NO2 and with p-OMeH+, p-NO2H+, and p-N2+. In the majority of cases, the alpha-aryl-beta-halovinyl cations were identified as the most likely intermediates, irrespective of X and for most R groups. For R = p-N2+ (with X = Br and Cl), R = CNH+ (with X = Cl), and R = MeOH+ (with X = Br), the corresponding beta-aryl-alpha-halovinyl cations become more stable than alpha-aryl-beta-halovinyl cations (but in most cases with a relatively small stability difference). Whereas competitive formation of the spirocyclic aryl bridged cations via this route appears remote, with R = N2+ and R = NO2H+ as substituents (with X = Br), cyclic halonium ions could intervene, since their relative stabilities are within approximately 4 kcal/mol of the lowest energy vinyl cations. Geometrical features, GIAO NMR chemical shifts, and NPA-derived charges were used to gain insight into the structural/electronic features in the resulting mono and dications. The study provides a basis for stable ion and solvolytic/kinetic studies on a series of substituted phenylethynyl halides that are being synthesized.     

Facile allylic C-H bond activation on the bridging disulfide ligand in the Ru(III) dinuclear complex having a conjugated RuSSRu core

Treatment of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)(mu-S(2))](CF(3)SO(3))(4) (1), which is prepared by the reaction of [[RuCl(P(OCH(3))(3))(2)](2)(mu-S(2))(mu-Cl)(2)] (2) with 4 equiv of AgCF(3)SO(3), with terminal alkenes such as 1-pentene, allyl ethyl ether, allyl phenyl ether, 1,4-hexadiene, and 3-methyl-1-butene, resulted in the formation of complexes carrying a C(3)S(2) five-membered ring, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)CH(2)CR(1)R(2)S]](CF(3)SO(3))(4) (3, R(1) = CH(2)CH(3), R(2) = H, 40%; 4, R(1) = OCH(2)CH(3), R(2) = H, 60%; 5, R(1) = OC(6)H(5), R(2) = H, 73%; 6, R(1) = CH=CHCH(3), R(2) = H, 48%; 7, R(1) = R(2) = CH(3), 40%). Reaction of 1 with methylenecycloalkanes was found to give several different types of products, depending on the ring size of the substrates. A trace of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(CH(2)CH(2))CH(CH(3))S]](CF(3)SO(3))(4) (9) having a C(2)S(2) four-membered ring to bridge the two Ru atoms was obtained by the reaction of 1 with methylenecyclobutane, whereas the reaction with methylenecyclohexane gave [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-S(CH(2)(C=CHCH(2)CH(2)CH(2)CH(2))S)](CF(3)SO(3))(3) (10) in 69% yield via C-S bond formation and elimination of a proton. Throughout these reactions with alkenes giving a variety of products, the activation of the allylic C-H bond is always the essential and initial key step.     

C-H cleavage and double alkyl additions to the disulfido ligand in dicyanido-bridged Ru2S2 complexes

Novel dicyanido-bridged dicationic RuIIISSRuIII complexes [{Ru(P(OCH3)3)2}2(mu-S2)(mu-X)2{mu-m-C6H4(CH2CN)2}](CF3SO3)2 (4, X=Cl, Br) were synthesized by the abstraction of the two terminal halide ions of [{RuX(P(OCH3)3)2}2(mu-S2)(mu-X)2] (1, X=Cl, Br) followed by treatment with m-xylylenedicyanide. 4 reacted with 2,3-dimethylbutadiene to give the C4S2 ring-bridged complex [{Ru(P(OCH3)3)2}2{mu-SCH2C(CH3)=C(CH3)CH2S}(mu-X)2{mu-m-C6H4(CH2CN)2}](CF3SO3)2 (6, X=Cl, Br). In addition, 4 reacted with 1-alkenes in CH3OH to give alkenyl disulfide complexes [{Ru(P(OCH3)3)2}2{mu-SS(CH2C=CHR)}(mu-Cl)2{mu-m-C6H4(CH2CN)2}](CF3SO3) (7: R=CH2CH3, 9: R=CH2CH2CH3) and alkenyl methyl disulfide complexes [{Ru(P(OCH3)3)2}2{mu-S(CH3)S(CH2C=HR)}(mu-Cl)2{mu-m-C6H4(CH2CN)2}](CF3SO3)2 (8: R=CH2CH3, 10: R=CH2CH2CH3) via the activation of an allylic C-H bond followed by the elimination of H+ or condensation with CH3OH. Additionally, the reaction of 4 with 3-penten-1-ol gave [{Ru(P(OCH3)3)2}2{mu-SS(CH2C=CHCH2OH)}(mu-Cl)2{mu-m-C6H4(CH2CN)2}](CF3SO3) (11) via the elimination of H+ and [{Ru(P(OCH3)3)2}2(mu-SCH2CH=CHCH2S)(mu-Cl)2{mu-m-C6H4(CH2CN)2}](CF3SO3)2 (12) via the intramolecular elimination of a H2O molecule. 12 was exclusively obtained from the reaction of 4 with 4-bromo-1-butene.     

A computational study of the lowest singlet and triplet states of neutral and dianionic 1,2-substituted icosahedral and octahedral o-carboranes

This work introduces a calibrated B3LYP/6-31G(d) study on the electronic structure of singlet and triplet neutral species of 1,2-substituted icosahedral 1,2-R(2)-1,2-C(2)B(10)H(10) and octahedral 1,2-R(2)-1,2-C(2)B(4)H(4) molecules with R = {H, OH, SH, NH(2), PH(2), CH(3), SiH(3)} and their respective dianions formed by proton removal on each R group. A variety of small adiabatic singlet-triplet gaps DeltaE(ST) are obtained from these systems ranging from 2.93 eV (R = NH(2)) 相似文献   

Conformational analysis and assignments of relative stereocenter configurations in fluoroalkyl-iridium complexes using 19F[1H] HOESY experiments. Comparison with solid-state X-ray structural results

Solution conformations about the metal-carbon bond of the secondary fluoroalkyl ligands in iridium complexes [IrCp(PMe(3))(R(F))X] [Cp* = C(5)Me(5); R(F) = CF(CF(3))(2), X = I (1), CH(3) (2); R(F) = CF(CF(3))(CF(2)CF(3)), X = I (4), CH(3) (5)] have been determined using (19)F[(1)H] HOESY techniques. The molecules adopt the staggered conformation with the tertiary fluorine in the more hindered sector between the PMe(3) and X ligands, with CF(3) (and CF(2)CF(3)) substituents lying in the less hindered regions between PMe(3) and Cp or X and Cp. In molecules containing the CF(CF(3))(2) ligand, these conformations are identical to those adopted in the solid state. For compound 4, containing the CF(CF(3))(CF(2)CF(3)) ligand, two diastereomers are observed in solution. Solution conformations and relative stereocenter configuration assignments have been obtained using (19)F[(1)H] HOESY and correlated with the X-ray structure for the major diastereomer of 4, which has the (S(Ir), S(C)) or (R(Ir), R(C)) configuration. Relative stereocenter configurations of analogue 5, for which no suitable crystals could be obtained, were assigned using (19)F[(1)H] HOESY and proved to be different from 4, with 5 preferring the (S(Ir), R(C)) or (R(Ir), S(C)) configuration.     

Syntheses of ketonated disulfide-bridged diruthenium complexes via C-H bond activation and C-S bond formation

The alpha-C-H bonds of 3-methyl-2-butanone, 3-pentanone, and 2-methyl-3-pentanone were activated on the sulfur center of the disulfide-bridged ruthenium dinuclear complex [(RuCl(P(OCH3)3)2)2(mu-S2)(mu-Cl)2] (1) in the presence of AgX (X = PF6, SbF6) with concomitant formation of C-S bonds to give the corresponding ketonated complexes [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SSCHR1COR2)(Ru(CH3CN)3(P(OCH3)3)2)]X3 ([5](PF6)3, R1 = H, R2 = CH(CH3)2, X = PF6; [6](PF6)3, R1 = CH3, R2 = CH2CH3, X = PF6; [7](SbF6)3, R1 = CH3, R2 = CH(CH3)2, X = SbF6). For unsymmetric ketones, the primary or the secondary carbon of the alpha-C-H bond, rather than the tertiary carbon, is preferentially bound to one of the two bridging sulfur atoms. The alpha-C-H bond of the cyclic ketone cyclohexanone was cleaved to give the complex [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SS-1- cyclohexanon-2-yl)(Ru(CH3CN)3(P(OCH3)3)2)](SbF6)3 ([8](SbF6)3). And the reactions of acetophenone and p-methoxyacetophenone, respectively, with the chloride-free complex [(Ru(CH3CN)3(P(OCH3)3)2)2(mu-S2)]4+ (3) gave [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SSCH2COAr)(Ru(CH3CN)3(P(OCH3)3)2)](CF3SO3)3 ([9](CF3SO3)3, Ar = Ph; [10](CF3SO3)3, Ar = p-CH3OC6H4). The relative reactivities of a primary and a secondary C-H bond were clearly observed in the reaction of butanone with complex 3, which gave a mixture of two complexes, i.e., [(Ru(CH3CN)2(P(OCH3)3)20(mu-SSCH2COCH2CH3)(Ru(CH3CN)3(P(OCH3)3)2)](CF3SO3)3 ([11](CF3SO3)3) and [(Ru(CH3CN)2(P(OCH3)3)2)(mu-SSCHCH3COCH3)(Ru(CH3CN)3(P(OCH3)2)](CF3SO3)3 ([12](CF3SO3)3), in a molar ratio of 1:1.8. Complex 12 was converted to 11 at room temperature if the reaction time was prolonged. The relative reactivities of the alpha-C-H bonds of the ketones were deduced to be in the order 2 degrees > 1 degree > 3 degrees, on the basis of the consideration of contributions from both electronic and steric effects. Additionally, the C-S bonds in the ketonated complexes were found to be cleaved easily by protonation at room temperature. The mechanism for the formation of the ketonated disulfide-bridged ruthenium dinuclear complexes is as follows: initial coordination of the oxygen atom of the carbonyl group to the ruthenium center, followed by addition of an alpha-C-H bond to the disulfide bridging ligand, having S=S double-bond character, to form a C-S-S-H moiety, and finally completion of the reaction by deprotonation of the S-H bond.     

Substituent effects on the ring-chain tautomerism of some 1,3-oxazolidine derivatives

The 14 and 70 eV electron ionization mass spectra of five sets (R1 = Me, Et, i-Pr, t-Bu and Ph) of seven 2-aryl-4-R1-substituted (Ar = C6H4X; X = p-NO2, m-Br, p-Cl, H, p-Me, p-OMe and p-NMe2) (1-5) and of seven 2-aryl-5-phenyl-substituted 1,3-oxazolidines (6; for Ar, see above) were recorded to study their ring-chain equilibria in the gas phase. These equilibria were also studied by 1H NMR spectroscopy in CDCl3 for compounds 5 and 6. A few 2,4- and 2,5-dimethyl-2-aryl derivatives (7, 8: Ar = C6H4X; X = m-Br, H and p-OMe) were studied both in CDCl3 and in the gas phase. The main characteristics of the ring-chain equilibria expressed by the variable SigmaRA% of the ring and of the chain form proved to be a strong dependence on the nature of the substituents on C-2 and C-4. The results in the gas phase are compared with those in CDCl3.     

Linear Free Energy Relationships in Dinuclear Compounds. 2. Inductive Redox Tuning via Remote Substituents in Quadruply Bonded Dimolybdenum Compounds

Syntheses and characterizations are reported for dimolybdenum(II) compounds supported by the diarylformamidinate (ArNC(H)NAr(-)) ligand, where Ar is XC(6)H(4)(-), with X as p-OMe (1), H (2), m-OMe (3), p-Cl (4), m-Cl (5), m-CF(3) (6), p-COMe (7), p-CF(3) (8), or Ar is 3,4-Cl(2)C(6)H(3)(-) (9) or 3,5-Cl(2)C(6)H(3)(-) (10). The (quasi)reversible oxidation potentials measured for the Mo(2)(5+)/Mo(2)(4+) couple were found to correlate with the Hammett constant (sigma(X)) of the aryl substituents according to the following equation: DeltaE(1/2) = E(1/2)(X) - E(1/2)(H) = 87(8sigma(X)) mV. Molecular structure determinations of compounds 1, 2, 5, and 10 revealed an invariant core geometry around the Mo(2) center, with statistically identical Mo-Mo quadruple bond lengths of 2.0964(5), 2.0949[8], 2.0958(6), and 2.0965(5) ?, respectively. Magnetic anisotropies for compounds 1-10 estimated on the basis of (1)H NMR data were similar and unrelated to sigma(X). Similarity in UV-vis spectra was also found within the series, which, in conjunction with the features of both molecular structures and (1)H NMR spectra, was interpreted as the existence of a constant upper valence structure across the series. Results of Fenske-Hall calculations performed for several model compounds paralleled the experimental observations.     

Reactions of phosphine oxides with bromophosphoranimines; synthesis and unusual rearrangements of O-donor stabilized phosphoranimine cations

Reaction of phosphine oxides R(3)P═O [R = Me (1a), Et (1c), (i)Pr (1d) and Ph (1e)], with the bromophosphoranimines BrPR'R'P═NSiMe(3) [R' = R' = Me (2a); R' = Me, R' = Ph (2b); R' = R' = OCH(2)CF(3) (2c)] in the presence or absence of AgOTf (OTf = CF(3)SO(3)) resulted in a rearrangement reaction to give the salts [R(3)P═N═PR'R'O-SiMe(3)]X (X = Br or OTf) ([4]X). Reaction of phosphine oxide 1a with the phosphoranimine BrPMe(2)═NSiPh(3) (5) with a sterically encumbered silyl group also resulted in the analogous rearranged product [Me(3)P═N═PMe(2)O-SiPh(3)]X ([8]X) but at a significantly slower rate. In contrast, the direct reaction of the bulky tert-butyl substituted phosphine oxide, (t)Bu(3)P═O (1b) with 2a or 2c in the presence of AgOTf yielded the phosphine oxide-stabilized phosphoranimine cations [(t)Bu(3)P═O·PR'(2)═NSiMe(3)](+) ([3](+), R' = Me (d), OCH(2)CF(3) (e)). A mechanism is proposed for the unexpected formation of [4](+) in which the formation of the donor-stabilized adduct [3](+) occurs as the first step.     

Regioselective Substitution Reactions of Sulfur(VI)-Nitrogen-Phosphorus Rings: Reactions of the Halogenated Cyclic Thionylphosphazenes [NSOX(NPCl(2))(2)] (X = Cl or F) with Oxygen-Based Nucleophiles

The reactions of the cyclic thionylphosphazenes [NSOX(NPCl(2))(2)] (1, X = Cl; 2, X = F) with three oxygen-based nucleophiles of increasing basicity, sodium phenoxide (NaOPh), sodium trifluoroethoxide (NaOCH(2)CF(3)), and sodium butoxide (NaOBu) have been studied. The reaction of 1 and 2 with 4 equiv of NaOPh at 25 degrees C yielded the regioselectively tetrasubstituted species [NSOX{NP(OPh)(2)}(2)] (5d, X = Cl; 6d, X = F). Further reaction of 5d with an additional 2 equiv of NaOPh over several days or at elevated temperatures gave the fully substituted compound [NSO(OPh){NP(OPh)(2)}(2)] (5e), whereas 6d did not react further. The reaction of 1 and 2 with 5 equiv of NaOCH(2)CF(3) yielded in both cases [NSO(OCH(2)CF(3)){NP(OCH(2)CF(3))(2)}(2)] (7e), and similarly reaction with 5 equiv of NaOBu yielded [NSO(OBu){NP(OBu)(2)}(2)] (9e). In all cases, the reactions were monitored by (31)P NMR and (where applicable) (19)F NMR and were found to involve complete substitution at phosphorus via a predominantly vicinal pathway, followed by substitution at sulfur. Substitutional control of the reactions of NaOPh, NaOBu, with 1 and 2 was found to conform to the following general order of reactivity, PCl(2) > PCl(OR) > SOX (X = Cl, F). Although the reaction with NaOCH(2)CF(3) followed the same order of reactivity, a significant enhancement of reaction rate was detected with each equivalent of trifluoroethoxide added. Reaction of 7e with excess NaOCH(2)CF(3) led to elimination of (CF(3)CH(2))(2)O and the formation of the salts Na[NSO(OCH(2)CF(3))NP(OCH(2)CF(3))(2)NP(OCH(2)CF(3))O] (11) and Na[NS(O)O{NP(OCH(2)CF(3))(2)}(2)] (12). Crystals of 6d are triclinic, space group P&onemacr;, with a = 9.789(3) ?, b = 11.393(4) ?, c = 12.079(5) ?, alpha = 107.40(3) degrees, beta = 91.23(3) degrees, gamma = 93.18(3), V = 1283.6(8) ?(3), and Z = 2. Crystals of 5e are monoclinic, space group C2/c, with a = 32.457(3) ?, b = 10.747(1) ?, c = 18.294(2) ?, beta = 110.37(1) degrees, V = 5982.4(9) ?(3), and Z = 8.     

Dehydration reaction of hydroxyl substituted alkenes and alkynes on the Ru(2)S(2) complex

A variety of inter- and intramolecular dehydration was found in the reactions of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)(mu-S(2))](CF(3)SO(3))(4) (1) with hydroxyl substituted alkenes and alkynes. Treatment of 1 with allyl alcohol gave a C(3)S(2) five-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)CH(2)CH(OCH(2)CH=CH(2))S]](CF(3)SO(3))(4) (2), via C-S bond formation after C-H bond activation and intermolecular dehydration. On the other hand, intramolecular dehydration was observed in the reaction of 1 with 3-buten-1-ol giving a C(4)S(2) six-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2) [mu-SCH(2)CH=CHCH(2)S]](CF(3)SO(3))(4) (3). Complex 1 reacts with 2-propyn-1-ol or 2-butyn-1-ol to give homocoupling products, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCR=CHCH(OCH(2)C triple bond CR)S]](CF(3)SO(3))(4) (4: R = H, 5: R = CH(3)), via intermolecular dehydration. In the reaction with 2-propyn-1-ol, the intermediate complex having a hydroxyl group, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OH)S]](CF(3)SO(3))(4) (6), was isolated, which further reacted with 2-propyn-1-ol and 2-butyn-1-ol to give 4 and a cross-coupling product, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OCH(2)C triple bond CCH(3))S]](CF(3)SO(3))(4) (7), respectively. The reaction of 1 with diols, (HO)CHRC triple bond CCHR(OH), gave furyl complexes, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SSC=CROCR=CH]](CF(3)SO(3))(3) (8: R = H, 9: R = CH(3)) via intramolecular elimination of a H(2)O molecule and a H(+). Even though (HO)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OH) does not have any propargylic C-H bond, it also reacts with 1 to give [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)C(=CH(2))C(=C=C(CH(3))(2))]S](CF(3)SO(3))(4) (10). In addition, the reaction of 1 with (CH(3)O)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OCH(3)) gives [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(2)][mu-S=C(C(CH(3))(2)OCH(3))C=CC(CH(3))CH(2)S][Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)]](CF(3)SO(3))(4) (11), in which one molecule of CH(3)OH is eliminated, and the S-S bond is cleaved.     

Dicopper(II) complexes of H-BPMP-type ligands: pH-induced changes of redox, spectroscopic ((19)F NMR studies of fluorinated complexes), structural properties, and catecholase activities

Substitution of the methyl group from the H-BPMP (HL(CH)3) ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) by electron withdrawing (F or CF(3)) or electron donating (OCH(3)) groups afforded a series of dinucleating ligand (HL(OCH)3, HL(F), HL(CF)3), allowing one to understand the changes in the properties of the corresponding dicopper complexes. Dinuclear Cu(II) complexes have been synthesized and characterized by spectroscopic (UV-vis, EPR, (1)H NMR) as well as electrochemical techniques and, in some cases, by single-crystal X-ray diffraction: [Cu(2)(L(OCH)3)(muOH)][(ClO(4))(2)].C(4)H(8)O, [Cu(2)(L(F))(muOH)][(ClO(4))(2)], [Cu(2)(L(F))(H(2)O)(2)][(ClO(4))(3)].C(3)D(6)O, and [Cu(2)(L(CF)3)(H(2)O)(2)][(ClO(4))(3)].4H(2)O. Significant differences are observed for the Cu-Cu distance in the two mu-hydroxo complexes (2.980 A (R = OCH(3)) and 2.967 A (R = F)) compared to the two bis aqua complexes (4.084 A (R = F) and 4.222 A (R = CF(3))). The mu-hydroxo and bis aqua complexes are reversibly interconverted upon acid/base titration. In basic medium, new species are reversibly formed and identified as the bis hydroxo complexes except for the complex from HL(CF)3 which is irreversibly transformed near pH = 10. pH-driven interconversions have been studied by UV-vis, EPR, and (1)H NMR, and the corresponding pK are determinated. In addition, with the fluorinated complexes, the changes in the coordination sphere around the copper centers and in their redox states are evidenced by the fluorine chemical shift changes ((19)F NMR). For all the complexes described here, investigations of the catechol oxidase activities (oxidation of 3,5-di-tert-butylcatechol to the corresponding quinone) are of interest in modeling the catecholase enzyme active site and in understanding aspects of structure/reactivity. These studies show the pH-dependence for the catalytic abilities of the complexes, related with changes in the coordination sphere of the metal centers: only the mu-hydroxo complexes from HL(CH)3, HL(F), and HL(OCH)3 exhibit a catecholase activity. Modification on R-substituent induces a drastic effect on the catecholase activity: the presence of an electron donating group on the ligand increases this activity; the reverse effect is observed with an electron withdrawing group.     

Distinct electronic effects on reductive eliminations of symmetrical and unsymmetrical bis-aryl platinum complexes

Symmetrical bis-aryl platinum complexes (DPPF)Pt(C(6)H(4)-4-R)(2) (R = NMe(2), OMe, CH(3), H, Cl, CF(3)) and electronically unsymmetrical bis-aryl platinum complexes (DPPF)Pt(C(6)H(4)-4-R)(C(6)H(4)-4-X) (R = CH(3), X = NMe(2), OMe, H, Cl, F, CF(3); R = OMe, X = NMe(2), H, Cl, F, CF(3); R = CF(3), X = H, Cl, NMe(2); and R = NMe(2), X = H, Cl) were prepared, and the rates of reductive elimination of these complexes in the presence of excess PPh(3) are reported. The platinum complexes reductively eliminated biaryl compounds in quantitative yields with first-order rate constants that were independent of the concentration of PPh(3). Plots of Log(k(obs)/k(obs(H))) vs Hammett substituent constants (sigma) of the para substituents R and X showed that the rates of reductive elimination reactions depended on two different electronic properties. The reductive elimination from symmetrical bis-aryl platinum complexes occurred faster from complexes with more electron-donating para substituents R. However, reductive elimination from a series of electronically unsymmetrical bis-aryl complexes was not faster from complexes with the more electron-donating substituents. Instead, reductive elimination was faster from complexes with a larger difference in the electronic properties of the substituents on the two platinum-bound aryl groups. The two electronic effects can complement or cancel each other. Thus, this combination of electronic effects gives rise to complex, but now more interpretable, free energy relationships for reductive elimination.     

Synthesis,structure, and reactivity of some N-phosphorylphosphoranimines

A large series of new N-phosphorylphosphoranimines that bear potentially reactive functional groups on both phosphorus centers were prepared by silicon-nitrogen bond cleavage reactions of N-silylphosphoranimines. Thus, treatment of the N-silylphosphoranimines, Me(3)SiN=P(Me)(R)X (R = Me, Ph; X = OCH(2)CF(3) and R = Me, X = OPh), with phosphoryl chlorides, RP(=O)Cl(2) (R' = Cl, Me, Ph), readily afforded the corresponding N-phosphoryl derivatives, R'P(=O)(Cl)-N=P(Me)(R)X, in high yields. Subsequent reaction with 1 or 2 equiv of the silylamine, Me(3)SiNMe(2), resulted in ligand exchange at the phosphoryl (P=O) group to give the P-dimethylamino analogues, R'P(=O)(NMe(2))N=P(Me)(R)X (R' = Cl, NMe(2), Me, Ph; R = Me, Ph; X = OCH(2)CF(3), OPh). These new N-phosphorylphosphoranimines (and one thiophosphoryl analogue) were obtained as thermally stable, distillable liquids and were characterized by NMR ((1)H, (13)C, and (31)P) spectroscopy and elemental analysis. One member of the series, Cl(2)P(=O)N=P(Me)(Ph)OCH(2)CF(3) (4), was also studied by single-crystal X-ray diffraction which revealed that the formal P(O)-N single bond [1.55(1) A] is shorter than the formal N=PR(2)X double bond [1.60(1) A]. Such structural features are compared to those of similar compounds and discussed in relationship to the unexpected thermolysis pathways observed for these N-phosphorylphosphoranimines, none of which produced poly(phosphazenes).     

The D Parameter (EPR Zero-Field Splitting) of Localized 1,3-Cyclopentanediyl Triplet Diradicals as a Measure of Electronic Substituent Effects on the Spin Densities in Para-Substituted Benzyl-Type Radicals

The zero-field splitting parameters D of the symmetrically disubstituted and unsymmetrically monosubstituted 1,3-diaryl-1,3-cyclopentanediyl triplet diradicals 1, 2 (X = p-MeO, p-Me, p-Cl, p-NH(2), p-CO(2)Me, p-CN, p-NO(2)), and 5 were determined in 2-methyltetrahydrofuran glass at 77 K. The linear plot (m = 0.558, r(2) = 0.993) of the experimental D values for the symmetrically disubstituted derivatives versus the corresponding monosubstituted ones reveals that the electronic substituent effects are additive and implies (except for the magnetic dipolar interaction) that each benzyl-type radical site acts independently in the localized diradicals. This additivity permits us to view these triplet diradicals as a composite of the two separate monoradical components and allows us to assess valuable electronic properties of benzyl-type monoradicals from the D parameter of the triplet diradical species. A theoretical analysis shows that the D parameter is a measure of the spin density rho at the benzylic positions and the inter-radical distance d in localized diradicals. A good correlation exists between the D parameter of these triplet diradicals (constant inter-radical distance d) and the EPR hyperfine coupling constants of the corresponding benzyl-type monoradicals, which establishes that the observed electronic substituent effects reflect changes in the spin densities at the radical sites. The novel DeltaD scale allows us to quantify spectroscopically the para substituent effect on the spin delocalization at the benzylic position.     

Substituent effects on the gas-phase ring-chain tautomerism of 3,4,5,6-tetrahydro-2H-1,3-oxazines

The electron ionization mass spectra of five series of seven 2-aryl,4-R-substituted (R = Me, Et, i-Pr, t-Bu or Ph) 3,4,5,6-tetrahydro-2H-1,3-oxazines were recorded at 14 and 70 eV in order to study the ring-chain tautomeric equilibria in the gas phase. Certain fragment ions were associated with the ring or with the open-chain forms of the compounds. As in chloroform solution, the electron-withdrawing effect of the aryl substituent (p-NO(2), m-Br, p-Cl, H, p-Me, p-OMe and p-NMe(2)) shifts the equilibrium towards the ring form. The correlation of ring-chain equilibria (log K = [ring]/[chain]) with the Hammett sigma+ constants of the aryl substituents was in general good or satisfactory although in some cases the p-NMe(2) did not fit these correlations.