Structural diversity in bishydroxylamine complexes of gallium

Reactions of bishydroxylamines of the type HON(R)CH2CH2N(R)OH (R=Me, tBu) with trimethyl- and triisopropylgallium gave bicyclic metalla cages of the formula R'2GaO(R)NCH2CH2N(R)OGaR'2 [R'=Me, R=Me (), tBu (); R'=iPr, R=Me (), tBu ()] with six-membered Ga2O2N2-rings. While the complexes show the same core constitution in the solid state, NMR spectra reveal the steric influence of the isopropyl substituent of the compounds / on its behaviour in solution. The reaction of the sterically more demanding substituted tri-tert-butylgallium with HON(Me)CH2CH2N(Me)OH yielded a heterodimeric complex O'-[HON(Me)CH2CH2NH(Me)O(tBu2Ga)]-cyclo-(tBu2Ga)-O,N'-[ON(Me)CH2CH2N(Me)O] () with two gallium atoms of different surrounding and two different bishydroxylamine ligands, one doubly deprotonated and one protonated, but at one end in its tautomeric aminoxide form. Further condensation of was observed to give a tricyclic compound cyclo-[(tBuGa)ON(Me)CH2CH2N(Me)O]2 () with a central Ga2O2N2 ring resulting from two Ga-N donor-acceptor bonds.     

Internal rotation study of some sixfold barrier molecules

Molecular orbital calculations of sixfold barriers in nitromethane, methyl boron difluoride, and trifluoronitromethane were performed by various Hartree-Fock and electron correlation methods. In those calculations, staggered and eclipsed conformations are of primary concern. These results indicated that for CH₃NO₂ and CH₃BF₂ the staggered conformations are more stable, while CF₃NO₂ has a more stable conformation in an eclipsed form. Both conformations do not differ significantly, which may account for the low internal rotational barrier of each molecule. Values of the barrier calculated by the Møller-Plesset perturbation and the quadratic configuration interaction methods did not match the experimental results. However, better internal rotational barrier values of each molecule were observed when the improved better basis sets and the Hartree-Fock method were selected. © 1997 John Wiley & Sons, Inc.     

Preparation,Properties and Complexation Behaviour of P,P-Di-tert. Butylphosphinothioic Amides

Abstract

Starting from tBu₂PCl, the title compounds tBu₂P(S)NHR′ (R′= Me Et, iPr, tBu) may be easily prepared according to With R′=tBu the amine has to be substituted by its Li-salt [tBuNH]^?Li^+.     

Insertion of H2C=CHX (X = F, Cl, Br, O(i)Pr) into (tBu3SiO)3TaH2 and beta-X-Elimination from (tBu3SiO)3HTaCH2CH2X (X = OR): relevance to Ziegler-Natta copolymerizations.

The insertion of H2C=CHX (X = OR; R = Me, Et, nPr, (i)Pr, CH=CH2, Ph) into (tBu3SiO)3TaH2 (1) afforded (tBu3SiO)3HTaCH2CH2X (2-CH2CH2X), which beta-X-eliminated to give ethylene and (tBu3SiO)3HTaX (3-X). beta-X-elimination rates were inversely proportional to the size of R. An X-ray crystallographic study of (tBu3SiO)3HTaCH2CH2O(t)Bu (2-CH2CH2O(t)Bu) revealed a distorted trigonal bipyramidal structure with an equatorial plane containing the hydride and a -CH2CH2O(t)Bu ligand with a staggered disposition. erythro- and threo-(tBu3SiO)3HTaCHDCHDOEt (2-CHDCHDOEt) are staggered in solution, according to (1)H NMR spectroscopic studies, and eliminated cis- and trans-HDC=CHD, respectively, helping verify the four-centered transition state for beta-OEt-elimination. When X = F, Cl, or Br, 2-CH2CH2X was not observed en route to 3-X, signifying that olefin insertion was rate-determining. Insertion rates suggested that substantial positive charge on the substituted carbon was incurred. The reactivity of other H2C=CHX with 1, and a discussion of the observations and their ramifications on the incorporation of functionalized monomers in Ziegler-Natta copolymerizations, are presented.     

Radical‐induced oxidation of RAFT agents—A kinetic study

Radical‐induced oxidation of reversible addition‐fragmentation chain transfer (RAFT) agents is investigated with respect to the effect of molecular structure on oxidation rate. The radicals are generated by homolysis of either azobisisobutyronitrile or alkoxyamine and transformed in situ immediately into peroxy radicals through transfer to molecular oxygen. It is found that the oxidation rate depends on the structure of Z‐ and R‐group of thiocarbonylthio compounds. For dithioesters with identical Z‐phenyl substituent, the oxidation rate decreases in the order of cyanoisopropyl (? C(Me)₂CN) > cumyl (? C(Me)₂Ph) > phenylethyl (? CH(Me)Ph) > 2‐methoxy‐1‐methyl‐2‐oxoethyl (? CH(Me) ? C(?O)OCH₃) > benzyl (? CH₂Ph). For dithioesters with identical R‐group, the oxidation rate decreases in the order of Z = phenyl? ～ benzyl? > RS? (trithiocarbonates) > RO? (xanthates). The stability of the RAFT agents toward oxidation correlates well with the chain transfer abilities as those previously reported by Rizzardo and coworkers. The priority of the oxidation reaction over the RAFT process, and the subsequent influence on RAFT polymerization are also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

2‐Phenyl­malonpiperadide and 2‐phenyl­malonmorpholide

The structures of 2‐phenyl­malonpiperadide [systematic name: 2‐phenyl‐1,3‐bis­(piperidin‐1‐yl)­propane‐1,3‐dione, C₁₉H₂₆N₂O₂, (I)] and 2‐phenyl­malonmorpholide [systematic name: 1,3‐dimorpholino‐2‐phenyl­propane‐1,3‐dione, C₁₇H₂₂N₂O₄, (II)], have been determined and both their molecular conformations and packing arrangements compared. Although chemically similar, compounds (I) and (II) exhibit different molecular conformations. The only general conformational similarities are that their respective carbonyl groups are orientated in the same direction and the heterocyclic rings exist in the chair arrangement. General similarities in the packing arrangements arise due to both compounds having the same space group (P2₁2₁2₁) and a similar alignment of their phenyl‐substituted backbone with respect to the c axis. Similar C—H⋯O hydrogen‐bonding associations are listed for the carbonyl O atoms, while only one of the morpholine O atoms is involved in any such association.     

Conformational analysis of X3PNP(O)X2 and (X3PNPX3)+ for X = H,F, Cl,CH3 by the pcilo method

Conformational energy maps have been calculated, using the PCILO method, for X₃PNP(O)X₂ and (X₃PNPX₃)⁺ for X = H, F, Cl, CH₃ as a function of the PNP angle. In H₃PNP(O)H₂ the global energy minimum corresponds to the eclipsed conformation of the H₃P and P(O)H₂ fragments for all PNP angles, while in Cl₃PNP(O)Cl₂, the global minimum always has Cl₃P and P(O)C1₂ staggered: the global minimum in F₃PNP(O)F₂ corresponds to eclipsed F₃P and P(O)F₂ fragments at low PNP angles and staggered fragments at high PNP angles: in (CH₃))₃PNPO(CH₃)₂ the global minimum conformation is very sensitive to ∠ PNP. Subordinate energy minima occur for all X₃PNP(O)X₂, species: in particular, there are two local conformational minima for Cl₃PNP(O)Cl₂ at the optimum value of ∠ PNP, and the relative energies of the three stable conformations are in good agreement with those derivable from the ³¹P NMR spectrum of this compound. In (X₃PNPX₃)⁺ the global minimum, usually the sole minimum on the conformational energy surface, is always close to the eclipsed conformation: free rotation of the X₃P groups relative to one another is approached in each (X₃PNPX₃)⁺ ion as ∠PNP approaches 180°. The conformations of the transition states for the equilibria between energy minima are reported with their relative energies, for X₃PNP(O)X₂ (X = H, F. Cl, CH₃) and for (Cl₃PNPCl₃)⁺     

Oxo(trisyl)boran (Me3Si)3C?BO als Zwischenstufe

Oxo(trisyl)borane (Me₃Si)₃C? B?O as an Intermediate The acyclic trisylboranes R? B(OSiMe₃)? Cl ( 4 a ) and R? B(OH)? H ( 5 a ) and the cyclic boranes (? RB? O? CO? CO? O? ) ( 1 a ) and (? RB? O? RB? O? SO₂? O? ) ( 6 a ) [R = (Me₃Si)₃C, “Trisyl”] are thermolyzed in the gasphase to give well-defined products. The tris(trisyl)boroxine (? RB? O? )₃ ( 2 a ) is formed from 4 a and 5 a at 140 and 160°C, respectively, besides Me₃SiCl and H₂, respectively, whereas the six-membered ring [? BMe? CH(SiMe₃)? SiMe₂? O? SiMe₂? CH₂? ] ( 8 ) is the product from 1 a and 6 a at 600 and 700°C, respectively, besides CO/CO₂ and SO₃, respectively. The oxoborane R? B?O is presumably a common intermediate. It is stabilized at the lower temperature by cyclotrimerization to give 2 and at the higher temperature by a sequence of several intramolecular steps: a 1,3-silyl shift along the chain C? B? O, an exchange of Me and Me₃SiO along the chain Si? C? B, and a C? H addition to the B?C double bond; the steps can be rationalized by analogous known reactions. The gas-phase thermolysis at 600°C of the dioxaboracyclohexenes (? BR? O? CR′ = CH? CRR′? O? ) ( 7 b? d ; R = Me, iPr, tBu; R′ = Me) yields the boroxines (RBO)₃ and the enones Me? CO? CH?CHR? Me; the cyclohexene 7 e (R = Me; R′ = CF₃) is not decomposed at 600°C.     

Reactions de l'hexafluorure de molybdene avec les aldehydes et les cetones fonctionnels

The substituents F, Cl, Br, CN, NO₂, COOR, CONR₂, P(O)R₂ do not interfere with the reaction of MoF₆ with aromatic aldehydes and ketones yielding gem-difluoro compounds, but OH, NH, OR, NR₂, CC, react preferentially with MoF₆ and prevent the reaction at CO. Yields of gem-difluoro compounds are enhanced with electron-attracting substituents on the carbonyl derivative, and are lowered when the CO group is sterically hindered. The hydrolytic stability of the RCF₂R′ compounds vary widely with the nature of R and R′. Some reactions on R and R′ leave the CF₂ group unaffected. Thus a number of new CF₂ compounds are prepared including α,α-difluoroalkyl substituted benzyl alcohol32 benzylamines34, 36 benzaldehyde27, benzoic acids24, 28, 31, 35.¹H and¹⁹F NMR data are given for all the new derivatives. The mechanism of the conversion is tentatively postulated.     

Cis-homo addition-1,4 thiophile d'organomagnesiens avec des composes thiocarbonyles comportant un groupe carbonyle en β: Synthese stereoselective d'alcoylthio-2 et de bis (alcoylthio)-2,2 cyclopropanols

Aliphatic Grignard reagents react stereoselectively with β thioxo carbonyl compounds to give substituted cis 2-alkylthio or 2,2-bis (alkylthio) cyclopropanols with good yields. Two types of non-enethiolisable thiocarbonyl compounds of formulae MeCOC(Me)₂CSR undergo this reaction a thioketone (R = Me) and a number of dithioesters (R = SMe, SEt, S iso Pr). The cis configuration of cyclopropanols has been assigned by ¹H NMR-Eu(fod)₃. The cyclopropane ring closure is a concerted cis-1,4-homo addition.     

Reactivity Studies of Iridium Pyridylidenes [TpMe2Ir(C6H5)2(C(CH)3C(R)NH] (R=H,Me, Ph)

The reactivity of a series of iridium? pyridylidene complexes with the formula [Tp^Me2Ir(C₆H₅)₂(C(CH)₃C(R)N H] ( 1 a – 1 c ) towards a variety of substrates, from small molecules, such as H₂, O₂, carbon oxides, and formaldehyde, to alkenes and alkynes, is described. Most of the observed reactivity is best explained by invoking 16 e^? unsaturated [Tp^Me2Ir(phenyl)(pyridyl)] intermediates, which behave as internal frustrated Lewis pairs (FLPs). H₂ is heterolytically split to give hydride? pyridylidene complexes, whilst CO, CO₂, and H₂C?O provide carbonyl, carbonate, and alkoxide species, respectively. Ethylene and propene form five‐membered metallacycles with an IrCH₂CH(R)N (R=H, Me) motif, whereas, in contrast, acetylene affords four‐membered iridacycles with the IrC(?CH₂)N moiety. C₆H₅(C?O)H and C₆H₅C?CH react with formation of Ir? C₆H₅ and Ir? C?CPh bonds and the concomitant elimination of a molecule of pyridine and benzene, respectively. Finally the reactivity of compounds 1 a – 1 c against O₂ is described. Density functional theory calculations that provide theoretical support for these experimental observations are also reported.     

异-α-姜黄烯及其衍生物的合成

姜科姜黄属是一个重要的药用植物群其根茎和块根分别称为姜黄和郁金。中医中药认为, 郁金具有行气, 纠瘀和通经等功效。动物药理试验表明, 姜科植物温郁金具有抗生育活性, 而其挥发油主要含有姜烯、α-姜黄烯和异-α-姜黄烯等倍半萜类化合物。本文合成了温郁金挥发油的另一个成分异-α-姜黄烯和其衍生物2-甲基-6-对甲苯基-2-庚醇、脱氢异-α-姜黄烯和2-甲基-6-对甲苯基-5-庚烯-2-醇。它们的化学结构得到确证。     

DFT study of substitution effect on the geometry, IR spectra, spin state and energetic stability of the ferrocenes and their pentaphospholyl analogues

Optimal structures, vibrational spectra and thermochemical characteristics of ferrocenes and pentaphosphaferrocenes containing up to five methyl substituents in the cyclopentadienyl ring are found with the use of DFT computations. It is shown that the non-substituted ferrocenes and pentaphosphaferrocenes as well as the species with small number of methyl substituents adopt eclipsed conformations. Increasing the number of the methyl substituents results either in the conformational equilibria between the eclipsed and staggered forms or in complete shift to the staggered conformations. These effects, as well as elongation of CC bonds of the Cp ring and growth of Fe-Cp and Cp-P₅ distances with growing number of methyl groups can be explained by repulsive interactions of the methyl groups with each other or with phosphorus atoms of the pentaphospholyl ligands. The pentaphosphaferrocenes are predicted to be stable towards disproportionation to homoleptic sandwich complexes. This stability grows as the number of methyl substituents in cyclopentadienyl ring increases, which is a result of stronger Fe-P₅ bonding in the methyl substituted pentaphosphaferrocenes relative to the non-substituted species, and destabilization of the homoleptic ferrocenes because of Me?Me repulsion. A huge energy gap between the low- and high-spin states of the ferrocenes and pentaphosphoferrocenes is predicted, though introduction of methyl substituents causes a moderate decrease of the gap. Transition from low- to high-spin state should result in pronounced changes of geometry and IR spectra of the ferrocenes, which suggests that IR spectroscopy can be used for diagnostics of spin state of iron complexes.     

Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XVIII Configurational and conformational studies with derivatives of hexahydroindolizin-2(3H)-one

A series of substituted hexahydroindolizin-2(3H)-ones and some related ketones have been prepared by Dieckmann condensation of the appropriate diesters. Utilising spectral data, the configurations of these compounds have been assigned, and their conformations discussed with particular reference to the magnitude of the geminal coupling constant (J_gem) for the N? CH₂? C(O) protons. With the exception of tetrahydropyrrolizin-2(3H)-one, all the ketones in this study are shown to exist in predominantly trans-fused conformations. In the case of hexahydroindolizin-2(3H) one and hexahydro-2H-quinolizin-3 (4H)-one, the separate contributions to J_gem from the adjacent N lone pair and the carbonyl π electrons are discussed.     

Calculation of the 1J(PP) angular dependence in P2H4

Using the results obtained from an MO SCF ab initio calculation on P₂H₄ in four different conformations, the ¹J(PP) NMR coupling constants have been calculated. The ¹J(PP) values are highly dependent upon the rotational angle φ (?238.0 Hz in the eclipsed conformation, 10.9 Hz in the staggered one). The shape of the theoretical ¹J(PP) plot seems to be in good agreement with experimentally measured ¹J(PP) values.     

Syntheses and Reactions of Dimolybdenum Alkyne Compounds Containing Functionally Substituted Ligands. The Crystal Structure of [Co2Mo2(μ4-CHCH)(μ-CO)4(CO)4-(η5-C5H4C(O)Me)2]

Abstract

Three dimolybdenum alkyne complexes containing functionally substituted ligands [Mo₂(μ-CHCH)(CO)₄(η⁵?C₅H₄C(O)R)₂] [R ? OEt, (1a); R ? Me, (1b); R ? Ph, (1c)] were synthesized by reactions of acetylene with in situ generated metal-metal triply bonded complexes [Mo(CO)₂(η⁵?C₅H₄C(O)R)]₂ (R ? OEt, Me, Ph). Further reaction of (1a), (1b) or (1c) with Co₂(CO)₈ in refluxing toluene gave another three new butterfly compounds [Co₂Mo₂-(μ₄-CHCH)(μ-CO)₄(CO)₄(η⁵-C₅H₄C(O)R)₂] [R ? OEt, (2a); R ? Me, (2b); R ? Ph, (2c)]. The resulting compounds were characterized by elemental analyses, IR, ¹H NMR and MS. The crystal structure of (2b) was determined by single-crystal X-ray analysis. The results indicate that the existence of functional groups on the cyclopentadienyl ring has an influence on the reactivity of this type of complex.     

Synthesis,molecular structure and stereoisomerization of 2-phosphinyl and 2-phosphonylethyl diorganotin halides

Functionally substituted triorganotin halides V–IX of type R₂Sn(X)(CH₂)₂P(O)PhR′ (R = Me, t-Bu; Rt? = OEt, t-Bu; X = Cl, Br) have been synthesized by halogen cleavage of the corresponding tetraorganotin compounds R₂R²Sn(CH₂)₂P(O)PhR′ (R² = Me or Ph), I–IV. The solid state structure of Me₂Sn (Br) (CH₂)₂P(O)PhBu-t (IX), determined by X-ray diffraction, shows a distorted trigonal-bipyramidal structure at the tin atom, with intramolecular coordination of the PO group. Spectroscopic data are in agreement with such a structure in solution for compounds V–IX. Upon varying the temperature, concentration or solvent in solutions of compounds V–IX a stereoisomerization is observed. On the basis of NMR ¹H, ¹³C, ³¹P, ¹¹⁹Sn), IR and conductivity studies, it is suggested that this stereoisomerization involves a hexacoordinated transition state at the tin atom.     

Metallo(alkyl)chlorophosphanes Cp(CO)3 M-P(R)CI (M=Mo,W; R=Me,Ph, tBu,C5Me5) - Novel Sources for Phosphinidenes

Abstract

Metallation of organodichlorophosphanes RPC1₂ (R=Me, Ph, tBu, C₅Me₅) with Na[M(CO)₃Cp] (M=Mo, W) in benzene yields the thermolabile Metallo(alkyl)chlorophosphanes la-g. In solution la-d show a high tendency to decompose to the corresponding metal chloride Cp(CO)₃M-Cl with phosphinidene elimination. The rate of decomposition depends on the metal and the phosphorus ligand (Mo > W, Me > Ph > tBu C₅Me₅)     

Komplexchemie P-reicher Phosphane und Silylphosphane. VIII. Zur unterschiedlichen Tendenz der Bildung von Chromcarbonyl-Komplexen silylierter-alkylierter Phosphane und Diphosphane

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. VIII. Concerning the Different Tendencies of Silylated and Alkylated Phosphanes and Diphosphanes to Form Chromium Carbonyl Complexes The influence of the substituents Me₃Si tBu and Me in phosphanes and diphosphanes on the formation of complex compounds with Cr(CO)₅THF is investigated. tBu(Me₃Si)P? P(SiMe₃)₂ 1 and (tBu)₂P? P(SiMe₃)₂ 2, resp., react with Cr(CO)₅THF 4 at ?18°C by coordinating Cr(CO)₅ to the P(SiMe₃)₂ group to give tBu(Me₃Si)P? P^IV(SiMe₃), · Cr(CO)₅ 1 a, tBu(Me₃Si)P^IV? P^IV(SiMe₃)₂ · Cr(CO)₄ 1b and (tBu)₂P? P^IV(SiMe₃)₂ · Cr(CO)₅ 2a . In the reaction of 1 with 4 using a molar ratio of 1:2 at first 1 a is formed which reacts on to yield completely 1 b. In a mixture of the dissolved compounds (Me₃Si)₃P 5, (tBu)₃P 6 and (tBu)₃P? P(SiMe₃)₂ 2 only 5 and 6 react with Cr(CO)₅THF yielding (Me₃Si)₃P · Cr(CO)₅ and (tBu)₃P · Cr(CO)₅, but 2 does not yet react. In a solution of (Me₃Si)₃P 5, P₂Me₄ 7 and (Me₃Si)₂P? PMe₂ 3 only 5 and 7 react with Cr(CO)₅THF (0.25 to 1.5 equivalents with respect to 3) to give (Me₃Si)₃P · Cr(CO)₅, P₂Me₄ · Cr(CO)₅ and P₂Me₄ · 2Cr(CO)₅. The formation of complexes with Cr(CO)₅THF of the phosphanes 5 and 6 is clearly favoured as compared to the silylated diphosphanes 2 and 3 (not to P₂Me₄); the PR₂ groups (R = tBu, Me in 2 or 3 ) don't have a strong influence.     

Synthesis and structural characterization of 3-thienyl alkyl imides

Five new thiophene imides having the structures C₄H₃SC(O)N(H)C(O)R (where R=Me, Et, Pr, t-Bu, 1-4) and C₄H₃SCH₂C(O)N(H)C(O)CH₃5 have been prepared. Control over the orientation of the carbonyl groups was achieved by the introduction of a bulky group in the terminal position of the side chain, and molecular modeling calculations indicated that the energy difference between the ct and tt conformations is small. The acidity of 1-4 decreases from Me to t-Bu, and, although 1-4 will not undergo oxidative polymerization, the introduction of a single spacer CH₂ group allows 5 to polymerize.