Elementorganische Amin/Imin-Verbindungen,XXXI. Cyclometallierung bei N-tert-Butyl-Phosphor-Stickstoff-Iridiumkomplexen

Element-Organic Amine/Imine Compounds, XXXI. - Cyclometallation with N-tert-Butyl-Phosphorus-Nitrogen Iridium Complexes The interaction of R¹R²N–PNR³ ( 1 ) (R¹  SiMe₃, tBu, iC₃H₇; R²  R³  SiMe₃, tBu) with [M(COD)(μ-Cl)]₂ ( 2 ), M  Rh, Ir, affords the amino(imino)phosphane complexes 3 , whose PN bond adds methanol with formation of the diamidophosphite complexes 4 . Already below 0°C the iridium compounds of 4 undergo cyclometallation of a tBu methyl group (R²) with formation of the hydrido-iridium metallaheterocycles 5 . The structures of 4b and 5a are elucidated by X-ray analyses.     

Substituted 1,3,2,4‐benzodithiadiazines: Novel derivatives,by‐products,and intermediates*

The synthesis of the title compounds 1 by 1 : 1 condensation of Ar NSNSiMe₃ 2 with SCl₂ followed by intramolecular ortho‐cyclization of each [Ar NSN S Cl] intermediate is complicated by further reaction of 1 with SCl₂ to give Herz salts 3 . With the 2 :SCl₂ ratio of 2:1, the formation of by‐products 3 is reduced and novel compounds 1 are accessible. With ortho‐I containing starting material 2j , the parent compound 1s is obtained as the result of an unexpected I, not H, substitution. The rate of the 1 + SCl₂ reaction depends upon a substituent's position, and the minor 8‐R isomers 1l,p (R = Br, I) are isolated for the first time from mixtures with the major 6‐R isomers due to reduced reactivity toward SCl₂. The synthesized compounds 1–3 are characterized by multinuclear (including nitrogen) NMR and X‐ray crystallography. According to the X‐ray diffraction data, 1j (6‐Br) and 1k (7‐Br) derivatives are planar, whereas 1i (5‐Br) and 1l (8‐Br) are bent along the S1···N4 line by ∼5° and ∼4°, respectively, and the 1r (7‐OCH₃) derivative is planar in contrast to the known 5‐OCH₃ isomer, which possesses a significantly folded heterocycle. The distortion of the planar geometry of some compounds 1 is interpreted in terms of a pseudo‐Jahn‐Teller effect as the result of π‐highest occupied molecular orbital (HOMO)  σ*‐(LUMO) lowest unoccupied molecular orbital + 1 mixing in a planar conformation. The 2p compound is the first structurally defined Ar–N = S = N–SiMe₃ azathiene. The compound Ar–N = S = N–S–NH‐Ar 6 modeling the aforementioned intermediate has been isolated and structurally characterized. We describe the attempts to synthesize compounds 1 from 2‐aminobenzenethiols and (SN)₄ and from salts 3 and Me₃SiN₃, and we discuss the reaction pathways. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:563–576, 2001     

The heavier pnictogen and chalcogen analogues of isocyanic and cyanic acids and their dimers: A high level ab initio study

The CCSD(T)/cc-pVTZ//CCSD/cc-pVTZ method is used to determine the geometries and energetics of the isomers HXCY vs HY─CX (XN, P, As; YO, S) and their dimers from chain dimerizations and head-to-head or head-to-tail [2 + 2] cyclodimerizations. The HO─CX structures with CX triple bonds lie at energies at least 18.5 kcal/mol above their HXCO isomers. However, the energy differences between the HXCS and HS─CX isomers are found to be particularly small, especially in the [H,P,C,S] and [H,As,C,S] systems. For (HNCY)₂, the lowest energy dimers are the chain isomers, which lie ~11 kcal/mol below the lowest energy cyclic dimers aNO containing a NCNC ring and cNS containing a NCSC ring. Formation of the remaining dimers through dimerization from two monomers is predicted to be endothermic and thus thermodynamically disfavored. However, the energies of the chain isomers in the other (HXCY)₂ (XP, As; YO, S) series are higher than those of the corresponding isomeric lowest energy cyclodimers. For (HXCO)₂ (XP, As), the lowest energy structures are the head-to-head dimers hPO and hAsO containing a C─C─XX ring. For (HXCS)₂ (XP, As), the lowest energy structures are the head-to-head dimers gPS and gAsS with a CCXS ring.     

铱催化环加成反应的研究进展

过渡金属催化环加成反应是合成单环及多环化合物的重要方法,也是有机化学的研究热点之一.综述了近年来铱催化环加成反应的研究进展,主要包括了[2+2+1],[2+2+2],[4+2],1,3-偶极环加成反应等,及少量关于[3+2+2],[3+2],[5+1]环加成反应的报道,并讨论了部分铱催化环加成反应机理.     

Efficient synthesis and crystal structure of 2‐propyl‐5‐(substituted)phenyl‐1,4‐dioxo‐1,2,3,4,5,6,7,8‐octahydro‐[1,4,2]diazaphosphorino[1,2‐a] [1,3,2]benzodiazaphosphorine 3‐oxides

In order to search for novel antitumor and antiviral agents with high activity and low toxicity, some 2‐propyl‐5‐(substituted)phenyl‐1,4‐dioxo‐1,2,3,4,5,6,7,8‐octahydro‐[1,4,2]diazaphosphorino[1,2‐a][1,3,2]benzodiazaphosphorine 3‐oxides ( 2a–e ) have been designed incorporating the proximate carbonyl and phosphoryl groups into the benzoannulated phosphadiamide heterocycle and synthesized in acceptable yields. These compounds contain the proximate carbonyl and phosphoryl groups in the fused heterocycle. Their structures were confirmed by spectroscopic methods and microanalyses. The results from X‐ray crystallography analysis of 2a showed that the proximate carbonyl and phosphoryl groups are not coplanar because of their being jointly located in the fused heterocycle, having ring tension, and this then destroys the conjugation between the CO and the PO moieties. As a result, the length of the P C bonds measured as 1.851(3)–1.852(3) Å are just the same as that of a P C bond not involved in conjugation (1.80–1.85 Å). Also,the C(1), C(2), C(3), N(2), N(3), and P(1) atoms of the [1,4,2]diazaphosphorino moiety exist preferably in the boat conformation. The coplanar C(1), C(3), N(2), and N(3) atoms, within an average deviation of 0.0102 Å, form the ground floor of the boat conformation, whereas the P(1) and C(2) atoms are on the same side of the coplanar structure with the distance of 0.7067 and 0.6315 Å, respectively. © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:63–71, 2002; DOI 10.1002/hc.1107     

An efficient synthesis and crystal structure of novel 1‐oxo‐2‐propyl‐4‐(substituted)phenylimino‐1,2,3,4,5,6,7,8‐octahydro[1,4,3]thiazaphosphorino[4,3‐a][1,3,2]benzodiazaphosphorine 3‐oxides

A series of 1‐oxo‐2‐propyl‐4‐(substituted)phenylimino‐1,2,3,4,5,6,7,8‐octahydro‐[1,4,3]thiazaphosphorino[4,3‐a][1,3,2]benzodiazaphosphorine 3‐oxides ( 5a–g ) has been synthesized in excellent yields via the reaction of 1‐(2‐bromoethyl)‐2,3‐dihydro‐3‐propyl‐1,3,2‐benzodiazaphosphorin‐4(1H)‐one 2‐oxide with (substituted) phenyl isothiocyanates, which contain the proximate imino and phosphoryl groups in the fused heterocycle. The structures of all of the new compounds were confirmed by spectroscopic methods and microanalyses. The results from X‐ray crystallography analysis of 5a showed that the proximate imino and phosphoryl groups are not coplanar due to their being jointly located in the fused heterocycle, thus having ring tension, and this then destroys the conjugation between the CN and the PO moieties. As a result, the length of the P C bond, measured as 1.8285(18) Å, is just the same as that of a P C bond not involved in conjugation (1.80–1.85 Å). Also, the C(1), C(2), S(1), C(3), P(1), and N(2) atoms of the [1,4,3]thiazaphosphorino moiety exist preferably in the boat conformation. The coplanar C(1), N(2), C(3), and S(1) atoms, within an average deviation of 0.0564 Å, form the ground floor of the boat conformation, whereas, the P(1) and C(2) atoms are on the same side of the coplanar structure with the distance of 0.7729 Å and 0.7621 Å, respectively. On the other hand, around the CN double bond, the P(1) C(3) bond and the N(1) C(11) bond are in a trans relationship because of the repulsive action of the n‐propyl group in the 2‐position of the title compound. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:599–610, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10041     

Reactive EC(p‐p)π‐systems 53 [1]: Reactivity studies on perfluoro‐2‐arsapropene: [2+2]‐cycloaddition reactions and quantum chemical calculations

The extremely labile perfluoro‐2‐arsapropene F₃CAsCF₂ ( 1 ) has been generated by an improved pyrolysis process of Me₃SnAs(CF₃)₂ and found to be stabilized by the presence of hexamethyldisiloxane and tert‐butylphosphaethyne, thus allowing (i) reactivity studies with alkyne derivatives like tBuCP, (iPr)₂NCP, MeCCN(iPr)₂, HCCOEt and (ii) a full NMR investigation of 1 (¹⁹F, ¹³C). Due to the instability of 1 and some of the products, the [2+2]‐cycloaddition reactions gave the expected arsaphospha‐ and arsa‐cyclobutene derivatives, respectively, in moderate to good yields, but in some cases contaminated with side and/or decomposition products. Unequivocal characterization of the novel compounds was accomplished by spectroscopic in‐ vestigations (¹H, ¹³C, ¹⁹F, ³¹P NMR, IR, MS) supported by comparison with the data of the more stable phosphorus analogues. An interesting isomerization was observed for the 2‐dialkylamino‐4,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐3‐phospha‐2‐cyclobutenes yielding the more stable 3‐dialkylamino‐2,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐2‐phospha‐3‐cyclobutenes. Quantum chemical calculations [B3LYP/6‐311+ G(d,p)] of HAsCH₂, F₃CAsCF₂, and F₃CPCF₂ were carried out to compare the length of the AsC double bond with the literature data and to elucidate substituent effects on its electronic structure. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:406–419, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20118     

The tautomerization and ring closure in the Claisen rearrangement: A DFT study

Elementary processes of the aromatic Claisen rearrangement were investigated by DFT calculations. First, rearrangements of four substrates Ph—O—CH₂—CHCH₂ [A], Ph—O—CH₂—CHCH(OMe) [B], Ph—O—CH₂—CHCH₂····BF₃ [C], and Ph—O—CH—CHCH(OMe)····BF₃ [D] were examined. In these systems, the tautomerization is initiated by the intermolecular proton transfer involving the transient ion‐pair intermediate. An ignition‐propagation chain‐reaction mechanism in the tautomerization was suggested. For [A], the (ortho‐allyl phenol → α‐methyl‐dihydrobenzofuran (α‐methyl‐cumarane)) process was found to be ready and the product of the Claisen rearrangement seems to be the cumarane rather than the phenol. In [D] (activated both by the terminal methoxy group and by the BF₃ catalyst), not the [3,3]‐sigmatropic shift but the tautomerization is the rate determining step. Second, the parent system, Ph—O—CH₂—CHCH₂, was investigated with (H₂O) _n (n = 2, 4, 6, and 10) systematically. The tautomerization takes place by the proton transfer via the water dimer or trimer. Except n = 2, similar changes of Gibbs free energies were obtained from the ether substrate to the cumarane.     

Total Synthesis of Tri-, Hexa- and Heptasaccharidic Substructures of the O-Polysaccharide of Providencia rustigianii O34

A general and efficient strategy for synthesis of tri-, hexa- and heptasaccharidic substructures of the lipopolysaccharide of Providencia rustigianii O34 is described. For the heptasaccharide seven different building blocks were employed. Special features of the structures are an α-linked galactosamine and the two embedded α-fucose units, which are either branched at positions-3 and -4 or further linked at their 2-position. Convergent strategies focused on [4+3], [3+4], and [4+2+1] couplings. Whereas the [4+3] and [3+4] coupling strategies failed the [4+2+1] strategy was successful. As monosaccharidic building blocks trichloroacetimidates and phosphates were employed. Global deprotection of the fully protected structures was achieved by Birch reaction.     

Homoleptic cobalt and copper phenolate A2[M(OAr)4] compounds: the effect of phenoxide fluorination

Two series of homoleptic phenolate complexes with fluorinated aryloxide ligands A2[M(OAr)4] with M=Co2+ or Cu2+, OAr-=(OC6F5)- (OArF) or [3,5-OC6H3(CF3)2]- (OAr'), A+=K (18-crown-6)+, Tl+, Ph4P+, Et3HN+, or Me4N+ have been synthesized. Two related complexes with nonfluorinated phenoxide ligands have been synthesized and studied in comparison to the fluorinated aryloxides demonstrating the dramatic structural changes effected by modification of OPh to OAr(F). The compounds [K(18-crown-6)]2[Cu(OArF)4], 1a; [K(18-crown-6)]2[Cu(OAr')4], 1b; [Tl2Cu(OArF)4], 2a; [Tl2Cu(OAr')4], 2b; (Ph4P)2[Cu(OArF)4], 3; (nBu4N)2[Cu(OArF)4], 4; (HEt3N)2[Cu(OArF)4], 5; [K(18-crown-6)]2[Cu2(mu2-OC6H5)2(OC6H5)4], 6; [K(18-crown-6)]2[Co(OArF)4], 7a; [(18-crown-6)]2[Co(OAr')4], 7b; [Tl2Co(OArF)4], 8a; [Tl2Co(OAr')4], 8b; (Me4N)2[Co(OArF)4], 9; [Cp2Co]2[Co(OAr')4], 10; and [(18-crown-6)])[Co2(mu2-OC6H5)2(OC6H5)4], 11, have been characterized with UV-vis and multinuclear NMR spectroscopy and solution magnetic moment studies. Cyclic voltammetry was used to study 1a, 1b, 7a, and 7b. X-ray crystallography was used to characterize 1b, 3, 4, 5, 6, 7a, 7b, 10, and 11. The related [MX4]2- compound (Ph4P)2[Co(OArF)2Cl2], 12, has also been synthesized and characterized spectroscopically, as well as with conductivity and single-crystal X-ray diffraction. Use of fluorinated aryloxides permits synthesis and isolation of the mononuclear, homoleptic phenolate anions in good yield without oligomerized side products. The reaction conditions that result in homoleptic 1a and 7a with OArF upon changing the ligand to OPh result in mu2-OPh bridging phenoxides and the dimeric complexes 6 and 11. The [M(OArF)4]2- and [M(OAr')4]2- anions in 1a, 1b, 3, 4, 5, 7a, 7b, 9, and 10 demonstrate that stable, isolable homoleptic phenolate anions do not need to be coordinatively or sterically saturated and can be achieved by increasing the electronegativity of the ligand.     

Sol–gel derived Si/C/O/N‐materials: molecular model compounds,xerogels and porous ceramics

Polymeric Si/C/O/N xerogels, with the idealized polymer network structure comprising [Si O Si(NCN)₃]_n moieties, were prepared by reactions of hexachlorodisiloxane (Cl₃Si O SiCl₃) with bis(trimethylsilyl)carbodiimide (Me₃Si NCN SiMe₃, BTSC). NMR and FTIR spectra indicate the existence of ‐NCN‐ and Si O Si‐ units in the xerogels and also in the ceramic materials obtained upon pyrolysis. The feasibility of this reaction protocol was confirmed on the molecular level by the deliberate synthesis of the macrocyclic compound [SiPh₂ O SiPh₂(NCN)]₂, the crystal structure and spectroscopic data of which are reported. The influence of pyridine as a catalyst for the cross‐linking reaction was studied. The degree of cross‐linking increased within the polymers with the addition of pyridine. It was shown by the reaction of hexachlorodisiloxane with excess pyridine that the latter appears to activate only one out of the two ‐SiCl₃ moieties under formation of hexacoordinated silicon compounds. The crystal structure of Cl₃Si O SiCl₃(pyridine)₂ is presented. Quantum chemical calculations are in support of this adduct being a potential intermediate in the pyridine catalyzed sol–gel process. The ceramic yield after pyrolysis of the Si/C/O/N‐xerogels at 1000 °C, which reaches values up to 50%, was found to depend on the aging protocol (time, temperature), whereas no correlation was found with the amount of pyridine added for xerogel synthesis. The Si/C/N/O‐ceramics obtained after pyrolysis at 1000 °C under NH₃ are completely amorphous. Chemically they have to be considered as hybrids between an ideal [SiOSi(NCN)₃]_n network and glass‐like Si₂N₂O. The products are mesoporous with closed pores and a broad pore size distribution. Copyright © 2011 John Wiley & Sons, Ltd.     

A SERIES OF TRINUCLEAR MOLYBDENUM CLUSTERS WITH LOOSE COORDINATION SITES

<正> The cluster compound Mo3S4[S2P(OEt)2]4(H2O) with a comparatively stable cluster core [Mo3(μ3-S)(μ-S)3]4+ and some labile ligands or loosely coordination sites has been already prepared successfully by a self-assembly reaction. Its surprising chemical reactivity in the reactions of substitution, addition, and oxidation has been noted and used widely for the syntheses of a series of new, trinuclear Mo cluster compounds, of which the structures of the 12 selected compounds characterized by X-ray diffraction analysis are exhibited in diagrams. Meanwhile, those compounds with the same cluster core [Mo3(μ3-S)(μ-S)2]4+ show two groups of characteristic IR bands at ~480 cm-1 for the Mo-(μ-S) vibration and -450cm-1. for the Mo- (μ3-S), and their selected bond distances are tabulated as well.In a cluster-catalyzed homogeneous process, it is important that clusters have loose coordination sites or are coordination unsaturated. In our further research on the medium-valence molybdenum clusters[1], we have foun     

Homoleptic rare-earth metal(III) tetramethylaluminates: structural chemistry, reactivity, and performance in isoprene polymerization

The complexes [Ln(AlMe4)3] (Ln=Y, La, Ce, Pr, Nd, Sm, Ho, Lu) have been synthesized by an amide elimination route and the structures of [Lu{(micro-Me)2AlMe2}3], [Sm{(micro-Me)2AlMe2}3], [Pr{(micro-Me)2AlMe2}3], and [La{(micro-Me)2AlMe2}2{(micro-Me)3AlMe}] determined by X-ray crystallography. These structures reveal a distinct Ln3+ cation size-dependency. A comprehensive insight into the intrinsic properties and solution coordination phenomena of [Ln(AlMe4)3] complexes has been gained from extended dynamic 1H and 13C NMR spectroscopic studies, as well as 1D 89Y, 2D 1H/89Y, and 27Al NMR spectroscopic investigations. [Ce(AlMe4)3] and [Pr(AlMe4)3] have been used as alkyl precursors for the synthesis of heterobimetallic alkylated rare-earth metal complexes. Both carboxylate and siloxide ligands can be introduced by methane elimination reactions that give the heterobimetallic complexes [Ln{(O2CAriPr)2(micro-AlMe2)}2(AlMe4)(C6H14)n] and [Ln{OSi(OtBu)3}(AlMe3)(AlMe4)2], respectively. [Pr{OSi(OtBu)3}(AlMe3)(AlMe4)2] has been characterized by X-ray structure analysis. All of the cerium and praseodymium complexes are used as precatalysts in the stereospecific polymerization of isoprene (1-3 equivalents of Et2AlCl as co-catalyst) and compared to the corresponding neodymium-based initiators reported previously. The superior catalytic performance of the homoleptic complexes leads to quantitative yields of high-cis-1,4-polyisoprene (>98%) in almost all of the polymerization experiments. In the case of the binary catalyst mixtures derived from carboxylate or siloxide precatalysts quantitative formation of polyisoprene is only observed for nLn:nCl=1:2. The influence of the metal size is illustrated for the heterobimetallic lanthanum, cerium, praseodymium, neodymium, and gadolinium carboxylate complexes, and the highest activities are observed for praseodymium as a metal center in the presence of one equivalent of Et2AlCl.     

N-alkyl-C-polyfluoroalkyl-C-chlorosulfinimides RFC(Cl)SN?R

The N-alkyl-C-polyfluoroalkyl-C-chlorosulfinimides R_FC(Cl)SN R have been investigated. Some aspects of their thermal stability and their [3 + 2] and [3 + 1] cycloaddition reactions have been examined.     

Methylcobaltverbindungen mit nicht chelatisierenden Liganden,IV. Monoolefinkomplexe

Methylcobalt Compounds with Non-chelating Ligands, IV. Monoolefin Complexes Tris(trimethylphosphane)cobalt(I) halides in ether solvents saturated with olefin at low temperatures from monoolefin complexes which are prone to dissociation. Upon reaction with methyl-or phenyllithium more stable compounds are formed of the composition CoR(CC)L₃ ( 1 – 4 ) (R  CH₃; CC  C₂H₄, C₃H₆, cyclo-C₅H₈; R  C₆H₅; CC  C₂H₄; L  P(CH₃)₃). In solution the fluctional molecules adopt a ground state structure containing a σ-bonded group and an olefin ligand in adjacent positions (trigonal-bipyramidal: CH₃ axial and C₂H₄ equatorial or C₆H₅ and C₂H₄ equatorial). The latter arrangement is confirmed for the crystalline state by an X-ray structure determination of (ethene)phenyltris(trimethylphosphane)cobalt ( 4 ). An equatorial plane of coordination along a Co P bond not only contains both ethene-C atoms but also all the atoms of the phenyl group. The compound is thermally decomposed to give biphenyl and (ethene)tris-(trimethylphosphane)cobalt(0). No products of an olefin insertion reaction are observed.     

Bimetallic effects in homopolymerization of styrene and copolymerization of ethylene and styrenic comonomers: scope, kinetics, and mechanism

This contribution describes the homopolymerization of styrene and the copolymerization of ethylene and styrenic comonomers mediated by the single-site bimetallic "constrained geometry catalysts" (CGCs), (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [EBICGC(TiMe2)2; Ti2], (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [EBICGC(ZrMe2)2; Zr2], (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [MBICGC(TiMe2)2; C1-Ti2], and (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [MBICGC(ZrMe2)2; C1-Zr2], in combination with the borate activator/cocatalyst Ph3C+ B(C6F5)4- (B1). Under identical styrene homopolymerization conditions, C1-Ti2 + B1 and Ti2 + B1 exhibit approximately 65 and approximately 35 times greater polymerization activities, respectively, than does monometallic [1-Me2Si(3-ethylindenyl)(tBuN)]TiMe2 (Ti1) + B1. C1-Zr2 + B1 and Zr2 + B1 exhibit approximately 8 and approximately 4 times greater polymerization activities, respectively, than does the monometallic control [1-Me2Si(3-ethylindenyl)(tBuN)]ZrMe2 (Zr1) + B1. NMR analyses show that the bimetallic catalysts suppress the regiochemical insertion selectivity exhibited by the monometallic analogues. In ethylene copolymerization, Ti2 + B1 enchains 15.4% more styrene (B), 28.9% more 4-methylstyrene (C), 45.4% more 4-fluorostyrene (D), 41.2% more 4-chlorostyrene (E), and 31.0% more 4-bromostyrene (F) than does Ti1 + B1. This observed bimetallic chemoselectivity effect follows the same general trend as the pi-electron density on the styrenic ipso carbon (D > E > F > C > B). Kinetic studies reveal that both Ti2 + B1 and Ti1 + B1-mediated ethylene-styrene copolymerizations follow second-order Markovian statistics and tend to be alternating. Moreover, calculated reactivity ratios indicate that Ti2 + B1 favors styrene insertion more than does Ti1 + B1. All the organozirconium complexes (C1-Zr2, Zr2, and Zr1) are found to be incompetent for ethylene-styrene copolymerization, yielding only mixtures of polyethylene and polystyrene. Model compound (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)][Ti(CH2Ph)2]}2 {EBICGC[Ti(CH2Ph)2]2; Ti2(CH2Ph)4} was designed, synthesized, and structurally characterized. In situ activation studies with cocatalyst B(C6F5)3 suggest an eta(1)-coordination mode for the benzyl groups, thus supporting the proposed polymerization mechanism. For ethylene-styrene copolymerization, polar solvents are found to increase copolymerization activities and coproduce atactic polystyrene impurities in addition to ethylene-co-styrene, without diminishing the comonomer incorporation selectivity. Both homopolymerization and copolymerization results argue that substantial cooperative effects between catalytic sites are operative.     

Discharge flow‐chemiluminescence study of the rate coefficients for O(3P) + CF2CCl2 and O(3P) + CF3CFCF2 reactions at 298 K

The kinetics of the reactions O(³P) + CF₂CCl₂ and O(³P) + CF₃CFCF₂ were studied at room temperature in a discharge flow tube system. The overall rate constants based on the measured afterglow reactions were (3.10 ± 0.40) × 10⁻¹³ and (3.00 ± 0.60) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, respectively. The experiments were carried out under pseudo‐first‐order conditions with [O(³P)]₀ ≪ [alkene]₀. These results are compared with previous relative measurements using different experimental techniques. The effect of substituent atoms or groups on the overall rate constants is analyzed in comparison with other alkenes in the literature. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 867–872, 1999     

Imine- and Amine-Type Macrocycles Derived from Chiral Diamines and Aromatic Dialdehydes

The condensation of aromatic dialdehydes with chiral diamines, such as 1,2-trans-diaminocyclohexane, leads to various enantiopure or meso-type macrocyclic Schiff bases, including [2 + 2], [3 + 3], [4 + 4], [6 + 6] and [8 + 8] condensation products. Unlike most cases of macrocycle synthesis, the [3 + 3] macrocycles of this type are sometimes obtained in high yields by direct condensation without a metal template. Macrocycles of other sizes from this family can often be selectively obtained in high yields by a suitable choice of metal template, solvent, or chirality of the building blocks. In particular, the application of a cadmium(II) template results in the expansion of the [2 + 2] macrocycles into giant [6 + 6] and [8 + 8] macrocycles. These imine macrocycles can be reduced to the corresponding macrocyclic amines which can act as hosts for the binding of multiple cations or multiple anions.     

Aminolysis of P-trichloro-N-dichlorophosphorylmonophosphazene and the crystal structure of 1-(dichlorophosphinyl)-2-chloro-2,2-bis(diisopropylamino)phosphazene

The reactions of Cl₃PN P(O)Cl₂ ( 1 ) with primary and secondary amines have been studied. The following monophosphazenes, (RRN)₃PN P(O)(NRR)₂, and bis(phosphinoyl)amines, [(RRN)₂P(O)]₂NH were isolated: NRR = NHCH₂Ph, Net₂, NH(CH₂)₂CH₃ groups for monophosphazenes, and Net₂, NH(CH₂)₂CH₃ for phosphinoyl amines. The unexpected geminal phosphazene, Cl(RRN)₂PN P(O)Cl₂, {RRN = N[CH(CH₃)₂]₂}, was also obtained in moderate yield. The spectral data (IR, ¹H, ¹³C, and ³¹P NMR, and MS) are presented. The structure of 1-(dichlorophosphinyl)-2-chloro-2,2-bis(diisopropylamino)phosphazene ( 5 ) was determined by X-ray crystallography. The basicities of these and related compounds in nonaqueous nitrobenzene solution were obtained by potentiometric titration.     

Synthesis, structures and theoretical investigation of

The silylated derivative of thiophosphoric acid (S)P(SSiMe3)3 is used as a convenient starting compound for the synthesis of multinuclear Cu and Au cluster complexes. (S)P(SSiMe3)3 reacts with CuCI/PPh3 and [AuCClPPh3] to give the following compounds: [Cu4(P2S6)(PPh3)4] (1), [Cu6(P2S6)Cl2-(PPh3)6] (2) and [Au4(P2S6)(PPh3)4](3). According to X-ray structure determination, these compounds contain P2S6(4-) ions, in which S atoms act as ligands for Cu+ and Au+ ions. Although 1 and 3 have the same stoichiometry, bonding of the metal ions to the P2S6 skeleton displays small but remarkable differences. Au is twofold coordinated, whereas Cu shows a threefold coordination. Ab initio calculations have been carried out to rationalise these structural differences. The theoretical treatment of the corresponding Ag compound indicates the latter to be less stable.