The crystal and molecular structure of bis(pentamethylcyclopentadienyl)dichlorotitanium(IV)

The structure of bis(pentamethylcyclopentadienyl)dichlorotitanium(IV) has been investigated by single-crystal X-ray diffraction techniques. [η-C₅(CH₃)₅]₂TiCl₂ crystallizes in the orthorhombic space group P2₁2₁2₁ with cell dimensions a = 10.816(1), b = 8.132(1), c = 22.259(1) Å; Z = 4. Full matrix, least-squares refinement converged to a final R index of 0.032 based on 1429 reflections. The configuration about the titanium atom is a distorted tetrahedron comprised of the two chlorine atoms and the centroids of the two η-cyclopentadienyl rings. Several ring methyl groups are bent considerably out of the cyclopentadienyl plane and away from the titanium atom. These out-of-plane deviations are attributable to chlorine—methyl crowding and methyl—methyl contacts between the two rings.     

The crystal and molecular structures of bis (pentafluorophenyl)disulphide and bis(pentafluorophenyl)diselenide

The structures of (C₆F₅)₂S₂ and (C₆F₅)₂Se₂ have been determined by single crystal, X-ray diffraction techniques. The compounds are isostructural although the molecules are packed differently in the crystal in comparison with their phenyl analogues. Important bond lengths and angles are: SS, 2.059(4)Å; SeSe, 2.319(4)Å; SC, 1.770Å; SeC, 1.910(15)Å; SSC, 101.3(3)°; SeSeC, 98.8(1)°.     

Syntheses and structure of bis(pentamethylcyclopentadienyl)-dithiophosphinato Complexes

Bis(pentamethylcyclopentadienyl)phosphane Cp*₂PH reacts with sulfur under basic conditions to give the corresponding dithiophosphinate salts M⁺ CP*₂PS−2 ( 5 M⁺ = HNEt+3, 6 M⁺ = Li⁺), which are formed via the intermediate CP*₂P(S)H ( 4 ). Both salts on treatment with cobalt(II) chloride give rise to the transition metal dithiophosphinate 7 . The structures of this new type of diorganodithiophosphinate complexes in the solid state have been investigated. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8 : 521–525, 1997     

The crystal and molecular structure of pentamethylcyclopentadienyl(cyclopentadienyl)titaniumdichloride

An X-ray study of (C₅H₅)[(CH₃)₅C₅]TiCl₂ has shown that the coordination of ligands in the molecule is that of a distorted tetrahedron with two staggered five-membered rings π-bonded to titanium [(TiC)_av. 2.40 »]. The cyclopentadienyl rings are tilted at an angle of 130° and the two σ-bonded Cl atoms are separated by an average distance of 2.33 ». The ClTiCl bond angle is equal to 94.8°.     

The molecular structures of pentaborane(9) and pentaborane(11) in the gas phase as determined by electron diffraction

The structure of gaseous arachno-B₅H₁₁ has been redetermined by electron diffraction and shown to be similar to that found in the solid state at low temperature (93 K) except that the inner basal interatomic distance B(3)B(4) appears to be somewhat shorter in the gas phase. The data are consistent with the presence of asymmetric B(2)H(2,3)B(3) and B(5)H(4,5)B(4) bridges with the two halves of each bridge differing in length by ca. 12 pm. The unique endo/face-capping H atom attached to the apical B(1) atom has not been located with high precision, but the best fit to the data is obtained for an asymmetric structure with the distances B(2) … H(1)_endo and B(5) … H(1)_endo differing by 31 pm. For comparison, the structure of nido-B₅H₉ has also been redetermined by electron diffraction. The interatomic distances are in excellent agreement with those previously obtained from microwave data. The directly-bonded BH(bridge) distances reveal an unusually large amplitude of vibration of the bridging H atoms but it was not possible to establish whether this was a real effect or whether the structure has a lower symmetry than that expected.     

Crystal structures of two polymeric bis(triphenyltin) malonates

In an attempt to prepare potassium/sodium salts of malonato-triphenylstannate, two bis(triphenyltin) malonates were obtained instead, [(C₆H₅)₃Sn]₃[O₂CCH₂CO₂]_1.5 (1) and {[(C₆H₅)₃SnO₂CCH₂CO₂Sn(C₆H₅)₃]H₂O}CH₃CH₂OH (2). This provides an excellent example of structural diversity in triorganotin carboxylates. In both complexes, the dicarboxylate was connected to the triphenyltin groups forming a linear infinite polymeric chain. Both complexes have a trans-trigonal bipyramidal geometry with the three phenyl groups occupying the equatorial plane and two oxygens at axial positions. Both short and long tin–oxygen distances were observed in 1 and 2. In 1, all carboxylates functioned as bridging bidentate ligands, resulting in an infinite 3-D polymer network propagating along all three axes. In 2, Sn1 is bonded to a carboxylate and a water molecule (Sn1–O1 2.145(3)?Å, Sn1–O3 2.341(3)?Å, O1–Sn1–O3 173.97(12)°). Only one carboxylate acts as a bidentate ligand allowing the carbonyl group to be axially coordinated to the adjacent tin, Sn2. Also, Sn2 is covalently bonded to the other carboxylate group in the malonate ligand (Sn2–O4 2.163(3)?Å, Sn2–O5 2.353(3)?Å, O4–Sn2–O5 173.47(12)°). There is a water molecule included in the crystal lattice hydrogen bonded to the uncoordinated carbonyl in malonate.     

The importance of a single methyl group in determining the reaction chemistry of pentamethylcyclopentadienyl cyclooctatetraenyl uranium metallocenes

The steric factors that allow trivalent [(C(5)Me(5))(3)U] (1) to function as a three-electron reductant with C(8)H(8) to form tetravalent [{(C(5)Me(5))(C(8)H(8))U}(2)(μ-C(8)H(8))] (2) have been explored by examining the synthesis and reactivity of the intermediate, "[(C(5)Me(5))(2)(C(8)H(8))U]" (3), and the slightly less crowded analogues, [(C(5)Me(5))(C(5)Me(4)H)(C(8)H(8))U] and [(C(5)Me(4)H)(2)(C(8)H(8))U], that have, successively one less methyl group. The reaction of [{(C(5)Me(5))(C(8)H(8))U(μ-OTf)}(2)] (4; OTf=OSO(2) CF(3)) with two equivalents of KC(5)Me(5) in THF gave ring-opening to "[(C(5)Me(5))(C(8)H(8))U{O(CH(2))(4)(C(5) Me(5))}]" consistent with in situ formation of 3. Reaction of 4 with two and four equivalents of KC(5)Me(4)H generates two equivalents of [(C(5)Me(5))(C(5)Me(4)H)(C(8)H(8))U] (5) and [(C(5)Me(4)H)(2)(C(8)H(8))U] (6), respectively, which in contrast to 3 were isolable. Tetravalent 5 reduces phenazine and PhEEPh (E=S, Se, and Te) to form the tetravalent uranium reduction products, [{(C(5)Me(5))(C(8)H(8))U}(2)(μ-C(12)H(8)N(2))] (7), [{(C(5)Me(5))(C(8)H(8))U}(2)(μ-SPh)(2)] (8), [{(C(5)Me(5))(C(8)H(8))U}(2)(μ-SePh)(2)] (9), and [{(C(5)Me(5))(C(8)H(8))U}(2)(μ-TePh)(2)] (10), consistent with sterically induced reduction. In contrast, the less sterically crowded 6 does not react with these substrates.     

Ethylene/1‐hexene copolymerization with tetramethyldisiloxane‐bridged bis(indenyl) metallocenes

Ethylene/1‐hexene copolymerizations with disiloxane‐bridged metallocenes, rac‐ and meso‐1,1,3,3‐tetramethyldisiloxanediyl‐bis(1‐indenyl)zirconium dichloride (rac‐ 1 , meso‐ 1 ) activated by modified methylaluminoxane were performed to investigate the influence of conformational dynamics on comonomer selectivity. Although ¹H NOESY (nuclear Overhauser and exchange spectroscopy) analysis indicated that the most stable conformation for the meso isomer in solution was that in which both indenes project over the metal coordination site, this isomer showed higher 1‐hexene selectivity in copolymerization (r_e = 140 ± 30, r_h = 0.024 ± 0.004) than the rac isomer with only one indene over the coordination site (r_e = 240 ± 20, r_h = 0.005 ± 0.001). The meso isomer showed high 1‐hexene selectivity, a high product of reactivity ratios (r_er_h = 3.3 ± 0.5) and produced copolymers that could be separated into fractions with different ethylene content suggesting that the active species exhibited multisite behavior and populated conformations with different comonomer selectivities during the copolymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3323–3331, 2004     

Study of ultraviolet photolysis of bis(trichloromethyl)Mercury in the gas phase and in solution

Conclusions The UV photolysis of Hg(CCl₃)₂ in the gas phase at 80°, and in dimethoxyethane solutions at 18°, leads to the respective formation of C₂Cl₆ and HCCl₃ as the main products, which testifies to the predominant free-radical decomposition of the starting molecules involving CCl₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2146–2148, September, 1974.     

The syntheses and structures of bis(alkylimino)isoindolines

In this Letter, we present a synthetic and structural study into bis-imino substituted diiminoisoindolines, which can be synthesized either via CaCl₂ mediated reaction of phthalonitrile with primary amines, or via direct reaction of these amines with unsubstituted diiminoisoindoline. The preferred synthesis does depend on the methodology, and in two cases singly substituted adducts were formed. The single crystal X-ray structures show that, with the exception of the bis-naphthyl compound, the anti conformation is preferred, and that the ionizable hydrogen atom resides on an exocyclic nitrogen rather than the central isoindoline nitrogen atom.     

Synthesis and molecular and extended structures for a diaminonaphthalene-derived bis(amido)stannylene

The cyclic bis(amido)tin(II) compound Sn[1,8-((iPrN)2C10H6] (2) was isolated from the reaction of Li2[1,8-((iPrN)2C10H6] (1) and SnCl2. Solid-state structural analysis of 2 showed it to be a mononuclear species with a pyramidal Sn center as part of a nonplanar metallaheterocycle. The packing diagram of 2 revealed an extended one-dimensional head-to-tail chain structure with short intermolecular Sn/arene-C interactions. Computational examination of 2 (DFT/PW91 and MP2 with 6-31G* and 6-311G** basis functions) indicated that the optimum gas-phase structure of 2,which displays a Sn center in the plane of the naphthyl backbone with a slightly twisted metallaheterocycle, is approximately 24 kcal/mol lower in energy than the X-ray structure. The solid-state geometry of 2 is attributed to the intermolecular donation of the naphthalene pi-electrons to a Lewis acidic Sn center, which leads to the observed supramolecular structure. The crystal structure of 1 is also reported.     

Triplet energy transfer insight in coordination of unsaturated hydrocarbons by d(0) bent metallocenes (Zr, Hf)

For a class of pi-complexes as energy donors, with the use of highly emissive d(0) metallocenes Cp(2)MCl(2) where M = Zr and Hf, it is shown that radiationless triplet energy transfer to unsaturated hydrocarbons in a rigid nonpolar methylcyclohexane (MCH) matrix (where molecular diffusion is absent) obeys the Perrin equation, occurs at radii R(0), being close to the diameter of interacting molecules, and is well described by an electron-exchange resonant (Dexter) mechanism of interaction. Principle correlation between values of the critical radius and a number of C atoms in a linear alpha-olefin is for the first time reported, viz. R(0) (Angstrom) = -2.47 + 1.35n (obtained for systems [Cp(2)HfCl(2) + CnH(2)n + MCH] at 77 K). Pronounced blue shifts (up to 1000 cm(-1)) of low-temperature emission spectra of Cp(2)ZrCl(2) in MCH in the presence of dienes, possessing nonconjugated C=C bonds, are observed, thus suggesting inner-sphere diene coordination. In view of the experimental data, inner- and outer-sphere coordinative interaction between the components of catalytic systems for polymerization (d(0) metallocene precatalysts and alkenes and dienes) is rationalized.     

Surfactant self-assembly in the gas phase: bis(2-ethylhexyl)sulfosuccinate-alkaline metal ion aggregates

The coating effect of alkali metal salt clusters by the surfactant anion bis(2-ethylhexyl)sulfosuccinate has been investigated by electrospray ionization mass spectrometry (MS) and MS/MS. The analysis of the data emphasized the formation and stability in the gas phase of reverse micelle-like surfactant aggregates carrying in their interior ionic clusters. Two main contributions have been postulated to account for the observed stability: intra-aggregate electrostatic interactions and screening of inter-aggregate attractive interactions due to the exclusion volume effect caused by the surfactant alkyl chains. Moreover, the stability and structural arrangement of these supramolecular aggregates result in strong dependency on the alkali metal salt identity.