Tetra-n-butyl­ammonium bromide: a redetermination at 150 K addressing the merohedral twinning

The redetermined, low temperature (150 K), structure of tetra-n-butyl­ammonium bromide, (C4H9)4N+·Br−, has been found to be merohedrally twinned via twin law −1 0 0, 0 − 1 0, 1 0 1. The structure was previously determined, with low precision, no inclusion of H atoms and only the bromide ion refined with anisotropic displacement parameters, by Wang et al. (1995 ▶). Mol. Cryst. Liq. Cryst. Sci. Tech. A, 264, 115–129. The redetermined structure has considerably improved precision in all geometrical parameters, has all non-H atoms refined anisotropically, H atoms included, and is isomorphous with the iodide analogue. The structure is otherwise routine, with the shortest cation to anion contacts being between the bromide anion and the CH atoms close to the ammonium nitro­gen centre at a distance of ca. 2.98–3.11 Å. Each anion makes eight such contacts to four different anions. The n-butyl chains are fully extended, adopting an all-anti conformation with approximate S 4 point symmetry

Molybdenum complexes derived from the oxydianiline [(2-NH₂C₆H₄)₂O] : synthesis, characterization and ε-caprolactone ROP capability

The reaction of Na₂MoO₄ with 2,2′-oxydianiline (2-aminophenylether), (2-NH₂C₆H₄)₂O, LH₄, in DME (DME = 1,2-dimethoxyethane) in the presence of Et₃N and Me₃SiCl afforded either the bis(imido) molybdenum(VI) complex {Mo(L)Cl₂(DME)} (1), where L = (2-NC₆H₄)₂O, or the molybdenum(V) salt [Mo(L′)Cl₄][Et₃NH] (2), where L′ = [(2-NH₂C₆H₄)(2-NC₆H₄)O], depending on the work-up method employed. The same diamine reacted with in situ [Mo(NtBu)₂Cl₂(DME)] afforded a tetra-nuclear complex [Mo₄Cl₃(NtBu)₃(OSiMe₃)(μ₄-O)(L)₂(L′)₂]·2MeCN (3·2MeCN). The crystal structures of 1, 2 and 3·2MeCN have been determined. The structure of the bis(imido) complex 1 contains two unique molecules paired up via weak π-stacking, whereas the structure of 2 contains a chelating amine/imido ligand, and is made up of discrete units of two cations and two anions which are interacting via H-bonding. The tetra-nuclear structure 3 contains four different types of distorted octahedral molybdenum centre, and a bent Me₃SiO group thought to originate from the precursor synthesis. Complexes 1–3 have been screened for their ability to ring open polymerize (ROP) ε-caprolactone. For 1 and 3 (not 2), conversion rates were good (>90%) at high temperatures (100 °C) over 6–24 h, and the polymerization proceeded in a living manner

Ring opening polymerization of lactides and lactones by multimetallic alkyl zinc complexes derived from the acids Ph₂C(X)CO₂2H (X = OH, NH₂ )

The reaction of the dialkylzinc reagents R₂Zn with the acids 2,2-Ph₂C(X)(CO₂H), where X = NH₂, OH, i.e. 2,2′-diphenylglycine (dpgH) or benzilic acid (benzH2), in toluene at reflux temperature afforded the tetra-nuclear ring complexes [RZn(dpg)]₄, where R = Me (1), Et (2), 2-CF₃C₆H₄ (3), and 2,4,6-F₃C₆H₂ (4); complex 2 has been previously reported. The crystal structures of 1·(2MeCN), 3 and 4·(4(C₇H₈)·1.59(H₂O)) are reported, along with that of the intermediate compound (2-CF₃C₆H₄)3B·MeCN and the known compound [ZnCl₂(NCMe)₂]. Complexes 1–4, together with the known complex [(ZnEt)₃(ZnL)₃(benz)₃] (5; L = MeCN), have been screened, in the absence of benzyl alcohol, for their potential to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and rac-lactide (rac-LA); the co-polymerization of ε-CL with rac-LA was also studied. Complexes 3 and 4 bearing fluorinated aryls at zinc were found to afford the highest activities

Zinc calixarene complexes for the ring opening polymerization of cyclic esters

Reaction of Zn(C₆F₅)₂·toluene (two equivalents) with 1,3-dipropoxy-p-tert-butyl-calix[4]arene (L¹H₂) led to the isolation of the complex [{Zn(C₆F₅)}₂L¹] (1), whilst similar use of Zn(Me)₂ resulted in the known complex [{Zn(Me)}₂L¹] (2). Treatment of L¹H₂ with in situ prepared Zn{N(SiMe₃)₂}₂ in refluxing toluene led to the isolation of the compound [(Na)ZnN(SiMe₃)₂L¹] (3). The stepwise reaction of L¹H₂ and sodium hydride, followed by ZnCl₂ and finally NaN(SiMe₃)₂ yielded the compound [Zn{N(SiMe₃)₂}₂L¹] (4). The reaction between three equivalents of Zn(C₆F₅)₂·toluene and oxacalix[3]arene (L²H₃) at room temperature formed the compound {[Zn(C₆F₅)]₃L²} (5); heating of 5 in acetonitrile caused the ring opening of the parent oxacalix[3]arene and rearrangement to afford the complex [(L²)Zn₆(C₆F₅)(R)(RH)OH]·5MeCN R = C₆F₅CH₂-(p-ᵗBuPhenolate-CH₂OCH₂–)₂–p-ᵗBuPhenolate-CH₂O⁻)³⁻ (6). The molecular structures of the new complexes 1, 3 and 6, together with that of the known complex 2, whose solid state structure has not previously been reported, have been determined. Compounds 1, 3–5 have been screened for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and rac-lactide. Compounds featuring a Zn–C₆F₅ fragment were found to be poor ROP pre-catalysts as they did not react with benzyl alcohol to form an alkoxide. By contrast, compound 4, which contains a zinc silylamide linkage, was the most active of the zinc-based calix[4]arene compounds screened and was capable of ROP at ambient temperature with 65% conversion over 4 h

Vanadium(V) tetra-phenolate complexes: synthesis, structural studies and ethylene homo-(co-)polymerization capability

Reaction of α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xylene (p-L¹H₄) with two equivalents of [VO(OR)₃] (R = nPr, tBu) in refluxing toluene afforded, after work-up, the complexes {[VO(OnPr)(THF)]₂ (μ-p-L¹)}·2(THF) (1·2(THF)) or {[VO(OtBu)]₂ (μ-p-L¹)}·2MeCN (2·2MeCN), respectively in moderate to good yield. A similar reaction using the meta pro-ligand, namely α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-m-xylene (m-L²H₄) afforded the complex {[VO(OnPr)(THF)]₂ (μ-p-L²)} (3). Use of [V(Np-R¹C₆H₄)(tBuO)₃] (R¹ = Me, CF₃) with p-L¹H₄ led to the isolation of the oxo–imido complexes {[VO(tBuO)][V(Np-R¹C₆H₄) (tBuO)](μ-p-L¹)} (R¹ = Me, 4·CH2Cl₂; CF₃, 5·CH2Cl₂), whereas use of [V(Np-R¹C₆H₄)CL³] (R¹ = Me, CF₃) in combination with Et₃N/p-L¹H₄ or p-L¹Na₄ afforded the diimido complexes {[V(Np-MeC₆H₄)(THF)Cl]₂ (μ-p-L¹)}·4toluene (6·4toluene) or {[V(Np-CF₃C₆H₄)(THF)Cl]₂ (μ-p-L¹)} (7). For comparative studies, the complex [(VO)(μ-OnPr)L³]₂ (8) has also been prepared via the interaction of [VO(nPrO)₃] and 2-(α-(2-hydroxy-3,5-di-tert-butylphenyl)benzyl)-4,6-di-tert-butylphenol (L³H2). The crystal structures of 1·2THF, 2·2MeCN, 3, 4·CH2Cl₂, 5·CH2Cl₂, 6·4toluene·THF, 7 and 8 have been determined. Complexes 1–3 and 5–8 have been screened as pre-catalysts for the polymerization of ethylene in the presence of a variety of co-catalysts (with and without a re-activator), including DMAC (dimethylaluminium chloride), DEAC (diethylaluminium chloride), EADC (ethylaluminium dichloride) and EASC (ethylaluminium sesquichloride) at various temperatures and for the co-polymerization of ethylene with propylene; results are compared versus the benchmark catalyst [VO(OEt)Cl₂]. In some cases, activities as high as 243 400 g mmol⁻¹ V⁻¹ h⁻¹ (30.43 kgPE mmol V⁻¹ h⁻¹ bar⁻¹) were achievable, whilst it also proved possible to obtain higher molecular weight polymers (in comparable yields to the use of [VO(OEt)Cl₂]). In all cases with dimethylaluminium chloride (DMAC)/ethyltrichloroacetate (ETA) activation, the activities achieved surpassed those of the benchmark catalyst. In the case of the co-polymerization of ethylene with propylene, complexes 1–3 and 5–8 showed comparable or higher molecular weight than [VO(OEt)Cl₂] with comparable catalytic activities or higher in the case of the imido complexes 6 and 7

Organoaluminium complexes derived from Anilines or Schiff bases for ring opening polymerization of epsilon-caprolactone, delta-valerolactone and rac-lactide

Reaction of R¹R²CHN=CH(3,5-tBu₂C₆H₂-OH-2) (R¹ = R² = Me L¹H; R¹ = Me, R² = Ph L²H; R¹ = R2 = Ph L³H) with one equivalent of R³3Al (R³ = Me, Et) afforded [(L¹-³)AlR³₂] (L¹, R³ = Me 1, R³ = Et 2; L², R³ = Me 3, R³ = Et 4; L³ R³ = Me 5, R³ = Et 6); complex 1 has been previously reported. Use of the N,O-ligand derived from 2,2/-diphenylglycine afforded either 5 or a by-product [Ph₂NCH₂(3,5-tBu₂C₆H₂-O-2)AlMe₂] (7). The known Schiff base complex [2-Ph₂PC₆H4CH₂(3,5-tBu₂C₃H₂-O-2)AlMe₂] (8) and the product of the reaction of 2-diphenylphosphinoaniline 1-NH₂,2-PPh₂C₆H4 with Me3Al, namely {Ph₂PC₆H4N[(Me₂Al)₂mu-Me](mu-Me₂Al)} (9) were also isolated. For structural and catalytic comparisons, complexes resulting from interaction of Me₃Al with diphenylamine or benzhydrylamine, namely {Ph₂N[(Me₂Al)2mu-Me]} (10) and [Ph₂CHNH(mu-Me₂Al)]₂·MeCN (11), were prepared. The molecular structures of the Schiff pro-ligands derived from Ph₂CHNH₂ and 2,2/-Ph2C(CO₂H)(NH₂), together with complexes 5, 7 and 9 - 11·MeCN were determined. All complexes have been screened for their ability to ring opening polymerization (ROP) epsilon-caprolactone, delta-valerolactone or rac-lactide, in the presence of benzyl alcohol, with or without solvent present. The co-polymerization of epsilon-caprolactone with rac-lactide has also been studied

Vanadium(V) oxo and imido calix[8]arene complexes: synthesis, structural studies, and ethylene homo/copolymerisation capability

Interaction of p-tert-butylcalix[8]areneH₈ (L⁸H₈) with in-situ generated [NaVO(Ot-Bu)₄] (from VOCl₃ and four equivalents of NaOtBu) afforded the dark brown complex [Na(NCMe)₅][(VO)₂L⁸H]·4MeCN (1·4MeCN), in which the calix[8]arene adopts a saddle-shaped conformation. Increasing (to four equivalents per L⁸) the amount of [NaVO(Ot-Bu)₄] present in the reaction, led to the formation of the yellow octa-vanadyl complex {[(Na(VO)₄L⁸)(Na(NCMe))₃] [Na(NCMe)₆}₂·10MeCN (2·10MeCN), in which the calix[8]arene adopts a pleated loop conformation. In the presence of adventitious oxygen, reaction of four equivalents of [VO(Ot-Bu)₃] (generated from VOCl₃ and 3KOtBu) with L⁸H₈ afforded the alkali-metal free green complex [(VO)₄L⁸(μ³-O)₂] (3); the solvates 3·3MeCN and 3·3CH₂Cl₂ have been isolated. In both solvates, the L⁸ ligand adopts a shallow saddle-shaped conformation, supporting a core comprising of a (VO)₄O₄ ladder. In the case of lithium, in order to obtain crystalline material, it was found necessary to reverse the order of addition such that lithium tert-butoxide was added to L⁸H₈, and then subsequently treated (at –78 ⁰C) with two equivalents of VOCl₃; crystallization from tetrahydrofuran (THF) afforded {(VO₂)₂Li₆[L⁸](thf)₂(OtBu)₂(Et₂O)₂}·Et₂O (4·Et₂O). In the structure of 4·Et₂O, vanadium, lithium and oxygen form a central lattern-type cage, which is capped top and bottom by an Li₂O₂2 diamond; the calix[8]arene is in a ‘down, down, out, out, down, down’ conformation. When the ‘same reaction’ was extracted into acetonitrile (MeCN), the salt complex [Li(NCMe)₄][(VO)₂L⁸H]·8MeCN (5.8MeCN) was formed. In 5·8MeCN, the [Li(NCMe)₄] cations reside between the anions in the clefts of L⁸H, the latter adopting a saddle-shaped conformation. Use of the imido precursors [V(Nt-Bu)(Ot-Bu)₃] and [V(Np-tolyl)(Ot-Bu)₃] and L⁸H₈, afforded, via an imido exchange, the salt [t-BuNH₃]{[V(p-tolylN)]₂L⁸H}·3½MeCN (6·3½MeCN). The molecular structures of 1 to 6 are reported; data collections for complexes 2·10MeCN, 3·3MeCN and 3·3CH₂Cl₂ required the use of synchrotron radiation. Complexes 1, 3 and 4 have been screened as pre-catalysts for the polymerization of ethylene in the presence of a variety of co-catalysts (with and without a re-activator) at various temperatures and for the co-polymerization of ethylene with propylene; results are compared versus the benchmark catalyst VO(OEt)Cl₂. In some cases, activities as high as 136,000 g/mmol.v.h were achievable, whilst it also proved possible to obtain higher molecular weight polymers (in comparible yields) versus the use of VO(OEt)Cl₂. In the case of the co-polymerization, the incorporation of propylene was 7.1 – 10.9 mol% (cf 10 mol% for VO(OEt)Cl₂), though catalytic activities were lower versus VO(OEt)Cl₂

A hexahomotrioxacalix[3]arene-based ditopic receptor for alkylammonium ions controlled by Ag + ions 4

A receptor cone-1 based on a hexahomotrioxacalix[3]arene bearing three pyridyl groups 21 was successfully synthesized, which has a C3-symmetric conformation and is capable of binding 22 alkylammonium and metal ions simultaneously in a cooperative fashion. It can bind 23 alkylammonium ions through the -cavity formed by three aryl rings. This behaviour is consistent 24 with the cone-in/cone-out conformational rearrangement needed to reorganize the cavity for 25 endo-complexation. As a C3-symmetrical pyridyl-substituted calixarene, receptor cone-1 can also 26 bind a Ag + ion and the nitrogen atoms are turned towards the inside of the cavity and interact with 27 Ag +. After complexation of tris(2-pyridylamide) derivative receptor cone-1 with Ag + , the original 28 C3-symmetry was retained and higher complexation selectivity for n-BuNH3 + versus t-BuNH3 + was 29 observed. Thus, it is believed that this receptor will have a role to play in the sensing, detection, and 30 recognition of Ag + and n-BuNH3 + ions. 3

N-(4-Methoxy­phen­yl)-tert-butane­sulfinamide

In the title compound, C11H17NO2S, the mol­ecules inter­act head-to-tail through N—H⋯OS hydrogen bonds, giving discrete centrosymmetric cyclic dimers. The N—Car­yl bond length [1.4225 (14) Å] is inter­mediate between that in N-phenyl-tert-butane­sulfinamide [1.4083 (12) Å] and the N—Calk­yl bond lengths in N-alkyl­alkanesulfinamides (1.470–1.530 Å), suggesting weaker delocalization of electrons over the N atom and the aromatic ring due to the presence of the 4-meth­oxy group

Multimetallic lithium complexes derived from the acids Ph₂C(X)CO₂H (X = OH, NH₂) : synthesis, structure and ring opening polymerization of lactides and lactones

Reaction of LiOR (R=t-Bu, Ph) with the acids 2,2/-Ph₂C(X)(CO₂H), X=OH (benzH), NH₂ (dpgH) was investigated. For benzH, one equivalent LiOt-Bu in THF afforded [Li(benz)]2⋅2THF (1⋅2THF), which adopts a 1D chain structure. If acetonitrile is used (mild conditions), another polymorph of 1 is isolated; LiOPh also led to 1. Robust work-up afforded [Li₇(benz)₇(MeCN)] 2MeCN THF (2⋅2MeCN⋅THF). Use of LiOt-Bu (2 equivalents) led to {Li₈(Ot-Bu)₂[(benz)](OCPh₂CO₂CPh₂CO2t-Bu)₂(THF)₄} (3), the core of which comprises two open cubes linked by benz ligands. For dpgH, two equivalents of LiOt-Bu in THF afforded [Li6(Ot-Bu)₂(dpg)₂(THF)₂] (4), which contains an Li₂Ov 6-step ladder. Similar reaction of LiOPh afforded [Li₈(PhO)₄(dpg)₄(MeCN)₄] (5). Complexes 1–5 were screened for their potential as catalysts for ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL), rac-lactide (rac-LA) and δ-valerolactone (δ-VL). For ROP of ϵ-CL, conversions > 70 % were achievable at 110 °C with good control. For rac-LA and δ-VL, temperatures of at least 110 °C over 12 h were necessary for activity (conversions > 60 %). Systems employing 2 were inactiv