Crystalline Micro-Sized Carbonated Apatites: Chemical Anisotropy of the Crystallite Surfaces, Biocompatibility, Osteoconductivity, and Osteoinductive Effect Enhanced by Poly(ethylene phosphoric acid).

Carbonated hydroxyapatites (CAp) are very close to natural bone apatite in chemical composition and are regarded as a prospective bone mineral substitute for bone surgery and orthopedics. However, until now, the studies and applications of CAp were limited because of the amorphous nature of the synthetic CAp. In the present work, microsized highly crystalline carbonated apatites with uniform hexagonal (hCAp) or platelike (pCAp) morphology have been studied for the first time in vitro and in vivo, comparing against commercial hydroxyapatite (HAp) and ß-tricalcuim phosphate (ßTCP). In vitro experiments on dissolution of those calcium phosphate ceramics (CPCs) in acetate (pH 5.5) and Tris (pH 7.3) buffer solutions showed the following rank order of the dissolution rates: ßTCP > hCAp > pCAp > HAp. The higher dissolution rate of hCAp in comparison with pCAp is explained by chemical anisotropy of the crystallite surfaces, which was proven by SEM studies of the changes in the morphology of hCAp and pCAp crystallites during hydrolysis. A 5-week experiment on subcutaneous implantation of CPC species showed the following rank order of bioresorption rates: ßTCP > pCAp > hCAp > HAp. pCAp matrixes exhibited the highest biocompatibility, confirmed by histomorphological analysis. Three-month bone regeneration experiments involving a rat tibial defect model were conducted with 250-500 µm granules of pCAp and pCAp-PEPA [pCAp, pretreated with 2 wt % poly(ethylene phosphoric acid)]. Notably, pCAp-PEPA implants were resorbed at higher rates and induced the formation of more mature osseous tissue, a compact bone with Haversian systems.

Polyisobutylenes with Controlled Molecular Weight and Chain-End Structure: Synthesis and Actual Applications.

The polymerization of isobutylene allows us to obtain a wide spectrum of polyisobutylenes (PIBs) which differ in their molecular weight characteristics and the chemical structure of chain-end groups. The bulk of the PIBs manufactured worldwide are highly reactive polyisobutylenes (HRPIBs) with -C(Me)=CH2 end-groups and low-molecular weights (Mn < 5 kDa). HRPIBs are feedstocks that are in high demand in the manufacturing of additives for fuels and oils, adhesives, detergents, and other fine chemicals. In addition, HRPIBs and CMe2Cl-terminated PIBs are intensively studied with the aim of finding biomedical applications and for the purpose of developing new materials. Both chain control (molecular weight and dispersity) and chemoselectivity (formation of exo-olefinic or -CMe2Cl groups) should be achieved during polymerization. This review highlights the fundamental issues in the mechanisms of isobutylene polymerization and PIB analysis, examines actual catalytic approaches to PIBs, and describes recent studies on the functionalization and applications of HRPIBs and halogen-terminated PIBs.

Dispersant and Protective Roles of Amphiphilic Poly(ethylene phosphate) Block Copolymers in Polyester/Bone Mineral Composites.

Composites of synthetic bone mineral substitutes (BMS) and biodegradable polyesters are of particular interest for bone surgery and orthopedics. Manufacturing of composite scaffolds commonly uses mixing of the BMS with polymer melts. Melt processing requires a high homogeneity of the mixing, and is complicated by BMS-promoted thermal degradation of polymers. In our work, poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites reinforced by commercial ß-tricalcium phosphate (ßTCP) or synthesized carbonated hydroxyapatite with hexagonal and plate-like crystallite shapes (hCAp and pCAp, respectively) were fabricated using injection molding. pCAp-based composites showed advanced mechanical and thermal characteristics, and the best set of mechanical characteristics was observed for the PLLA-based composite containing 25 wt% of pCAp. To achieve compatibility of polyesters and pCAp, reactive block copolymers of PLLA or PCL with poly(tert-butyl ethylene phosphate) (C1 and C2, respectively) were introduced to the composite. The formation of a polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer during composite preparation, followed by chemical binding of PEPA with pCAp, have been proved experimentally. The presence of 5 wt% of the compatibilizer provided deeper homogenization of the composite, resulting in a marked increase in strength and moduli as well as a more pronounced nucleation effect during isothermal crystallization. The use of C1 increased the thermal stability of the PLLA-based composite, containing 25 wt% of pCAp. In view of positive impacts of polyester-b-PEPA on composite homogeneity, mechanical characteristics, and thermal stability, polyester-b-PEPA will find application in the further development of composite materials for bone surgery and orthopedics.

Chain-End Functionalization of Poly(ε-caprolactone) for Chemical Binding with Gelatin: Binary Electrospun Scaffolds with Improved Physico-Mechanical Characteristics and Cell Adhesive Properties.

Composite biocompatible scaffolds, obtained using the electrospinning (ES) technique, are highly promising for biomedical application thanks to their high surface area, porosity, adjustable fiber diameter, and permeability. However, the combination of synthetic biodegradable (such as poly(ε-caprolactone) PCL) and natural (such as gelatin Gt) polymers is complicated by the problem of low compatibility of the components. Previously, this problem was solved by PCL grafting and/or Gt cross-linking after ES molding. In the present study, composite fibrous scaffolds consisting of PCL and Gt were fabricated by the electrospinning (ES) method using non-functionalized PCL1 or NHS-functionalized PCL2 and hexafluoroisopropanol as a solvent. To provide covalent binding between PCL2 and Gt macromolecules, NHS-functionalized methyl glutarate was synthesized and studied in model reactions with components of spinning solution. It was found that selective formation of amide bonds, which provide complete covalent bonding of Gt in PCL/Gt composite, requires the presence of weak acid. With the use of the optimized ES method, fibrous mats with different PCL/Gt ratios were prepared. The sample morphology (SEM), hydrolytic resistance (FT-IR), cell adhesion and viability (MTT assay), cell penetration (fluorescent microscopy), and mechanical characteristics of the samples were studied. PCL2-based films with a Gt content of 20 wt% have demonstrated the best set of properties.

Tandem Synthesis of Ultra-High Molecular Weight Drag Reducing Poly-α-Olefins for Low-Temperature Pipeline Transportation.

Ultra-high molecular weight poly-α-olefins are widely used as drag reducing agents (DRAs) for pipeline transportation of oil and refined petroleum products. The synthesis of polyolefin DRAs is based on low-temperature Ziegler-Natta (ZN) polymerization of higher α-olefins. 1-Hexene based DRAs, the most effective at room temperature, typically lose DR activity at low temperatures. The use of 1-hexene copolymers with C8-C12 linear α-olefins appears to offer a solution to the problem of low-temperature drag reducing. The present work aims to develop two-stage synthesis of polyolefin DRAs that is based on selective oligomerization of ethylene in the presence of efficient chromium/aminodiphosphine catalysts (Cr-PNP), followed by polymerization of the olefin mixtures, formed at oligomerization stage, using efficient titanium-magnesium ZN catalyst. We have shown that oligomerization of ethylene in α-olefin reaction media proceeds faster than in saturated hydrocarbons, providing the formation of 1-hexene, 1-octene, and branched C10 and C12 olefins; the composition and the ratio of the reaction products depended on the nature of PNP ligand. Oligomerizates were used in ZN polymerization 'as is', without additional treatment. Due to branched character of C10+ hydrocarbons, formed during oligomerization of ethylene, resulting polyolefins demonstrate higher low-temperature DR efficiency at low polymer concentrations (~1 ppm) in comparison with benchmark polymers prepared from the mixtures of linear α-olefins and from pure 1-hexene. We assume that faster solubility and more efficient solvation of the polyolefins, prepared using 'tandem' ethylene-based process, represent an advantage of these type polymers over conventional poly(1-hexene) and linear α-olefin-based polymers when used as 'winter' DRAs.

Antibacterial Poly(ε-CL)/Hydroxyapatite Electrospun Fibers Reinforced by Poly(ε-CL)-b-poly(ethylene phosphoric acid).

In bone surgery and orthopedics, bioresorbable materials can be helpful in bone repair and countering post-op infections. Explicit antibacterial activity, osteoinductive and osteoconductive effects are essential to achieving this objective. Nonwoven electrospun (ES) fibers are receiving the close attention of physicians as promising materials for wound dressing and tissue engineering; potentially, in high contrast with dense materials, ES mats hamper regeneration of the bone extracellular matrix to a lesser extent. The use of the compositions of inherently biodegradable polyesters (poly(ε-caprolactone) PCL, poly(lactoglycolide), etc.), calcium phosphates and antibiotics is highly prospective, but the task of forming ES fibers from such compositions is complicated by the incompatibility of the main organic and inorganic ingredients, polyesters and calcium phosphates. In the present research we report the synthesis of hydroxyapatite (HAp) nanoparticles with uniform morphology, and demonstrate high efficiency of the block copolymer of PCL and poly(ethylene phosphoric acid) (PEPA) as an efficient compatibilizer for PCL/HAp mixtures that are able to form ES fibers with improved mechanical characteristics. The materials obtained in the presence of vancomycin exhibited incremental drug release against Staphylococcus aureus (St. aureus).

Functionalized Biodegradable Polymers via Termination of Ring-Opening Polymerization by Acyl Chlorides.

Aliphatic polyesters are an important class of polymeric materials for biomedical applications due to their versatile and tunable chemistry, biocompatibility and biodegradability. A capability of direct bonding with biomedically significant molecules, provided by the presence of the reactive end functional groups (FGs), is highly desirable for prospective polymers. Among FGs, N-hydroxysuccinimidyl activated ester group (NHS) and maleimide fragment (MI) provide efficient covalent bonding with -NH- and -SH containing compounds. In our study, we found that NHS- and MI-derived acyl chlorides efficiently terminate living ring-opening polymerization of ε-caprolactone, L-lactide, ethyl ethylene phosphonate and ethyl ethylene phosphate, catalyzed by 2,6-di-tert-butyl-4-methylphenoxy magnesium complex, with a formation of NHS- and MI-functionalized polymers at a high yields. Reactivity of these polymers towards amine- and thiol-containing model substrates in organic and aqueous media was also studied.

In Vitro and In Vivo Studies of Biodegradability and Biocompatibility of Poly(εCL)-b-Poly(EtOEP)-Based Films.

The control of surface bioadhesive properties of the subcutaneous implants is essential for the development of biosensors and controlled drug release devices. Poly(alkyl ethylene phosphate)-based (co)polymers are structurally versatile, biocompatible and biodegradable, and may be regarded as an alternative to poly(ethylene glycol) (PEG) copolymers in the creation of antiadhesive materials. The present work reports the synthesis of block copolymers of ε-caprolactone (εCL) and 2-ethoxy-1,3,2-dioxaphospholane-2-oxide (ethyl ethylene phosphate, EtOEP) with different content of EtOEP fragments, preparation of polymer films, and the results of the study of the impact of EtOEP/εCL ratio on the hydrophilicity (contact angle of wetting), hydrolytic stability, cytotoxicity, protein and cell adhesion, and cell proliferation using umbilical cord multipotent stem cells. It was found that the increase of EtOEP/εCL ratio results in increase of hydrophilicity of the polymer films with lowering of the protein and cell adhesion. MTT cytotoxicity test showed no significant deviations in toxicity of poly(εCL) and poly(εCL)-b-poly(EtOEP)-based films. The influence of the length of poly(EtOEP)chain in block-copolymers on fibrotic reactions was analyzed using subcutaneous implantation experiments (Wistar line rats), the increase of the width of the fibrous capsule correlated with higher EtOEP/εCL ratio. However, the copolymer-based film with highest content of polyphosphate had been subjected to faster degradation with a formation of developed contact surface of poly(εCL). The rate of the degradation of polyphosphate in vivo was significantly higher than the rate of the degradation of polyphosphate in vitro, which only confirms an objective value of in vivo experiments in the development of polymer materials for biomedical applications.

Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization.

The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(µ-butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO:κO')di-µ-hydroxido-bis[(butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO)(butyl 2,6-di-tert-butyl-4-methylphenyl phosphato-κO)chromium](Cr-Cr) heptane disolvate or {Cr2(µ2-OH)2[µ2-PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO:κO']2[PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2[HOPO(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2}·2C7H16, [Cr2(C19H32O4P)4(C19H33O4P)2(OH)2]·2C7H16, denoted (1)·2(heptane), [µ-bis(2,6-diisopropylphenyl) phosphato-1κO:2κO']bis[bis(2,6-diisopropylphenyl) phosphato]-1κO,2κO-chlorido-2κCl-triethanol-1κ2O,2κO-di-µ-ethanolato-1κ2O:2κ2O-dichromium(Cr-Cr) ethanol monosolvate or {Cr2(µ2-OEt)2[µ2-PO2(O-2,6-iPr2-C6H3)2-κO:κO'][PO2(O-2,6-iPr2-C6H3)2-κO]2Cl(EtOH)3}·EtOH, [Cr2(C2H5O)2(C24H34O4P)3Cl(C2H6O)3]·C2H6O, denoted (2)·EtOH, and di-µ-ethanolato-1κ2O:2κ2O-bis{[bis(2,6-diisopropylphenyl) hydrogen phosphato-κO][bis(2,6-diisopropylphenyl) phosphato-κO]chlorido(ethanol-κO)chromium}(Cr-Cr) benzene disolvate or {Cr2(µ2-OEt)2[PO2(O-2,6-iPr2-C6H3)2-κO]2[HOPO(O-2,6-iPr2-C6H3)2-κO]2Cl2(EtOH)2}·2C6H6, [Cr2(C2H5O)2(C24H34O4P)2(C24H35O4P)2Cl2(C2H6O)2]·2C6H6, denoted (3)·2C6H6. Complexes (1)-(3) have been synthesized by an exchange reaction between the in-situ-generated corresponding lithium or potassium disubstituted phosphates with CrCl3(H2O)6 in ethanol. The subsequent crystallization of (1) from heptane, (2) from ethanol and (3) from an ethanol/benzene mixture allowed us to obtain crystals of (1)·2(heptane), (2)·EtOH and (3)·2C6H6, whose structures have the monoclinic P21, orthorhombic P212121 and triclinic P-1 space groups, respectively. All three complexes have binuclear cores with a single Cr-Cr bond, i.e. Cr2O6P2 in (1), Cr2PO4 in (2) and Cr2O2 in (3), where the Cr atoms are in distorted octahedral environments, formally having 16 e per Cr atom. The complexes have bridging ligands µ2-OH in (1) or µ2-OEt in (2) and (3). The organophosphate ligands demonstrate terminal κO coordination modes in (1)-(3) and bridging µ2-κO:κO' coordination modes in (1) and (2). All the complexes exhibit hydrogen bonding: two intramolecular Ophos...H-Ophos interactions in (1) and (3) form two {H[PO2(OR)2]2} associates; two intramolecular Cl...H-OEt hydrogen bonds additionally stabilize the Cr2O2 core in (3); two intramolecular Ophos...H-OEt interactions and two O...H-O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in (2)·EtOH. The presence of both basic ligands (OH- or OEt-) and acidic [H(phosphate)2]- associates at the same metal centres in (1) and (3) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short-chain branching. The formation of a small amount of α-olefins has been detected in this reaction.

A New Approach to Developing Long-Acting Injectable Formulations of Anti-HIV Drugs: Poly(Ethylene Phosphoric Acid) Block Copolymers Increase the Efficiency of Tenofovir against HIV-1 in MT-4 Cells.

Despite the world's combined efforts, human immunodeficiency virus (HIV), the causative agent of AIDS, remains one of the world's most serious public health challenges. High genetic variability of HIV complicates the development of anti-HIV vaccine, and there is an actual clinical need for increasing the efficiency of anti-HIV drugs in terms of targeted delivery and controlled release. Tenofovir (TFV), a nucleotide-analog reverse transcriptase inhibitor, has gained wide acceptance as a drug for pre-exposure prophylaxis or treatment of HIV infection. In our study, we explored the potential of tenofovir disoproxil (TFD) adducts with block copolymers of poly(ethylene glycol) monomethyl ether and poly(ethylene phosphoric acid) (mPEG-b-PEPA) as candidates for developing a long-acting/controlled-release formulation of TFV. Two types of mPEG-b-PEPA with numbers of ethylene phosphoric acid (EPA) fragments of 13 and 49 were synthesized by catalytic ring-opening polymerization, and used for preparing four types of adducts with TFD. Antiviral activity of [mPEG-b-PEPA]TFD or tenofovir disoproxil fumarate (TDF) was evaluated using the model of experimental HIV infection in vitro (MT-4/HIV-1IIIB). Judging by the values of the selectivity index (SI), TFD exhibited an up to 14-fold higher anti-HIV activity in the form of mPEG-b-PEPA adducts, thus demonstrating significant promise for further development of long-acting/controlled-release injectable TFV formulations.

Different coordination modes of trans-2-{[(2-methoxyphenyl)imino]methyl}phenoxide in rare-earth complexes: influence of the metal cation radius and the number of ligands on steric congestion and ligand coordination modes.

A simple and effective synthetic route to homo- and heteroleptic rare-earth (Ln = Y, La and Nd) complexes with a tridentate Schiff base anion has been demonstrated using exchange reactions of rare-earth chlorides with in-situ-generated sodium (E)-2-{[(2-methoxyphenyl)imino]methyl}phenoxide in different molar ratios in absolute methanol. Five crystal structures have been determined and studied, namely tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato-κ3O1,N,O2)lanthanum, [La(C14H12NO2)3], (1), tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato-κ3O1,N,O2)neodymium tetrahydrofuran disolvate, [La(C14H12NO2)3]·2C4H8O, (2)·2THF, tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato)-κ3O1,N,O2;κ3O1,N,O2;κ2N,O1-yttrium, [Y(C14H12NO2)3], (3), dichlorido-1κCl,2κCl-µ-methanolato-1:2κ2O:O-methanol-2κO-(µ-2-{[(2-methoxyphenyl)imino]methyl}phenolato-1κ3O1,N,O2:2κO1)bis(2-{[(2-methoxyphenyl)imino]methyl}phenolato)-1κ3O1,N,O2;2κ3O1,N,O2-diyttrium-tetrahydrofuran-methanol (1/1/1), [Y2(C14H12NO2)3(CH3O)Cl2(CH4O)]·CH4O·C4H8O, (4)·MeOH·THF, and bis(µ-2-{[(2-methoxyphenyl)imino]methyl}phenolato-1κ3O1,N,O2:2κO1)bis(2-{[(2-methoxyphenyl)imino]methyl}phenolato-2κ3O1,N,O2)sodiumyttrium chloroform disolvate, [NaY(C14H12NO2)4]·2CHCl3, (5)·2CHCl3. Structural peculiarities of homoleptic tris(iminophenoxide)s (1)-(3), binuclear tris(iminophenoxide) (4) and homoleptic ate tetrakis(iminophenoxide) (5) are discussed. The nonflat Schiff base ligand displays µ2-κ3O1,N,O2:κO1 bridging, and κ3O1,N,O2 and κ2N,O1 terminal coordination modes, depending on steric congestion, which in turn depends on the ionic radii of the rare-earth metals and the number of coordinated ligands. It has been demonstrated that interligand dihedral angles of the phenoxide ligand are convenient for comparing steric hindrance in complexes. (4)·MeOH has a flat Y2O2 rhomboid core and exhibits both inter- and intramolecular MeO-H...Cl hydrogen bonding. Catalytic systems based on complexes (1)-(3) and (5) have demonstrated medium catalytic performance in acrylonitrile polymerization, providing polyacrylonitrile samples with narrow polydispersity.

[Bis(2,6-diiso-propyl-phen-yl) phosphato-κO]pentakis-(methanol-κO)manganese bis-(2,6-diiso-propyl-phen-yl) phosphate methanol tris-olvate.

The title compound, [Mn(C24H34O4P)(CH3OH)5](C24H34O4P)·3CH3OH, was formed in the reaction between a hydrate of a manganese(II) salt [either Mn(NO3)2(H2O)6 or MnCl2(H2O)4] with a methanol solvate of lithium bis-(2,6-diiso-propyl-phen-yl) phosphate, {Li[OOP(O-2,6- i Pr2C6H3)2]·(CH4O)3}·CH4O, in methanol. The structure has monoclinic (Cc) symmetry at 150 K. The complex consists of an [Mn{OOP(O-2,6- i Pr2C6H3)2}(CH3OH)5]+ cation, an [OOP(O-2,6- i Pr2C6H3)2]- anion and three non-coordinating methanol mol-ecules. The anion demonstrates disorder of an isopropyl group [occupancy ratio is 0.57 (4):0.43 (4)]. The di-aryl-phosphate ligand in the cation exhibits a κ1 O terminal coordination mode. The Mn atom is in a nearly unperturbed octa-hedral environment. The [Mn{OOP(O-2,6- i Pr2C6H3)2}(CH3OH)5]+ cation exhibits one intra-molecular O-H⋯O bond, and is coordinated via two inter-molecular O-H⋯O hydrogen bonds to the [OOP(O-2,6- i Pr2C6H3)2]- anion. The cations, anions and non-coordinating methanol mol-ecules are linked into infinite chains along the c-axis direction via 0-H⋯O hydrogen bonding. The complex is of inter-est as a possible inhibitor for the thermal decomposition of polydi-methyl-siloxane. The crystal studied was refined as an inversion twin with a domain ratio of 0.47 (3):0.53 (3).

Dinuclear neodymium and lanthanum bis(2,6-diisopropylphenyl) phosphate complexes bearing a hydroxide ligand: catalytic activity of the Nd complex in 1,3-diene polymerization.

The reactions of K[(2,6-iPr2C6H3-O)2POO] either with LaCl3(H2O)7 or with Nd(NO3)3(H2O)6 in a 3:1 molar ratio, followed by vacuum drying and recrystallization from alkanes, have led to the formation of diaquapentakis[bis(2,6-diisopropylphenyl) phosphato]-µ-hydroxido-dilanthanum hexane disolvate, [La2(C24H34O4P)5(OH)(H2O)2]·2C6H14, (1)·2(hexane), and tetraaquatetrakis[bis(2,6-diisopropylphenyl) phosphato]-µ-hydroxido-dineodymium bis(2,6-diisopropylphenyl) phosphate heptane disolvate, [Nd2(C24H34O4P)4(OH)(H2O)4]·2C6H14, (2)·2(heptane). The compounds crystalize in the P21/n and P-1 space groups, respectively. The diaryl-substituted organophosphate ligand exhibits three different coordination modes, viz. κ2O,O'-terminal [in (1) and (2)], κO-terminal [in (1)] and µ2-κ1O:κ1O'-bridging [in (1) and (2)]. Binuclear structures (1) and (2) are similar and have the same unique Ln2(µ-OH)(µ-OPO)2 core. The structure of (2) consists of an [Nd2{(2,6-iPr2C6H3-O)2POO}4(OH)(H2O)4]+ cation and a [(2,6-iPr2C6H3-O)2POO]- anion, which are bound via four intermolecular O-H...O hydrogen bonds. The molecular structure of (1) displays two O-H...O hydrogen bonds between OH/H2O ligands and a κ1O-terminal organophosphate ligand, which resembles, to some extent, the `free' [(2,6-iPr2C6H3-O)2POO]- anion in (2). NMR studies have shown that the formation of (1) undoubtedly occurs due to intramolecular hydrolysis during vacuum drying of the aqueous La tris(phosphate) complex. Catalytic experiments have demonstrated that the presence of the coordinated hydroxide anion and water molecules in precatalyst (2) substantially lowered the catalytic activity of the system prepared from (2) in butadiene and isoprene polymerization compared to the catalytic system based on the neodymium tris[bis(2,6-diisopropylphenyl) phosphate] complex, which contains neither OH nor H2O ligands.

Crystal structure and catalytic activity of tetra-kis-(µ2-ethyl 2,6-di-tert-butyl-4-methyl-phenyl phos-phato-κ2O:O')bis-(ethyl 2,6-di-tert-butyl-4-methyl-phenyl phosphato-κ2O,O')dilutetium n-heptane disolvate.

The title complex, [Lu2(C17H28O4P)6]·2C7H16, was formed in the reaction between potassium 2,6-di-tert-butyl-4-methyl-phenyl ethyl phosphate, [K(2,6- t Bu2-4-MeC6H2-O)(EtO)PO2], and LuCl3(H2O)6 in water, followed by vacuum drying and recrystallization from heptane. Its crystal structure has triclinic (P [Formula: see text]) symmetry at 120 K. The lutetium tris-(phosphate) complex has a binuclear [Lu2(µ-OPO)4] core and the organophosphate ligand exhibits κ2O,O' terminal and µ2-κ1O:κ1O' bridging coordination modes with the LuIII ion being sixfold coordinated. The complex is of inter-est as a precatalyst in the acrylo-nitrile polymerization process and displays good catalytic activity under mild conditions.

Isomorphous rare-earth tris[bis(2,6-diisopropylphenyl) phosphate] complexes and their catalytic properties in 1,3-diene polymerization and in the inhibited oxidation of polydimethylsiloxane.

Crystals of mononuclear tris[bis(2,6-diisopropylphenyl) phosphato-κO]pentakis(methanol-κO)lanthanide methanol monosolvates of lanthanum, [La(C24H34O4P)3(CH3OH)5]·CH3OH, (1), cerium, [Ce(C24H34O4P)3(CH3OH)5]·CH3OH, (2), and neodymium, [Nd(C24H34O4P)3(CH3OH)5]·CH3OH, (3), have been obtained by reactions between LnCl3(H2O)n (n = 6 or 7) and lithium bis(2,6-diisopropylphenyl) phosphate in a 1:3 molar ratio in methanol media. Compounds (1)-(3) crystallize in the monoclinic P21/c space group and have isomorphous crystal structures. All three bis(2,6-diisopropylphenyl) phosphate ligands display a κO-monodentate coordination mode. The coordination number of the metal atom is 8. Each [Ln{O2P(O-2,6-iPr2C6H3)2}3(CH3OH)5] molecular unit exhibits four intramolecular O-H...O hydrogen bonds, forming six-membered rings. The unit forms two intermolecular O-H...O hydrogen bonds with one noncoordinating methanol molecule. All six hydroxy H atoms are involved in hydrogen bonding within the [Ln{O2P(O-2,6-iPr2C6H3)2}3(CH3OH)5]·CH3OH unit. This, along with the high steric hindrance induced by the three bulky diaryl phosphate ligands, prevents the formation of a hydrogen-bond network. Complexes (1)-(3) exhibit disorder of two of the isopropyl groups of the phosphate ligands. The cerium compound (2) demonstrates an essential catalytic inhibition in the thermal decomposition of polydimethylsiloxane in air at 573 K. Catalytic systems based on the neodymium complex tris[bis(2,6-diisopropylphenyl) phosphato-κO]neodymium, (3'), which was obtained as a dry powder of (3) upon removal of methanol, display a high catalytic activity in isoprene and butadiene polymerization.

Isomorphous rare-earth bis[bis(2,6-diisopropylphenyl)phosphate] complexes and their self-assembly into two-dimensional frameworks by intramolecular hydrogen bonds.

The crystal structures of rare-earth diaryl- or dialkylphosphate derivatives are poorly explored. Crystals of bis[bis(2,6-diisopropylphenyl)phosphato-κO]chloridotetrakis(methanol-κO)neodymium methanol disolvate, [Nd(C24H34O4P)Cl(CH4O)4]·2CH3OH, (1), and of the lutetium, [Lu(C24H34O4P)Cl(CH4O)4]·2CH3OH, (2), and yttrium, [Y(C24H34O4P)Cl(CH4O)4]·2CH3OH, (3), analogues have been obtained by reactions between lithium bis(2,6-diisopropylphenyl)phosphate and LnCl3(H2O)6 (in a 2:1 ratio) in methanol. Compounds (1)-(3) crystallize in the C2/c space group. Their crystal structures are isomorphous. The molecule possesses C2 symmetry with a twofold crystallographic axis passing through the Ln and Cl atoms. The bis(2,6-diisopropylphenyl)phosphate ligands all display a κ1O-monodentate coordination mode. The coordination polyhedron for the metal atom [coordination number (CN) = 7] is a distorted pentagonal bipyramid. Each [Ln{O2P(O-2,6-iPr2C6H3)2}2Cl(CH3OH)4] molecular unit exhibits two intramolecular O-H...O hydrogen bonds, forming six-membered rings, and two intramolecular O-H...Cl interactions, forming four-membered rings. Intermolecular O-H...O hydrogen bonds connect each unit via four noncoordinating methanol molecules with four other units, forming a two-dimensional hydrogen-bond network. Crystals of bis[bis(2,6-diisopropylphenyl)phosphato-κO]tetrakis(methanol-κO)(nitrato-κ2O,O')neodymium methanol disolvate, [Nd(C24H34O4P)(NO3)(CH4O)4]·2CH3OH, (4), have been obtained in an analogous manner from NdCl3(H2O)6. Compound (4) also crystalizes in the C2/c space group. Its crystal structure is similar to those of (1)-(3). The κ2O,O'-bidentate nitrate anion is disordered over a twofold axis, being located nearly on it. Half of the molecule is crystallographically unique (CNNd = 8). Unlike (1)-(3), complex (4) exhibits disorder of all three methanol molecules, one isopropyl group of the phosphate ligand and the NO3- ligand. The structure of (4) displays intra- and intermolecular O-H...O hydrogen bonds similar to those in (1)-(3). Compounds (1)-(4) represent the first reported mononuclear bis[bis(diaryl/dialkyl)phosphate] rare-earth complexes.

Crystal structure of [bis-(2,6-diiso-propyl-phen-yl) phosphato-κO]tris-(methanol-κO)lithium methanol monosolvate.

Crystals of the title compound, [Li{OOP(O-2,6-(i)Pr2C6H3)2}(CH3OH)3]·CH3OH or [Li(C24H34O4P)(CH3OH)3]·CH3OH, have been formed in the reaction between HOOP(O-2,6-(i)Pr2C6H3)2 and LiOH in methanol. The title compound is of inter-est as it represents the first reported crystal structure of the family of lithium phosphate diesters. The {Li(CH3OH)3[O2P(O-(i)Pr2C6H3)2]} unit displays the Li atom in a slightly distorted tetra-hedral coordination environment and exhibits one intra-molecular O-H⋯O hydrogen bond between a coordinating methanol mol-ecule and the terminal non-coordinating O atom of the phosphate group. The unit is connected with two non-coordinating methanol mol-ecules through two inter-molecular O-H⋯O hydrogen bonds, and with a neighbouring unit through two other O-H⋯O inter-actions. These inter-molecular hydrogen bonds lead to the formation of infinite chains along [100]. There are no significant inter-actions between the chains.

Easily accessible, hydrocarbon-soluble, crystalline, anhydrous lanthanide (Nd, La, and Y) phosphates.

Nd, La and Y triphosphates were prepared via the reaction of potassium ionol ethyl phosphate with the corresponding lanthanide nitrates or chlorides in water. According to the X-ray diffraction data, the recrystallised reaction products were dimers. The products did not contain water, were readily soluble in hydrocarbon solvents and demonstrated promising catalytic properties in the polymerisation of butadiene and DL-dilactide.

Synthesis of hydroxydiamines and triamines via reductive cleavage of N-N bond in substituted pyrazolidines.

Aliphatic polyamines, being a versatile class of organic compounds, are widely used in many fields of medicine and organic chemistry. However, the general approach to the synthesis of chiral aliphatic polyamines has been still undeveloped. Here, we describe a new method for the synthesis of chiral trifunctional amino compounds, namely hydroxydiamines and triamines. The initial compounds, namely substituted hydroxy- or aminopyrazolidines and pyrazolines, are readily available using convenient stereoselective methods developed earlier by us. The proposed method allows synthesizing of chiral diaminoalcohols and triamines, which are the analogs of a well-known anti-TB drug, namely ethambutol, and cannot be obtained alternatively. The key step of the synthesis is N-N bond cleavage in substituted hydroxy- or aminopyrazolidines and pyrazolines with borane-tetrahydrofuran complex; other known methods for N-N bond cleavage turned out to be ineffective. The main advantage of the proposed method is the retention of a certain configuration of stereocenters in the course of the reaction. Six new chiral diasteomerically pure substituted hydroxydiamines and triamines and the enantiomerically pure triamine with four chiral centers were synthesized and characterized using NMR, IR and mass spectroscopy, as well as elemental analysis.