Synthesis of the sterically constrained ligand precursor cyclopentadienyl-2,6-diphenylbenzene and structure of [(2,6-Ph2–C6H3-η5-C5H4)Zr(NEt2)3]

A Pd-catalysed Stille coupling of 2,6-diphenyliodobenzene with tributylcyclopentadienyltin gave the sterically constrained ligand precursor cyclopentadienyl-2,6-diphenylbenzene (1). Treatment of this precursor with tetrakis(diethylamido)zirconium(IV) gave the three-legged piano-stool complex [(2,6-Ph₂–C₆H₃-η⁵-C₅H₄)Zr(NEt₂)₃] (2). Complex 2 was characterised by ¹H- and ¹³C{¹H}-NMR spectroscopy as well as by X-ray crystallography which showed significant distortions of the three-legged piano-stool geometry as a result of steric interactions with the bulky aryl substituent.     

Monocarbaborane anion chemistry: use of an anilinyl residue as an anchor group for the construction of rod-like monocarbaboranyl diazo and imino compounds

Reaction of the [1-(4-H₂N–C₆H₄)-closo-1-CB₉H₉]⁻ anion 1 with Me₂CHCH₂CH₂ONO and dilute HCl gives neutral [1-(4-N₂–C₆H₄)-closo-1-CB₉H₉] 3, which reacts with PhNH₂ to form the 19.5 Å [1-{4-(4-H₂N–C₆H₄–NN)–C₆H₄}-closo-1-CB₉H₉]⁻ azo anion 2. Anion 1 with ketones and aldehydes gives imino compounds: with (CH₃)₂CO it gives neutral [1-{4-(Me₂CNH)–C₆H₄}-closo-1-CB₉H₉] 6 and with the para-dialdehyde C₆H₄-1,4-(CHO)₂ it gives the 30.5 Å extended rod-like neutral species [C₆H₄-1,4-{1-(CHNH–C₆H₄)-closo-1-CB₉H₉}₂] 8.     

C,N-chelated dicyclopentadienylzirconium complexes and their possible use as hydrogenation catalysts

In situ generated Cp₂Zr(n-Bu)Cl (6) reacts with {2-[(CH₃)₂NCH₂]C₆H₄}₂Pb to form exclusively {2-[(CH₃)₂NCH₂]C₆H₄}Cp₂ZrCl (7), [(CH₃)₂NCH₂]C₆H₅, butene and elemental lead. The further derivatization of chloride (7) to fluoride (8), hydride (9), methyl derivative (10), and a reduction of 7 are also described. The crystal structures of 7–10 were determined. The catalytic activity of 9 and 10 in hydrogenation of styrene was also preliminarily tested.     

Yttrium 3,5-di-tert-butyl-catecholates supported by 2,6-diisopropylphenyl substituted β-diketiminate

β-Diketiminato yttrium complex [LClY(μ-Cl)₃YL(THF)] (L = 2,6-ⁱPr₂C₆H₃-NC(Me)CHC(Me)N-2,6-ⁱPr₂C₆H₃) has been used for the preparation of non-solvated mixed-ligand compound [{LY(μ-3,5-Cat)}₂] (1) by the salt metathesis reaction with potassium 3,5-di-tert-butyl-catecholate (3,5-CatK₂). The dinuclear yttrium complex [{K(THF)}{LY(μ-3,5-Cat)₃Y(THF)}] (2) has been found as an unexpected by-product of side reaction caused by the presence of an admixture of YCl₃. Complex 1 has been fully characterized by a set of methods and its solid-state structure, along with that of by-product 2, has been determined by single-crystal X-ray diffraction analysis.     

Intramolecular hydrogen bond controlled coordination of N-thiophosphorylated thiourea 2,6-Me2C6H3NHC(S)NHP(S)(OiPr)2 with Ni(II)

Reaction of O,O′-diisopropylthiophosphoric acid isothiocyanate (iPrO)₂P(S)NCS with 2,6-dimethylaniline 2,6-Me₂C₆H₃NH₂ leads to the new N-thiophosphorylated thiourea 2,6-Me₂C₆H₃NHC(S)NHP(S)(OiPr)₂ (HL). Reaction of the potassium salt of HL with Ni(II) in aqueous EtOH leads to the complex of formula [Ni(L-N,S)₂]. The molecular structures of the thiourea HL and the complex [Ni(L-N,S)₂] were elucidated by single crystal X-ray diffraction analysis, ¹H and ³¹P NMR spectroscopy and microanalysis. In the complex [Ni(L-N,S)₂], the metal center is found to be in a square-planar N₂S₂ environment formed by the CS sulfur atoms and the P–N nitrogen atoms of two deprotonated L ligands. The ligands are in a trans-configuration.     

Different hydrolytic stabilities of some C,N-chelated germanium alkoxides

C,N-intramolecularly coordinated germanium(IV) methoxides Ar₃GeOMe (1) and (Ar′)₂Ge(OMe)₂ (2) [where Ar = [2-(Me₂NCH₂)C₆H₄]⁻, Ar′ = [2-(DipN = CH)C₆H₄]⁻, Dip = 2,6-(i-Pr)₂C₆H₃] were prepared by the reaction of the lithium precursors ArLi and Ar′Li with Ge(OMe)₄ in appropriate molar ratio. While the diorganogermanium(IV) compound 2 is air-stable specie, triorganogermanium(IV) compound is surprisingly smoothly hydrolyzed by air-moisture to corresponding triorganogermanol Ar₃GeOH (3). Studied compounds were characterized by the help of multinuclear NMR spectroscopy and in the case of 2 and 3 using single-crystal X-ray diffraction analysis.     

Mononuclear versus dinuclear palladacycles derived from 1,3-bis(N,N-dimethylaminomethyl)benzene: Structures and catalytic activity

Mononuclear and dinuclear palladacycles derived from 1,3-bis(N,N-dimethylaminomethyl)benzenes, [{Pd(Cl)}2,6-(Me₂NCH₂)₂C₆H₃] (1) and [1-{Pd(H₂O)(Py)}-5-{Pd(OTf)(Py)-2,4-(Me₂NCH₂)₂C₆H₂]-(OTf) (2), were synthesized and their structures were fully characterized. Complex 1 is a pincer complex with η³-mer NCN phenyl backbone, complex 2 is a bispalladium(II) complex with 1,2- and 4,5- two C,N-ortho phenyl backbone. Whereas the pincer complex 1 acted as a poor catalyst on methanolysis of fenitrothion, complex 2 demonstrated high catalytic activity in the same reactions, but there is no synergetic effect between two palladium ions. The results clearly indicate that a dissociable co-ligand in the palladacycle compounds significantly promotes the catalytic methanolysis.     

Homo- and R/S-copolymerizations of chiral methylpropargyl esters carrying pyrene moieties, and optical properties of the formed polymers

Pyrene-functionalized chiral methylpropargyl esters, (R)-3-butyn-2-yl-1-pyrenebutyrate [(R)-1], (S)-3-butyn-2-yl-1-pyrenebutyrate [(S)-1], (R)-3-butyn-2-yl-1-pyrenecarboxylate [(R)-2], and 3-butyn-2-yl-1-pyrenecarboxylate [(R,S)-2] were polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] to obtain the corresponding polymers with moderate molecular weights (M_n: 10?500-66?500) in good yields (82-97%). All the polymers were soluble in CHCl₃, CH₂Cl₂, and THF. The polarimetric and CD spectroscopic data indicated that poly[(R)-1], poly[(S)-1], and poly[(R)-2] existed in a helical structure with predominantly one-handed screw sense in these solvents. The helical structure of poly[(R)-1] and poly[(S)-1] was stable upon heating and addition of MeOH, while that of poly[(R)-2] changed upon MeOH addition. The copolymerization of (R)-1 with (S)-1 was also conducted to obtain the copolymers satisfactorily. Poly[(R)-1], poly[(S)-1], and poly[(R)-2] emitted fluorescence smaller than the corresponding racemic copolymers. The fluorescence intensity was tuned by the addition of MeOH to THF solutions of the polymers.     

Cage-opening supramolecular isomerism in Cu(II) complexes

Reactions of Cu(NO₃)₂·3H₂O or Cu(CF₃SO₃)₂·6H₂O with semirigid ligands 2,6-bis(pyridin-3-ylmethyl)-3a,4,4a,7a,8,8a-hexahydro-4,8-ethenopyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (L1) and 2,6-bis(pyridin-4-ylmethyl)-3a,4,4a,7a,8,8a-hexahydro-4,8-ethenopyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (L2) result in 0D tetragonal prismatic cage (1, 4), 1D loop-and-chain (2, 5, 6), and 2D (4,4) network (3) metal-organic complexes, which comprise of U_a, U_b or Z type ligand conformations, respectively. Solid state X-ray diffraction and solution state ESI-MS analyses manifest the ring-opening isomerization mechanism among the complexes, and photoluminescence properties are also studied.     

Coordinatively unsaturated molybdenum complexes with chelating cycloheptatrienyl-phosphane ligands and their use in transition metal catalysis

The synthesis of the tetrahydroborate complex [(2-iPr₂PC₆H₄-η⁷-C₇H₆)Mo(η²-BH₄)(P–Mo)] 3 containing the linked cycloheptatrienyl-phosphane ligand [2-(diisopropylphosphanyl)phenyl]cycloheptatrienyl is described, which provides the possibility to generate the 14-electron complex [(2-iPr₂PC₆H₄-η⁷-C₇H₆)Mo(P–Mo)]⁺ (4) on treatment with dimethylanilinium salts such as [HNMe₂Ph][BPh₄]. Generation of (4)BPh₄ in the presence of 2,6-dimethylphenyl isocyanide, 2,5-norbornadiene or phenylacetylene affords the diisocyanide complex (5a)BPh₄, the diolefin complex (5b)BPh₄ and the alkyne complex (6)BPh₄, respectively. The latter complex can be used for the catalytic oligomerization of phenylacetylene affording predominantly the cyclotrimers 1,3,5- and 1,2,4-triphenylbenzene.     

1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester: A new bidentate ligand in arene ruthenium chemistry

1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester (1) is prepared from 1,1′-ferrocene dicarbonyl chloride and 4-hydroxypyridine. This new bidentate ferrocenoyl ligand reacts with the monocationic complex [(η⁶-p-cymene)₂Ru₂(μ-OH)₃]⁺ to give the dicationic complex [(η⁶-p-cymene)₂Ru₂(μ-OH)₂(1,1′- (NC₅H₄–OOC)₂–Fc)]²⁺ (2) (Fc: C₅H₄–Fe–C₅H₄), isolated as a tetrafluoroborate salt. The single-crystal X-ray structure analysis of [2][BF₄]₂ reveals the ferrocenoyl pyridine ligand 1 to act as μ₂-η² chelating ligand in the dinuclear complex, having replaced a μ₂-η¹-hydroxo ligand.     

Self-assembly and guest binding of nickel(II) macrocyclic complex with pentyl groups and cis,cis-1,3,5-cyclohexanetricarboxylic acid

Reaction of the nickel(II) macrocyclic complex 1 including pendant pentyl groups in MeCN/H₂O mixed solvent with deprotonated cis,cis-1,3,5-cyclohexanetricarboxylic acid (CTC^3 −) resulted in two-dimensional (2-D) coordination polymer [Ni(C₁₈H₄₂N₆)]₃[C₆H₉(COO)₃]₂·6H₂O·6CH₃CN (2). The crystal structure of 2 indicates that each nickel(II) macrocyclic unit binds two CTC^3 − ions in trans position and each CTC^3 − ion coordinates three nickel(II) macrocyclic complexes to form a 2-D layer with hexagonal motif. The dried solid of 2 differentiates MeOH, EtOH, and PhOH in toluene solvent with the K_f values of 1.38, 2.11, and 6.68 M^− 1, respectively.     

Phenylcalcium iodides with silyl substituents in para-position

The reduction of silyl substituted iodobenzenes 4-Ph₃Si–C₆H₄–I (1) and Me₂Si(–C₆H₄–4–I)₂ (2) with activated calcium yields sparingly soluble 4-Ph₃Si–C₆H₄–Ca(thf)₄I (3) and moderate soluble Me₂Si[–C₆H₄–4-Ca(thf)₄I]₂ (4). The molecular structures of 1 and 2 and a structural motif of 4 are presented.     

Improved synthesis of pincer ligand precursor,and synthesis and structural characterization of terphenyl scaffolded S–C–S palladium pincer complex

An easier and more expedient synthesis of 2,6-(BrCH₂C₆H₄)₂-4-I-C₆H₃ (2) is reported. This material allowed easy synthesis of the new pincer ligand precursor 2,6-(4-CH₃C₆H₄SCH₂C₆H₄)₂-4-I-C₆H₃ (3) in 87% yield. Compound 3 reacts with Pd₂(dba)₃ to give the new palladium pincer complex 4. Compound 4 has been fully characterized, including structural characterization by single crystal X-ray diffraction methods. The results of the crystallographic work on 4 reveal a twisted type pincer complex not unlike related terphenyl pincer complexes.     

Supramolecular Polymers and Chiral Phosphine Oxides by Oxidation of Gold(I) Complexes

The chiral diphosphine ligand R,R-cyclo-C₆H₁₀-trans-1,2-{NHC(=O)C₆H₄-2-PPh₂}₂, 1, forms complexes with gold(I) of formula [Au(1)]Cl, 2, and [(ClAu)₂(µ-1)], 3, in which the diphosphine acts as a trans-chelate and bridging ligand, respectively. Oxidation of these gold(I) complexes leads to dissociation and oxidation of the diphosphine ligand to form the corresponding diphosphine dioxide R,R-cyclo-C₆H₁₀-1,2-{NHC(=O)C₆H₄-2-P(=O)Ph₂}₂, which has been crystallized in its protonated form and as complexes with Na⁺ and Fe²⁺, with [AuBr₂]^? or [AuBr₄]^? anions. Some of these compounds form supramolecular polymers by intermolecular hydrogen bonding.     

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94?000 were obtained in 20-98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV-vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.     

Synthesis and structural characterization of isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarboranes stabilized by the agostic bonding interaction

The [7-Me₃N-nido-7-CB₁₀H₁₂] (1), after being treated with two molar equiv. of Proton Sponge, reacts with [(η⁴-C₁₀H₁₂)₂Rh₂(μ-Cl)₂] (2) in benzene–ethanol solution affording two isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarborane complexes, differing in hapticity of the carbocyclic ligand, viz. [2,2-{(2′,3′-η²):(5′-η¹)-C₁₀H₁₃}-1-(Me₃N)-2,1-closo-RhCB₁₀H₁₀] (3) and [2-{(1′-3′-η³)-C₁₀H₁₃}-1-(Me₃N)-2,1-closo-RhCB₁₀H₁₀] (4). Isomeric compounds 3 and 4 were characterized by analytical, multinuclear NMR spectroscopic data as well as by single-crystal X-ray diffraction study, which revealed the existence of an agostic C–H⋯Rh interaction in both the species.     

Synthesis,structure, and catalytic activity of benzyl thorium metallocenes

Treatment of the chloride metallocene [η⁵-1,3-(Me₃C)₂C₅H₃]₂ThCl₂ or [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂ThCl₂ with 2 equiv of PhCH₂K in diethyl ether at room temperature gives, after recrystallization from a benzene solution, the benzyl metallocenes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Th(CH₂Ph)₂ (1) and [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂Th(CH₂Ph)₂ (2), respectively, in good yields. Complexes 1 and 2 have been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analyses. They are active catalysts for the polymerization of rac-lactide, leading to the atactic polylactides with high molecular weights and narrow molecular weight distributions.     

Nested [Na6(H2O)]6+ encapsulation of nickel(II) coordination framework assembled from pyridyl-2,6-dicarboxylic acid

Hydrothermal reactions of pyridyl-2,6-dicarboxylic acid (H₂PDC) and NiCl₂ · 6H₂O in the presence of NaOH and KOH, respectively afforded the products, {[Ni(PDC)(Cl)](Na)(H₂O)/3}_n (1) and K₂[Ni(PDC)₂] · 7H₂O (2), of which 1 was characterized consisting of 3-D porous framework and [Na₆(H₂O)]⁶⁺ inclusions, and 2 was a mononuclear complex with potassium hydrate as counterion.