Binuclear Salan borate compounds with three-coordinate boron atoms

A series of binuclear boron compounds supported by Salan(^tBu)H₄ ligands have been prepared. They are of the general formula Salan(^tBu)[B(OR)]₂. The compounds are Salean(^tBu)(BOR)₂ [Salean(^tBu) = (N,N′-ethylenebis(3,5-di-tert-butyl-salicylamine)), R = Me (1), SiMe₃ (4)], Salban(^tBu)(BOR)₂[Salban(^tBu) = (N,N′-butylenebis(3,5-di-tert-butyl-salicylamine)), R = Me (2), SiMe₃ (5)], and Salhan(^tBu)(BOR)₂ [Salhan(^tBu) = (N,N′-hexylenebis(3,5-di-tert-butyl-salicylamine)), R = Me (3)]. All of the compounds were characterized by spectroscopic (¹H NMR, ¹¹B NMR, IR) and physical (mp, EA) techniques. Also, 1, 2 and 4 were structurally characterized by single crystal X-ray diffraction studies.     

Synthesis, structures, and catalytic properties for ethylene polymerization of bridged [η,η-C5H4CHPhArO]TiCl2 complexes

A number of bridged half-sandwich titanium complexes [η⁵:η¹-2-C₅H₄CHPh-4-R¹-6-R²C₆H₂O]TiCl₂ [R¹ = H (5), Me (6), ^tBu (7, 8); R² = H (6, 7), ^tBu (5, 8)] were synthesized from the reaction of their corresponding trimethylsilyl substituted ligand precursors 2-Me₃SiC₅H₄CHPh-4-R¹-6-R²C₆H₂OSiMe₃ [R¹ = H (1), Me (2), ^tBu (3, 4); R² = H (2, 3), ^tBu (1, 4)] with TiCl₄ in hexane. All new complexes were characterized by ¹H and ¹³C NMR spectroscopy. Molecular structures of complexes 5 and 8 were determined by single crystal X-ray diffraction analysis. Upon activation with AlⁱBu₃/Ph₃CB (C₆F₅)₄, complexes 5-8 exhibit reasonable catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing polyethylene and poly(ethylene-co-1-hexene) with moderate molecular weights.     

Self-assembly of di- and triorganotin(IV) complexes: Syntheses, characterization and crystal structures of 1D polymeric chain containing O,O-diethyl or O,O-diisopropyl phosphoric acid ligands

A series of organotin(IV) complexes with O,O-diethyl phosphoric acid (L¹H) and O,O-diisopropyl phosphoric acid (L²H) of the types: [R₃Sn · L]_n (L = L¹, R = Ph 1, R = PhCH₂2, R = Me 3, R = Bu 4; L = L², R = Ph 9, R = PhCH₂10, R = Me 11, R = Bu 12), [R₂Cl Sn · L]_n (L = L¹, R = Me 5, R = Ph 6, R = PhCH₂7, R = Bu 8; L = L², R = Me 13, R = Ph 14, R = PhCH₂15, R = Bu 16), have been synthesized. All complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy analysis. Among them, complexes 1, 2, 3, 5, 8, 9 and 11 have been characterized by X-ray crystallography diffraction analysis. In the crystalline state, the complexes adopt infinite 1D infinite chain structures which are generated by the bidentate bridging phosphonate ligands and the five-coordinated tin centers.     

Insertion reaction of elemental sulfur into the Ln–C bond: Synthesis and characterization of [(C5H4SiMe2Bu)2Ln(μ-SR)]2 (R = Me,Ln = Yb,Er, Dy,Y; R = Bu,Ln = Yb,Dy)

Treatment of (C₅H₄SiMe₂^tBu)₂LnR with 1 equiv of elemental sulfur in toluene at ambient temperature gives dimeric complexes [(C₅H₄SiMe₂^tBu)₂Ln(μ-SR)]₂ [R = Me, Ln = Yb (1), Er (2), Dy (3), Y (4); R = ⁿBu, Ln = Yb (5), Dy (6)]. All these complexes have been characterized by elemental analysis, IR and mass spectroscopies. The structures of complexes 1, 3, 5 and 6 are also determined through X-ray single crystal diffraction analysis, indicating that only one sulfur atom from elemental sulfur inserts into Ln–C σ-bond.     

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Aluminium complexes bearing the N,N-chelating ligand 1,4-bis(2-hydroxy-3,5-di-tert-butyl)piperazine (1) have been synthesised. Both monometallic and bimetallic aluminium methyl complexes (2 and 3, respectively) were prepared by treatment of 1 with the appropriate amount of AlMe₃. Complex 2 can be converted to 3 by addition of excess AlMe₃. Bimetallic aluminium-ethyl complex 4 was also prepared. Treatment of 1 with AlEt₂Cl afforded the monometallic chloride complex 5. Treatment of this latter complex with potassium alkoxides (KOR, R = Me, Et, ⁱPr, ^tBu) or AgOTf afforded the corresponding aluminium alkoxide complexes (6, R = Et; 7, R = Me; 8, R = ⁱPr; 9, R = ^tBu; 10, R = OTf) in good yields. Aluminium ethoxide complex 6 was also synthesised by treatment of 1 with AlEt₂OEt. All of these complexes were tested as potential catalysts in the ring-opening polymerisation of rac-lactide and caprolactone with limited success.     

Synthesis and evaluation of substituted pyrazoles palladium(II) complexes as ethylene polymerization catalysts

The substituted pyrazole palladium complexes, (3,5-^tBu₂pz)₂PdCl₂ (1) (3,5-Me₂pz)₂PdCl₂ (2), (3-Mepz)₂PdCl₂ (3) and (pz)₂PdCl₂ (4) (pzH=pyrazole), can be prepared from the reaction of (COD)PdCl₂ with the appropriate pyrazole. The chloromethyl derivative, (3,5-^tBu₂pz)₂PdCl(Me) (5), was prepared from (COD)PdClMe and ^tBu₂pzH. X-ray crystal structure determination of 1 and 5 established their structures in the solid state to be the trans-isomer. After activation of 1-4 and 5 with methylaluminoxane (MAO) the resulting palladium complexes were used as catalysts in ethylene polymerization, yielding linear high-density polyethylene (HDPE). The highest activity was observed for (3,5-^tBu₂pz)PdClMe.     

Chiral self-assembly of triorganotin complexes: Syntheses, characterization, crystal structures and antitumor activity of organotin(IV) complexes containing (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid ligands

Six new chiral triorganotin(IV) complexes, {(R₃Sn)₂[C₃H₆(COO)₂]}_n (R = Me: 1; Bu: 2), {(R₃Sn)₂[C₄H₈(COO)₂]}_n (R = Me: 3; Bu: 4), and {(R₃Sn)₂[C₂H₄O(COO)₂]}_n (R = Me: 5; Bu: 6) have been prepared by treatment of (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid, with the corresponding R₃SnCl (R = Me, Bu) and sodium ethoxide in methanol. All the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and TGA. Except for 3, all of the complexes were also characterized by X-ray crystallography. The structural analyses reveal that complexes 1 and 5 have 2D network structures in which (R)-(+)-methylsuccinic acid and l-(−)-malic acid act as tetradentate ligands coordinated to trimethyltin(IV) ions. Complexes 2 and 4 have 3D metal-organic framework structures in which the deprotoned acids serve as tetradentate ligands. Complex 6 adopts a 1D zigzag chain structure and forms a 2D supramolecular framework through intermolecular C-H?O interactions. In addition, the antitumor activities of complexes 1-6 have been studied. We also have measured the specific rotation of the chiral dicarboxylic acids and the organotin derivatives.     

Synthesis and characterization of aluminum complexes of 2-pyrazol-1-yl-ethenolate ligands

The synthesis and the characterization of some new aluminum complexes with bidentate 2-pyrazol-1-yl-ethenolate ligands are described. 2-(3,5-Disubstituted pyrazol-1-yl)-1-phenylethanones, 1-PhC(O)CH₂-3,5-R₂C₃HN₂ (1a, R = Me; 1b, R = Bu^t), were prepared by solventless reaction of 3,5-dimethyl pyrazole or 3,5-di-tert-butyl pyrazole with PhC(O)CH₂Br. Reaction of 1a or 1b with (R¹ = Me, Et) yielded N,O-chelate alkylaluminum complexes (2a, R = R¹ = Me; 2b, R = Bu^t, R¹ = Me; 2c, R = Me, R¹ = Et). Compound 1a was readily lithiated with LiBuⁿ in thf or toluene to give lithiated species 3. Treatment of 3 with 0.5 equiv of MeAlCl₂ or AlCl₃ yielded five-coordinated aluminum complexes [XAl(OC(Ph)CH{(3,5-Me₂C₃HN₂)-1})₂] (4, X = Me; 5, X = Cl). Reaction of 5 with an equiv of LiHBEt₃ generated [Al(OC(Ph)CH{(3,5-Me₂C₃HN₂)-1})₃] (6). Complex 6 was also obtained by reaction of 3 with 1/3 equiv of AlCl₃. Treatment of 5 with 2 equiv of AlMe₃ yielded complex 2a, whereas with an equiv of AlMe₃ afforded a mixture of 2a and [Me(Cl)AlOC(Ph)CH{(3,5-Me₂C₃HN₂)-1}] (7). Compounds 1a, 1b, 2a-2c and 4-6 were characterized by elemental analyses, NMR and IR (for 1a and 1b) spectroscopy. The structures of complexes 2a and 5 were determined by single crystal X-ray diffraction techniques. Both 2a and 5 are monomeric in the solid state. The coordination geometries of the aluminum atoms are a distorted tetrahedron for 2a or a distorted trigonal bipyramid for 5.     

The effect of titanium alkoxides in the synthesis of heterobimetallic complexes by titanocene(III) alkoxide-induced metal-metal bond cleavage of metal carbonyl dimers

A series of titanocene(III) alkoxides L₂Ti(III)OR where L = Cp, R = Et(1b), ^tBu(1a), 2,6-Me₂C₆H₃(1c), 2,6-^tBu₂-4-Me-C₆H₂(1d), or L = Cp*, R = Me(2e), ^tBu(2a), Ph(2f) was synthesized and subjected to reaction with [CpM(CO)₃]₂ [M = Mo, W], [CpRu(CO)₂]₂, and Co₂(CO)₈. The Ti(III) precursors 1a, 1c, 2a, 2e, and 2f reacted with [CpM(CO)₃]₂ [M = Mo, W] to form heterobimetallic complexes L₂Ti(OR)(μ-OC)(CO)₂MCp [M = Mo, W], of which Ti and M are linked by an isocarbonyl bridge. Reactions of these Ti(III) complexes with Co₂(CO)₈ resulted in formation of Ti-Co₁ heterobimetallic complexes, from 2a, 2e, or 2f, or Ti-Co₃ tetrametallic complexes, Cp₂Ti(O^tBu)(μ-OC)Co₃(CO)₉ from 1a, 1b, or 1c. The products were characterized by NMR, IR, and X-ray crystallography. Reaction mechanisms were proposed from these results, in particular, from steric/electronic effects of titanium alkoxides.     

Synthesis and reactivity of asymmetrically substituted ansa-bridged zirconocene complexes: X-ray crystal structures of [Zr{R(H)C(η-C5Me4)(η-C5H4)}Cl2] (R = Bu, Bu) and [Zr{Bu(H)C(η-C5Me4)(η-C5H4)}(CH2Ph)2]

The dialkyl complexes, (R = Prⁱ, R′ = Me (2a), CH₂Ph (3a); R = Buⁿ, R′ = Me (2b), CH₂Ph (3b); R = Bu^t, R′ = Me (2c), CH₂Ph (3c); R = Ph, R′ = Me (2d), CH₂Ph (3d)), have been synthesized by the reaction of the ansa-metallocene dichloride complex, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (R = Prⁱ (1a), Buⁿ (1b), Bu^t (1c), Ph (1d)), and two molar equivalents of the alkyl Gringard reagent. The insertion reaction of the isocyanide reagent, CNC₆H₃Me₂-2,6, into the zirconium-carbon σ-bond of 2 gave the corresponding η²-iminoacyl derivatives, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}{η²-MeCNC₆H₃Me₂-2,6}Me] (R = Prⁱ (4a), Buⁿ (4b), Bu^t (4c), Ph (4d)). The molecular structures of 1b, 1c and 3b have been determined by single-crystal X-ray diffraction studies.     

Reactivity studies of (η-arene)ruthenium dimeric complexes towards pyrazoles: isolation of amidines, bis pyrazoles and chloro bridged pyrazole complexes

The complex [(η⁶-p-cymene)Ru(μ-Cl)Cl]₂1 reacts with pyrazole ligands (3a-g) in acetonitrile to afford the amidine derivatives of the type [(η⁶-p-cymene)Ru(L)(3,5-HRR′pz)](BF4)₂ (4a-f), where L = {HNC(Me)3,5-RR′pz}; R, R′ = H (4a); H, CH₃ (4b); C₆H₅ (4c); CH₃, C₆H₅ (4d) OCH₃ (4e); and OC₂H₅ (4f), respectively. The ligand L is generated in situ through the condensation of 3,5-HRR′pz with acetonitrile under the influence of [(η⁶-p-cymene)RuCl₂]₂. The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂2 reacts with pyrazole ligands in acetonitrile to yield bis-pyrazole derivatives such as [(η⁶-C₆Me₆)Ru (3,5-HRR′pz)₂Cl](BF₄) (5a-b), where R, R′ = H (5a); H, CH₃ (5b), as well as dimeric complexes of pyrazole substituted chloro bridged derivatives [{(η⁶-C₆Me₆)Ru(μ-Cl) (3,5-HRR′pz)}₂](BF₄)₂ (5c-g), where R, R′ = CH₃ (5c); C₆H₅ (5d); CH₃, C₆H₅ (5e); OCH₃ (5f); and OC₂H₅ (5g), respectively. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures¹ of representative complexes [(η⁶-C₆Me₆)Ru{3(5)-Hmpz}₂Cl]⁺5b, [(η⁶-C₆Me₆)Ru(μ-Cl)(3,5-Hdmpz)]₂²⁺5c and [(η⁶-C₆Me₆)Ru(μ-Cl){3(5)Me,5(3)Ph-Hpz}]₂²⁺5e were established by single crystal X-ray diffraction studies.     

Substituted lithiumtrimethylsiloxysilanides LiSiRR′(OSiMe3) - Investigations of their synthesis, stability and reactivity

The reactions of the trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-h: R′ = Ph, 1a: R = H, 1b: R = Me, 1c: R = Et, 1d: R = ⁱPr, 1e: R = ^tBu, 1f: R = Ph, 1g: R = 2,4,6-Me₃C₆H₂ (Mes), 1h: R = 2,4,6-(Me₂CH)₃C₆H₂ (Tip); 1i: R = R′ = Mes) with lithium metal in tetrahydrofuran (THF) at −78 °C and in a mixture of THF/diethyl ether/n-pentane in a volume ratio 4:1:1 at −110 °C lead to mixtures of numerous compounds. Dependent on the substituents silyllithium derivatives (Me₃SiO)RR′SiLi (2b-i), Me₃SiO(RR′Si)₂Li (3a-g), Me₃SiRR′SiLi (4a-h), (LiO)RR′SiLi (12e, 12g-i), trisiloxanes (Me₃SiO)₂SiRR′ (5a-i) and trimethylsiloxydisilanes (6f^∗, 6h^∗, 6i^∗) are formed. All silyllithium compounds were trapped with Me₃SiCl or HMe₂SiCl resulting in the following products: (Me₃SiO)RR′SiSiMe₂R″ (6b-i: R″ = Me, 7c-i: R″ = H), Me₃SiO(RR′Si)₂SiMe₂R″ (8a-g: R″ = Me, 9a-g: R″ = H), Me₃SiRR′SiSiMe₂R″ (10a-h: R″ = Me, 11a-h: R″ = H) and (HMe₂SiO)RR′SiSiMe₂H (13e, 13g-i). The stability of trimethylsiloxysilyllithiums 2 depends on the substituents and on the temperature. (Me₃SiO)Mes₂SiLi (2i) is the most stable compound due to the high steric shielding of the silicon centre. The trimethylsiloxysilyllithiums 2a-g undergo partially self-condensation to afford the corresponding trimethylsiloxydisilanyllithiums Me₃SiO(RR′Si)₂Li (3a-g). (Me₃)Si-O bond cleavage was observed for 2e and 2g-i. The relatively stable trimethylsiloxysilyllithiums 2f, 2g and 2i react with n-butyllithium under nucleophilic butylation to give the n-butyl-substituted silyllithiums ⁿBuRR′SiLi (15g, 15f, 15i), which were trapped with Me₃SiCl. By reaction of 2g and 2i with 2,3-dimethylbuta-1,3-diene the corresponding 1,1-diarylsilacyclopentenes 17g and 17i are obtained.X-ray studies of 17g revealed a folded silacyclopentene ring with the silicon atom located 0.5 Å above the mean plane formed by the four carbon ring atoms.     

Heteroleptic tin (II) dialkoxides stabilized by intramolecular coordination Sn(OCH2CH2NMe2)(OR) (R = Me, Et, Pr, Bu, Ph). Synthesis, structure and catalytic activity in polyurethane synthesis

A straightforward method of synthesis of heteroleptic tin (II) alkoxides stabilized by one intramolecular coordination bond was developed. Addition of one equivalent of dimethylamino ethanol to diamide Sn(N(SiMe₃)₂)₂ (5) yields alkoxy-amido derivative Sn(OCH₂CH₂NMe₂)(N(SiMe₃)₂) (2). Further addition of alcohol leads to corresponding heteroleptic dialkoxides Sn(OCH₂CH₂NMe₂)(OR) (R = Me (6), Et (7), ⁱPr (8), ^tBu (9), Ph (10)). Catalytic activity of tin (II) compounds in polyurethane formation was tested.     

Hypervalent and binuclear silicon and germanium derivatives from bis-(3,5-di-tert-butyl-2-phenol)-oxamide

The reactions of bis-(3,5-di-tert-butyl-2-phenol)oxamide (1) with Cl₂SiR₂ (Me or Ph) or Cl₂GeR₂ (Me, nBu or Ph) in THF provided binuclear pentacoordinated silicon and germanium compounds: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylsilane (2), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylsilane (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylgermane (4), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-di-n-butylgermane (5) and bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylgermane (6). The mono-nuclear tetracoordinated silicon compounds N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(dimethylsilane) (8) and N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(diphenylsilane) (9) were synthesized from N-(3,5-di-tert-butyl-2-phenol)acetamide (7) and Cl₂SiR₂ (R = Me and Ph). Comparison of the ²⁹Si NMR chemical shifts of the penta- (2 and 3) and tetracoordinated (8 and 9) silicon compounds provided information about the intramolecular coordination of the carbonyl group to the silicon atom. Compounds 3 and 6 were characterized by single-crystal X-ray analyses. They have planar hexacyclic structures where the central atoms present distorted tbp geometries with one nitrogen and two carbon atoms in equatorial positions and two oxygen atoms in apical positions.     

Investigation on coordination modes of organotin(IV) complexes with 6-thiopurine and related ligands

The organotin(IV) complexes R₂Sn(tpu)₂ · L [L = 2MeOH, R = Me (1); L = 0: R = n-Bu (2), Ph (3), PhCH₂ (4)], R₃Sn(Hthpu) [R = Me (5), n-Bu (6), Ph (7), PhCH₂ (8)] and (R₂SnCl)₂ (dtpu) · L [L = H₂O, R = Me (9); L = 0: R = n-Bu (10), Ph (11), PhCH₂ (12)] have been synthesized, where tpu, Hthpu and dtpu are the anions of 6-thiopurine (Htpu), 2-thio-6-hydroxypurine (H₂thpu) and 2,6-dithiopurine (H₂dtpu), respectively. All the complexes 1-12 have been characterized by elemental, IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectra analyses. And complexes 1, 2, 7 and 9 have also been determined by X-ray crystallography, complexes 1 and 2 are both six-coordinated with R₂Sn coordinated to the thiol/thione S and heterocyclic N atoms but the coordination modes differed. As for complex 7 and 9, the geometries of Sn atoms are distorted trigonal bipyramidal. Moreover, the packing of complexes 1, 2, 7 and 9 are stabilized by the hydrogen bonding and weak interactions.     

Synthetic and X-ray diffraction studies of borosiloxane cages [R′Si(ORBO)3SiR′] and the adducts of [BuSi{O(PhB)O}3SiBu] with pyridine or N,N,N′,N′-tetramethylethylenediamine

Eleven borosiloxane [R′Si(ORBO)₃SiR′] compounds where R′ = Bu^t and R = Ph (1), 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), 4-CH(O)C₆H₄ (5), CpFeC₅H₄ (6), 4-C(O)CH₃C₆H₄ (7), 4-ClC₆H₄ (8), 2,4-F₂C₆H₃ (9), and R′ = cyclo-C₆H₁₁ and R = Ph (10), and 4-BrC₆H₄ (11) have been synthesized and characterized by spectroscopic (IR, NMR), mass spectrometric and, for compounds where R′ = Bu^t and R = 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), CpFeC₅H₄ (6) and 2,4-F₂C₆H₃ (9), X-ray diffraction studies. These compounds contain trigonal planar RBO₂ and tetrahedral R′SiO₃ units located around 11-atom “spherical” Si₂O₆B₃ cores. The dimensions of the Si₂O₆B₃ cores in compounds 2, 3, 4, 6 and 9 are remarkably similar. The reaction between [Bu^tSi{O(PhB)O}₃SiBu^t] (1), and excess pyridine yields the 1:1 adduct [Bu^tSi{O(PhB)O}SiBu^t]. NC₅H₅ (12) while the reaction between 1 and N,N,N′,N′-tetramethylethylenediamine in equimolar amounts affords a 2:1 borosiloxane:amine adduct [Bu^tSi{O(PhB)O}₃SiBu^t]₂ · Me₂NCH₂CH₂NMe₂ (13). Compounds 12 and 13 were characterised with IR and (¹H, ¹³C and¹¹B) NMR spectroscopies and the structure of the pyridine complex 12 was determined with X-ray techniques.     

Self-assembly syntheses and crystal structures of triorganotin(IV) pyridinecarboxylate: 1D polymers and a 42-membered macrocycle

A series of new triorganotin(IV) pyridinecarboxylates with 6-hydroxynicotinic acid (6-OH-3-nicH), 5-hydroxynicotinic acid (5-OH-3-nicH) and 2-hydroxyisonicotinic acid (2-OH-4-isonicH) of the types: [R₃Sn (6-OH-3-nic)·L]_n (I) (R = Ph, L = Ph·EtOH, 1; R = Bn, L = H₂O·EtOH, 2; R = Me, L = 0, 3; R = n-Bu, L = 0, 4), [R₃Sn (5-OH-3-nic)]_n (II) (R = Ph, 5; R = Bn, 6; R = Me, 7; R = n-Bu, 8), [R₃Sn (2-OH-4-isonic·L)]_n (III) (R = Bn, 9, L = MeOH; R = Me, L = 0, 10; R = Ph, 11, L = 0.5EtOH) have been synthesized. All the complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy analyses. Among them, except for complexes 5 and 6, all complexes were also characterized by X-ray crystallography diffraction analysis. Crystal structures show that complexes 1-10 adopt 1D infinite chain structures which are generated by the bidentate O, O or N, O and the five-coordinated tin centers. Significant O-H?O, and N-H?O intermolecular hydrogen bonds stabilize these structures. Complex 11 is a 42-membered macrocycle containing six tin atoms, and forms a 2D network by intermolecular N-H?O hydrogen.     

Synthesis and characterization of para-nitro substituted 2,6-bis(phenylimino)pyridyl Fe(II) and Co(II) complexes and their ethylene polymerization properties

Four iron(II) and cobalt(II) complexes ligated by 2,6-bis(4-nitro-2,6-R₂-phenylimino)pyridines, LMCl₂ (1: R = Me, M = Fe; 2: R = iPr, M = Fe; 3: R = Me, M = Co; 4: R = iPr, M = Co) have been synthesized and fully characterized, and their catalytic ethylene polymerization properties have been investigated. Among these complexes, the iron(II) pre-catalyst bearing the ortho-isopropyl groups (complex 2) exhibited higher activities and produced higher molecular weight polymers than the other complexes in the presence of methylaluminoxane (MAO). A comparison of 2 with the reference non-nitro-substituted catalyst (2,6-bis(2,6-diisopropylphenylimino)pyridyl)FeCl₂ (FeCat 5) revealed a modest increase of the catalytic activity and longer lifetime upon substitution of the para-positions with nitro groups (activity up to 6.0 × 10³ kg mol⁻¹ h⁻¹ bar⁻¹ for 2 and 4.8 × 10³ kg mol⁻¹ h⁻¹ bar⁻¹ for 5), converting ethylene to highly linear polyethylenes with a unimodal molecular weight distribution around 456.4 kg mol⁻¹. However, the iron(II) pre-catalyst 1 on changing from ortho-isopropyl to methyl groups displayed much lower activities (over an order of magnitude) than 2 under mild conditions. As expected, the cobalt analogues showed relatively low polymerization activities.     

Fe Spin crossover materials based on dissymmetrical N4 Schiff bases including 2-pyridyl and 2R-imidazol-4-yl rings: Synthesis,crystal structure and magnetic and Mössbauer properties

The synthesis and characterization of new symmetrical Fe^II complexes, [FeL^A(NCS)₂] (1), and [FeL^Bx(NCS)₂] (2–4), are reported (L^A is the tetradentate Schiff base N,N′-bis(1-pyridin-2-ylethylidene)-2,2-dimethylpropane-1,3-diamine, and L^Bx stands for the family of tetradentate Schiff bases N,N′-bis[(2-R-1H-imidazol-4-yl)methylene]-2,2-dimethylpropane-1,3-diamine, with: R = H for L^B1 in 2, R = Me for L^B2 in 3, and R = Ph for L^B3 in 4). Single-crystal X-ray structures have been determined for 1 (low-spin state at 293 K), 2 (high-spin (HS) state at 200 K), and 3 (HS state at 180 K). These complexes remain in the same spin-state over the whole temperature range [80–400 K]. The dissymmetrical tetradentate Schiff base ligands L^Cx, N-[(2-R₂-1H-imidazol-4-yl)methylene]-N′-(1-pyridin-2-ylethylidene)-2,2-R₁-propane-1,3-diamine (R₁ = H, Me; R₂ = H, Me, Ph), containing both pyridine and imidazole rings were obtained as their [FeL^Cx(NCS)₂] complexes, 5–10, through reaction of the isolated aminal type ligands 2-methyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = H, 5–7) or 2,5,5-trimethyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = Me, 8–10) with imidazole-4-carboxaldehyde (R₂ = H: 5, 8), 2-methylimidazole-4-carboxaldehyde (R₂ = Me: 6, 9), and 2-phenyl-imidazole-4-carboxaldehyde (R₂ = Ph: 7, 10) in the presence of iron(II) thiocyanate. Together with the single-crystal X-ray structures of 7 and 9, variable-temperature magnetic susceptibility and Mössbauer studies of 5–10 showed that it is possible to tune the spin crossover properties in the [FeL^Cx(NCS)₂] series by changing the 2-imidazole and/or C2-propylene susbtituent of L^Cx.     

Electronically variable imino-phenanthrolinyl-cobalt complexes; synthesis, structures and ethylene oligomerisation studies

The 2-imino-1,10-phenanthroline ligands, 1,10-C₁₂H₇N₂-2-CRN(2,6-i-Pr₂-4-R¹-C₆H₂) [R = R¹ = H (L1); R = H, R¹ = Br (L2); R = H, R¹ = CN (L3); R = H, R¹ = i-Pr (L4); R = Me, R¹ = H (L5); R = Me, R¹ = i-Pr (L6)], have been prepared in high yield from the condensation reaction of 1,10-C₁₂H₇N₂-2-CRO (R = H, Me) with one equivalent of the corresponding 4-substituted 2,6-diisopropylaniline. The molecular structures of L2, L5 and L6 reveal the imino nitrogen atoms to adopt a transoid configuration with respect to the phenanthrolinyl nitrogen atoms. Treatment of Lx with one equivalent of CoCl₂ in n-BuOH at 90 °C gives the high spin complexes, (Lx)CoCl₂ [Lx = L1 (1a), L2 (1b), L3 (1c), L4 (1d), L5 (1e), L6 (1f)], in which the metal centres exhibit distorted square pyramidal geometries. Activation of 1a-1f with excess methylaluminoxane (MAO) gives catalysts that are modestly active for the oligomerisation of ethylene affording mainly linear α-olefins along with some degree of internal olefins. While the donor capability of the 4-position of the N-aryl group does not appear to affect the activity of the catalyst, it does have an influence on the ratio of α-olefins to internal olefins. Single crystal X-ray diffraction studies have been performed on L2, L5, L6, 1a, 1c and 1f.