Cyclophosphazenes tethered together via N-ring centres with ortho-, meta- and para-xylylene linkers

Hexakis (organoamino) cyclotriphosphazenes (RNH)₆P₃N₃ {R = i-Bu (1), R = i-Pr (2)} react with ortho-, meta- and para-derivatives of α,α′-dibromo xylene in 2:1 ratio to form salts of compositions [{(RNH)₆P₃N₃}₂xyl]Br₂, {R = i-Bu, o-xyl (3); R = i-Pr, m-xyl (4); R = i-Pr, p-xyl (5)}. These contain dications consisting of two phosphazene rings, which are tethered together via ring N centres by a xylylene unit. X-ray structure analyses show that the substitution pattern at the xylylene bridge controls the orientation and distance between the two tethered phosphazene rings. The solid state structures exhibit dense networks of hydrogen bonds linking dications and anions. Direct N-H?N bonds between dications are observed in the crystal structure of 3.     

Facile synthesis of achiral and chiral PCN pincer palladium(II) complexes and their application in the Suzuki and copper-free Sonogashira cross-coupling reactions

Five non-symmetrical PCN pincer palladium(II) complexes [PdCl{C₆H₃-2-(CHNR)-6-()}] (R = m-ClC₆H₄, R′ = Ph (2a); R = Ph, R′ = Ph (2b); R = i-Pr, R′ = Ph (2c); R = m-ClC₆H₄, R′ = i-Pr (2d); R = (S)-1-phenylethyl, R′ = Ph (2e)) have been easily prepared in only two steps from readily available m-hydroxybenzaldehyde and characterized by HRMS, ¹H NMR, ¹³C NMR, ³¹P NMR and IR spectra. The molecular structures of 2a and 2b have been further determined by X-ray single-crystal diffraction. The obtained Pd complexes were found to be effective catalysts for the Suzuki and copper-free Sonogashira cross-coupling reactions which could be carried out in the undried solvent under air.     

Titanium complexes bearing aromatic-substituted β-enaminoketonato ligands: Syntheses, structure and olefin polymerization behavior

A series of titanium complexes [(Ar)NC(CF₃)CHC(R)O]₂TiCl₂ (4b: Ar = -C₆H₄OMe(p), R = Ph; 4c: Ar = -C₆H₄Me(p), R = Ph; 4d: Ar = -C₆H₄Me(o), R = Ph; 4e: Ar = α-Naphthyl, R = Ph; 4f: Ar = -C₆H₅, R = t-Bu; 4g: Ar = -C₆H₄OMe(p); R = t-Bu; 4h: Ar = -C₆H₄Me(p); R = t-Bu; 4i: Ar = -C₆H₄Me(o); R = t-Bu) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4b, 4c and 4h adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b-c and 4f-i are active catalysts for ethylene polymerization and ethylene/norbornene copolymerization, and produce high molecular weight polyethylenes and ethylene/norbornene alternating copolymers. In addition, the complex 4c/MMAO catalyst system exhibits the characteristics of a quasi-living copolymerization of ethylene and norbornene with narrow molecular weight distribution.     

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.     

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.     

Orthopalladation of phosphorus ylides in endo position with bidentate ligands

The ortho-metallated complexes [Pd₂{κ²(C,C)-C₆H₄(PPh₂CHC(O)C₆H₅R}₂(μ-Cl)₂] (R = Ph (1a), NO₂ (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph₃PCHC(O)C₆H₅R, (R = Ph, NO₂, Br) and Pd(OAc)₂ in MeOH, followed by an excess of NaCl. The dinuclear complexes (1a-1c) react with silver trifluoromethylsulfonate and bidentate ligands [L = bipy (2,2′-bipyridine), phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), dppp (bis(diphenylphosphino)propane)] giving the mononuclear stabilized orthopalladated complexes in endo position [Pd{κ²(C,C)-C₆H₄(PPh₂CHC(O)R}L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO₂, L = phen (2b), bipy (3b), dppe (4b), dppp (5b); R = Br, L = phen (2c), bipy (3c), dppe (4c), dppp (5c); OTf = trifluoromethylsulfonate anion]. Orthometalation and ylidic C-coordination are demonstrated by an X-ray diffraction study of 2c and 3c. In the structures, the palladium atom shows a slightly distorted square-planar coordination geometry.     

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.     

Allylpalladium (II) complexes with dichalcogenoimidodiphosphinate ligands: Synthesis, structure, spectroscopy and their transformation into palladium chalcogenides

The synthesis, characterization and thermal behavior of new monomeric allylpalladium (II) complexes with dichalcogenoamidodiphosphinate anions are reported. The complexes [R = H, R′ = Prⁱ, E = S (1a); R = H, R′ = Prⁱ, E = Se (1b); R = H, R′ = Ph, E = S (1c); R = H, R′ = Ph, E = Se (1d); R = Me, R′ = Prⁱ, E = S (2a); R = Me, R′ = Prⁱ, E = Se (2b); R = Me, R′ = Ph, E = S (2c); R = Me, R′ = Ph, E = Se (2d)] have been prepared by room temperature reaction of [Pd(η³-CH₂C(R)CH₂)(acac)] (acac = acetylacetonate) with dichalcogenoimidodiphosphinic acids in acetonitrile solution. The complexes have been characterized by multinuclear NMR (¹H, ¹³C{¹H}, ³¹P{¹H}, ⁷⁷Se{¹H}), FT-IR and elemental analyses. The crystal structures of complexes 1a, 1d and 2d have been reported and they consist of a six-membered PdE₂P₂N ring (E = S for 1a and Se for 1d and 2d) and an allyl group, C₃H₄R(R = H for 1a and 1d and Me for 2d). Thermogravimetric studies have been carried out for few representative complexes. The complexes thermally decompose in argon atmosphere to leave a residue of palladium chalcogenides, which have been characterized by PXRD, SEM and EDS.     

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.     

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

An efficient route to the novel tridentate phosphine ligands RP[CH₂CH₂CH₂P(OR′)₂]₂ (I: R = Ph; R′ = i-Pr; II: R = Cy; R′ = i-Pr; III: R = Ph; R′ = Me and IV: R = Cy; R′ = Me) has been developed. The corresponding ruthenium and iron dicarbonyl complexes M(triphos)(CO)₂ (1: M = Ru; triphos = I; 2: M = Ru; triphos = II; 3: M = Ru; triphos = III; 4: M = Ru; triphos = IV; 5: M = Fe; triphos = I; 6: M = Fe; triphos = II; 7: M = Fe; triphos = III and 8: M = Fe; triphos = IV) have been prepared and fully characterized. The structures of 1, 3 and 5 have been established by X-ray diffraction studies. The oxidative addition of MeI to 1-8 produces a mixture of the corresponding isomeric octahedral cationic complexes mer,trans-(13a-20a) and mer,cis-[M(Me)(triphos)(CO)₂]I (13b-20b) (M = Ru, Fe; triphos = I-IV). The structures of 13a and 20a (as the tetraphenylborate salt (21)) have been verified by X-ray diffraction studies. The oxidative addition of other alkyl iodides (EtI, i-PrI and n-PrI) to 1-8 did not afford the corresponding alkyl metal complexes and rather the cationic octahedral iodo complexes mer,cis-[M(I)(triphos)(CO)₂]I (22-29) (M = Ru, Fe; triphos = I-IV) were produced. Complexes 22-29 could also be obtained by the addition of a stoichiometric amount of I₂ to 1-8. The structure of 22 has been verified by an X-ray diffraction study. Reaction of 13a/b-20a/b with CO afforded the acetyl complexes mer,trans-[M(COMe)(triphos)(CO)₂]I, 30-37, respectively (M = Ru, Fe; triphos = I-IV). The ruthenium acetyl complexes 30-33 reacted slowly with 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) even in boiling acetonitrile. Under the same conditions, the deprotonation reactions of the iron acetyl complexes 34-37 were completed within 24-40 h to afford the corresponding zero valent complexes 5-8. It was not possible to observe the intermediate ketene complexes. Tracing of the released ketene was attempted by deprotonation studies on the labelled species mer,trans-[Fe(COCD₃)(triphos)(CO)₂]I (38) and mer,trans-[Fe(¹³COMe)(triphos)(CO)₂]I (39).     

Dimeric and trimeric diorganosilicon chalcogenides (PhRSiE)2,3 (E = S, Se, Te; R = Ph, Me)

Ph₂SiCl₂ and PhMeSiCl₂ react with Li₂E (E = S, Se, Te) under formation of trimeric diorganosilicon chalcogenides (PhRSiE)₃ (R = Ph: 1a-3a, R = Me: cis/trans-4a (E = S), cis/trans-5a (E = Se)). In case of E = S, Se dimeric four-membered ring compounds (PhRSiE)₂ (R = Ph: 1b-2b, R = Me: cis/trans-4b (E = S), cis/trans-5b (E = Se)) have been observed as by-products. 1a-5b have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ⁷⁷Se, ¹²⁵Te). Four- and six-membered ring compounds differ significantly in ²⁹Si and ⁷⁷Se chemical shifts as well as in the value of ¹J_SiSe.The molecular structures of 2a, 3a and trans-5a reported in this paper are the first examples of compounds with unfused six-membered rings Si₃E₃ (E = Se, Te). The Si₃E₃ rings adopt twisted boat conformations. The crystal structure of 3a reveals an intermolecular Te-Te contact of 3.858 Å which yields a dimerization in the solid state.     

Structural diversity of di and triorganotin complexes with 4-sulfanylbenzoic acid: Supramolecular structures involving intermolecular Sn?O, O-H?O or C-H?X (X = O or S) interactions

Twelve new organotin complexes with 4-sulfanylbenzoic acid of two types: R_nSn[S(C₆H₄COOH)]_4−n (I) (n = 3: R = Me 1, n-Bu 2, Ph 3; PhCH₂4; n = 2: R = Me 5; n-Bu 6, Ph 7, PhCH₂8) and R₃Sn(SC₆H₄COO)SnR₃ · mEtOH (II) (m = 0: R = Me 9, n-Bu 10, PhCH₂12; m = 2: R = Ph 11), along with the 4,4′-bipy adduct of 9, [Me₃Sn(SC₆H₄COO)SnMe₃]₂(4,4-bipy) 13, have been synthesized. The coordination behavior of 4-sulfanylbenzoic acid is monodentate in 1-8 by thiol S atom but not carboxylic oxygen atom. While, in 9-13 it behaves as multidenate by both thiol S atom and carboxylic oxygen atoms. The supramolecular structures of 6, 11 and 13 have been found to consist of 1D molecular chains built up by intermolecular O-H?O, C-H?O or C-H?S hydrogen bonds. The supramolecular aggregation of 7 is 2D network determined by two C-H?O hydrogen bonds. Extended intermolecular C-H?O interactions in the crystal lattice of 9 link the molecules into a 2D network.     

Reactions of trimethylsiloxychlorosilanes with lithium metal - On the mechanism of the formation of trimethylsiloxysilyllithium compounds LiSiRR’(OSiMe3)

The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me₃SiO)RR′SiLi (2a: R = Et, 2b: R = ⁱPr, 2c: R = 2,4,6-Me₃C₆H₂ (Mes); 2a-c: R′ = Ph; 2d: R = R′ = Mes) starting from the conversion of the corresponding trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-d) in the presence of excess lithium in a mixture of THF/diethyl ether/n-pentane at −110 °C was investigated.The trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a: R = Et, 1b: R = ⁱPr, 1c: R = Mes) react with lithium to give initially the trimethylsiloxysilyllithium compounds (Me₃SiO)RPhSiLi (2a-c). These siloxysilyllithiums 2 couple partially with more trimethylsiloxychlorosilanes 1 to produce the siloxydisilanes (Me₃SiO)RPhSi-SiPhR(OSiMe₃) (Ia-c), and they undergo bimolecular self-condensation affording the trimethylsiloxydisilanyllithium compounds (Me₃SiO)RPhSi-RPhSiLi (3a-c). The siloxydisilanes I are cleaved by excess of lithium to give the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2). In the case of the two trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a: R = Et, 3b: R = ⁱPr) a reaction with more trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a, 1b) takes place under formation of siloxytrisilanes (Me₃SiO)RPhSi-RPhSi-SiPhR(OSiMe₃) (IIa: R = Et, IIb: R = ⁱPr) which are cleaved by lithium to yield the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2a, 2b) and the trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a, 3b). The dimesityl-trimethylsiloxy-silyllithium (Me₃SiO)Mes₂SiLi (2d) was obtained directly by reaction of the trimethylsiloxychlorosilane (Me₃SiO)Mes₂SiCl (1d) and lithium without formation of the siloxydisilane intermediate. Both silyllithium compounds 2 and 3 were trapped with HMe₂SiCl giving the products (Me₃SiO)RR′Si-SiMe₂H and (Me₃SiO)RPhSi-RPhSi-SiMe₂H.     

Syntheses, characterization and crystal structures of di- and triorganotin (IV) derivatives with 6-amino-1,3,5-triazine-2,4-dithiol

A series of organotin (IV) complexes with 6-amino-1,3,5-triazine-2,4-dithiol of the type [(R_nSnCl_4−n)₂ (C₃H₂N₄S₂)] (n = 3: R = Me 1, n-Bu 2, PhCH₂3, Ph 4; n = 2: R = Me 5, n-Bu 6, PhCH₂7, Ph 8) have been synthesized. All the complexes 1-8 have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectra. Among them complexes 1, 4, 5 and 8 have also been characterized by X-ray crystallography diffraction analyses, which revealed that the tin atoms of complexes 1, 4, 5 and 8 are all five-coordinated with distorted trigonal bipyramid geometries.     

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.     

Syntheses, characterizations and crystal structures of new organoantimony(V) complexes with heterocyclic (S, N) ligand

Eight new organoantimony(V) complexes with 1-phenyl-1H-tetrazole-5-thiol [L¹H] and 2,5-dimercapto-4-phenyl-1,3,4-thiodiazole [L²H] of the type R_nSbL_5 − n (L = L¹: n = 4, R = n-Bu 1, Ph 2, n = 3, R = Me 3, Ph 4; L = L²: n = 4, R = n-Bu 5, Ph 6, n = 3, R = Me 7, Ph 8) have been synthesized. All the complexes 1-8 have been characterized by elemental, FT-IR, ¹H and ¹³C NMR analyses. Among them complexes 2, 6 and 8 have also been confirmed by X-ray crystallography. The structure analyses show that the antimony atoms in complexes 2 and 6 display a trigonal bipyramid geometry, while it displays a distorted capped trigonal prism in complex 8 with two intramolecular Sb?N weak interactions. Furthermore, the supramolecular structure of 2 has been found to consist of one-dimensional linear molecular chain built up by intermolecular C-H?N weak hydrogen bonds, while a macrocyclic dimer has been found in complex 6 linked by intermolecular C-H?S weak hydrogen bonds with head-to-tail arrangement. Interestingly, one-dimensional helical chain is recognized in complex 8, which is connected by intermolecular C-H?S weak hydrogen bonds.     

New alkenyl-substituted group 4 C-ansa-metallocene complexes. Reactivity of the substituent at the carbon ansa bridge

The allyl-substituted group 4 metal complexes [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti, R = CH₂CHCH₂, (2); R = CH₂C(CH₃)CH₂ (3); M = Zr, R = CH₂CHCH₂ (4), R = CH₂C(CH₃)CH₂ (5)] have been synthesized by the reaction of allyl ansa-magnesocene derivatives and the tetrachloride salts of the corresponding transition metal. The dialkyl complexes ] [M = Ti, R = CH₂=CHCH₂, R′ = Me (6), R′ = CH₂Ph (7); R = CH₂C(CH₃)CH₂, R′ = Me (8), R′ = CH₂Ph (9); M = Zr, R = CH₂CHCH₂, R′ = Me (10), R′ = CH₂Ph (11); R = CH₂C(CH₃)CH₂, R′ = Me (12), R′ = CH₂Ph (13)] have been synthesized by the reaction of the corresponding ansa-metallocene dichloride complexes 2-5 and two molar equivalents of the alkyl Grignard reagent. Compounds 2-5 reacted with H₂ under catalytic conditions (Wilkinson’s catalyst or Pd/C) to give the hydrogenation products [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = CH₂CH₂CH₃ (14) or R = CH₂CH(CH₃)₂ (15); M = Zr and R = CH₂CH₂CH₃ (16) or R = CH₂CH(CH₃)₂ (17)]. The reactivity of 2-5 has also been tested in hydroboration and hydrosilylation reactions. The hydroboration reactions of 3, 4 and 5 with 9-borabicyclo[3.3.1]nonane (9-BBN) yielded the complexes [M{(9-BBN)CH₂CH(R)CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (18); M = Zr and R = H (19) or R = CH₃ (20)]. The reaction with the silane reagents HSiMe₂Cl gave the corresponding [M{ClMe₂SiCH₂CHRCH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (21); M = Zr and R = H (22) or R = CH₃ (23)]. The reaction of 22 with t-BuMe₂SiOH produced a new complex [Zr{t-BuMe₂SiOSi(Me₂)CH₂CH₂CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (24) through the formation of Si-O-Si bonds. On the other hand, reactivity studies of some zirconocene complexes were carried out, with the insertion reaction of phenyl isocyanate (PhNCO) into the zirconium-carbon σ-bond of [Zr{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}₂Me₂] (25) giving [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr{Me{κ²-O,N-OC(Me)NPh}] as a mixture of two isomers 26a-b. The reaction of [Zr{(n-Bu)(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}(CH₂Ph)₂] (27) with CO also provided a mixture of two isomers [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr(CH₂Ph){κ²-O,C-COCH₂Ph}] 28a-b. The molecular structures of 4, 11, 16 and 17 have been determined by single-crystal X-ray diffraction studies.     

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.     

Synthesis, structure and ethylene polymerization behavior of titanium phosphinoamide complexes

(Phosphinoamide)(cyclopentadienyl)titanium(IV) complexes of the type Cp*TiCl₂(η²-Ph₂PNR) [Cp*=C₅Me₅; R = t-Bu (2a), R = n-Bu (2b), R = Ph (2c)] have been prepared by the reaction of Cp*TiCl₃ with the corresponding lithium phosphinoamides. The structure of Cp*TiCl₂(η²-Ph₂PN^tBu) (2a) and Cp*TiCl₂(η²-Ph₂PNPh) (2c) have been determined by X-ray crystallography. These complexes exhibited moderate catalytic activities for ethylene polymerization in the presence of modified methylaluminoxane (MMAO). Catalytic activity of up to 2.5 × 10⁶ g/(mol Ti h) was observed when activated by i-Bu₃Al/Ph₃CB(C₆F₅)₄.     

Ruthenium vinylidene and carbyne complexes containing a multifunctional tridentate ligand with a PNN donor set

The neutral, octahedral ruthenium vinylidene complexes mer,trans-[(PNN)Cl₂Ru(CCHR)] (PNN = N-(2-diphenylphosphinobenzylidene)-2-(2-pyridyl)ethylamine; R = Ph, 1a; R = ^tBu, 1b) are reported. An X-ray crystallographic study of 1a confirms the tridentate, meridional coordination mode of the PNN ligand. Compounds 1a and 1b undergo regioselective electrophilic addition with HBF₄ · Et₂O at C_β of the vinylidene ligand at low temperatures, and are cleanly and quantitatively converted to the ruthenium carbynes mer,trans-[(PNN)Cl₂Ru(CCH₂R)][BF₄] (R = Ph, 2a; R = ^tBu, 2b). Carbynes 2a and 2b are stable only at low temperatures (<−50 °C). Complex 1a undergoes ligand substitution with L to yield mer,trans-[(PNN)Cl₂Ru(L)] (L = MeCN, 3a; L = CO, 3b).