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Cu(II) salen (salen = N,N′-ethylene-bis(salicylideneimine)) complexes bearing alkoxy chains of C12 (1) and C10 (2) in the salicylidene moieties were synthesized and subsequently characterized by several independent methods: single crystal X-ray diffraction, infrared spectroscopy, mass spectrometry, and UV-Vis spectroscopy. The solid state structures show that the spatial orientation and packing of the complexes are not affected by the alkyl chain length but by a coordinated solvent molecule, as demonstrated by the structure of 1 having methanol in an axial position.

The brown crystals of [PMePh3]2[Se2Br6] (1) and red crystals of [PMePh3]2[SeBr6(SeBr2)2] (2) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of methyltriphenylphosphonium bromide. The crystal structures of 1 and 2 has been determined by the X-ray methods and refined to R = 0.0373 for 2397 reflections and 0.0397 for 3417 reflections, respectively. The salt 1 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 13.202(5) A, b = 11.954(4) A, c = 13.418(6) A, β = 93.08(4)° (193(2)). The crystals of 2 are triclinic, space group with the cell dimensions a = 10.266(3) A, b = 11.311(3) A, c = 11.619(2) A, α = 108.87(2)°, β = 105.72(2)°, γ = 99.40(2)° (193(2) K). In the solid state structure of 1 the dinuclear hexabromo-diselenate(II) anion is centrosymmetric and consists of two distorted almost square planar SeBr4 units sharing a common edge through two μ-bridging Br atoms. The terminal SeII–Br bonds are 2.3984(11) and 2.4273(11) A, whereas the bridging μBr–SeII bonds are 2.7817(11) and 2.9081(12) A. In the solid state the trinuclear [SeBr6(SeBr2)2]2− anion of 2 is centrosymmetric too and contains a nearly regular [SeBr6] octahedron where the four equatorial bromo ligands each have developed bonds to the SeII atoms of the SeBr2 molecules. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are 3.0603(15) and 3.1043(12) A, and can be interpreted as bonds of the donor-acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The SeIV–Br distances are in the range 2.5570(9)–2.5773(11) A and the SeII–Br bond lengths in coordinated SeBr2 molecules – 2.3411(12) and 2.3421(10) A.

Three titanium complexes derived from 2-(2,6-difluoroanilino)pyridine and 2-(2-chloroanilino)pyridine were synthesized and characterized by X-ray diffraction or spectroscopic methods. All titanium complexes have been used to catalyze the polymerization of ethylene in the presence of MAO as cocatalyst. The mono(2,6-difluorophenylaminopyridinato) titanium catalyst was found to be more active in ethylene polymerization than the bis(2,6-difluorophenylaminopyridinato) and bis(2-chlorophenylaminopyridinato) titanium catalysts. ortho-Halogens disturbed the β-elimination transition state of ethylene polymerization and formed higher molar mass polyethylene than their unhalogenated congener. Due to fluxionality, the bis(2-chlorophenylaminopyridinato) titanium catalyst formed broader molar mass distribution than the bis(2,6-difluorophenylaminopyridinato) titanium catalysts.

Titanium complexes bearing anionic [N,O-] bidentate salicylaldiminato ligands were synthesized with excellent yields via one- or two-step processes. The common feature of these catalyst precursors is the presence of aliphatic substituents (adamantyl, benzyl, (CH2)2Ph, (CH2)3Ph, and i-Pr) at the aldimino moieties. X-ray structure analysis of the benzyl-substituted complex revealed a distorted octahedral geometry, wherein nitrogen and chlorine atoms form the basal plane while the oxygen atoms of the phenoxy moieties complete the coordination sphere of the Ti center by occupying the axial positions. However, according to dynamic 1H NMR measurements, these complexes can possess different structural isomers in solution, even at room temperature. After MAO activation, the catalysts displayed a range of catalytic activities [3−1700 kgPE/(molTi·h·bar)]. The complex with ethylphenyl substituents was the most active in the series. In general, the (CH2)2Ph- and (CH2)3Ph-substituted catalysts produce PE with unimodal...

Hf bis(phenoxyimino) dibenzyl complexes bearing benzylimino and perfluorophenylimino groups were prepared by a direct reaction between the desired ligand precursors and Hf(CH2Ph)4. In the solid sta...

A series of manganese(II) dichloro complexes made in situ and bearing mainly various nitrogen ligands was studied with a parallel screening method in order to identify catalytically active complexes for ethene polymerization using methylaluminoxane (MAO) as a cocatalyst. From the series two of the most active octahedral manganese(II) complexes, those bearing tetradentate nitrogen ligands with chiral bridges, [N,N‘-bis(quinoline-2-methylene)diiminocyclohexane]MnCl2 (1) and {N,N‘-(6,6‘-dimethylbiphenyl-2,2‘-diyl)bis[(2-pyridyl)methyl]diimine}MnCl2 (2), were selected for more detailed studies. According to their solid-state structures, it is common for these C2-symmetric manganese complexes to have a distorted-octahedral coordination geometry where chlorides occupy cis positions with wide Cl−Mn−Cl angles (132−135°). The highest activity in ethene polymerization (67 kg of PE/((mol of Mn) h)) was obtained with 1/MAO at 80 °C. Furthermore, the alkylation of 1 and 2 with MeMgBr and (benzyl)MgBr was investigated,...

Benzyl-substituted bis(amido)cyclodiphosph(III)azane complexes [(RN)(t-BuNP)]2M(CH2Ph)nCl2-n (M = Zr, Ti; n = 1, 2) bearing t-Bu or bulky aryl substituents on amido nitrogens were prepared by direc...

A series of titanium complexes bearing two anionic [N, O–] bidentate salicylaldiminato ligands, namely bis[(N-salicylidene)anilinato]titanium(IV) dichloride (1), bis[(N-salicylidene)-2,6-dimethylanilinato]titanium(IV) dichloride (2), bis[(N-salicylidene)-2,6-di-i- propylanilinato]titanium(IV) dichloride (3), bis[(N-salicylidene)-(1-naphthalenylimino)]titanium(IV) dichloride (4), bis[(N-salicylidene)-2,6-difluoroanilinato]titanium(IV) dichloride (5), and bis[(N-3-fluorosalicylidene)-2,6-difluoroanilinato]titanium(IV) dichloride (6) have been synthesized with good yields by a two-step procedure. The X-ray structure analysis reveals that in complex 2, titanium has a distorted octahedral coordination sphere in which the oxygen atoms and the chloride ligands form the basal plane. Both the chloride and the phenoxy moieties have a cis orientation and the angle between the chloride ligands is 93.05°. The imine nitrogen atoms complete the octahedral coordination of the Ti center by occupying the axial positions. The newly synthesized (2 and 4–6) and already known complexes (1 and 3) were introduced in detailed ethene-polymerization studies. The activities achieved were low to moderate depending on the size and nature of the imino substituents. The polyethenes (PEs) produced had high molar masses, and the modalities of the molecular weight distributions varyied with polymerization temperature. Based on the results of ab initio calculations and on the experimental data obtained, an explanation for uni- and bimodal polymerization behavior and the differences in catalytic activities are given. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Three 2-phenylaminopyridine (Ap) complexes of types ApTiCl3 and Ap2TiCl2 were characterized with X-ray diffraction. The complexes were studied as polymerization catalysts using MAO as cocatalyst. In ethylene polymerization, the catalysts showed moderate activities between 65 and 285 kg PE mol−1 Ti−1 h−1 and the molecular weight distributions were between 2.5 and 4.2, and the molar masses were between 135 000 and 804 000 kg/mol.

Bis(amido) hafnium complexes [(RN)(t-BuNP)]2HfCl2 (R = 2,6-i-Pr2C6H3 (5), 2,5-t-Bu2C6H3 (6)) bearing a N-tert-butyl cyclodiphosph(III)azane bridge were prepared by direct metalation of corresponding ligand precursors with Hf(NMe2)4 followed by chlorination by Me3SiCl. Complexes 5 and 6 and the already known [(t-BuN)(t-BuNP)]2HfCl2 (4) were subsequently converted to their methyl derivatives [(RN)(t-BuNP)]2HfMe2 by the alkylation by MeMgBr in Et2O. The solid state structure of [(t-BuN)(t-BuNP)]2HfMe2 (7) reveals a highly distorted trigonal-bypiramidal configuration at the metal center. Activation of the dimethyl complexes with B(C6F5)3 led to the generation of corresponding cationic species, which were investigated by 1H, 13C, 31P, and 19F NMR. In the solid state, the metal center of {[(t-BuN)(t-BuNP)]2HfMe(μ-Me)B(C6F5)3} has a distorted trigonal-bypiramidal configuration and the [MeB(C6F5)3]- anion is only weakly coordinated with cationic hafnium. In deuterobenzene solution {[(t-BuN)(t-BuNP)]2HfMe(μ-Me)B(C...

The meso - and rac -like isomers of bis{η 5 -(1-benzyl)indenyl}zirconium dichloride ( 5 ), bis{η 5 -(1- para -methoxybenzyl)indenyl}zirconium dichloride ( 6 ), bis{η 5 -(1- para -fluoro-benzyl)indenyl}zirconium dichloride ( 7 ) and bis{η 5 -(1-phenylethyl)indenyl}zirconium dichloride ( 8 ) were synthesized and isolated. Solid-state structures of meso - and rac -like 5 were determined by X-ray structure analysis. Polymerization properties of the methylaluminoxane (MAO) activated diastereomers of complexes 5 – 8 were studied in ethene polymerizations under different monomer concentrations. The rac -like isomer of 1-phenylethyl-substituted 8 /MAO showed significantly higher activity than the 1-benzyl substituted analogs 5 – 7 /MAO. In addition, rac - 8 /MAO behaves like a single center catalyst producing polyethene with narrow molar mass distribution (1.8–1.9), while diastereomers of 5 – 7 /MAO produce polymers with molar mass distributions varying from 2.7 up to 10.3. The rac and meso -like isomers of 5 – 7 /MAO have different response on the monomer concentration. Quantum chemical calculations suggest a strong interaction between the benzyl substituent and the electron deficient zirconium center. The phenyl metal coordination energies depend on the electronic properties of the para -substituent. In 8 /MAO, due to the ethyl spacer, the coordination does not have a significant role and therefore much higher activity and single center polymerization behavior is observed.

A series of new zirconium dichloride complexes bearing bulky cis-bis(amino)cyclodiphosph(III)azane ligands, [(RN)2(tBuNP)2]ZrCl2 [R = phenyl (7), diphenylmethyl (8), 2,6-diethylphenyl (9), 2,5-di-tert-butylphenyl (10), and 2,6-diisopropylphenyl (11)] were prepared in high yields by a two-step synthetic route. The structure of cis-[(Ph2CHN)(tBuNP)]2Zr(NMe2)2 (8a), determined by X-ray analysis, shows that the zirconium atom has a distorted trigonal-bipyramidal configuration consisting of four equidistant metal−amido nitrogen bonds and an additional coordination between the metal and a nitrogen atom from the cyclodiphosph(III)azane ring. After methylaluminoxane activation, these complexes exhibit moderate to high activities in ethene polymerization and produce high molar mass polyethene (Mw up to 1100 kg/mol). Polymerization experiments reveal that the behavior of bis(amido)cyclodiphosph(III)azane-based ZrIV catalysts depends on the nature and steric bulkiness of the amido substituents, reaction temperature, MAO/zirconium ratio, as well as monomer pressure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The dual-site zirconocene dichlorides rac- and meso-SiMe2(3-benzylindenyl)(indenyl)ZrCl2 have been synthesized and used, after a methylaluminoxane activation, in propene polymerization. These diastereomers produce isotactic polypropenes with similar microstructures and molar masses under equivalent polymerization conditions.

Bis(amino)cyclodiphosph(III)azanes cis-[(RNH)(PN-tBu)]2, R = 2,6-iPr2C6H3 (2), 2-tBuC6H4 (3), 2-CF3C6H4 (4), 2,5-tBu2C6H3 (5), Ph2CH (6), 2,4-Me2C6H3 (7), 2,6-Et2C6H3 (8), have been synthesized in the presence of Et3N by a nucleophilic substitution reaction of cis-(ClPN-tBu)2 (1) with the corresponding bulky aryl and alkylamines. The bis(amino)cyclodiphosph(III)azanes 2−8 adopt the thermodynamically stable cis-configuration − a prerequisite for efficient metal complex formation. Deprotonation of bis(amino)cyclodiphosph(III)azanes with nBuLi slowly afforded the corresponding salts, cis-[(2,4-Me2C6H3N)(PN-tBu)]2Li2(THF)2. The crystal structure of cis-[(2,4-Me2C6H3N)(PN-tBu)]2Li2(THF)2 (9) consists of a heterocube of two lithium atoms, two nitrogen atoms and a cyclodiphosph(III)azane ring. Transmetallation of Li compounds by TiCl4 was unselective and led to a complex mixture of products. The direct reaction of cis-bis(amino)cyclodiphosph(III)azanes with Ti(NMe2)4 is the most efficient method to prepare the corresponding titanium(IV) bis-amido complexes cis-[(RN)(PNtBu)]2Ti(NMe2)2 (11a, 12a, 14a, 15a). In the solid state, cis-[(PhN)(PN-tBu)]2Ti(NMe2)2 (11a) adopts a highly distorted trigonal-bipyramidal configuration at the metal center. These bis-amido titanium(IV) complexes have been subsequently transformed into the dichlorides cis-[(RN)(PN-tBu)]2TiCl2 (12−15) with Me3SiCl. After MAO activation the complexes possess moderate catalytic activity in ethene polymerization and produce linear polyethylene with molar masses of up to 2.6 × 106 g/mol and with narrow polydispersities. The catalytic activity and polymer properties depend strongly on the bulkiness of the ligand substituents; cis-[(2,6-iPr2C6H3N)(PN-tBu)]2TiCl2 (14) gave the highest activity (231 kg PE/molcat × bar × h). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Five new nonsymmetric 1-diphenylphosphino-3-{bis[aryl]phosphino}propane ligands 1b−f [aryl: b = 3,5-bis(trifluoromethyl)phenyl, c = 3,5-dimethylphenyl, d = 3,5-difluorophenyl, e = 2-(trifluoromethyl)phenyl, f = 2,4,6-trifluorophenyl] and their corresponding neutral dichloro palladium(II) 2b−f, diiodo palladium(II) 3d,e, and dicationic diacetonitrile palladium(II) ditetrafluoroborate complexes 4b−f were synthesized. The symmetric ligand 1,3-bis{bis[3,5-bis(trifluoromethyl)phenyl]phosphino}propane (1a) and the related palladium(II) complexes 2a and 4a were prepared for comparison. Solid state structures of new ligands were determined by X-ray structure analysis in the form of the dichloro (2a−c,f) and diiodo (3d,e) compounds. The properties of the symmetric (4a) and nonsymmetric catalysts (4b−f) were tested in propene/CO copolymerization experiments. A clear correlation between primarily steric effects of these ligands and the catalyst activity as well as the molecular weight of the resulting polyketone ma...

Synthesis and polymerization data of a series of new sulfur-containing C1-symmetric metallocenes, rac-[1-(9-η5-fluorenyl)-2-(2-methylbenzo[b]indeno[4,5-d]thiophen-1-η5-yl)ethane]zirconium dichloride (7a), rac-[1-(9-η5-fluorenyl)-2-(2-methylbenzo[b]indeno[4,5-d]thiophen-1-η5-yl)ethane]hafnium dichloride (7b), rac-[1-(9-η5-fluorenyl)-2-(2-methylbenzo[b]indeno[4,5-d]thiophen-1-η5-yl)ethane]hafnium dimethyl (7c), and rac-[1-(9-η5-fluorenyl)-2-(2-methylbenzo[b]indeno[4,5-d]thiophen-3-η5-yl)ethane]zirconium dichloride (8), are reported. The characteristic structural feature of these complexes is the 2-methyl-1H-benzo[b]indeno[4,5-d]thiophene moiety (3: MBIT), which was derived from dibenzothiophene. In the case of 7a−c the MBIT unit shows a “back” orientation, whereas in 8 it is directed to the “front” of the tetrahedral metallocene dichloride species, which was unambiguously illustrated by X-ray structure analysis. Propylene polymerization experiments revealed higher activity and stereoselectivity for 7a/MAO ...

The nucleophilic substitution reaction of the enantiomerically pure ligand, (1R,2R)-(−)-1,2-diaminocyclohexane [DACH] (1) with cis-bis(benzonitrile)palladium(II) dichloride [(PhCN)2PdCl2] leads to the formation of the complex [(DACH)PdCl2] (2) in a high yield. The reaction of the corresponding platinum(II) complex [(PhCN)2PtCl2] with DACH, under the same reaction conditions, surprisingly, took a different course, in which nucleophilic addition to the benzonitrile ligand occurred forming an enantiomerically pure amidine complex [(PhCNHNH(C6H10)NH2)Pt(NCPh)Cl]Cl (3), where the nitrogen ligand form a seven-membered chelate around the central atom. The aqua and oxalato derivatives of complex 2, [(DACH)Pd(H2O)2](NO3)2 (4) and [(DACH)Pd(C2O4)] (5) have also been prepared and characterized. The platinum analogue complex to 5, [(DACH)Pt(C2O4)] (6), was prepared starting from the enantiomerically pure isomer (1) and the platinum salt K2PtX4 (X=Cl, I). According to X-ray structural analysis carried out on the complex, the product does not consist of just the desired isomer, but a mixture of both the trans-l (trans-(−)-1R,2R) and trans-d (trans-(+)-1S,2S) isomers. No retention of optical isomerism was observed. The single crystal structural analysis was also carried out on the ligand N,N′-(1R,2R)-(−)-diaminocyclohexane dihydrochloride (DACH·2HCl)] (1a). The result indicates, however, that only the R,R-isomer exists in the free ligand.

Schiff-base condensation of diethylenetriamine with a series of dialdehydes [isophthalaldehyde (2a), 5-tert-butylisophthalaldehyde (2b), 2-methylisophthalaldehyde (2c), and p-phthalaldehyde (2d)] affords four hexaaza macrocyclic ligands [LH,H (3a), LtBu,H (3b), LH,Me (3c), Lp-H,H (3d)] bearing different substituents on the aromatic units that connect the two metal ion binding sites. The dinuclear copper(I) complexes [LH,HCu2(MeCN)2](ClO4)2 (4a), [LtBu,HCu2(MeCN)2](ClO4)2 (4b), [LH,MeCu2(MeCN)2](ClO4)2 (4c), and [Lp−H,HCu2(MeCN)2](CF3SO3)2 (4d) are obtained in good yields by reaction with CuI salts. X-ray diffraction studies performed on 4a and 4d reveal a distorted tetrahedral coordination geometry around each CuI ion, which is constructed by three nitrogen donors of the macrocyclic ligand and one acetonitrile solvent molecule. Treatment of these complexes with molecular dioxygen shows that their reactivity can be fine-tuned by the nature of the aromatic unit of the dialdehyde building blocks. Thus two different dinuclear CuII complexes resulting from the reaction of 4a and 4b with dioxygen were isolated and characterized by single crystal X-ray diffraction, XPS and magnetic measurements. The introduction of a methyl group in the 2-position of the aromatic spacers in 4c hinders such oxygen transfer reactions but may allow the characterization of stable dioxygen binding species. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A series of new oxygen-substituted, asymmetric zirconocene dichlorides (rac-{1-[5,6-(ethylenedioxy)-2-methyl-1-η5-indenyl]-2-(9-η5-fluorenyl)ethane}zirconium dichloride (3a), rac{1-[5,6-(ethylenedioxy)-2-methyl-1-η5-indenyl]-2-(9-η5-fluorenyl)ethane}dimethylzirconium (3b) and rac-{[5,6-ethylenedioxy)-2-methyl-1-η5-indenyl](9-η5-fluorenyl)dimethylsilane}zirconium dichloride (3c)} have been prepared and their polymerization behavior was investigated in dependence of monomer concentration, temperature and catalyst activation. The presence of oxygen substituents on the indenyl ring results in a strong increase of polymerization activities and also of polymer molecular weights with decreasing Al/Zr ratio. Significantly higher molecular masses and activities were found for the dimethyl complex 3b after activation with [(C6H5)3C+][(C6F5)4B−] deriving from the absence of chain transfer to aluminum and higher concentration of active catalyst species. The mechanism of stereoerror formation of the oxygen-containing C1-symmetric catalyst was investigated by deuterium labeling studies on propene monomers. The results are discussed on the basis of a reversible chain transfer to aluminum.

A series of tridentate P, N, P ligands comprising a central pyridine unit and two pendent diarylphosphane moieties (2, 6-bis(CH2PAr2)pyridine; Ar = phenyl (1), 2-methylphenyl (2), 2, 4, 6-trimethylphenyl (3)) as well as the corresponding iron (1-FeCl2, 2-FeCl2, 3-FeCl2) and cobalt (1-CoCl2, 2-CoCl2, 3-CoCl2) complexes were synthesized and characterized. An X-ray structure analysis of 2-CoCl2 and 3-CoCl2 exhibited a trigonal-bipyramidal coordination geometry at the metal center, the two chlorine atoms and the nitrogen occupying the equatorial and the phosphane units the apical positions. IR analysis indicated, that in all complexes the pyridine unit is coordinated to the metal center. The cobalt compounds were applied as catalyst precursors for the polymerization of ethene after activation with MAO. Eisen- und Cobaltkomplexe mit dreizahnigen P, N, P-Liganden — Synthese, Charakterisierung und Verwendung als Katalysatoren fur die Ethenpolymerisation Eine Reihe von dreizahnigen P, N, P-Liganden, bestehend aus einer 2, 6-diarylphosphansubstituierten Pyridineinheit (2, 6-bis(CH2PAr2)pyridin; Ar = phenyl (1), 2-methylphenyl (2), 2, 4, 6-trimethylphenyl (3)), wurde zu den entsprechenden Eisen(1-FeCl2, 2-FeCl2, 3-FeCl2) und Cobaltkomplexen (1-CoCl2, 2-CoCl2, 3-CoCl2) umgesetzt. Strukturanalysen an 2-CoCl2 und 3-CoCl2 zeigten in beiden Fallen eine trigonal-bipyramidale Koordinationsanordnung am Cobalt(II). Die Cobalt-Verbindungen wurden nach Aktivierung mit MAO als Katalysatoren fur die Polymerisation von Ethen eingesetzt.

A synthesis of new chiral dihalo palladium(II)-(5, 7) and nickel(II) (6, 8) complexes bearing the ligands N,N′-bis{(−)-(cis)-myrtanyl}butylene-2,3-diimine (BMDI, 3) and the conformationally constrained bisoxazoline ligand ((1R,2S)-inda-box, 4) is described. Reaction of [(TMEDA)Pd(CH3)Cl] (TMEDA: N,N,N′,N′-tetramethylethylenediamine) with 4 followed by chloride abstraction with NaB(Arf)4 in the presence of CH3CN afforded the solvent stabilized, monoalkyl complex [(4)Pd(NCCH3)(CH3)]B(Arf)4 (9) (Arf: 3,5-bis(trifluoromethyl)benzene). The solid state structure of the dichloro palladium(II) complex [{(1R,2S)-inda-box}PdCl2] (7) was determined by X-ray structure analysis.

Four new 1,4-diaza-2,3-dimethylbutadiene ligands (Ar−NC(CH3)−(H3C)CNAr; Ar: 3a = 2,6-diphenylphenyl; 3b = 2,6-di(4-OCH3-phenyl)phenyl; 3c = 2,6-di(4-tert-butyl-phenyl)phenyl; 3d = 2,6-di(3,5-dimethylphenyl)phenyl) as well as the palladium dichloride complexes 4a−c and methyl monochloride derivatives 5a−c were prepared, and their polymerization behavior was investigated. The corresponding nickel species 6a−c were tested for the insertion polymerization of ethene by in situ reactions of 3a−c with (DME)NiBr2. The ligands are accessible by a three-step procedure. Aryl boronic acids were prepared by Grignard reactions of substituted aryl bromides and were coupled with 2,6-dibromo aniline according to a Suzuki cross-coupling protocol to give the corresponding terphenyl anilines 2a−d. Condensation of 2,3-butanedione with the corresponding aniline afforded the formation of the diimines 3a−d. The corresponding palladium dichloride complexes 4a−c are accessible by reaction with (PhCN)2PdCl2. The structures of 4a−c...

Tertiary phosphines with pendant arenes R 2 PR' (R = Cy, Ph; R' = CH 2 CH 2 Ph or CH 2 CHPh 2 ) (1-4) were synthesized and converted to the corresponding chelating ruthenium(II) complexes [RuCl 2 (η 1 :η 6 -R 2 PR')] (la-4a). Halide exchange yielded [RuI 2 (η 1 :η 6 -R 2 PR')] (lb,3b), which were structurally characterized by single crystal X-ray diffraction. The systems (la,2a,4a) were activated for ROMP of norbornene by addition of a diazo compound (trimethylsilyldiazomethane) and AgBF 4 (A), by a diazo compound alone (B) or by a combination of the sodium salt NaB(Ar f ) 4 (Ar f = 3,5-(CF 3 ) 2 C 6 H 3 ) and methanol (C). The influence of the thereby created differing number of accessible coordination sites on the polymerization activity and the polymer microstructure (cis/trans ratio) was investigated. The nucleophilicity of the counter ion was found to play a crucial role in terms of catalytic activity.

The synthesis and characterization of the unsymmetric hafnium dialkyl [1-(η5-9-fluorenyl)-2-(η5-1-indenyl)ethane]HfCl2 (2) and corresponding dimethyl complex [1-(η5-9-fluorenyl)-2-(η5-1-indenyl)ethane]Hf(CH3)2 (3) is described. The dialkyl hafnocene (3) crystallizes in monoclinic space group P21/c (No. 14) with a = 9.458(8), b = 8.541(8), c = 23.733(11) A, β = 93.16(5) deg., V = 1914(3) A3, Z = 4. Further on, complex 3 was activated with methylaluminiumoxane (MAO) and utilized as a catalyst in ethene polymerization. Synthese und Kristallstruktur von [1-(η5-9-fluorenyl)-2-(η5-1-indenyl)ethan]hafniumdimethyl Die Synthese und Charakterisierung des asymmetrischen Hafniumdialkyls [1-(η5-9-fluorenyl)-2(η5-1-indenyl)ethan]HfCl2 (2) und des entsprechenden Dimethyl Komplexes [1-(η5-9-fluorenyl)-2-(η5-1-indenyl)ethan]Hf(CH3)2 (3) werden beschrieben. Dialkylhafnocen (3) kristallisiert in der monoklinen Raumgruppe P21/c (Nr. 14) mit a = 9.458(8), b = 8.541(8), c = 23.733(11) A, β = 93.16(5)°, V = 1914(3) A3, Z = 4. Komplex 3 wurde mit Methylaluminiumoxan (MAO) aktiviert und als Katalysator in der Ethenpolymerisation eingesetzt.

Palladium(II) complexes of the general type [Pd(L∩L)Cl2] (4–6) and their corresponding dicationic complexes [Pd(L∩L)(NCCH3)2](BF4)2 (7–9) (L∩L=[(1-(thiomethyl)-2-(diphenylarsino)ethane] (S∩As, 1) (4, 7) [1-(thiomethyl)-2-(diphenylphosphino)ethane] (S∩P, 2) (5, 8) and [1,2-bis(diphenylphosphino)ethane] (P∩P, 3) (6, 9) have been synthesized and utilized as catalysts for the polymerization reaction of bicyclo[2.2.1]hept-2-ene (norbornene). The dichloride complexes can be activated with methylaluminoxane (MAO), while the corresponding dicationic compounds were used as single component catalysts for the polymerization reactions. Catalytic performance of the new type of catalyst can be altered by modifying the donor atoms in the bidentate ligand. The activity of the Pd(II) complexes towards the polymerization reaction increases with increasing the trans-influence of the donor atoms (P∩P>S∩P>S∩As). The influence of donor atoms on the length of the PdCl bonds was elucidated by X-ray structure analysis carried out on the palladium(II) complex [Pd(S∩As)Cl2] (4).

Preparation of four dimeric nickel(II) complexes and three monomeric palladium(II) complexes bearing didentate pyridinylimine ligands is described. The solid-state structures of these compounds have been determined by single-crystal X-ray diffraction. After activation with methylaluminoxane (MAO) the nickel compounds were used as catalysts in ethylene polymerization producing nearly linear or primarily methyl-branched polymers. The effect of ligand environment was most evident on degree of branching, while catalytic activity and molecular weight of the polymer were more dependent on the general catalyst composition as well as reaction conditions. Activation of the dichloropalladium(II) complexes with MAO yields highly active catalysts for the polymerization of bicyclo[2.2.1]hept-2-ene (norbornene) whereas only low conversions (

Two mononuclear copper(II) complexes with the unsymmetrical tridentate ligand 2-[((imidazol-2-ylmethylidene)amino)ethyl]pyridine (HL), [Cu(HL)(H2O)](ClO4)2.2H2O (1) and [Cu(HL)Cl2] (2), have been prepared and characterized. The X-ray analysis of 2 revealed that the copper(II) ion assumes a pentacoordinated square pyramidal geometry with an N3Cl2 donor set. When 1 and 2 are treated with an equimolecular amount of potassium hydroxide, the deprotonation of the imidazole moiety promotes a self-assembled process, by coordination of the imidazolate nitrogen atom to a Cu(II) center of an adjacent unit, leading to the polynuclear complexes [[Cu(L)(H2O)](ClO4)]n (3) and [[Cu(L)Cl].2H2O]n (4). Variable-temperature magnetic data are well reproduced for one-dimensional infinite regular chain systems with J = -60.3 cm(-1) and g = 2.02 for 3 and J = -69.5 cm(-1) and g = 2.06, for 4. When 1 is used as a "ligand complex" for [M(hfac)2] (M = Cu(II), Ni(II), Mn(II), Zn(II)) in a basic medium, only the imidazolate-bridged trinuclear complexes [Cu(L)(hfac)M(hfac)2Cu(hfac)(L)] (M = Zn(II), Cu(II)) (5, 6) can be isolated. Nevertheless, the analogous complex containing Mn(II) as the central metal (7) can be prepared from the precursor [Cu(HL)Cl2] (2). All the trinuclear complexes are isostructural. The structures of 5 and 6 have been solved by X-ray crystallographic methods and consist of well-isolated molecules with Ci symmetry, the center of symmetry being located at the central metal. Thus, the copper(II) fragments are in trans positions, leading to a linear conformation. The magnetic susceptibility data (2-300 K), which reveal the occurrence of antiferromagnetic interactions between copper(II) ions and the central metal, were quantitatively analyzed for symmetrical three-spin systems to give the coupling parameters JCuCu = -37.2 and JCuMn = -3.7 cm(-1) with D = +/-0.4 cm(-1) for 6 and 7, respectively. These magnetic behaviors are compared with those for analogous systems and discussed on the basis of a localized-orbital model of exchange interactions.

The reaction of M(hfac)2 with the tridentate Schiff base H2L (where H2L stands for the 1:1 condensation product of 2-imidazolecarboxaldehyde with β-alanine) leads to the complexes [M(HL)(hfac)]n [M = MnII, NiII, and CuII; hfac = hexafluoroacetylacetonate anion] (1–3). The structures of the complexes 1 and 3 have been solved by X-ray crystallographic methods. The structures are very similar and consist of infinite zig-zag chains, running parallel to the b axis, in which the metal ions are bridged sequentially by anti-anti carboxylate groups with intrachain metal–metal distances of 6.134 A for 1 and 6.239 A for 3. Each monodeprotonated HL ligand acts as a tridentate one to a metal(II) ion and as a monodentate one to a neighbouring metal(II) centre. Metal atoms exhibit distorted octahedral coordination spheres comprised of two oxygen atoms from the hexafluoroacetylacetonate ligand, three donor atoms from the HL ligand and the oxygen atom belonging to the carboxylate group of an adjacent molecule. The complexes 1–3 have been confirmed to be isomorphous and isostructural on the basis of X-ray powder diffraction and IR spectra. The magnetic properties of the three compounds were studied by susceptibility measurements as a function of the temperature and successfully analyzed in terms of the isotropic spin Hamiltonian for one-dimensional infinite chain systems to give the coupling parameters J = –0.91 cm−1, g = 2.03 (1); J = –13.2 cm−1, g = 2.24 (2); and J = 0.40 cm−1, g = 2.11 (3). The magnetic behaviour for all three complexes can be satisfactorily explained in terms of the conformation of the bridge and the interaction between the d orbitals of the metal centre and the bridge.

The synthesis, molecular structure and magnetic properties of three new polynuclear copper(II) complexes, [Cu( cis -oxpn)Cu(bpm)]- (ClO 4 ) 2 ·CH 3 OH ( 1 ), [Cu 2 ( trans -oxpn) (bpm) 2 ](ClO 4 ) 2 ·2H 2 O ( 2 ) and [Cu 2 ( trans -oxpn)( μ -bpm)](ClO 4 ) 2 ·2.5H 2 O ( 3 ) are reported. The compounds were prepared by controlling the conformation ( cis or trans ) of oxpn ( N , N ′-bis(3-aminopropyl)oxamidate and the coordination mode (bi- or bisbidentate) of bpm (2,2′-bipyrimidine). Complex 1 is a dinuclear complex in which the copper(II) ions are bridged by a cis -oxamidate group and where bpm acts as a bidentate terminal ligand. 2 is a trans -oxamidate-bridged dinuclear copper(II) complex with two bidentate terminal bpm molecules. In 3, a bisbidentate bpm molecule connects the dinuclear Cu 2 ( trans -oxpn) units to generate an alternating oxamidate-bpm polynuclear copper(II) chain complex. Magnetic susceptibility measurements reveal the occurrence of strong antiferromagnetic exchange couplings for the three compouns with J values of −386.0 and −328.9 cm −1 for 1 and 2 , respectively, and J = −340.0 cm −1 , with an alternation parameter α = 0.24, for 3 . Magnetic parameters are discussed on the basis of the structural results and compared with those of related complexes.

Mononuclear copper(II) complexes with an unsymmetrical tridentate Schiff's base involving two imidazole moieties, [Cu(HL)(H2O)](ClO4)2 (1) and [Cu(L)(hfac)] (3), have been prepared and characterized, where HL stands for the 1:1 condensation product of 2-imidazolecarboxaldehyde and histamine. Under basic conditions, 1 easily undergoes a self-assembly process affording an insoluble imidazolate-bridged polymeric species {[Cu(L)(H2O)](ClO4)}n (2). By using 1 and 3 as “ligand complexes” toward M(hfac)2 (hfac = hexafluoroacetylacetonate) a series of imidazolate-bridged heterometal trinuclear complexes with the formula [Cu(L)(hfac)M(hfac)2Cu(hfac)(L)] (M = ZnII, CuII, NiII, MnII) (4−7) can be prepared. The structures of these complexes have been solved by X-ray crystallographic methods. All the trinuclear complexes are isostructural and consist of trinuclear molecules with a V-shaped conformation, which are formed by two CuL(hfac) “ligands” bonded through imidazolate bridges to the central metal in cis-position....

In this work titanium dichloro complexes bearing diethylmalonate, diethylphenylmalonate and diphenylmalonate ligands have been synthesized. The complexes were activated by methylaluminoxane (MAO) and exhibited moderate activity [10–50 kg PE /(mol Ti h bar)] in ethene polymerization. The catalysts produced ultra high molar mass polyethene (PE) (up to 3000 kg/mol) with polydispersity values range between 2 and 4.

Epoxystyrene (1a) were converted into their corresponding alcohols, 2a–c, by treatment with either fluorenyl- or indenyllithium. These alcohols were then further converted into their trifluoromethanesulfonate derivatives, 3a–c. Subsequent reaction of the triflates with fluorenyl-, indolyl-, or tetraphenylcyclopentadienyllithium resulted in formation of 2-(9-fluorenyl)-1(1-indenyl)-1-phenylethane (4a), and 1-(9-fluorenyl)-2-(5-tetraphenylcyclopentadienyl)ethane (4c). The ansa-metallocene (1-(R,S)-2(η5-9-fluorenyl)-1-[η5-1(R,S)-indenyl]-1-phenylethane]ZrCl2 (5a) was prepared from the dilithio salt of 4a. Hydrogenation of 5a with H2/PtO2 leads to {1(R,s)-cyclohexyl-2-(η5-octahydro-9-fluorenyl)-1-[η5-tetrahydro-1(R,S)-indenyl]ethane]ZrCl2 (6a. The complexes 5a and 6a were activated with methylalumoxane (MAO) and used for propene polymerization. The solid state structures of 4b, 4c, and 5a are reported.

The complexes [Cu(μ-L)Cu(bipy)(EtOH)](ClO4)2 2a and [Cu(μ-1L)Cu(bipy)(H2O)](ClO4)2·H2O 2b [where H2L = N,N′-bis(1,3-dimethyl-5-nitrosopyrimidine-2,4-(1H,3H)-dion-6-yl)propylenediamine; H21L arises from H2L by elimination of a CO molecule from one of the pyrimidine rings] have been obtained from the reaction of the precursor [Cu(μ-HL)Cu(H2O)2(CH3CH2OH)](ClO4)3 1 with bipy and Cu(ClO4)2 · 6H2O, respectively. The structures of 2a and 2b have been solved by X-ray crystallographic methods. The structure of 2a is made up of [Cu(μ-L)Cu(bipy)(EtOH)]2+ cations and two semi coordinated perchlorate anions. The [Cu(I)L] fragment coordinates to the external Cu(2) ion through the two deprotonated oximate oxygens to afford a dinuclear structure with double syn-syn nitroso-oximate bridge and an intramolecular CuCu distance of 3.731(1) A. The Cu(1) exhibits a CuN4O2 pseudoctahedral coordination polyhedron whereas the geometry around the Cu(2) ion is distorted square-pyramidal CuN2O2O. The structure of 2b consists of [Cu(μ-1L)Cu(bipy)(H2O)]2+ cations, two perchlorate anions and one lattice water molecule. The coordination of the [Cu(1L)] unit to the external Cu(2) ion takes place through the two nitroso-oximate groups, one of them disordered on two sets of crystallographic positions, one with a 63% occupancy and the other with a 37% occupancy. The intramolecular Cu(l)Cu(2) distance is 3.655(3) A. The Cu(l) occupying the inner site of the 1L2− ligand exhibits a 4+1 CuN4O (63%) [CuN3O2(37%)] coordination environment whereas the Cu(2) atom is in a distorted square-pyramidal CuN2O3(63%)[CuN3O2(37%)] environment. The dinuclear fragments of 2a and 2b are almost planar with dihedral angles between the mean basal coordination planes of 4.1(2)° and 4.6°, respectively. Both 2a and 2b are diamagnetic at room temperature, so that J < −1000 cm−1. The structural and magnetic data for these complexes have been compared with those of similar compounds, but no correlation between the magnitude of the exchange interaction and the degree of deviation from planarity is evident. In view of this and to rationalize the influence of the distortion from planarity on the magnetic properties in oximate-bridged complexes, MO Extended Huckel calculations have been performed.

The reaction of N,N′ -bis(1,3-dimethyl-5-nitroso-2,4-dioxopyrimidin-6-yl)butane-1,4-diamine (H 2 L 2 ) with copper(II) salts in ethanol yielded mononuclear complexes of formula [Cu(HL 2 )X] (X is the anion of the corresponding copper salt). These mononuclear precursors reacted with either Cu II and 2,2′-bipyridine (bipy) or [NiL][ClO 4 ] 2 (L = d,l -5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) to afford the homodinuclear complexes [Cu(µ-Cl)(µ-L 2 )Cu(bipy)]ClO 4 ·2H 2 O 1 and [LNi(µ-H 2 L 2 )NiL][ClO 4 ] 4 2, respectively. Within the dinuclear cation of 1 the copper(II) ions exhibit a 4 + 1 co-ordination environment. The dioxime ligand bridges the basal planes of the metal ions through the oximate groups in a symmetrical syn-syn fashion, Cu(1) · · · Cu(2) being 3.364(3) A, whereas their apical positions are occupied by a bridging Cl anion, with a Cu(1)–Cl(1)–Cu(2) angle of 80.42(7)°. A magnetic study of 1 revealed that the antiferromagnetic exchange is so strong as to cause complete spin pairing at room temperature. Complex 2 consists of a homodinuclear [LNi(µ-H 2 L 2 )NiL] 4+ cation and four non-co-ordinated perchlorate anions. The ligand adopts an unusual bis(didentate) open-chain co-ordination mode by elimination of the Cu atom occupying the inner site of the pseudo-macrocyclic ligand in the mononuclear precursor. This results in a Ni · · · Ni distance of 13.370(3) A. The nickel(II) ions are octahedrally co-ordinated by four nitrogen atoms belonging to the macrocyclic ligand L and the N and O atoms from the nitroso and the neighbouring exocyclic group. The co-ordination modes of H 2 L 2 are compared to those of the related N,N′ -bis(1,3-dimethyl-5-nitroso-2,4-dioxopyrimidin-6-yl)propane-1,3-diamine (H 2 L 1 ).

The synthetic route to obtain single crystals of dichloro­{6,6′-di-tert-butyl-2,2′-[1,2-ethanediylbis(nitrilomethylidyne-N)]- 4,4′-dimethyldiphenolato-O,O'}titanium(IV), is described. The X-ray analysis reveals that the title compound is a monomer with four molecules in the unit cell. There are only weak van der Waals-type forces between neighboring molecules. The compound crystallizes in the monoclinic space group P21/c (No. 14). The Ti atom has a distorted octahedral coordination with chloride ions in trans positions.

The lithium complex μ 9 -carbonato- O,O′,O′-μ 3 -chloro-tris( μ 3 -chloro- μ -hexamethylphosphoramide- O -hexamethylphosphoramide- O-μ 6 -tetramethylsiloxanediolato- O,O′ -tetralithium) bis-tetrahydrofuran,[[Li 4 (μ 3 -Cl(μ 6 -C 4 H 12 O 3 Si 2 )(μ-C 6 H 18 N 3 OP)(C 6 H 18 N 3 OP)] 3 (μ 3 -Cl)(μ 9 -CO 3 )]·2C 4 H 8 O, was formed in a reaction between dichlorodimethylsilane and dry ethanol followed by reaction with Bu n Li, HMPA (hexamethylphosphoramide) and TiCl 4 . The structure consists of three Li 4 O 3 Cl cubanes which are linked together by a central chloride and carbonate ion. In addition, three tetramethyl siloxanediolato and HMPA bridges join the cubanes externally. The remaining three HMPA molecules are monocoordinated to the lithium atoms. The crystal also contains two tetrahydrofuran solvent molecules.

Reported here are useful strategies recently developed for the large-scale synthesis of complex and polyfunctional molecules using native or engineered enzymes as catalysts. Several important issues in the field regarding the problems of substrate specificity, product inhibition, reaction reversibility, enzyme stability and catalytic efficiency are addressed in the representative synthesis of carbohydrates and carbohydrate mimetics designed for use to study carbohydrate-mediated cell adhesion.

Lipoxygenases catalyze dioxygenation of polyunsaturated fatty acids to produce fatty-acid hydroperoxides. The reaction involves initial stereospecific abstraction of a hydrogen atom from a bis-allylic methylene group followed by antarafacial attack by dioxygen at one of the terminal carbon atoms of the pentadienyl radical. 8(R)-Dioxygenase, recently discovered in the fungus Gaeumannomyces graminis, catalyzes formation of 8-hydroperoxy derivatives of linoleic and oleic acids by abstracting one hydrogen from C-8 and inserting dioxygen at the same carbon atom. Isotope-labeling studies show that the configuration at C-8 is inverted during this process. The fungus Saprolegnia parasitica, a fish parasite, contains an omega 6-lipoxygenase and an epoxy alcohol synthase. The latter enzyme catalyzes isomerization of fatty acid hydroperoxides into alpha,beta- and gamma,delta-epoxy alcohols. Experiments with 18O-labelled hydroperoxides demonstrate that the hydroperoxide --> epoxy alcohol conversion consists of intramolecular transfer of the terminal hydroperoxide oxygen to either of the two conjugated double bonds. The reactions proceed with retention of geometrical configuration, i.e. epoxidation of the alpha,beta (E) and gamma,delta (Z) double bonds of the parent fatty acid hydroperoxide gives rise to trans and cis epoxides, respectively. G. graminis, as well as the marine red alga Gracilariopsis lemaneiformis, contain vicinal diol synthases that catalyze isomerization of fatty-acid hydroperoxides into vicinal dihydroxy fatty acids. Studies using 18O-labelled hydroperoxides show that the hydroperoxide --> diol conversions occur by intramolecular transfer of the terminal hydroperoxide oxygen to the vicinal methylene group. Experiments with stereospecifically deuteriated fatty-acid hydroperoxides demonstrate that the intramolecular hydroxylations catalyzed by the two vicinal diol synthases proceed with retention of absolute configuration of the carbon hydroxylated.

The crystal structure of [Cu(ClO4)(μ-L)Ni(CTH)](ClO4)·H2O (where H2L is α,ω-bis(1,3-dimethyl-5-nitrosouracil-6-yl-amine)propane and CTH is d,l-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been determined by X-ray methods. The complex crystallizes in the monoclinic space group C2/c with a=41.848(16), b=12.738(3), c=20.005(7) A, β=114.92(2)°. The structure consists of discrete dimetallic cations [Cu(ClO4)(μ-L)Ni(CTH)]+, one perchlorate anion and one non-bonded disordered molecule of water. Within the dinuclear cation, copper(II) and nickel(II) are bibridged by an exocyclic oxygen atom of the uracil ring and an anti nitroso-oximato group, resulting in a Cu···Ni distance of 4.972(2) A. The copper(II) ion occupying the inside site of the double deprotonated ligand L2− exhibits a N4O distorted square-pyramidal coordination environment, whereas the nickel(II) ion is in a distorted octahedral geometry. Magnetic susceptibility measurements in the temperature range 300-2 K revealed the occurrence of a strong antiferromagnetic exchange interaction between copper(II) and nickel(II) ions with a J value of −136.4 cm−1. Magnetic and structural parameters of this and other related complexes are compared in order to know how the type of NO bridging conformation affects the magnetic properties.

Li(2,6- t Bu 2 -OC 6 H 3 )(DMSO)} 2 was formed by the reaction of n -butyl lithium with 2,6-di- tert -butylphenol followed by recrystallization from toluene-DMSO solution. The single crystal X-ray diffraction data were collected at °C. The structural analysis showed that this phenoxide is a dimer and lithium metal is 3-coordinated. A special feature in this structure is the short OAr (ArC 6 H 3 -2,6- t Bu 2 ) bond length [1.315(13) A] which is the shortest distance found in dimeric lithium phenoxides.

The reaction of H2L [H2L =N,N′-bis(1,3-dimethyl-5-nitrosopyrimidine-2,4(1H,3H)-dion-6-yl)propylenediamine] with an excess of Cu(ClO4)2·6H2O in ethanol gave the dinuclear complex [Cu(µ-HL)-Cu(H2O)2(EtOH)][ClO4]31, magnetic studies of which revealed that the antiferromagnetic exchange interaction mediated by the oximate groups is so strong that it causes a complete spin coupling at room temperature. This compound reacted with NaCl in ethanol–water (5:1) to afford the mixed-bridged trinuclear copper(II) complex [{Cu(µ-HL)Cu(H2O)Cu(µ-L)}(µ-Cl)][ClO4]2·4.88H2O 2 the crystal structure of which was solved by single-crystal X-ray diffraction. Compound 2 consists of discrete trinuclear cations [{Cu(µ-HL)Cu(H2O)Cu(µ-L)}(µ-Cl)]2+, non-co-ordinated perchlorate anions and lattice water molecules. Within the trinuclear cation, which has C2v symmetry the three copper ions are arranged at the corners of an isosceles triangle. Each terminal copper atom Cu(2) and the central copper atom Cu(1) are bibridged by syn,syn oximate groups with a Cu(1)⋯ Cu(2) distance of 3.373(4)A, whereas a chloride anion bridges the two terminal copper atoms with a Cu(2)⋯ Cu(2) distance of 4.770(4)A. The angles Cu(2)–Cu(1)–Cu(2) and Cu(2)–Cl(1)–Cu(2) are 90.0(1) and 144.4(4)°, respectively. The central Cu(1) exhibits a square pyramidal CuO5 co-ordination environment with four oxygen atoms of oximate groups in the basal plane and the water oxygen at the apical site. The terminal Cu(2) atoms occupy the N4 inner site of the ligand with the chloride bridging anion occupying the axial position of the square pyramidal CuN4Cl co-ordination environment. From magnetic susceptibility measurements, complex 2 was found to exhibit a very strong antiferromagnetic exchange interaction through the oximate bridges (J=–189 cm–1), leading to complete spin coupling at 120 K. Magnetic parameters are discussed on the basis of the structural results and compared with those of other related complexes.

The structure of the title compound, C 17 H 15 N 3 , consists of two independant molecules which are connected by nearly linear weak N(amino)-H...N(pyridine) hydrogen bonds through a pseudo center of inversion to form a dimer. Conformationally, this symmetrically substituted pyridine derivative displays an E,E form. In this form the H-atom interactions between neighboring rings are reduced