Hydrozirconierung von nitrilen: Die bildung ein- und zweikerniger (alkylidenamido)zirconocen-komplexe

Cp₂Zr(-N=CHR)Cl compounds (9a–9c: R = CH₃, C₆H₅, CH₂Ph,respectively) are formed upon hydrozirconation of nitriles. Subsequent reaction with an aryllithium reagent yields Cp₂Zr(-N=CHR)Ar (14). The (alkylidene amido)zirconocene complexes are characterized by a linear heteroallene-type structure possessing an sp-hybridized nitrogen atom. 9 reacts with the oligomeric metallocene dihydrides (Cp₂ZrH₂)_x (15) and (Cp₂HfH₂)_c, (17), respectively, to form the binuclear compounds Cp₂Zr(μ-N=CHR)(μ-Cl)MC_p2 (16, M = Zr) and (18, M = Hf). The formation of these thermally very stable metal complexes is discussed.     

Reaktionen von (η-formaldehyd)zirconocen-dimer mit heterokumulenen

The (η²-formaldehyde)zirconocene dimer (Cp₂ H₂)₂ (7) inserts CO₂ into the zirconium to carbon bond of the metallaoxirane moiety to give [(Cp₂ H₂)(Cp₂ =O)] (8). Reaction with diphenylketene 7 gives the cyclodimeric 1 : 1 addition product (Cp₂ =CPh₂)₂ (10) via the mono-insertion product 9. Similarly, treatment of 7 with t-butylisocyanate yields the intermediate complex [(Cp₂ H₂)(Cp₂ =NCMe₃)] (11) which gives the final product (Cp₂ =NCMe₃)₂ (12). Here two five-membered metallacycles are joined together by oxygen bridges via a central four-membered Zr₂O₂ metallacycle. Complex 12 was characterized by X-ray diffraction. It crystallizes in space group P2₁/n with cell parameters a 10.142(1), b 17.949(2), c 12.001(1) Å, β = 114.27(1)°; Z = 2, R = 0.055, R_w = 0.054.     

三价锆有机化合物的ESR谱研究

利用Cp₂ZrHCl、(Cp₂ZrCl)₂、Cp₂ZrH(μ-H)与不含活泼氢的氮、膦类配体作用,可得到一系列热稳定的三价锆配合物,对其进行了ESR谱研究,其中17种配合物的波谱参数为首次报道。     

Carbonylation of 2-bornenyl(methyl)zirconocene

The reaction of methylzirconocenechloride with 2-bornenyllithium yields (2-bornenyl)methylzirconocene (10a). Carbonylation of 10a takes place exclusively by CO-insertion into the Zr-C(sp²) bond to give Cp₂ZrMe(η²-OC-C₁₀H₁₅) (16a). The corresponding hafnium complex 10b reacts analogously to give 16b. Complex 16a was characterized by X-ray diffraction, and found to contain an η²-acyl ligand bonded to zirconium in the thermodynamically favored “O-inside” arrangement with the following bonding parameters: d Zr-C(acyl) = 2.192(7) Å, d Zr-O(acyl) = 2.258(6) Å, d C=O = 1.246(9) Å, angles O(acyl)---Zr---C(acyl) = 32.5(2)°, Zr---C(acyl)---O(acyl) = 76.7(4)°.     

Reactions of naphthaleneytterbium with bis(cyclopentadienyl)complexes of cobalt, nickel, chromium and vanadium. X-Ray crystal structure of the triple-decker CpVC10H8VCp

Naphthaleneytterbium, C₁₀H₈Yb(THF)₃, reacts with Cp₂Cr, Cp₂Co, Cp₂Ni, and Cp₂V in THF to give Cp₂Yb. In the case of the reaction of C₁₀H₈Yb(THF)₃ with Cp₂V, vanadium-containing intermediates could be isolated. One of them, CpVC₁₀H₈VCp, has been characterized by X-ray diffraction. The crystals are monoclinic, space group P2₁/n, with a 907.0(5), b 798.8(3), c 1080.8(5) pm, β 105.21(4)°; Z = 2. The structure was refined to R = 0.0288 for 1131 observed reflections (F_o > 4σ(F_o)).     

Monomeric, dimeric and polymeric [Cp2MoH2] complexes with Ag---S bonds

The reaction of [Cp₂MoH₂] and AgBF₄ with the dithio ligands Na(S₂CPh) and K(S₂COⁱPr) afforded the complexes [(Cp₂MoH₂AgS₂CPh)₂] (1) and [(Cp₂MoH₂AgS₂COⁱPr)₂] (2). Using the monothio ligands Na(SC(O)Ph), K(SC(O)CH₃) and Na(S(NHPh)C=C(CN)₂) the complexes [(Cp₂MoH₂AgSC(O)Ph)₂] (3), [((Cp₂MoH₂)₂(AgSC(O)CH₃)₃)_n] (4) and [(Cp₂MoH₂)₂AgS(NHPh)C=C(CN)₂] (6) were formed. The reaction of thiobenzamide and [(Cp₂MoH₂)₂AgCl] gave the complex [(Cp₂MoH₂Ag(Cl)S(NH₂)CPh)₂] (5). Complexes 1 and 2 have a dimeric structure with the two dithio ligands bridging the two silver atoms. Complex 3 is also a dimer, however, the monothio ligands are coordinated with their single sulphur atoms to the silver atoms. In the polymer 4 the thioacetate ligand has the same bonding mode as in 3. The three-dimensional structure of 4 is built-up of parallel strings. In the dimer 5 the thiobenzamide ligands bind with the sulphur atom to a silver atom each. Complex 6 has a monomeric structure in which the silver atom is coordinated to two [Cp₂MoH₂] ligands and to the sulphur atom of the S(NHPh)C=C(CN)₂ ligand. Compounds 1–6 were characterised analytically and spectroscopically and the structures were determined by single crystal X-ray analyses.     

Chiroptische effekte von lanthanoidorganylen mit optisch aktiven liganden III. Erschließung wohldefinierter chiraler organosamarium(III)-verbindungen durch umsetzung von tris(cyclopentadienyl)samarium mit (1S,2R,5R)-Isomenthol, (R)-(+)-Isobutyllactat und (R)-(+)-Methyl-p-tolylsulfoxid

While each of the three organosamarium(III) title complexes: [Cp₂Sm{μ-OC₁₀H₁₉}]₂ (5; Cp = C₅H₅, OC₁₀H₁₉ = isomenthoxide), [Cp₂Sm{μ-OCH(Me)COOⁱBU}]₂ (6) and [Cp₃SmOS(Me)-p-C₆H₄Me] (7) contains a chiral ligand atom (i.e. C or S) next to the metal-bonded oxygen atoms, only the dinuclear compounds 5 and, even better, 6 display (below ca. 600 nm) significant circular dichroism of discrete f---f-crystal field transitions. According to a successful single-crystal X-ray study of 5, the cyclohexyl ring of its (1S,2R,5R)-isomenthoxide ligand adopts a conformation with axial OSm- and ⁱPr-substituents, which is energetically less favourable at least for neat (1S,2R,5R)-isomenthol.

Zusammenfassung

Obwohl jeder der drei neuen Organosamarium(III)-Komplexe: [Cp₂Sm{μ-OC₁₀OH₁₉}]₂ (5; Cp = C₅H₅, OC₁₀H₁₉ = Isomentholat), [Cp₂Sm{μ-OCH(Me)COOⁱBU}]₂ (6) und [Cp₃SmOS(Me)-p-C₆H₄Me] mindestens ein chirales Ligandenatom (C oder S) unmittelbar am metallkoordinierten O-Atom enthält, zeigen nur die dimeren Systeme 5 und noch ausgeprägter 6 (unterhalb von ca. 600 nm) signifikanten Circulardichroismus von f---f-Kristallfeldübergängen des Sm³⁺-Ions. Auf Grund einer erfolgreichen Kristallstrukturanalyse von 5 liegt der Cyclohexylring des (1S,2R,5R)-Isomentholatliganden ausschließlich in der Konformation mit axialen OSm- und ⁱPr-Substituenten vor, die für freies (1S,2R,5R)-Isomenthol energetisch deutlich unvorteilhafter ist.     

The preparation and catalytic applications of supported zirconocene and hafnocene complexes

Polymer-attached Cp₂ZrCl₂, Cp₂HfCl₂, CpZrCl₃, CpHfCl₃, Cp₂ZrCl and Cp₃HfCl have been prepared. The polymer-attached Cp₂ZrCl₂, on reduction with BuLi, produced an active catalyst whose efficiency for olefin hydrogenation is about eight times as great as that of the corresponding homogeneous species under the same conditions. The reduction products of supported zirconocene and hafnocene complexes are active hydrogenation catalysts for diphenylacetylene which was hydrogenated to 1,2-diphenylethane through intermediate stilbene. The similar reduction products have also been employed in catalytic isomerization of allylbenzene, cis-stilbene and 1,5-cyclooctadiene. Allylbenzene was converted into a mixture of trans- and cis-propenylbenzene, cis-stilbene was isomerized to trans-stilbene, and 1,5-cyclooctadiene was isomerized to 1,3-cyclooctadiene through the 1,4-cyclooctadiene intermediate. Polymer-attached Cp₂ZrCl₂, CpZrCl₃, Cp₂HfCl₂, and CpHfCl₃ can be used directly, without going through the reduction process, for the low yield epoxidation of cyclohexene. Polymer-attached Cp₂ZrCl₂ was used in hydrozirconation and carbon monoxide reduction studies.     

Reaktion eines titanocen—Alkin-Komplexes mit trialkylammoniumtetraphenylborat—eine neue darstellungsweise und erste kristallstrukturanalyse von neutralligandhaltigen kationischen titanocen(III-komplexen [{Cp2Ti(L)2}{BPh4}]

The catioanic d¹-titanocene complexes [{Cp₂Ti(L)₂⁺}{BPh₄⁻}] with L = THF (1) and pyridine (2) were very simply prepared by the reaction of [Cp₂Ti(Me₃SiCCSiMe₃)] with trimethylammoniumtetraphenylborate via a le⁻-oxidation of the 14e⁻-Cp₂Ti-unit to the paramagnetic titanium(III) complex under evolution of molecular hydrogen and the alkyne. Complex 2 is the first example of such a cationic-only neutral-ligand containing complexes without anionic ligands that has been characterized by an X-ray structure analysis.     

Synthese und konformationsstudien von selen-analoga der metallocen-dithiolen-chelate früher übergangsmetalle

The reaction of the metallocene dichlorides Cp₂MCl₂ (Cp = η⁵-C₅H₅; M = Ti, Zr, Hf, Mo, W) and Cp₂′TiCl₂ (Cp′ = η⁵-C₅H₄CH₃) with equimolar amounts of dilithium-benzene-o-diselenolate, 1,2-(LiSe)₂C₆H₄, gives the chelate complexes Cp₂M(Se₂C₆H₄) (M = Ti (I), Zr (II), Hf (III), Mo (IV), W (V)) and Cp₂′Ti(Se₂C₆H₄) (VI). CpTiCl₃ reacts with 1,2-(LiSe)₂C₆H₄ to give CpTiCl(Se₂C₆H₄) (VII). The ring inversion activation parameters for I–VI can be determined by means of temperature-dependent ¹H NMR spectroscopy in solution. The fragmentation behaviour of I–VII in the mass spectrometer has been investigated by pursuing metastable transitions, using linked-scan techniques.     

Acetylen-Komplexe von Di(η-cyclopentadienyl)molybdän: Synthesen und Protonierung. Struktur von [Cp2MoH{η-C2(SiMe3)2}]PF6

Cp₂MoH₂ reacts with methyl acrylate in the presence of acetylenes (L = C₂H₂, C₂Me₂, HCC^tBu, HCCSiMe₃, C₂(SiMe₃)₂, HCCCH₂OMe, HCCCH₂NMe₂) to form acetylene complexes Cp₂Mo(L) 5. Protonation takes place with CF₃CO₂H at −80°C to give short-lived cations [Cp₂MoH(L)⁺ (8) (L = C₂Me₂, HCCSiMe₃, C₂(SiMe₃)₂). The structure of [Cp₂MoH{η²-C₂(SiMe₃)₂}]PF₆(9) was determined by an X-ray diffraction study.     

Zr-TUD-1: A novel heterogeneous catalyst for the Meerwein–Ponndorf–Verley reaction

A series of Schiff-base complexes has been synthesized by the condensation of 1,2-diaminocyclohexane with salicylaldehyde, 2-pyridinecarboxaldehyde, and 2-hydroxy-1-naphthaldehyde, followed by the metallation with manganese (1, 2, 3a), cobalt (3b), copper (3c) and iron (3d) salts. These Schiff-base ligands L₁–L₃ and complexes 1, 2, 3a–d were then characterized by IR, ¹H NMR, ¹³C NMR, UV–vis spectra, and DSC measurement. Schiff-base Mn complex (3a) resulting from N,N′-bis(2-hydroxy-1-naphthalidene)cyclohexanediamine (L₃) ligand was considerably active for the catalytic epoxidation of styrene under mild conditions, in which the highest yield of styrene oxide reached 91.2 mol%, notably higher than those achieved from simple salt catalysts Mn(Ac)₂·4H₂O and MnSO₄·H₂O. However, another two salen–Mn complexes 1 and 2 derived from ligands N,N′-bis(salicylidene)cyclohexanediamine (L₁) and N,N′-bis(2-pyridine carboxalidene)cyclohexanediamine (L₂) exhibited relatively poor activity under identical experimental conditions.     

Synthesis and characterisation of [(C5Me4R)2NbS2]2M complexes (M = Fe, Co; R = Me, Et) : organometallic tetrathiometalates with niobocene ligands

Irradiation of Cp₂^* Nb(η²---S₂)H (Cp^* = C₅Me₅) 1a in the presence of Fe(CO)₅ gives the CO-free complex [Cp₂^*NbS₂]₂Fe 2a. The core of 2a contains an FeS₄ tetrahedron which is ligated by two niobocene ligands as shown by X-ray diffraction analysis. In the reaction of 1a or Cp₂^xNb(η²---S₂)H (CP^x = C₅Me₄Et) 1b with Co₂(CO)₈, compounds 3a and 3b of the same type are formed. Electrochemical studies of 2a and 3a,b show that they undergo three reversible 1e⁻ steps. The oxidation of 3b exerts a considerable influence on its absorption spectrum. A qualitative EHMO analysis is in agreement with a strong delocalisation of electron density over the whole NbS₂MS₂Nb system.     

Iron carbonyl complexes from 2-[2,3-diaza-4-(2-thienyl)buta-1,3-dienyl]thiophene: N---N bond cleavage and cyclometalation

When thienyl Schiff base 1, derived from 2-formylthiophene and hydrazine, reacted with Fe₂(CO)₉ in n-hexane, three major complexes were obtained: (1) a diironhexacarbonyl complex with two 2-thienylmethylideneamido bridging ligands 2, which resulted from the =N---N= bond cleavage of ligand 1; (2) a doubly cyclometalated di-μ-di-(η¹:η²-thienyl; η¹:η¹(N))bis(hexacarbonyldiiron) complex (3); and (3) a cyclometalated (μ-η¹:η²-thienyl; η¹:η¹(N))hexacarbonyldiiron complex (4). Molecular structures of compounds 1a, 1c, and 2a have been determined by single-crystal X-ray diffraction.     

二环戊二烯基钛烴氧基衍生物的合成和性能研究

二环戊二烯基二氯化钛与脂肪醇的反应是非常复杂的,由于反应体系不同,所得的产物也不同,且产物又不稳定^[1-3]。     

Supramolecular architecture of cadmium(II)–terephthalate complexes having a tridentate or tetradentate Schiff base as blocking coligand

Two new cadmium(II)–terephthalate complexes, _∞¹{[Cd₂(μ-terephthalate)₂(L¹)₂]·9H₂O} (1) and [{Cd(H₂O)(L²)}₂(μ-terephthalate)](terephthalate) · 10H₂O (2), where L¹ = (E)-N¹,N¹-diethyl-N²-(1-(pyridin-2-yl)ethylidene)ethane-1,2-diamine; L² = N,N′-bis-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine; have been synthesized by a conventional solution method. Characterization by single crystal X-ray crystallography shows that compound 1 is composed of 1-D polymeric zig-zag chains with distorted pentagonal-bipyramidal cadmium centers. Compound 2 consists of centrosymmetric dinuclear complexes with a distorted pentagonal-bipyramidal cadmium center in which one terephthalate ligand bridges the metal centres and another terephthalate anion with water of crystallization forms a H-bonding network.     

Bis(2-bromoethyl) selenium dibromide as the selenium-introducing reagent: One-pot preparation of 2,5-bis(alkoxymethyl)tetrahydroselenophenes by the cyclization of 1,5-hexadiene

The reaction of bis(2-bromoethyl)selenium dibromide (1a) with 1,5-hexadiene (2) in methanol or ethanol affords 2,5-bis(alkoxymethyl)tetrahydroselenophene-1,1-dibromides (R = CH₃ (3b), R = C₂H₅ (3c)) via 2,5-bis(bromomethyl)tetrahydroselenophene-1,1-dibromide (3a). The reaction of 1a with 2 in 1-propanol, 2-methyl-1-propanol or 1-butanol in the presence of sodium carbonate gave 2,5-bis(alkoxymethyl)tetrahydroselenophene (R = C₃H₇ (4a), R = (CH₃)₂CHCH₂ (4b) and R = C₄H₉ (4c)) via 3a. The ratios of the trans and cis isomers of 3a–3c are 3:2. In addition, the structure of trans-2,5-bis(methoxymethyl)tetrahydroselenophene-1,1-dibromide (trans-3b) was determined by X-ray crystallography.     

Cyano-bridged bimetallic complexes of copper(II) with tetracyanonickelate(II). Crystal structure of [Cu(dpt)Ni(CN)4]

Five new complexes of composition [Cu(dpt)Ni(CN)₄] (1) (dpt=dipropylenetriamine), [Cu(dien)Ni(CN)₄]·2H₂O (2) (dien=diethylenetriamine), [Cu(N,N′-dimeen)Ni(CN)₄]·H₂O (3) (N,N′-dimeen=N,N′-dimethylethylenediamine), [Cu(N,N-dimeen)Ni(CN)₄]·H₂O (4) (N,N-dimeen=N,N-dimethylethylenediamine) and [Cu(trimeen)Ni(CN)₄] (5) (trimeen=N,N,N′-trimethylethylenediamine) have been obtained by the reactions of the mixture of Cu(ClO₄)₂·6H₂O, appropriate amine and K₂[Ni(CN)₄] in water and have been characterized by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dpt)Ni(CN)₄] (1) has been determined by single-crystal X-ray analysis. The structure of 1 consists of a one-dimensional polymeric chain ---Cu(dpt)---NC---Ni(CN)₂---CN---Cu(dpt)--- in which the Cu(II) and Ni(II) atoms are linked by CN groups. The nickel atom is four coordinate with four cyanide-carbon atoms (two cyano groups are terminal and two cyano groups (in cis fashion) are bridged) in a square-planar arrangement and the copper atom is five coordinate with two cyanide-nitrogen and three dpt-nitrogen atoms, in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibility (2–300 K) was measured for compound 1. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (J=−0.16 cm⁻¹) between the copper atoms within each chain through the diamagnetic Ni(CN)₄ ²⁻ ions.     

Ethylene oligomerization by diimine iron(II) complexes/EAO

The catalytic properties of a series of Fe(II) diimine complexes (diimine=N,N′-o-phenylenebis(salicylideneaminato), N,N′-ethylenebis(salicylideneaminato), N,N′-o-phenylenebisbenzal, N,N′-ethylenebisbenzal) in combination with ethylaluminoxane (EAO) for ethylene oligomerization have been investigated. Treatment of the iron(II) complexes with EAO in toluene generates active catalytic systems in situ that oligomerize ethylene to low-carbon olefins. The effects of reaction temperature, ratios of Al/Fe and reaction periods on catalytic activity and product distribution have been studied. The activity of complex FeCl₂(PhCH=o-NC₆H₄N=CHPh) with EAO at 200°C is 1.35×10⁵ g oligomers/mol Fe·h, and the selectivity of C_4–10 olefins is 84.8%.     

Addition of a Reformatsky reagent to N-anthracene-9-sulfonyl and related imines: Synthesis of protected β-amino acids

The Reformatsky reagent tert-butoxycarbonylmethylzinc bromide adds in high yields to N-sulfonylimines, e.g. 1a–1d, derived by condensation of benzaldehyde dimethyl acetal with methanesulfonamide, toluene-4-sulfonamide, 4-(methoxycarbonyl)benzenesulfonamide and sulfamide: the products are protected β-amino acids 2a–2d. N-Deprotection occurs reductively (Na-naphthalene; low yields) for 2b and 2c or hydrolytically (refluxing aq. pyridine; 76% yield of amino acid 3a after acid hydrolysis of the t-butyl ester) for the sulfamide derivatives 2d. Anthracene-9-sulfonamide (6) is readily available by sulfonation and chlorination of anthracene, and condenses with aldehydes [RCHO; R = Ph, 4-FC₆H₄, 4-MeOC₆H₄, 4-NCC₆H₄, 2-furyl, (E)-styryl], e.g. in the presence of TiCl₄/Et₃N, to yield imines 7a–7f, which after addition of tert-butoxycarbonylmethylzinc bromide give protected amino acids 8a–8f; however, 8f cyclizes to the sultam 9 via a spontaneous intramolecular Diels-Alder reaction. Reductive cleavage of the N-anthracene-9-sulfonyl group is much easier than for traditional N-sulfonyl protecting groups, as demonstrated by the deprotection of 8a and 8c using aluminium amalgam.