Y,Lu, and Gd Complexes of NCO/NCS Pincer Ligands: Synthesis,Characterization, and Catalysis in the cis‐1,4‐Selective Polymerization of Isoprene

A series of NCO/NCS pincer precursors, 3‐(Ar²OCH₂)‐2‐Br‐(Ar¹N?CH)C₆H₃ ((^Ar1NCO^Ar2)Br, 3a , 3b , 3c , 3d ) and 3‐(2,6‐Me₂C₆H₃SCH₂)‐2‐Br‐(Ar¹N?CH)C₆H₃ ((^Ar1NCS^Me)Br, 4a and 4b ) were synthesized and characterized. The reactions of [^Ar1NCO^Ar2]Br/ [^Ar1NCS^Me]Br with nBuLi and the subsequent addition of the rare‐earth‐metal chlorides afforded their corresponding rare‐earth‐metal–pincer complexes, that is, [(^Ar1NCO^Ar2)YCl₂(thf)₂] ( 5a , 5b , 5c , 5d ), [(^Ar1NCO^Ar2)LuCl₂(thf)₂] ( 6a , 6d ), [(^Ar1NCO^Ar2)GdCl₂(thf)₂] ( 7 ), [{(^Ar1NCS^Me)Y(μ‐Cl)}₂{(μ‐Cl)Li(thf)₂(μ‐Cl)}₂] ( 8 , 9 ), and [{(^Ar1NCS^Me)Gd(μ‐Cl)}₂{(μ‐Cl)Li(thf)₂(μ‐Cl)}₂] ( 10 , 11 ). These diamagnetic complexes were characterized by ¹H and ¹³C NMR spectroscopy and the molecular structures of compounds 5a , 6a , 7 , and 10 were well‐established by X‐ray diffraction analysis. In compounds 5a , 6a , and 7 , all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two Cl? Li? Cl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the polymerization of isoprene, thereby affording highly cis‐1,4‐selective polyisoprene, whilst the NCO? lutetium complexes were inert under the same conditions.     

Synthese,Struktur und Reaktivität von Tris‐, Bis‐ und Mono(2,4‐dimethylpentadienyl)‐Komplexen des Neodyms,Lanthans und des Yttriums

The tris(2,4‐dimethylpentadienyl) complexes [Ln(η⁵‐Me₂C₅H₅)₃] (Ln = Nd, La, Y) are obtained analytically pure by reaction of the tribromides LnBr₃·nTHF with the potassium compound K(Me₂C₅H₅)(thf)_n in THF in good yields. The structural characterization is carried out by X‐ray crystal structure analysis and NMR‐spectroscopically. The tris complexes can be transformed into the dimeric bis(2,4‐dimethylpentadienyl) complexes [Ln₂(η⁵‐Me₂C₅H₅)₄X₂] (Ln, X: Nd, Cl, Br, I; La, Br, I; Y, Br) by reaction with the trihalides THF solvates in the molar ratio 2:1 in toluene. Structure and bonding conditions are determined for selected compounds by X‐ray crystal structure analysis and NMR‐spectroscopically in general. The dimer‐monomer equilibrium existing in solution was investigated NMR‐spectroscopically in dependence of the donor strength of the solvent and could be established also by preparation of the corresponding monomer neutral ligand complexes [Ln(η⁵‐Me₂C₅H₅)₂X(L)] (Ln, X, L: Nd, Br, py; La, Cl, thf; Br, py; Y, Br, thf). Finally the possibilities for preparation of mono(2,4‐dimethylpentadienyl)lanthanoid(III)‐dibromid complexes are shown and the hexameric structure of the lanthanum complex [La₆(η⁵‐Me₂C₅H₅)₆Br₁₂(thf)₄] is proved by X‐ray crystal structure analysis.     

Organo‐Palladium(II)‐Verbindungen mit PdC4‐Koordination: Phenylethinyl‐ und Methylphenylethinylkomplexe

Tetrakis(p‐tolyl)oxalamidinato‐bis[acetylacetonatopalladium(II)] ([Pd₂(acac)₂(oxam)]) reacted with Li–C≡C–C₆H₅ in THF with formation of [Pd(C≡C–C₆H₅)₄Li₂(thf)₄] ( 1a ). Reaction of [Pd₂(acac)₂(oxam)] with a mixture of 6 equiv. Li–C≡C–C₆H₅ and 2 equiv. LiCH₃ resulted in the formation of [Pd(CH₃)(C≡C–C₆H₅)₃Li₂(thf)₄] ( 2 ), and the dimeric complex [Pd₂(CH₃)₄(C≡C–C₆H₅)₄Li₄(thf)₆] ( 3 ) was isolated upon reaction of [Pd₂(acac)₂(oxam)] with a mixture of 4 equiv. Li–C≡C–C₆H₅ and 4 equiv. LiCH₃. 1 – 3 are extremely reactive compounds, which were isolated as white needles in good yields (60–90%). They were fully characterized by IR, ¹H‐, ¹³C‐, ⁷Li‐NMR spectroscopy, and by X‐ray crystallography of single crystals. In these compounds Li ions are bonded to the two carbon atoms of the alkinyl ligand. 1a reacted with Pd(PPh₃)₄ in the presence of oxygen to form the already known complexes trans‐[Pd(C≡C–C₆H₅)₂(PPh₃)₂] and [Pd(η²‐O₂)(PPh₃)₂]. In addition, 1a is an active catalyst for the Heck coupling reaction, but less active in the catalytic Sonogashira reaction.     

Heterobimetallische Komplexe von Lithium,Aluminium und Gold mit dem N‐[2‐N′,N′‐(Dimethylaminoethyl)‐N‐methyl‐aminoethyl]‐ferrocenyl‐Liganden (η5‐C5H5)Fe{η5‐C5H3[CH(CH3)N(CH3)CH2CH2NMe2]‐2}

Heterobimetallic Complexes of Lithium, Aluminum, and Gold with the N ‐[2‐ N ′, N ′‐(dimethylaminoethyl)‐ N ‐methyl‐aminoethyl]‐ferrocenyl Ligand (η⁵‐C₅H₅)Fe{η⁵‐C₅H₃[CH(CH₃)N(CH₃)CH₂CH₂NMe₂]‐2} N‐[2‐N′,N′‐(dimethylaminoethyl)‐N‐methyl‐aminoethyl]ferrocene FcN,NH ( 1 ) reacts with ⁿBuLi under formation of the lithium organyl (FcN,N)Li ( 2 ). At reactions of 2 with AlBr₃ and AuCl · PPh₃ the heterobimetallic organo derivatives (FcN,N)AlBr₂ ( 3 ), (FcN,N)Au · PPh₃ ( 4 ) are formed. A detailed characterization of 2 – 4 was carried out by single crystal x‐ray analyses as well as by NMR and Mößbauer spectroscopy.     

Surprisingly Different Reaction Behavior of Alkali and Alkaline Earth Metal Bis(trimethylsilyl)amides toward Bulky N‐(2‐Pyridylethyl)‐N′‐(2,6‐diisopropylphenyl)pivalamidine

N‐(2,6‐Diisopropylphenyl)‐N′‐(2‐pyridylethyl)pivalamidine (Dipp‐N=C(tBu)‐N(H)‐C₂H₄‐Py) ( 1 ), reacts with metalation reagents of lithium, magnesium, calcium, and strontium to give the corresponding pivalamidinates [(tmeda)Li{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}] ( 6 ), [Mg{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}₂] ( 3 ), and heteroleptic [{(Me₃Si)₂N}Ae{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}], with Ae being Ca ( 2 a ) and Sr ( 2 b ). In contrast to this straightforward deprotonation of the amidine units, the reaction of 1 with the bis(trimethylsilyl)amides of sodium or potassium unexpectedly leads to a β‐metalation and an immediate deamidation reaction yielding [(thf)₂Na{Dipp‐N=C(tBu)‐N(H)}] ( 4 a ) or [(thf)₂K{Dipp‐N=C(tBu)‐N(H)}] ( 4 b ), respectively, as well as 2‐vinylpyridine in both cases. The lithium derivative shows a similar reaction behavior to the alkaline earth metal congeners, underlining the diagonal relationship in the periodic table. Protonation of 4 a or the metathesis reaction of 4 b with CaI₂ in tetrahydrofuran yields N‐(2,6‐diisopropylphenyl)pivalamidine (Dipp‐N=C(tBu)‐NH₂) ( 5 ), or [(thf)₄Ca{Dipp‐N=C(tBu)‐N(H)}₂] ( 7 ), respectively. The reaction of AN(SiMe₃)₂ (A=Na, K) with less bulky formamidine Dipp‐N=C(H)‐N(H)‐C₂H₄‐Py ( 8 ) leads to deprotonation of the amidine functionality, and [(thf)Na{Dipp‐N=C(H)‐N‐C₂H₄‐Py}]₂ ( 9 a ) or [(thf)K{Dipp‐N=C(H)‐N‐C₂H₄‐Py}]₂ ( 9 b ), respectively, are isolated as dinuclear complexes. From these experiments it is obvious, that β‐metalation/deamidation of N‐(2‐pyridylethyl)amidines requires bases with soft metal ions and also steric pressure. The isomeric forms of all compounds are verified by single‐crystal X‐ray structure analysis and are maintained in solution.     

Ansa‐Bridged Bis(benzene) Titanium Complexes

Taking advantage of an improved synthesis of [Ti(η⁶‐C₆H₆)₂], we report here the first examples of ansa‐bridged bis(benzene) titanium complexes. Deprotonation of [Ti(η⁶‐C₆H₆)₂] with nBuLi in the presence of N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (pmdta) leads to the corresponding 1,1′‐dilithio salt [Ti(η⁶‐C₆H₅Li)₂] ? pmdta that enables the preparation of the first one‐ and two‐atom‐bridged complexes by simple salt metathesis. The ansa complexes were fully characterized (NMR spectroscopy, UV/Vis spectroscopy, elemental analysis, and X‐ray crystallography) and further studied electrochemically and computationally. Moreover, [Ti(η⁶‐C₆H₆)₂] is found to react with the Lewis base 1,3‐dimethylimidazole‐2‐ylidene (IMe) to give the bent sandwich complex [Ti(η⁶‐C₆H₆)₂(IMe)].     

Halogenomercury Salts of Sterically Crowded Triazenides – Convenient Starting Materials for Redox‐Transmetallation Reactions

Diaryl‐substituted triazenides Ar(Ar′)N₃HgX [Ar/Ar′ = Dmp/Mph, X = Cl ( 2a ), Br ( 3a ), I ( 4a ); Ar/Ar′ = Dmp/Tph, X = Cl ( 2b ), I ( 4b ) with Mph = 2‐MesC₆H₄, Mes = 2,4,6‐Me₃C₆H₂, Tph = 2′,4′,6′‐triisopropylbiphenyl‐2‐yl and Dmp = 2,6‐Mes₂C₆H₃] were synthesized by salt‐metathesis reactions in ethyl ether from the readily available starting materials Ar(Ar′)N₃Li and HgX₂. These compounds may be used for redox‐transmetallation reactions with rare‐earth or alkaline earth metals. Thus, reaction of 4b or 2b with magnesium or ytterbium in tetrahydrofuran afforded the triazenides Dmp(Tph)N₃MX(thf) ( 5b : M = Mg, X = I; 6b : M = Yb, X = Cl) in good yield. All new compounds were characterized by melting point, ¹H and ¹³C NMR spectroscopy and for selected species by IR spectroscopy or mass spectrometry. In addition, the solid‐state structures of triazenides 2a , 2b , 3a , 4b , 5b and 6b were investigated by single‐crystal X‐ray diffraction.     

Preparation,characterization and luminescence‐sensing properties of two ZnII MOFs with mixed 5‐amino‐2,4,6‐tribromoisophthalic acid and bipyridyl‐type ligands

The bromo‐substituted aromatic dicarboxylic acid 5‐amino‐2,4,6‐tribromoisophthalic acid (H₂ATBIP), in the presence of the N‐donor flexible bipyridyl‐type ligands 1,3‐bis(pyridin‐4‐yl)propane (bpp) and N,N′‐bis(pyridin‐4‐ylmethyl)oxalamide (4‐bpme) and Zn^II ions, was used as an O‐donor ligand to assemble two novel luminescent metal–organic frameworks (MOFs), namely poly[[(μ‐5‐amino‐2,4,6‐tribromoisophthalato‐κ²O¹:O³)[μ‐1,3‐bis(pyridin‐4‐yl)propane‐κ²N:N′]zinc(II)] dimethylformamide monosolvate], {[Zn(C₈H₂Br₃NO₄)(C₁₃H₁₄N₂)]·C₃H₇NO}_n, ( 1 ), and poly[[(μ‐5‐amino‐2,4,6‐tribromoisophthalato‐κ²O¹:O³)diaqua[μ‐N,N′‐bis(pyridin‐4‐ylmethyl)oxalamide‐κ²N:N′]zinc(II)] monohydrate], {[Zn(C₈H₂Br₃NO₄)(C₁₄H₁₄N₄O₂)(H₂O)₂]·H₂O}_n, ( 2 ), using the solution evaporation method. Both ( 1 ) and ( 2 ) were characterized by FT–IR spectroscopy, elemental analysis (EA), solid‐state diffuse‐reflectance UV–Vis spectroscopy, and powder and single‐crystal X‐ray diffraction analysis. Complex ( 1 ) shows a two‐dimensional (2D) corrugated layer simplified as a 2D (4,4) topological network. The supramolecular interactions (π–π stacking, hydrogen bonding and C—Br…Br halogen bonding) play significant roles in the formation of an extended three‐dimensional (3D) supramolecular network of ( 1 ). Complex ( 2 ) crystallizes in the chiral space group P2₁2₁2₁ and exhibits a novel 3D homochiral framework, showing a diamond‐like topology with Schläfli symbol 6⁶. The homochirality of ( 2 ) is further confirmed by the solid‐state circular dichroism (CD) spectrum. The second harmonic generation (SHG) property of ( 2 ) was also investigated. The hydrogen and C—Br…Br/O halogen bonding further stabilize the framework of ( 2 ). The central Zn^II ions in ( 1 ) and ( 2 ) show tetrahedral and octahedral coordination geometries, respectively. The coordinated and uncoordinated water molecules in ( 2 ) could be removed selectively upon heating. Most importantly, ( 1 ) and ( 2 ) show rapid and highly sensitive sensing for a large pool of nitroaromatic explosives (NAEs).     

Synthesis of 3‐Alkoxybenzo[c]thiophen‐1(3H)‐ones by Hydrolysis of N‐Substituted 3‐Alkoxybenzo[c]thiophen‐1(3H)‐imines Derived from 1‐Bromo‐2‐(dialkoxymethyl)benzenes and Isothiocyanates

A convenient procedure for the preparation of a new type of thiophthalides, 3‐alkoxybenzo[c]thiophen‐1(3H)‐ones 4 and 9 has been developed. Thus, 1‐(dialkoxymethyl)‐2‐lithiobenzenes, generated by Br/Li exchange between 2‐bromo‐1‐(dialkoxymethyl)benzenes 1 and 6 , and BuLi, react with isothiocyanates to afford N‐substituted 2‐(dialkoxymethyl)benzothioamides 2 and 7 , which, on treatment with a catalytic amount of TsOH?H₂O, give N‐substituted 3‐alkoxybenzo[c]thiophen‐1(3H)‐imines 3 and 8 . The latter are hydrolyzed under acidic conditions to the desired products 4 and 9 , respectively.     

Preparation of new 2‐amino‐ and 2,3‐diamino‐pyridine trifluoroacetyl enamine derivatives and their application to the synthesis of trifluoromethyl‐containing 3H‐pyrido[2,3‐b][1,4] diazepinols

The synthesis of a novel series of the intermediates N²(N³)‐[1‐alkyl(aryl/heteroaryl)‐3‐oxo‐4,4,4‐trifluoroalk‐1‐en‐1‐yl]‐2‐aminopyridines [F₃CC(O)CH?CR¹(2? NH?C₅H₃N)] and 2,3‐diaminopyridines [F₃CC(O)CH?CR¹(2‐NH₂‐3‐NH? C₅H₃N)], where R¹ = H, Me, C₆H₅, 4‐FC₆H₄, 4‐CIC₆H₄, 4‐BrC₆H₄, 4‐CH₃C₆H₄, 4‐OCH₃C₆H₄, 4,4′‐biphenyl, 1‐naphthyl, 2‐thienyl, 2‐furyl, is reported. The corresponding series of 2‐aryl(heteroaryl)‐4‐trifluoromethyl‐3H‐pyrido[2,3‐b][1,4]diazepin‐4‐ols obtained from intramolecular cyclization reaction of the respective trifluoroacetyl enamines or from the direct cyclocondensation reaction of 4‐methoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,3‐diaminopyridine, under mild conditions, is also reported.     

Substituted Ferrocenylboranes – Potential Ligand Precursors for ansa‐ Metallocenes,Constrained Geometry Complexes and ansa‐Diamido Complexes

A wide range of potential ligand precursors and related compounds have been synthesized from ferrocenyldibromoborane and ferrocenylenebis(dibromoborane) via salt elimination reactions. These comprise ligand precursors suitable for the preparation of (i) ansa‐metallocenes such as [FcB(η¹‐C₅H₅)₂] ( 2 ), [FcB(1‐C₉H₇)₂] ( 3 ), [FcB(3‐C₉H₇)₂] ( 4 ) and [1,1′‐fc{B(3‐C₉H₇)₂}₂] ( 11 ), (ii) constrained geometry complexes such as [FcB(1‐C₉H₇)N(H)Ph] ( 7 ) and [FcB(3‐C₉H₇)N(H)Ph] ( 8 ), (iii) ansa‐diamido complexes such as [FcB(N(H)Ph)₂] ( 9 ) as well as (iv) the related compounds [FcB(Br)N(H)tBu] ( 5 ), [FcB(Br)N(H)Ph] ( 6 ), [1,1′‐fc{B(Br)N(SiMe₃)₂}₂] ( 12 ) and [1,1′‐fc{B(Br)NiPr₂}₂] ( 13 ) (Fc = ferrocenyl, fc = ferrocenylene, C₅H₅ = cyclopentadienyl, C₉H₇ = indenyl). All new compounds have been characterised by multinuclear NMR spectroscopic techniques and in the case of 7 and 12 by X‐ray diffraction methods.     

The Nitrogen‐Assisted Triphenylphosphine Displacement of 3‐Hydroxypyridine and 3‐Aminopyridine Ligands in Palladium(II) Complexes: Crystal Structures of [Pd(PPh3)Br]2{μ,η2‐C5H3N(OH)}2 and [Pd(PPh3)Br]2{μ,η2‐C5H3N(NH2)}2

Treatment of Pd(PPh₃₎₄ with 2‐bromo‐3‐hydroxypyridine [C₅H₃N(OH)Br] and 3‐amino‐2‐bromopyridine [C₅H₃N(NH₂)Br] in dichloromethane at ambient temperature cause the oxidative addition reaction to produce the palladium complex [Pd(PPh₃₎₂{η¹‐C₅H₃N(OH)}(Br)], 2 and [Pd(PPh₃₎₂{η¹‐C₅H₃N(NH₂)}(Br)], 3 , by substituting two triphenylphosphine ligands, respectively. In dichloromethane solution of complexes 2 and 3 at ambient temperature for 3 days, it undergo displacement of the triphenylphosphine ligand to form the dipalladium complexes [Pd(PPh₃)Br]₂{μ,η²‐C₅H₃N(OH)}₂, 4 and [Pd(PPh₃)Br]₂{μ,η²‐C₅H₃N(NH₂)}₂, 5 , in which the two 3‐hydroxypyridine and 3‐aminopyridine ligands coordinated through carbon to one metal center and bridging the other metal through nitrogen atom, respectively. Complexes 4 and 5 are characterized by X‐ray diffraction analyses.     

Formation of Organolithium Hetero‐Aggregates [Li4Ar2(nBu)2] (Ar=C6H4CH(Me)NMe2‐2) during the Directed ortho‐Lithiation of [1‐(Dimethylamino)ethyl]benzene

(R)‐[1‐(Dimethylamino)ethyl]benzene reacts with nBuLi in a 1:1 molar ratio in pentane to quantitatively yield a unique hetero‐aggregate ( 2 a ) containing the lithiated arene, unreacted nBuLi, and the complexed parent arene in a 1:1:1 ratio. As a model compound, [Li₄(C₆H₄CH(Me)NMe₂‐2)₂(nBu)₂] ( 2 b ) was prepared from the quantitative redistribution reaction of the parent lithiated arene Li(C₆H₄CH(Me)NMe₂‐2) with nBuLi in a 1:1 molar ratio. The mono‐Et₂O adduct [Li₄(C₆H₄CH(Me)NMe₂‐2)₂(nBu)₂(OEt₂)] ( 2 c ) and the bis‐Et₂O adduct [Li₄(C₆H₄CH(Me)NMe₂‐2)₂(nBu)₂(OEt₂)₂] ( 2 d ) were obtained by re‐crystallization of 2 b from pentane/Et₂O and pure Et₂O, respectively. The single‐crystal X‐ray structure determinations of 2 b – d show that the overall structural motifs of all three derivatives are closely related. They are all tetranuclear Li aggregates in which the four Li atoms are arranged in an almost regular tetrahedron. These structures can be described as consisting of two linked dimeric units: one Li₂Ar₂ dimer and a hypothetical Li₂nBu₂ dimer. The stereochemical aspects of the chiral Li₂Ar₂ fragment are discussed. The structures as observed in the solid state are apparently retained in solution as revealed by a combination of cryoscopy and ¹H, ¹³C, and ⁶Li NMR spectroscopy.     

Synthesis and structural characterization of iridium(I) complexes of 20‐membered macrocyclic rings bearing chelating bis(N‐heterocyclic carbene) ligands

The reactivities of two 20‐membered macrocyclic ligands, each containing two N‐heterocyclic carbene (NHC) and two amine groups, towards [IrCl(COD)]₂ (COD is cycloocta‐1,5‐diene) were investigated. Macrocycles containing imidazolin‐2‐ylidene groups formed the monometallic complex [(1,2,5,6‐η)‐cycloocta‐1,5‐diene](5,16‐dibenzyl‐1,5,9,12,16,20‐hexaazatricyclo[18.2.1.1^9,12]tetracosa‐10,21‐dien‐21,22‐diylidene)iridium(I) bromide dichloromethane monosolvate, [Ir(C₈H₁₂)(C₃₂H₄₂N₆)]Br·CH₂Cl₂, 2a . The structure of iridium complex 2a at 100 K has triclinic P symmetry. The ligand in 2a coordinates to the Ir center through the NHC moieties in a cis fashion. Additionally, the ligand adopts an umbrella‐like structure that appears to envelope the Ir center. The structure displays C—H…Br interactions. Macrocycles containing benzimidazolin‐2‐ylidene groups formed the bimetallic complex [μ‐5,20‐dibenzyl‐1,5,9,16,20,24‐hexaazapentacyclo[22.6.1.1^9,16.0^10,15.0^25,30]dotriaconta‐10(15),11,13,25(30),26,28‐hexaene‐31,32‐diylidene]bis{bromido[(1,2,5,6‐η)‐cycloocta‐1,5‐diene]iridium(I)}, [Ir₂Br₂(C₈H₁₂)₂(C₄₀H₄₆N₆)], 2b . The structure of complex 2b at 100 K has orthorhombic Pbca symmetry. Each NHC moiety in 2b coordinates in a monodentate fashion to an Ir(COD) fragment. The structure exhibits disorder of the main molecule. This disorder is found in the portion of the macrocycle containing an amine group. This structure also displays C—H…Br interactions. Finally, the structure of the hexafluorophosphate salt of the imidazolin‐2‐ylidene‐containing macrocycle, namely 5,16‐dibenzyl‐1λ⁵,5,9,12λ⁵,16,20‐hexaazatricyclo[18.2.1.1^9,12]tetracosa‐1(23),10,12(24),21‐tetraene‐1,12‐diium bis(hexafluorophosphate), C₃₂H₄₄N₆²⁺·2PF₆^?, 1c , was determined. The structure of macrocycle 1c at 100 K has triclinic P symmetry and was found to contain C—H…F interactions.     

Synthesis and Reactivity of Boron‐, Silicon‐, and Tin‐Bridged ansa‐Cyclopentadienyl–Cycloheptatrienyl Titanium Complexes (Troticenophanes)

A novel one‐pot method was developed for the preparation of [Ti(η⁵‐C₅H₅)(η⁷‐C₇H₇)] (troticene, 1 ) by reaction of sodium cyclopentadienide (NaCp) with [TiCl₄(thf)₂], followed by reduction of the intermediate [(η⁵‐C₅H₅)₂TiCl₂] with magnesium in the presence of cycloheptatriene (C₇H₈). The [n]troticenophanes 3 (n=1), 4 , 8 , 10 (n=2), and 11 (n=3) were synthesized by salt elimination reactions between dilithiated troticene, [Ti(η⁵‐C₅H₄Li)(η⁷‐C₇H₆Li)] ? pmdta ( 2 ) (pmdta=N,N′,N′,N′′,N′′‐pentamethyldiethylenetriamine), and the appropriate organoelement dichlorides Cl₂Sn(Mes)₂ (Mes=2,4,6‐trimethylphenyl), Cl₂Sn₂(tBu)₄, Cl₂B₂(NMe₂)₂, Cl₂Si₂Me₄, and (ClSiMe₂)₂CH₂, respectively. Their structural characterization was carried out by single‐crystal X‐ray diffraction and multinuclear NMR spectroscopy. The stanna[1]‐ and stanna[2]troticenophanes 3 and 4 represent the first heteroleptic sandwich complexes bearing Sn atoms in the ansa bridge. The reaction of 3 with [Pt(PEt₃)₃] resulted in regioselective insertion of the [Pt(PEt₃)₂] fragment into the Sn? C_ipso bond between the tin atom and the seven‐membered ring, which afforded the platinastanna[2]troticenophane 5 . Oxidative addition was also observed upon treatment of 4 with elemental sulfur or selenium, to produce the [3]troticenophanes [Ti(η⁵‐C₅H₄SntBu₂)(η⁷‐C₇H₆SntBu₂)E] ( 6 : E=S; 7 : E=Se). The B? B bond of the bora[2]troticenophane 8 was readily cleaved by reaction with [Pt(PEt₃)₃] to form the corresponding oxidative addition product [Ti(η⁵‐C₅H₄BNMe₂)(η⁷‐C₇H₆BNMe₂)Pt(PEt₃)₂] ( 9 ). The solid‐state structures of compounds 5 , 6 , and 9 were also determined by single‐crystal X‐ray diffraction.     

Synthesis,Structures and Reactivity of Lanthanoid(II) Formamidinates of Varying Steric Bulk

New reactive, divalent lanthanoid formamidinates [Yb(Form)₂(thf)₂] (Form=[RNCHNR]; R=o‐MeC₆H₄ (o‐TolForm; 1 ), 2,6‐Me₂C₆H₃ (XylForm; 2 ), 2,4,6‐Me₃C₆H₂ (MesForm; 3 ), 2,6‐Et₂C₆H₃ (EtForm; 4 ), o‐PhC₆H₄ (o‐PhPhForm; 5 ), 2,6‐iPr₂C₆H₃ (DippForm; 6 ), o‐HC₆F₄ (TFForm; 7 )) and [Eu(DippForm)₂(thf)₂] ( 8 ) have been prepared by redox transmetallation/protolysis reactions between an excess of a lanthanoid metal, Hg(C₆F₅)₂ and the corresponding formamidine (HForm). X‐ray crystal structures of 2 – 6 and 8 show them to be monomeric with six‐coordinate lanthanoid atoms, chelating N,N′‐Form ligands and cis‐thf donors. However, [Yb(TFForm)₂(thf)₂] ( 7 ) crystallizes from THF as [Yb(TFForm)₂(thf)₃] ( 7 a ), in which ytterbium is seven coordinate and the thf ligands are “pseudo‐meridional”. Representative complexes undergo C? X (X=F, Cl, Br) activation reactions with perfluorodecalin, hexachloroethane or 1,2‐dichloroethane, and 1‐bromo‐2,3,4,5‐tetrafluorobenzene, giving [Yb(EtForm)₂F]₂ ( 9) , [Yb(o‐PhPhForm)₂F]₂ ( 10) , [Yb(o‐PhPhForm)₂Cl(thf)₂] ( 11) , [Yb(DippForm)₂Cl(thf)] ( 12) and [Yb(DippForm)₂Br(thf)] ( 16) . X‐ray crystallography has shown 9 to be a six‐coordinate, fluoride‐bridged dimer, 12 and 16 to be six‐coordinate monomers with the halide and thf ligands cis to each other, and 11 to have a seven‐coordinate Yb atom with “pseudo‐meridional” unidentate ligands and thf donors cis to each other. The analogous terbium compound [Tb(DippForm)₂Cl(thf)₂] ( 13 ), prepared by metathesis, has a similar structure to 11 . C? Br activation also accompanies the redox transmetallation/protolysis reactions between La, Nd or Yb metals, Hg(2‐BrC₆F₄)₂, and HDippForm, yielding [Ln(DippForm)₂Br(thf)] complexes (Ln=La ( 14 ), Nd ( 15 ), Yb ( 16 )).     

Influence of Halogen Substitution in the Ligand Sphere on the Antitumor and Antibacterial Activity of Half‐sandwich Ruthenium(II) Complexes [RuX(η6‐arene)(C5H4N‐2‐CH=N‐Ar)]+

New complexes [(η⁶‐p‐cymene)Ru(C₅H₄N‐2‐CH=N–Ar)X]PF₆ [X = Br ( 1 ), I ( 2 ); Ar = 4‐fluorophenyl ( a ), 4‐chlorophenyl ( b ), 4‐bromophenyl ( c ), 4‐iodophenyl ( d ), 2,5‐dichlorophenyl ( e )] were prepared, as well as 3a – 3e (X = Cl) and the new complexes [(η⁶‐arene)RuCl(N‐N)]PF₆ (arene = C₆H₅OCH₂CH₂OH, N‐N = 2,2′‐bipyridine ( 4 ), 2,6‐(dimethylphenyl)‐pyridin‐2‐yl‐methylene amine ( 5 ), 2,6‐(diisopropylphenyl)‐pyridin‐2‐yl‐methylene amine ( 6 ); arene = p‐cymene, N‐N = 4‐(aminophenyl)‐pyridin‐2‐yl‐methylene amine ( 7 )]. X‐ray diffraction studies were performed for 1a , 1b , 1c , 1d , 2b , 5 , and 7 . Cytotoxicities of 1a – 1d and 2 were established versus human cancer cells epithelial colorectal adenocarcinoma (Caco‐2) (IC₅₀: 35.8–631.0 μM), breast adenocarcinoma (MCF7) (IC₅₀: 36.3–128.8.0 μM), and hepatocellular carcinoma (HepG2) (IC₅₀: 60.6–439.8 μM), 3a – 3e were tested against HepG2 and Caco‐2, and 4 – 7 were tested against Caco‐2. 1 – 7 were tested against non‐cancerous human epithelial kidney cells. 1 and 2 were more selective towards tumor cells than the anticancer drug 5‐fluorouracil (5‐FU), but 3a – 3e (X = Cl) were not selective. 1 and 2 had good activity against MCF7, some with lower IC₅₀ than 5‐FU. Complexes with X = Br or I had moderate activity against Caco‐2 and HepG2, but those with Cl were inactive. Antibacterial activities of 1a , 2b , 3a , and 7 were tested against antibacterial susceptible and resistant Gram‐negative and ‐positive bacteria. 1a , 2b , and 3a showed activity against methicillin‐resistant S. aureus (MIC = 31–2000 μg · mL^–1).     

A 1‐Aza‐2‐silacyclobut‐3‐ene and an Alkyne from [Li{Si(SiMe3)3}(thf)3] and the Isocyanide 2,6‐Me2C6H3NC

The novel zwitterionic heterocycle 1 was unexpectedly obtained from the reaction between [Li(SiR₃)(thf)₃] and ArNC. Upon heating 1 underwent an interesting ring opening to give the alkyne 2 . Hence the C≡C bond effectively arises from the C−C coupling of two ArNC moieties. R=SiMe₃, Ar=2,6‐Me₂C₆H₃, tmeda=N,N,N′,N′‐tetramethylethylenediamine.     

Hydrogen‐bonding patterns in 3‐alkyl‐3‐hydroxyindolin‐2‐ones

The molecules of racemic 3‐benzoylmethyl‐3‐hydroxyindolin‐2‐one, C₁₆H₁₃NO₃, (I), are linked by a combination of N—H...O and O—H...O hydrogen bonds into a chain of centrosymmetric edge‐fused R₂²(10) and R₄⁴(12) rings. Five monosubstituted analogues of (I), namely racemic 3‐hydroxy‐3‐[(4‐methylbenzoyl)methyl]indolin‐2‐one, C₁₇H₁₅NO₃, (II), racemic 3‐[(4‐fluorobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂FNO₃, (III), racemic 3‐[(4‐chlorobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂ClNO₃, (IV), racemic 3‐[(4‐bromobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂BrNO₃, (V), and racemic 3‐hydroxy‐3‐[(4‐nitrobenzoyl)methyl]indolin‐2‐one, C₁₆H₁₂N₂O₅, (VI), are isomorphous in space group P. In each of compounds (II)–(VI), a combination of N—H...O and O—H...O hydrogen bonds generates a chain of centrosymmetric edge‐fused R₂²(8) and R₂²(10) rings, and these chains are linked into sheets by an aromatic π–π stacking interaction. No two of the structures of (II)–(VI) exhibit the same combination of weak hydrogen bonds of C—H...O and C—H...π(arene) types. The molecules of racemic 3‐hydroxy‐3‐(2‐thienylcarbonylmethyl)indolin‐2‐one, C₁₄H₁₁NO₃S, (VII), form hydrogen‐bonded chains very similar to those in (II)–(VI), but here the sheet formation depends upon a weak π–π stacking interaction between thienyl rings. Comparisons are drawn between the crystal structures of compounds (I)–(VII) and those of some recently reported analogues having no aromatic group in the side chain.     

A new two‐dimensional ZnII coordination polymer based on 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and 5‐nitrobenzene‐1,3‐dicarboxylic acid: synthesis,crystal structure and physical properties

A novel two‐dimensional (2D) Zn^II coordination framework, poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene](μ‐5‐nitrobenzene‐1,3‐dicarboxylato)zinc(II)], [Zn(C₈H₃NO₆)(C₁₄H₁₄N₄)]_n or [Zn(NO₂‐BDC)(1,3‐BMIB)]_n [1,3‐BMIB is 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and NO₂‐H₂BDC is 5‐nitrobenzene‐1,3‐dicarboxylic acid], has been prepared and characterized by IR, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. Single‐crystal X‐ray diffraction analysis revealed that the compound is a new 2D polymer with a 6³ topology parallel to the (10) crystal planes based on left‐handed helices, right‐handed helical NO₂‐BDC–Zn chains and [Zn₂(1,3‐BMIB)₂]_n clusters. In the crystal, adjacent layers are further connected by C—H…O hydrogen bonds, C—H…π interactions, C—O…π interactions and N—O…π interactions to form a three‐dimensional structure in the solid state. In addition, the compound exhibits strong fluorescence emissions in the solid state at room temperature.