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.     

Reaktionen des tBu(Me3Si)P?P(Li)?P(tBu)2 mit CH3Cl und 1,2-Dibromethan

Reactions of tBu(Me₃Si)P? P(Li)? P(tBu)₂ with CH₃Cl and 1,2-Dibromoethane tBu(Me₃Si)P? P(Li)? P(tBu)₂ · 0.95 THF 1 with CH₃Cl (?70°C) yields tBu(Me₃Si)P? P = P(Me)(tBu)₂ 2 at ?70°C, with 1,2-Dibromoethane tBu(Me₃Si)P? PBr? P(tBu)₂ 3 (main product) and tBu(Me₃Si)P? P?P(Br)tBu₂ 4. 3 eliminates Me₃SiBr yielding the cyclotetraphosphane {tBuP? P[P(tBu)₂]}₂ 5 .     

Dendritic Iron Porphyrins with a Tethered Axial Ligand as New Model Compounds for Heme Monooxygenases

The novel iron(III) porphyrin dendrimers of generation zero ([ 1 ⋅Fe^III]Cl), one ([ 2 ⋅Fe^III]Cl), and two ([ 3 ⋅Fe^III]Cl) (Fig. 1) were prepared (Schemes 1 and 3) as models of heme monooxygenases. They feature controlled axial ligation at the Fe center by one imidazole tethered to the porphyrin core and possess a vacant coordination site available for ligand binding and catalysis. The high purity of the dendrimers and the absence of structural defects was demonstrated by matrix‐assisted laser‐desorption‐ionization time‐of‐flight (MALDI‐TOF) mass spectrometry (Fig. 3). The electronic properties of the Fe^III porphyrin dendrimers and comparison compounds [ 4 ⋅Fe^III]Cl and [ 12 ⋅Fe^III(1,2‐Me₂Im)]Cl (1,2‐Me₂Im=1,2‐dimethylimidazole) were investigated by UV/VIS and EPR (electronic paramagnetic resonance) spectroscopy, as well as by measurements of the magnetic moments by the Evans‐Scheffold method. Epoxidation of olefins and oxidation of sulfides to sulfoxides, catalyzed by the new dendritic metalloporphyrins, were investigated in CH₂Cl₂ with iodosylbenzene as the oxidant (Tables 1 and 2). The total turnover numbers were found to increase with the size of the dendrimer, due to improved catalyst stability at higher dendritic generations (Figs. 4 and 5). The second‐generation complex [ 3 ⋅Fe^III]Cl was, therefore, the most efficient catalyst in the series, despite the fact that its active site is considerably hindered by the encapsulation inside the sterically demanding, fluctuating dendritic wedges. Very high product selectivities were observed in all oxidation reactions, regardless of dendrimer generation.     

Beiträge zur Chemie des Phosphors. Synthese und Eigenschaften des 1,2-Diphospha-3,4-diboretans (t-BuP)2(BNMe2)2

Contributions tot he Chemistry of Phosphorus. 148. Synthesis and Properties of the 1,2-Diphospha-3,4-diboretane (t-BuP)₂(BNMe₂)₂ The first 1, 2-diphospha-3,4-diboretane (1,2-diphospha-3, 4-diboracyclobutane) (t-BuP)₂(BNMe₂)(1) was prepared by [2+2] cyclocondensation of K(t-Bu)P? P(t-Bu)K with Cl(Me₂N)B? B(NMe₂)Cl. 1 could be isolated in the pure state and was NMR spectroscopically characterized as a compound with a planar P₂ B₂ ring skeleton.     

Polarographische Bestimmung von 1,5-Dihydroxy-4,8-dinitro-anthrachinon (DNA) und seines Isomeren 1,8-Dihydroxy-4,5-dinitro-anthrachinon (DNC)

Zusammenfassung Zur quantitativen Analyse der Isomeren DNA und DNC, des Substanzgemisches und von Mischungen mit anderen Nitroderivaten wird die Polarographie von 0,1–0,3 g-Proben in Pyridin in Gegenwart von 1. NH₄Cl, NH₄OH, Na₂SO₃ und Nigrosinlösung; 2. Na₂SO₃ und Nigrosinlösung und 3. NH₄Cl, NH₄OH, Na₃SO₃ und Gelatinelösung mit einer Genauigkeit von ± 3% und einer Empfindlichkeit von 10^–2 durchgeführt.

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Polarographic determination of 1,5-dihydroxy-4,8-dinitroanthraquinone (DNA) and its isomer 1,8-dihydroxy 4,5-dinitroanthraquinone(DNC)

Quantitative analysis is carried out with the isomeric compounds, there mixtures and mixtures with other nitro derivatives. 0.1 to 0.3 g samples are applied in pyridine and polarographic recording is performed in the presence of 1) NH₄Cl, NH₄OH, Na₂SO₃ and nigrosine, 2) Na₂SO₃ and nigrosine, 3) NH₄Cl, NH₄OH, Na₂SO₃ and gelatin. Accuracy is ± 3%, sensitivity 10^–2.

     

(Me2NH2)[(Ph3Sn)3(MoO4)2], ein Triorganozinnmolybdat mit Schichtstruktur

(Me₂NH₂)[(Ph₃Sn)₃(MoO₄)₂], a Triorganotin Molybdate with Layer Structure The reaction of [(Ph₃Sn)₂MoO₄] with (Me₂NH₂)Cl in an acetonitrile/water mixture leads to the formation of (Me₂NH₂)[(Ph₃Sn)₃(MoO₄)₂] ( 1 ). ( 1 ) crystallizes in the space group Pca2₁ with a = 1967.0(4), b = 1353.1(2) and c = 2176.6(5) pm. In the crystal structure of 1 Ph₃SnO₂ bipyramides and MoO₄ tetrahedra are linked by corner sharing to give a layer structure. Additionally the layers are connected by O···H···N hydrogen bridges between MoO₄ groups and [Me₂NH₂]⁺ ions to give a 3D network structure.     

On the Reaction of [(CO)3Fe(μ‐Me2NCO)2Fe(CO)2(NHMe2)] with Chelating Ligands — X‐Ray Structures of New Binuclear μ‐Carbamoyl Complexes

Reaction of the binuclear μ‐carbamoyl complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(HNMe₂)] ( 1 ) in toluene with the chelating ligands Ph₂PCH₂PPh₂ (dppm) and Ph₂PCH₂CH₂PPh₂ (dppe) gives different results. With dppm only the complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(dppm)] ( 3 ) with a dangling ligand is obtained under replacement of amine, whereas with dppe depending on the reaction conditions up to three compounds are found. A 1 : 1 mixture of the educts generates the related complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(dppe)] ( 4 ) together with the tetranuclear complex [{(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂}₂(dppe)] (5 ). 4 slowly converts into [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)(dppe)] ( 6 ) with dppe acting as a chelating ligand. 6 is the first compound in this series in which one of the five CO groups is replaced by another donor. A 2 : 1 molar ratio of 1 and dppe quantitatively produces 5 . Addition of CO to a solution of 6 proceeds under slow reversible conversion of the complex into 4 . The compounds were characterized by the usual spectroscopic methods; 3 , 5 and 6 were also studied by X‐ray diffraction analyses.     

Über die Ammonolyse von Organometallen. XII. Die Ammonolyse von Dimethyl-diphenyl- und Dimethyl-dibenzyl-silan

Dimethyl-diphenyl and dimethyl-dibenzyl-silane react in liqu. NH₃ in the presence of KKH₂ giving rise to the formation of H₂N? Si(Me₂)? NH? Si(Me₃)? NHK (III); exclusively C₆H₅ and C₆H₅CH₂ are split off and substituted by NH₂. Reaction of the potassium compound III with the equivalent amount of NH₄Cl brings about a mixture of octamethylcyclotetrasilazane and hexamethylcyclotrisilazane.     

Effect of the Structure of Phase-Transfer Catalyst on the Rate of Alkaline Hydrolysis of N-Benzyloxycarbonylglycine 4-Nitrophenyl Ester in the System Chloroform-Borate Buffer

Onium salts QZ (Z = Cl, Br) having a lipophilic (Q = R₃NR', where R' = C₁₆H₃₃) or readily extractable (into organic phase) cation (Q = Ph₄P) exhibit a high catalytic activity in phase-transfer alkaline hydrolysis of N-benzyloxycarbonylglycine 4-nitrophenyl ester in the two-phase system chloroform-borate buffer (pH 10). No catalytic effect is observed in the presence of hydrophilic ammonium salts [Et₄NCl, Et₃PhCH₂NCl, Me₂(NH₂)+NCH₂CH₂+N(NH₂)Me₂·2Br^-] and those insoluble in organic solvents [(Me)₃+NNH(CH₂)₂COO^-·2H₂O, Me₂(NH₂)+NCH₂CO^-, Me₂(NH₂)+N(CH₂)₃SO₃ ^-]. These data suggest extraction mechanism of the process. The activity of lipophilic cation Q is determined mainly by two factors: its extractibility, on the one hand, and the ability to form micelles, on the other.     

Zur Reaktion von Permethylcyclosilanen mit Halogenen

The series of ,-diiodopermethylpolysilanes, I(SiMe ₂) _n I, (n=4–6) andX(SiMe ₂)₄ X, (X=Cl, Br) has been prepared by the action of halogen on the corresponding cyclic compounds (SiMe ₂) _n . The mass spectra, NMR-, IR- andRaman-spectra of these compounds have been recorded.

Herrn Prof. Dr.Josef Schurz zum 60. Geburtstag gewidmet.     

UV/Vis-spektroskopische Untersuchungen an Cyclosilanderivaten

UV/Vis-spectra of Cyclosilanes (SiX ₂) _n withX=Cl, Br, I, OMe andn=4, 5, 6 are recorded and interpreted qualitatively. The spectra exhibit increasing influence of the substituents on the Si-Si-bond system within the rings in the order Cl OMe Br I. At the low energy side of the spectra weak absorption bands, possibly due to intramolecular charge transfer transitions, appear. The strong inductive effect of the electronegative substituents is documented by a marked increase of the first IP's compared to permethylcyclosilanes.

     

Upon the hydrogen-bonding ability of the H4 and H5 protons of the imidazolium cation

The crystal and molecular structures of [Me₂Etim]Cl, [Me₂Etim]₂[CoCl₄], and [Me₂Etim]₂[NiCl₄] ([Me₂Etim]⁺ = 1,2-dimethyl-3-ethylimidazolium cation) all contain evidence that the H4 and H5 protons of the imidazolium cation enter into hydrogen bonds; the implications of this observation for the interactions in room-temperature chloroaluminate(III) ionic liquids are considered.     

Kernresonanzuntersuchungen an zeolithischen Heptagermanaten, 2. Mitt.

Zusammenfassung An zeolithischen Heptagermanaten der FormelMe ₃HGe₇O₁₆·xH₂O, (Me=NH₄, Li, Tl, Cs und Na;x=0–6) wurden Kernresonanzuntersuchungen durchgeführt. Es wurden Messungen an¹H und¹⁴N in Ammoniumzeolith sowie an⁷Li,²⁰⁵Tl,¹³³Cs und²³Na zwischen Zimmertemp. und der Temperatur des flüssigen Stickstoffs ausgeführt. Es zeigt sich, daß die Kationen Diffusionsbewegungen ausführen, die sowohl durch höhere Temperatur als auch durch das Vorhandensein von Wassermolekülen begünstigt werden.

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NMR investigation of zeolitic heptagermanates, II

Zeolitic heptagermanates with compositionMe ₃HGe₇O₁₆·xH₂O, (Me=NH₄, Li, Tl, Cs and Na;x=0–6) have been investigated by NMR. Measurements on¹H and¹⁴N in ammoniumzeolites and on⁷Li,²⁰⁵Tl,¹³³Cs and²³Na have been performed between room temperature and liquid nitrogen temperature. It is observed that the cations execute diffusional motions, which are favoured by higher temperature as well as by the presence of water molecules.

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Mit 9 Abbildungen     

Silicon‐ and Tin‐Containing Open‐Chain and Eight‐Membered‐Ring Compounds as Bicentric Lewis Acids toward Anions

Herein, we report the syntheses of silicon‐ and tin‐containing open‐chain and eight‐membered‐ring compounds Me₂Si(CH₂SnMe₂X)₂ ( 2 , X=Me; 3 , X=Cl; 4 , X=F), CH₂(SnMe₂CH₂I)₂ ( 7 ), CH₂(SnMe₂CH₂Cl)₂ ( 8 ), cyclo‐Me₂Sn(CH₂SnMe₂CH₂)₂SiMe₂ ( 6 ), cyclo‐(Me₂SnCH₂)₄ ( 9 ), cyclo‐Me_(2?n)X_nSn(CH₂SiMe₂CH₂)₂SnX_nMe_(2?n) ( 5 , n=0; 10 , n = 1, X= Cl; 11 , n=1, X= F; 12 , n=2, X= Cl), and the chloride and fluoride complexes NEt₄[cyclo‐ Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?F] ( 13 ), PPh₄[cyclo‐Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?Cl] ( 14 ), NEt₄[cyclo‐Me(F)Sn(CH₂SiMe₂CH₂)₂Sn(F)Me?F] ( 15 ), [NEt₄]₂[cyclo‐Cl₂Sn(CH₂SiMe₂CH₂)₂SnCl₂?2 Cl] ( 16 ), M[Me₂Si(CH₂Sn(Cl)Me₂)₂?Cl] ( 17 a , M=PPh₄; 17 b , M=NEt₄), NEt₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?F] ( 18 ), NEt₄[Me₂Si(CH₂Sn(F)Me₂)₂?F] ( 19 ), and PPh₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?Br] ( 20 ). The compounds were characterised by electrospray mass‐spectrometric, IR and ¹H, ¹³C, ¹⁹F, ²⁹Si, and ¹¹⁹Sn NMR spectroscopic analysis, and, except for 15 and 18 , single‐crystal X‐ray diffraction studies.     

Chelatliganden auf Basis peralkylierter Bis‐ und Tris‐Guanidine

Chelat Ligands Based on Peralkyl Bis‐ and Tris‐Guanidines By reaction of bi‐ and trifunctional primary alkyl amines with the chlor amidinium salt [(Me₂N)₂C–Cl]Cl amine functionalities are transformed into more basic peralkyl guanidine functionalities. This synthetic strategy is used in the synthesis of new peralkyl bis‐ and tris‐guanidines 1 a and 2 – 4 . The ligand 1,1,1‐tris[2N‐(1,1,3,3‐tetramethylguanidino)methyl]ethane ( 4 ), reacts with ZnCl₂ und MnCl₂ to yield neutral 1 : 1 complexes 5 and 6 with one non‐coordinating dangling guanidine functionality and a tetrahedrally coordinated metal atom. The crystal structure analysis of the hydrochloride 1 b of octamethyl bis guanidine 1,2di[2N‐(1,1,3,3‐tetramethylguanidino)]ethane ( 1 a ) as well as the one of the zinc complex 5 are reported.     

Crystal Structure and Spectroscopic Properties of Bis[trans‐dichlorobis(2,2‐dimethylpropane‐1,3‐diamine)chromium(III)] Tetrachlorozincate

The structure of trans‐[Cr(Me₂tn)₂Cl₂]₂ZnCl₄ (Me₂tn = 2,2‐dimethylpropane‐1,3‐diamine) was determined by a single‐crystal X‐ray diffraction study at 173 K. The analysis reveals that there are three crystallographically independent chromium(III) complex cations in the title compound. The chromium(III) atoms are coordinated by four nitrogen atoms of Me₂tn and two chlorine atoms in a trans arrangement, displaying a distorted octahedral geometry. The two six‐membered chelate rings in three complex cations are oriented in an anti chair–chair conformation with respect to each other. The Cr–N and Cr–Cl bond lengths average 2.0862(2) and 2.3112(6) Å, respectively. The ZnCl₄^2– have slightly distorted tetrahedral arrangement with Zn–Cl lengths and the Cl–Zn–Cl angles are influenced by hydrogen bonding. The resolved absorption maxima in the electronic d–d spectrum were fitted with a secular determinant for a quartet energy state of the d³ configuration in a tetragonal field. It is confirmed that the nitrogen atoms of the Me₂tn ligand are strong σ donors, but the chloro ligands have weak σ‐ and π donor properties toward the chromium(III) ion.     

Ruthenium(II)-Phthalocyaninate(2–): Darstellung und Eigenschaften von Acido(carbonyl)phthalocyaninato(2–)ruthenat(II), [Ru(X)(CO)Pc2−]− (X = Cl,Br, I,NCO, NCS,N3)

Ruthenium(II) Phthalocyaninates(2–): Synthesis and Properties of (Acido)(carbonyl)phthalocyaninato(2–)ruthenate(II), [Ru(X)(CO)Pc^2?]^? (X = Cl, Br, I, NCO, NCS, N₃) (ⁿBu₄N)[Ru(OH)₂Pc^2?] is reduced in acetone with carbonmonoxid to blue-violet [Ru(H₂O)(CO)Pc^2?], which yields in tetrahydrofurane with excess (ⁿBu₄N)X acido(carbonyl)phthalocyaninato(2–)ruthenate(II), [Ru(X)(CO)Pc^2?]^? (X = Cl, Br, I, NCO, NCS, N₃) isolated as red-violet, diamagnetic (ⁿBu₄N) complex salt. The UV-Vis spectra are dominated by the typical π-π* transitions of the Pc^2? ligand at approximately 15100 (B), 28300 (Q₁) und 33500 cm^?1 (Q₂), only fairly dependent of the axial ligands. v(C? O) is observed at 1927 (X = I), 1930 (Cl, Br), 1936 (N₃, NCO) 1948 cm^?1 (NCS), v(C? N) at 2208 cm^?1 (NCO), 2093 cm^?1 (NCS) and v(N? N) at 2030 cm^?1 only in the MIR spectrum. v(Ru? C) coincides in the FIR spectrum with a deformation vibration of the Pc ligand, but is detected in the resonance Raman(RR) spectrum at 516 (X = Cl), 512 (Br), 510 (N₃), 504 (I), 499 (NCO), 498 cm^?1 (NCS). v(Ru? X) is observed in the FIR spectrum at 257 (X = Cl), 191 (Br), 166 (I), 349 (N₃), 336 (NCO) and 224 cm^?1 (NCS). Only v(Ru? I) is RR-enhanced.     

Basische metalle : XX. Synthese und reaktivität von C6Me6Ru(CO)PMe3. Ein stabiler aromaten-ruthenium(0)-carbonyl-komplex

Treatment of [C₆Me₆RuCl₂]₂ with carbon monoxide gives C₆Me₆Ru(CO)Cl₂ (II) which reacts with PMe₃ in the presence of NH₄PF₆ to form [C₆Me₆Ru(CO)(PMe₃)Cl]PF₆ (III). Reduction of the cation of III with NaC₁₀H₈ in THF yields C₆Me₆Ru(CO)PMe₃ (IV) which is the first stable mononuclear areneruthenium(0) carbonyl complex. IV reacts with CF₃COOH/NH₄PF₆ and MeI/NH₄PF₆ to give the stable salts [C₆Me₆RuH(CO)PMe₃]PF₄ (V) and [C₆Me₆RuCH₃(CO)PMe₃]PF₆ (VI).     

Ringsubstituierte [1]titanocenophane

The ring-substituted bis(cyclopentadienyl)silanesMe ₂Si(C₅H₅) (MeC₅H₄) (1a) andMe ₂Si(MeC₅H₄)₂ (2a) could be prepared by the reactions ofMe ₂SiCl₂ with C₅H₅Na andMeC₅H₄Na or only withMeC₅H₄Na, respectively. Metallation of1 a or2 a withn-BuLi and following reaction with TiCl₄ led to the first ringsubstituted [1]titanocenophanes,Me ₂Si(C₅H₄) (MeC₅H₃)TiCl₂ (1 b) orMe ₂Si(MeC₅H₃)₂ TiCl₂ (2 b), respectively. On reaction with NaI,1 b yieldedMe ₂Si(C₅H₄) (MeC₅H₃)TiI₂ (1 c). Structural assignments of the compounds could be made on the basis of their¹H NMR spectra.

     

Towards Functionalized Silicon‐Containing α‐Amino Acids: Asymmetric Syntheses of Sila Analogs of Homoserine and Homomethionine

The homoserine and homomethionine sila analogs, (R)‐HOSi(Me₂)CH₂CH(NH₂)CO₂H ((R)‐ 21 ) and (R)‐MeSCH₂Si(Me₂)CH₂CH(NH₂)CO₂H ((R)‐ 24 ), respectively, were each synthesized in nine steps and in 30 and 23% overall yield, respectively, from commercially available ClSiMe₂CH₂Cl. The key step of both syntheses was the asymmetric α‐bromination of an Evans amide to introduce the stereogenic center of the amino acids with defined absolute configuration. While the preparation of the homomethionine analog (R)‐ 24 followed the expected pathway, the sila analog of homoserine, (R)‐ 21 , was unexpectedly formed during the catalytic hydrogenation of an N₃CH₂‐substituted silane derivative.