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Die (Cymol)Ruthenium-Halbsandwich-Komplexe K1 und K2 mit chiralen Pyrroloxazolin-Liganden wurden synthetisiert und charakterisiert. Die Komplexe bilden Diastereomere, die sich nur in der Metallkonfiguration unterscheiden. Der Komplex K1 kristallisiert in Form des reinen Diastereomers SRu, SC4, RC5. In Losung erfolgt Epimerisierung SRu, SC4, RC5 ⇌ RRu, SC4, RC5 durch Konfigurationsanderung am Rutheniumatom. Die Halbwertszeit fur diese Reaktion erster Ordnung bei 0.4 °C in CD2Cl2 betragt 50.6 min. Damit stehen die beiden Diastereomeren bei Raumtemperatur miteinander im Gleichgewicht. Die Gleichgewichtsgemische von K1 und K2 wurden als Katalysatoren fur die Transferhydrierung von Acetophenon und fur die Diels-Alder-Reaktion von Cyclopentadien mit Methacrolein eingesetzt. Dabei wurden Enantiomerenuberschusse bis 60 % ee erreicht. Asymmetric Catalysis. 155 [1] (Cymene)Ruthenium Halfsandwich Complexes with Pyrroleoxazoline Ligands — Synthesis, Stereochemistry, Catalysis The (cymene)ruthenium halfsandwich complexes K1 and K2 with chiral pyrroleoxazoline ligands were synthesized and characterized. The complexes form diastereomers, which only differ in the metal configuration. Complex K1 crystallized as the pure diastereomer SRu, SC4, RC5. In solution epimerization SRu, SC4, RC5 ⇌ RRu, SC4, RC5 occurred via change of the configuration at the ruthenium atom. The half-life for the first-order reaction at 0.4 °C in CD2Cl2 was 50.6 min. Thus, the two diastereomers equilibrate at room temperature. The equilibrium mixtures of K1 und K2 were used as catalysts for the transfer hydrogenation of acetophenone and for the Diels-Alder reaction of cyclopentadiene with methacrolein. Enantiomeric excesses of up to 60 % ee were achieved.

The trinuclear complex [Pt2Rh(μ3-S)2{(−)-diop}2(cod)]Cl (3) was synthesized starting from the chiral “ligand” [Pt2(μ-S)2{(−)-diop}] (2) and [Rh(cod)Cl]2, and characterized by X-ray crystallography. Compound 3 was used as a catalyst in the hydrosilylation of acetophenone with diphenylsilane and in the hydrogenation of ketopantolactone.

The preparation of cyclic 10-membered tetrahydroxy enediynes is reported. The synthesis starts from tartaric acid and allows the control of the relative stereochemistry. Acetal protection of the 2,3-hydroxy groups stabilizes the enediyne during synthesis. Removal of the cyclic protecting group with EtSH/TFA transforms the stable compounds into reactive enediynes, and the rate constants of their cyclization were determined in benzene and water. The cytoxicity of the activated compounds was assayed against tumor cells in vitro, but the growth inhibitory effect was weak compared to cisplatin.

The synthesis of new chiral tridentate ligands is reported which coordinate transition metals in a meridional way. The ligands contain a pyridine ring, an oxazoline ring, and a strongly coordinating diphenylphosphanyl group. The methionine-derived ligand forms a copper complex, which has been studied by X-ray crystallography. The new ligands were tested in models of enantioselective catalyses, such as hydrogenation of ketopantolactone, hydrosilylation of acetophenone, and transfer hydrogenation of acetophenone.

Chiral binaphthyl compounds, especially those with different substituents in 2- and 2’-position of the binaphthyl system, have gained interest as constituents of successful ligands in various catalytic reactions. Here, we present the synthesis and characterization of new binaphthyl ligands containing oxazoline, cyano and amide substituents in 2’-position in addition to methoxy, hydroxy or amino groups in 2-position. Starting from these compounds new ligands for enantioselective catalysis will be accessible.

The reaction of the cluster salts [Cp* 2 Nb(CO) 2 ] n [Co 1 1 Te 7 (CO) 1 0 ] (Cp* = C 5 Me 5 ; n = 1, 2) with excess PMe 2 Ph gave the neutral, dark brown clusters [Co 1 1 Te 7 (CO) 6 (PMe 2 Ph) 4 ] (5) and [Co 1 1 Te 7 (CO) 5 (PMe 2 Ph) 5 ] (6) with 147 metal valence electrons. The new compounds were characterized by IR spectroscopy, elemental analyses, and mass spectrometry. The molecular structure of 6 was determined by X+ray crystallography. Like its precursor anion, it consists of a pentagonal-prismatic [Co 1 1 Te 7 ] core, but with a ligand sphere composed of five CO and five PMe 2 Ph ligands. Detailed electrochemical studies of both reactions reveal that a stepwise substitution of CO ligands in the initial cluster anions takes place leading to intermediate [Co 1 1 Te 7 (CO) 1 0 - m (PMe 2 Ph) m ] n - ions (m = 1 - 5; n = 1, 2). Each of these intermediates is distinguished by at least one oxidation and two reduction waves, giving rise to a total of 21 redox couples and 27 electroactive species. The electron sponge character of the new compounds is particularly pronounced in 5, which exhibits charges n between + 1 and - 4 corresponding to metal valence electron counts of between 146 and 151.

The use of nitrogen-containing ligands for asymmetric catalysis has received growing interest in the last years. In this paper we report the synthesis of three new ligands (5c, 5d and 6) and the X-ray structure analysis of 5c and of the copper(II) complex 6-Cu(II)OTf. The catalytic activity of the ligands was tested in standard asymmetric reactions, but in most of the cases only low yields and poor enantioselectivity was obtained.

The complexes Cp*Rh(beapy)Cl (5) and Cp*Ir(beapy)Cl (6) were synthesized by reaction of [Cp*MCl2]2 (M=Rh, Ir) and the deprotonated ligand Hbeapy, the condensation product of benzylamine and 2-pyrrolcarbaldehyde. In each case two enantiomers (SM) and (RM) arise, differing only in the metal chirality. The CH2 group of the benzyl substituent in the ligand forms an AB spectrum which was used for 1H NMR coalescence measurements (Tc=115.1 °C). The half-life for the racemization of Cp*Rh(beapy)Cl (5) was 46 ms at 115.1 °C. Substitution of the chloride ligand in Cp*Rh(pepy)Cl (3), pepy anion of Schiff base (+)-2-N-[(S)-1-phenylethyl]pyrrolcarbaldimine, afforded the complexes Cp*Rh(pepy)Br (7) and Cp*Rh(pepy)I (8). Single crystals of the two compounds contained only one of the two diastereomers. In solution the compounds epimerized via a change of the metal configuration, the half-life for (RRh,SC)-Cp*Rh(NN*)I (8) being 40.8 min at −40 °C in CD2Cl2 solution (obtained by time dependent integration of suitable 1H NMR signals). Reaction of [CpRhCl2]2 with (+)-N-[(S)-1-phenylethyl]salicylaldimine gave CpRh(pesa)Cl (9). Surprisingly, single crystals of 9 contained both diastereomers (RRh,SC) and (SRh,SC) in a 1:1 ratio following the molecular recognition motif of the inverted pianostools. The half-lifes for the epimerization of 9 with respect to the metal center, derived from 1H NMR coalescence experiments, were 31 and 9.2 ms at 11.3 °C (CD2Cl2) for the forward and back reactions, respectively.

New nitrogen-containing ligands derived from the (1R,2R)-trans-cyclohexanediamine chiral core unit have been synthesized and fully characterized. Their catalytic activity was tested in the asymmetric addition of diethylzinc to aldehydes leading to the respective secondary alcohols with enantioselectivities of up to 74% ee.

The Wilkinson-type catalysts [Rh(diop)(PPh3)Cl] and [Rh(diop)(PPh3)I] have been synthesised and characterised by X-ray structure analysis. In the crystal the distorted square planar compounds form pairs of diastereomers. The compounds were tested as catalysts in the enantioselective hydrogenation of ketopantolactone. With 65 % ee the iodo complex achieved a higher enantioselectivity than the chloro complex (55 % ee). Asymmetric Catalysis. 151 [1] Katalysatoren [Rh(diop)(PPh3)Hal] vom Wilkinson-Typ in der enantioselektiven Hydrierung von Ketopantolacton Die Wilkinson-artigen Katalysatoren [Rh(diop)(PPh3)Cl] und [Rh(diop)(PPh3)I] wurden synthetisiert und durch Rontgenstrukturanalyse charakterisiert. Im Kristall bilden die verzerrt quadratisch-planaren Verbindungen Paare von Diastereomeren. Die Verbindungen wurden als Katalysatoren in der enantioselektiven Hydrierung von Ketopantolacton getestet. Dabei ergab der Iod-Komplex mit 65 % ee hohere Enantioselektivitaten als der Chlor-Komplex mit 55 % ee.

The synthesis of new hydrolytically stable oxime ether ligands by condensation of various aldehydes with O-β- d -glucopyranosylhydroxylamine 1 or O-β- d -galactopyranosylhydroxylamine 4 is described. After peracetylation of the hydroxyl groups, ligands soluble in organic solvents were obtained. The ligands have been tested in transition metal-catalysed reactions. Phosphorus-containing ligands gave high yields in palladium-catalysed allylic alkylation and rhodium-catalysed hydrosilylation reactions although the enantioselectivities were low. A 1,3-diphenylallyl–palladium(II) complex of ligand 2b was prepared and its structure was established by X-ray diffraction analysis.

Condensation of a number of optically active amines and α-amino acid esters with salicylaldehyde gave the chiral compounds HLL*-1−HLL*-8. A series of diastereomeric complexes of the type (RM,SC)- and (SM,SC)-[(η6-arene)M(LL*)X] (1−14: M = Ru, Os; X = Cl, I), differing only in the metal configuration, were formed by reaction of [(η6-arene)MCl2]2 with these compounds in the presence of base and by halogen exchange. Five of the complexes were characterized by X-ray structure analyses. Three cases showed the structural peculiarity that the single crystals contained the RM,SC and SM,SC diastereomers with opposite configurations at the metal centers in a 1:1 ratio, whereas two cases crystallized as pure RM,SC diastereomers. Two complexes, the ligands of which (the salicylaldiminates of methyl phenylalaninate and methyl phenylglycinate) had racemized during the synthesis, crystallized as racemates RRu,SC/SRu,RC. Complexes 1−14 were tested as catalysts in the enantioselective isomerization of 2-n-butyl-4,7-dihyd...

The stereoselective Pd-catalyzed allylation of MBA [5-(2′-hex-3′-ynyl)-1-methylbarbituric acid] gives the commercial injection narcotic methohexital, which exists as four isomers: two diastereomeric pairs of enantiomers. The isomer composition produced depends on three stereochemical parameters: catalyst control, substrate control, and kinetic resolution. Judicious choice of these parameters allowed the synthesis of methohexital samples with greatly differing isomer compositions, and these samples were investigated with respect to their anaesthetic doses in rats. Some isomer compositions obtained were much more active than the commercially used drug and showed fewer side effects. As a consequence of the determination of the absolute configuration of the methohexital (SbRh) isomer, the unknown configuration of the trade product, the so-called α-racemate, can be established as (RbSh) and (SbRh). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Ortho-metalated derivatives of the optically active ligand (S)-(−)-N,N-dimethyl(1-phenylethyl)amine (LL*-H) react with [(η6-p-cymene)MCl2]2 (M=Ru, Os) to give the half-sandwich complexes [(η6-p-cymene)Ru(LL*)Cl] (1a,b) and [(η6-p-cymene)Os(LL*)Cl] (2a,b). In both cases two diastereomers (RM,SC) and (SM,SC) arise differing only in the metal configuration. On crystallization the (RM,SC)-isomers of both complexes 1 and 2 were obtained diastereomerically pure. The absolute configurations were established by X-ray structure analyses. Epimerization studies clearly showed that the metal configuration in both complexes is labile in solution.

The synthesis of two new zinc(II) complexes with 1,4,7,10-tetraazacyclododecan-1-ol and 1,4,7,10-tetraazacyclododecan-1,7-diol as ligands is described. One of these complexes is characterized by X-ray structure analysis. By coordination to the metal cation the acidity of the hydroxylamine groups of the ligands is significantly increased as confirmed by potentiometric pH titrations.

Neutral and cationic half-sandwich (η 6 -p-cymene)ruthe-nium complexes 9-12 with chiral Schiff base ligands derived from binaphthylamino derivatives and salicylaldehyde, diphenyl(2-formylphenyl)phosphane, and 2-pyridinealdehyde form two diastereomers which only differ in the metal configuration. From the diastereomeric mixtures of compounds 10 and 12 the major diastereomers crystallize, whereas for compound 9 both diastereomers co-crystallize in a 1:1 ratio in the same single crystal. In compounds 13 and 14 containing the reduced Schiff base ligands, the nitrogen atom of the secondary amine functionality becomes another chiral center. In solution at room temperature the various diastereomers interconvert rapidly. The new compounds were used as catalysts in the enantioselective transfer hydrogenation of acetophenone with 2-propanol and in the Diels-Alder reaction of cyclopentadiene with methacrolein.

The reaction of K 3 SbS 3 with [Cp* 2 Co 2 I 4 ] (Cp*=C 5 Me 5 ) gave dark brown [Cp* 3 Co 3 (μ 3 -S)(μ 3 -SbS 4 I)] ( 1 ) in 22% yield. Complex 1 was characterized by 1 H-NMR and mass spectra. The crystal structure determination reveals as the central feature a distorted Co 3 SbS 4 cube with the fifth sulfur atom being inserted into one of the three SbS edges. The coordination sphere around the Sb atom in the unprecedented tripodal ψ-Sb(S 2 )S 2 -ligand is extended by a weakly coordinated iodine atom [ d (SbI)=3.215(1) A].

The reaction of [(η7-C7H7)Mo(η6-C6H5CH3)]BF4 with the optically active Schiff base ligands LL1−LL3 (LL1 = pyridine-2-carbald-(S)-1-phenylethylimine, LL2 = 6-methylpyridine-2-carbald-(S)-1-phenyleth...

The chiral-at-metal cycloheptatrienyl-molybdenum complexes (RMo, SC)-[(η7-C7H7)Mo(iminphos)(CO)]BF4 (2a) and (SMo, SC)-[(η7-C7H7)Mo(iminphos)(CO)]BF4 (2b) (iminphos = 2-[N-(S)-1-phenylethylcarbaldimino]phenyl(diphenyl)phosphane), which only differ in the molybdenum configuration, were prepared and separated by fractional crystallization. The absolute configuration for both diastereomers was determined by X-ray analysis. 1H NMR studies demonstrated the configurational lability at the molybdenum centre in solution. Optisch aktive Ubergangsmetall-Komplexe. 128 [1] Synthese, Charakterisierung und Molekulstrukturen von chiralen Cycloheptatrienyl-Iminphos-Molybdan-Komplexen mit unterschiedlicher Metallkonfiguration Die am Metall chiralen Cycloheptatrienyl-Molybdan-Komplexe (RMo, SC)-[(η7-C7H7)Mo(iminphos)(CO)]BF4 (2a) und (SMo, SC)-[(η7-C7H7)Mo(iminphos)(CO)]BF4 (2b) (iminphos = -2-[N-(S)-1-Phenylethylcarbaldimino]phenyl(diphenyl)phosphan), die sich nur in der Konfiguration am Molybdanatom unterscheiden, wurden dargestellt und durch fraktionierende Kristallisation getrennt. Die absolute Konfiguration wurde fur beide Diastereomere durch Kristallstrukturanalyse bestimmt. Durch 1H-NMR-spektroskopische Untersuchungen konnte die Konfigurationslabilitat des Metallzentrums nachgewiesen werden.

The (+)-9-phenyldeltacyclanyl moiety as a chiral phosphorus substituent contains eight configurationally fixed asymmetric carbon atoms. It is easily obtained from the reaction of norbornadiene and phenylacetylene via a Co-catalyzed enantioselective homo-Diels−Alder reaction, to give (+)-8-phenyldeltacyclene. In the reaction of (+)-8-phenyldeltacyclene with 1,2-(H2P)2C6H4 the trisubstitution product P,P,P′-tris[(+)9-phenyldeltacyclan-8-yl)-1,2-bis(phosphanyl)benzene, (+)δ-LH, is obtained, in which a single P−H bond at the stereogenic phosphorus atom is left. (+)δ-LH crystallizes as a pure diastereomer, which isomerizes in solution with respect to the secondary phosphorus atom at −20 °C resulting in a 64:36 diastereomer mixture. Substitution of the P−H hydrogen atom in (+)δ-LH by benzyl, 3-bromobenzyl, 6-bromo-n-hexyl and 3-(diphenylphosphanyl)phenyl gave the bis(tertiary) diphosphanes (+)δ-LR1−(+)δ-LR4. NiBr2, PdHal2 (Hal = Cl, Br, I) and PtHal2 (Hal = Cl, Br) complexes of (+)δ-LH and (+)δ-LR1−(+)δ-LR4have been synthesized. The complexes form two diastereomers differing in the configuration of the chiral P atom. X-ray structure analyses have been carried out with (+)δ-LH, [(+)δ-LR2]NiBr2, [(+)δ-LH]PdI2 and [(+)δ-LCl]PdI2. Interestingly, for [(+)δ-LH]PdI2 both diastereomers are found in the same crystal lattice in a 1:1 ratio. In [(+)δ-LH]PdI2 and [(+)δ-LCl]PdI2the configuration at the secondary phosphorus atom is stable in solution at room temperature, whereas in the free ligand (+)δ-LH it is configurationally labile. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The reaction of [Cp* 2 Nb(Te 2 H)] ( 1 ) (Cp*=C 5 Me 5 ) with [Ru 3 (CO) 12 ] in boiling toluene gave [Ru 3 (μ 2 -H) 2 (CO) 9 (μ 3 -Te)] ( 2 ), [Ru 6 (μ 3 -H)(CO) 15 (μ 3 -Te) 3 ][Cp* 2 Nb(CO) 2 ] ( 3 ) and [Ru 5 (μ 2 -H)(CO) 14 (μ 4 -Te)][Cp* 2 Nb(CO) 2 ] ( 4 ) along with already known [Ru 4 (CO) 11 (μ 4 -Te) 2 ] ( 5 ). Complexes 2 – 4 were analytically and spectroscopically characterized and X-ray diffraction analyses of 3 and 4 were carried out. The anion of 3 is built up of a triangular hexametallic core of C 3 v symmetry, in which the central Ru 3 triangle, being bridged by a μ 3 -H ligand, is composed of three corner-linked Ru 3 Te tetrahedra. The main structural feature of the anion of 4 is a Ru 5 Te octahedron. The cations in 3 and 4 are known niobocenedicarbonyl species. The reaction of 2 with bis(diphenylphosphino)methane (dppm) gave [Ru 3 (μ 2 -H) 2 (CO) 7 (dppm)(μ 3 -Te)] ( 6 ). Low temperature 1 H-NMR spectroscopy and X-ray diffraction analysis show an unsymmetrical distribution of both hydride ligands over the triangular Ru 3 basis of the Ru 3 Te tetrahedron. The reaction of 5 with dppm gave [Ru 3 (CO) 7 (dppm)(μ 3 -Te) 2 ] ( 7 ) and known [Ru 4 (CO) 9 (dppm)(μ 4 -Te) 2 ] ( 8 ). The crystal structure of 7 reveals a square pyramidal arrangement of the Ru 3 Te 2 core. Electrochemical studies of 5 show this complex to be able to consume up to four electrons in reversible steps.

Substituted phenazines 7 and 15 with two urea units have been prepared and characterized. X-ray structure analyses are reported for intermediates 5, 9, 11b and 12. According to theoretical calculations the geometry of the two urea moieties in phenazines 7 and 15 should be well suited for the binding of trigonal planar anions, such as nitrate. NMR titration revealed that compound 15 indeed shows a weak interaction with nitrate ions in DMSO.

The reaction of [Cp‘2Nb(Te2)H] (1) (Cp‘ = tBuC5H4) with [Fe2(CO)9] gives [{Cp‘2NbH(Te)2}Fe2(CO)6] (2). Compound 2 reacts with [Cr(CO)5THF] to give [{Cp‘2NbH(Te)2Fe2(CO)6}·Cr(CO)5] (3) in nearly qua...

A new way of linking carbohydrates to phosphorus- or nitrogen-containing aldehydes via oxime ethers is described resulting in novel CN ligands which are stable towards hydrolysis. Reaction of O -β- d -glucopyranosylhydroxylamine 2 with 2-diphenylphosphanylbenzaldehyde 3 or pyridine-2-carbaldehyde 4 afforded the oxime ethers O -(β- d -glucopyranosyl)-2-diphenylphosphanylbenzaldoxime 5 and O -(β- d -glucopyranosyl)pyridine-2-carbaldoxime 6 . After peracetylation of the hydroxyl groups in 5 and 6 , the protected sugar derivatives O -(2,3,4,6-tetra- O -acetyl-β- d -glucopyranosyl)-2-diphenylphosphanylbenzaldoxime 7 and O -(2,3,4,6-tetra- O -acetyl-β- d -glucopyranosyl)pyridine-2-carbaldoxime 8 were obtained. The molecular structure of 7 was established by X-ray diffraction studies.

The reaction of [Cp 2 MoH 2 ] and AgBF 4 with the pseudohalide ligands SCN − , OCN − , CN − and SCF 3 − afforded the complexes [(Cp 2 MoH 2 ) 2 AgSCN] ( 1 ), [(Cp 2 MoH 2 ) 2 AgNCO]·CH 2 Cl 2 ( 2 ), [(Cp 2 MoH 2 ) 2 Ag(C 3 N 3 H 2 O 3 )]·3CH 2 Cl 2 ( 3 ), [(Cp 2 MoH 2 ) 2 Ag] n [(Ag 2 (CN) 3 ) n ] ( 4 ) and [(Cp 2 MoH 2 ) 2 AgSCF 3 ]·CH 2 Cl 2 ( 5 ). 1 , 2 and 5 have a [Cp 2 MoH 2 ]:Ag:ligand stoichiometry of 2:1:1. Complex 3 contains the anion of the ligand (HNCO) 3 , formed by trimerization of HNCO. The three-dimensional structure of 4 is built up of polymeric [Ag 2 (CN) 3 − ] n strings and [(Cp 2 MoH 2 ) 2 Ag] + units. The compounds 1 – 5 were characterized analytically and spectroscopically. All the structures were determined by single crystal X-ray analysis.

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.

The reaction of K 3 AsS 3 with [Cp # Co(CO)I 2 ] (Cp # =Cp* (C 5 Me 5 ) or Cp x (C 5 Me 4 Et)) in DMF at 120°C gave violet [Cp # 2 Co 2 As 2 S 3 ] 1 # , dark brown [Cp # 3 Co 3 AsS 6 ]I 2 # , and dark brown [Cp # 3 Co 3 AsS 5 ]I 3 # . Whereas compounds 1 # are already known, 2 # and 3 # were characterized by IR, 1 H-NMR and mass spectra. A crystal structure determination of 3 (Cp) x reveals a salt-like character with [Cp x 3 Co 3 AsS 5 ] + cations and iodide in a 1:1 ratio. In the cation the three Co atoms are connected by a μ 3 -S and a μ 3 -AsS 4 ligand, thus forming a distorted Co 3 AsS 4 -cube. An additional sulfur atom is inserted into one of the As–S edges. The reaction of [Cp # 2 Co 2 I 4 ] with K 2 As 4 Se 6 in DMF at 120°C gave the brown salts [Cp # 3 Co 3 AsSe 5 ]I 5 # . For characterization, compound 5 (Cp x ) was reacted with [Cr(CO) 5 THF]. An X-ray diffraction analysis of the resulting [Cp x 3 Co 3 AsSe 5 ][Cr(CO) 5 I] 8 (Cp x ) reveals a molecular structure similar to that of 3 (Cp) x , but with a [Cr(CO) 5 I] − anion. In the cation all sulfur atoms are replaced by Se atoms.

The reaction of [Cp*Mo(CO)3Cl] (Cp*=C5Me5) with K3AsS3 has been investigated under different conditions. At 56°C, the already known compounds [Cp*2Mo2S4] (2), [Cp*2Mo2As2S3] (3), and [Cp*2Mo2S4H2] (4) are formed along with [Cp*2Mo2(CO)2As2S4] (5). Reaction at 120°C only gives 2 and 3. Complex 5 was characterized by means of its bisadduct [{Cp*2Mo2(CO)2As2S4}·2Cr(CO)5] (6). An X-ray crystallographic study of 6 reveals the presence of two novel AsS2 ligands, bridging in a pseudoallylic manner two Mo atoms. The Cr(CO)5 fragments are coordinated to both the outer sulfur atoms. Thus, each AsS2 ligand in 6 acts as a seven-electron ligand.

Base degradation of the prochiral 1-diphenylphosphanyl-2-phenyl-1,2-dicarba-closo-dodecaborane (1) affords the planar-chiral 7-diphenylphosphanyl-8-phenyl-7,8-dicarba-nido-undecaborate anion (2). Resolution of the racemic anion carried out using a well-established procedure, gave the internally diastereomeric palladium complexes 3R-R and 3R-S. These complexes were separated by fractional crystallization. A single-crystal X-ray analysis of 3R-R established the exo-nido bonding of the carborane ligand via the phosphorus atom and the adjacent BH group, and the (R) configuration of the carborane ligand. The enantiomerically pure anions of 2 were liberated from the diastereomerically pure palladium complexes 3R-R and 3R-S, respectively, by subsequent addition of HCl and NaCN. The exo-nido-rhodium−carborane complexes 4−8 were prepared by heating 2eR or 2eS with [Rh(COD)Cl]2 and/or a chiral chelating phosphane, such as DIOP and BINAP, under reflux. The chiral complexes were tested under enantioselective catalysis conditions such as hydrogenation of acetamidocinnamic acid, hydrogenation of ketopantolactone, and hydrosilylation of acetophenone.

Reaction of [Cp′2NbTe2H] (1) (Cp′ = η5-tBuC5H4) with [W(CO)6] in decane at 140 °C gives red [{(Cp′2Nb)2WTe4}⋅W(CO)4] (2), whereas in the reaction of 1 with [Cr(CO)6] green-black [Cp′4Nb2Te2] (3) is formed. The crystal structures of 2 and 3 have been determined. The structure of 2 contains a slightly distorted WTe4 tetrahedron to which two niobocene fragments and one W(CO)4 group are coordinated. The crystal structure determination of 3 reveals the presence of two Cp′2Nb units bridged by two Te atoms. Complex 2 represents the first example of an organometallic derivative of the unknown WTe42− anion.

The stereoselective synthesis of highly functionalized 1,2,3-trisubstituted cyclopropanes 1 and 2, starting from readily available furans 3 or N-protected pyrrole 4, is described. Furthermore, exceptionally high diastereocontrol in agreement with the Felkin-Anh model was observed for the addition of nucleophiles to the title compounds.

The optically active bidentate Schiff base ligands (+)-2-N-[(S)-1-phenylethyl]pyrrolcarbaldimine NN*H and (+)-N-[(S)-1-phenylethyl]salicylaldimine ON*H react with [Cp*MCl2]2 (M=Rh, Ir) to give the half-sandwich complexes Cp*Rh(NN*)Cl (1), Cp*Ir(NN*)Cl (2), Cp*Rh(ON*)Cl (3) and Cp*Ir(ON*)Cl (4). In all four cases two diastereomers (RM,SC) and (SM,SC) arise, differing only in the metal configuration. However, in each of the systems 1–4, only the (RM,SC) diastereomer crystallized. X-ray structure analyses established the absolute configuration in the crystals of all four complexes. In solution the compounds epimerize via a change of the metal configuration and approach equilibria (RM,SC) (SM,SC) in which for 1 and 2 the (SM,SC) diastereomers dominate. Time dependent integration of 1H NMR signals of the complexes 1 and 2 revealed that the epimerization is a clean first-order reaction. The half-lives in CD2Cl2 solution at −50°C were 19.4 min for 1 and 30.6 min for 2. From the temperature dependence ΔH≠ was determined as 62.4 kJ mol−1 for 1 and 44.3 kJ mol−1 for 2 and ΔS≠ as 148 J K−1 mol−1 for 1 and 65 J K−1 mol−1 for 2. For the compounds 3 and 4, the kinetic data for the epimerization with respect to the metal center were derived from 1H NMR coalescence experiments: half lives 35 ms for 3 at 21±3° (CH2Cl2 solution) and 58 ms for 4 at −1.8±3°C (CHCl3 solution). These epimerization studies show that the metal configuration is labile in complexes 1 and 2 and extremely labile in complexes 3 and 4.

The phosphorus(III)-bridged [1]ferrocenophanes 1,1′-ferrocenediylphenylphosphine ( 1 ), (−)-1,1′-ferrocenediylmenthylphosphine ( 2 ) and (−)-bornyl-1,1′-ferrocenediylphosphine ( 3 ) have been synthesized via the reaction of 1,1′-dilithioferrocene (TMEDA adduct) and Cl 2 PR (R=Ph, Men, Bor). Compounds 1 and 2 have been used as ligands in the preparation of the complexes Cp*Mn(CO) 2 [Fe(η 5 -C 5 H 4 ) 2 PPh] ( 4 ) and (−)- trans -PdCl 2 [Fe(η 5 -C 5 H 4 ) 2 PMen] 2 ( 5 ). The new compounds 2 – 5 were characterized by multinuclear NMR, by MS, and 2 , 4 and 5 by single-crystal X-ray diffraction. Remarkably, the cyclic dimer anti - exo,exo -1,12-dimenthyl-1,12-diphospha[1.1]ferrocenophane ( 6 ) could be isolated and structurally characterized. The thermal ring-opening polymerization of 1 , 2 and 3 yielded the poly(ferrocenediylphosphines) 7 , 8 and 9 . Compounds 2 and 8 were used as chiral ligands in the Rh-catalyzed diastereoselective hydrogenation of folic acid.

The reaction of [Cp#2NbTe2H] (1#; Cp# = Cp* (C5Me5) or Cp(x) (C5Me4Et)) with two equivalents of [Co2(CO)8] gives a series of cobalt carbonyl telluride clusters that contain different types of niobocene carbonyl fragments. At 0 degrees C, [Cp#2NbTe2CO3(CO)7] (2#) and [Co4Te2(CO)10] (3) are formed which disappear at higher temperatures: in boiling toluene a mixture of [cat2][Co9Te6(CO)8] (5#) (cat= [Cp#2Nb(CO)2]+) and [cat2][Co11Te7(CO)10] (6#) is formed along with [cat][Co(CO)4] (4#). Complexes 6# transform into [cat][Co11Te7(CO)10] (7#) upon interaction with HPF6 or wet SiO2. The molecular structures of 2(Cp(x)), 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) have been determined by X-ray crystallography. The structure of the neutral 2(Cp(x)) consists of a [Co3(CO)6Te2] bipyramid which is connected to a [(C5Me4Et)2Nb(CO)] fragment through a mu4-Te bridge. The ionic structures of 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) each contain one (4, 7) or two (5, 6) [Cp#2Nb(CO)2]+ cations. Apart from 4, the anionic counterparts each contain an interstitial Co atom and are hexacapped cubic cluster anions [Co9Te6(CO)8]2- (5) or heptacapped pentagonal prismatic cluster anions [Co11Te7(CO)10]n- (n=2: [6]2- , n=1: [7]-), respectively. Electrochemical studies established a reversible electron transfer between the anionic clusters [Co11,Te7(CO)10]- and [Co11Te7(CO)10]2in 6# and 7# and provided evidence for the existence of species containing [Co11Te7(CO),0] and [Co11Te7(CO)0]3-. The electronic structures of the new clusters and their relative stabilities are examined by means of DFT calculations.

Imines of salicylaldehyde and 2,6-diformyl-p-cresol have been used as ligands in palladium (II) complexes. Enantiomerically pure ligands give enantiomerically pure complexes, racemic ligands give racemates and meso-forms. Differences between the respective isomers of the ligands within the complexes and between the diastereomers of the complexes were investigated. Crystal structure analyses established the trans configuration at the metal center.

In the crystals of [Ca(H2O)5][Cr(Ida)2]2·4H2O (triclinic symmetry, a = 10.1056(10) A, b = 13.0077(11) A, c = 13.1185(13) A, α = 70.186(11)°, β = 81.248(11)°, γ = 78.996(11)°, Z = 2, space group P\( \bar 1 \)) cyclic centrosymmetric tetramers are present. In them calcium ions are bonded to oxygen atoms of the carboxyl groups of two octahedral complex cis(N)-[Cr(Ida)2]− ions (Ida is the iminodiacetic acid anion). The O atoms of five water molecules complete the Ca atom environment to a distorted pentagonal bipyramid. Isolated [Cr(Ida)2]− ions of a similar structure neutralize the positive charge of tetramers.

Ionic [areneFeCp]+ fragments were used as electron acceptors in combination with dimethylamino or pyridoneiminyl donors to form push–pull substituted chromophores. While a tolane derivative showed high second-order non-linear optical activity (measured by hyper-Rayleigh scattering), an analogous pyridoneimine derivative did not. With the help of an X-ray crystal structure analysis this discrepancy was traced back to a cyanine-like structure of the imine. Semiempirical INDO/S calculations support this conclusion.

New expanded bisphosphane ligands with a chiral trans-1,2-substituted cyclopentane skeleton were prepared. Polyaldehydes were accessible by coupling optically active bisphosphane precursors with branched aryl bromides. Optically active expanded ligands were obtained by condensation of the aldehydes with chiral amines and amino alcohols. The optically active ligands were tested in several model reactions of enantioselective catalysis, including allylic alkylation, hydrogenation (adopted to the use of water), and hydrosilylation.

Ethynyltributyltin undergoes inverse type [4+2] cycloadditions with various 1,3,4-oxadiazin-6-ones to afford two regioisomeric stannylated α-pyrones, which can be separated by flash column chromatography. Exposure of the stannanes to elemental halogens in chloroform or THF as solvent yields the corresponding halogeno pyrones. A general exception of this reaction type is also described. Destannylation with dry hydrogen chloride furnishes 3,6-disubstituted α-pyrones.

The absolute configuration has been determined for the title compound, C14H18N2O5S, a bicyclic aromatic building block which can act as a rigid fluorescence marker in peptide backbones. In the crystal packing, the two independent molecules of the asymmetric unit are aligned in an antiparallel manner as dimers which are stabilized by antiparallel inter­molecular N—H⋯O=C hydrogen bonds. In addition, there are weak inter­molecular C—H⋯O inter­actions.

Black single crystals of MnBiSe2I were obtained by the reaction of stoichiometric amounts of Mn, Bi, BiI3, and Se at 600 °C for 7 days. The compound crystallizes in the monoclinic system, space group C2/m, with a = 13.428(2), b = 4.112(1), c = 10.130(2) A, β = 90.97(2)°, and Z = 4. The crystal structure refinement based on 849 reflections converged at R = 0.0380 and wR2 = 0.0916, respectively. MnBiSe2I forms a layer structure consisting of MnSe6 octahedra, MnSe2I4 octahedra, and BiSe3+2 pyramids.

The crystallographic data, NMR and UV-VIS spectra and luminescence of the heteroleptic complexes [Ru(L)(bpy)2](PF6)2 (L = 5-aryl-6-cyano-2,2’-bipyridine) are described.

Phase-pure FeP nanoparticles (NPs) have been synthesized through low temperature thermolysis of the single source precursor [(CO)4Fe(PH3)]. Examination of the mechanism demonstrates the central role of the labile CO ligands and the weak P-H bonds to yield stoichiometry controlled FeP materials.

The metalation of tri(tert-butyl)silylphosphane with diethylzinc yields quantitatively the title compound tetraethyltetrakis(tri(tert-butyl)silylphosphanediido)hexazinc (1) with a novel Zn6P4 cage with two Zn2P2 rings interconnected by two zinc atoms.

In contrast to bidentate ligands, e.g. PN, the tripod ligands CpPN- predetermine a single metal configuration, preventing formation of the opposite metal configuration.