Kurt Mereiter

The substitution chemistry of RuCp* (temeda)Cl

SummaryHalide abstraction from RuCp*(tmeda)Cl (1,tmeda=Me2NCH2CH2NMe2) with NaBPh4 in CH2Cl2 leads to the formation of the sandwich complex RuCp*(η6-C6H5BPh3) (2). In the presence of CH3CN (1 equiv.) and CO, however, the cationic complexes [RuCp*(tmeda)(CH3CN)]+ (3) and [RuCp*(temeda)(CO)]+ (5) are obtained. In CH3CN,tmeda is also replaced giving [RuCp*(CH3CN)3]+ (4). Complex1 reacts readily with terminal acetylenes HC≡CR, the products depending on the nature ofR (Ph, SiMe3,n-Bu, COOEt). Thus, withR=Ph the ruthenacyclopentatriene complex RuCp*(σ,σ′-C4Ph2H2)Cl (6), withR=SiMe3 the cyclobutadiene complex Ru(Cp*)(σ4-C4H2(1,2-SiMe3)2)Cl (7), and withR=n-Bu and COOEt the binuclear complexes (Cp*)RuCl2(η2:η4-μ2-C4H2(1,3-R)2)Ru(Cp*) (8,9) are obtained. Furthermore, with diethyl maleate in the presence of 1 equiv. of LiCl,1 transforms into the new anionic complex Li[Ru(Cp*) (η2-C2H2(COOEt)2)Cl2] (10). X-ray structures of2,3,4,7, and10 are included.ZusammenfassungChloridabspaltung von RuCp*(tmeda)Cl (1,tmeda=Me2NCH2CH2NMe2) mittels NaBPh4 in CH2Cl2 führt zur Bildung des Halbsandwich-Komplexes RuCp*(η6-C6H5BPh3) (2), während in Gegenwart von CH3CN oder CO die beiden kationischen Verbindungen [RuCp*(tmeda)(CH3CN)]+ (3) und [RuCp*(tmeda)(CO)]+ (5) entstehen. In CH3CN als Lösungsmittel wird sogartmeda unter Bildung von [RuCp*(CH3CN)3]+ (4) verdrängt. Komplex1 reagiert sehr leicht mit terminalen Alkinen HC≡CR, wobei die Produkte stark von der Natur des SubstituentenR (Ph, SiMe3,n-Bu, COOEt) abhängen. Im Fall vonR=Ph entsteht der Ruthenacyclopentatrien-Komplex RuCp*(σσ′-C4Ph2H2)Cl (6), mitR=SiMe3 der Cyclobutadien-Komplex Ru(Cp*)(η4-C4H2(1,2-SiMe3)2)Cl (7), und im Fall vonR=n-Bu und COOEt bilden sich die binuklearen Komplexe (Cp*)RuCl2(η2:η4-μ2-C4H2(1,3-R)2)Ru(Cp*) (8,9). Überdies reagiert1 mit Maleinsäurediethylester in Gegenwart von LiCl zum neuen anionischen Komplex Li[Ru(Cp*) (η2-C2H2(COOEt)2)Cl2] (10). Von2,3,4,7 und10 wurden die Kristallstrukturen bestimmt.

Rh(acac)(CO)(PR 3 ) and Rh(oxinate)(CO)(PR 3 ) complexes—substitution chemistry and structural aspects

The substitution of CO in Rh(acac)(CO) 2 by the phosphorus ligands P(OPh) 3 , P(NC 4 H 4 ) 3 , and PPh 2 (NC 4 H 4 ) has been studied kinetically by stopped-flow spectrophotometry as a function of temperature. With P(OPh) 3 and P(NC 4 H 4 ) 3 , both CO ligands are replaced in a stepwise fashion via the intermediate Rh(acac)(CO)(PR 3 ). However, the disubstituted complexes Rh(acac)(PR 3 ) 2 are thermodynamically unstable. Judged from the activation parameters, the individual steps are associative processes. In the case of PPh 2 (NC 4 H 4 ) only the monosubstituted complex is formed. The differences in the substitution rates as well as the stability of the various products are largely dominated by electronic (e.g. basicity) effects. X-ray structures of some of the mono-substituted complexes are given. In addition, also the reaction of Rh(oxinate)(CO) 2 with P(OPh) 3 has been studied kinetically showing that oxinate has a labilizing effect relative to acetylacetonate

SCOPE AND LIMITATIONS OF THE T-REACTION EMPLOYING SOME FUNCTIONALIZED C-H-ACIDS AND NATURALLY OCCURRING SECONDARY AMINES

Scope and limitations of the T-reaction with emphasis on using chiral, natural products as starting materials to prepare novel chiral heterocycles is studied and the diastereoselective introduction of newly formed stereocenters is explained via proposed mechanisms.

Platinum complexes of heteroannularly bridged heterobidentate ferrocenyl diphosphine ligands: their molecular structure and their use in catalytic carbonylation reactions

Abstract Platinum complexes PtCl2(L) and PtCl(SnCl3)(L) of the ferrocenyl diphosphine ligands (L) (R,R)-1-diphenylphosphino-2,1′-[(1-diphenylphosphino)-1,3-propanediyl]-ferrocene (1), (R,R)-1-diphenylphosphino-2,1′-[(1-dicyclohexylphosphino)-1,3-propanediyl]-ferrocene (2), (R,R)-1-bis(4-fluorophenyl)phosphino-2,1′-[(1-diphenylphosphino)-1,3-propanediyl]-ferrocene (3), have been synthesised. Complexes PtCl2(1) and PtCl2(2) have been structurally characterised by X-ray diffraction. Both the ‘preformed’ and the in situ catalysts have been used in hydroformylations of styrene. At low temperature (below 70°C) and with use of the platinum catalysts the prevailing formation of (R)-2-phenyl-propanal was observed, while at higher temperatures the formation of the (S)-enantiomer was favoured. The palladium catalysts proved to be rather inactive in the hydromethoxycarbonylation of styrene. In the presence of ligand 2 the predominant formation of the linear regioisomer was observed.

Synthesis of a new class of chiral aminoalcohols and their application in the enantioselective addition of diethylzinc to aldehydes

Five new aminoalcohols containing a 2,2′-bridged binaphthyl entity were synthesised and applied as auxiliaries in the enantioselective addition of Et 2 Zn to ten aldehydes. While reactivities were generally high and low concentrations of aminoalcohols were found sufficient to achieve complete conversions (<1 mol%), the observed enantioselectivities were highly dependent upon auxiliary and substrate structure. Up to 97% e.e.s have been observed in the case of aromatic substrates but significantly lower degrees of asymmetric induction were found for aliphatic substrates (up to ca. 60% e.e.). Suggestions concerning the structure of the transition states based on molecular mechanics calculations are presented to rationalise different enantiocontrol.

Synthesis and reactivity of Ru(II) complexes containing the phosphino-amine Ph2PCH2CH2NMe2

Abstract RuCl 3 · 3H 2 O reacts with 2 equiv. of Ph 2 PCH 2 CH 2 NMe 2 in the presence of Zn to the neutral complex Ru( κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 ) 2 Cl 2 ( 1 ). Alternatively, 1 is also obtained by the reaction of RuCl 2 (PPh 3 ) 3 with 2 equiv. of Ph 2 PCH 2 CH 2 NMe 2 . Compound 1 crystallizes in the space group P 2 1 (No. 4) with a = 11.009(3), b = 11.007(4), c = 16.999(4) A , β = 106.22(2)° and Z = 2. The hemilabile nature of the Ph 2 PCH 2 CH 2 NMe 2 ligand in 1 is revealed by the reaction with CO and HC  CPh affording complexes Ru( κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 )-( κ 1 (P)-Ph 2 CH 2 NMe 2 )(Cl 2 (CO) ( 2 ) and Ru( κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 )( κ 1 (P)-Ph 2 PCH 2 CH 2 NMe 2 )(Cl) 2 (CCHPh) ( 3 ). Halide abstraction from 1 with NaBPh 4 affords the five-coordinate cationic complex [ Ru (κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 ) 2 Cl ] ′ [ BPh 4 ] ( 4 ) which crystallizes in the space group Pbca (No. 61) with a = 21.806(4), b = 19.683(4), c = 26.405(5) A , and Z = 8. Compound 4 reacts readily with CH 3 CN, CO and HC  CR (R  Ph, SiMe 3 , n-Bu) to give the cationic complexes [Ru( κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 ) 2 (Cl)(CCHR)] ( 5 ), [Ru( κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 ) 2 (Cl)(CCHR)] ( 7–9 ). Compound [Ru( κ 2 (P,N)-Ph 2 PCH 2 CH 2 NMe 2 ) 2 (Cl)(CO)] ′ [BPh 4 ] ( 6a ) one of the two stereosiomers 6a and 6b crystallizes in the space group P l (No. 2) with a = 11.637(3), b = 15.012(3), c = 15.306(3) A , α = 96.34(1), β = 98.32(1), γ = 98.731(1)° and Z = 2 and the isomeric compound 6b crystallizes in the space group P 2 1 c (No. 14) with a = 20.445(2), b = 14.198)2), c = 19.717(2), A , β = 94.66(1)° and Z = 4, 1 catalyzes the dimerization of HC  CPh to Z - and E -butenynes.

Oxidative addition of O2, Cl2, NO, NO+ and H2 to [Ru(ν5-C5Me5) (Ph2PCH2CH2PPh2)]+ : X-ray structures of [Ru(C1)2(ν5-C5Me5)(Ph2PCH2CH2PPh2]+ and [Ru(NO)(ν5-C5Me5)(Ph2PCH2CH2PPh2]2+

Treatment of Ru(ν5-C5Me5) (dppe)Cl (1) (dppe = Ph2PCH2CH2PPh2) with Ag+ (as the PF6− or CF3SO3− salt) in CH3NO2 as the solvent yields the 16-electron complex [Ru(ν5-C5Me5 (dppe]+ (2) in quantitative yield. Complex 2 reacts with O2, Cl2, NO, NO+ and H2 to form the cationic Ru(IV) complexes [Ru(ν5-C5Me5) dppe)]+ (3), [Ru(Cl)2(η5-C5Me5)(dppe)]+ (4), [Ru(NO) (η5-C5Me5) (dppe)]2+ (5) and [Ru(H)2(η5-C5Me5)(dppe)]+ (6) in good yields. The crystal structures of 4b (CF3SO3− salt) and 5b (CF3SO3− salt) have been determined by X-ray diffraction techniques. 4b crystallizes in the triclinic space group P1 (No. 2), with a=12.215(4), b=12.593(5), c=14.422(4) A, α=76.45(2), β=79.83(2), gg=84.64(2)°, V=2119.7(12) A3, Z=2. The structure was refined to R(F)=0.0418 (F≥4σF). 5b crystallizes in the monoclinic space group P21/n, with a=12.679(4), b=12.269(5), c=27.658(9) A, β=90.36(1)°, V=4302(3) A3, Z=4. The structure was refined to R(F)=0.0511 (F≥4σF).

Chiral auxiliaries as docking/protecting groups: biohydroxylation of selected ketones with Beauveria bassiana ATCC 7159

Abstract The concept of chiral docking/protecting groups for biohydroxylation was extended from cyclopentanone to other ketones. Reaction of cyclohexanone, (R)-3-methylcyclohexanone, cycloheptanone, 5-methyl-2-hexanone and 4-methyl-2-pentanone with (R)-2-amino-1-propanol and subsequent in situ benzoylation afforded the corresponding N-benzoylated oxazolidine derivatives. All substrates were hydroxylated with the fungus Beauveria bassiana ATCC 7159, one of which was diastereoselectively hydroxylated with a d.e. of 99%. In this manner, access to the corresponding hydroxylated ketones was provided.

Structure and bonding in a series of cyano complexes: RuCp(PPh3) 2CN, [RuCp(PPh3) 2(CNH)]CF3SO3, and H-bridged [Ru2(Cp) 2(PPh3) 4CNHNC]CF3SO3

Abstract The three title cyanoruthenium complexes have been characterized by means of X-ray diffraction analysis, IR and NMR solution spectroscopies, as well as extended Huckel molecular orbital calculations examining the properties of the cyanide fragment changing with complexation and with the co-ligands Cp and PPh3. Explanations are given for crystallographic results of the C-N bond shortening upon complexation, the supershort (2.573 A) bond length of N(H) ⋯ N in the bridged complex, as well as the Ru-C-N and C-N-H-N-C bendings. Although the crystallographically found asymmetry of coordinated Cp is not significant, the MO calculations suggest a distorted endocyclic bond-length pattern indicative of the relative importance of σ and π bonding in the metalcyclopentadienyl interactions.

Guanylhydrazones of (Hetero)Aryl Methyl Ketones: Structure and Reaction with Acetic Anhydride

Summary. The synthesis of some novel guanylhydrazones of (hetero)aryl methyl ketones is described. Successive reaction with hot acetic anhydride leads to the corresponding N,N′-diacetyl derivatives. Structural assignments of all novel compounds and those of some already known congeners were achieved by means of NMR spectroscopic investigations (1H, 13C) and X-ray structure analysis.Zusammenfassung. Die Synthese einiger neuer Guanylhydrazone von Aryl-bzw. Heteroarylmethylketonen wird beschrieben. Die Reaktion dieser Verbindungen mit Acetanhydrid führt zu entsprechenden N,N′-Diacetylderivaten. Die Strukturen aller neuen Verbindungen sowie die einiger bereits beschriebener Analoga wurden mit Hilfe von NMR-Untersuchungen (1H, 13C) sowie durch Röntgenkristallstrukturanalysen bestimmt.