Günter Liehr

Reactivity towards dioxygen of a copper(I) complex of tris(2-benzylaminoethyl)amine

Abstract The reaction of dioxygen with the copper(I) Bz 3 tren complex (Bz 3 tren=tris(2-benzylaminoethyl)amine) complex has been investigated using low temperature stopped-flow techniques. The formation of a superoxo as well as a peroxo complex as intermediates was detected spectroscopically. The copper(II) complexes [Cu(Bz 3 tren)H 2 O](ClO 4 ) 2 and [Cu(Bz 3 tren)Cl]Cl were synthesized and structurally characterized. Both complexes react with dioxygen in solution and formation of benzaldehyde was observed.

The reactivity of N-coordinated amides in metallopeptide frameworks: molecular events in metal-induced pathogenic pathways?

The amino acid derived tertiary amide ligand tert-butoxycarbonyl-(S)-alanine-N,N-bis(picolyl)amide (Boc-(S)-Ala-bpa, 1) has been synthesized as a model for metal-coordinating peptide frameworks. Its reactions with copper(II) and cadmium(II) salts have been studied. Binding of Cu2+ results in amide bond cleavage and formation of [(bpa)(solvent)Cu]2+ complexes. In contrast, the stable, eight-coordinate complex [(Boc-(S)-Ala-bpa)Cd(NO3)2] (5) has been isolated and characterized by X-ray crystallography. An unusual tertiary amide nitrogen coordination is observed in 5; this gives rise to significantly reduced cis-trans isomerization barriers. Possible implications for metal-induced conformational changes in proteins are discussed.

Chemie polyfunktioneller moleküle: LXXIX. Kristall- und molekülstruktur von μ,-carbonyl-μ-chloro-di[μ,-bis(diphenylphosphino)-amin-p,P′]-bis[carbonyl-rhodium(I)]chlorid-methanol (1/1)☆

Abstract The molecular and crystal structure of the compound [Rh2(μ-CO)(μ-Cl)(μ-Ph2PNHPPh2)2(CO)2]Cl·CH3OH (1/1) (II) have been investigated in order to obtain confirmation of the complicated hydrogen bridge linkage system, deduced earlier from vibrational spectroscopy. Crystals of II are triclinic, space group P 1 , with a 1680.6(1.1), b 1380.6(5), c 1190.5(1.1) pm, α 96.30(3), γ 96.00(7), γ 110.75(3)° and Z = 2. On the basis of 3258 unique reflections, the structure was refined by blocked matrix least-squares techniques to a conventional R value of 0.064. The two rhodium atoms of the cation are bridged by two nearly transoid PNP ligands. In the equatorial plane, which is not exactly perpendicular to the waved bridging ligand planes, the two metals are slightly asymmetrically bridged by a Cl and a CO ligand. A terminal CO group on each metal, one nearly colinear with the single RhRh bond (273.7 pm), the other at an angle to die metal-metal distance, completes the rhodium coordination. The geometry of the rhodium atoms can be described as a significant distorted bipyramid. The cations of II are connected together to infinite chains along the b-axis of the crystal by strong hydrogen-bridging bond systems.

Kinetics and mechanism of the reaction of chelated Pd(II) complexes with thiols in acidic aqueous solution. Synthesis and crystal structure of [Pd(bpma)Cl]Cl·H2O (bpma = bis(2-pyridylmethyl)amine)

The kinetics of the complex-formation reactions between monofunctional palladium(II) complexes [Pd(N–N–N)H2O]2+, where N–N–N is 2,2′:6′,2″-terpyridine (terpy), diethylenetriamine (dien) or bis(2-pyridylmethyl)amine (bpma), with L-cysteine, DL-penicillamine and glutathione, have been studied in an aqueous 0.10 M perchloric acid medium using variable-temperature and -pressure stopped-flow spectrophotometry. Second-order rate constants, k1298, varied between 2.8 × 102 and 4.4 × 104 M−1 s−1. The highest reactivity was observed for the [Pd(terpy)H2O]2+ complex, whereas glutathione is the strongest nucleophile. Activation volumes for these reactions varied between −5.6 ± 0.3 and −10.7 ± 1.0 cm3 mol−1. The negative entropies and volumes of activation support a strong contribution from bond making in the transition state of the substitution process. The crystal structure of [Pd(bpma)Cl]Cl·H2O has been determined by X-ray diffraction at 190 K. Crystals are triclinic with space group P and consist of distorted square-planar [Pd(bpma)Cl]+ cations. The Pd–N distances are all equal to 2.005(7) A. The Pd–Cl distance is 2.305(3) A.

Syntheses, Structures and Properties of Copper(I) and Copper(II) Complexes of the Ligand N,N′-Bis[2′-(dimethylamino)ethyl]-N,N′-dimethylethane1,2-diamine (Me6trien)

Copper(I) and copper(II) complexes of the ligand N,N′-bis[2′(dimethylamino)ethyl]-N,N′-dimethylethane-1,2-diamine (Me6trien) were synthesized and structurally characterized. In the solid state the complex cation [Cu(Me6trien)]+ (1) adopts a distorted tetrahedral configuration. Crystallography, EPR measurements, and UV/Vis spectroscopy indicate that the analogous copper(II) complex [Cu(Me6trien)Cl]+ has a square pyramidal geometry in the solid state as well as in solution. The reaction of 1 with dioxygen was investigated in different solvents. No copper dioxygen intermediates could be detected spectrophotometrically during these reactions.

Kinetics and mechanism of the reactions of [Pt(terpy)H2O]2+ with thiols in acidic aqueous solution. Synthesis and crystal structure of [Pt(terpy)(tu)](ClO4)2 (tu = thiourea)

The kinetics of the complex-formation reactions between [Pt(terpy)H2O]2+, where terpy is 2,2′:6′,2″-terpyridine, with L-cysteine, DL-penicillamine, glutathione and thiourea (tu) were studied in an aqueous 0.10 M perchloric acid medium using variable-temperature and -pressure stopped-flow spectrophotometry. Thiourea is the best nucleophile with a second order rate constant, k1298, of 1.72 × 105 M−1 s−1, whereas glutathione is the strongest nucleophile of the studied thiols, for which k1298 varied between 38 and 583 M−1 s−1. Activation volumes for the reactions with thiourea, L-cysteine, glutathione and DL-penicillamine, are −6.0 ± 0.3, −9.3 ± 0.4, −12.4 ± 0.6 and −20.6 ± 1.0 cm3 mol−1, respectively. The negative entropies and volumes of activation support a strong contribution from bond making in the transition state of the substitution process. The crystal structure of [Pt(terpy)(tu)](ClO4)2 was determined by X-ray diffraction. Crystals are monoclinic with the space group P21/c and consist of the distorted square-planar [Pt(terpy)(tu)]2+ complex. The Pt–N (central) bond distance, 1.971(14), is shorter than the other two Pt–N distances, 2.078(15) and 2.045(15) A. The Pt–S distance is 2.301(5) A.

Synthesis, Structures, and Redox Properties of Copper Complexes with Chiral and Achiral Amino Acid Derived Ligands

A series of copper(II) complexes containing the amino acid derived ligands bpaAc-Gly-OEt {1; [bis(picolyl)amino]acylglycine ethyl ester} and bpaAc-Phe-OMe {2; [bis(picolyl)amino]acylphenylalanine methyl ester} were synthesized and characterized in solution and in the solid state. This was done in order to evaluate the relevance of weak aromatic interactions between a metal center and amino acid side chains in square-pyramidal or octahedral coordination environments. The results showed that the structural, spectroscopic, and electrochemical properties of the copper(II) center are not affected by the amino acid side chain structure. This is in remarkable contrast to our previous investigations on zinc(II) complexes of the same ligands, which indicate close association of the metal center and the phenyl substituent of 2 in a trigonal-bipyramidal environment. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Metallomethane, VI [1]. Kristallstruktur von Tetrakis(chloroquecksilber)methan-Dimethylsulfoxid C(HgCl)4 · (CH3)2SO / Metallomethanes, VI [1]. Crystal Structure of Tetrakis(chloromercuri)methane-Dimethylsulfoxide C(HgCl)4 · (CH3)2SO

The tetrakis (halomercuri) methane dimethylsulfoxide solvates C(HgX)4 · DMSO (X = Cl and Br) have been prepared. - The crystal structure of the chloro compound C(HgCl)4 · DMSO has been determined (R = 0.0611 and Rw = 0.0562). The compound crystallizes in space-group P21/n with a = 1854(1) pm, b = 727.3(5) pm, c = 1049.1(6) pm, β = 94.82(3)°, Z = 4; dc = 4.873 g·cm-3, d0 = 4.51 g-cm-3. - The C(HgCl)4 molecules have C-Hg bond lengths in the range 201.4(26) to 209.9(27) pm (average 207.0 pm), and Hg-Cl bonds between 231.4(9) and 234.2(9) pm (average 233.2 pm). The bond angles Hg-C-Hg vary from 107.3(3) to 111.7(4)° (average 109.5°), and the angles C-Hg-Cl are found within the limits 172.2(24) and 178.3(25)° (mean 174.3°). DMSO molecules (S-O bond 148.6(23)pm) are coordinated via oxygen to two Hg atoms of one C(HgCl)4 molecule and to one Hg atom of a neighbouring C(HgCl)4 molecule forming two bifurcated bridges in a dimer [C(HgCl)4 · DMSO]2; two strong Cl→···Hg and two weak S→···Hg interactions also contribute to this pair formation. The dimeric units are arranged to layers in the planes (100) and (200), such that each C(HgCl)4 molecule has six C(HgCl)4 and two DMSO molecules as neighbours; with two C(HgCl)4 molecules from each adjacent layer, each C(HgCl)4 molecule achieves a total coordination number of ten. Depending on the van der Waals radius assumed for mercury a packing coefficient 0.640 ≤ k ≤ 0.691 is obtained. - Cryoscopy and vibrational spectrometry suggest monomeric, unperturbed tetrahedral C(HgX)4 molecules in DMSO solutions.

Über die Darstellung und Eigenschaften neuer Chloro-tris(carbonylmetaIIato)-zinn(IV)-Komplexe und die Kristallstruktur von ClSn[Fe(CO)2Cp]2[Co(CO)4]. Synthesis and Properties of New Chloro Tris(carbonylmetalato) Tin(IV) Complexes and the X-ray Structure Analysis of ClSn[Fe(CO)2Cp]2[Co(CO)4]

The chloro-tris(carbonylmetalato)tin(IV) compounds, listed in Table I, are obtained by the reaction of TlCo(CO)4 or Tl[Mn(CO)5]3 with the dichloro(carbonylmetalato)tin(IV) complexes Cl2Sn[M(CO)5]2 (M = Mn, Re), Cl2Sn[Fe(CO)2Cp]2, Cl2Sn[Cr(CO)3Cp][Mn(CO)5] and Cl2Sn[Cr(CO)3Cp][Fe(CO)2Cp] in the molar ratio 1:1. Chloro-tris(carbonylmetalato)- tin(TV) compounds of the same type are also formed by treatment of TlCo(CO)4 with the trichloro(carbonylmetalato)tin(IV) complexes in the molar ratio 2 : 1. The new compounds are characterized by their analyses, mass, IR and FIR spectra. The X-ray analysis of ClSn[Fe(CO)2Cp]2[Co(CO)4] (space group P21/c) confirms the presence of 3 carbonyl - metalato groups attached to tin.