Wolfgang Beck

Metal complex SERMs (selective oestrogen receptor modulators). The influence of different metal units on breast cancer cell antiproliferative effects.

The selective oestrogen receptor modulator tamoxifen is a leading agent in the adjuvant treatment of breast cancer. Several organometallic moieties have been vectorised with tamoxifen, in order to improve on the latters antiproliferative properties by the addition of a potentially cytotoxic moiety, and have been evaluated versus both oestrogen receptor positive (MCF7) and oestrogen receptor negative (MDA-MB231) breast cancer cells. For tamoxifen analogues with ((R,R)-trans-1,2-diaminocyclohexane)platinum(II), cyclopentadienyl rhenium tricarbonyl, and ruthenocene tethers, there was no enhancement of the antiproliferative effect on oestrogen receptor positive cells, nor any cytotoxic effect on oestrogen receptor negative cells, while those containing cyclopentadienyl titanium dichloride showed an oestrogenic effect. However, compounds where ferrocene replaces tamoxifens phenyl ring were strongly cytotoxic against both cell lines. The synthesis and biological results of these compounds is reviewed and placed in the historic context of inorganic compounds in therapy.

Transformation behaviour of different platinum compounds in a clay-like humic soil: speciation investigations

Synthetic platinum compounds with different oxidation stages and a platinum containing tunnel dust, used as a natural sample, were added to a clay-like humic soil. Possible chemical and physical interactions with the soil were investigated. Oxidation of finely dispersed metallic platinum in the soil was studied by eluting platinum species with different polar solvents and complexing agents. Due to its ultrafine dispersion and nanocrystalline particle size, the platinum present in the tunnel dust was oxidised in the soil to a higher degree than the model compound platinum black. K2PtCl4 and Na2PtCl6 ∗ 6H2O showed strong adsorption in the soil by recomplexation into almost insoluble species. Differences in the transformation reactions between native and artificial platinum compounds are described.

Biometallorganische Chemie – Übergangsmetallkomplexe mit α‐Aminosäuren und Peptiden

Ein neues interdisziplinares Forschungsgebiet ist die Biometallorganische Chemie; sie befast sich mit der Einfuhrung von metallorganischen Fragmenten in Biomolekule (siehe z. B. Struktur rechts). Die „klassischen” α-Aminosaure- und Peptidliganden haben sich dabei als besonders vielseitig erwiesen und eroffnen unter anderem einen Zugang zu stereochemisch interessanten Verbindungen. α-Aminosauren und Peptide konnen durch metallorganische Verbindungen synthetisiert, markiert, stabilisiert oder aktiviert werden.

Metal complexes of biologically important ligands, LXXXVII α-amino carboxylate complexes of palladium(II), iridium(III) and ruthenium(II) from chloro-bridged ortho-metallated metal compounds and [(OC)3Ru(Cl)(μ-Cl)]2

Abstract The chloro-bridged ortho-metallated compounds [(L)Pd(μ-Cl)] 2 (HL = 2-benzylpyridine, 2-phenylpyridine, azobenzene) and [(L) 2 Ir(μ-Cl)] 2 (LH = 2-phenylpyridine) react with α-amino carboxylase to give the N,O-chelate complexes (L)Pd-t-NH 2 C(H)(R)CO 2 and (L) 2 Ir-NH 2 C(H)(R)CO 2 . The chloro-bridged carbonyl complex [(OC) 3 Ru(Cl)(μ-Cl)] 2 and prolinate afford the N,O-chelate (Cl)(OC) 3 Ru(prolinate). From the osmium complex [(OC) 3 Os(Cl)(μ-Cl)] 2 and N , N -dimethylglycine methylester the ionic compound [HN(Me 2 )CH 2 CO 2 Et] + (Os(CO) 3 Cl 3 ) − ( 25 ) was obtained. The structures of [2-(2-pyridylmethyl)phenyl-C 1 ,N]Pd(prolinate)], [(2-pyridylphenyl-C 1 ,N) 2 Ir(prolinate)] a and of 25 were determined by X-ray diffraction.

Alkyne bridged α- amino acids by palladium mediated coupling of alkynes with N-t-Boc-4-iodo-phenylalanine methyl ester

Abstract The Heck reaction of trimethylsilylacetylene with N-t-Boc-4-iodo-L-phenylalanine methyl ester gives N-t-Boc-4-ethynyl-L-phenylalanine methyl ester (2). Coupling of 2 with different alkynes yields alkyne bridged linear amino acid esters 3– 5. Also tripodal and tetrapodal amino acid esters 10 and 11 were prepared by this approach. All compounds have been obtained in enantiomerically pure form. The protecting groups were removed by standard methods to yield the free amino acids as hydrochlorides.

Reactions of metal carbonyls with the azide anion

Abstract The kinetics of the reaction of metal hexacarbonyls M(CO) 6 (M = Cr, Mo, W) with tetraethylammonium azide in acetone solution have been studied in detail. The ionic reaction products NEt 4 [M(CO) 5 NCO] are formed by an S N 2-type mechanism suggesting a primary, rate-determining attack of the azide anion to the carbon atom of a CO group. The activation energy for this step depends on the metal hexacarbonyl and decreases in order Cr>Mo>W. The preparation of the azido complex [Az(C 6 H 5 ) 4 ] [W(CO) 5 N 3 ] together with some preliminary results on the reactions of other metal carbonyl compounds, e.g. Mn(CO) 5 Br, Re(CO) 5 Cl, CO 2 (CO) 8 and Fe(CO) 5 , with the azide ion are reported.

Metal complexes of biologically important ligands, CXIV ferrocenyl–oxazolones as N and C donors in Pd(II), Pt(II) and Ir(III) complexes and ferrocenoyl–dipeptides ☆

Abstract 2-Ferrocenyl-4R-5(4H)-oxazolones 1–5 were obtained from N-ferrocenoyl-α-amino acids and function as N donors in dichloro–phosphine–palladium(II) and platinum(II) complexes 6–18. The reaction of ferrocenyl–oxazolone and ferrocenyl–bis(oxazolone) with [Cp*IrCl2]2 afforded trimetallic and pentametallic complexes 19 and 20 with a C,N bridging oxazolone. Ring opening of the ferrocenyl–oxazolones 1, 2 and 4 with α-amino acid esters gave N-ferrocenoyl–dipeptide esters 21–26. In the ferrocene bis(dipeptides) the two peptide esters are aligned parallel by hydrogen bonding. The structures of 6 and 19 were determined by X-ray diffraction.

FACILE SYNTHESIS OF CYCLIC TETRAPEPTIDES FROM NONACTIVATED PEPTIDE ESTERS ON METAL CENTERS

The cyclization of dipeptide esters of α-, β-, γ-, and δ-amino acids can be achieved by using NiII , PdII , or CuII templates. The structure of one of the complexes (1) obtained, which was determined by X-ray crystallography, reveals that the anions form layers and are linked to water molecules by hydrogen bonds.

New C-tetrazolato complexes of rhodium(III), palladium(II) and gold(III)

Abstract The azido complexes [RhCp*(μ-N3)(N3)]2 (Cp*=η-C5Me5), trans-Rh(N3)(CO)(PPh3)2, Na2[Pd(N3)4], Na2[Pd2(μ-N3)2(N3)4] and Na[Au(N3)4], prepared in situ from metal halide precursors and a three- to ten-fold excess of NaN3 in water, react with aliphatic isocyanides to give a series of new metal–carbon bonded tetrazolato complexes. All azide ligands in the coordination sphere undergo this cycloaddition with isocyanides except on palladium(II) where only two tetrazol-5-ato groups are formed. In the neutral species HAu(CN4R)4 (R=tBu (2c), Cy (2d)) presumably one of the four tetrazol-5-ato groups has been protonated to afford a tetrazol-5-ylidene (carbene) ligand. The reactivities of the isocyanides decrease in the order CNtBu>CNCy>CN(CH2)4Cl>CN-allyl>CNCH2CO2Na; surprisingly, no reaction occurs with methylisocyanide. With tert-butyl isocyanide in the cold, [Ru(μ-N3)(N3)(η-C10H14)]2 (C10H14:4-isopropyltoluene) only reacts with cleavage of the azido bridges giving rise to [Ru(N3)2(η-C10H14)CNtBu] (5a), while heating of the same mixture affords a second azido-isocyanide complex, trans-[Ru(N3)2(CNtBu)4] (5b), of which an X-ray structure analysis has been carried out. In some cases the reactions proceed with N2 evolution, and rhodium complexes 6a–c are also formed probably containing cyanamido (N{R}CN) or carbodiimido (NCNR) ligands, respectively.

Lewis-saure metallkomplexe : VII. Darstellung und reaktivität von pentacarbonyltetrafluoroboratorhenium: ein trifluorohydroxoborato-komplex, (OC)5ReOHBF3

Abstract (OC) 5 ReFBF 3 (I) is obtained by abstraction of H - or CH 3 - from (OC) 5 ReH or (OC) 5 ReCH 3 , respectively, using Ph 3 CBF 4 . Treatment of I with water vapour yields the trifluorohydroxoborato complex (OC) 5 ReOHBF 3 (III). The reaction of I with σ and π-donors L proceeds to give the salts [(OC) 5 ReL] + BF 4 - (L  (CH 3 ) 2 CO, CH 3 CN, CO, C 2 H 4 , propene, pentene-1) under mild conditions. [(OC) 5 ReC 2 H 4 ] + BF 4 - and Na + [Re(OC) 5 ] - form the ethylene bridged complex (OC) 5 CH 2 CH 2 Re(OC) 5 .