Paule Castan

Platinum and palladium complexes of 3-methyl orotic acid: a route toward palladium complexes with good antitumor activity.

In order to design and develop potential anticancer drugs involving the same structural pattern as platinum(II) antitumor complexes, complexes of palladium and platinum with 3-methyl-orotic acid as the leaving ligand have been synthesized. The study of the anticancer activity of these compounds toward L1210 leukemia and sarcoma 180 in mice is presented and discussed in terms of the nature of the ligand and the metal involved. The (3-methylorotato)(1,2-diamino-cyclohexane) palladium(II) has an activity (sarcoma 180) similar to that for cis-DDP itself. The crystal structure of (3-methylorotato)(dl-trans-1,2-diaminocyclohexane) platinum(II) is described.

Preparation and interconversion of dimeric di-µ-hydroxo and tri-µ-hydroxo complexes of platinum(II) and palladium(II) with 2,2′-bipyridine and 1,10-phenanthroline

Treatment of [Pt(L)I2][L = 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen)] with AgNO3 in acetone gives the nitrato complexes [PtL(ONO2)2]. The palladium analogues were prepared from [Pd(L)Cl2] in dilute nitric acid. Dissolution of [ML(ONO2)2](M = Pd or Pt) in water results in the formation of the hydroxo-bridged dimers [LM(µ-OH)2ML][NO3]2 plus nitric acid. Reaction of [M(L)Cl2] with AgNO3 in water gives [LM(µ-OH)2ML][NO3]2 directly as the sole product. The dimers are resistant to substitution, although prolonged heating in aqueous nitric acid reforms [ML(ONO2)2]. The dimers add 1 mol of OH– to form the very stable trihydroxo-bridged compounds [LM(µ-OH)3ML]+(M = Pt, deep red; M = Pd, deep yellow) where each metal is five-co-ordinate. These complexes are slowly cleaved by hydroxide to give [ML(OH)2], which was also prepared either by base hydrolysis or by reaction of [M(L)Cl2] with Ag2O. Addition of HX (X = NO3, or ClO4) to [PtL(OH)2] affords [LPt(µ-OH)3PtL]+, [LPt(µ-OH)2PtL]2+ or [PtL(ONO2)2] at pH 8, 4, and 1 respectively. The complexes have been characterised by i.r., u.v., and n.m.r. (195Pt, 13C, and 1H) spectroscopy.

Polymeric copper(II)-orotato complexes, [(C5H2N2O4)Cu(H2O)2]n

The compound [(C5H2N2O4)Cu(H2O)2]n has been synthesized and its structure determined at room temperature. The primary coordination sphere at the Cu ion is square planar with the orotate dianion coordinating at the metal through heterocyclic nitrogen atom and adjacent oxygen of the carboxylate group, the remaining coordination sites are occupied by two water molecules. The orotate dianion is tricoordinated to one copper via N1 and one oxygen of the carboxylato group and to another copper atom via the other oxygen of the carboxylato group. The coordination at copper is extended to five by the other oxygen of the carboxylate group of another orotate molecule. Thus, the molecules are associated to form chains, the carboxylato group acting as a bridge between the metal ions, the orotato-group being tridentate. The title compound crystallizes in the monoclinic space group. P21/n1 with a = 9.515(5), b = 6.925(2), c = 11.861(6) Å, β = 95.285(9)°, Dcalc = 2.17 g cm−3, and z = 4.

A novel co-ordination mode for the squarate ligand [dihydroxycyclobutenedionate(2–)]: synthesis, crystal structure, and magnetic properties of catena-diaqua(2,2′-bipyridyl)-µ-(squarato-O1,O2)-nickel(II) dihydrate

The crystal and molecular structure of catena-diaqua(2,2′-bipyridyl)-µ-(squarato- O 1, O 2)-nickel( II) dihydrate, [{Ni(C 4O 4)(C 10H 8N 2)(H 2O) 2·2H 2O} n ][squarate = dihydroxycyclobutenedionate(2–)] has been determined by single-crystal X-ray analysis. The compound crystallizes in the monoclinic system, space group P2 1/ c, with a= 11.724(2), b= 7.418(1), c= 19.343(3)A, and β= 100.16(2)°. The crystal structure contains chains of squarato- O 1, O 2-bridged Ni II metal atoms. These chains are held together by strong hydrogen bonds between the non-co-ordinating oxygen atoms of the squarate anions and the water molecules. Variable-temperature (4.2–290 K) magnetic susceptibilities were determined; the squarato- O 1, O 2 bridge cannot mediate in a significant exchange interaction.

Coordination complexes of platinum(II) and platinum(II) with ligands involving the thioamido group: chloro bridged mixed-valence compounds

Abstract Complexes of the type [PtL4][PtCl6] where L = thiourea, thiocaprolactam, tetrahydro-2 pyrimidinethione, 2-imidazolidinethione (ethylenethiourea) and pyrimidine-2 thione, have been synthesized and investigated. This work initiates the study of a new family of mixed valence complexes of platinum involving S-donor ligands.

Synthesis, characterization and X-ray crystal structure of ethylenediamine-(orotato)palladium(II)

Reaction of the hydrolysis product of dichloroethylenediaminepalladium(II) with orotic acid methyl ester in aqueous or methanol-water media gives an orotic acid complex: [Pd(C5H2N2O4)(C2H8N2)](H2O)0.5. The complex was characterized by UV,1H NMR and X-ray diffraction. The compound crystallizes in the space group P1, a=9.742(1), b=10.535(1), c=11.113(1) A, α=100.60(1), β=103.165(7), γ=109.22(1)°, V=1006.2(2) A3, Z=2. It appears that during the reaction process hydrolysis of the ester function arises and that the compound obtained is a complex of orotic acid.

NMR (195Pt and 13C) contribution to the study of some Pt(II), Pt(IV) and mixed-valence thioamido complexes

Abstract The 195 Pt and 13 C chemical shifts (δ Pt and δ c ) are reported for platinum(II), platinum(IV) and class II mixed-valence complexes, with general formula [PtL 4 ]X 2 , cis - and trans -PtL 2 X 2 , PtL 2 X 4 and Pt 2 L 4 X 6 (where L may be thiourea, 2-imidazolidine-thione, tetrahydro 2-pyrimidinethione, thiocaprolactam, pyridine-2-thione and tetramethylthiourea, and X may be Cl or Br). The 195 Pt chemical shifts can be understood in view of 13 C data in terms of variations of electronegativities and σ-donor abilities of ligands attached to platinum.

On limited platinum chains. Synthesis and crystal structure of a green tetranuclear platinum compound, cis-diammine tetraplatinum squarate, Pt4(NH3)8(C404)4· 4H20. A structural analogue of platinum blues

Abstract From the reaction of the cis-dichlorodiammine hydrolysis product with squaric acid, green crystals of cis-diammine tetraplatinum squarate are obtained. A single crystal X-ray diffraction analysis shows that the compound consists of a tetranuclear chain, whose adjacent platinum atoms are bridged by squaric ligands.

Interactions of squaric and croconic acids with [PtL4]2+ complexes (L = NH3, L2 = ethylenediamine): oxidative properties of oxocarbon acids and crystal structure determinations

Squaric (H2Sq) and croconic (H2Croc) acid (H2A) react with [PtL4]2+ (L = ammonia or L2 = ethylenediamine) to yield complexes formulating as [PtL4](HA)2. The crystal structure of the complexes [Pt(en)2](HSq)2 and [Pt(en)2](HCroc)2 have been determined using X-ray diffraction techniques. Oxidation of platinum occurred in the course of the same reaction and complexes of [PtL4Cl2]A were obtained. The X-ray determination of the structure of [Pt(NH3)4Cl2]Sq is reported. Electrochemical measurements have been performed in the solid state to support the results obtained during the oxidation process.

Solid-state cyclometallation of the 1-methyl-2,4'-bipyridinium complexes of palladiumII and platinumII

Abstract The complexes [M(2,4′-bpyMe)X3] · nH2O (M = Pd, Pt; X = Cl, Br; 2,4′-bpyMe = 1-methyl-2,4′-bipyridinium, n = 0, 1, 2) cyclometallate with elimination of HX to give [M(2,4′bpyMe-H)X2] in the solid state on heating or upon microwave irradiation. Thermal analysis (TGA, DTA, DSC) in conjunction with infrared spectroscope indicates that these complexes cyclometallate in the temperature range 160–260°C. The ease of cyclometallation is Pd > Pt and Cl > Br. The time of cyclometallation with microwave irradiation depends on the mode of irradiation.