Renato Ettorre

The structure of dichlorodimethylbis(pyrazole-N2)tin(IV)

Abstract The structure of the complex Sn(CH3)2Cl2·2C3H4N2 has been determined by single crystal X-ray diffraction methods. The compound crystallizes in the monoclinic system, space Group C2/c (no. 15), with unit cell dimensions a 14.010(4), b 7.906(3), c 13.617(4) A, β 114.7(3)°, and Z = 4. The configuration about the tin atom is all-trans-octahedral. The pyrazole ligands, coordinated through the imino nitrogen atom, are intramolecularly and intermolecularly hydrogen bonded to the chloride ligands, the N(1)H … Cl distances being 3.480 and 3.297 A, respectively. Structural features of the complex are compared with those of other complexes of N-bonded heterocyclic ligands of the type Sn(CH3)2Cl2·2L.

The crystal structure of dichlorobis(N-methylimidazole)dimethyltin(IV)

Abstract The structure of the complex dichlorobis( N -methylimidazole)dimethyltin(IV), Me 2 SnCl 2 ( N Miz) 2 , has been determined from three-dimensional X-ray diffraction data. The compound crystallizes in the triclinic space group P 1 , and the cell parameters are: a 7.218(2), b 7.441(3), c 7.972(3) A, α 114.1(1), β 104.05(10), γ 97.8(1)°, Z = 1. The coordination geometry about the tin atom is all- trans octahedral; the N Miz. ligands are bonded to the metal through their pyridine-like nitrogen atom. The SnC, SnCl and SnN bond distances are 2.118(5), 2.571(3) and 2.329(5) A, respectively. The 1 H NMR spectra are consistent with the presence of a trans -octahedral structure for Me 2 SnCl 2 ( N Miz) 2 in solution, also.

1H and 13C NMR studies of palladium(II) and platinum(II) complexation of cytosine

Abstract 1H and 13C NMR spectra of cytosine, cytosine hydrochloride, and the systems cytosine-PdCl2 and cytosine-PtCl2 in DMSO-d6 are reported. Analysis of the spectra shows that the 4-amino-2(1H)pyrimidinone structure of the ligand is retained upon metal complexation and the N-3 atom is the binding site.

NMR studies of the interaction between cytosine and gold complexes

Abstract Hydrogen-1 NMR data are reported for the systems (a) cytosine-[(C 6 H 5 · CH 2 ) 2 S]-AuCl, (b) cytosine-(AuCl 4 ) − , and (c) cytosine-(AuBr 4 ) − , and for 5-bromocytosine and protonated 5-bromocytosine in DMSO- d 6 . Carbon-13 NMR data for system (c) are also reported. Analysis of the spectra shows: (a) complexation of cytosine to gold(I) through the N-3 atom; (b) coordination equilibria of cytosine and tetrachloroaurate(III) anion; (c) formation of 5-bromocytosine.

Coordination chemistry of peptides. Part I. Metal complexes of cyclo-L-methionyI-L-methionine

cis-Dichloro-bis-[acetonitril]-platin und der Titelligand reagieren in 2,2,2-Trifluorethanol im Verhaltnis 1:1 innerhalb einer Woche zu dem Komplex (I), die analoge Pd-Verbindung (I) wurde durch zweitagige Reaktion von Dichlor-bis- [dimethylsulfoxid]-palladium und dem Liganden in DMSO dargestellt.

Redox reaction mechanisms of platinum (IV) complexes

Abstract Kinetic investigations on redox reactions of platinum-(IV) complexes trans -[Pt(PEt 3 ) 2 Br 4 ], and trans - [Pt(PPr 3 ) 2 Br 4 ]] with SCN - ,I - , SeCN - and S 2 O 3 2- , and of trans -[Pt(PEt 3 )bb]2 Cl 4 ], trans -[Pt(AsEt 3 ) 2 Cl 4 ]and trans - [Pt(AsEt 3 )Br 4 ] with SCN - and SeCN - in methanol are reported. The following reaction scheme has been proposed: The reaction rates of the redox process are first order with respect to both the platinum(IV) complex and the reagent,Y n- . Representing with k 2 the second order rate constants, it was found that the log k 2 for the reactions of the various substrates with different anions are linearly related to log k 2 for the corresponding reactions of the complex trans -[Pt(PPr 3 ) 2 Cl 4 ], (termed as r(X)). according to the linear free energy relationship: log k 2 = r(x)+r s (where the constant r s depends upon the nature of the substrate). This relationship is discussed in terms of a reaction mechanism involoving a weak bond formation between the platinum(IV) complex and Y n- in the activated complex, probably a two electron bridged- transfer of the type:

Crystal structure of bis(2-aminopyridinium)dimethyltetrachlorostannate(IV) and its formation by hydrolysis of dimethyltin dichloride

Abstract The structure of (C 5 H 7 N 2 ) 2 [Sn(CH 3 ) 2 Cl 4 ] has been determined by X-ray diffraction. The compound crystallizes in the orthorhombic system, space group Pbca (No. 61), with unit cell dimensions a 15.585(2), b 17.561(2), c 7.088(1) A, and Z = 4. The structure consists of hydrogen-bonded chains of alternating [Sn(CH 3 ) 2 Cl 4 ] 2− anions and pairs of C 5 H 7 N 2 + cations. Each trans -dimethyltetrachlorostannate(IV) octahedral unit is surrounded by four 2-aminopyridinium ions and is involved in ten hydrogen-bonding interactions with d (NH⋯ Cl) ranging from 3.242(12) to 3.463(12) A. 1 H NMR data show that (C 5 H 7 N 2 ) 2 [Sn(CH 3 ) 2 Cl 4 ] is formed along with 1,3-dichloro-1,1,3,3-tetramethyldistannoxane in the reaction of Sn(CH 3 ) 2 Cl 2 and C 5 H 6 N 2 in moist CDCl 3 ; the fact that hydrolysis of the dimethyltin dichloride takes place is related to the relatively high basicity and low coordinating tendency of 2-aminopyridine.

Reactions of tetrabromoaurate(III) and dicyanodibromoaurate(III) with uracil

Abstract The reactions of AuBr − 4 and Au(CN) 2 Br − 2 with uracil in water produce gold(I) and 5-bromouracil and/or 5-bromo-6-hydroxy-5,6-dihydrouracil. The observed kinetics of the reactions are consistent with a mechanism involving a fast redox pre-equilibrium followed by bromination of the pyrimidine (X − = Br − or CN − ): The calculated equilibrium constant K = k 1 / k −1 is 1.6 × 10 −10 M for AuBr − 4 and 1.7 × 10 −11 M for Au(CN) 2 Br − 2 . Specific rates for the reduction of AuBr − 4 are correspondingly greater than those for the reduction of Au(CN) 2 Br − 2 .

Reduction reactions of trans-PtL2X4 complexes. Influence of the uncharged ligands L on the reduction reaction rates

Abstract Kinetic investigations on redox reactions of platinum(IV) complexes of the type trans-[PtL 2 X 4 (where L = pyridine, piperidine, methyl- and ethylamine, dimethyl- and diethylsulphide; X = Cl or Br) with SCN−, I−, SeCN− and S 2 O 3 2− in methanol are reported. All of the substrates studied are reduced by these anions to platinum(II) complexes; the reaction rates are first order with respect to both the platinum(IV) complex and the reducing anion. The reduction rates of the complexes trans-[PtL 2 X 4 ] increase in the order arsine

Structure of dibromobis(2-chloroimidazole)copper(II)

The structure of [CuBr 2 (C 3 H 3 ClN 2 ) 2 ] consists of discrete four-coordinate molecular units with two imidazole N(3) atoms and two bromide ions bonded to the metal. The coordination about the Cu atom is intermediate between tetarahedral and square-planar. The complex is isostructural with the corresponding chloride [CuCl 2 (C 3 H 3 ClN 2 ) 2 ]