Michele Gaul

Xanthine complexes with 3d metal perchlorates

Abstract Complexes of xanthine (xnH) with 3d metal perchlorates were prepared by refluxing mixtures of ligand and metal salt in ethyl acetate-triethyl orthoformate. In all cases, partial substitution of anionic xn − for ClO 4 − groups occurs, and the solid complexes isolated also contain invariably two neutral xnH ligands per metal ion, viz. Cr(xn) 2 (xnH) 2 ClO 4 , Fe(xn) 2 (xnH) 2 ClO 4 ·H 2 O, M(xn)(xnH) 2 ClO 4 ·H 2 O (M = Fe, Co, Ni) and M(xn)(xnH) 2 ClO 4 · 2H 2 O (M = Mn, Zn). The new complexes are generally hexacoordinated and appear to be linear chainlike polymeric species characterized by a (-Mxn-) n single-bridged backbone. Four terminal ligands per metal ion, including two xnH groups in all cases, complete its inner coordination sphere; the remaining two terminal ligands differ from complex to complex as follows: M = Cr 3+ xn − , -OClO 3 ; Fe 3+ xn − , H 2 O; Fe 2+ , Co 2+ , Ni 2+ OClO 3 , H 2 O; Mn 2+ , Zn 2+ two aqua ligands. Probable binding sites of bidentate bridging xn − and unidentate terminal xnH and xn − are discussed.

ADDUCTS OF THEOBROMINE WITH 3d METAL PERCHLORATES

Abstract Adducts of theobromine (tbH) with 3d metal perchlorates (Mn+ = Cr3-. Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2- I here prepared by refluxing mixtures of the Iigand and a metal salt in ethyl acetate-triethyl orthoformate. The new complexes invariably involve 2: 1 molar ratios of tbH to metal ion and are apparently monomeric with terminal tbH ligands binding riaa ring nitrogen (N9 or Nl). The Mn2+, Cu2+ and Zn2- complexes are distorted tetrahedral, involving tuo tbH and two unidentate perchlorato ligands in the first coordination sphere of the metal ion. The remaining metal(II) complexes (Fe, Co, Ni) were obtained as monohydrates. These compounds are pentacoordinated of the [M(tbH)2(OClO3)2(OH2)] type, containing one aqua ligand in addition to the tbH and perchlorato ligands. The Cr3+ and Fe3+ complexes are low-symmetry hexacoordinated, with two tbH ligands. two unidentate and one bidentate chelating perchlorate Iigands.

THEOPHYLLINE ADDUCTS WITH 3d METAL PERCHLORATES

Abstract 2:1 adducts of theophylline (tpH) with 3d metal perchlorates were prepared by refluxing mixtures of ligand and metal salt in ethyl acetate-triethyl orthoformate. The new complexes appear to be generally monomeric, involving terminal N7-bonded tpH ligands. Mn2+. Co2+ and Zn2+ perchlorates afforded water-free adducts of the types [M(tpH)2(OClO3)(=O2ClO2)]. (M=Mn, Co) and [Zn(tpH)2(OClO3)2]. The former two complexes are pentacoordinated with one unidentate -OClO3 and one bidentate chelating = O2ClO2 ligand, while the Zn2+ complex is analogous to the previously reported Cu2+ complex. i.e., tetrahedral with two unidentate -OClO3 ligands. The Co2+ complex is moisture-sensitive, being converted to the dihydrate [Co(tpH)2(OClO3)2 (OH2)2] immediately upon exposure to the atmosphere. The rest of the new complexes were isolated in the form of hydrates and are of the types: [Ni(tpH)2(OClO3)2(OH2)2] hexacoordinated with exclusively coordinated -OClO3. 1[Fe(tpH)2)2(OClO3)(OH2)]ClO4, distorted tetrahedral, and ...

Adenine N(1)-oxide complexes with metal chlorides

Abstract M(LH)2Cl3 (M = Al, Fe), VO(LH)Cl2 and Dy(LH)3Cl3 adducts and mixed neutral-monoanionic ligand complexes of the M(LH)LCl2 (M = Cr, Fe) and M(LH)LCl3 (M = Th, U) types are formed by boiling under reflux mixtures of adenine N(1)-oxide (LH) and the VO2+, M3+ (M = Al, Cr, Fe, Dy) or M4+ (M = Th, U) chloride in ethanol-triethyl orthoformate. Characterization studies indicate significant differences in the ligand (LH or L−) binding sites from complex to complex, viz.: Monomeric complexes: [Al(LH)2Cl3] N(9) (unidentate); [VO(LH)Cl2] chelating through O(1), N(6); [Fe(LH)2Cl3] one unidentate O(1)- and one bidentate chelating O(1), N(6)-bonded LH. Bi- or poly-nuclear linear complexes with single or double bridges of O(1), N(7)-bonded L− or LH between adjacent metal ions involve the following binding sites for the terminal LH ligands: [M(LH)-LCl2]x (M = Cr, Fe; x > 2) chelating through O(1), N(6); [Dy(LH)3Cl3]2 and [M(LH)LCl3]x (M = Th, U) N(9) (unidentate).

Nicke(II) halide complexes with hypoxanthine and xanthine

SummaryNi(LH)3LX complexes (LH=hypoxanthine or xanthine; X=Cl, Br or I) are formed by boiling under reflux 2:1 molar mixtures of LH and hydrated NiX2 in HC(OEt)3−MeCO2Et. The new complexes appear to be linear chain-like polymers, characterized by bidentate monoanionic L− ligands singly bidging between adjacent Ni2+ ions. A coordination number six is attained by the presence of three terminal unidentate LH and one X ligand in the first coordination sphere of each Ni2+ ion. The neutral LH and monoanionic L− ligands bind exclusivelyvia ring nitrogens to NiII. The probable binding sites of the uni- and bi-dentate hypoxanthine and ligands in the new complexes are discussed.

Xanthine and hypoxanthine complexes with cobalt(II) halides

Complexes of the Co(LH)2LX and Co(LH)2- LI·H2O (LH=xanthine or hypoxanthine; XCl, Br) types were synthesized by refluxing 2:1 molar mixtures of LH and CoX2 in triethyl orthoformate-ethyl acetate for one week. Characterization studies suggest that the new complexes are monomeric involving exclusively terminal neutral LH and monoanionic L− ligands. The Co(II) chloride and bromide complexes are tetrahedral (CoN3X chromophores), while the monohydrated Co(II) iodide complexes are pentacoordinated (CoN3IO absorbing species). The hypoxanthine ligands are probably N7-bound to Co(II). In the case of the xanthine complexes, N7 and N9 were considered as about equally likely to function as the primary binding site of the terminal unidentate xanthine ligands.

Ferric Chloride and Bromide Complexes with Xanthine and Hypoxanthine

Abstract Complexes of the type Fe(LH)3LX2 (LH α xanthine or hypoxanthine; X α Cl or Br) were synthesized by refluxing 2:1 molar mixtures of LH and FeX3, in triethyl orthoformate-ethyl acetate for one week. Characterization studies suggest that the new complexes are hexacoordinated and monomeric, involving a cis-FeN4X2 arrangement of the terminal ligands around the Fe3 + ion. The hypoxanthine ligands probably bind via the N7 imidazole nitrogen to Fe(III). In the case of the xanthine complexes, the N7 and N9 imidazole nitrogens are considered as about equally likely to function as the binding site of the terminal neutral and monoanionic xanthine ligands.

Cobalt(II), nickel(II) and iron(IlI) halide adducts with theobromine

Abstract Adducts of theobromine (L) with Co(II) and Ni(II) chlorides, bromides and iodides and Fe(III) chlorides and bromides were synthesized by refluxing 2:1 molar mixtures of L and the hydrated metal salt in triethyl orthoformate-ethyl acetate. Solid complexes of the CoL2X2 (X = Cl, Br), CoL2I2· H2O, NiL2X2·2H2O (X = Cl, Br, I) and FeL2X3·H2O (X = Cl, Br) types were isolated. Characterization studies suggest that the new adducts are neutral monomeric with terminal unidentate L, halo and, wherever applicable, aqua ligands. The Co(II) complexes are distorted tetrahedral for X = Cl, Br and pentacoordinated for X = I, while the Ni(II) and Fe(III) adducts are hexacoordinated. The pyrimidine N1 and imidazole N9 ring nitrogens were considered as equally likely to act as the binding site of terminal theobromine.

Theophylline Adducts with cobalt(II), Nickel(II) and Iron(III) Halides

Abstract Theophylline (L) adducts with Co(II) and Ni(II) chlorides, bromides and iodides and Fe(III) chloride and bromide were prepared by boiling under reflux 2:1 molar mixtures of L and hydrated metal salt in triethyl orthoformate-ethyl acetate. The new solid complexes obtained are adducts of the types CoL2X2 (X = Cl, Br, I), NiL2X2.H2O (X = Cl, Br), NiL2I2.2H2O, and FeL2X3.H2O (X = Cl, Br). On the basis of spectral, magnetic and conductance characterization, these complexes were formulated as being neutral monomeric with terminal N7-bound unidentate L, halo and, wherever applicable, aqua ligands. The Co(II)complexes are distorted tetrahedral species, the Ni(II) chloride and bromide adducts are pentacoordinated and the Ni(II) iodide and the Fe(III) complexes hexacoordinated.