RAMAN DIFFERENCE SPECTROPHOTOMETRIC STUDY OF COMPETITIVE REACTIONS OF NUCLEOTIDES WITH CIS-DIMETHYLGOLD(III); AND THE INVESTIGATION OF PROBLEMS ASSOCIATED WITH THE SYNTHESIS OF THERMALLY STABLE SALTS OF LITHIUM PERMETHYLMETALLATES

FRANK JOHN ARMATIS, Purdue University

Abstract

Competitive reactions of the heavy metal electrophile cis-dimethylgold(III) with a mixture of 20 mM 5'-GMP, 20 mM 5'-CMP, 30 mM 5'-AMP, 30 mM 5'-UMP have been studied at pH 7, 25(DEGREES)C. Raman difference spectroscopy was used to establish whether there is selectivity in the metal binding to the nucleic acids. The labile, bifunctional cis-dimethylgold(III) reacts with all four nucleotides with no selectivity in the coordination to pyrimidine over purine nucleotides. Attack is mainly at imino nitrogens with substitution of the metal for a proton. Cis-dimethylgold(III) exhibits little selectivity in its reaction with nucleotides. A study of the C211 cryptand was conducted to investigate the effect of this ligand upon the stability of salts of lithium cation. The reactions of the C211 cryptand with cyano complexes of lithium cyanide with cyanides of copper, silver and gold were studied. The following complexes were isolated and characterized by elemental analysis and infrared spectroscopy: Li(C211)Cu(,2)(CN)(,3), Li(C211)Cu(CN)(,4)(.)nH(,2)O(.)nEt(,2)O, Li(C211)Ag(CN)(,2), Li(C211)Au(CN)(,2) and Li(C211)Au(CN)(,4). Complexes containing more than one lithium cation (e.g. Li(,3)(C211)Cu(CN)(,4)(.)nH(,2)O(.)nEt(,2)O) may precipitate from solution with only a portion of the lithium complexed by C211. The infrared spectra of the complexes isolated revealed that the C211 cryptand complexes lithium such that little perturbation of the anionic species occurs. The reactions of the C211 cryptand with solutions of lithium permethylmetallates of chromium, tungsten, tin and copper were studied. The reactions of C211 with trimethylstannyllithium in THF and of C211 with dilithium octamethyltungstate in diethyl ether resulted in the syntheses of thermally stable solids containing Sn(CH(,3))(,3)('-) and W(CH(,3))(,8)('2-). Satisfactory elemental analyses for the tin and tungsten complexes could not be obtained, however, these permethylmetallates were identified by ('1)H nmr and infrared spectroscopies. The reaction of C211 with a solution of lithium dimethylcuprate in diethyl ether resulted in the synthesis of a thermally stable solid. The elemental analysis of this air sensitive solid suggests that the solid contains a permethyl complex of copper. The C211 cryptand reacts with Li(,3)Cr(CH(,3))(,6) in diethyl ether to give an unidentified side product. The low temperature (-40(DEGREES)C) Raman difference spectra of solutions containing mixtures of MeLi and LiBr in diethyl ether were obtained. Solutions of halide-free MeLi in diethyl ether exhibit bands in the low frequency region of the Raman spectra which are due to the Li(,4)C(,4) cluster vibrations of the MeLi tetramer. These low frequency bands are not observed in 1/1 solutions of MeLi/LiBr. These results obtained at -40(DEGREES)C are in agreement with previous Raman data obtained room temperature which suggests that the MeLi tetramers are altered or broken down in the presence of lithium halides.

Degree

Ph.D.

Subject Area

Chemistry

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