M. Ramakrishna Udupa

Bio: M. Ramakrishna Udupa is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Organometallic chemistry & Dithiocarbamate. The author has an hindex of 3, co-authored 8 publications receiving 37 citations.

Cobalt(II) Complexes of Creatinine

Abstract: Cobalt(II) complexes of creatinine [Co(creat)2X2] (X = Cl, Br, I or NCS) and [Co(creat)2X2(H2O)2] (X = HCO2, HOCH2CO2 or CNCH2CO2) have been prepared. Their i.r. spectra show an increase in ν(NH) of the cyclic secondary amine group, compared to free ligand (3300 cm−1), indicating that cyclic nitrogen is involved in coordination. The thiocyanate group coordinates through nitrogen and carboxylates coordinate as univalent unidentate ligands. The electronic spectra and magnetic moments suggest a d7 configuration for cobalt: a tetrahedral geometry (4.4 B.M.) for halide and thiocyanate complexes, and an octahedral geometry (5.0 B.M.) for the carboxylate complexes. On heating, the ligand moiety is lost and the respective cobalt halide or cobalt carboxylate is formed, which is converted finally into Co3O4. There is a correlation between the high intensity electronic transitions and the polarographic half-wave potentials.

Reactivity of the tetrathiomolybdate(VI) anion towards hard and soft base chelating agents

Abstract: The interaction of hard base chelating agents (LH) such as 8-quinolinol (oxH), salicylaldehyde (salH) andN-nitrosophenylhydroxylamine (NphaH) with ammonium tetrathiomolybdate(VI), (1), in aqueous solution yields disulphidomolybdenum(VI) complexes, [MoS2L2] The ir absorptions at 540 and 510 cm−1 are assigned tov(Mo-S), which indicate that the two sulphido-groups arecis to each other, The interaction of (1) with soft base chelating agents (SS), such as dithiocarbamates (dtc), dithiophosphate (dtp) and xanthates (xan) yields dimeric sulphido-bridged sulphidomolybdenum(V) complexes, [Mo2S4(SS)2] and with potassium ethylthioxanthate (KEttxan) yields a molybdenum(IV) complex, [Mo(Ettxan)4] The [Mo2S4(R2dtc)2] complexes were also obtained by the interaction of [MoO2(R2dtc)2] with phosphorus pentasulphide in xylene It was concluded that tetrathiomolybdate(VI) undergoes facile reduction when compared with tetraoxomolybdate(VI)

Reactions of (diethyldithiocarbamato)halogenotellurium(II); crystal structures of R[Te{S2CNEt2}X2][R = NEt4, X = I; R = H(phen)2(phen = 1,10-phenanthroline), X = I or Br]

Abstract: The reactions of (diethyldithiocarbamato)halogenotellurium(II) with thiourea, benzimidazole-2-thiol, halides (Cl–, Br–, I–) and 1,10-phenanthroline (phen) have been studied. The products were principally characterized by elemental analyses, IR and 1H NMR spectroscopies. Novel anionic (diethyldithiocarbamato)dihalogenotellurate(II) complexes resulted from the reactions of Te(S2CNEt2)X (X = Br or I) with NEt4X (X = Br or I) and phen. The crystal structures of the complexes [NEt4][Te(S2CNEt2)I2], [H(phen)2][Te(S2CNEt2)I2] and [H(phen)2][Te(S2CNEt2)Br2] have been determined. In the anions tellurium is co-ordinated to two sulfur atoms of the dithiocarbamate in an almost isobidentate manner and to two halides in an overall planar trapezoidal geometry. In [NEt4][Te(S2CNEt2)I2] the two iodides are almost equidistant to tellurium with distances of 3.079(1) and 3.072(1)A, whereas in [H(phen)2][Te(S2CNEt2)I2] the two Te–I distances are 3.151(1) and 3.038(1)A and in [H(phen)2][Te(S2CNEt2)Br2] the two Te–Br distances are 2.911(1) and 2.986(1)A. In [H(phen)2]+ the proton is bound to one of the nitrogen atoms of a phenanthroline group and the two phen groups are held together by three hydrogen bonds, of which two are of the interesting type C–H ⋯ N.