Reactions of pyrazole based ligand and halide bridged arene d 6 metal precursors resulted a series of mono and di-substituted pyrazole based half sandwich d 6 metal complexes. In general, they are formulated as [(arene)MLCl 2 ] [M = Ru, arene = benzene (1), p-cymene (2), arene = Cp*, M = Rh (3) and Ir (4)] and [(arene)ML 2 Cl] [M = Ru, arene = benzene (5), p-cymene (6), arene = Cp*, M = Rh (7) and Ir (8)]. All these complexes were characterized by various spectroscopic techniques (IR, 1 H NMR, ESI-MS, and UV/Vis). The molecular struc-* Dr. M. R. Kollipara E-Mail: kmrao@nehu.ac.in [a] Center for Advanced Studies in Chemistry 79tures were confirmed by single-crystal X-ray diffraction technique. Spectroscopic studies revealed that complexation i.e., mono-and disubstitution occurred by the ratio-based reaction between pyrazole ligand and metal precursor through the neutral nitrogen rather than protic nitrogen. In these complexes deprotonation of the protic nitrogen does not occur unlike the other complexes containing pyrazole derivatives, in which the pyrazole ligand is anionic.
[(benzene)RuCl 2 L] (1)Yield: 47 %. IR (KBr): ν = 3434 (νN-H), 1639 (νC=C), 1432 (νC=N) cm -1 . 1 H NMR (400 MHz, CDCl 3 ): δ = 12.94 (s, 1 H), 8.26