Twelve new multidentate poly(pyrazol-1-ylmethyl)benzene ligands , (5)-(16), have been synthesized by phase-transfer-catalysed alkylations of pyrazoles with poly( bromomethyl )benzenes, and their 1H and 13C n.m.r. spectra have been fully assigned. X-Ray crystal structure determinations have been carried out on the tetrachloropalladate salt of the diprotonated form of 1,4-bis(3,5-dimethylpyrazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene and on hexakis (pyrazol-1-ylmethyl)benzene.

Eleven chelating tetrazole -containing ligands have been synthesized, and their complexes with palladium(II) and ruthenium(II) prepared. Proton n.m.r. spectroscopy, electronic absorption spectroscopy and cyclic voltammetry have been used to study the nature of the metal-ligand interactions in these complexes. The negatively charged tetrazolate group is shown to be a strong electron donor with very different properties to those of the protonated or alkylated tetrazole group. This leads to pH control of the properties of transition metal complexes containing such ligands.

The bromide (5), prepared by treatment of the glycine derivative (4) with N-bromosuccinimide, reacted with hexabutylditin to give diastereoisomers of the glycine dimer (7), only when moisture was rigorously excluded from the reaction. Otherwise the major products were the diastereoisomers of the ether (11). The structure of the racemic diastereoisomer (11) was determined by X-ray crystallography. Photolysis of mixtures of the glycine derivative (4) and di-t-butyl peroxide gave the alanine derivative (10) in addition to the diastereoisomeric dimers (7).

The syntheses of 23 new chelating ligands are described. Most of these ligands are derived from the chiral pyrazole (1) which has been linked to a variety of heterocycles , namely pyridine, pyrimidine, pyridazine, isoxazole , benzimidazole, thiophen and furan. In certain cases the parent achiral analogues have also been prepared. Preliminary studies of the coordination chemistry of these ligands with selected transition metals have been carried out. The X-ray crystal structures of palladium complexes of isoxazole- and thiophen-containing ligands have also been determined.

The colourless crystalline form of the benzoylpyrazolone (2) has molecules with the NH structure (2c) stabilized by intermolecular hydrogen bonds. At room temperature crystals are monoclinic: P21/c, a 13.508(5), b 9.124(4), c 11.451(3)Ǻ, β 90.80(3)°, Z4; the structure was refined to R 0.059, Rw 0.048. The acetoacetylpyrazolone (3) has the OH structure (3c) with two intramolecular hydrogen bonds. At 193 K crystals are triclinic: Pī , a 7.142(2), b 13.704(8), c 14.699(7)Ǻ, α 117.36(3), β 96.87(3), γ 93.73(3)°, Z 4; the structure was refined to R 0.049, Rw 0.054.