New heteroligand peroxo compounds of titanium(IV): synthesis, characterisation and spectroscopic studies of A 2[Ti(O 2) 2SO 4]·4H 2O (A = NH 4 OR K), [Ti(O 2) 2(L-L)] (L-L = 1,10-phenanthroline, 2,2'-bipyridine) and [Ti(O 2) 2(thiourea)] · H 2O

Abstract

Alkali diperoxomonosulphatotitanate(IV) tetrahydrates, A 2[Ti(O 2) 2-SO 4·4H 2O (A = NH 4 or K), have been synthesised from the reaction of freshly precipitated TiO 2 with 7.65 M H 2SO 4 and 30% H 2O 2 at pH 2.5 – 3, adjusted by the addition of aqueous ammonia or potassium hydroxide. Also, three molecular mixed-ligand diperoxo compounds of titanium(IV), viz. [Ti(O 2) 2( o-phen)], [Ti(O 2) 2(bipy)] and [Ti(O 2) 2(thiourea)] · H 2O have been obtained by reacting a solution of freshly precipitated TiO 2 in 40% HF with an ethanolic solution of 1,10-phenanthroline ( o-phen), an ethanolic solution of 2,2'-bipyridine (bipy), and an aqueous solution of thiourea, respectively, and 30% H 2O 2 maintained at pH 7 by the addition of aqueous ammonia. The compounds are all yellow products and have been characterised from the results of elemental analyses, room temperature magnetic susceptibility measurements, and IR and laser Raman (1R) spectroscopic studies. The IR and laser Raman spectra show that each of the O 2 2− and SO 4 2− ligands in [Ti(O 2) 2SO 4] 2− ion, and the O 2 2− and o-phen or bipy in the respective cases occur as bidentate ligands, while thiourea in [Ti(O 2) 2 (thiourea)] · H 2O binds the metal centre in a monodentate manner. The compounds are all diamagnetic and EPR-silent.