Polymeric low-valence platinum-phenanthroline complexes as precursors of platinum colloids

It was found that the reduction of Pt(II), Pt(III) and Pt(I,III) acetates with H₂ in the presence of 1,10-phenanthroline (phen), according to the standard procedure for the synthesis of palladium-561 giant clusters, resulted, unexpectedly, in the high-nuclear Pt(I) complex of the empirical composition Pt₈phen₃(OAc)₄(OH)₄(H₂O)₆ instead of the expected platinum colloid. Data of electron microscopy (TEM, HREM), small-angle X-ray scattering (SAXS), EXAFS and thermal analysis (DTA-TG) combined with elemental microanalysis all point to a loose structure of the obtained complex, with a minor Pt---Pt bonding (average coordination number for the Pt---Pt bonds is about 1). Variation of the preparation procedure resulted in a series of polymeric phen-platinum complexes, containing Pt atoms in oxidation states ranging from (+1) to (+0.3), and whose main structural features were established by the above-mentioned techniques. Giant clusters with dense Pt/PtO_x cores (coordination number for the Pt---Pt bonds is about 6) were obtained by gradual heating of the precursor Pt complex to about 200°C as well as by a modified preparation procedure at 20°C.