Stable subnanometre Pt clusters in zeolite NaX via stoichiometric carbonylcomplexes: Probing of negative charge by DRIFT spectroscopy of adsorbed COand H-2

Negatively charged platinum carbonyl Chini complexes [Pt-3(CO)(6)](n)(2-) w ith n = 2-4 were synthesized by reductive carbonylation of Pt2+ in NaX zeol ite and subsequently decomposed in vacuum at temperatures up to 773 K. The Pt clusters obtained preserved a low nuclearity, evidenced by rapid recarbo nylation resulting in regeneration of the initial carbonyl Chini complexes. The electronic state of the metal clusters was probed by diffuse reflectan ce infrared Fourier transform (DRIFT) spectroscopy of chemisorbed CO and H- 2. A strong electron donor capacity of Pt was indicated by the bands of (i) the linearly bonded CO at 1958-1976 cm(-1) and (ii) the stretching frequen cy of terminal platinum hydrides at 2040 cm(-1). It was concluded that the strong donor properties have to be attributed to negative charging of the P t clusters, originating from the precursor carbonyl complex.