Crystal structures and spectroscopic properties of platina-beta-diketones - a new mode of stacking in platinum complexes

Platina-beta-diketones [Pt-2{(COR)(2)H}(2)(mu-Cl)(2)] (R = Me 1a, Et 1b, n- Pent 1c, n-Hex 1d, (CH2)(4)Ph 1e) are prepared by reaction of hexachloropla tinic acid in n-butanol with silyl-substituted acetylenes R'C=CSiMe3 (R' = R-CH2). Complexes 1 are characterized by NMR, IR and UV-vis spectroscopies. The crystal structures of complexes 1a, b, e reveal discrete dinuclear mol ecules linked via Pt ... Pt interactions [d(Pt ... Pt)= 3.318(1)-3.352(1) A ngstrom] in such a way that polymeric chain-like structures are formed. The se complexes exhibit only an emission in the solid state (lambda(max) 555 n m) that is ascribed to a d(8)-d(8) electronic excited state. No emission is observed in solution. The distinct differences in the absorption and emiss ion spectra in solution and in the solid state, as well as the lack of phot oconductivity, are ascribed to the columnar structures in the solid state w ith the mode of stacking of the platinum centers with alternating Pt ... Pt interactions and Pt-Cl-Pt bridges. (C) 2000 Elsevier Science S.A. All righ ts reserved.