Cyclometallated Platinum(II) Complexes with Small Crown Ether Rings: Appropriate Choice of the Bridging Diphosphane to Coordinate Potassium Cations

[Image: see text] This account reports the synthesis and structural characterization of the first cyclometallated platinum(II) complex that coordinates a potassium cation in a sandwich arrangement via two 15-crown-5 ether rings within the same molecule. The cooperation of the two small crown ether moieties allows the entrapment of the non-ideal potassium ion. The reaction of the parent thiosemicarbazone ligand 3,4-(C(8)H(16)O(5))C(6)H(3)C(Me)=NN–(H)C(=S)NHMe, 1, containing the crown ether ring, with K(2)[PtCl(4)], or alternatively with PtCl(2)(DMSO)(2), and subsequent treatment with the diphosphanes Ph(2)PCH(2)PPh(2) (dppm) and Ph(2)PC(=CH(2))PPh(2) (vdpp) produced the double nuclear platinacycles 3a, 3b, and 4, probably via formation of the 2a and 2b intermediates. Complex 3a with the K(+) cation in a sandwich coordination was slightly mixed with 3b lacking any K(+). Alternatively, reaction of 1 with K(2)[PtCl(4)] or with PtCl(2)(DMSO)(2) followed by the diphosphane Ph(2)PC(=CH(2))PPh(2) (vdpp) only gave the dinuclear phosphane-bridged compound 4; this highlights the importance of choosing the right diphosphane ligand. Density functional theory calculations (B3LYP-D3/LANL2DZ-ECP-6.311++G**) revealed similar affinities for both dppm and vdpp derivatives to coordinate potassium cations. Crystal structure analysis was performed for compounds 3a and 4.