Preparation, properties, and reactions of metal-containing heterocycles: Part CV. Synthesis and structure of polyoxadiphosphaplatinaferrocenophanes

A series of novel heterobimetallic crown ether-like polyoxadiphosphaplatinaferrocenophanes cis-[1,1′-Fc(CH2O(CH2CH2O)nCH2CH2PPh2)2]PtCl2 (n=1–3) (4a–c) was synthesized in good yield by cyclization of the bis(phosphine) ligands 1,1′-Fc(CH2O(CH2CH2O)nCH2CH2PPh2)2 (n=1–3) (3a–c) and (PhCN)2PtCl2 under high dilution conditions in CH2Cl2. The bisphosphines 3a–c are obtained by reaction of the corresponding diols 1,1′-Fc(CH2O(CH2CH2O)nCH2CH2OH)2 (n=1–3) (1a–c) with: (i) CH3SO2Cl in CH2Cl2 and (ii) LiPPh2 in THF. Although the X-ray crystal structure of 4a shows that the cavity is large enough for the encapsulation of small metal cations, inclusion experiments of 4a–c with Group 1 cations, and Mg2+, or NH4+ in solution applying NMR titration and cyclovoltammetric methods reveal no evidence for the formation of host–guest complexes for 4a,b. In the case of 4c only the addition of Na+ or K+ leads to an insignificant effect.