Assembled Structures and Electrical Conductivities of Salts Comprised of Cationic Sandwich Complexes and Polyoxometalates.

Polyoxometalates (POMs) are recognized for their diverse structures and catalytic properties, yet their organometallic salts have not been thoroughly investigated. In this study, we synthesized salts of a Keggin-type POM with cationic sandwich complexes featuring various substituents, [ X ] ₂ [SMo ₁₂ O ₄₀ ] [ X = Ru(C ₅ H ₅ )(C ₆ H ₅ R); R = H ( 1a ), Me ( 1b ), Bu ( 1c )], [Co(C ₅ H ₅ ) ₂ ( 2 ), and Co(C ₅ Me ₅ ) ₂ ( 3 )]. These salts exhibited similar structural characteristics, with each anion surrounded by 10 cations, forming two-dimensional sheet arrangements through O···O anion-anion contacts, except for the salt of 1c , which exhibited one-dimensional contact owing to the larger cation substituent. Additionally, [ 2 ](THA)[Mo ₆ O ₁₉ ], [ 3 ] ₂ [Mo ₆ O ₁₉ ], and [ 3 ](THA)[SMo ₁₂ O ₄₀ ], containing the Lindqvist-type POM [Mo ₆ O ₁₉ ] and/or tetrahexylammonium (THA) cation, were obtained, with the packing structure of [ 3 ] ₂ [Mo ₆ O ₁₉ ] closely resembling that of [ X ] ₂ [SMo ₁₂ O ₄₀ ]. Solvate crystals of [ 1a ] ₃ [PMo ₁₂ O ₄₀ ] were also prepared. [ 1a ] ₂ [SMo ₁₂ O ₄₀ ] exhibits an electrical conductivity σ of 1.4 × 10 ^-7 S cm ^-1 at 373 K, which is 2 orders of magnitude higher than those of (THA) ₂ [SMo ₁₂ O ₄₀ ] and [ 1a ]PF ₆ .