POLYMORPHISM AND RELATED MAGNETIC-BEHAVIOR IN DECAMETHYLFERROCENIUM SALTS OF TRANSITION-METAL MALEONITRILEDITHIOLATES

Several decamethylferrocenium/transition-metal maleonitriledithiolate compounds have been synthesized and structurally characterized. The co mpounds [Fe(cp)(2)](x)[M(mnt)(2)](gamma)(CH3CN)(z) (M = Cu(II), Co(II I), Fe(III)) crystallize in the triclinic space group P $($) over bar$ $ 1 (No. 2). For M = Co(III) two solid-state phases have been isolated . alpha-[Fe(cp)(2)](2)[Co(mnt)(2)](2)(CH3CN)(2) (Fe(2)Co(2)A): a = 9. 894(4) Angstrom, b = 12.942(6) Angstrom, c = 15.056(6) Angstrom, alpha = 110.13(3)degrees, beta = 981.41(4)degrees, gamma = 107.78(3)degrees , V = 1657 Angstrom(3), M(r) = 1413,3, d(c) = 1.419 g/cm(3), Z = 1, an d R = 0.061 for 2351 reflections with 1 greater than or equal to 3 sig ma(1). beta-[Fe(cp)(2)](2)[Co(mnt)(2)](2) (Fe2Co2B): a = 9.576(8) Ang strom, b = 12.849(4) Angstrom, c = 13.641(7) Angstrom, alpha = 108.13( 4)degrees, beta = 90.91(6)degrees, gamma = 103.54(4)degrees, V = 1544 Angstrom(3), M(r) = 1331.2, d(c) = 1.431 g/cm(3), Z = 1, and R = 0.043 for 2407 reflections with I greater than or equal to 3 sigma(1). The isostructural. ct modification is observed for M = Fe(III). alpha-[Fe( cp)(2)](2)[Fe(mnt)(2)](2)(CH3CN)(2) (Fe(2)Fe(2)A): a = 9.905(7) Angst rom, b = 12.966(5) Angstrom, c = 15.142(3) Angstrom, alpha = 109.77(2) degrees, beta = 98.64(4)degrees, gamma = 108.06(6)degrees, V = 1668 An gstrom(3) M(r) = 1407.2, d(c) = 1.401 g/cm(3), Z = 1, and R = 0.063 fo r 3125 reflections with 1 greater than or equal to 3 sigma(I). The dim eric anionic species show a square pyramidal coordination for the meta l (the apical M-S bonds are Co-S = 2.39, 2.35 Angstrom and Fe-S = 2.49 Angstrom). Orthogonal arrangement of adjacent cations is observed in the decamethylferrocenium chains of the two a compounds, while a paral lel packing exists in the beta modification. [Fe(cp)(2)]Cu-2(mnt)(2) (Fe2Cu): a = 9.713(5) Angstrom, b = 11.407(4) Angstrom, c = 11.958(5) Angstrom, alpha = 100.90(2)degrees, beta = 113.20(5)degrees, gamma = 9 2.66(3)degrees, V = 1185 Angstrom(3), M(r)= 996.5, d(c) = 1.396 g/cm(3 ), Z = 1, and R = 0.041 for 2724 reflections with 1 greater than or eq ual to 3 sigma(1). The dianion [Cu(mnt)(2)](2-) exhibits a planar mono meric structure and the mixed anion-cation stacks adopt a...A(2-)D(+)D (+)A(2-)D(+)D(+)A(2-)... arrangement with short anion-cation distances : d(Fe-S) 5.54 Angstrom, and d(Fe-Cu) = 6.37 Angstrom. The magnetic pr operties of all the compounds have been investigated. In both Fe(2)Co( 2)A and Fe2Co2B the decamethylferrocenium cations have been found to b e magnetically isolated. In Fe(2)Fe(2)A, a strong antiferromagnetic in teraction within the {[Fe(mnt)](2)}(2-) dimeric unit has been characte rized. In Fe2Cu, finally, each [Cu(mnt)(2)](2-) is found to interact a ntiferromagnetically with two adjacent [Fe(C-p)(2)](+) cations.