AXIAL BINDING OF 2-METHYLIMIDAZOLE TO THE TETRAARYLCARBOXYLATODIRUTHENIUM(II,III) CORE - X-RAY CRYSTAL-STRUCTURE OF [RU-2(O2CC6H4-P-OME)(4)(2-MIMH)(2)](CLO4). 1.75CH(2)CL(2).H2O

Diruthenium (II. III) complexes of the type [Ru-2(O2CAr)(4) (2-mimH)(2 )](ClO4) (Ar = C6H4-p-X : X=OMe,1, X=Me, 2, 2-mimH=2-methylimidazole) have been isolated from the reaction of Ru2Cl(O2CAr)(4) with 2-mimH in CH2Cl2 followed by the addition of NaClO4. The crystal structure of 1 .1.75CH(2)Cl(2).H2O has been determined. The crystal belongs to the mo noclinic space group p2(1)/c with the following unit cell dimensions f or the C40H40N4O16ClRu2.1.75CH(2)Cl(2).H2O (M = 1237.0) : a = 12.347(3 )Angstrom, b = 17.615(5)Angstrom, c = 26.148(2)Angstrom,beta = 92.88(1 )degrees. v = 5679(2)Angstrom(3). Z=4, D-c = 1.45 g cm(-3). lambda(Mo- K-alpha) = 0.7107 Angstrom, mu(Mo-K-alpha) = 8.1 cm(-1), T = 293 K, R = 0.0815 (wR(2) = 0.2118) for 5834 reflections with 1 > 2 sigma(I). Th e complex has a tetracarboxylatodiruthenium (II, III) core and two axi ally bound 2-methylimidazole ligands. The Ru-Ru bond length is 2.290(1 )Angstrom. The Ru-Ru bond order is 2.5 and the complex is three-electr on paramagnetic. The complex shows an irreversible Ru-2(II,III)-->Ru-2 (Il,II) reduction near -0.2 V vs SCE in CH2Cl2-0. 1 MTBAP. The complex es exemplify the first adduct of the tetracarboxylatodiruthenium (II,I II) core having N-donor ligands.