MOLECULAR-STRUCTURE, DYNAMICS, AND CRYSTAL ORGANIZATION OF [(MU-CL)(3)((ETA(6)-ARENE)RU)(2)] [BF4] (ARENE=C6H6 AND C(6)H(5)ME) AND A BONDING STUDY BY EXTENDED HUCKEL CALCULATIONS

The complexes [(mu-Cl)(3){(eta(6)-arene)Ru}(2)](+) (arene = C6H6, 1, a nd C(6)H(5)Me, 2) have been synthesized by reaction of the appropriate dihydroarene and ruthenium(III) chloride in ethanol, yielding {(mu-Cl )(2)[(eta(6)-arene)RuCl](2)}, which then affords the desired product o n treatment with aqueous HBF4 in trifluoroacetic acid. Single crystal X-ray diffraction data have been collected at 296 and 150 K for 1 (la, and Ib, respectively) and at 150 K for 2. Compound la is monoclinic, space group P2(1)/a, a = 8.4449(6), b = 18.9448(12), c = 10.3154(7) An gstrom, beta = 103.416(4)degrees, V = 1605.3 Angstrom(3) Z = 4; Ib is monoclinic, space group P2(1)/a, a = 8.43(2), b = 18.68(14), c = 10.25 (2) Angstrom, beta = 104.8(1)degrees, V = 1560.5 Angstrom(3), Z = 1; 2 is triclinic, space group P $($) over bar$$ 1, a = 9.355(5), b = 9.66 8(4), c = 10.190(4) Angstrom, alpha = 92.12(3), beta = 104.71(4), gamm a = 93.07(3)degrees, V = 888.9 Angstrom(3), Z = 2. The hydrogen atoms in 1, as well as the methyl groups in 2, have been found to bend signi ficantly towards the metal atoms. The bonding interactions between the arene fragments and the metals have been studied by means of extended Huckel calculations showing that a 6 degrees bending is required in o rder to optimize the overlap between the (mu-Cl)(3)Ru-2 fragment and t he arenes. The molecular structures of both complexes have been invest igated in relation with the respective crystal structures. The ion org anization in crystalline 1 and 2 has been compared with that in analog ous bis(arene) derivatives. The dynamics about equilibrium positions a s well as the reorientational motion of the benzene ligands in 1 at th e two temperatures have been investigated by means of thermal motion a nalysis and packing potential energy calculations.