Synthesis and characterization of ?,?1-and ?,?2-dithiolate di- and triruthenium complexes with a dppf ligand [dppf=1,1?-bis (diphenylphosphino)ferrocene]

Reactions of [Ru3(CO)10(mu-dppf)] (1) with 1,3-propanedithiol and 1,2-ethanedithiol have been investigated. The triruthenium complex [HRu3(CO)8(mu-SCH2CH2CH2SH)(mu-dppf)] (2) was obtained as the major product (38%) from the reaction of [Ru3(CO)10(mu-dppf)] with 1,3-propanedithiol in THF (66 degrees C). In contrast, the reaction conducted in toluene (110 degrees C) furnished the dinuclear [Ru2(CO)4(mu-SCH2CH2CH2S)(mu-dppf)] (3) in low yield (8%). Similar reactions of 1 with 1,2-ethanedithiol at 66 degrees C afforded [HRu3(CO)8(mu-SCH2CH2SH)(mu-dppf)] (4) in a 23% yield while performing the reaction at 110 degrees C led to decomposition. Compounds 2 and 4 are formed by the oxidative addition of one of the S-H bonds of the dithiols. In contrast, the dinuclear 3 is formed by cluster fragmentation and oxidative addition of both S-H bonds of the dithiol donor. Compounds 2 and 4 are fluxional in solution. The VT NMR behavior of 2 and 4 are consistent with a torsional motion of the cyclopentadienyl rings of the dppf ligand about the Ru-Ru edge that is bridged by the diphosphine ligand. The new compounds have been characterized by IR and NMR (1H and 31P{1H}) spectroscopies, together with single-crystal X-ray diffraction analysis on compounds 2 and 3. The bonding in 2 and 3 has been investigated by electronic structure calculations. The location of the hydride in cluster 2 has been established and the energy ordering for the different stereoisomers based on 2 have been computationally evaluated.