SYNTHESIS, STRUCTURE, REACTIVITY, AND ELECTROCHEMICAL STUDY OF A 5)-PENTAMETHYLCYCLOPENTADIENYL)CHLORORUTHENIUM(II) COMPLEX

[RuCp(eta(4)-C6H10)Cl] (Cp* = C(5)Me(5); 1) reacts with the tmbp liga nd (2; tmbp = 4,4',5,5'-tetramethyl-2, 2'-biphosphinine) in THF to aff ord the [RuCp(tmbp)Cl] complex 3, which has also been characterized b y a single-crystal X-ray diffraction study. Complex 3 crystallizes wit h one THF molecule. The environment about the Ru atom corresponds to t hat of a classical three-legged piano-stool structure. Reaction of 3 w ith LiBr and KCN in CH2Cl2/MeOH afforded [RuCp(tmbp)Br] (4) and [RuCp (tmbp)CN] (5), respectively. 3 also reacts in CH2Cl2, in the presence of NH4PF6, with various monodentate ligands to produce a series of st able cationic complexes of the type [RuCp(tmbp) (L)](+)[PF6](-) (L = acetonitrile (6), pyridine (7), trimethyl phosphite (8), triphenylphos phine (9), 2-bromo-4,5-dimethylphosphinine (10), tert-butyl isocyanide (11), cis-cyclooctene (12), norbornene (13)). All complexes were obta ined in good yields and have been characterized by a combination of el emental analyses and spectroscopic methods (IR and P-31, H-1, and C-13 NMR). The redox chemistry of 3 has been investigated by cyclic voltam metry in MeCN. Complex 3 is reversibly oxidized in [RuCp(III)(tmbp)Cl ] at +0.49 V (vs SCE). The first irreversible monoelectronic reduction wave, which occurs at -1.82 V vs SCE, indicates the formation of the [Ru(I)Cp(tmbp)] complex with the loss of Cl-. The second reversible r eduction wave at -2.24 V was assigned to the formation of the anionic [Ru(0)Cp(tmbp)](-) complex, which is stable within the time scale of the cyclic voltammetry.