title: Influence of cyclopentadienyl ring-tilt on electron-transfer reactions: redox-induced reactivity of strained [2] and [3]ruthenocenophanes.
abstract: In contrast to ruthenocene [Ru(η(5) -C5 H5 )2 ] and dimethylruthenocene [Ru(η(5) -C5 H4 Me)2 ] (7), chemical oxidation of highly strained, ring-tilted [2]ruthenocenophane [Ru(η(5) -C5 H4 )2 (CH2 )2 ] (5) and slightly strained [3]ruthenocenophane [Ru(η(5) -C5 H4 )2 (CH2 )3 ] (6) with cationic oxidants containing the non-coordinating [B(C6 F5 )4 ](-) anion was found to afford stable and isolable metalmetal bonded dicationic dimer salts [Ru(η(5) -C5 H4 )2 (CH2 )2 ]2 [B(C6 F5 )4 ]2 (8) and [Ru(η(5) -C5 H4 )2 (CH2 )3 ]2 [B(C6 F5 )4 ]2 (17), respectively. Cyclic voltammetry and DFT studies indicated that the oxidation potential, propensity for dimerization, and strength of the resulting RuRu bond is strongly dependent on the degree of tilt present in 5 and 6 and thereby degree of exposure of the Ru center. Cleavage of the RuRu bond in 8 was achieved through reaction with the radical source [(CH3 )2 NC(S)SSC(S)N(CH3 )2 ] (thiram), affording unusual dimer [(CH3 )2 NCS2 Ru(η(5) -C5 H4 )(η(3) -C5 H4 )C2 H4 ]2 [B(C6 F5 )4 ]2 (9) through a haptotropic η(5) -η(3) ring-slippage followed by an apparent [2+2] cyclodimerization of the cyclopentadienyl ligand. Analogs of possible intermediates in the reaction pathway [C6 H5 ERu(η(5) -C5 H4 )2 C2 H4 ][B(C6 F5 )4 ] [E=S (15) or Se (16)] were synthesized through reaction of 8 with C6 H5 EEC6 H5 (E=S or Se).
authors.affiliation: School of Chemistry, University of Bristol, Bristol, BS8 1TS (UK).
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Russell
authors.forename: Joe B
authors.initials: JB
authors.lastname: Gilroy
authors.forename: Kevin
authors.initials: K
authors.lastname: Lam
authors.forename: Mairi F
authors.initials: MF
authors.lastname: Haddow
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Harvey
authors.forename: William E
authors.initials: WE
authors.lastname: Geiger
authors.forename: Ian
authors.initials: I
authors.lastname: Manners
keywords: electron-transfer reactions; organometallic chemistry; ruthenium