A Novel Coordination Mode of the Fulvalene Ligand in Binuclear Ruthenium Complexes. Synthesis, Structure, and Some Reactivities of [(η⁵-Cp)Ru(μ₂-η⁶:η⁶-C₁₀H₈)Ru(η⁵-Cp)](BF₄)₂

Abstract

The reaction of biruthenocene with excess p-benzoquinone and boron trifluoride-diethyl ether produced the title complex (1) in good yield. Singlecrystal X-ray analysis revealed that 1 is the Rufulvalene complex with the novel coordination mode µ 2 -η 6 :η 6 . The reaction of 1 with BrThe fulvalene (abbreviated as Fv) ligand is interesting because it provides the possibility of the simultaneous coordination of two metals. Thus, many M-Fv complexes have been reported. 1-6 In M-Fv complexes reported to date, two coordination modes have been found; one is the µ 2 -η 5 :η 5 form, which is the most typical, and the other is the µ 2 -η 4 :η 4 form, found in [Fe 2 Fv-(CO) 6 ] 2+ and related cations. 7,8 Here, we report the synthesis and structure of the Ru-Fv complex 1, which contains a third type of coordination mode (µ 2 -η 6 :η 6 ) for the Fv ligand. Reactions of 1 with Br 2 or PPh 3 are also described. 9 When a benzene-hexane solution containing BF 3 ‚ Et 2 O was added to a solution of biruthenocene (abbreviated as RcRc) and p-benzoquinone in benzene, a black precipitate was obtained immediately. 10 Recrystallization of the precipitate from nitromethane-diethyl ether gave well-formed orange-yellow crystals of 1. The 1 H NMR spectrum of 1 in CD 3 NO 2 showed signals assigned to the Cp ligand at δ 5.79 (s) and two triplets due to the Fv ligand at δ 6.82 (t) and 4.96 (t). The signal pattern suggests a symmetric structure for the molecule and is quite different from that of the mixed-valence (Ru II Ru IV ) biruthenocenium cation, formulated as [CpRu IIFvRu IV CpL] 2+ (L ) CH 3 CN, C 2 H 5 CN). 10 The remarkable difference of the chemical shift between the R-and -protons of the Fv ligand suggests that the Fv ligand is coordinated in an unusual manner. The 13 C NMR spectrum of 1 showed four signals at δ 89.7, 95.7, 87.0, and 74.8, which are assigned to the Cp ligand, the Fv ligand, and the ipso carbon of the Fv ligand, respec- † Saitama University.

Synthesis and Some Properties of Bis(ruthenocenyl)thiophene Derivatives – Possible Spin‐Coupling in the Two‐Electron Oxidized Species of Dinuclear Ruthenocenes Bridged by Thiophene Derivatives

“…Similarly, the 1 H NMR spectrum of 11 in CD 3 CN shows the presence of mixed-valence complex 12. This type of conversion has been reported for the dissolution of the twoelectron oxidized species of biruthenocene in CD 3 CN, [11] but has not been observed for the oxidized species of the dinuclear ruthenocenes bridged by oligoenes and oligoynes in CD 3 CN. [12,13] This difference may be due to the level of stability of the fulvene complex-type structure.…”

“…The cyclic voltammograms for these complexes exhibited the one-step twoelectron redox waves in a lower potential region, contrary to those for derivatives bridged by benzenoid aromatics. [11] This finding is probably related to increases in the electronrich and olefinic properties of the thiophene derivatives. The stability levels and structures of the two-electron oxidized species were found to be mainly dependent on the types of bridging thiophene derivatives.…”

“…For example, biruthenocene undergoes one-step two-electron oxidation to afford the dicationic complex that possesses a uniquely coordinated fulvalene as a result of structural isomerization caused by spin-coupling. [11] Bis(ruthenocenyl)oligoenes are oxidized reversibly by the one-step two-electron redox process to afford stable dicationic bis(fulvene)-type complexes. [12] The spin coupling that leads to this structural isomerization is maintained despite the length of the conjugation, at least up to the tetraene derivatives.…”

Coordination complexes of aryl- and alkylphosphonium cyclopentadienylides (cyclopentadienylidene ylides), C5R4PR′R′′R′′′ (R=H, alkyl, aryl; R′, R′′, R′′′=alkyl, aryl)

“…41 was formed as the major product (87%) [58]. The X-ray crystal structure confirmed the ylide structure, the P-C 5 bond length of 1.769(3)Å being longer than in C 5 H 4 PPh 3 but shorter than a P-C single bond.…”

“…The X-ray crystal structure confirmed the ylide structure, the P-C 5 bond length of 1.769(3)Å being longer than in C 5 H 4 PPh 3 but shorter than a P-C single bond. The 31 P NMR resonance was observed at δ 25.08, in the region expected for the coordination complex of C 5 H 4 PPh 3 [58] although, again, there was no parallel made with known Ramirez ylide-types of compounds.…”