Consanguineous Families of Coordinated Carbon: A ReC4Re Assembly That Is Isolable in Three Oxidation States, Including Crystallographically Characterized ReC⋮CC⋮CRe and +ReCCCCRe+ Adducts and a Radical Cation in Which Charge Is Delocalized between Rhenium Termini Academic Article uri icon

abstract

  • Reaction of (η5-C5Me5)Re(NO)(PPh3)(C ≡ CH) and Cu(OAc)2 (1.5 equiv, 80 °C, pyridine) gives the orange-brown ReC4Re complex (η5-C5Me5)Re(NO)(PPh3)(C ≡ CC ≡ C)(Ph3P)(ON)Re(η5-C5Me5) (2, 88%) as a 50:50 diastereomer mixture. Crystallization affords (SS,RR)-2 · 2CH2Cl2 and solutions enriched in (SR,RS)-2 (meso). Addition of Ag+PF6- (≤ 2 equiv) yields deep blue (SS,RR)- and (SR,RS)-22+2PF6- (86%), which give two geometric isomers (62:38, 89:11; CD2Cl2, -93 °C) about the +Re = C = C = C = C = Re+ linkages. Crystal structures of (SS,RR)-2 · 2CH2Cl2 and (SS,RR)-22+2PF6- show ReC4Re units with bond angles (169-178°) and lengths (C ≡ C, 1.202(7); C-C 1.398(5); C = C 1.260-1.305(10) Å) near those of butadiyne or cumulenes. Natural bond order analysis and topological electron density calculations confirm the valence formulations. Reactions of (SS,RR)-2 with (SS,RR)-22+2PF6- or Ag+PF6- (1 equiv) give a green radical cation (SS,RR)-2.+PF6- (μ = 1.74 μ(B); Faraday method). E°data yield a K(c) value of 1.1 x 109 (CH2Cl2, 22.5 °C) for the comproportionation. ESR spectra show undecets with A(iso,Re) values (98 G) half those of related monorhenium radical cations, indicating spin delocalization over two rheniums (I = 5/2). Accordingly, IR spectra give only one υ(NO) band, positioned between those of 2 and 22+2PF6- (CH2Cl2, 1665 vs 1623/1719 cm-1). Near IR spectra show unique solvent-independent bands (883, 1000, 1200 nm; ε 15000, 9400, 3200 M-1 cm-1). Sodium naphthalenide reduces (SS,RR)- or (SR,RS)-2.+PF6- to (SS,RR)- or (SR,RS)-2, establishing configurational stability. These and related data are analyzed in detail.

author list (cited authors)

  • Brady, M., Weng, W., Zhou, Y., Seyler, J. W., Amoroso, A. J., Arif, A. M., ... Gladysz, J. A.

publication date

  • January 1, 1997 11:11 AM