Cyclometalated Formazan Derivatives of Ruthenium and Osmium: Structure of Ru((o-C6H4)N=NC(Ph)=NNPh) (CO)(PPh3)2

Geoffrey B. Jameson, Alan Muster, Stephen D. Robinson, Jonathan N. Wingfield, James A Ibers

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1,5-Diphenylformazans, PhN=NC(R)=NNHPh (R = H, Me, or Ph), react with the complexes RuH2(CO)(PPh3)3, RuH2(CO)(AsPh3)3, RuHCl(CO)(PPh3)3, Os(O2CCF3)2(CO)(PPh3)2, and OsH(O2CCF3)(CO)(PPh3)2 in boiling 2- methoxyethanol or dimethylformamide over a period of 30 min to 4 h to afford cyclometalated formazan derivatives M((o-C6H4)N=NC(R)=NNPh)(CO)(EPh3)2 (M = Ru, E = P, R = H, Me, or Ph; M = Ru, E = As, R = Ph; = Os, E = P, R = H, Me, or Ph) as deep green, air-stable, crystalline solids. The initial products formed in these reactions appear to be N’,N5-chelate formazan complexes which subsequently rearrange and undergo cyclometalation. Isomeric intermediates of the form Ru(PhN=NCH=NNPh)H(CO)(PPh3)2 have been isolated as pink (ris-PPh3 ligands) or purple (frarw-PPh3 ligands) complexes from the reaction of RuH2(CO)(PPh3)3 with PhN=NCH=NNHPh and have been shown 1-1-1-1 to convert to the green cyclometalated complex Ru((o-C6H4)N=NCH=NNPh)(CO)(PPh3)2 on further heating. The structure of the green complex Ru((o-C6H4)N=NC(Ph)=NNPh)(CO)(PPh3)2 has been established by an X-ray diffraction study. The complex crystallizes in space group C2h5-P21/c (a = 18.539 (3) Å, b = 25.381 (6) Å, c = 19.391 (4) Å, β = 97.36 (1)° at 0 °C) with two pseudosymmetrically related molecules per asymmetric unit. The structure, described by 399 variable parameters, was refined with use of 8498 reflections having F02 > 3σ (F02) to values for R and Rw of 0.081 and 0.107. The compound contains six-coordinated ruthenium(II) bound to a trans pair of triphenylphosphine ligands (average Ru-P = 2.384 (5) Å), a carbonyl group (average Ru-C = 1.83 (1) Å, C-O = 1.17 (1) Å), and a planar, tridentate, cyclometalated formazan ligand coordinated through nitrogen atoms N1 (Ru-N = 2.163 (7) Å) and N4 (Ru-N = 2.02 (1) Å) and the ortho carbon atom of the phenyl ring on the N5 nitrogen atom (Ru-C = 2.091 (9) Å). The bond lengths found for the formazan skeleton are consistent with extensive electron delocalization throughout the chelate rings and the adjoining phenyl groups.

Original languageEnglish (US)
Pages (from-to)2448-2456
Number of pages9
JournalInorganic Chemistry
Issue number8
StatePublished - Jan 1 1981

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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