Syntheses and crystal structures of geometrical isomeric pairs: Trans- and cis-(PPh4) [Co(acac)2(CN)2] and trans- and cis-[Co(acac)2(PMe3 or PEt3)2]PF6 (acac = pentane-2,4-dionate)

Takayoshi Suzuki, Kazuo Kashiwabara, Masakazu Kita, Junnosuke Fujita, Sumio Kaizaki

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Reactions of trans-[Co(acac)2(PPh3)2]PF6 (acac = pentane-2,4-dionate) with NaCN and with PR3 (R = Me or Et) in methanol afforded new complexes, trans-(PPh4) [Co(acac)2(CN)2] and trans-[Co(acac)2(PR3)2]PF6, respectively. The structures of the new trans-isomers, together with those of the corresponding known cis-isomers, were determined by single-crystal X-ray diffraction. Complexes trans[Co(acac)2(PR3)2]+ were stable in dry organic solvents, but in wet methanol easily hydrolysed to give trans-[Co(acac)2(PR3) (H2O)] + and isomerized to cis-[Co(acac)2(PR3)2]+ by the addition of a catalytic amount of active charcoal. In contrast, trans- and cis-[Co(acac)2(CN)2]- and cis-[Co(acac)2(PR3)2]+ were stable in both dry and wet solvents. The X-ray structure analyses showed that the Co-C and Co-P bonds in the trans-isomers were longer by about 0.07 and 0.08 Å, respectively, than those of the corresponding cis-isomers. The Co-O bonds trans to cyanide and phosphine ligands were also longer than those of the mutually trans Co-O bonds, owing to the strong trans influences of cyanide and phosphine ligands.

Original languageEnglish
Pages (from-to)77-84
Number of pages8
JournalInorganica Chimica Acta
Issue number1
Publication statusPublished - Oct 30 1998
Externally publishedYes


  • Cobalt complexes
  • Crystal structures
  • Cyanide complexes
  • Phosphine complexes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry


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