Aryldiazenato-complexes : synthesis and structure of complexes derived from the oxidative addition of diazonium ions to trans-carbonylchlorobis(triphenylphosphine)iridium(I)

Abstract

Vaska's complexes [IrX(CO)(PPh₃)₂](X = Cl or Br) react with aryldiazonium tetrafluoroborates to form cationic iridium(III) aryldiazenato-complexes of the type [{Ir(X)(N₂Ar)(CO)(PPh₃)₂}_n][BF₄]n, and in the presence of lithium chloride to form the neutral six-co-ordinate complexes [IrXCl(N₂Ar)(CO)(PPh₃)₂]. The presence of the ‘doubly-bent’ aryldiazenato-group (as required by the Ir^IIIoxidation state in an 18 valence-electron complex) has been confirmed by a single crystal X-ray structure determination for [IrCl₂(o-N₂C₆H₄NO₂)(CO)(PPh₃)₂]. Crystals are triclinic, space group P, with Z= 2 in a cell of dimensions: a= 12.202(7), b= 15.441(8), c= 12.762(6)Å, α= 96.41 (3), β= 89.01 (3), γ= 105.09(3)°. The structure was solved by Patterson and Fourier methods and refined by least-squares procedure (1 616 reflections) to R 0.089. Selected dimensions in the aryldiazenato-ligand are Ir–N(1) 2.05(4), N(1)–N(2) 1.19(4), N(2)–C(11) 1.47(5)Å: Ir–N(1)–N(2) 115(3), N(1)–N(2)–C(7) 115(3)°. The aryldiazenato-ligand appears to exert a strong trans-influence, since the chloride trans to it has Ir–Cl(2) 2.48(1)Å, vs. Ir–Cl(1) 2.37(1)Å for the cis-chloride.