Nitrido-complexes of rhenium which contain tertiary phosphines, and attempts to prepare their osmium analogues

Abstract

The preparation of nitrido-complexes of type [ReNCl₂(PR₃)_n](PR₃= tertiary phosphine, n= 2 or 3) with azide as a source of nitride ion offers no improvement over the use of hydrazine dihydrochloride, which we use here to prepare a number of new analogues. The value of n appears to depend mainly on the steric requirements of the phosphine. Bond length and i.r. spectra data suggest that the ReN bond is weaker than the ReNR bond, a phenomenon which can be correlated with the increased strength of the CN bond upon the co-ordination of organic nitriles. Initial attempts to use the hydrazine dihydrochloride method to prepare nitrido–osmium complexes containing tertiary phosphines have led to the preparation of an ammine [OsCl₃(NH₃)(PPh₃)₂] and of oxo-complexes [OsOX₃(PPh₃)₂](X = Cl or Br). Some azido-complexes of iridium and rhodium were also characterised.