Rhenium(v) in combination with tertiary phosphines as ligands has a strong tendency to form multiple bonds to nitrogen. Three new series of complexes containing such bonds, of the types [ReX,(NAr) (PRJJ, [ReNX,(PR,),], and [ReNX,(PR,),] (X = halogen, Ar = aryl, R = alkyl or aryl), are described. Imido-complexes are obtained by the reaction of the arylamine on the complexes [ReOX,(PR,),] or [ReOX,(OEt) (PR,),], and the nitrido complexes by hydrazine dihydrochloride reduction of potassium per-rhenate in the presence of the phosphine. The dipole moments, configurations, and structures of the new compounds are discussed, RHENIUM(V) HALIDES in combination with tertiary phosphines have a strong tendency to form stable multiple bonds to atoms, such as oxygen and nitrogen, in the groupings Re=O and Re=NPh.l Dipole moments show the Re=O and Re=NPh bonds to have considerable triple-bond character and may be represented Re + 0 and Re NPh, the arrows representing the drift of &electrons from the ligand into d-orbitals of the metal. The high bond order of the Re=O bond is also demonstrated by its length of 1-60 A, as compared with 1.87 A in [ReO2(CN),I2-.
Some complexes of diethylphenylphosphine and triphenylphosphine, of the type [ReX,(PR,),] (X = C1 or Br), have been prepared by (a) oxidation of complexes of the type [ReX,(PR,),] by X,, (b) pyrolysis of the salts [PHR,],[ReX,], or (c) reduction of [ReOX,(PR,),] in HX. The " violet complex " obtained by the interaction of per-rhenates, diethylphenylphosphine, and hydrochloric acid in boiling ethanol is shown to be a solid solution of some 15% of trans-[ReCl,(PEt,Ph),] in trans- [ReOCl,(PEt,Ph),] . Ligand displacement provides a convenient preparation of the otherwise difficult to obtain trialkyl-and tertiary alkaryl-phosphine and -arsine complexes of the type [ReOCl,(MR,),] (M = P or As) from the readily available trans- [ReOCl,(PPh,) Recently, in describing a number of complexes of tertiary phosphines with rhenium(v) , rhenium(m), and rhenium(n), we mentioned a mysterious violet complex to which we were unable to assign a formula, but we tentatively suggested it might be [Re(OH)C1,(PEt,Ph)2].1 It was obtained together with cis-and trarts-[ReOCI,(PEt,Ph),] by the interaction of per-rhenates, diethylphenylphosphine, and hydrochloric acid in boiling ethanol. We now find that this complex is a solid solution of 10-22% of a new, intensely violet, complex, trans-[ReCI,(PEt,Ph),], in green trarts- [ReOCI,(PEt,Ph),]. Here we describe this tetrachlorocomplex and related complexes of rhenium@), all of which are strongly coloured [(I), (11), and (111); Table 11, and also an improved method of obtaining some complexes of the types cis-and trans-[ReOCl,L,] by ligand displacement from the readily available trans-[ Re0 C1, ( P P h,) , I .
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