Ruthenate(VI)-catalysed dehydrogenation of primary amines to nitriles, and crystal structures of cis-[Ru(bipy)2(NH2CH2Ph)2][PF6]2·0.5MeOH and cis-[Ru(bipy)2(NCPh)2][PF6]2·CH2Cl2†

Abstract

Catalytic dehydrogenation of benzylic and other primary amines RCH₂NH₂ to the corresponding nitriles RCN by the system trans-[Ru(OH)₂O₃]^2–/S₂O₈^2– has been investigated. The complex cis-[Ru(bipy)₂(NH₂CH₂Ph)₂]²⁺ and the new cis-[Ru(bipy)₂(NH₂CH₂R)₂]²⁺ (R = o-, m- or p-ClC₆H₄, o-MeC₆H₄, o- or p-MeOC₆H₄); cis-[Ru(phen)₂(NH₂CH₂R)₂]²⁺ (R = Ph or p-MeOC₆H₄) and cis-[Os(bipy)₂(NH₂CH₂Ph)₂]²⁺ have been made, and dehydrogenation of the co-ordinated amine in the ruthenium complexes to the corresponding nitriles in cis-[Ru(L–L)₂(NCR)₂]²⁺ (L–L = bipy or phen) by peroxodisulfate demonstrated. The crystal structures of cis-[Ru(bipy)₂(NH₂CH₂Ph)₂][PF₆]·0.5MeOH and cis-[Ru(bipy)₂(NCPh)₂][PF₆]₂·CH₂Cl₂, the latter a product of co-ordinated amine dehydrogenation by peroxodisulfate to give cis-[Ru(bipy)₂(NH₂CH₂Ph)₂]²⁺, were determined. Raman, infrared and ¹H NMR data for the complexes have been measured; the latter suggest that the cis configurations of the amine complexes are retained in solution.