The dominant steric effect in the synthesis of ammine hydrido- and chlorido-Ru(II)-N,N-dimethylhydrazine and mixed alkyl-aryl phosphine complexes: Novel methyldiazene reduction intermediates

Novel cationic hydrido complexes [RuH(1,5-cod)(NH₃)(NH₂NMe₂)₂](X) (X = PF₆, BPh₄) and chlorido-ammine complexes [RuCl(1,5-cod)(NH₃)₂(NH₂NMe₂)](X) (X = PF₆, BPh₄), were isolated from the reaction of the polymeric [RuCl₂(1,5-cod)]_x with NH₂NMe₂. Reaction of the hydrido complexes with the phosphine ligands PMe₃, PMe₂Ph, P(OMe)₂Ph resulted in the formation of monohydrido-phosphine complexes, whereas reaction with the bulkier PMePh₂ ligand gave dihydrido-phosphine complexes. Similar reactions of the chlorido-ammine complexes with the phosphine ligands PMe₃, PMe₂Ph, P(OMe)₂Ph, and PMePh₂ all sequentially substituted the NH₂NMe₂ and the 1,5-cod ligands to give the chlorido-ammine phosphine complexes. All complexes were fully characterised and the single crystal X-ray structures were determined for [RuH{P(OMe)₂Ph}₅](BPh₄), [RuH₂(PMePh₂)₄], [{Ru(PMe₂Ph)₃}₂(μ-F)₃](PF₆), fac-[RuCl(NH₃)₂(PMe₂Ph)₃](PF₆), and [RuCl(NH₃)(PMe₂Ph)₄](PF₆). Intramolecular strain between coordinated σ-donor ligands in the Ru(II)-NH₂NMe₂ precursor complexes as well as the relative steric bulk of incoming σ-donor ligands were found to be chemically directing in the formation of monohydrido-, bishydrido-, mono-ammine, and bis-ammine ruthenium(II) complexes.