Complexes comprising 'dangling' phosphorus arms and tri(hetero)metallic butenynyl moieties

Trans-RuCl2(PP3)2 (1a) (PP3 = tris[2-(diphenylphosphino)ethyl]phosphine) was prepared by reaction of RuCl2(PPh3)3 with 2 eq. PP3. Through coordination of two potentially tetradentate ligands in a bidentate arrangement, four uncoordinated phosphine moieties remain readily available for subsequent reaction. This is demonstrated through their facile oxidation with hydrogen peroxide, providing trans-RuCl2(PP[PO]2)2 (1b) (PP[PO]2 = bis[2-(diphenylphosphine oxide)ethyl][2-(diphenylphosphino)ethyl]phosphine). Whilst chloride abstraction reactions from 1a appear slow (typical for trans dichlorides), cis-RuCl2(PP3) is shown to react rapidly with ethynylferrocene under ‘Dixneuf’ conditions (CH2Cl2, NaPF6, NEt3), providing the tri(hetero)metallic butenynyl complex [(PP3)Ru(η3–FcC3CHFc)]PF6 (2, Fc = ferrocenyl). The pendant groups of 1a-b offer great potential for future coordination studies (for example, to prepare mixed transition metal/lanthanide materials), whereby the facile synthetic route to 2 suggests a path towards examination of complex mixed-valence systems comprising multiple redox-active centres.