Dinuclear Rh(I) complex with 2,7-bis(diphenylphosphino)-1,8-naphthyridine: Synthesis, structure, and dynamic property

Abstract

Reaction of [RhCl(cod)] 2 with 2,7-bis(diphenylphosphino)-1,8-naphthyridine (dpnapy) and 2,6-xylyl isocyanide (XylNC) in the presence of NH 4PF 6 afforded the dirhodium(I) complex, [Rh 2(μ-dpnapy) 2(XylNC) 4](PF 6) 2 ( 5), and similar procedures using [MCl 2(cod)] (M = Pt, Pd) resulted in the formation of [Pt 2(μ-dpnapy) 2(XylNC) 4](PF 6) 4 ( 6) and [Pd 2Cl 2(μ-dpnapy) 2(XylNC) 2](PF 6) 2 ( 7). Complexes 5– 7 were characterized by elemental analysis, IR, UV–Vis, 1H and 31P{ 1H} NMR, and ESI mass spectroscopic techniques, to involve a small and rigid d 8 {M 2(μ-dpnapy) 2} metallomacrocycle. Complex 5 readily incorporated a silver(I) ion into the macrocycle to afford [Rh 2Ag(μ-dpnapy) 2(XylNC) 4](PF 6) 3 ( 8) which was characterized by X-ray crystallography. The Ag(I) ion is trapped by two trans N atoms of dpnapy ligands, resulting in an asymmetric Rh–Ag⋯Rh structure, determined as a disordered model in the crystal structure, and however, in a CH 2Cl 2 solution, a dynamic interconversion of the two Ag-trapped sites was observed with low-temperature NMR studies, which was further supported by DFT molecular orbital calculations. When an acetonitrile solution of complex 5 was treated over a droplet of mercury(0), the polymeric compound formulated as {[Rh(μ-dpnapy)(XylNC) 2](PF 6)} n ( 9) was isolated as yellow single crystals, which were revealed by X-ray crystallography to consist of C 6 helical rods along c axis with a pitch of 33.5 Å (rise of unit = 5.6 Å) and a diameter of 20.64 Å.