Synthesis, crystal structure, and characterization of a heterometallic one-dimensional complex with metal-metal bonds

摘要

The quasi-one-dimensional chain [{PtRh(TCM)_2(NH _3)_2Cl_2._5}_2{Pt_2(PVM) _2(NH_3)_4}_2]_n(PF _6)_(6n)·2nH_2O (Chain-2; TCM = Cl _3CCONH-, PVM = ~tBuCONH-), which consists of Pt and Rh atoms, has been obtained from two dinuclear compounds, [Pt_2(PVM)_2(NH_3)_4](PF _6)_2·H_2O (1) and [PtRh(TCM) _2(NH_3)_2Cl_3] (2). Single-crystal X-ray analysis showed that the dinuclear compounds stack with metal-metal bonds to form octameric units, Pt-Rh-Pt-Pt-Pt-Pt-Rh-Pt (Pt_6Rh_2), that are bridged by the Cl~- ion to be a quasi-one-dimensional chain. Elemental analysis, X-ray photoelectron spectroscopy, electron paramagnetic resonance (EPR), and magnetic susceptibility measurements showed that Chain-2 has a mixed valency and one unpaired electron per octameric Pt _6Rh_2 unit. Taking into account the small observed g _(av) value (g_(av) = 2.01 at room temperature) obtained by EPR measurement and B3LYP density functional theory calculations of the model complex, oxidation states of the octameric unit are postulated to be Pt ~(3+)-Rh~(2.5+)-Pt~(2+)-Pt~(2+)-Pt ~(2+)-Pt~(2+)-Rh~(2.5+)-Pt~(3+), where the EPR isotropic signal showed that the unpaired electron resides in the Rh d _(xy) orbitals (Δ* orbitals in Pt-Rh dinuclear parts) and hops from one Rh atom to another.