Synthesis, Crystal Structure, and Characterization of a Heterometallic One-Dimensional Complex with Metal−Metal Bonds

The quasi-one-dimensional chain [{PtRh(TCM)2(NH3)2Cl2.5}2{Pt2(PVM)2(NH3)4}2] n (PF6)6n ·2nH2O (Chain-2; TCM = Cl3CCONH−, PVM = t BuCONH−), which consists of Pt and Rh atoms, has been obtained from two dinuclear compounds, [Pt2(PVM)2(NH3)4](PF6)2·H2O (1) and [PtRh(TCM)2(NH3)2Cl3] (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 (Pt6Rh2), 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 Pt6Rh2 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 Pt3+−Rh2.5+−Pt2+−Pt2+−Pt2+−Pt2+−Rh2.5+−Pt3+, 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.