Six novel Pt–Rh dinuclear complexes (1–6), [PtRh(PVM)2(NH3)2Cl3]·4H2O (1, PVM = tBuCONH–), [PtRh(PVM)2(en)Cl3]·3H2O (2, en = ethylenediamine), [PtRh(PVM)2(NH2CH3)2Cl3]·3H2O (3), [PtRh(PVM)2(NH2tBu)2Cl3]·3H2O (4), [PtRh(TCM)2(NH3)2Cl3] (5, TCM = Cl3CCONH–), and [PtRh(BZM)2(NH3)2Cl3]·H2O (6, BZM = PhCONH–), have been synthesized from Pt mononuclear complexes having nitrogen‐coordinated amidate ligands with noncoordinated amidate oxygen atoms. X‐ray analysis revealed that compounds 1 and 2 form zigzag one‐dimensional chains in the form [–Pt–Rh–Cl–]n. The oxidation states of the metal ions have been determined by X‐ray photoelectron spectroscopy (XPS) and 195Pt NMR spectroscopic analysis, and are Pt(+2, d8)···Rh(+3, d6). In comparison with the Pt–Rh distances found in the literature, it has become apparent that the Pt–Rh dinuclear complexes have a dative Pt(d8)→Rh(d6) bond, where the Pt d orbital is stabilized by the overlap with the d orbital of the Rh atom. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The quasi-one-dimensional chain [{PtRh(TCM)(2)(NH(3))(2)Cl(2.5)}(2){Pt(2)(PVM)(2)(NH(3))(4)}(2)](n)(PF(6))(6n).2nH(2)O (Chain-2; TCM = Cl(3)CCONH(-), PVM = (t)BuCONH(-)), 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(2)O (1) and [PtRh(TCM)(2)(NH(3))(2)Cl(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(6)Rh(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(6)Rh(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 (delta* orbitals in Pt-Rh dinuclear parts) and hops from one Rh atom to another.

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In this manuscript we review the structure of the novel 1-D chain complex, {[PtRh(PVM) 2 (NH 3 ) 2 Cl 2.5 ] 2 [Pt 2 (PVM) 2 (NH 3 ) 4 ] 2 (PF 6 ) 6 Á 2MeOH Á 2H 2 O} n (4) (PVM ¼ pivalamidate), consisting of mixed-valence dimeric complexes with appreciably extended metal-metal bondings. Compound 4 is made up of octameric segments, each of which consists of two platinum-rhodium dinuclear complexes and a tetrameric platinum unit. The charge of 19+ for the Pt 6 Rh 2 octameric segment in 4 was deduced from the number of the independent PF 6 À counter ions, and is the supporting evidence for one unpaired electron per one octameric segment. The tetrameric platinum unit in 4 is the structural motif that is observed in [Pt 2 (PVM) 2 (NH 3 ) 4 ](PF 6 ) 2 Á H 2 O (2) and [Pt 4 (PVM) 4 (NH 3 ) 8 ](PF 6 ) 4 (ClO 4 ) Á 2H 2 O (3 ¼ ''platinum blue'' with one electron delocalized over the four platinum atoms). On the basis of the EPR, magnetic susceptibility, and electrical conductivity results, the nature of the unpaired electron in 4 is discussed. r