Thiolate-Thione Redox-Active Ligand with a Six-Membered Chelate Ring via Template Condensation and Its Pt(II) Complexes

A new template condensation reaction has been discovered in a mixture of Pt(II), thiobenzamide, and base. Four complexes of the general form [Pt(ctaPh^R)₂], R = CH₃ (1a), H (1b), F (1c), Cl (1d), cta = condensed thioamide, have been prepared under similar conditions and thoroughly characterized by ¹H NMR and UV-vis-NIR spectroscopy, (spectro)electrochemistry, elemental analysis, and single-crystal X-ray diffraction. The ligand is redox active and can be reduced from the initial monoanion to a dianionic and then trianionic state. Chemical reduction of 1a with [Cp₂Co] yielded [Cp₂Co]₂[Pt(ctaPh^CH3)₂], [Cp₂Co]₂[1a], which has been similarly characterized with the addition of EPR spectroscopy and SQUID magnetization. The singly reduced form containing [1a]^1-, (nBu₄N)[Pt(ctaPh^CH3)₂], has been generated in situ and characterized by UV-vis and EPR spectroscopies. DFT studies of 1b, [1b]^1-, and [1b]^2- confirm the location of additional electrons in exclusively ligand-based orbitals. A detailed analysis of this redox-active ligand, with emphasis on the characteristics that favor noninnocent behavior in six-membered chelate rings, is included.

Structures and paramagnetism of five heterometallic pentanuclear metal strings containing as many as four different metals: NiPtCo2Pd(tpda)4Cl2

Five heterometallic pentanuclear metal strings were prepared by stepwise synthesis from two to three and four kinds of metals aligned in one chain. In particular, NiPtCo2Pd(tpda)4Cl2 (5) possesses four different metals, and the SQUID measurement shows that Ni2+ is the only magnetically active center. Besides, the shortest Co(ii)-Co(ii) single bond (2.105(9) Å), so far, is reported.

Band Structures of Quasi-One-Dimensional Incommensurate Helical Systems: A Case Study of Infinite Chromium Extended Metal Atom Chain

Extended metal atom chains (EMACs) are promising candidates for molecular wires but their band structures remain to be explored. As a quasi-one-dimensional (Q1D) system, the incommensurate helical nature of EMACs hinders such calculations. In this work, we resolved this issue via explicit implementation of helical symmetry. Moreover, the pattern of metal d bands was rationalized by a systematic investigation on a series of related Q1D helical systems. Two critical factors, helical ligand field and chemically asymmetric ligand field, are proposed and identified. We found that the symmetry and ligand fields of the system dominate the pattern of the metal d bands, instead of specific chemical composition of ligands. The presented method and rationale are applicable to not only EMACs but also related Q1D helical systems.

One-dimensional complexes extended by unbridged metal-metal bonds based on a HOMO-LUMO interaction at the dz2 orbital between platinum and heterometal atoms

In this review, the crystal structures of seventeen heterometallic one-dimensional compounds 1-17 are shown, and their electronic structures are discussed based on the diffuse reflectance spectra and other physical measurements. Compounds 1-17 comprise two kinds of complexes with HOMO-LUMO interactions at σ-type (d_z²) orbitals between platinum and heterometal atoms, where two or three kinds of metal are regularly aligned through metal-metal bonds. In [{PtRh(piam)₂(NH₃)₂Cl_2.5}₂{Pt₂(piam)₂(NH₃)₄}₂]_n(PF₆)_6n·2nMeOH·2nH₂O (3, piam = pivalamidate), the platinum and rhodium atoms are aligned as -Pt-Rh-Pt-Pt-Pt-Pt-Rh-Pt-Cl- with a mixed valence, where an unpaired electron hops from one Rh atom to another. [{Rh₂(O₂CCF₃)₄}{Pt₂(piam)₂(NH₃)₄}₂]_n(CF₃CO₂)_4n·2nEtOH·2nH₂O (6) with -Pt-Pt-Rh-Rh-Pt-Pt- alignment has a conduction band (CB) and a valence band (VB) attributed to σ-type orbitals, exhibiting narrower gaps between CB and VB than other analogues. [{Ru₂(O₂CCH₃)₄}{Pt₂(piam)₂(NH₃)₄}₂]_n(PF₆)_4n·4nH₂O (14) with -Pt-Pt-Ru-Ru-Pt-Pt- and [{Rh₂(O₂CCH₃)₄}{Pt₂Cu(piam)₄(NH₃)₄}]_n(PF₆)_2n (15) with -Rh-Rh-Pt-Cu-Pt- are paramagnetic chains, where one or two unpaired electrons reside at each metal per repeating unit. Thus, this system is diverse in modulating the electronic structures, band structures and the expected physical properties based on the unique oxidation states and redox properties attributed to the metal-metal interaction.