Alloyed Tetranuclear Metal Chains of Pd 4− n Pt n ( n= 0–3) Scaffolded by a New Linear Tetraphosphine Containing a PNP Bridge

Mixed-Valence Tetrametallic Iridium Chains

Neutral [X-{Ir2 }-{Ir2 }-X] (X=Cl, Br, SCN, I) and dicationic [L-{Ir2 }-{Ir2 }-L]2+ (L=MeCN, Me2 CO) tetrametallic iridium chains made by connecting two dinuclear {Ir2 } units ({Ir2 }=[Ir2 (μ-OPy)2 (CO)4 ], OPy=2-pyridonate) by an iridium-iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain. While the axial ligands do not significantly affect the metal-metal bond lengths, the metallic chain has a significant impact on the iridium-L/X bond distances. The complexes show free rotation around the unsupported iridium-iridium bond in solution, with a low-energy transition state for the chloride chain. The absorption spectra of these complexes show characteristic bands at 438-504 nm, which can be fine-tuned by varying the terminal capping ligands.

Aiming for dynamic behaviours of molecular metal chains

The dynamical functions of molecular metal chains, that could be derived from unique physical and chemical properties coupled with self-assembly of metal chain components, have largely been unexplored, and this review paper focuses on the dynamic behaviours of Pd chains supported by linear tetraphosphines, meso- and rac-Ph₂PCH₂P(Ph)CH₂P(Ph)CH₂PPh₂ recently reported, and the current development on fine-tuning of metal chains by introducing heterometal atoms, i.e. heterometallic molecular metal chains, that are considered as promising dynamical components in the next generation.

Heterometallic bond activation enabled by unsymmetrical ligand scaffolds: bridging the opposites

Heterobi- and multimetallic complexes providing close proximity between several metal centers serve as active species in artificial and enzymatic catalysis, and in model systems, showing unique modes of metal-metal cooperative bond activation. Through the rational design of well-defined, unsymmetrical ligand scaffolds, we create a convenient approach to support the assembly of heterometallic species in a well-defined and site-specific manner, preventing them from scrambling and dissociation. In this perspective, we will outline general strategies for the design of unsymmetrical ligands to support heterobi- and multimetallic complexes that show reactivity in various types of heterometallic cooperative bond activation.

Transition Metal Chain Complexes Supported by Soft Donor Assembling Ligands

The chemistry of discrete molecular chains constituted by metals in low oxidation states, displaying metal-metal proximity and stabilized by suitable metal-bridging, assembling ligands comprising at least one soft donor atom is comprehensively reviewed; complexes with a single (hard or soft) bridging atom (e.g., μ-halide, μ-sulfide, or μ-PR₂ etc.) as well as "closed" metal arrays (that fall in the realm of cluster chemistry) are excluded. The focus is on transition metal-based systems, with few excursions to cases combining transition and post-transition elements. Most relevant supporting ligands have neutral C, P, O, or S donor (mainly, N-heterocyclic carbene, phosphine, ether, thioether) or anionic donor (mainly phenyl, ylide, silyl, phosphide, thiolate) groups. A supporting-ligand-based classification of the metal chains is introduced, using as the classifying parameter the number of "bites" (i.e., ligand bridges) subtending each intermetallic separation. The ligands are further grouped according to the number of donor atoms interacting with the metal chain (called denticity in the following) and the column of the Periodic Table to which the set of donor atoms belongs (in ascending order). A complementary metal-based compilation of the complexes discussed is also provided in a concise tabular form.

The Discrete Breast Cancer Stem Cell Mammosphere Activity of Group 10-Bis(azadiphosphine) Metal Complexes

We report the anti-breast cancer stem cell (CSC) properties of a series of Group 10-bis(azadiphosphine) complexes 1-3 under exclusively three-dimensional cell culture conditions. The breast CSC mammosphere potency of 1-3 is dependent on the Group 10 metal present, increasing in the following order: 1 (nickel complex) <2 (palladium complex) <3 (platinum complex). Notably, 3 reduces the formation and size of mammospheres to a greater extent than salinomycin, an established CSC-active compound, or any reported anti-CSC metal complex tested under similar conditions. Mechanistic studies suggest that the most effective complexes 2 and 3 readily penetrate CSC mammospheres, enter CSC nuclei, induce genomic DNA damage, and trigger caspase-dependent apoptosis. To the best of our knowledge, this is the first study to systematically probe the anti-CSC activity of a series of structurally related Group 10 complexes and to be conducted entirely using three-dimensional CSC culture conditions.

A new series of heteronuclear metal strings, MRhRh(dpa)4Cl2 and MRhRhM(dpa)4X2, from the reactions of Rh2(dpa)4 with metal ions of group 7 to group 12

A new series of trinuclear and tetranuclear HMSCs, MRhRh(dpa)₄Cl₂ and MRhRhM(dpa)₄X₂, from the reactions of Rh₂(dpa)₄ and metal ions were synthesized.

Structure and magnetic properties of a novel heteroheptanuclear metal string complex [Ni3Ru2Ni2(μ7-teptra)4(NCS)2](PF6)

We report the synthesis of a novel heteroheptanuclear metal string complex (HMSC) [Ni₃Ru₂Ni₂(μ₇-teptra)₄(NCS)₂](PF₆) 1 supported by tetra-pyridyl-tri-amine (H₃teptra) ligands. We employed X-ray diffraction and other spectroscopic techniques to characterize the complex. The observed remarkably short Ru-Ru distance of 2.2499(3) Å for 1 is indicative of a unique metal-metal interaction in the mixed-valence [Ru₂]⁵⁺ (S = 3/2) unit. The complex exhibits a relatively high magnetic moment value of 4.55 B.M. at 4 K, which increases rapidly to 6.00 B.M. at 30 K and remains at 6.11 B.M. from 50 to 300 K as shown by SQUID measurements, indicating a high spin (S≥ 3/2) system which is further supported by the analyses of EPR spectra at low temperatures. These magnetic behaviors can be ascribed to the result of spin-exchange interactions among multi-spin centers.

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.

Paramagnetic One-Dimensional Chain Complex Consisting of Three Kinds of Metallic Species Showing Magnetic Interaction through Metal-Metal Bonds

A heterometallic and paramagnetic one-dimensional (1-D) chain (3) aligned as -Rh(+2)-Rh(+2)-Pt(+2)-Co(+2)-Pt(+2)- with direct metal-metal bonds was obtained by HOMO-LUMO interactions at the σ* (d_z²) orbital between two kinds of complexes. The 1-D chains in 3 have relatively straight backbones because the raw material complexes, [Rh₂(O₂CCH₃)₄] and [Pt₂Co(piam)₄(NH₃)₄], are connected and stacked in a face-to-face fashion, where Co---Co are separated by about 13.3 Å with four different metals. Physical measurements revealed that 3 has a band gap between the σ-type conduction and valence bands, where d-orbitals of the Co ion with three unpaired electrons are laid among them. The magnetic behavior of 3 was investigated and found to be consistent with a complex interaction involving both zero-field splitting and Pauli paramagnetism attributed to band formation superimposed on relatively strong exchange coupling (zJ = -22.2 cm^-1) between two high-spin Co(+2) ions separated by the diamagnetic Pt-Rh-Rh-Pt.