Development of Multinuclear Metal Systems Structurally Constrained by Linear Polyphosphines

Abstract

Structurally constrained multinuclear transition metal assemblies are fascinating building blocks for atomically precise nanostructured molecular devices due to a variety of functions with electronic, magnetic, photophysical, and catalytic properties originating from cooperative effects of proximate metal centers. Their viable syntheses are in debt to design of multidentate supporting ligands, and to develop low valent metal assemblies as molecular miniatures of metallic materials, those with a pair of soft donors connected by a single atom are highly desired. The authorʼs group synthesized a series of linear polyphosphine ligands with short bite distances, and has systematically studied such multinuclear metal clusters. This review describes the recent developments of low-valent metal clusters supported by linear tri-, tetra- and hexadentate phosphine ligands, Ph₂PCH₂[P(Ph)CH₂]_nPPh₂ (n = 1, 2, 4), Ph₂PCH₂P(Ph) [CH₂]_mP(Ph)CH₂PPh₂ (m = 1-4), and Ph₂PCH₂P(Ph) N(Ph)P(Ph)CH₂PPh₂, mainly focusing on self-aligned Pt₆, Pt₂Pd₂Pt₂, Pd₈ chains, strongly luminous Au₄ and Au₆ chains and {Au₂AgCu}₂ rings, and trigonal, rhombic, square planar, and cage-type copper hydride clusters with their reactivity and catalytic activity.