Coinage Metal Complexes Supported by the Tri- and Tetraphosphine Ligands

Abstract

A series of tri- and tetranuclear phosphine complexes of d¹⁰ metal ions supported by the polydentate ligands, bis­(diphenylphosphinomethyl)­phenylphosphine (<i>PPP</i>) and tris­(diphenylphosphinomethyl)­phosphine (<i>PPPP</i>), were synthesized. All the compounds under study, [AuM₂(<i>PPP</i>)₂]³⁺ (M = Au (<b>1</b>), Cu (<b>2</b>), Ag (<b>3</b>)), [M₄(<i>PPPP</i>)₂]⁴⁺ (M = Ag (<b>4</b>), Au (<b>5</b>)), [AuAg₃(<i>PPPP</i>)₂]⁴⁺ (<b>6</b>), and [Au₂Cu₂(<i>PPPP</i>)₂(NCMe)₄]⁴⁺ (<b>7</b>), were characterized crystallographically. The trinuclear clusters <b>1</b>–<b>3</b> contain a linear metal core, while in the isostructural tetranuclear complexes <b>4</b>–<b>6</b> the metal framework has a plane star-shaped arrangement. Cluster <b>7</b> adopts a structural motif that involves a digold unit bridged by two arms of the <i>PPPP</i> phosphines and decorated two spatially separated Cu^I ions chelated by the remaining P donors. The NMR spectroscopic investigation in DMSO solution revealed the heterometallic clusters <b>2</b>, <b>3</b>, and <b>6</b> are stereochemically nonrigid and undergo reversible metal ions redistribution between several species, accompanied by their solvation–desolvation. The complexes <b>1</b>–<b>3</b> and <b>5</b>–<b>7</b> exhibit room temperature luminescence in the solid state (Φ_em = 6–64%) in the spectral region from 450 to 563 nm. The phosphorescence observed originates from the triplet excited states, determined by the metal cluster-centered d_σ* → p_σ transitions