Multinuclear variable-temperature nuclear magnetic resonance study of rhodium carbonyl clusters containing encapsulated heteroatoms: ligand and metal polyhedral rearrangements

Abstract

Variable-temperature multinuclear n.m.r. studies (¹³C, ¹³C-{¹⁰³Rh}, ¹³C-{³¹P}, and ³¹P) are reported for [Rh₉E(CO)₂₁]^2–, [Rh₁₀E(CO)₂₂]^3–(E = P or As), and [Rh₁₂Sb(CO)₂₇]^3–. In all cases, complete fluxionality of both the carbonyl and metal polyhedra are observed at high temperatures, and at low temperatures it has been possible to obtain spectra for the Rh₉ and Rh₁₀ clusters, which are fully consistent with their solid-state structures, thus allowing a complete spectroscopic assignment; the Rh₁₂ cluster is still fluxional in solution at –97 °C.