Rhodium-rhodium interactions in [Rh(β-diketonato)(CO)2] complexes

Abstract

The solid state single crystal structures of [Rh(β-diketonato)(CO)2], where β-diketonato = (R1COCHCOR2)−, with R1, R2 = CF3, C4H3S (1), C4H3S, C4H3S (2), Ph, C4H3S (3) and CF3, Ph (4), show that these complexes in some cases form dinuclear units, which stack in chains with weak metallophilic rhodium-rhodium interactions, while in other cases they produce continuous polymeric units, with equal intermolecular Rh⋯Rh distances. Different solid state structural data is reported herein for these four complexes, including a low temperature comparison with ambient data for (4). In the latter case, weak intermolecular halogen bonding has also been identified, which additionally contributes to the stability of (4) in the solid state. Computational evaluation of the frontier molecular orbitals of both dinuclear and tetranuclear models of complexes (1)–(4), show Rh(dz2)-Rh(dz2) σ bonding and σ* anti-bonding orbitals. An NBO analysis of the dinuclear units, revealed a donor-acceptor interaction between the two rhodium atoms in such a unit, while a QTAIM study identified a bonding path between the two rhodium atoms therein.