A Copper(I)–Arene Complex With an Unsupported η⁶ Interaction

Abstract

Addition of PR 3 (R = Ph or OPh) to [Cu(h 2 -Me 6 C 6 ) 2 ][PF 6 ] results in the formation of [(h 6 -Me 6 C 6 )Cu-(PR 3 )][PF 6 ], the first copper-arene complexes to feature an unsupported h 6 arene interaction. A DFT analysis reveals that the preference for the h 6 binding mode is enforced by the steric clash between the methyl groups of the arene ligand and the phenyl rings of the phosphine co-ligand.

Taming a monomeric [Cu(η6-C6H6)]+ complex with silylene

“…The Cu–C benzene bond distances range from 2.342(9) to 2.477(8) Å, with an average of 2.404 Å, which is longer than those reported for [Cu(η 6 -C 6 Me 6 )] + . 6 Similarly, the distance between the Cu atom and the centroid of the benzene ring (Cu–C centroid 1.960 Å) in 3 is slightly longer than those in Hayton's [Cu(η 6 -C 6 Me 6 )] + complexes (1.800(3) and 1.775(6) Å), 6 but significantly shorter than those reported for the tethered Cu(arene) complexes such as Cu( i )-cyclophanes or 9,10-anthracene derived endo-cyclic Cu( i ) complexes (∼2.5–3.0 Å). 4 The [SbF 6 ] anion in the asymmetric unit shows no significant bonding interaction with the Cu + atom and the closest approach between the F atom and the Cu center (Cu···F) is 4.96(1) Å, which rules out any possibility of interaction between them.…”

“…A major breakthrough in this research was recently achieved by Hayton and coworkers, who isolated two half sandwich complexes [(η 6 -C 6 Me 6 )Cu(PR 3 )][PF 6 ] (R = Ph, OPh) where the C 6 Me 6 ring is bound to the Cu ion in the η 6 coordination mode. 6 However, they have also theoretically shown that when benzene is employed instead of hexamethylbenzene as an arene, the η 2 mode is preferred, and hence surmised that the preference for the η 6 mode over the η 2 mode is exclusively due to steric repulsion between Me groups and PR 3 units. Additionally, they calculated the relative energies for [Cu(C 6 H 6 )] + in gas as well as condensed phases and found the preference for the η 2 mode in both phases but more in the condensed phase, as previously predicted by Guo et al These studies consequently lead to the question: is it even possible to isolate [Cu(η 6 -C 6 H 6 )] + in the condensed phase?…”