Structures and Properties of Copper Alkene Complexes. Preorganization Effects and the Binding of Different Isomers of Cyclododecatriene to Copper Triflate

Abstract

The single-crystal X-ray structures of the copper 1,5,9-cyclododecatriene complexes (cis,cis,trans-C 12 H 18 )Cu(OTf), cct-1, (cis,trans,trans-C 12 H 18 )Cu(OTf), ctt-1, and (trans,trans,trans-C 12 H 18 )Cu(OTf), ttt-1, have been determined. In all three compounds, the triflate ligand and all three CdC double bonds of the triene are bound to the copper center, which adopts a distorted tetrahedral coordination geometry. The Cu-C distances are 2.190-2.217 Å and the Cu-O distances are 2.096-2.135 Å. The complex ctt-1 is a nonelectrolyte in nitromethane. The 1 H and 13 C NMR spectra of ctt-1 and ttt-1 show that the two faces of the trienes, which are inequivalent in the solid state structure, are equivalent in solution even at -70 °C, suggesting that these molecules undergo a dynamic exchange process that is rapid on the NMR time scale (the two faces of cct-C 12 H 18 are inequivalent even for the free triene, and so dynamic processes in its copper complex are not so easily observed). Most likely, the dynamic processes in ctt-1 and ttt-1 involve movement of the triflate ligand between one "side" of the molecule and the other by means of a dissociative process, although dissociation of one or more double bonds of the alkene from the copper center, followed by an intramolecular rearrangement, cannot be ruled out. 63 Cu NMR chemical shifts are also reported. Competition studies in toluene show that the free energy of ctt-1 is about 1 kcal mol -1 lower (i.e., more stable) than expected from the relative energies of the free trienes. This stabilization can be attributed to a preorganization effect.

Structural studies of (prop-2-en-1-yl)bis[(pyridin-2-yl)methylidene]amine hetero-scorpionate copper complexes

“…A second feasible coordination mode would be to have the allyl group in the olefinic arm make an associative bond with the metal center, displacing the chloride ligand and occupying the fourth coordination site. This type of associative bonding is well documented in the literature (Bellott & Girolami, 2009;Sullivan et al, 2003). However, given the short length of the fluxional arm in this case, it is unlikely that an associative bond would form between the olefinic arm and metal center of the same complex.…”

Isolable Ethylene Complexes of Copper(I), Silver(I), and Gold(I) Supported by Fluorinated Scorpionates [HB{3‐(CF3),5‐(CH3)Pz}3]– and [HB{3‐(CF3),5‐(Ph)Pz}3]–

“…Silver(I) triflate, and AuCl were purchased from Aldrich and ethylene gas was purchased from Matheson. [HB{3‐(CF 3 ),5‐(CH 3 )Pz} 3 ]Na, [HB{3‐(CF 3 ),5‐(Ph)Pz} 3 ]Na(THF), and [CF 3 SO 3 Cu] 2 · C 6 H 6 , were prepared via reported procedures.…”

Metal Triflimidates: Better than Metal Triflates as Catalysts in Organic Synthesis—The Effect of a Highly Delocalized Counteranion

“…[37] The h 2 -O,O mode seems to be the most frequent mode of coordination, with the anion adopting a cisoid conformation (the CF 3 groups lying on the same side of the S-N-S plane) which leads to a delocalized six-membered ring when coordinated to a metal center; the Tf 2 N À ion behaves more like a ligand. [39] By comparing data from metallic triflate and triflimidate salts, it appears that the bond lengths between the coordinating oxygen atom and the metal center are usually of the same order of magnitude [37][38][39][40][41][42] [38] Interestingly, when coordinated, the triflimidate anion has the capacity to undergo structural changes, compared to the free anion, depending on the environment. [37] It has been shown in the reactions of silicon-based Lewis acids that although the Bronsted acidity of HOTf is superior to that of HNTf 2 , R 3 SiNTf 2 is a superior Lewis acid than R 3 SiOTf because of the greater steric repulsion between the R 3 Si and NTf 2 groups.…”