Oxygen-Bound Trifluoromethoxide Complexes of Copper and Gold

Abstract

Well-defined copper and gold complexes have been prepared which contain the shortest structurally characterized metal−oxygen bonds between transition metals and a trifluoromethoxide moiety. The trifluoromethoxide ligand is O-bound to both the copper and gold centers, with a copper−oxygen distance of 1.849(4) Å and a gold−oxygen distance of 2.058(4) Å. Density functional theory (DFT) calculations on all new trifluoromethoxy complexes were performed in order to obtain bond lengths and angles that are not influenced from any intermolecular contacts in the solid state and also to provide a first glimpse of the electronic features of this previously unknown ligand.The trifluoromethoxide group has recently been described as "the least well-understood" fluorine-containing substituent. 1

Cooperative dual palladium/silver catalyst for direct difluoromethylation of aryl bromides and iodides

“…We next turned our attention to identify a ligand to stabilize difluoromethylated coinage metal complexes. Because strong s-donating N-heterocyclic carbenes (NHCs) have successfully been employed in stabilizing many coinage metal complexes [37][38][39][40][41][42] , we sought to determine if NHC ligands could stabilize AgCF 2 H that was known to undergo homolytic cleavage of Ag-C(CF 2 H) bond to form HCF 2 and Ag(0) even at À 50°C. It was found that NHCligated difluoromethyl-silver complex [(SIPr)Ag(CF 2 H)] (SIPr: 1,3-bis(2,6-diisopropyl phenyl) imidazolin-2-ylidene) 6 could be prepared in 82% yield by the reaction of [(SIPr)AgCl] with 2.0 equivalents of TMSCF 2 H in THF at room temperature in the presence of 2.0 equivalents of NaO t Bu (Fig.…”

Aryl-BIAN-ligated silver(i) trifluoromethoxide complex

“…The two Ag−N bonds are substantially different [Ag(trifluoromethoxide ligand is significantly shorter than that of the Ag(1)−O(THF) (2.502(4) Å), but is significantly longer than that found in the related complexes (SIPr)MOCF 3 (M = Cu: 1.849(5) Å; M = Au: 2.058(4) Å). 40 Moreover, the M−O(1)−C(1) (M = Ag) angle in 1 is 125.3(3)°, which is larger than those found in (SIPr)MOCF 3 (M = Cu: 120.7(5)°; M = Au: 123.3(7)°) 40. …”

Access to a new class of synthetic building blocks via trifluoromethoxylation of pyridines and pyrimidines

“…11,16,17 This is due to (i) strong electron repulsion between three fluorine atoms and an incoming nucleophile; (ii) formation of energetically disfavoured CF 3 carbocation transition state structure (TS); and (iii) competing iodination of nucleophiles due to the reversed electron density. In addition, the thermal instability of transition metal–OCF 3 complexes (they readily decompose to form fluorophosgene and metal fluoride) 18 and the poor nucleophilicity of the OCF 3 anion (a reactive electrophile is needed for the C–OCF 3 bond formation) 19 have hampered the development of the C–OCF 3 bond formation through either transition metal-catalysed C–O bond formation or nucleophilic substitution. Strategies for the synthesis of trifluoromethoxylated heteroaromatic compounds are very rare.…”