Conversion of a AuI Fluorido Complex into an N‐Fluoroamido Derivative: N−F versus Au−N Reactivity

The AuI complex [Au{N(F)SO2Ph}(SPhos)] (SPhos=dicyclohexyl(2′,6′-dimethoxy[1,1′-biphenyl]-2-yl)phosphane) (2) bearing a fluoroamido ligand has been synthesized by reaction of the fluorido complex [Au(F)(SPhos)] (1) with NFSI (NFSI=N-fluorobenzenesulfonimide). A reaction with CO resulted in an unprecedented insertion into the N−F bond at 2. With the carbene precursor N2CH(CO2Et) N−F bond cleavage gave the Au−F bond insertion product [Au{CHF(CO2C2H5)}(SPhos)] (7). The presence of CNtBu led to Au−N cleavage at 2 and concomitant amide formation to give the cationic complex [Au(CNtBu)(SPhos)][N(F)SO2Ph)] (5), which reacted further to give FtBu as well as the cyanido complex [Au(CN)(SPhos)] (6). These results led to the development of a process for the amination of electrophilic organic substrates by transfer of the fluoroamido group NF(SO2Ph)−.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Peer Reviewe

Au(I) Fluorido Phosphine Complexes: Tools for the Hydrofluorination of Alkynes

The reactivity of the Au(I) fluorido complex [Au(F)(SPhos)] (SPhos=dicyclohexyl(2’,6’‐dimethoxy[1,1’‐biphenyl]‐2‐yl)phosphine) (1) towards several alkynes was studied. The formation of fluorovinyl species by formal insertion of the alkyne in the metal‐fluorine bond was observed. Addition of HCl to vinyl complexes resulted in protodeauration and elimination of the hydrofluorinated alkynes. Treatment of 1 with the terminal alkyne 1‐hexyne resulted in clean formation of the alkynyl complex [Au(C≡CC4H9)(SPhos)] (15), whereas with an excess alkyne hydrofluorination was also observed. Various Au(I) phosphine complexes including 1 were then compared in their ability to catalyze hydrofluorination reactions of 1‐phenyl‐1‐propyne with Et3N ⋅ 3HF as HF source. Model reactions suggested a reaction mechanism, which imparts a pre‐coordination of an alkyne to a cationic gold center followed by nucleophilic addition of a fluoride. Mechanistic investigations included reactivity studies at [Au(SPhos)][B(C6F5)4)] (17), which was treated with 4‐phenyl‐3‐butyn‐2‐one and TMAF (TMAF=tetramethylammonium fluoride). The reaction led to the formation of the complex [Au(CH3C(O)C=C(F)Ph)(SPhos)] (13), but not the fluorido complex 1.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659German Research Foundation http://dx.doi.org/10.13039/501100001659Deutsche Forschungsgemeinschaft (DFG)Peer Reviewe

Bimetallic Carbonyl Complexes Based on Iridium and Rhodium: Useful Tools for Hydrodefluorination Reactions

A set of bimetallic complexes based on iridium and rhodium with bis(diphenylphosphino)methane, bis(di‐iso‐propylphosphino)methane, diphenyl‐2‐pyridylphosphine and 2‐(di‐iso‐propylphosphino)imidazole bridging ligands was prepared. The complexes were characterized by NMR and IR spectroscopy and studied quantum‐chemically using DFT methods. The bimetallic systems succeeded in catalytic hydrodefluorination reactions of lower fluorinated aryl fluorides using molecular hydrogen and sodium tert‐butoxide as a base. Effects of (i) ligand variation, (ii) mono‐ vs bimetallic nuclearity, and (iii) Ir vs Rh metal identity were studied and rationalized en route to achieve an effective hydrodefluorination.Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)Peer Reviewe

NMR spectroscopic study of the adduct formation and reactivity of homoleptic rare earth amides with alkali metal benzyl compounds, and the crystal structures of [Li(TMEDA)₂][Nd{N(SiMe₃)₂}₃(CH2Ph)] and [{Li(TMP)}₂{Li(Ph)}]₂

An NMR spectroscopic study has been conducted into the reactivity of alkali metal benzyls [M(CH2Ph)], (M = Li, Na, K) with lanthanide tris(amide) complexes [Ln(N")3] (Ln = Y, Ce, Nd; N" = N(SiMe3)2) and [Ce(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). It was found that for [Ln(N")3], benzyl adducts [M][Ln(N")3(CH2Ph)] were initially formed, and the molecular structure for M = Li(TMEDA)2 and Ln = Nd was determined revealing a distorted tetrahedral [Nd(N")3(CH2Ph)] anion. In all cases, these adduct complexes were unstable, intramolecularly deprotonating a methyl arm of a N" ligand via benzyl basicity and eliminating toluene to prepare cyclometallated complexes of the form [M][Ln(N")2{κ2-CH2Si(Me)2N(SiMe3)}]. In parallel studies, reactions of [Li(Ph)] with [Ln(N")3] (Ln = Ce, Nd) afforded [Li(N")], whilst for (Ln = Y) adduct formation was observed. [Ce(TMP)3] did not generate any characterisable bimetallic adducts. The reaction of [Li(Ph)] with [Li(TMP)] afforded the hexanuclear [{Li(TMP)}2{Li(μ-Ph)}]2, which features lithium in three different coordination environments

Palladium-Catalyzed Oxidative Borylation of Allylic C–H Bonds in Alkenes

This communication describes an efficient palladium pincer complex-catalyzed allylic C–H borylation of alkenes. The transformation exhibits high regio- and stereoselectivity with a variety of linear alkenes. A synthetically useful feature of this allylic C–H borylation method is that all allyl-Bpin products can be isolated in usually high yields. Preliminary mechanistic studies indicate that this C–H borylation reaction proceeds via Pd­(IV) pincer complex intermediates