Atom Transfer Radical Additions with the Cationic Half‐Sandwich Complex [Cp*Ru(PPh₃)₂(CH₃CN)]OTf

Selective Dialkylation of a Doubly Linked Dicyclopentadiene Ligand and the Ensuing Ruthenium Complexes

“…When Zn is used as the reducing agent, the counteranion for 6 is 1 / 2 [Zn 2 Cl 6 ] 2– instead of a chloride anion. This is similar to the reported [ZnCl 4 ] 2– counterion by Severin and co-workers in the synthesis of [Cp*Ru­(MeCN) 3 ] 2 [ZnCl 4 ] when Zn is used as a reducing agent . Complex 6 is air sensitive and will revert back to 5 in CDCl 3 (room temperature, 18 h).…”

“…This is similar to the reported [ZnCl 4 ] 2− counterion by Severin and co-workers in the synthesis of [Cp*Ru(MeCN) 3 ] 2 [ZnCl 4 ] when Zn is used as a reducing agent. 15 Complex 6 is air sensitive and will revert back to 5 in CDCl 3 (room temperature, 18 h). 6 is stable in MeCN, but in CD 3 CN, the 1 H NMR spectrum of 6 shows none of the bound acetonitriles, due to the rapid exchange with the deuterated solvent.…”

Atom‐Transfer Radical Addition (ATRA) and Cyclization (ATRC) Reactions Catalyzed by a Mixture of [RuCl2Cp*(PPh3)] and Magnesium

“…Exchanging PPh 3 for P( n Bu) 3 (Table 2, entries 4 and 5), PCy 3 (Cy: cyclohexyl), or P( p ‐C 6 H 4 Cl) 3 resulted in lower yields (Table 2, entries 4–7). Cationic Ru II complex 4 has been described as one of the best catalysts for the addition of CHCl 3 to styrene,6 but its performance (Table 2, entry 8) was found to be inferior to that of complex 1 (Table 2, entry 1). The “classical” ATRA reaction catalyst [RuCl 2 (PPh 3 ) 3 ] ( 5 ) and the bimetallic catalysts [(cymene)Ru(μ‐Cl) 3 RuCl(C 2 H 4 )(PCy 3 )] ( 6 ) and [Cp*Rh(μ‐Cl) 3 RuCl(PPh 3 ) 2 ] ( 7 ), which were recently reported by our laboratory,5b,e gave only low conversions and yields under the present reaction conditions (Table 2, entries 9–11).…”

“…Consequently, only low turnover numbers (TONs) are achieved; this is particularly evident for addition reactions with substrates that show a low intrinsic reactivity, such as CHCl 3 or 1‐decene. In these cases, the maximum TONs generally do not exceed 300 6…”

Atom Transfer Radical Reactions as a Tool for Olefin Functionalization – On the Way to Practical Applications

“…[33] Their studies showed that the simple modification of the chloro neutral complex into a cationic acetonitrile complex result in a significant increase of the catalyst stability. In addition, Severin and co-workers have proposed a methodology to improve the catalytic activity of ruthenium half-sandwich complexes, which consisted in the addition of the radical initiator azobis(isobutyronitrile) (AIBN) as cocatalyst.…”