Reactions of RuCp and RuCp* Allyl Carbene Complexes:  Products Derived from Activation of Phenyl, Cyclohexyl, and Methyl C−H Bonds in PPh₃, PCy₃, and Cp* Ligands

Abstract

Ruthenium allyl carbene complexes of the type [RuCp(dC(R)-(η 3 -CHC(R)CHPR′ 3 ))]PF 6 (R, R′ ) aryl, alkyl substituents) are characterized by two reaction modes. (i) They behave as masked coordinatively unsaturated complexes and react readily with the donor ligands PR 3 and P(OR) 3 to give η 3 -butadienyl complexes. This is not a simple nucleophilic addition at the metal center but involves changes in both the bonding mode and the stereochemistry of the allyl carbene C 4 -chain. The incoming nucleophile induces C-H bond activation effecting formally a 1,4 hydrogen shift. (ii) They are capable of activating C-H bonds of aryl and alkyl groups in the bulky tertiary phosphine ligands PPh 3 and PCy 3 to give novel η 4 -butadiene complexes. In these, one R of PR 3 is σ-bonded to the metal center. A divergent rearrangement results if the allyl carbene complex derives from parent acetylene (instead of a terminal alkyne). In this case the C 4 -unit features a η 3 -allyl moiety and the metal center is η 2 -coordinated to an arene ring of the PPh 3 substituent. Finally, RuCp* allyl carbene complexes have been prepared for the first time. They are reactive entities and react slowly with cleavage of one of the ring methyl C-H bonds of the Cp* ligand to give tetramethylfulvene-type complexes.

Reaction Chemistry of the Carbenoid Butadienyl Complex Ion [CpCo(σ,η4‐C4HMe4)]+ Formed by Protonation of the Cyclobutadiene Complex [CpCo(C4Me4)]

“…Experimental support for this notion comes from the thermal behavior of 5. Monitoring a solution of 5 in [D 8 ]-toluene showed the onset of a slow thermolysis reaction around 80°C. Complex 5 partially isomerized to produce its stereoisomer 14, and partially decomposed with formation of a new dinuclear complex 15 and free olefins.…”

“…Thermolysis of 14 in [D 8 ]toluene was found to be markedly slower and again produced the dinuclear complex 15 and free olefins. Complex 5 was not found in the product mixtures.…”

“…While 2 + has not been ob- [6]CF 3 SO 3 with retention of the stereochemistry at C-4 (NMR), while the same reaction at ambient temperature and in presence of a large excess of pyridine is accompanied by stereoisomerization and afforded [7]CF 3 SO 3 (94 %). Nucleophilic addition of excess PPh 3 to 3 + gave a phosphonium salt [8]BF 4 , again with stereoisomerization, in near quantitative yield (98 %). Addition of CNtBu with concomitant rearrangement produced a (tert-butylamino)cobaltocenium salt [9]CF 3 SO 3 (90 %).…”

“…Complexes with σ,η 4 -butadienyl-type ligands are known in some variety, for instance of the fragments CpRu, [7] Cp*Ru, [8] CpRe, [9] and CpMo [10] as well as of other complexes of Nb, [11] Mo, [12] and W. [12] To the best of our knowledge, cation 3 + is the first such complex of a 3d metal. Since the ion 3 + originates from a protonation reaction, it seemed particularly interesting to study its reactions with bases and/or nucleophiles.…”

Catalysis and Organometallic Chemistry of Monometallic Species

“…173 Double C-H activation of bis(di-tert-butylphosphino)pentane to give a ruthenium alkene 18 and an osmium carbene 19, 174 a triple C-H activation reaction to give complex 20, 175 and reactions of RuCp and RuCp* alkyl complexes that exhibit a range of intramolecular C-H activation events are also described. 176 Intermolecular C-F activation of vinyl fluoride by Os() complexes has also been studied. 177 …”