Amphiphilic carbene complexes: both electrophiles and nucleophiles attack the carbene carbon of C5H5(CO)2Re:CHR

Half‐Sandwich Benzylidene Ruthenium Complexes Bearing Phosphanyl‐Pyridine Ligands: Reactivity towards Nucleophiles and Electrophiles

“…Although nucleophilic addition on the carbenic atom is a well‐known reaction of Fischer carbenes, in our case, reactivity studies of carbene complexes towards nucleophiles present several difficulties on account of the existence of competitive reactions. Casey tested the electrophilic nature of the carbenic atom in [Re(C 5 H 5 )(CO) 2 {=CHCH 2 CH 2 C(CH 3 ) 3 }] by means of the reaction with P(CH 3 ) 3 to afford the zwitterionic compound [Re(C 5 H 5 )(CO) 2 {=CH[P(CH 3 ) 3 ]CH 2 CH 2 C(CH 3 ) 3 }] 46. In contrast to this rhenium carbene complex, 3a reacts with P(CH 3 ) 3 to afford quantitatively and immediately a yellow compound characterized as [Ru(η 5 ‐C 5 Me 5 ){P(CH 3 ) 3 }(P i Pr 2 NHC 5 H 4 N)][BAr′ 4 ] ( 6a ), the result of nucleophilic substitution of the benzylidene ligand at the metal centre by the phosphane, as indicated by the 31 P{ 1 H} NMR spectrum, which displays a strongly coupled double doublet ( 2 J P,P′ = 42 Hz).…”

Quantitative Determination of the Regioselectivity of Nucleophilic Addition to η3-Propargyl Rhenium Complexes and Direct Observation of an Equilibrium between η3-Propargyl Rhenium Complexes and Rhenacyclobutenes

“…For example, phosphine attack might occur at the terminal carbon of 7 to give intermediate A , which could then undergo loss of phosphine to generate 8 (Scheme 8). Alkyl and vinyl CpRe(CO) 2 R − anions are well known stable species 18. The dissociative mechanism of Scheme 7 and the associative mechanism of Scheme 8 are readily distinguished by their kinetic independence or dependence on [PR 3 ].…”

Low-valent Organorhenium Compounds

“…At 1 7 °C, (126) decomposes to an r| 2 -alkene product with deuterium equally distributed between the cis and trans positions at C-l. Reaction of (125) with excess H C 1 leads to reduction and chain extension of the carbene ligand to form the hydroxy carbene (127) 212 The rhenium-carbon bond length in the parent electrophilic methylidene complex [Re(=CH 2 )(NO)(PPh 3 )(r|-Cp*)] + is 0. 189 8(18) nm, and AG*(114 °C) >79 kJ mol" 1 for rotation about the double bond.…”