TY - JOUR
T1 - Further evidence for ‘extended’ cumulene complexes
T2 - derivatives from reactions with halide anions and water
AU - Hall, Michael
AU - Steen, Rachel
AU - Korb, Marcus
AU - Sobolev, Alexandre
AU - Moggach, Stephen
AU - Lynam, Jason Martin
AU - Low, Paul J.
N1 - This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.
PY - 2020/6/5
Y1 - 2020/6/5
N2 - Reactions of [Ru{C=C(H)‐1,4‐C6H4CºCH}(PPh3)2Cp]BF4 ([1a]BF4) with HX, give [Ru{CºC‐1,4‐C6H4‐C(X)=CH2}(PPh3)2Cp] (X = Cl, Br) from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C6H4=C=CH2)(PPh3)2Cp]+. Similarly, [M{C=C(H)‐1,4‐C6H4‐CºCH}(LL)Cp ]BF4 [M(LL)Cp´ = Ru(PPh3)2Cp ([1a]BF4); Ru(dppe)Cp* ([1b]BF4); Fe(dppe)Cp ([1c]BF4); Fe(dppe)Cp* ([1d]BF4)] react with H+/H2O to give the acyl‐functionalised complexes [M{CºC‐1,4‐C6H4‐C(=O)CH3}(LL)Cp´]. The Markovnikov addition of the nucleophile to the remote alkyne is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene [M(=C=C=C6H4=C=CH2)(LL)Cp´]+ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(CºC‐1,4‐C6H4‐CºCH)(PPh3)2Cp] and [Ru(CºC‐1,4‐C6H4‐CºCH)(dppe)Cp*] reacted with the small electrophiles [CN]+ and [C7H7]+ at the β‐carbon to give vinylidene complexes, trityl cation ([CPh3]+) reacted with [M(CºC‐1,4‐C6H4‐CºCH)(LL)Cp´] at the exposed end of the carbon‐rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C6H4=C=C(H)CPh3}(LL)Cp´]+, which were isolated as the water adducts [M{CºC‐1,4‐C6H4‐C(=O)CH2CPh3}(LL)Cp´]. Evincing the scope of the reaction, the (5‐ethynyl‐2‐thienyl)vinylidene complexes [M{C=C(H)‐2,5‐cC4H2S‐CºCH}(LL)Cp´]BF4 add water readily to give [M{CºC‐2,5‐cC4H2S‐C(=O)CH3}(LL)Cp´].
AB - Reactions of [Ru{C=C(H)‐1,4‐C6H4CºCH}(PPh3)2Cp]BF4 ([1a]BF4) with HX, give [Ru{CºC‐1,4‐C6H4‐C(X)=CH2}(PPh3)2Cp] (X = Cl, Br) from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C6H4=C=CH2)(PPh3)2Cp]+. Similarly, [M{C=C(H)‐1,4‐C6H4‐CºCH}(LL)Cp ]BF4 [M(LL)Cp´ = Ru(PPh3)2Cp ([1a]BF4); Ru(dppe)Cp* ([1b]BF4); Fe(dppe)Cp ([1c]BF4); Fe(dppe)Cp* ([1d]BF4)] react with H+/H2O to give the acyl‐functionalised complexes [M{CºC‐1,4‐C6H4‐C(=O)CH3}(LL)Cp´]. The Markovnikov addition of the nucleophile to the remote alkyne is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene [M(=C=C=C6H4=C=CH2)(LL)Cp´]+ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(CºC‐1,4‐C6H4‐CºCH)(PPh3)2Cp] and [Ru(CºC‐1,4‐C6H4‐CºCH)(dppe)Cp*] reacted with the small electrophiles [CN]+ and [C7H7]+ at the β‐carbon to give vinylidene complexes, trityl cation ([CPh3]+) reacted with [M(CºC‐1,4‐C6H4‐CºCH)(LL)Cp´] at the exposed end of the carbon‐rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C6H4=C=C(H)CPh3}(LL)Cp´]+, which were isolated as the water adducts [M{CºC‐1,4‐C6H4‐C(=O)CH2CPh3}(LL)Cp´]. Evincing the scope of the reaction, the (5‐ethynyl‐2‐thienyl)vinylidene complexes [M{C=C(H)‐2,5‐cC4H2S‐CºCH}(LL)Cp´]BF4 add water readily to give [M{CºC‐2,5‐cC4H2S‐C(=O)CH3}(LL)Cp´].
U2 - 10.1002/chem.201905399
DO - 10.1002/chem.201905399
M3 - Article
SN - 0947-6539
VL - 26
SP - 7226
EP - 7234
JO - Chemistry : A European Journal
JF - Chemistry : A European Journal
IS - 32
ER -