J. Huang et al., Structural and thermochemical studies of chiral nucleophilic carbenes in the Cp*RuCl(L*) (Cp* = eta(5)-C5Me5; L* = chiral nucleophilic carbene) system, ORGANOMETAL, 20(13), 2001, pp. 2878-2882
The reaction of [Cp*RuCl](4) (1) with chiral nucleophilic carbene ligands L
= 1,3-R-2-imidazol-2-ylidene (R = (R)-1-cyclohexylethy1 ((-)ICMe), (1S,2S,
3S,5R)-isopinocamphenyl ((+)-I(i)PCamp), (R)-alpha -methylbenzyl ((+)IBMe))
affords the unsaturated chiral Cp*Ru(L)Cl(Cp* = eta (5)-C5Me5) complexes 2
-4 in high yields. A solution calorimetric investigation in this series Cla
rifies the electron donor properties of these chiral ligands, and compariso
ns are made with other recently reported nucleophilic carbene complexes and
with the widely used PCy3. Structural information from single-crystal X-ra
y studies for complexes 2, 3, Cp*Ru(IMes)Cl (IMes = 1,3-bis(2,4,6-trimethyl
phenyl)imidazol-2-ylidene; 5), Cp*Ru(ICy)Cl (ICy = 1,3-dicyclohexylimidazol
-2-ylidene; 6), and Cp*Ru(IAd)Cl (IAd = 1,3-diadamantylimidazol-2-ylidene;
7) allows for an initial quantitative treatment of steric parameters associ
ated with these ligands.