ic500811n_si_001.cif (44.81 kB)
C–H Activation of Pyrazolyl Ligands by Ru(II)
dataset
posted on 2014-06-16, 00:00 authored by Evan E. Joslin, Brandon Quillian, T. Brent Gunnoe, Thomas R. Cundari, Michal Sabat, William H. MyersPreviously,
hydridotris(pyrazolyl)borate (Tp) Ru(II) alkyl and
aryl complexes of the type TpRu(L)(NCMe)R (R = methyl or aryl;
L = charge-neutral two-electron donating ligand) were demonstrated
to activate aromatic C–H bonds. To determine the impact of
replacing the anionic Tp ligand with charge-neutral poly(pyrazolyl)alkane
ligands, [(C(pz)4)Ru(P(OCH2)3CEt)(NCMe)Me][BAr′4] (pz = pyrazolyl, BAr′4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) was prepared.
Heating a C6D6 solution of [(C(pz)4)Ru(P(OCH2)3CEt)(NCMe)Me][BAr′4] with 1 equiv of NCMe resulted in C–H activation of
the 5-position of a pyrazolyl ring to yield [(κ3-(N,C5,N)C(pz)4)Ru(P(OCH2)3CEt)(NCMe)2][BAr′4] and CH4. Intramolecular
C–H activation of the 5-position of a pyrazolyl ring also occurred
when (η6-p-cymene)Ru(P(OCH2)3CEt)(Br)Ph was heated in the presence of
C(pz)4 to yield [(κ3-N,C5,N)C(pz)4]Ru(P(OCH2)3CEt)(NCMe)Br and C6H6. Density functional theory calculations revealed
that the different reactivities of TpRu(P(OCH2)3CEt)(NCMe)R and [(C(pz)4)Ru(P(OCH2)3CEt)(NCMe)Me][BAr′4]
result from the stronger binding of the Tp pyrazolyl rings to Ru(II)
compared to that of C(pz)4.