title: Lanthanide complexes of the Kläui metalloligand, CpCo(P═O(OR)2)3: an examination of ligand exchange kinetics between isotopomers by electrospray mass spectrometry.
abstract: A series of lanthanide complexes, {[CpCo(P═O(OR)2)3]2Ln(H2O)x}(+)Cl(-) (Ln = Nd, 3; Eu, 4; Tb, 5; Yb, 6; R = Et, a; R = Ph, b) bearing two cobalt metalloligands were prepared. Electrospray mass spectrometry and thermogravimetric analysis suggest that the cations are either solvent-free or contain very weakly bound water molecules. The related complex {[CpCo(P═O(OPh)2)3]2Yb}(+) [CoCl3(THF)](-), 7, was crystallographically characterized, and the cation in this case was confirmed to be 6-coordinate and solvent-free. Ligand exchange rates between the d0- and d60-isotopomers of 3a-6a and 5b were determined in acetonitrile by electrospray mass spectrometry. The ligand exchange rate was found to increase by almost 4 orders of magnitude from the smallest (Yb, 6a, k = 0.3 M(-1) s(-1)) to largest ion (Nd, 3a, >2500 M(-1) s(-1)) in acetonitrile. Additionally, the ligand exchange rate increased rapidly for 5a (Tb) with increasing water concentration from 30 M(-1) s(-1) in pure acetonitrile to 268 M(-1) s(-1) in 50:50 (v/v) acetonitrile/water. Changing the phosphite substituent had no significant impact on the rate of ligand exchange for 5b (R = Ph) relative to 5a (R = Et).
authors.affiliation: Department of Chemistry, University of Victoria , P.O. Box 3065, Victoria, British Columbia, Canada V8W 3V6.
authors.forename: Kevin J H
authors.initials: KJ
authors.lastname: Allen
authors.forename: Emma C
authors.initials: EC
authors.lastname: Nicholls-Allison
authors.forename: Kevin R D
authors.initials: KR
authors.lastname: Johnson
authors.forename: Rajinder S
authors.initials: RS
authors.lastname: Nirwan
authors.forename: David J
authors.initials: DJ
authors.lastname: Berg
authors.forename: Dennis
authors.initials: D
authors.lastname: Wester
authors.forename: Brendan
authors.initials: B
authors.lastname: Twamley