THE DYNAMICS OF THE BETA-AGOSTIC ISOPROPYL COMPLEX (ARN=C(R)-C(R)=NAR)PD(CH(CH2-MU-H)(CH3))(-) (AR = 2,6-C6H3(I-PR)(2)) - EVIDENCE FOR IN-PLACE ROTATION VERSUS DISSOCIATION OF THE AGOSTIC METHYL-GROUP()BAR4'()

Variable-temperature H-1 and C-13 NMR spectroscopy has been used to st udy the dynamics of the beta-agostic isopropyl complex (ArN=C(R)-C(R)= NAr)Pd(CH(CH2-mu-H)(CH3))+BAr4'(-) (Ar = 2,6-C6H3(i-Pr)(2)). H-1 and C -13 line shape analysis suggests two independent processes occur: inte rchange of the agostic and nonagostic methyl groups and exchange of hy drogens within the agostic methyl group, which is best regarded as in- place methyl group rotation. Barriers for both of these processes are similar, with Delta G double dagger ca. 9 kcal/mol. The methyl groups undergo interchange without inversion at the Pd(II) center.