Synthesis and Characterization of Group 4 Amidinate Amide Complexes M[CyNC(Me)NCy]2(NR2)2 (R = Me, M = Ti, Zr, Hf; R = Et, M = Zr)

Amidinate amide complexes M[CyNC(Me)NCy]2(NR2)2 (M = Ti, R = Me (1); M = Zr, R = Me (2), R = Et, (3); M = Hf, R = Me (4); Cy = cyclohexyl) have been prepared, and their crystal structures show distorted-octahedral coordination spheres. Variable-temperature NMR studies give ΔH⧧ = 2.8(0.2) kcal mol−1, ΔS⧧ = −36(1) eu and ΔH⧧= 0.5(0.3) kcal mol−1, ΔS⧧ = −44(1) eu for interconversions in 2 and 3, respectively.