Activation of sp3-CH Bonds in a Mono(pentamethylcyclopentadienyl)yttrium Complex. X-ray Crystal Structures and Dynamic Behavior of Cp*Y(o-C6H4CH2NMe2)2 and Cp*Y[o-C6H4CH2NMe(CH2-μ)][μ-o-C6H4CH2NMe(CH2-μ)]YCp*[THF]

Reaction of Y(o-C6H4CH2NMe2)3 (1) with Cp*H gives Cp*Y(o-C6H4CH2NMe2)2 (2), which crystallizes in the monoclinic space group P21/n (No. 14) with a = 18.607 (4) Å, b = 15.633 (3) Å, c = 8.861 (3) Å, β = 102.73 (3)°, and Z = 4. Least-squares refinement with 3006 independent reflections (F > 4.0σ(F)) led to a final RF (wR) of 0.053 (0.068). The molecular structure consists of monomeric Cp*Y(o-C6H4CH2NMe2)2 units with a regularly bonded Cp* ligand (Y-Ct = 2.367 (3) Å), equal Y-C(aryl) distances (2.479 (6) and 2.471 (6) Å), and both nitrogen atoms coordinated to yttrium (Y-N distances = 2.568 (5) and 2.506 (6) Å). Short intramolecular Y···H distances (Y···H(181) = 3.00 (6) Å, Y···H(183) = 3.13 (9) Å) indicate agostic interactions. The long N(2)-C(18) bond (1.55 (1) Å) and the short Y···C(18) distance (3.202 (8) Å) indicate an Y···C-N agostic interaction. Thermolysis of 2 in THF gives Cp*Y[o-C6H4CH2NMe(CH2-μ)][μ-o-C6H4CH2NMe(CH2-μ)]YCp*[THF] (3) and N,N-dimethylbenzylamine. Compound 3 crystallizes in the monoclinic space group P21/c (No. 14) with a = 17.004 (1) Å, b = 13.962 (1) Å, c = 20.129 (3) Å, β = 92.94 (1)°, and Z = 4. Least-squares refinement with 4578 independent reflections (F > 5.0σ(F)) led to a final RF (wR) of 0.065 (0.070). The molecule consists of two Cp*Y fragments (Y(1)-Ct(1) = 2.420 (6) Å, Y(2)-Ct(2) = 2.414 (5) Å), bridged by two methylene carbon atoms (Y(1)-C(9) = 2.591 (10) Å, Y(2)-C(9) = 2.527 (9) Å, Y(1)-C(18) = 2.622 (10) Å, Y(2)-C(18) = 2.532 (10) Å) and one aryl carbon atom (Y(1)-C(1) = 2.702 (8) Å, Y(2)-C(1) = 2.547 (9) Å). The remaining aryl group is not bridging (Y(1)-C(10) = 2.441 (8) Å). Asymmetry in 3 is caused by THF coordination (Y(2)-O = 2.446 (5) Å). Thermolysis of 2 can be explained by dissociation of an Y-N dative bond followed by activation of an agostic C-H bond.