Group 4 Organometallics Supported by Sterically Hindered β ‐Diketonates

The synthesis, characterization, and reactivity of group 4 organometallics supported by β ‐diketonates is reported. Sterically hindered β ‐diketonates, such as 2,6‐dimesitylbenzoyl pinacolone ( L 1 ) and 2,6‐dimesitylbenzoyl acetylmesitylene ( L 2 ), preclude the formation of tetrakis‐ and tris‐chelates, halting at cis ‐octahedrally coordinated M( L n ) 2 Cl 2 (M = Ti, Zr, Hf; L n = L 1 , L 2 ). Metathesis with benzylmagnesium chloride affords M( L n ) 2 Bn 2 (M = Zr, Hf) and the reduced Ti( L 1 ) 2 Bn(THF) species. These are the first structurally‐characterized metal alkyl complexes exclusively supported by β ‐diketonates among the group 4 metals. Thermolysis of Zr( L n ) 2 Bn 2 complexes results in unimolecular migratory insertion reaction, forming an enone by‐product and ZrO 2 . Combined Eyring analyses and computational investigations suggest the bond rearrangements are initiated by an initial benzyl migration reaction to the less hindered carbonyl group on the ligand. Activation of M( L n ) 2 Bn 2 (M = Zr, Hf) in the presence of olefins resulted in similar oxygen abstraction. Implications and prospects for β ‐diketonate‐supported catalysis are discussed.