Trifluoromethyl‐Containing β ‐Diketiminato‐Magnesium Complexes: Synthesis, Structures, and Catalysis for the Hydroboration of Carbodiimides

ABSTRACT Trifluoromethyl‐containing β‐diketiminate ligands (CF 3 )BDI Et ‐H = (2,6‐di‐Et 2 C 6 H 3 )N=C (CF 3 )CH=C (CF 3 )NH(2,6‐di‐Et 2 C 6 H 3 ), (CF 3 )BDI i Pr ‐H = (2,6‐di‐ i Pr 2 C 6 H 3 )N=C (CF 3 )CH=C (CF 3 )NH(2,6‐di‐ i Pr 2 C 6 H 3 ) react with Mg n Bu 2 readily to provide THF‐ligated four‐coordinate monomeric magnesium butyl complexes (CF 3 )BDI Et Mg n Bu (THF) ( 1 ) and (CF 3 )BDI i Pr Mg n Bu (THF) ( 2 ) in THF, and three‐coordinate monomeric complexes (CF 3 )BDI Et Mg n Bu ( 3 ) and (CF 3 )BDI i Pr Mg n Bu ( 4 ) in toluene, respectively. The alkane elimination between 4 and NH (SiHMe 2 ) 2 gives silylamido complex 5 in toluene. Treatments of 4 with heterocumulene tert‐butyl isothiocyanate, tert‐butyl isocyanate, and N,N′‐diisopropylcarbodiimide produce single insertion derivatives (CF 3 )BDI i Pr MgN ( t Bu)C ( n Bu)S ( 6 ), (CF 3 )BDI i Pr MgN ( t Bu)C ( n Bu)O ( 7 ), and (CF 3 )BDI i Pr MgN ( i Pr)C ( n Bu)N ( i Pr) ( 8 ), respectively. All these new compounds were characterized by NMR spectroscopy, and the molecular structures of complexes 1 , 2 , 4 – 7 were further confirmed by single‐crystal X‐ray diffraction analyses. Moreover, representative complexes 2 – 5 were employed as pre‐catalysts for the hydroboration of commercially available carbodiimides bearing aliphatic and aromatic substituents with pinacol borane HBpin, including diisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC), di‐ tert ‐butylcarbodiimide, 2,6‐diisopropylphenylcarbodiimide, and unsymmetric 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDCI), in which the three‐coordinate monomeric complexes 3 and 4 showed better efficiency giving corresponding N ‐boryl formamidine products in high yields. A possible mechanistic pathway of the hydroboration reaction has been proposed.