C 2 ‐Symmetric Group 4 Metal Complexes Adorned with Chiral N,O Chelates: Synthesis and Structural Characterization of Helical Hexacoordinate Metal Dichlorides Derived from 6‐Isopropyl‐3‐methyl‐2‐(4‐isopropyl‐4,5‐dihydrooxazol‐2‐yl)phenol Ligands

A series of group 4 metal complexes containing [6‐isopropyl‐3‐methyl‐2‐(4‐R‐4,5‐dihydrooxazol‐2‐yl)phenol] ligands, N , O ‐(Oz R –O Ph ) [Oz R = oxazolyl; R = i Pr ( 4 ), t Bu ( 5 ); O Ph = phenolate] was prepared. The reaction of the lithium salts of compounds 4 and 5 with MCl 4 , (M = Ti, Zr, Hf) in 2:1 ratio afforded the corresponding hexacoordinate metal complexes of the types [{ N , O ‐(Oz i Pr –O Ph )} 2 MCl 2 ] [M = Ti ( 6 ), Zr ( 7 ), Hf ( 8 )] and [{ N , O ‐(Oz t Bu –O Ph )} 2 MCl 2 ] [M = Ti ( 9 ), Zr ( 10 ), Hf ( 11 )], respectively. The molecular structures of 6 , 7 , and 8 were established by X‐ray structural studies. The structures showed a helical screw‐shaped molecular entity with two alternating N,O‐chelating ancillary ligands and two cis ‐chlorido ligands at the metal centers. In the case of compound 6 , chiral locking by two N,O‐chelating ligands at the titanium resulted in unusual air stability. The cyclic voltammogram showed electrochemically quasireversible reduction for compound 6 , whereby the half‐life of the reduction state was about 3 s.