Zirconium Complexes of Diamine−Bis(phenolate) Ligands: Synthesis, Structures, and Solution Dynamics

A family of new organometallic and coordination compounds supported by the diamine−bis(phenolate) ligands O2NN‘Me and O2NN‘tBu are reported [H2O2NN‘R = (2-C5H4N)CH2N(CH2-2-HO-3,5-C6H2R2)2, where R = Me (1a) or tBu (1b)]. Reaction of H2O2NN‘R with sodium
hydride in THF gives the corresponding sodium salts Na2O2NN‘R (R = Me (2a) or tBu (2b)).
Reaction of H2O2NN‘R with Zr(CH2SiMe3)2Cl2(Et2O)2 gives the cis-dichloride derivatives
ZrCl2(O2NN‘R) (R = Me (3a) or tBu (3b)), which exist as two isomers (possessing either C1
(major) or Cs symmetry) in dynamic equilibrium with each other in solution. The compound
3b can also be prepared from Na2O2NN‘tBu and ZrCl4(THF)2, but reaction of Na2O2NN‘Me
with either ZrCl4 in benzene or ZrCl4(THF)2 in THF gives mixtures of 3a and the eight-coordinate bis(diamine−bis(phenolate)) complex Zr(O2NN‘Me)2 (4a). The latter can also be
prepared from 2 equiv of H2O2NN‘Me and Zr(CH2SiMe3)4. Treatment of Zr(NMe2)4 with H2O2NN‘tBu leads to the bis(dimethylamide) derivative Zr(NMe2)2(O2NN‘tBu) (5b). Similar protonolysis reactions between ZrR‘4 (R‘ = CH2SiMe3, CH2CMe3, or CH2Ph) give the corresponding
organometallic alkyl or benzyl compounds ZrR‘2(O2NN‘R) [R‘ = CH2SiMe3 (8a, 8b), CH2CMe3 (9a, 9b), or CH2Ph (10a, 10b); R = Me (suffix a) or tBu (suffix b)]. The dichloride
complexes ZrCl2(O2NN‘R) (3a, 3b) are also precursors to new organometallic derivatives,
and treatment with LiR‘ (R‘ = Me or CH2SiMe3) or R‘MgCl (R‘ = CH2Ph or C3H5) yields
ZrR‘2(O2NN‘R) [R‘ = Me (6a, 6b), η3-C3H5 (7b), CH2SiMe3 (8a, 8b), CH2Ph (10a, 10b)]. The
thermally unstable bis(η3-allyl) complex 7b is highly fluxional in solution. Reaction of the
dibenzyl compound 10a or 10b with B(C6F5)3 in the presence of THF gives the cationic
complexes [Zr(CH2Ph)(THF)(O2NN‘R)]+ as the [PhCH2B(C6F5)3]- salts (11a, 11b). The X-ray
crystal structures of the compounds 3a, 3b, 4a, 5b, 6a, 6b, and 10a are described.