The chemistry of sterically crowded aryl oxide ligands. 3. Crystal and molecular structure and spectroscopic properties of mixed benzyl-aryl oxide compounds of zirconium

Article abstract of DOI:10.1021/om00124a018

The reaction between tetrabenzyl- or tetrakis(4-fluorobenzyl)zirconium, Zr(CH₂Ph)₄ or Zr(CH₂PhF)₄, and the sterically demanding ligand 2,6-di-tert-butylphenol (HOAr′) leads to two types of substitution products: Zr(OAr′)(CH₂Ph)₃ (Ia), Zr(OAr′)(CH₂PhF)₃ (Ib), and Zr(OAr′)₂(CH₂Ph)₂ (IIa), Zr(OAr′)₂(CH₂PhF)₂ (IIb). Addition of 4-methoxy-2,6-di-tert-butylphenol (HOAr′-OMe) to Ia generates the mixed aryl oxide Zr(OAr′)(OAr′-OMe)(CH₂Ph)₂ (IIc). Structural studies show that I contains a significant interaction between the zirconium atom and the aryl ring of one of the benzyl groups which is best described as approaching η³-bonding, whereas the ligands in II are purely σ-bound (η¹). Spectroscopic evidence (¹H and ¹³C NMR) suggests the possible retention of this type of interaction in solution. Compound Ia crystallizes in space group C2/c with a = 17.499 (10) A?, b = 10.566 (6) A?, c = 32.769 (12) A?, β = 95.79 (2)°, and Z = 8. Compound Ib crystallizes in space group P2₁/c with a = 9.480 (3) A?, b = 33.605 (19) A?, c = 10.608 (4) A?, β = 114.20 (2)°, and Z = 4. Compound IIc crystallizes in space group P2₁/n with a = 17.683 (9) A?, b = 11.342 (5) A?, c = 19.470 (1) A?, β = 101.01 (2)°, and Z = 4.