Sodium, magnesium and zinc complexes of mono(phenolate) heteroscorpionate ligands

Abstract

The reaction of bis(3,5-dimethylpyrazolyl)methylphenol N₂O^ArH (1) with NaH in THF formed dimeric [Na(κ²-N₂O^Ar)(THF)]₂ (2), which contains a κ²(N,O)-bound bidentate N₂O^Ar ligand. The reaction of 1 with MgⁿBu₂ gave the four-coordinate monomeric butyl compound Mg(N₂O^Ar)ⁿBu (3), whereas with ⁿBuMgCl, a mixture of products was formed, including the six-coordinate homoleptic species Mg(N₂O^Ar)₂ (4). The reaction of [Na(κ²-N₂O^Ar)(THF)]₂ with ⁿBuMgCl also gave 3, as did the redistribution reaction of MgⁿBu₂ with 4. The reaction of 1 with Mg{N(SiRMe₂)₂}₂ afforded the four-coordinate amide derivatives Mg(N₂O^Ar){N(SiRMe₂)₂} (R = Me (6) or H (7)), together with 4. The reactions of 1 with ZnMe₂ or Zn{N(SiMe₃)₂}₂ gave the monomeric compounds Zn(N₂O^Ar)Me (8) and Zn(N₂O^Ar){N(SiMe₃)₂} (9), respectively. The reaction of 9 with HCl formed Zn(N₂O^Ar)Cl (11), and subsequent addition of LiN(SiHMe₂)₂ to 11 led to Zn(N₂O^Ar){N(SiHMe₂)₂} (12). The reaction of 1 with either Zn{N(SiMe₃)₂}₂ or 9 gave Zn(N₂O^Ar)₂. The compounds 2, 3, 4, 6, 8, 9 and 11 were crystallographically characterized. Compound 7 was very active for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) but the process was very poorly controlled as judged by the M_n and polydispersity index of the polymer. Compounds 3, 8, 9 and 12 gave poor conversions to poly(ε-CL) over extended periods. N₂O^ArH = 2,4-di-tert-butyl-6-(bis(3,5-dimethylpyrazolyl)methyl)phenol.