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

Dalton Transactions Pub Date: 2008-10-21 DOI: 10.1039/B813116C

Abstract

The reaction of bis(3,5-dimethylpyrazolyl)methylphenol N2OArH (1) with NaH in THF formed dimeric [Na(κ2-N2OAr)(THF)]2 (2), which contains a κ2(N,O)-bound bidentate N2OAr ligand. The reaction of 1 with MgnBu2 gave the four-coordinate monomeric butyl compound Mg(N2OAr)nBu (3), whereas with nBuMgCl, a mixture of products was formed, including the six-coordinate homoleptic species Mg(N2OAr)2 (4). The reaction of [Na(κ2-N2OAr)(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(N2OAr){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(N2OAr)Me (8) and Zn(N2OAr){N(SiMe3)2} (9), respectively. The reaction of 9 with HCl formed Zn(N2OAr)Cl (11), and subsequent addition of LiN(SiHMe2)2 to 11 led to Zn(N2OAr){N(SiHMe2)2} (12). The reaction of 1 with either Zn{N(SiMe3)2}2 or 9 gave Zn(N2OAr)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 Mn and polydispersity index of the polymer. Compounds 3, 8, 9 and 12 gave poor conversions to poly(ε-CL) over extended periods. N2OArH = 2,4-di-tert-butyl-6-(bis(3,5-dimethylpyrazolyl)methyl)phenol.

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