Sc3+ Chloro and Alkyl Complexes Coordinated by Pincer NHC-Tethered Bis(phenolate) Ligands

Abstract

Bis(phenolate) ligands with benzimidazole-2-ylidene (L1) and tetrahydropyrimidine-2-ylidene (L2) linkers proved to be suitable coordination environments for the synthesis of isolable Sc3+ chloro and alkyl complexes. The treatment of Sc(CH2SiMe3)3(THF)2 with equimolar amounts of [L1,2H3]Cl afforded chloro complexes L1,2ScCl(solv)2 (solv=THF, Py) in 76–85 % yields. L1,2ScCl(THF)2 were also prepared by the salt metathesis reactions of ScCl3 with [L1,2]Na2 generated from [L1,2H3]Cl and 3 equiv. of NaN(SiMe3)2 (−40 °C, THF) and isolated in somewhat lower yields (68–73 %). L2ScCl(THF)2 was subjected to the alkylation reaction with LiCH2SiMe3 affording alkyl derivative [L2Sc(CH2SiMe3)]2. This compound can be alternatively prepared by the subsequent reactions of [L2H3]Cl with equimolar amount of NaN(SiMe3)2 and Sc(CH2SiMe3)3(THF)2. In the dimeric alkyl compound [L2Sc(CH2SiMe3)]2, one of the phenoxide groups of the dianionic ligand is coordinated to one scandium center, while the second one features μ-bridging coordination with two metal centers.