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

Bis(phenolate) ligands with benzimidazole-2-ylidene (L-1) and tetrahydropyrimidine-2-ylidene (L-2) 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 [(LH3)-H-1,2]Cl afforded chloro complexes (LScCl)-Sc-1,2(solv)(2) (solv=THF, Py) in 76-85 % yields. (LScCl)-Sc-1,2(THF)(2) were also prepared by the salt metathesis reactions of ScCl3 with [L-1,L-2]Na-2 generated from [(LH3)-H-1,2]Cl and 3 equiv. of NaN(SiMe3)(2) (-40 & DEG;C, THF) and isolated in somewhat lower yields (68-73 %). (LScCl)-Sc-2(THF)(2) was subjected to the alkylation reaction with LiCH2SiMe3 affording alkyl derivative [(LSc)-Sc-2(CH2SiMe3)](2). This compound can be alternatively prepared by the subsequent reactions of [(LH3)-H-2]Cl with equimolar amount of NaN(SiMe3)(2) and Sc(CH2SiMe3)(3)(THF)(2). In the dimeric alkyl compound [(LSc)-Sc-2(CH2SiMe3)](2), one of the phenoxide groups of the dianionic ligand is coordinated to one scandium center, while the second one features & mu;-bridging coordination with two metal centers.