Bulky guanidinate stabilized homoleptic magnesium, calcium and zinc complexes and their catalytic activity in the Tishchenko reaction.

Bulky guanidinate stabilized homoleptic complexes of [LM(thf) n L] [L = {ArNC (N i Pr 2 )NAr} (Ar = 2,6- Me 2 –C 6 H 3 )]; M = Mg, Ca, and Zn; n = 0–1) have been synthesized with three different synthetic routes. First, treatment of bis{bis(trimethylsilyl)amide}s of Mg, Ca, and Zn i.e. [M{(N(SiMe 3 ) 2 } 2 ] (M = Mg, Ca(thf) 2 , and Zn) with free guanidine ligand (LH) at 80 ° C, elimination of NH(SiMe 3 ) 2 and formation of [LM(thf) n L] (M = Mg, Ca and Zn; n = 0–1) ( 3 – 5 ) complexes were occurred. Second, the reaction of two equivalents of potassium salt of LH with metal dihalides via salt metathesis led to the formation of homoleptic complexes. Third, the reaction between MR 2 (M = Mg, Ca, Zn; R = alkyl or OTf) and LH at reflux temperature, formation of bis(guanidinate) magnesium, calcium, and zinc complexes have been observed. The solid state structures of LH( 1 ), LK( 2 ) and all three bis(guanidinate) magnesium, calcium and zinc complexes ( 3 – 5 ) were confirmed by X-ray structural analysis. Furthermore, dimerization of a range of aromatic, heteroaromatic and aliphatic aldehydes (Tishchenko reaction) has been demonstrated by using catalysts 3 – 5 . [ABSTRACT FROM AUTHOR]