Bulky Hybrid C-Scorpionate/Amidinate Complexes of Lithium and Zinc

Lithiation of the bis(pyrazolyl)methanes H2C(Pz(Ad,Me))(2) (1 a) and H2C(Pz(Ph,Ph))(2) (1 b) and subsequent addition of N,N'-diisopropylcarbodiimide in THF yields [(thf)Li{(Pz(Ad,Me))(2)HC-C(=NiPr)(NiPr)}] (2 a) and [(thf)Li{(Pz(Ph,Ph))(2)HC-C(=NiPr)(NiPr)}] (2 b). For comparison reasons, the structure of [(thf)Li{(Pz(tBu,tBu))(2)HC-C(=NCy)(NCy)}] (I) has been determined as well. Protolysis with aqueous ammonium chloride solution gives (Pz(Ad,Me))(2)HC-C(=NiPr)(NHiPr) (3 a) and (Pz(Ph,Ph))(2)HC-C(=NiPr)(NHiPr) (3 b). Zincation with diethylzinc leads to the formation of [EtZn{(Pz(Ad,Me))(2)HC-C(=NiPr)(NiPr)}] (4 a) and [EtZn{(Pz(Ph,Ph))(2)HC-C(=NiPr)(NiPr)}] (4 b). The metathetical approach allows preparation and isolation of [ClZn{(Pz(Ph,Ph))(2)HC-C(=NiPr)(NiPr)}] (5). A comparison of the molecular structures of the lithium and zinc complexes allows to elucidate the influence of electronegativity on structural parameters because tetra-coordinate Li and Zn ions have very similar radii.

Automated summary

This study reveals the differences in molecular structures between lithium and zinc complexes, and elucidates the influence of electronegativity on structural parameters.