The Synthesis and Structure of Tris[2-(1,4-diisopropylimidazolyl)]phosphine Zinc Nitrate,[Pim Pr 2 i ]Zn(NO 3 ) 2 : Structural Consequences of t-Butyl versus Isopropyl Substitution in Tris(imidazoly1)phosphine Zinc Complexes

Abstract

The zinc complex [Pim^Pr₂i]Zn(NO₃)₂ has been synthesized by the reaction of tris[2-(1,4-diisopropylimidazolyl)]phosphine [Pim^Pr₂i] with Zn(NO₃)₂·6(H₂O). Comparison of the structure of [Pim^Pr₂i]Zn(NO₃)₂ with its more heavily substituted analogue {[Pim^Pri,Buf]Zn(NO₃)} (NO₃)demonstrates the rather dramatic structural consequences of replacing the t-butyl substituents in the 4-positions of the imidazolyl moieties with isopropyl groups. Specifically, [Pim^Pr₂i]Zn(NO₃)₂ exists as a six-coordinate complex with both unidentate and bidentate nitrate ligands whereas {[Pim^Pri,Buf]Zn(NO₃)} (NO₃) exists as an ion pair with a single nitrate ligand coordinated to zinc in an anisobidentate mode. [Pim^Pr₂i]Zn(NO₃)₂ is orthorhombic, Pbca (No. 61), a = 18.870(4) Å, b = 17.273(7) Å, c = 20.641(4) Å, V = 6758(3) ų, z = 8.