Preparation, structural studies, and magnetic properties of coordination complexes of bimetallic arylplatinum compounds and pyridyl nitronyl nitroxide radicals

Abstract

Treatment of 1,3-C₆H₄I₂ with Pt(PEt₃)₄ in toluene leads to the isolation of [1,3-(Pt(PEt₃)₂I)₂C₆H₄] (2). This complex has been characterized by ¹H, ¹³C and ³¹P NMR and elemental analysis. The structure of 2 as well as that of [1,4-(Pt(PEt₃)₂I)₂C₆H₄] (1) have been determined by single crystal X-ray analysis. As expected, the platinum centers of these derivatives adopt a square planar coordination geometry with the phosphine ligands in a trans arrangement. Treatment of compounds 1 and 2 with AgPF₆ and subsequent addition of two equivalents of NITpPy (NITpPy = [2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide]) results in the formation of [1,4-(Pt(PEt₃)₂(NITpPy))₂C₆H₄]²⁺[PF₆]⁻₂ (3) and [1,3-(Pt(PEt₃)₂(NITpPy))₂C₆H₄]²⁺[PF₆]⁻₂ (4), respectively. Compounds 3 and 4 have been characterized by +ESI/TOF, IR, UV and elemental analysis. Their structures have been determined by X-ray crystallography which confirmed the coordination of a NITpPy ligand at each platinum center. As in 1 and 2, the platinum centers adopt a square planar coordination geometry with the phosphine ligands in a trans arrangement. As shown by EPR spectroscopy and SQUID magnetometry, intramolecular magnetic coupling of the coordinated NITpPy moieties does not occur.