Coupling constants nJ(195Pt–1H), nJ(195Pt–13C) and Pt—H–C interactions in new Schiff-base complexes ofN-alkyl-1-(N-methylpyrrol-1-yl)ethanimine

Abstract

A series of complexes of the type trans-[PtCl₂(olefin)(imine)] olefin = ethene, propene, cis- or trans-but-2-ene; imine =N-alkyl-1-(N-methylpyrrol-1-yl)ethanimine; alkyl = Me, Prⁱ, Buⁱ, Bu^s, Bu^t) have been synthesized and studied by ¹H, ¹³C, and ¹⁹⁵Pt n.m.r. spectroscopic methods. The H³ and C³ of the pyrrole ring couple to ¹⁹⁵Pt with ⁿJ(¹⁹⁵Pt–¹H) 8.3 Hz and ⁿJ(¹⁹⁵Pt–¹³C) 16.6–20.5 Hz, which are too large for five- and four-bond coupling constants respectively, thereby suggesting a Pt[graphic omitted]H–C interaction. Furthermore, long-range coupling constants were observed between different protons of the imine and ¹⁹⁵Pt. In addition,¹H and ¹³C n.m.r. spectra of (η²-trans-but-2-ene) complexes show inequivalence of the proton and carbon atoms of the olefin. The ¹H, ¹³C, and ¹⁹⁵Pt data are discussed in terms of the donor and acceptor properties of the imine ligands.