Synthesis and reactivity of trans- N, N′-dimethyl- meso-octaalkylporphyrinogen Sm(II), Eu(II) and Yb(II) complexes: Metal-based influences on the reduction of t-butyl-1,4-diazabuta-1,3-diene

Abstract

Sm(II), Eu(II) and Yb(II) complexes of doubly deprotonated trans- N, N′-dimethyl- meso-octaethylporphyrinogen were synthesised as tetrahydrofuran adducts (Sm and Eu, bis; Yb, mono) by metathetical exchange reactions of the dipotassium macrocyclic precursor complexes with the corresponding metal diiodides in tetrahydrofuran. The Sm and Eu complexes partially desolvate in non-coordinating solvents to give mono-tetrahydrofuran adducts. Subsequent reactions of the initial Eu(II) and Yb(II) complexes with 1,4-di- t-butyl-1,4-diazabuta-1,3-diene failed to yield complexes featuring the 1,4-diazabuta-1,3-diene binding to the lanthanide centres either as neutral Lewis base donors or reduced ligands, which contrasts with previous findings in the case of the analogous Sm(II) reaction. These outcomes are discussed in relation to the variety of Ln(III)–Ln(II) reduction potentials, coordination number and oxidation state dependent ionic radii of the metals and macrocycle–ancillary ligand steric interactions. The complexes were characterised by X-ray crystal structure determination, satisfactory microanalysis and NMR spectroscopy, where possible.