Boron templated catecholphosphines as bidentate ligands in silver complexes

Abstract

Reaction of 3-[(diphenylphosphinyl)methyl]benzene-1,2-diol (1) and 4-[(diphenylphosphinyl)methyl]benzene-1,2-diol (2) with AgOTf or B(OH)₃ produced the bis-phosphine complexes 4, 5, or the borates 6, 7, respectively. All products were characterised by analytical and spectroscopic data and single-crystal X-ray diffraction studies. The anionic assembly 6 was shown to act as a template-based chelate ligand toward Ag⁺ by forming a neutral complex 8 of composition [(6)Ag] with AgOTf. Spectroscopic and single-crystal X-ray diffraction studies revealed the presence of a kinetically very stable and conformationally rigid chelate that is best described as a bis-phosphine silver complex with a distinctly non-linear P–Ag–P array and two further secondary Ag–O interactions. Reaction of 7 with AgOTf proceeded in a 2 : 2 molar ratio to give a dimeric product 9 which was, on the basis of spectroscopic data, formulated as a macrocycle of composition [(7)₂Ag₂]. The different molecular sizes of 8 and 9 was underlined by PGSE NMR measurements which gave further evidence for the formation of solvent adducts between the chelate complex 8 and DMF. Analysis of the ¹H,¹⁰⁹Ag HMQC NMR spectra of 8 provided evidence for a dependence of the ³J_Ag,H coupling on torsional angles which resembles a Karplus-type relationship.