Bridged poly(1-imidazolyl)borate silver(I) complexes containing tertiary mono(phosphine) ligands. The first structurally authenticated bis(imidazolyl)borate metal complex

Abstract

New silver(I) derivatives containing triorganophosphines and the anionic dihydrobis(1-imidazolyl)borate [H₂B(im)₂]⁻, or the tetrakis(1-imidazolyl)borate ligand, [B(im)₄]⁻, have been synthesized from reaction of AgNO₃ with PR₃ (R = phenyl, cyclohexyl, o-, m- or p-tolyl) or (PPh₂R′) (R′ = methyl or ethyl) and K{H₂B(im)₂}·DMAC [DMAC = dimethylacetamide) or K[B(im)₄]. Binuclear [Ag(PR₃)₂{(im)BX₂(im)}]₂ or polymeric [Ag(PR₃){(im)BX₂(im)}]_n (X = H or imidazolate) complexes have been obtained and fully characterized by elemental analyses and FT-IR in the solid state and by NMR (¹H and ³¹P) spectroscopy and conductivity measurements in solution. Solution data are consistent with partial dissociation of complexes, occurring through breaking of both Ag–N and Ag–P bonds. The structures of [Ag{P(C₆H₄Me-p)₃}₂{(im)BH₂(im)}]₂·2CHCl₃, [Ag{P(cy)₃}{(im)BH₂(im)}]_n and [{P(cy)₃}Ag{(im)B(im)₂(im)}]₂·MeCN have been determined by single crystal X-ray studies. The [Ag{P(cy)₃}{(im)BH₂(im)}]_n adduct is a single-stranded polymer containing three-coordinate silver atoms (PAgN₂ core), while in the two other adducts, the silver atoms are four-coordinate (P₂AgN₂ cores). In all structures the two silver atoms are bridged by independent imidazolate donors from a pair of (im)BX₂(im) moieties.