Variable co-ordination numbers in 1∶1 adducts of silver(I) tetrakis(pyrazolyl)borates with tertiary phosphines

Abstract

Silver(I) derivatives containing tertiary phosphines and anionic tetrakis(pyrazol-1-yl)borates were prepared from AgO₃SCF₃, PR₃ (R = phenyl, benzyl, cyclohexyl, 2,4,6-Me₃C₆H₂, o-, m- or p-tolyl) or PPh₂R′ (R′ = methyl or ethyl) and K[B(pz)₄] or K[B(mpz)₄] (Hpz = pyrazole, Hmpz = 3-methylpyrazole) and characterized through analytical and spectral (IR, ¹H, ¹³C and ³¹P NMR) measurements. These compounds are stable, soluble in chlorinated solvents, and non-electrolytes in CH₂Cl₂ and acetone. Room-temperature single-crystal structural characterizations were made for several of them. The pyrazolyl ligand is potentially maximally tridentate, and the maximally four-co-ordinate array about the silver potentially of threefold symmetry (excepting the fourth pz moiety) where the symmetry of the phosphine permits. The variation in the silver(I) co-ordination number and environment in various combinations of various degrees of steric interaction among the above entities has been explored. The reactivity of [{AgB(pz)₄}{P(C₆H₄Me-m)₃}] and [{AgB(pz)₄}{P(C₆H₄Me-o)₃}] towards unidentate N-, S- and P-donors was also investigated.