Some oxygen-donor di-N-thiocyanato–thorium(IV) and –uranium(IV) bis[hydrotris(pyrazol-1-yl)borate] complexes

Abstract

Di-N-thiocyanato–thorium(IV) and –uranium(IV) bis[hydrotris(pyrazol-1-yl)borate] complexes, M(NCS)₂[HB(pz)₃]₂·xL [pz = C₃H₃N₂; x= 1, M = Th, L = tetrahydrofuran (thf); M = U, L = thf, MeCONMe₂, PMe₂PhO, PMePh₂O, or PPh₃O; x= 2, M = Th, L = MeCONMe₂, PMe₃O, PMe₂PhO, PMePh₂O, or PPh₃O; M = U, L = PMe₃O; x= 1.5, M = Th, L = P(NMe₂)₃O], Th(NCS)₂[HB(3,5Me₂-pz)₃]₂ and U(NCS)₂[HB(3,5Me₂-pz)₃]₂·thf (3,5Me₂-pz = 3,5-dimethylpyrazol-1-yl) have been prepared. The i.r. and u.v.–visible spectra [uranium(IV) complexes only] of these compounds are reported and the effects of steric crowding on the possible bonding arrangements of the hydrotris(pyrazol-1-yl)borate ligands are discussed in terms of a cone angle factor approach to steric crowding about the metal centres in these complexes.