Neodymium and uranium borohydride complexes, precursors to cationic derivatives: comparison of 4f and 5f element complexes

Nd(BH4)(3)(THF)(3), 1, reacted with KCp*, KP* and K2COT (Cp* =eta-C5Me5, P* = eta-PC4Me4, COT = eta-C8H8) to form (Cp*)Nd(BH4)(2)(THF)(2), 2, [K(THF)][(P*)(2)Nd(BH4)(2)], 3 and (COT)Nd(BH4)(THF)(2), 4a, respectively. The mixed ring complexes (COT)Nd(Cp*)(THF), 6, and [(COT)Nd(P*)(THF)], 7a, the alkoxide [(COT)Nd(OEt)(THF)](2), 8, and the thiolates [Na] [(COT)Nd-((SBu)-Bu-t)(2)], 11 and [Na(THF)(2)][{(COT)Nd}(2)((SBu)-Bu-t)(3)], 12, were similarly synthesised from 4a by reaction with the alkali metal salt of the respective ligand. Protonolysis of the metal-borohydride bonds in 4a or (COT)U(BH4)(2)(THF), with NEt3HBPh4 in THF afforded the cations [(COT)Nd(THF)(4)][Bph(4)],5, [(COT)U(BH4)(THF)2][BPh4],13, and [(COT)U(HMPA)(3)][Bph(4)](2),14. These cations allowed the preparation of (COT)U(P*)(HMPA)(2), 15, [(COT)U(P*)(HMPA)(2)][BPh4], 16, and [(COT)U(HMPA)(3)][BPh4], 17. The X-ray crystal structures of [(COT)M(HMPA)(3)] [BPh4], M = Nd, 18, U, 17, have been determined, all owing comparison of Nd(III) and U(III) derivatives.