Synthesis and characterisation of light lanthanide bis-phospholyl borohydride complexes

Abstract

Organometallic lanthanide (Ln) chemistry is dominated by complexes that contain substituted cyclopentadienyl (CpR) ligands. Closely related phospholyls have received less attention, and although they have proven utility in stabilising low oxidation state Ln complexes the trivalent Ln chemistry of these ligands is limited in comparison. Herein, we synthesise two families of heteroleptic Ln3+complexes, [Ln(Htp)2(µ-BH4)]2(Htp = 2,5-di-tert-butylphospholyl;1-Ln; Ln = La, Ce, Nd, Sm), and [[Ln(Htp)2(µ-BH4)2K(S)]n(2-Ln, Ln = La, Ce, S = 2 DME,n= 2;3-Ce, Ln = Ce, S = Et2O and THF,n= 8)viathe reactions of parent [Ln(BH4)3(THF)3.5] with K(Htp), to investigate differences between Ln complexes with substituted phospholyl ligands and analogous CpRcomplexes. Complexes1-3-Lnwere characterised as appropriate by single crystal XRD, SQUID magnetometry, elemental analysis, multinuclear NMR, ATR-IR and UV-Vis-NIR spectroscopy.Ab initiocalculations reveal that small changes in the Ln3+coordination spheres of these complexes can have relatively large influences on crystal field splitting.