Synthesis and structure of heteroleptic ytterbium (II) tetrahydroborate complexes

Monomeric ytterbium (II) tetrahydroborate complexes supported by tris(pyrazolylborate) ligands, (TptBu,Me)Yb(BH4)(THF)0/1 were synthesized and characterized. The synthesis of (TptBu,Me)Yb(BH4)(THF) was found to depend on both solvent and alkali metal borohydride used. The synthesis proceeded optimally using NaBH4 in acetonitrile. The structure of (TptBu,Me)Yb(BH4)(THF) revealed a monomeric ytterbium (II) center in which the tetrahydroborate ligand is κ3 coordinated to the ytterbium center. A similar structure is proposed for (TptBu,Me)Yb(BH4) based on spectroscopic evidence.