Hexanuclear Niobium Cluster Alcoholates – First Representatives with Isopropanolato Ligands

Abstract

AbstractFour new compounds were synthesized which belong to the so far very small group of hexanuclear niobium cluster alcoholates. These are [Mg(HOCH3)6]3[Nb6Cl12(OCH3)6]2 ⋅ 6CH3OH (1), (Ph4P)2[Nb6(OC2H5)12Cl6] (2), (Ph4P)2[Nb6(OC3H7)i4Cli8Cla6] (3) and (NC5H6)2[Nb6(OC3H7)12Cl6] (4). The last two compounds represent the first examples with isopropanolato ligands on the inner coordination sites of the octahedral metal atom cores. The X‐ray structures of 1–3 have been determined. All cluster units with alcoholato ligands on the inner sites carry 14 cluster‐based electrons (CBEs), as do all other so far known cluster alcoholates. The cluster unit in Compound 1, which carries chloride ligands on the inner coordination sites, is a 15 CBE unit. The cluster anion in 3 has four inner ligand sites occupied by isopropanolate anions, which are arranged trans to each other and define a common plane. Because of the smaller size of the alcoholato O donor atom compared to halogenido ligands matrix effects are not much or not at all present in the cluster anions of 2 and 3 (and 4) and thereby the Nb−Nb distances are much smaller than found in cluster units with halogenido ligands.