Functionalised [Ge₉Ni] Clusters as Homogeneous Single‐Site Catalysts for Olefin Isomerisation Reactions

Abstract

Single‐site catalysis is an increasingly vital strategy to optimise heterogeneous catalytic reactions. In an ideal case, the nature and the population of catalytically active sites are all identical, which is impossible to realise on a solid support. The idea of single site catalysts is transferred from heterogeneous to homogeneous catalysis by the incorporation of a transition metal with oxidation state 0 in the surface of a small, soluble, molecular, homoatomic germanium atom cluster that also comprises main group atoms with oxidation state close to zero. An optimised synthetic protocol for four cluster compounds Hyp3Et[Ge9Ni]PR3 (R=Ph, ptolyl, iPr, Me) is presented, in which the transition metal is embedded in Ge atoms of a polyhedral cluster. The products were characterised by NMR spectroscopy, LIFDI/MS and elemental analysis and also structurally characterised for R=iPr and Me by single crystal X‐ray structure determination comprising a closo‐[Ge9Ni] core. The catalytic potential is investigated for various olefin isomerisation reactions. The formation of an active metal site is realized by ligand dissociation, which is observed for PPh3. DFT calculations of Hyp3Et[Ge9Ni]PR3 (R=Ph, iPr, Me), Hyp3Et[Ge9Ni](tolyl) and Hyp3Et[Ge9Ni](C6H12) show that ligand exchange with substrate molecules occurs during the catalytic reaction. Since the same principle, namely a bare metal atom site at the cluster surface, applies as in single‐site heterogeneous catalysis and since in contrast to classical homogeneous catalysis the metal atom is embedded in a cluster surface, the abbreviation SSHoC for Single Site Homogeneous Catalyst is proposed for this catalyst type. Since each metal atom is catalytically active, SSHoC enable a considerable increase in efficiency of catalysts and thus allow for sustainable use of expensive and less abundant transition metals.

Effect of La3+ on the Formation of Endohedral Zintl Clusters Featuring In/Bi Shells

“…Studying Zintl clusters in general is motivated not only by the interesting geometrical and electronical structures and the insights into chemical bonding between metal atoms − but also by first hints toward catalytic properties, demonstrated recently on related p-block-based or p-/d-block-based species, − in which the Zintl compounds were used for bond activation in the catalytical hydrogenation of cyclic alkenes, for carbonyl or CO 2 reduction, and also for olefin isomerization.…”

Zintl Clusters as a Platform for Lewis Acid Catalysis

“…14,21 these systems in alkene isomerization catalysis. 22 Scheschkewitz and co-workers also mediated alkene isomerization catalysis but this time with iridium coordinated to a silicon cluster. 23 Also in 2020, Zhang and Sun encapsulated ruthenium within a [Sn 9 ] cluster, dispersed it on a CeO 2 surface, and found that it mediated the reverse water-shift reaction.…”

“…In 2020, Goicochea and Weller coordinated a deltahedral [Ge 9 ] cluster to rhodium which facilitated the hydrogenation of cyclic alkenes, and later in 2022, the same system was found to scramble H/D (Figure ). , Fässler and co-workers reported a range of [NiGe 9 ] clusters with varying phosphine ligands on Ni and employed these systems in alkene isomerization catalysis . Scheschkewitz and co-workers also mediated alkene isomerization catalysis but this time with iridium coordinated to a silicon cluster .…”