Facile Access to Dative, Single, and Double Silicon-Metal Bonds Through M-Cl Insertion Reactions of Base-Stabilized SiII Cations

Heavier tetrylene- and tetrylyne-transition metal chemistry: it's no carbon copy

Since the late 19th century, heavier tetrylene- and tetrylyne-transition metal chemistry has formed an important cornerstone in both main-group and organometallic chemistry alike. Driven by the success of carbene systems, significant efforts have gone towards the thorough understanding of the heavier group 14 derivatives, with examples now known from across the d-block. This now leads towards applications in cooperative bond activation, and moves ultimately towards well-defined catalytic systems. This review aims to summarise this vast field, from initial discoveries of tetrylene and tetrylyne complexes, to the most recent developments in reactivity and catalysis, as a platform to the future of this exciting, blossoming field.

Tetryliumylidene ions in synthesis and catalysis

Tetryliumylidene ions ([R-E:]+), recognised for their intriguing electronic properties, have attracted considerable interest. These positively charged species, with two vacant p-orbitals and a lone pair at the E(ii) centre (E = Si, Ge, Sn, Pb), can be viewed as the combination of tetrylenes (R2E:) and tetrylium ions ([R3E]+), which makes them potent Lewis ambiphiles. Such electronic features highlight the potential of tetryliumylidenes for single-site small molecule activation and transition metal-free catalysis. The effective utilisation of the electrophilicity and nucleophilicity of tetryliumylidenes is expected to stem from appropriate ligand choice. For most of the isolated tetryliumylidenes, electron donor- and/or kinetic stabilisation is necessary. This minireview highlights the developments in tetryliumylidene syntheses and the progress of research towards their reactivity and applications in catalytic reactions.

Facile Access to Dative, Single, and Double Silicon-Metal Bonds Through M-Cl Insertion Reactions of Base-Stabilized SiII Cations

Silicon(II) cations can offer fascinating reactivity patterns due to their unique electronic structure: a lone pair of electrons, two empty p orbitals and a positive charge combined on a single silicon center. We now report the facile insertion of N-heterocyclic carbene (NHC)-stabilized silyliumylidene ions into M-Cl bonds (M=Ru, Rh), forming a series of novel chlorosilylene transition-metal complexes. Theoretical investigations revealed a reaction mechanism in which the insertion into the M-Cl bond with concomitant 1,2-migration of a silicon-bound NHC to the transition metal takes place after formation of an initial silyliumylidene transition-metal complex. The mechanism could be verified experimentally through characterization of the intermediate complexes. Furthermore, the obtained chlorosilylene complexes can be conveniently utilized as synthons to access Si-M and Si=M bonding motifs bonds through reductive dehalogenation.

Lewis base-stabilized silyliumylidene ions in transition metal coordination chemistry

An overview of the progress made in the transition metal chemistry of isolable base-stabilized silyliumylidene ions.