# Pure Molecular Inorganic Rings: Mixed Group 14/15 Metallacycles

## TL;DR

Scientists created new inorganic rings using silicon, germanium, and heavy elements like antimony, bonded with a molybdenum atom.

## Contribution

The paper reports the first examples of three- to five-membered pure inorganic heterocycles with mixed group 14/15 atoms and a transition metal.

## Key findings

- Novel Si–Sb and Ge–Sb ring systems were synthesized, including three- and four-membered rings.
- The ring size depends on the combination of tetrel and pnictogen atoms used in the reaction.
- These metallacycles offer new reactivity possibilities for heavy group 14/15 chemistry.

## Abstract

A systematic study on the reactivity of the homodipnictogen tetrahedrane complexes [{Cp‘Mo(CO)2}2(μ,η2:2‐E2)] (E ═ P, As, Sb; Cp‘ = η5‐C5H4
tBu) towards the disilylene [LPhSi]2 and digermylene [LPhGe]2 (LPh = PhC(NtBu)2) is presented. Depending on the specific combination of tetrel and pnictogen atom, a variety of novel silicon‐pnictogen and germanium‐pnictogen heterocycles in different bonding situations were obtained. This is a significant development, as these metallacycles are unprecedented and offer new possibilities for further reactivities. These three‐ to five‐membered pure inorganic heterocycles include one Mo, one or two tetrel, and one or two pnictogen atoms in each case. Especially for the heavier pnictogen Sb, this cyclization behavior forming novel three‐ and four‐membered Si–Sb as well as five‐membered Ge–Sb ring systems has not been observed so far. These results present unique examples of heavy group 14/15 heterocycles.

The synthesis and characterization of novel mixed group 14/15 metallacycles incorporating a transition‐metal is described. All of the presented compounds were obtained by reduction of an organometallic Mo2E2 tetrahedrane using Si(I) and Ge(I) compounds, respectively. The size of the obtained metallacycles (three‐, four‐, five‐membered rings) is strongly dependent on the combination of the tetrel as well as the pnictogen atoms.