Reactivity of an NHC-Coordinated Trisilacyclopropylidene with Transition Metal Carbonyl Compounds

The
reaction of the NHC-coordinated trisilacyclopropylidene F with freshly prepared W­(CO)6–n(thf)n (n = 1,
2) yielded in addition to the targeted tungsten pentacarbonyl complex 1 the unexpected NHC-coordinated Si3W-heterocycle 2 via oxidative insertion of a W­(CO)4 unit into
the peripheral Si–Si single bond of F. The structurally
analogous insertion product 3 is selectively accessible
by reacting F with Mo­(CO)4(nbd) in 71% yield.
Moreover, F reacts selectively with Fe2(CO)9 giving rise to the iron tetracarbonyl complex 4 that can either thermally or photolytically be converted under release
of one equivalent of carbon monoxide into the NHC-coordinated Si3Fe-heterocycle 5 featuring a butterfly-type structural
motif. FT-IR spectroscopy and DFT calculations of 1 and 4 reveal strong σ-donor and negligible π-acceptor
properties of F. Natural bond orbital analysis (NBO)
and quantum theory of atoms in molecules (QTAIM) of 2, 3, and 5 give evidence for weak transannular
interactions in 2 and 3 and the presence
of a transannular bond in 5.