Silyl(silylene) Coinage Metal Complexes Obtained from Isolable Cyclic Alkylsilylenes

A series
of coinage metal complexes ligated by cyclic alkylsilylenes
(3M and 4M; M = Cu, Ag, Au) were synthesized by the reaction
of the corresponding cyclic alkylsilylene, i.e., cyclic dialkylsilylene
(CDASi) 1 or cyclic alkylaminosilylene (CAASi) 2 with 0.5 equiv of MCl (M = Cu, Ag) or AuCl-tht (tht = tetrahydrothiophene).
The molecular structures of these silylene complexes determined by
XRD analysis and the DFT calculations suggested that the silylene–metal
bond distances and bond angles around the two-coordinate metal center
are dependent on the π acceptor ability and steric demands of
the silylene ligands. Complexes 3Cu and 4Ag exhibit a fluxional
behavior due to the chlorine migration between terminal silicon atoms
in solution. The ease of 1,3-Cl migration increases in the order Au
< Ag < Cu and 3 < 4. The mechanisms
of these migration reactions were investigated by DFT calculations.