Abstract:
The planar tetracoordinate (ptC) character of Cβ in the tungstenacyclobutadiene (WCBD) from alkyne
metathesis is analyzed with the support of structural, electronic, molecular orbital and electron density
data obtained from density functional theory calculations. The ptC character of Cβ is due to 1,3-WC
bonding, which is established on the basis of the single bond-like WCβ distance in X-ray structures and
calculated structures, a catastrophe ring critical point for the WCBD ring in quantum theory of atoms-inmolecule
analysis (QTAIM) and a large difference in the 13C-NMR data of Cα and Cβ atoms. The metalloaromatic
character of WCBD is revealed by nuclear independent chemical shift (NICS) values and
diatropic ring current observed in the anisotropy of the induced current density (AICD) plot. These WCBD
structural motifs provide a new strategy to build 1-, 2- and 3-dimensional organometallic polymeric
structures containing multiple ptC centers. Several such structures are reported, and their 3-dimensional
extensions provide access to novel ptC-incorporated metal–organic frameworks.
