posted on 2017-05-04, 00:00authored byJing Xu, Xinxing Zhang, Shuang Yu, Yi-hong Ding, Kit H. Bowen
The
chemical curiosity “planar tetracoordinate carbon”
(ptC) has greatly broadened one’s knowledge of molecular bonding
motifs apart from the traditional, tetrahedral, van’t Hoff
and LeBel’s concept. Synthesized ptC examples have been reported
either in the solid state or in the gas phase, where the ptC core
is usually metalized or organometallized. Surprisingly, there has
been no experimental report on hydrogenated ptC to date. A possible
answer to this situation could be the “promiscuity”
of hydrogen when binding to other elements, which frustrates the formation
of stable ptC that is in competition with other structures. In this
Letter, we for the first time identified two hydrogenated ptC species,
CAl4H and CAl4H–, based on
a photoelectron spectroscopic and quantum chemical study. The favorable
site-selectivity of hydrogen was shown to be the bridge of the Al–Al
bond rather than the terminus of Al, manifesting the thermodynamic
preference of the 17e/18e counting rule over the 15e/16e rule.