Halogen Bonding with Dihalogens and Interhalogens - Halogen Bonding: Fundamentals and Applications - page 88

(87) have diiodine-based electron acceptors, but all of the halogens and
interhalogens except for dichlorine are represented. Of the diiodine com-
plexes, 60 are simple adducts, 17 are bridging, four are extended adducts,
and nine are bridged extended adducts. One ionic salt is included (LOPQIQ)
due to the presence of a simple adduct structure in the asymmetric unit
in addition to two iodonium cations closely linked to one I 3 - and an addi-
tional discrete I 3 - anion. All of the interhalogen IBr complexes are simple
adducts, as are all of the ICl complexes, except one (HAMCII) [59] which
is a bridged extended adduct, with the chlorine atoms acting as Lewis base
donors to a bridging I 2 molecule. Two of the three known Br 2 complexes
are simple adducts, while the third is bridging. In addition, three bromo
salts are known, two with S - Br + cations and Br 3 - anions (BEMLIO and
YESGUY), and one with bis-donor-iodonium cations and an I - I - an- ··· I 2 ···

ion (FIMDOU).

2.4
Arsenic and Selenium Electron Donors

Few arsenic based complexes have been characterized. Three sets of struc-
tural data (FESKAP, FESKAP01, FESKAP02), a set for a second polymorph
(FESKAP10), and a set for a toluene solvate (FUTTAP) have been reported for
triphenylarsine I 2 , and all are simple adducts, as is the same electron donor

complexed with the interhalogen IBr (CUXCON). For trimethylarsine, on the
other hand, two electron donors are bridged by a single diiodine (ZODJOR),
but with dibromine a simple ionic salt, Me 3 AsBr +

·

Br - ··· (TMASBR01), is

formed.
Like sulfur, selenium based electron donors are heavily studied due to their
potential as antithyroid agents. Of the 28 complexes reported, the majority
(20) are diiodine based, and most of these (16) are simple adducts. One di-
iodine complex is bridged, one contains only extended adducts, one contains
only bridged adducts, and one contains both bridged and extended adducts.
All of the interhalogen complexes are simple adducts except one with iodine
monobromine, which forms an extended adduct.
In addition to halogen bonded complexes or ionic salts, it is also pos-
sible for sulfur and selenium electron donors to form complexes in which
the electron donor atom inserts into the X 2 bond, giving a hypervalent
donor atom with a T-shaped geometry. It has been recently reported [147]
that for dibromine and selenium, this type of complex is favored over halo-
gen bonded complexes. While no purely halogen bonded complex is re-
ported for dibromine, there is one complex (IRABEI) in which one selenium
atom of each of several selenanthrene molecules in the asymmetric unit
does insert into a Br 2 bond, but for one of the molecules, the other sel-
enium atom forms a halogen bond with a Br 2 molecule to form a simple
adduct ( A ).