Structural Characteristics of Aryloxybismuthanes Stabilized by Hypervalent Bond Formation. Synthesis, Incorporation of 4-Methoxyphenol through Hydrogen Bonding, and Crystal Supramolecularity

10-Phenoxyphenothiabismine 5,5-dioxide (2a) and related compounds 2b,c, the first
example of an air-stable aryloxybismuthane whose bismuth−oxygen bond is not incorporated
into a ring system, were synthesized and fully characterized. Substitution of the OAr group
in 2 by phenols in solution revealed two substitution tendencies. The substitution with
2-methoxyphenol proceeded preferentially due to intramolecular coordination of the 2-methoxy oxygen atom with the bismuth atom in 10-(2-methoxyphenoxy)phenothiabismine 5,5-dioxide (2b). Furthermore, the substitution is more favorable with more acidic phenols, which
is in accord with the apicophilicity observed at an apical position in hypervalent compounds.
10-(4-Methoxyphenoxy)phenothiabismine 5,5-dioxide (2c) was found to form 10-(4-methoxyphenoxy)phenothiabismine 5,5-dioxide·4-methoxyphenol 1:1 complex (3) through hydrogen
bonding between the OH group of 4-methoxyphenol and the aryloxide oxygen atom of 2c.
Such complex formation may be the initial step of the substitution reactions. Comparison of
the X-ray crystal structures of 2b, 2c, and 3 shows that these bismuthanes adopt various
association modes, which might show potential utility of bismuth−oxygen coordinate bonds
in the construction of three-dimensional organometallic systems.