Spoke Adducts

Most of the reported structurally characterised neutral spoke C.-T. adducts have sulfur as the donor atom and di-iodine as the acceptor molecule.1,2 10 12 13 18,28 38 Those obtained from molecules containing selenium and di-iodine are less numerous,1,2 39 40 

1 The n( [) bond order was calculated according to the empirical logarithmic function (1) proposed by Pauling and adapted by Burgi 25 

Under such circumstances, the E-X and X-Y bond distances should be strongly correlated in C.-T. spoke adducts. In fact, it is well known that for C.-T. spoke I2-adducts with S-donors a reciprocal correlation exists between (f(I-I) and rf(S-I), which was initially proposed by F.H. Herbstein and W. Schwotzer as a hyperbola.46 Assuming a valence (bond order) model for the description of the S-I-I system within C.-T. adducts, with n(I-I) + n(E-I) = 1 

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All these extended spoke adducts structurally resemble Z -shaped X82-polyhalides (X = I, Br) in which two asymmetric X3 trihalides are bridged by an X2 molecule.15 This further supports the above-mentioned similarity in the chemical nature of asymmetric X3 trihalides and linear E-X-Y systems in C.-T. adducts. 

A polymeric structure is also observed in the adduct LE 2I2 (LE = 4,5-6z s(bromomethyl)l,3-dithiole-2-thione). LE-I2- I2 bent-shaped units, which are typical in discrete extended spoke adducts with 1 2 (LE/I2) stoichiometry, are joined head-to-tail by soft-soft I- -I interactions involving the terminal iodide atom of the LE-I2 moiety and the terminal iodide atom of the second coordinated di-iodine molecule.37... 

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