Crystal 1,4-diiodobenzene

T-shaped tridentate nodes, the diiodobenzenes as linear bidentate modules that space the nodes and ribbons compounded of consecutive rectangles are formed [155] (Fig. 11). A similar topology is present in the co-crystal CBr4/Ph4P+Br where bromide anions and carbon tetrabromide both work as tridentate notes that alternate in the ribbon [121]. 

In the earliest authentic halocarbon complex (1982), o-diiodobenzene was found to chelate to cationic Ir(III) as shown in diagram (5)." An earlier proposed example proved to be misidentified when the crystal structure was carried out. To be stable, any such complex must resist oxidative addition, hence the use of an oxidation state, Ir(III), that is only oxidized with difficulty. The normally rather weakly basic halocarbon lone pairs are often reluctant to bind, but chelation and involvement of the least electronegative hahde, iodine, favor binding as does the cationic character of the complex. A series of such complexes was soon found, including complexes of fr(I)" and a series of weakly bound dichloromethane complexes for certain systems." These solvento complexes can be very labile and so find use as precursors for binding of other weakly basic hgands. Even fluorocarbon complexes proved viable." A review of the area is available. It now seems... 

De Sanctis, S. C., Giglio, E., Pavel, V., and Quagliata, C. A study of the crystal packing of the 2 1 and 3 1 canal complexes between deoxycholic acid and p-diiodobenzene and phenanthrene. Acta Cryst. B28, 3656-3661 (1972). 

Bipyridine and 1,4-diiodobenzene crystallize in a 1 1 ratio forming 1-D chains through nitrogen-iodine interactions with N-I distances of 3.023 A [51]. Similarly, the crystallization of 4,4 -bipyridine with 1,4-diiodotetafluoroben-zene produces a 1-D chain with N I distances of 2.851 A, which is considerably... 

Dihaloalkane and arene derivatives have proved to be a rich source of crystal engineering because of the robustness of supramolecular synthons such as X - I-C=C. The interaction energy of the N - I-C bonds in the 1 1 complex of 4,4 -bipyridyl and 1,4-diiodobenzene is 13.2kJmor with the N -1 distance being 3.03 A. The analogous complex with 1,4-diiodotetrafluorobenzene has an interaction energy of... 

Figure 10 Competition between hydrogen and halogen bonding, (a) Chemical structures of (i) l,2,4,5-tefrafluoro-3,6-diiodobenzene, (ii) 1,4-dihydroxybenzene, and (iii) l,2-bis(4-pyridyl)ethane (b) supramolecnlar chain in the 1 1 multicomponent crystal formed between (i) and (iii) mediated by N- I halogen bonds [2.79 A] and (c) supramolecnlar chain in the 1 1 multicomponent crystal formed between (ii) and (iii) mediated by O—H- -N hydrogen bonds. Halogen and hydrogen bonds are shown as orange dashed hues.

Figure 8.15 (a) The stepwise formation of linear infinite halogen-bonded chains of the co-crystal of 1,4-thiomorpholine and tetrafluoro-l,4-diiodobenzene, via a finite assembly intermediate and (b) stepwise formation of infinite zig zag halogen-bonded chains of the co-crystal of 1,4-thiomorpholine and tetrafluoro-l,2-diiodobenzene. ... 

Allen EH, Goud BS, Hoy VJ, Howard JAK, Desiraju GR (1994) Molecular recognition via iodo- nitro and iodo- -cyano interactions crystal structures of the 1 1 complexes of 1,4-diiodobenzene with 1,4-dinitrobenzene and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Chem Commun 2729-2730... 

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