852574-03-9Relevant academic research and scientific papers
Supramolecular chemistry of halogens: Complementary features of inorganic (M-X) and organic (C-X′) halogens applied to M-X...X′-C halogen bond formation
Zordan, Fiorenzo,Brammer, Lee,Sherwood, Paul
, p. 5979 - 5989 (2005)
Electronic differences between inorganic (M-X) and organic (C-X) halogens in conjunction with the anisotropic charge distribution associated with terminal halogens have been exploited in supramolecular synthesis based upon intermolecular M-X...X′-C halogen bonds. The synthesis and crystal structures of a family of compounds trans-[MCl2(NC5H 4X-3)2] (M = Pd(II), Pt(II); X = F, Cl, Br, I; NC 5H4X-3 = 3-halopyridine) are reported. With the exception of the fluoropyridine compounds, network structures propagated by M-Cl...X-C halogen bonds are adopted and involve all M-Cl and all C-X groups, M-Cl...X-C interactions show Cl...X separations shorter than van der Waals values, shorter distances being observed for heavier halogens (X). Geometries with near linear Cl...X-C angles (155-172°) and markedly bent M-Cl...X angles (92-137°) are consistently observed. DR calculations on the model dimers {trans-[MCl2(NH3)(NC 5H4X-3)]}2 show association through M-Cl...X-C (X ≠ F) interactions with geometries similar to experimental values. DFT calculations of the electrostatic potential distributions for the compounds trans-[PdCl2(NC5H4X-3)2] (X = F, Cl, Br, I) demonstrate the effectiveness of the strategy to activate C-X groups toward halogen bond formation by enhancing their electrophilicity, and explain the absence of M-Cl...F-C interactions. The M-Cl...X-C halogen bonds described here can be viewed unambiguously as nucleophile-electrophile interactions that involve an attractive electrostatic contribution. This contrasts with some types of halogen-halogen interactions previously described and suggests that M-Cl...X-C halogen bonds could provide a valuable new synthon for supramolecular chemists.
