Effect of Magnesium Bond on the Competition Between Hydrogen and Halogen Bonds and the Induction of Proton and Halogen Transfer. Issue 12 (25th April 2018)

• Record Type: Journal Article
• Authors: Xu, Hui‐Li; Li, Qing‐Zhong; Scheiner, Steve
• Is Part Of: Chemphyschem. Volume 19:Issue 12(2018)
• Page Start: 1456
• Page End: 1464
• Publication Date: 2018-04-25
• Subjects: atoms in molecules -- cooperativity -- energy decomposition -- molecular electrostatic potential -- natural bond orbital; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201800102
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: HOX (X=Cl, Br, I, and At) can engage in either a H‐bond (HB) or halogen bond (XB) with a base‐like HCN, NH3, and imidazole. Although the former is energetically preferred for X=Cl and Br, it is the XB that is more stable for At, with I showing little preference. MgY2 forms a Mg‐bond with the O atom of HOX, which grows stronger in the order X=Cl<Br<I<At and Y=F<Cl<Br. When all three molecules are combined, both the Mg and the H/X bonds are cooperatively strengthened to a large degree. Rather than causing a reversal in the HB/XB competition, the Mg‐bond acts primarily to amplify the natural preference within the dimer. The Mg‐bond induces a certain degree of transfer from O to N of the bridging atom in the H/X bond. Comparison is also made with the effects of a Be‐bond. Abstract : The H/X files : The function of HOX as simultaneous electron donor and acceptor in MgY2 ⋅⋅⋅HOX⋅⋅⋅base results in positive cooperativity and a surprising strengthening of both bonds. The relative stabilities of the HB and XB in the dimers are amplified within the context of the triads. The addition of the MgB causes at least a partial migration of the bridging H/X within the respective HB/XB. In some cases, this motion is large enough that it can be characterized as a proton or halogen transfer.