Abstract
Metal-metal bonds between metal cations are ubiquitous in coordination complexes, whereas similar bonding characteristics between non-metal and metal cations are not. Here, we report an X-ray crystal structure of a centrosymmetric complex [Ag(m-O(3)SCF(3))(2){(4MePyNO)(2)I}](2) (1-AgI), where the iodine(I) cation forms an unusual 3-centre 4-electron [O-I-O](+) halogen bond with two oxygen atoms from two 4-methylpyridine N-oxide (4MePyNO). The iodine(I) atoms from two [4MePyNO-I-ONPyMe4](+) cations, which, together with the two silver(I) atoms from the paddlewheel [Ag(m-O(3)SCF(3))(2)](2)(2-) structure, establish two unique I(+)-Ag(+) bonds at 2.863(2) Å. This bond length is characteristic of bimetallic coordination bonds such as Au(+)-Ag(+) [2.8553(6) Å], Cu(+)-Ag(+) [2.8616(9) Å], and Pt(2+)-Ag(+) [2.8602(4) Å]. Density Functional Theory calculations unambiguously support the existence of the I(+)-Ag(+) coordination bond between non-metal and metal cations in complex 1-AgI.