A non-metal-to-metal I<sup>+</sup>-Ag<sup>+</sup> coordination bond.

Puttreddy, Rakesh; Limberg, Niklas; Müller, Carsten; Riedel, Sebastian; Frontera, Antonio; Lundell, Jan; Rissanen, Kari · Nat Commun · 2025

basic_science · Level V

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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<sub>3</sub>SCF<sub>3</sub>)<sub>2</sub>{(4MePyNO)<sub>2</sub>I}]<sub>2</sub> (1-AgI), where the iodine(I) cation forms an unusual 3-centre 4-electron [O-I-O]<sup>+</sup> halogen bond with two oxygen atoms from two 4-methylpyridine N-oxide (4MePyNO). The iodine(I) atoms from two [4MePyNO-I-ONPyMe4]<sup>+</sup> cations, which, together with the two silver(I) atoms from the paddlewheel [Ag(m-O<sub>3</sub>SCF<sub>3</sub>)<sub>2</sub>]<sub>2</sub><sup>2-</sup> structure, establish two unique I<sup>+</sup>-Ag<sup>+</sup> bonds at 2.863(2) Å. This bond length is characteristic of bimetallic coordination bonds such as Au<sup>+</sup>-Ag<sup>+</sup> [2.8553(6) Å], Cu<sup>+</sup>-Ag<sup>+</sup> [2.8616(9) Å], and Pt<sup>2+</sup>-Ag<sup>+</sup> [2.8602(4) Å]. Density Functional Theory calculations unambiguously support the existence of the I<sup>+</sup>-Ag<sup>+</sup> coordination bond between non-metal and metal cations in complex 1-AgI.