Electron belt-to-σ-hole switch of noncovalently bound iodine(I) atoms in dithiocarbamate metal complexes

Co-crystallization of dithiocarbamate complexes [M-II(S2CNEt2)(2)] (M = Cu 1, Ni 2, Pd 3, Pt 4) and 1,3,5-triiodotrifluorobenzene (FIB) gives an isomorphic series of (1-4)center dot 2FIB co-crystals exhibiting quadruple Cu/ Ni/Pd/Pt isostructural exchange. In the structures of (1-4)center dot 2FIB, the halogen- bonded C-I center dot center dot center dot M (Ni, Pd, Pt) and semicoordination M center dot center dot center dot I-C (Cu) metal-involving contacts were identified by X-ray diffractometry and their nature was verified theoretically. The directionality of the I sigma-hole center dot center dot center dot d(Z)(2)M(II) and M-II center dot center dot center dot I-electron belt interactions depends on the identity of a metal center: on going from a rather electrophilic Cu-II to substantially more nucleophilic Ni-II, Pd-II, and Pt-II centers, we observed the electron belt-to-s-hole switch of a noncovalently bound iodine(I) of FIB and, correspondingly, its shift from semicoordination to halogen bonding. The negative values of the electrostatic potentials (given in parentheses) were estimated for all metal centers and they decrease in the order Cu-II (-8.8) > Ni-II (-24.5) > Pd-II (-28.6) > Pt-II (-33.3 kcal mol(-1)). Despite the negative potentials at all M(II)s, the semicoordinative contact Cu center dot center dot center dot I was established by the recognition of the LP(I)-> LP*(Cu) charge transfer using natural bond orbital (NBO) analysis and the comparison of electron density (ED) and electrostatic potential (ESP) minima positions along the I center dot center dot center dot Cu bond paths. In the case of the rather nucleophilic (although positively charged) Pd-II and Pt-II centers, the contacts C-I center dot center dot center dot d(Z)(2)[Pd] and C-I center dot center dot center dot d(Z)(2)[Pt] can be attributed to the unconventional metal-involving halogen bonding; these contacts are among the strongest (4.30 and 5.42 kcal mol(-1), correspondingly) between any metal center and iodine(I)-based sigma-hole donors.

Automated summary

Co-crystallization of dithiocarbamate complexes [M-II(S2CNEt2)(2)] (M = Cu 1, Ni 2, Pd 3, Pt 4) with 1,3,5-triiodotrifluorobenzene (FIB) forms an isomorphic series of co-crystals showing quadruple Cu/Ni/Pd/Pt isostructural exchange. The negative electrostatic potentials of Cu, Ni, Pd, and Pt decrease in the order Cu-II (-8.8) > Ni-II (-24.5) > Pd-II (-28.6) > Pt-II (-33.3 kcal mol(-1)), with Cu showing a shift from semicoordination to halogen bonding due to electron belt-to-s-hole switch. Semicoordinative contact Cu•••I is established by LP(I)-> LP*(Cu) charge transfer analysis. The more nucleophilic Pd and Pt centers exhibit unconventional metal-involving halogen bonding contacts with FIB, with the strongest interactions observed between Pt and the iodine(I)-based donors.