Neutral and Dianionic Organoantimony(III) Dithiolene Complexes:  Syntheses, X-ray Crystal Structures, and Unexpected Reactivity

Abstract

The new neutral PhSb(dmid) (dmid 2-) 4,5-dithiolato-1,3-dithiol-2-one) complex has been synthesized upon reaction of deprotected 1,3,4,6-tetrathiapentalene-2,5-dione with dichlorophenylstibine. Single-crystal X-ray structure determination shows an original threedimensional network in the solid state, via Sb---O and Sb---S secondary interactions, based on an octagonal "Sb 4 S 4 " motif. Not only PhSb(dmid) but also PhSb(dmit) (dmit 2-) 4,5dithiolato-1,3-dithiole-2-thione) reacts with a second 1 equiv of dithiolate to give a series of highly reactive dianionic complexes, unknown so far. One of these complexes, [Me 4 N] 2 [PhSb-(dmid) 2 ], was structurally characterized by single-crystal X-ray measurements. Both dithiolene ligands, lying in the equatorial plane of a distorted octahedron, are unsymmetrically coordinated, with two Sb-S distances much longer than the other two. These dianionic species reacted with 1 equiv of PhSbCl 2 to give, unexpectedly, a series of Sb(V) [Ph 2 Sb(dithiolene) 2 ]complexes. The same compounds were obtained directly upon slow addition of 1 equiv of PhSbCl 2 on the corresponding dithiolate suspensions. This demonstrates that dianionic [PhSb III (dithiolene) 2 ] 2species are key intermediates in the synthesis of [Ph 2 Sb V (dithiolene) 2 ]salts. The single-crystal X-ray structure determination of the tetraethylammonium salts of [Ph 2 Sb(dmid) 2 ] -, [Ph 2 Sb(dmit) 2 ] -, and [Ph 2 Sb(dmid)(dmit)]show a distorted-octahedral coordination geometry for the Sb center with a cis configuration of the phenyl groups. This is preserved also in solution, as established by 13 C NMR. Using the same technique, combined with 1 H NMR, in a scrambling experiment, a fast dithiolene exchange has been emphasized. In the case of the [Ph 2 Sb(dmid) 2 ]salt, two polymorphs, with different folding angles along the S---S hinge, were crystallized.

Electron‐Rich Organoantimony(III) Dithiolate Complexes

“…The complex is readily soluble in THF and only sparingly soluble in other organic solvents. As described in our previous study, [25] the addition rate of PhSbCl 2 is a crucial parameter in order to reach an optimum yield of the dithiolene complex. This is related to the reactivity of 1 or 2, once formed, towards a second equivalent of dithiolate to give a highly reactive dianionic species.…”

“…This kinetic instability can be related to the flexibility of the antimony coordination sphere, leading to a multitude of ligandscrambling reactions in solution. [25] Solutions of the neutral complex 2 in THF are also unstable, since a deposit of unidentified compounds precipitated out of the solution within one day. These observations show that the complex 2 is probably not a suitable donor for electrocrystallization experiments.…”

“…The flexibility of the coordination around antimony is further demonstrated by the observation of two successive single-crystal structural phase-transitions. On the other hand, in [SbPh(dmid)], [25] secondary Sb···S contacts lead to the formation of a centrosymmetric cyclic octagonal ''Sb 4 S 4 '' motif as a result of a formal tetramerization of the [SbPh(dmid)] molecule. Such motifs are also encountered in open-framework antimony sulfides.…”

Preparation and characterization of catena-[bromo(tetrahydrofuran-O)(2-thioxo-1,3-dithiole-4,5- dithiolato)antimony(III)], [Br(THF)Sb(dmit)]n

“…Among these complexes are inorganic and organometallic Sb V compounds, e.g., [Q][Sb(dmit) 3 ] (1) [4], [Q][Ar 2 Sb(dmit) 2 ] [5,6] (2) and Sb III species, such as [Q][Sb(dmit) 2 ] (3) [7][8][9][10] and PhSb(dmit)(THF) (4) [11] (Ar = Ph or p-tolyl; Q = onium cation). In contrast to the Sb V ionic complexes, 1-2, the Sb III ionic complex, 3, exhibits inter-anion Sb-S interactions: however, all the Sb centers in 1-3 are 6-coordinate, in the case of 3 excluding the Sb lone pair.…”

Covalently bonded compounds of heavy group 15/16 elements – Synthesis, structure and potential application in material sciences

“…Known solid state structures of compounds of the general type RM(ER') 2 (type II) with threecoordinated group 15 atoms (M) in the formal oxidation state +III and two-coordinated chalcogen (E) atoms are almost exclusively limited to the corresponding antimony sulfides [66,67,68,69,70,71,72,73,74,75] and bismuth sulfides. [76] In contrast, only two compounds, In both molecules, the three-coordinated bismuth atoms adopt a corner of a trigonal pyramid as is exemplarily shown for (Me 3 Si) 2 CHBi{TeSi(SiMe 3 ) 3 } 2 (Fig.…”