Poly[[μ4-3,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b:6′,7′-e]pyrazine]di-μ-iodido-dicopper(I)]: a two-dimensional copper(I) coordination polymer

The reaction of the pyrazinethiophane ligand 3,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b:6′,7′-e]pyrazine with CuI led to the formation of a two-dimensional copper(I) coordination polymer with CuI in a trigonal–pyramidal coordination environment defined by two S and two I atoms.

In the complex, the ligand is step-shaped, as in the solidstate structure of the ligand itself (Assoumatine & Stoeckli-Evans, 2020). The conformation of the eight-membered rings fits best to the definition of a twist-boat-chair (Evans & Boeyens, 1988;Spek, 2020), with a pseudo-twofold rotation . Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A view, almost normal to plane (102), of the crystal packing of complex I.

Figure 3
A view along the b axis of the crystal packing of complex I. Hydrogen bonds are shown as dashed lines (Table 1). For clarity, only the hydrogen atoms involved in these interactions have been included.
axis bisecting bonds C1-C2 and C6-C7 in one ring and bonds C3-C4 and C10-C11 in the second ring. A search of the Cambridge Structural Database (CSD; Version 5.41, last update November 2019; Groom et al., 2016) for the benzene analogue of L, or complexes of this analogue, gave no hits. A search for the S 2 CuI 2 CuS 2 motif gave 34 hits for 33 structures (see file S1 in the supporting information). The CuÁ Á ÁCu distances of the majority of these compounds vary from ca 2.580 to 3.087 Å (largest observed distance is 3.706 Å ). For the majority of the compounds, the Cu-S bond lengths vary from 2.246 to 2.374 Å (largest observed distance is 2.531 Å ), while the Cu-I bond lengths vary from 2.498 to 2.762 Å (largest observed bond length is 3.086 Å ). It is evident from Table 2 that the bond lengths observed in complex I fall within these limits.
In the crystal of I, the layers lying parallel to plane (102) (Fig. 2) are linked by C-HÁ Á ÁI hydrogen bonds forming a supramolecular framework ( Fig. 3 and Table 1). There are no other significant intermolecular interactions present in the crystal.
Synthesis of complex I: A solution of L (20 mg, 0.06 mmol) in CHCl 3 (10 ml) was introduced into a 16 mm diameter glass tube and layered with MeCN (2 ml) as a buffer zone. Then a solution of CuI (11 mg, 0.06 mmol) in MeCN (5 ml) was added very gently to avoid possible mixing. The glass tube was sealed under an atmosphere of nitrogen and left in the dark at room temperature for at least 3 weeks, whereupon pale-yellow block-like crystals of complex I were isolated at the interface between the two solutions. Analysis for C 12 H 16 N 2 S 4 Cu 2 I 2 (M r = 697.46); calculated (%): C 20.66, H 2.32, N 4.02; found (%): C 20.90, H 2.31, N 3.93. The IR spectrum for I is shown in Fig.  S1 of the supporting information.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The data were collected with a four-circle diffractometer at RT and only one equivalent of data were measured, hence R int = 0.0. No suitable scans could be found so the crystal was equated to a sphere and the ABSSphere absorption correction was applied (PLATON; Spek, 2020). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.71 e Å −3 Δρ min = −0.69 e Å −3 data-2 IUCrData (2020). 5, x200467 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.