Crystal structure of the coordination polymer catena-poly[[[(acetonitrile-κN)copper(I)]-μ3-1,3-dithiolane-κ3 S:S:S′] hexafluoridophosphate]

The title one-dimensional ribbon-like coordination polymer results from the reaction of [Cu(MeCN)4][PF6] with 1,3-dithiolane.

In a comparative study with respect to our previous work on the coordination chemistry of the open-chain dithioether analogues RS-CH 2 -SR (Chaabé ne et al., 2016;Knorr et al., 2014;Peindy et al., 2007) and in part to fill the gap between the versatile coordination chemistry of THT (see above) and the almost unexplored coordination chemistry of 1,3-dithiolane, we recently described in detail the construction and structural features of molecular clusters and coordination networks, with dimensionalities varying from 0D-2D by reacting 1,3-dithiolane and its ferrocenyl derivative substituted at the 2-position with CuX salts (X = Cl, Br, I) (Raghuvanshi et al., 2017). However, surprisingly, a survey of the Cambridge Structural Database (Groom et al., 2016), reveals that apart from our CuX-1,3-dithiolane compounds, no other unsubstituted 1,3-dithiolane complexes have been structurally characterized. We have now extended our project on the coordination chemistry of this cyclic dithioether using [Cu(MeCN) 4 ][PF 6 ] as reactant to obtain the title polymeric ionic salt-like material, which could be interesting for electrochemical investigations.

Structural commentary
We have previously described (Raghuvanshi et al., 2017) The molecular structure of the asymmetric unit of the title complex is illustrated in Fig. 1, and selected bond lengths and bond angles are given in Table 1. The ribbon-like structure is built upon individual Cu I atoms, each ligated by a datively bound MeCN ligand and interconnected to the neighbouring metal centers by two bridging dithiolane ligands (Fig. 2). Overall, the architecture of CP1 is quite reminiscent of that of the 1D polymeric tetrafluoridoborate salt [Cu(1,3-dithiane)-(MeCN)] n + (Knaust & Keller, 2003). Nevertheless, there is one difference. Whereas the asymmetric unit of the latter salt (crystallizing in the orthorhombic Sohncke space group P2 1 2 1 2 1 ) contains three unique copper(I) centers, that of CP1 (crystallizing in the orthorhombic non-centrosymmetric space group Pna2 1 ) contains only two unique Cu I atoms. Each displays a CuNS 3 four-coordinate environment; see Table 1 [L-Cu-L angles: 99.97 (7) to 119.47 (11) for Cu1, and 99.29 (11) to 118.69 (4) for Cu2]. The 4 descriptor for fourfold coordination is = 0.89 for both atoms Cu1 and Cu2, indicating that each have a trigonal-pyramidal geometry ( 4 = 1 for a perfect tetrahedral geometry, = 0 for a perfect square planar geometry and = 0.85 for a perfect trigonalpyramidal geometry; Yang et al., 2007).

Figure 2
A partial view along the b axis of the crystal packing of the title compound. For clarity, the H atoms and the PF 6 À anions have been omitted.
2.2630 (10)-2.3367 (11) Å , the mean Cu-S bond length of 2.314 (12) Å is quite similar to that in [Cu(1,3-dithiane)-(MeCN)] n + . In addition, the mean Cu-N bond distance matches well with that of [Cu(1,3-dithiane)(MeCN)] n [1.979 (4) versus 1.984 (7) Å ]. The three dithiolane ligands each have one S atom that is a two-electron donor and one S atom that is a 2 -four-electron donor. The CuÁ Á ÁCu separations of ca 3.689-3.852 Å are far above the sum of the van der Waals radii of two Cu atoms (2.8 Å ), excluding any bonding interaction. These two bonding modes lead to the formation of a ribbon-like coordination polymer, which runs parallel to the a axis, where each copper(I) center is bonded to two 2 -S atoms and one 1 -S atom ( Fig. 2 and Table 1).

Supramolecular features
The crystal packing of the title compound is illustrated in Fig. 3, and shows the ribbon-like structures, propagating along the a-axis direction, that are linked by a number of C-HÁ Á ÁF hydrogen bonds, forming a supramolecular framework ( Fig. 3 and Table 2).

Synthesis and crystallization
The reaction scheme for the synthesis of the title compound is illustrated in Fig. 4

Figure 4
Reaction scheme for the synthesis of the title compound, CP1.