Tris(μ4-azepane-1-carbodithioato)bis(μ3-azepane-1-carbodithioato)-μ9-bromido-tetra-μ2-bromido-octacopper(I)copper(II)

The reaction of Cu(Hm-dtc)2 (H2m-dtc is azepane-1-carbodithioic acid), CuBr2 and methyl isothiocyanate yielded the title mixed-valence nonanuclear CuI/CuII compound, [Cu9Br5(C7H12NS2)5] or [CuI 8CuIIBr5(Hm-dtc)5], encapsulating a bromide anion in the center of the Cu9Br4S10 cluster cage. The cage consists of a mononuclear CuII unit [Cu(Hm-dtc)2], three μ4-bridging Hm-dtc− ligands, eight CuI ions with distorted tetrahedral or trigonal pyramidal coordination geometries and four μ2-bridging bromide anions. The incorporated central bromide anion interacts with nine Cu ions with shorter Cu—Br separations than the sum of the van der Waals radii for Cu and Br.

Single-crystal X-ray analysis reveals the formation of a new mixed -valence Cu(I)/Cu(II) cluster of formula [Cu I 8 Cu II Br 5 (Hm-dtc) 5 ]. This complex has a cage structure consisting of a mononuclear Cu(Hm-dtc) 2 unit, eight Cu ions, four Br anions and bridging µ-Hm-dtcligands, and the Br1 is incorporated in the center of the cage through bonding to the Cu3 ion. The Cu1 ion of the mononuclear units has distorted square-planar coordination geometries in which the Hmdtcligands coordinate with the Cu1 ion in four-membered chelate rings. The Cu3 ion forms a tetrahedral S 2 Br 2 coordination geometry. The other Cu ions, Cu2, Cu4, Cu5, Cu6, Cu7 and Cu8, have trigonal pyramidal S 2 Br 1 coordination geometries, where the Br1 ion is located close to the Cu ions, thereby forming a pseudo tetrahedral geometry for the Cu ions; the Cu2-Br1, Cu4-Br1, Cu5-Br1, Cu6-Br1, Cu7-Br1, Cu8-Br1 and Cu9-Br1 separations are 2.9054 (6), 2.8672 (6), 2.7825 (8), 2.9319 (6), 2.9262 (8), 2.9563 (7) and 2.9013 (7) Å, respectively; these separations are slightly larger than the Cu3-Br1 distance [2.6912 (8) Å] and smaller than that of the sum of the van der Waals radii for Cu and Br (3.25 Å). In addition, the incorporated Br1 ion is also located close to the Cu1 ion of the mononuclear Cu(Hm-dtc) 2 unit with the separation of 2.9650 (6) Å. Usually, the oxidation states of Cu complexes with dithiocarbamate ligands can be determined by the Cu-S distances. In the mononuclear Cu(Hm-dtc) 2 unit, the average Cu -S distance is 2.3185 (13) Å, which is similar to the typical Cu(II)-S distances for Cu(II) -dithiocarbamate complexes such as Cu II (Et 2 dtc) 2 [av. 2.312 (1) Å], Cu II (i-Pr 2 dtc) 2 [av. 2.2884 (7) Å] and Cu II (n-Bu 2 dtc) 2 [av. 2.308 (1) Å] (Jian et al., 1999;Ngo et al., 2003). Based on its charge neutrality, it is concluded that this complex is in the mixed-valence state with formula [Cu I 8 Cu II Br 5 (Hm-dtc) 5 ], in which the square-planar Cu1 is divalent and the other Cu ions of Cu2-Cu9 with distorted tetrahedral or trigonal pyramidal coordination geometries are monovalent.

S2. Experimental
A CHCl 3 solution (20 ml) of Cu(Hm-dtc) 2 (0.1 mmol) was placed in a 50 ml glass vessel with a screw type cap, and a mixed-solvent (10 ml) of CHCl 3 and MeOH was slowly added on the solution. Then, a MeOH solution (20 ml) of CuBr 2 (0.2 mmol) and methylisothiocyanate (1.0 mmol) was slowly added on the solution making the layers of the solutions. By the slow diffusion of the solutions, black plate-shaped single crystals were obtained after a few days standing at room temperature.

S3. Refinement
All H atoms were placed in calculated positions and refined as riding, with C-H = 0.97 Å and U iso (H) = 1.2U eq (C).

Figure 1
ORTEP view of nonanuclear Cu I /Cu II cluster with 50% probability level ellipsoids: Cu, red-brown; Br, orange; S, yellow; C, white; and N, blue. Hydrogen atoms are omitted for clarity.   Packing diagram of nonanuclear copper cluster viewed along the a axis. Hydrogen atoms are omitted for clarity.

Data collection
Rigaku R-AXIS RAPID diffractometer Detector resolution: 10.000 pixels mm -1 ω scans Absorption correction: multi-scan (ABSCOR; Rigaku, 1995) T min = 0.241, T max = 0.468 50620 measured reflections 12284 independent reflections 10468 reflections with F 2 > 2.0σ(F 2 ) R int = 0.078 Special details Geometry. ENTER SPECIAL DETAILS OF THE MOLECULAR GEOMETRY Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).