Synthesis and crystal structure of (1,4,7,10-tetraazacyclododecane-κ4 N)(tetrasulfido-κ2 S 1,S 4)manganese(II)

In the crystal structure of the title compound, the MnII cations are sixfold coordinated by four N atoms of a cyclen ligand and two terminal S atoms of an [S4]2− anion into discrete complexes that are connected via intermolecular N—H⋯S hydrogen bonding into a three-dimensional network.

The title compound, [Mn(S 4 )(C 8 H 20 N 4 )], was accidentally obtained by the hydrothermal reaction of Mn(ClO 4 ) 2 Á6H 2 O, cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) and Na 3 SbS 4 Á9H 2 O in water at 413 K, indicating that polysulfide anions might represent intermediates in the synthesis of thiometallate compounds using Na 3 SbS 4 Á9H 2 O as a reactant. X-ray powder diffraction proves that the sample is slightly contaminated with NaSb(OH) 6 and an unknown crystalline phase. The crystal investigated was twinned with a twofold rotation axis as the twin element, and therefore a twin refinement using data in HKLF-5 format was performed. The asymmetric unit of the title compound consists of one Mn II cation, one [S 4 ] 2À anion and one cyclen ligand in general positions. The Mn II cation is sixfold coordinated by two cis-S atoms of the [S 4 ] 2À anions, as well as four N atoms of the cyclen ligand within an irregular coordination. The complexes are linked via pairs of N-HÁ Á ÁS hydrogen bonds into chains, which are further linked into layers by additional N-HÁ Á ÁS hydrogen bonding. These layers are connected into a three-dimensional network by intermolecular N-HÁ Á ÁS and C-HÁ Á ÁS hydrogen bonding. It is noted that only one similar complex with Mn II is reported in the literature.

Chemical context
Investigations on the synthesis and crystal structures of new inorganic-organic chalcogenidometallates are an important topic in inorganic chemistry and many such compounds have been reported in the literature (Sheldrick & Wachhold, 1988;Dehnen & Melullis, 2007;Seidlhofer et al., 2010Seidlhofer et al., , 2011Wang et al., 2016;Zhou, 2016;Zhu & Dai, 2017;Nie et al., 2017). In this context, thioantimonates are of special interest because they show a variety of coordination numbers and can form networks of different dimensionality (Schur et al., 2001;Jia et al., 2004;Powell et al., 2005;Zhang et al., 2007;Liu & Zhou, 2011;Engelke et al., 2004;Puls et al., 2006). This is the reason why we have been interested in this class of compounds for several years (Bensch et al., 1997;Spetzler et al., 2004Spetzler et al., , 2005Stä hler et al., 2001;Lü hmann et al., 2008). Most of these compounds were synthesized by solvothermal reactions using the elements as reactands, which is a disadvantage for several reasons. Recently, we have found that many such compounds are more easily available if simple metal salts such as, for example, Schlippe's salt (Na 3 SbS 4 Á9H 2 O) or NaSbS 3 are used as starting materials (Anderer et al., 2014(Anderer et al., , 2016Danker et al., 2020). The major advantage of this approach is the fact that different SbS x species are present in solution, which in some cases allows the preparation of thioantimonates already at room temperature. The reactions in solution are complex, but it has been found that Schlippe's salt is unstable and forms different species such as, for example, [SbS 3 O] 3À , HS À , [S 2 O 3 ] 2À or [SbS 4 ] 3À anions (Anderer et al., 2014;Long et al., 1970;Rammelsberg, 1841;Planer-Friedrich & Wilson, 2012;Planer-Friedrich & Scheinost, 2011;Mosselmans et al., 2000).
In the course of our investigations we became interested in compounds based on cyclen as the ligand (cyclen = 1,4,7,10tetraazacyclododecane); cyclen is a tetradentate ligand that in an octahedral coordination provides two free coordination sites that can be used by the metal cation to connect to a thioantimonate network. In this context, Mn II cations are of special interest because this cation exhibits a high affinity to sulfur. Therefore, Na 3 SbS 4 Á9H 2 O was reacted with manganese perchlorate under hydrothermal conditions leading to yellow plate-like crystals, which were identified by single crystal X-ray diffraction. Surprisingly, the structure consists of discrete complexes, in which manganese is coordinated by one cyclen ligand and one tetrasulfide dianion that must have formed in situ from Na 3 SbS 4 . This finding is of special interest because it indicates that polysulfide species might represent intermediates in the synthesis of thiometallate compounds using Na 3 SbS 4 as reactant. It is noted that only one similar complex has been reported in the literature, in which the Mn II cations are linked to a tridentate chelating ligand, one water molecule and one tetrasulfide dianion, which was synthesized by a completely different route (Wieghardt et al., 1987).
Investigations using X-ray powder diffraction (XRPD) proved that the title compound was obtained as the major phase but is contaminated with small amount of mopungite [NaSb(OH) 6 ; Schrewelius, 1938;Asai, 1975) and an additional crystalline phase of unknown identity (Fig. 1). The title compound cannot be obtained as a pure crystalline phase if the reaction conditions are varied and therefore, no further investigations were performed.

Structural commentary
The asymmetric unit of the title compound consists of one Mn II cation, one tetrasulfido anion and one cyclen ligand in general positions. The Mn II cations are coordinated by two terminal S atoms of the tetrasulfido anion and the N atoms of the cyclen ligand (Fig. 2). The Mn-N bond lengths range from 2.294 (5) to 2.329 (4) Å , which corresponds to literature values ( Table 1). The Mn-S bond lengths of 2.5894 (2) and 2.6195 (2) Å (Table 1) are slightly longer that those in the Experimental and calculated XRPD powder patterns of the title compound. The reflections of side products are marked by stars.

Figure 2
Molecular structure of the title compound with atom labelling and displacement ellipsoids drawn at the 50% probability level. similar complex aqua-(-1,4-tetrasulfido)N,N 0 ,N 00 -trimethyl-1,4,7-triazacyclononanemanganese(II) (Wieghardt et al., 1987). The [S 4 ] 2À anion shows a staggered conformation with a value of the torsion angle along the S atoms of 61.7 (6) . The bond angles within this complex are far from the ideal values, which shows that the Mn II cations are in an irregular coordination ( Fig. 3 and Table 1). This arises for steric reasons, because the Mn II cation is located 1.149 (1) Å above the plane formed by the cyclene N atoms and the terminal S atoms of the tetrasulfido anion are enforced to be in cis-positions.

Supramolecular features
In the crystal structure of the title compound, the discrete complexes are linked by pairs of N-HÁ Á ÁS hydrogen bonds between atom S4 (H3) of one complex and H1 (S1) of a neighbouring complex into eight-membered rings that are condensed into chains propagating in the b-axis direction ( Fig. 4: top and Table 2). The HÁ Á ÁS distances of 2.50 and 2.48 Å and the N-HÁ Á ÁS angles of 148 and 152 indicate a relatively strong interaction ( Table 2). The terminal S atoms S4 of two neighbouring complexes act as acceptors for a second hydrogen bond to the amino H atoms H4 of these complexes, also forming eight-membered rings that in this case are located on centers of inversion ( Fig. 4: bottom and Table 2). These rings are condensed into chains that propagate along the c-axis direction (Fig. 4: bottom). As each complex is part of both of these two chains, layers are formed parallel to the bc plane (Fig. 5). The layers are linked into a three-dimensional network by C-HÁ Á ÁS and additional N-HÁ Á ÁS hydrogen bonding ( Fig. 6 and View of the Mn coordination sphere in the molecular structure of the title compound.

Figure 4
View of the chains running along the b-(top) and the c-axis (bottom) directions with intermolecular N-HÁ Á ÁS hydrogen bonds shown as dashed lines.

Figure 5
Crystal structure of the title compound with view of the layers along the a-axis direction with intermolecular N-HÁ Á ÁS hydrogen bonds shown as dashed lines.

Database survey
There is only one crystal structure reported in which Mn II cations are linked to [S 4 ] 2À anions and this compound was obtained from the reaction of manganese acetate with ammonium sulfide. This structure is similar to that of the title compound, but in this case the Mn II cation is linked to a tridentate N-donor ligand and the Mn coordination is completed by one water molecule (Wieghardt et al., 1987). Complexes with other transition-metal cations that are related to the structure of the title compound are not reported in the Cambridge Structural Database (Version 2020; Groom et al., 2016). For Zn and Ni, one complex is found in which the Ni cations are in a square-pyramidal coordination of four S atoms of two [S 4 ] 2À anions and charge balance is achieved by tetraethylammonium cations (Mü ller et al., 1983;(Coucouvanis et al., 1985). Similar compounds are also reported with Ni and Hg, but the tetraethylammonium cations are replaced by tetraphenylphosphonium cations (Coucouvanis et al., 1985;Mü ller et al., 1985;Bailey et al., 1991).

Synthesis and crystallization
Synthesis of Na 3 SbS 4 Á9H 2 O: Na 3 SbS 4 Á9H 2 O was synthesized by adding 16.6 g (0.213 mol) of Na 2 SÁxH 2 O (technical grade, purchased from Acros Organics) to 58 mL of demineralized water. This solution was heated to 323 K for 1h. Afterwards 19.6 g (0.058 mol) of Sb 2 S 3 (98%, purchased from Alfa Aesar) and 3.69 g (0.115 mol) of sulfur (min. 99%, purchased from Alfa Aesar), were added and the reaction mixture was heated to 343 K for 6 h. The reaction mixture was filtered and the filtrate was stored overnight, leading to the formation of slightly yellow crystals, that were filtered off, washed with small amounts of water and dried under vacuum (yield about 30% based on Sb 2 S 3 ).
Synthesis of the title compound: The title compound was synthesized by the reaction of 36.8 mg (0.1 mmol) of Mn(ClO 4 ) 2 Á6H 2 O (99%, purchased from Alfa Aesar), 17.2 mg (0.1 mmol) of cyclen (98%, purchased from Strem Chemicals) and 288.8 mg (0.6 mmol) of Na 3 SbS 4 Á9H 2 O. The reaction mixture was heated at 413 K for 11 d in 2 mL of water, leading to the formation of a precipitate that was filtered off. XRPD investigations proved the product to consist of the title compound as the major phase and very small amounts of NaSb(OH) 6 and an additional crystalline phase of unknown identity.
Experimental methods: The XRPD measurements were performed using a Stoe Transmission Powder Diffraction System (STADI P) with Cu Ka radiation that was equipped with a linear, position-sensitive MYTHEN detector from Stoe & Cie.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3  were refined using a riding model with U iso (H) = 1.2U eq (C). In the first refinements, poor reliability factors and several residual electron densities were found in the difference map, for which no reasonable structure model can be found, indicating twinning. PLATON (Spek, 2020) immediately detected a pseudo-twofold rotation axis as the twin element, indicating non-merohedral twinning. Therefore, the data were transformed into HKLF-5 format and a twin refinement was performed, leading to a BASF parameter of 0.473 (5) and a significant improvement of all reliability factors. PLATON detected pseudo symmetry but investigations showed the unit cell and space group to be correct. Please note that symmetryequivalent reflections had to be be merged before refinement and thus no R int value can be given.

sup-1
Acta Cryst. SHELXL2018/3 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: publCIF (Westrip, 2010). 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.