research communications
Synthesis, κN)tetrakis(pyridine-κN)nickel(II)
and properties of bis(isoselenocyanato-aInstitut für Anorganische Chemie, Universität Kiel, Max-Eyth-Str. 2, 24118 Kiel, Germany
*Correspondence e-mail: cnaether@ac.uni-kiel.de
The reaction of nickel chloride hexahydrate with potassium selenocyanate and pyridine in water leads to the formation of crystals of the title complex, [Ni(NCSe)2(C5H5N)4], which were characterized by single-crystal X-ray diffraction. Its consists of discrete complexes, located on centers of inversion, in which the Ni cations are sixfold coordinated by two terminal N-bonded selenocyanate anions and four pyridine ligands within a slightly distorted octahedral coordination. In the crystal, the complexes are connected by weak C—H⋯Se interactions. PXRD investigations revealed that a pure crystalline phase has formed. In the IR and Raman spectra, the C—N stretching vibrations are observed at 2083 and 2079 cm−1, respectively, in agreement with the presence of only terminally bonded anionic ligands. Upon heating, one well-resolved mass loss is observed, in which two of the four pyridine ligands are removed, leading to a compound with the composition Ni(NCSe)2(C5H5N)2. In this compound, the C—N stretching vibration is shifted to 2108 cm−1 (Raman) and 2115 cm−1 (IR), indicating the presence of μ-1,3-bridging anionic ligands. In its PXRD pattern, very broad reflections are observed, indicating for poor crystallinity and/or very small particle size. This crystalline phase is not isotypic to its Co and Fe analogs.
CCDC reference: 2235328
1. Chemical context
Coordination compounds based on thiocanate anions are well investigated, which can partly be traced back to their versatile magnetic behavior, including antiferro- or ferromagnetic ordering as well as single-chain magnet behavior (Shurdha et al., 2013; Prananto et al., 2017; Mautner et al., 2018; Werner et al., 2014; Rams et al., 2020). In contrast, much less is known about the corresponding selenocyanate coordination compounds, which might be related to the fact that their synthesis is more difficult to achieve. This is especially the case if less chalcophilic metal cations are used and compounds with bridging anionic ligands are to be prepared. Therefore, only a very limited number of such compounds have been reported in the literature (Turpeinen, 1977; Vicente et al., 1993; Wöhlert et al., 2012). To overcome this problem, we developed a synthetic procedure that allows a more directed preparation of thio- and selenocyanate coordination compounds with bridging anionic ligands, which is based on thermal treatment of suitable precursor compounds in which the anionic ligands are only terminally bonded (Werner et al., 2015; Wriedt & Näther, 2010). Upon heating, the neutral coligands are usually stepwise removed, leading to the formation of the desired compounds with a bridging coordination as intermediates. This procedure works perfectly for the synthesis of thiocyanates but can also be used for the synthesis of selenocyanates (Wöhlert et al., 2012).
In this context we have reported on compounds with the composition M(NCSe)2(pyridine)4 (M = Fe, Co) that upon heating lose two of the pyridine coligands and transform into compounds with the composition M(NCSe)2(pyridine)2 (M = Fe, Co), in which the metal cations are linked by pairs of μ-1,3-bridging selenocyanate anions into chains (Boeckmann et al., 2012; Boeckmann & Näther, 2011). In the course of our systematic work we also became interested in the corresponding Ni compounds, which are not reported in the literature. The synthesis of the desired compound Ni(NCSe)2(pyridine)2 in solution was unsuccessful but we found that single crystals, as well as larger amounts of a microcrystalline powder with the composition Ni(NCSe)2(pyridine)4, can easily be prepared from solution. The CN stretching vibrations of the anionic ligand are observed at 2083 cm−1 in the IR and at 2079 cm−1 in the Raman spectrum, which indicates that the selenocyanate anions are only terminally bonded (Fig. S1 in the supporting information). A comparison of the experimental powder X-ray pattern with that calculated from single-crystal data reveals that a pure crystalline phase has formed (Fig. 1). Measurements using and thermogravimetry coupled to (DTA–TG–MS) show one well-resolved mass loss in which the pyridine ligands are emitted and that is accompanied with an endothermic event in the DTA curve at 140°C (Fig. 2). Upon further heating, the TG curve is poorly resolved and two additionally endothermic events are observed. The experimental mass loss of 26.4% in the first step is close to that calculated for the removal of half of the pyridine ligands (27.0%). Therefore, it can be assumed that in the first mass loss a compound with the composition Ni(NCS)2(pyridine)2 is formed that, upon further heating, loses the remaining pyridine ligands and that this event cannot be separated from the decomposition of nickel selenocyanate at higher temperatures. For this residue, IR and Raman spectroscopy show that the CN stretching vibrations are located at 2115 cm−1 in the IR and at 2108 cm−1 in the Raman spectrum, indicating that μ-1,3-bridging selenocyanate anions are present (Fig. S2). PXRD investigations proved that the reflections of the precursor compound are absent but that a residue of poor crystallinity and/or very small particle size is obtained (Fig. S3). A comparison of the experimental powder pattern with that calculated for Co(NCSe)2(pyridine)2 retrieved from literature shows that these compounds are not isotypic (Fig. S3). Indexing of this powder pattern failed.
2. Structural commentary
Single-crystal 2(pyridine)4, is isotypic to its Co, Fe, Cd and Zn analogs already described in the literature (Boeckmann & Näther, 2011; Boeckmann et al., 2011 and 2012). The consists of one crystallographically independent NiII cation that is located on a center of inversion as well as one selenocyanate anion and two pyridine ligands in a general position (Fig. 3). The Ni cations are sixfold coordinated by four pyridine coligands and two terminally N-bonded selenocyanate anions in trans-positions. Bond lengths are similar to those in the corresponding Fe and Co compounds, even if the Ni—N bond lengths are slightly shortened because of the lower ionic radii. From the bond lengths and angles (Table 1) it is obvious that the octahedra are slightly distorted.
proves that the title compound, Ni(NCSe)3. Supramolecular features
In the crystal, the Ni(NCSe)2 units are arranged in corrugated layers in the ac plane and the pyridine rings are arranged in columns that proceed along the crystallographic c-axis direction with no sign of π–π interactions (Fig. 4). There are some C—H⋯Se contacts, with angles above 150°, indicating weak hydrogen-bonding interactions (Table 2). There are additional C—H⋯N contacts, but distances and especially angles indicate that they should not correspond to any significant interactions (Table 2).
4. Database survey
Some selenocyanate compounds with pyridine as ligand have been deposited in the Cambridge Structural Database [ConQuest Version 2022.2.0, CSD Version 5.43 (March 2022); Groom et al., 2016], including isotypic compounds with composition M(NCSe)2(pyridine)4 (M = Co, Fe, Cd, Zn) in which the metal cations are octahedrally coordinated by two terminal N-bonded selenocyanate anions and four pyridine ligands (refcodes ITISOU, CAQVEX, OWOJAM and OWOHUE; Boeckmann & Näther, 2011; Boeckmann et al., 2012, 2011). For these compounds, mixed crystals with the composition Co(NCS)x(NCSe)2–x(pyridine)4 have also been reported (refcodes TIXDOW and TIXDOW01; Neumann et al., 2019).
There are compounds with the composition M(NCSe)2(pyridine)2 (M = Co, Fe, Cd) in which the metal cations are octahedrally coordinated by two terminal N- and S-bonded selenocyanate anions and two pyridine ligands and are linked by pairs of selenocyanate anions into chains (refcodes: ITISUA, CAQVIB and OWOHOY; Boeckmann & Näther, 2011; Boeckmann et al., 2012, 2011). These compounds are also isotypic. There is an additional compound of composition Zn(NCSe)2(pyridine)2 that consists of discrete complexes in which the Zn cations are tetrahedrally coordinated by two terminal N-bonded selenocyanate anions and two pyridine ligands (refcode OWOJEQ; Boeckmann et al., 2011).
One mixed-metal compound with the composition HgSr(NCSe)4(pyridine)6 is also reported, in which the Hg cations are tetrahedrally coordinated by four Se-bonded selenocyanate anions and linked to the Sr cations that are octahedrally coordinated by two N-bonded selenocyanate anions and four pyridine ligands (refcode CICLOP; Brodersen et al., 1984).
A dinuclear complex with the composition (Fe(NCS)2)2(pyridine)2((3,5-bis(pyridin-2-yl)pyrazolyl)2 is found that shows spin-crossover behavior (refcode FIZYEU; Sy et al., 2014). Finally, there is another spin-crossover complex with the composition Fe(NCSe)2(pyridine)2-2-methyldipyrido[3,2-f:2′,3′-h)(quinoxaline) pyridine solvate (refcode TISWOI; Tao et al., 2007).
5. Synthesis and crystallization
NiCl2·6H2O and K(SeCN)2 were purchased from Merck and pyridine was purchased from Alfa Aesar.
Synthesis:
Larger amounts of a microcrystalline powder were obtained by the reaction of 59.4 mg of NiCl2·6H2O (0.25 mmol) and 72.0 mg (0.5 mmol) of KSeCN in a mixture of 1.5 ml of pyridine and 1.5 ml of water by stirring for 3 d at room temperature. The precipitate was filtered off and washed with a very small amount of water. Single crystals in the form of purple blocks were obtained under the same conditions but without stirring.
Experimental details:
Differential 2O3 crucibles using a Netzsch thermobalance with skimmer coupling and a Balzer Quadrupol MS. The XRPD measurements were performed by using a Stoe Transmission Powder Diffraction System (STADI P) equipped with a linear, position-sensitive MYTHEN detector from Stoe & Cie with Cu Kα radiation. The IR data were measured using a Bruker Alpha-P ATR-IR spectrometer and the Raman spectra were measured with a Bruker Vertex 70 spectrometer.
and thermogravimetric (DTA–TG–MS) measurements were performed in a dynamic helium atmosphere in Al6. Refinement
Crystal data, data collection and structure . Hydrogen atoms were positioned with idealized geometry (C—H = 0.95 Å) and were refined with Uĩso(H) = 1.2Ueq(C) using a riding model.
details are summarized in Table 3
|
Supporting information
CCDC reference: 2235328
https://doi.org/10.1107/S2056989023000245/hb8047sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989023000245/hb8047Isup2.hkl
IR (top) and Raman spectra of compound 1. Given are the values for the CN stretching vibrations of the selenocyanate anion. DOI: https://doi.org/10.1107/S2056989023000245/hb8047sup3.jpg
IR (top) and Raman spectra of the residue obtained after the first mass loss in a TG measurement of compound 1. Given are the values for the CN stretching vibrations of the selenocyanate anion. DOI: https://doi.org/10.1107/S2056989023000245/hb8047sup4.jpg
Experimental PXRD pattern of the residue obtained after the first mass loss in a TG measurement of compound 1 (top) and calculated PXRD pattern for Co(NCSe)2(pyridine)2 retrieved from literature (bottom). DOI: https://doi.org/10.1107/S2056989023000245/hb8047sup5.jpg
Data collection: X-AREA (Stoe, 2008); cell
X-AREA (Stoe, 2008); data reduction: X-AREA (Stoe, 2008); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016/6 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 1999); software used to prepare material for publication: publCIF (Westrip, 2010).[Ni(NCSe)2(C5H5N)4] | F(000) = 1160 |
Mr = 585.07 | Dx = 1.654 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 12.4422 (10) Å | Cell parameters from 7129 reflections |
b = 13.2302 (9) Å | θ = 2.3–27.0° |
c = 15.0723 (12) Å | µ = 3.95 mm−1 |
β = 108.755 (9)° | T = 170 K |
V = 2349.4 (3) Å3 | Block, purple |
Z = 4 | 0.50 × 0.40 × 0.30 mm |
Stoe IPDS-2 diffractometer | 1971 reflections with I > 2σ(I) |
ω scans | Rint = 0.034 |
Absorption correction: numerical (X-Shape and X-Red 32; Stoe, 2008) | θmax = 27.0°, θmin = 2.3° |
Tmin = 0.486, Tmax = 0.563 | h = −15→15 |
7129 measured reflections | k = −13→16 |
2485 independent reflections | l = −19→19 |
Refinement on F2 | Primary atom site location: dual |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.030 | H-atom parameters constrained |
wR(F2) = 0.075 | w = 1/[σ2(Fo2) + (0.0461P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.02 | (Δ/σ)max < 0.001 |
2485 reflections | Δρmax = 0.89 e Å−3 |
142 parameters | Δρmin = −0.64 e Å−3 |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
Ni1 | 0.750000 | 0.750000 | 0.500000 | 0.01661 (12) | |
N11 | 0.63560 (19) | 0.62770 (17) | 0.43798 (16) | 0.0204 (5) | |
C11 | 0.6697 (3) | 0.5310 (2) | 0.4492 (2) | 0.0277 (6) | |
H11 | 0.747512 | 0.517340 | 0.481265 | 0.033* | |
C12 | 0.5971 (3) | 0.4497 (3) | 0.4165 (2) | 0.0365 (7) | |
H12 | 0.624361 | 0.382260 | 0.427221 | 0.044* | |
C13 | 0.4841 (3) | 0.4692 (3) | 0.3678 (2) | 0.0397 (8) | |
H13 | 0.432159 | 0.415397 | 0.344311 | 0.048* | |
C14 | 0.4487 (3) | 0.5685 (3) | 0.3543 (3) | 0.0391 (8) | |
H14 | 0.371805 | 0.584215 | 0.320745 | 0.047* | |
C15 | 0.5265 (3) | 0.6448 (2) | 0.3902 (2) | 0.0291 (6) | |
H15 | 0.501079 | 0.712884 | 0.380325 | 0.035* | |
N21 | 0.78775 (18) | 0.68763 (17) | 0.63947 (15) | 0.0193 (5) | |
C21 | 0.7547 (2) | 0.7336 (2) | 0.7063 (2) | 0.0258 (6) | |
H21 | 0.716401 | 0.796653 | 0.692048 | 0.031* | |
C22 | 0.7742 (3) | 0.6931 (3) | 0.7948 (2) | 0.0312 (7) | |
H22 | 0.750093 | 0.728412 | 0.839944 | 0.037* | |
C23 | 0.8288 (3) | 0.6010 (3) | 0.8172 (2) | 0.0319 (7) | |
H23 | 0.842008 | 0.571618 | 0.877261 | 0.038* | |
C24 | 0.8638 (3) | 0.5528 (2) | 0.7495 (2) | 0.0299 (6) | |
H24 | 0.901305 | 0.489356 | 0.762043 | 0.036* | |
C25 | 0.8428 (2) | 0.5993 (2) | 0.6628 (2) | 0.0244 (6) | |
H25 | 0.868951 | 0.566730 | 0.617400 | 0.029* | |
Se1 | 0.41596 (3) | 0.85023 (2) | 0.58223 (2) | 0.02991 (11) | |
C1 | 0.5366 (2) | 0.83774 (19) | 0.54277 (18) | 0.0196 (5) | |
N1 | 0.6154 (2) | 0.82749 (18) | 0.51901 (16) | 0.0228 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ni1 | 0.0135 (2) | 0.0166 (2) | 0.0203 (2) | 0.00038 (17) | 0.0062 (2) | −0.00075 (18) |
N11 | 0.0182 (12) | 0.0201 (12) | 0.0227 (11) | −0.0014 (9) | 0.0061 (10) | −0.0024 (9) |
C11 | 0.0268 (16) | 0.0216 (15) | 0.0342 (16) | 0.0006 (12) | 0.0090 (14) | −0.0016 (12) |
C12 | 0.044 (2) | 0.0225 (15) | 0.0430 (18) | −0.0059 (14) | 0.0145 (17) | −0.0052 (14) |
C13 | 0.041 (2) | 0.0353 (19) | 0.0436 (19) | −0.0199 (15) | 0.0143 (17) | −0.0140 (15) |
C14 | 0.0221 (17) | 0.041 (2) | 0.046 (2) | −0.0095 (13) | 0.0004 (16) | −0.0070 (16) |
C15 | 0.0228 (16) | 0.0275 (15) | 0.0333 (16) | −0.0016 (12) | 0.0038 (14) | −0.0019 (12) |
N21 | 0.0173 (12) | 0.0204 (11) | 0.0201 (11) | −0.0011 (9) | 0.0061 (10) | −0.0006 (9) |
C21 | 0.0231 (15) | 0.0300 (15) | 0.0244 (14) | −0.0004 (11) | 0.0078 (13) | −0.0056 (12) |
C22 | 0.0315 (17) | 0.0428 (18) | 0.0207 (13) | −0.0025 (14) | 0.0103 (14) | −0.0067 (13) |
C23 | 0.0279 (17) | 0.047 (2) | 0.0198 (14) | −0.0048 (14) | 0.0059 (14) | 0.0037 (13) |
C24 | 0.0295 (16) | 0.0296 (16) | 0.0301 (14) | 0.0048 (13) | 0.0088 (14) | 0.0073 (13) |
C25 | 0.0242 (16) | 0.0243 (15) | 0.0249 (14) | 0.0029 (11) | 0.0079 (13) | −0.0008 (11) |
Se1 | 0.02946 (18) | 0.02786 (17) | 0.04138 (19) | 0.00354 (12) | 0.02390 (15) | 0.00093 (13) |
C1 | 0.0225 (14) | 0.0150 (12) | 0.0186 (13) | 0.0024 (10) | 0.0028 (12) | −0.0001 (10) |
N1 | 0.0186 (12) | 0.0235 (12) | 0.0270 (12) | 0.0028 (9) | 0.0084 (11) | 0.0007 (9) |
Ni1—N1i | 2.061 (2) | C14—H14 | 0.9500 |
Ni1—N1 | 2.061 (2) | C15—H15 | 0.9500 |
Ni1—N11 | 2.159 (2) | N21—C25 | 1.342 (4) |
Ni1—N11i | 2.159 (2) | N21—C21 | 1.350 (3) |
Ni1—N21 | 2.165 (2) | C21—C22 | 1.384 (4) |
Ni1—N21i | 2.165 (2) | C21—H21 | 0.9500 |
N11—C15 | 1.336 (4) | C22—C23 | 1.383 (5) |
N11—C11 | 1.342 (4) | C22—H22 | 0.9500 |
C11—C12 | 1.388 (4) | C23—C24 | 1.387 (4) |
C11—H11 | 0.9500 | C23—H23 | 0.9500 |
C12—C13 | 1.385 (5) | C24—C25 | 1.391 (4) |
C12—H12 | 0.9500 | C24—H24 | 0.9500 |
C13—C14 | 1.380 (5) | C25—H25 | 0.9500 |
C13—H13 | 0.9500 | Se1—C1 | 1.792 (3) |
C14—C15 | 1.384 (4) | C1—N1 | 1.154 (3) |
N1i—Ni1—N1 | 180.0 | C13—C14—C15 | 119.1 (3) |
N1i—Ni1—N11 | 91.10 (9) | C13—C14—H14 | 120.4 |
N1—Ni1—N11 | 88.90 (9) | C15—C14—H14 | 120.4 |
N1i—Ni1—N11i | 88.90 (9) | N11—C15—C14 | 123.3 (3) |
N1—Ni1—N11i | 91.10 (9) | N11—C15—H15 | 118.3 |
N11—Ni1—N11i | 180.00 (8) | C14—C15—H15 | 118.3 |
N1i—Ni1—N21 | 90.75 (9) | C25—N21—C21 | 116.7 (2) |
N1—Ni1—N21 | 89.25 (9) | C25—N21—Ni1 | 121.25 (17) |
N11—Ni1—N21 | 92.40 (8) | C21—N21—Ni1 | 122.01 (19) |
N11i—Ni1—N21 | 87.60 (8) | N21—C21—C22 | 122.9 (3) |
N1i—Ni1—N21i | 89.25 (9) | N21—C21—H21 | 118.5 |
N1—Ni1—N21i | 90.75 (9) | C22—C21—H21 | 118.5 |
N11—Ni1—N21i | 87.61 (8) | C23—C22—C21 | 119.8 (3) |
N11i—Ni1—N21i | 92.40 (8) | C23—C22—H22 | 120.1 |
N21—Ni1—N21i | 180.0 | C21—C22—H22 | 120.1 |
C15—N11—C11 | 117.1 (3) | C22—C23—C24 | 118.1 (3) |
C15—N11—Ni1 | 121.4 (2) | C22—C23—H23 | 120.9 |
C11—N11—Ni1 | 121.5 (2) | C24—C23—H23 | 120.9 |
N11—C11—C12 | 123.4 (3) | C23—C24—C25 | 118.7 (3) |
N11—C11—H11 | 118.3 | C23—C24—H24 | 120.7 |
C12—C11—H11 | 118.3 | C25—C24—H24 | 120.7 |
C13—C12—C11 | 118.5 (3) | N21—C25—C24 | 123.8 (3) |
C13—C12—H12 | 120.7 | N21—C25—H25 | 118.1 |
C11—C12—H12 | 120.7 | C24—C25—H25 | 118.1 |
C14—C13—C12 | 118.5 (3) | N1—C1—Se1 | 178.1 (2) |
C14—C13—H13 | 120.8 | C1—N1—Ni1 | 155.6 (2) |
C12—C13—H13 | 120.8 |
Symmetry code: (i) −x+3/2, −y+3/2, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
C11—H11···Se1ii | 0.95 | 3.09 | 3.895 (3) | 144 |
C11—H11···N1i | 0.95 | 2.67 | 3.173 (4) | 114 |
C12—H12···Se1iii | 0.95 | 3.11 | 3.972 (3) | 151 |
C15—H15···N1 | 0.95 | 2.60 | 3.074 (4) | 111 |
C21—H21···N1 | 0.95 | 2.54 | 3.061 (4) | 115 |
C22—H22···Se1iv | 0.95 | 3.13 | 4.022 (3) | 157 |
C25—H25···Se1ii | 0.95 | 3.00 | 3.725 (3) | 134 |
C25—H25···N1i | 0.95 | 2.55 | 3.103 (4) | 118 |
Symmetry codes: (i) −x+3/2, −y+3/2, −z+1; (ii) x+1/2, y−1/2, z; (iii) −x+1, −y+1, −z+1; (iv) −x+1, y, −z+3/2. |
Acknowledgements
This work was supported by the state of Schleswig-Holstein.
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