trans-Di­aqua­bis­(pyridin-2-yl thio­phen-2-yl ketone-κ2N,O)nickel(II) bis­(tetra­fluorido­borate)

Westcott, B.L.; Nichol, G.S.

doi:10.1107/S2414314626002403

metal-organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 11| Part 3| March 2026| x260240

https://doi.org/10.1107/S2414314626002403

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trans-Diaquabis(pyridin-2-yl thiophen-2-yl ketone-κ²N,O)nickel(II) bis(tetrafluoridoborate)

Barry L. Westcott ^a ^* and Gary S. Nichol ^b

^aCentral Connecticut State University, Department of Chemistry and Biochemistry, 1615 Stanley St., New Britain, CT 06050, USA, and ^bThe University of Edinburgh, School of Chemistry, Joseph Black Building David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
^*Correspondence e-mail: [email protected]

Edited by M. Weil, Vienna University of Technology, Austria (Received 15 January 2026; accepted 6 March 2026; online 11 March 2026)

The complex title salt, [Ni(C₁₀H₇NOS)₂(H₂O)₂](BF₄)₂, has monoclinic symmetry (space group P2₁/c) with the central Ni^II atom located at an inversion center. The coordination environment around the Ni^II atom is pseudo-octahedral with bonding to pyridyl N [2.0342 (6) Å] and carbonyl O [2.0402 (5) Å] atoms from two chelating 2-thienyl 2-pyridyl ketone ligands. The remaining bonds are to water molecules [2.0989 (7) Å], which are hydrogen-bonded to BF₄⁻ counter-ions. The crystal structure was refined using nonspherical scattering factors.

Keywords: crystal structure; nickel; pyridyl ketone; hydrogen bonding.

CCDC reference: 2535729

Structure description

The ligand di-2-pyridyl ketone (dpk) displays an unusual hydration reaction in the presence of a metal ion allowing this ligand to have three distinct binding sites for metals – the two pyridyl nitrogen atoms and the diol (Efthymiou et al., 2010 ; Stamatatos & Christou, 2009 ). Derivatives of dpk, such as di-2-pyridyl ketone oxime (dpko), do not undergo this hydration reaction but can still form multiple binding sites with metals (Stoumpos et al., 2010 ). The structurally related ligand 2-thienyl-2-pyridyl ketone (tpk) changes the donor of one ring from N to S, which affects the overall electronic and structural capabilities of the compound. To date, only one metal complex with the tpk ligand has been reported (Sommerer et al., 1998 ). In this complex, only the pyridyl N – not the thienyl S – bonds with the metal ion, and the ketone remains unhydrated despite the presence of water.

The complex title salt (Fig. 1) is structurally and crystallographically similar to the previously reported Cu^II analog (Sommerer et al., 1998). The Cu^II complex salt was refined in the alternate space group of P2₁/n (versus P2₁/c) and can be considered as isoconfigurational (Lima de Faria et al., 1990 ). Both the Ni^II atom of the current structure and the Cu^II atom from the previous report sit on an inversion center with pseudo-octahedral coordination. The tpk ligands coordinate through pyridyl N [2.0342 (6) Å] and carbonyl O [2.0402 (5) Å] atoms in the equatorial plane and through oxygen atoms from water molecules in the axial positions, leading to an [O₄N₂] coordination set. The Ni—O distances with the aqua ligands are significantly shorter than in the Cu^II complex [2.0989 (7) Å versus. 2.409 (3) Å], likely due to the Jahn–Teller distortion seen for octahedral Cu^II complexes (Procter et al., 1968 ).

Figure 1
The molecular structures of cation and anion in the complex title salt. Displacement ellipsoids are drawn at the 50% probability level; only atoms of the asymmetric unit are labeled and H atoms omitted for clarity.

All other bond lengths and angles are consistent with the previously reported Cu^II complex (Sommerer et al., 1998) and Ni^II complexes with similar ligands, such as di-2-pyridyl ketone (Sue-Lein et al., 1986 ) or di-2-pyridyl ketone oxime (Stamou et al., 2025 ).

The BF₄⁻ anion acts as a hydrogen-bonding acceptor with the coordinating water molecules as donors (Table 1, Fig. 2). These medium–strong O—H⋯F interactions link adjacent complexes and anions together to form a hydrogen-bonded sheet, which propagates in the bc plane.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2a⋯F4ⁱ	0.852 (18)	1.862 (18)	2.7091 (10)	172 (2)
O2—H2b⋯F3	0.91 (2)	1.83 (2)	2.7206 (10)	164 (2)
Symmetry code: (i) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 2
The crystal structure of the complex title salt in a view along the a axis. O—H⋯F hydrogen-bonding is shown by dashed lines.

Synthesis and crystallization

Ni(BF₄)₂·6H₂O and acetonitrile were used as received from Thermo-Fisher; 2-thienyl 2-pyridyl ketone was used as received from Rieke Metals. [Ni(C₁₀H₇NOS)₂(H₂O)₂](BF₄)₂ was synthesized following a literature procedure (Sommerer et al., 1998): excess Ni(BF₄)₂·6H₂O (0.2294 g, 0.675 mmol) was combined with 2-thienyl 2-pyridyl ketone (0.1997 g, 1.10 mmol) in 35 ml of acetonitrile at room temperature affording a dark green solution, which was allowed to slowly evaporate until production and isolation of dark-green crystals suitable for X-ray diffraction (40 d).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The crystal used for data collection was twinned. Non-merohedral twinning was handled with CrysAlis PRO (relation between the twin domains by matrix [ $[\overline{1}]$ 0 0 / 0 $[\overline{1}]$ 0 / 0.9467 0 1]) and refined to a twin scale factor of 0.4990 (6). The crystal structure was refined using nonspherical scattering factors, with all atoms refined anisotropically by using the ‘final' default settings of NoSpherA2 (Kleemiss et al., 2021 ); ORCA 5.0 (Neese, 2022 ) was used for quantum mechanical calculations. The latter programs are implemented in OLEX2 (Dolomanov et al., 2009 ). The _olex2_refinement_description section of the CIF gives further details.

Table 2
Experimental details

Crystal data
Chemical formula	[Ni(C₁₀H₇NOS)₂(H₂O)₂](BF₄)₂
M_r	646.84
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	7.07483 (19), 11.9935 (3), 15.2159 (4)
β (°)	102.760 (3)
V (Å³)	1259.22 (6)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	1.03
Crystal size (mm)	0.26 × 0.17 × 0.13 × 0.10 (radius)

Data collection
Diffractometer	XtaLAB Synergy, Single source at home/near, HyPix-Arc 100
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2024 )
T_min, T_max	0.857, 0.858
No. of measured, independent and observed [I ≥ 2u(I)] reflections	10509, 10509, 9767
R_int	0.048
(sin θ/λ)_max (Å⁻¹)	0.848

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.086, 1.04
No. of reflections	10509
No. of parameters	260
No. of restraints	111
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	1.02, −0.47
Computer programs: CrysAlis PRO (Rigaku OD, 2024), SHELXS (Sheldrick, 2008 ), OLEX2.refine (Bourhis et al., 2015 ), NoSpherA2 (Kleemiss et al., 2021), OLEX2 (Dolomanov et al., 2009), Mercury (Macrae et al., 2020 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 2535729

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314626002403/wm4244sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314626002403/wm4244Isup2.hkl

checkCIF report

Computing details top

trans-Diaquabis(pyridin-2-yl thiophen-2-yl ketone-κ²N,O)nickel(II) bis(tetrafluoridoborate) top

Crystal data top

[Ni(C₁₀H₇NOS)₂(H₂O)₂](BF₄)₂	F(000) = 653.806
M_r = 646.84	D_x = 1.706 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.07483 (19) Å	Cell parameters from 13596 reflections
b = 11.9935 (3) Å	θ = 2.2–37.0°
c = 15.2159 (4) Å	µ = 1.03 mm⁻¹
β = 102.760 (3)°	T = 100 K
V = 1259.22 (6) Å³	Block, dark yellow
Z = 2	0.26 × 0.17 × 0.13 × 0.10 (radius) mm

Data collection top

XtaLAB Synergy, Single source at home/near, HyPix-Arc 100 diffractometer	10509 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source	9767 reflections with I ≥ 2u(I)
Graphite monochromator	R_int = 0.048
Detector resolution: 10.0000 pixels mm^-1	θ_max = 37.1°, θ_min = 2.2°
ω scans	h = −11→11
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2024)	k = −20→20
T_min = 0.857, T_max = 0.858	l = −25→25
10509 measured reflections

Refinement top

Refinement on F²	0 constraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F² > 2σ(F²)] = 0.030	All H-atom parameters refined
wR(F²) = 0.086	w = 1/[σ²(F_o²) + (0.0571P)² + 0.1359P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = −0.001
10509 reflections	Δρ_max = 1.02 e Å⁻³
260 parameters	Δρ_min = −0.46 e Å⁻³
111 restraints

Special details top

Refinement. NoSpherA2 refinement, some displacement ellipsoid restraints used. Non-merohedral twinning was handled with CrysAlisPro, twin law [-1 0 0 / 0 -1 0 / 0.9467 0 1] and refined twin scale factor 0.4990 (6).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Ni1	0.0	0.5	0.0	0.01554 (3)
S1	0.51294 (3)	0.714938 (19)	0.195111 (15)	0.02452 (4)
O1	0.20854 (7)	0.60036 (5)	0.07412 (4)	0.01866 (9)
O2	−0.10841 (9)	0.46202 (6)	0.11422 (5)	0.02351 (10)
H2a	−0.122 (3)	0.3961 (16)	0.1328 (14)	0.051 (4)
H2b	−0.062 (3)	0.5008 (14)	0.1661 (14)	0.038 (5)
N2	−0.14605 (7)	0.64682 (5)	−0.00535 (5)	0.01763 (10)
C1	−0.33236 (9)	0.66168 (7)	−0.04418 (6)	0.02221 (13)
H1	−0.407 (2)	0.5867 (17)	−0.0779 (14)	0.051 (5)
C2	−0.42673 (10)	0.76294 (8)	−0.03927 (6)	0.02484 (15)
H2	−0.5776 (18)	0.7711 (16)	−0.0713 (13)	0.040 (4)
C3	−0.32397 (11)	0.84908 (7)	0.01029 (7)	0.02557 (15)
H3	−0.3928 (19)	0.9261 (14)	0.0201 (12)	0.035 (4)
C4	−0.13057 (10)	0.83255 (6)	0.05346 (6)	0.02240 (13)
H4	−0.047 (2)	0.8930 (16)	0.0989 (13)	0.043 (4)
C5	−0.04442 (9)	0.73122 (6)	0.04249 (5)	0.01673 (10)
C6	0.16137 (8)	0.69937 (6)	0.08269 (5)	0.01650 (10)
C7	0.30595 (9)	0.77502 (6)	0.13156 (5)	0.01887 (11)
C8	0.31606 (11)	0.89175 (7)	0.13509 (6)	0.02567 (14)
H8	0.217 (2)	0.9425 (13)	0.1003 (12)	0.059 (5)
C9	0.49357 (14)	0.92843 (9)	0.18999 (8)	0.03150 (18)
H9	0.527 (3)	1.0200 (18)	0.206 (2)	0.080 (9)
C10	0.61176 (13)	0.84113 (9)	0.22691 (7)	0.03060 (17)
H10	0.754 (2)	0.8531 (17)	0.2664 (15)	0.059 (6)
F1	0.16379 (8)	0.59372 (6)	0.40965 (5)	0.03488 (13)
F2	−0.13872 (8)	0.63709 (9)	0.33296 (5)	0.04540 (19)
F3	0.08886 (10)	0.58187 (7)	0.25713 (6)	0.04152 (17)
F4	0.11487 (11)	0.75000 (6)	0.32510 (6)	0.03963 (15)
B1	0.05459 (10)	0.63984 (7)	0.33141 (6)	0.01851 (12)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ni1	0.01687 (5)	0.01203 (5)	0.01510 (6)	0.00016 (3)	−0.00211 (4)	−0.00188 (4)
S1	0.02372 (7)	0.02472 (9)	0.02122 (9)	−0.00632 (5)	−0.00344 (6)	0.00232 (7)
O1	0.01799 (17)	0.0133 (2)	0.0212 (2)	0.00127 (13)	−0.00320 (15)	−0.00312 (18)
O2	0.0323 (2)	0.0169 (3)	0.0205 (3)	−0.00054 (18)	0.0039 (2)	−0.0011 (2)
H2a	0.081 (11)	0.026 (4)	0.040 (8)	−0.014 (3)	0.002 (6)	0.004 (2)
H2b	0.074 (12)	0.017 (7)	0.018 (5)	−0.007 (5)	−0.001 (4)	0.003 (3)
N2	0.01724 (19)	0.0151 (2)	0.0179 (3)	0.00239 (15)	−0.00166 (16)	0.0000 (2)
C1	0.0179 (2)	0.0233 (3)	0.0222 (3)	0.00361 (19)	−0.0023 (2)	0.0012 (3)
H1	0.036 (7)	0.034 (6)	0.071 (14)	0.002 (3)	−0.013 (6)	−0.014 (4)
C2	0.0200 (2)	0.0272 (4)	0.0264 (4)	0.0085 (2)	0.0031 (2)	0.0062 (3)
H2	0.023 (4)	0.043 (8)	0.050 (10)	0.012 (2)	−0.003 (2)	0.002 (5)
C3	0.0258 (3)	0.0207 (3)	0.0317 (4)	0.0097 (2)	0.0094 (3)	0.0045 (3)
H3	0.031 (5)	0.028 (5)	0.044 (9)	0.014 (2)	0.003 (4)	−0.001 (3)
C4	0.0249 (3)	0.0150 (3)	0.0280 (4)	0.0045 (2)	0.0072 (2)	−0.0007 (3)
H4	0.043 (6)	0.024 (7)	0.056 (10)	0.005 (3)	0.001 (4)	−0.016 (4)
C5	0.0192 (2)	0.0119 (2)	0.0180 (3)	0.00215 (16)	0.00177 (18)	−0.0002 (2)
C6	0.0182 (2)	0.0127 (3)	0.0167 (3)	−0.00050 (16)	−0.00035 (18)	−0.0018 (2)
C7	0.0222 (2)	0.0147 (3)	0.0178 (3)	−0.00397 (17)	0.0005 (2)	−0.0022 (2)
C8	0.0301 (3)	0.0187 (3)	0.0265 (4)	−0.0087 (2)	0.0025 (3)	−0.0015 (3)
H8	0.059 (4)	0.030 (4)	0.074 (10)	−0.0002 (16)	−0.018 (3)	0.003 (2)
C9	0.0372 (4)	0.0239 (4)	0.0328 (5)	−0.0133 (3)	0.0064 (3)	−0.0097 (3)
H9	0.062 (8)	0.027 (2)	0.12 (2)	−0.0111 (14)	−0.039 (6)	−0.0161 (16)
C10	0.0308 (3)	0.0348 (5)	0.0225 (4)	−0.0144 (3)	−0.0020 (3)	−0.0054 (3)
H10	0.042 (3)	0.035 (6)	0.080 (13)	−0.0138 (15)	−0.025 (3)	−0.006 (3)
F1	0.0359 (2)	0.0336 (3)	0.0294 (3)	0.0018 (2)	−0.0050 (2)	0.0100 (3)
F2	0.0210 (2)	0.0763 (6)	0.0379 (4)	−0.0031 (2)	0.0043 (2)	0.0044 (4)
F3	0.0493 (3)	0.0429 (4)	0.0327 (3)	−0.0044 (3)	0.0096 (3)	−0.0207 (3)
F4	0.0557 (3)	0.0152 (3)	0.0485 (5)	−0.0017 (2)	0.0129 (3)	0.0015 (3)
B1	0.0191 (2)	0.0171 (3)	0.0180 (3)	−0.00108 (19)	0.0011 (2)	−0.0020 (3)

Geometric parameters (Å, º) top

Ni1—O1ⁱ	2.0402 (5)	C3—H3	1.070 (15)
Ni1—O1	2.0402 (5)	C3—C4	1.3950 (11)
Ni1—O2ⁱ	2.0989 (7)	C4—H4	1.082 (17)
Ni1—O2	2.0989 (7)	C4—C5	1.3861 (10)
Ni1—N2ⁱ	2.0342 (6)	C5—C6	1.4987 (9)
Ni1—N2	2.0342 (6)	C6—C7	1.4445 (9)
S1—C7	1.7243 (7)	C7—C8	1.4022 (11)
S1—C10	1.6924 (9)	C8—H8	0.989 (15)
O1—C6	1.2481 (8)	C8—C9	1.4160 (12)
O2—H2a	0.852 (18)	C9—H9	1.14 (2)
O2—H2b	0.91 (2)	C9—C10	1.3797 (16)
N2—C1	1.3321 (8)	C10—H10	1.060 (15)
N2—C5	1.3565 (9)	F1—B1	1.3833 (11)
C1—H1	1.109 (19)	F2—B1	1.3734 (9)
C1—C2	1.3958 (11)	F3—B1	1.3931 (11)
C2—H2	1.075 (13)	F4—B1	1.3982 (11)
C2—C3	1.3865 (14)

O1ⁱ—Ni1—O1	180.0	C4—C3—C2	119.48 (7)
O2—Ni1—O1	91.27 (2)	C4—C3—H3	119.1 (9)
O2—Ni1—O1ⁱ	88.73 (2)	H4—C4—C3	123.0 (9)
O2ⁱ—Ni1—O1	88.73 (2)	C5—C4—C3	118.66 (8)
O2ⁱ—Ni1—O1ⁱ	91.27 (2)	C5—C4—H4	118.2 (9)
O2ⁱ—Ni1—O2	180.0	C4—C5—N2	121.58 (6)
N2ⁱ—Ni1—O1ⁱ	79.07 (2)	C6—C5—N2	112.38 (6)
N2ⁱ—Ni1—O1	100.93 (2)	C6—C5—C4	125.99 (7)
N2—Ni1—O1	79.07 (2)	C5—C6—O1	117.25 (6)
N2—Ni1—O1ⁱ	100.93 (2)	C7—C6—O1	118.43 (6)
N2ⁱ—Ni1—O2ⁱ	86.89 (3)	C7—C6—C5	124.31 (6)
N2—Ni1—O2	86.89 (3)	C6—C7—S1	116.32 (5)
N2ⁱ—Ni1—O2	93.11 (3)	C8—C7—S1	111.46 (5)
N2—Ni1—O2ⁱ	93.11 (3)	C8—C7—C6	132.16 (7)
N2ⁱ—Ni1—N2	180.0	H8—C8—C7	124.7 (9)
C10—S1—C7	91.87 (4)	C9—C8—C7	111.34 (8)
C6—O1—Ni1	116.21 (4)	C9—C8—H8	123.8 (9)
H2a—O2—Ni1ⁱ	124.3 (14)	H9—C9—C8	122.7 (11)
H2b—O2—Ni1ⁱ	118.7 (13)	C10—C9—C8	112.53 (8)
H2b—O2—H2a	103.4 (17)	C10—C9—H9	124.6 (12)
C1—N2—Ni1	125.28 (5)	C9—C10—S1	112.79 (6)
C5—N2—Ni1	114.84 (4)	H10—C10—S1	124.3 (12)
C5—N2—C1	119.58 (6)	H10—C10—C9	122.8 (12)
H1—C1—N2	114.8 (9)	F2—B1—F1	110.16 (8)
C2—C1—N2	122.06 (8)	F3—B1—F1	109.54 (7)
C2—C1—H1	123.1 (9)	F3—B1—F2	110.76 (8)
H2—C2—C1	119.6 (10)	F4—B1—F1	108.43 (7)
C3—C2—C1	118.55 (6)	F4—B1—F2	110.11 (8)
C3—C2—H2	121.8 (10)	F4—B1—F3	107.79 (8)
H3—C3—C2	121.3 (8)

Ni1—O1—C6—C5	3.44 (6)	N2—C5—C6—C7	175.51 (6)
Ni1—O1—C6—C7	−177.61 (5)	C1—N2—C5—C4	1.14 (9)
Ni1—N2—C1—C2	175.01 (7)	C1—N2—C5—C6	179.00 (7)
Ni1—N2—C5—C4	−172.91 (6)	C1—C2—C3—C4	0.11 (10)
Ni1—N2—C5—C6	4.95 (6)	C2—C1—N2—C5	1.63 (10)
S1—C7—C6—O1	−14.34 (7)	C2—C3—C4—C5	2.48 (10)
S1—C7—C6—C5	164.53 (5)	C3—C4—C5—C6	179.26 (7)
S1—C7—C8—C9	−0.05 (7)	C4—C5—C6—C7	−6.74 (10)
S1—C10—C9—C8	0.81 (8)	C5—C6—C7—C8	−18.60 (10)
O1—C6—C5—N2	−5.61 (8)	C6—C7—S1—C10	177.93 (7)
O1—C6—C5—C4	172.14 (7)	C6—C7—C8—C9	−177.03 (10)
O1—C6—C7—C8	162.53 (7)	C7—S1—C10—C9	−0.71 (6)
N2—C1—C2—C3	−2.25 (10)	C7—C8—C9—C10	−0.48 (9)
N2—C5—C4—C3	−3.18 (9)	C8—C7—S1—C10	0.43 (7)

Symmetry code: (i) −x, −y+1, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2a···F4ⁱⁱ	0.852 (18)	1.862 (18)	2.7091 (10)	172 (2)
O2—H2b···F3	0.91 (2)	1.83 (2)	2.7206 (10)	164 (2)

Symmetry code: (ii) −x, y−1/2, −z+1/2.

Acknowledgements

B. Westcott thanks CSU-AAUP for research and travel funding and Dr G. Crundwell for helpful discussions.

References

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