On the reaction of nickel(II) ions with thiol­acetic acid

An unexpected mononuclear nickel thiol­ate, bis(per­thio­acetato-S,S′)nickel(II), [Ni(C₂H₃S₃)₂], has been obtained by the reaction of Ni^II ions with ­thiol­acetic acid. It consists of a planar rectangular NiS₄ unit. Weak hydrogen bonds of the type C—H...Ni form molecular ribbons along the a axis. Among the products, γ-sulfur is also detected.

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.034
• wR factor = 0.087
• Data-to-parameter ratio = 18.7

checkCIF results

No syntax errors found



ADDSYM reports no extra symmetry


 Alert Level C:



ABSTM_02  Alert C The ratio of expected to reported Tmax/Tmin(RR) is > 1.10
          Tmin and Tmax reported:      0.467     0.890
          Tmin and Tmax expected:      0.418     0.887
          RR =      1.113
          Please check that your absorption correction is appropriate.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Metal thiolates, including nickel thiolates, are a rich class of compounds and they are relevant to the coordination of metal ions by sulfur-containing amino acids in biological systems. They are also of interest as synthetic models related to metal sulfide catalysis (Krebs & Henkel, 1991). The reaction of Ni^II ions with thiolate ligands, provides a large variety of structural possibilities ranging from mononuclear to polynuclear complexes including cyclic clusters and chain fragments. So far, several cyclic nickel thiolates have been synthesized and characterized by diffraction techniques, nevertheless, the governing factors of the degree of oligomerization of cyclic or chain nickel thiolates are still unknown. We believe that the study of structural systematics and relationships may lead to an understanding of the architecture of these compounds in order to design new cyclic clusters. Recently, we have reported the synthesis and structures of a pentanuclear and a hexanuclear cyclic nickel thiolates where the thiolate ligands were only different by the substituents on the β-C atom (Mahmoudkhani & Langer, 1999a,b). In order to understand the effect of electronic modulations on α-C atom of thiolate ligand, we have undertaken the reaction of Ni^II ions with thiolacetic acid. To our surprise, instead of a cyclic cluster, we obtained a mononuclear nickel thiolate, (I), in which the primary thiolcarboxylate ligand was transformed to a perthiocarboxylate ligand. This is to our best knowledge, the first example of an alkylperthiocarboxylato–metal complex, although there are some reports on the structure of arylperthiocarboxylate-metal complexes (Coucouvanis et al., 1985; Coucouvanis & Fackler, 1967; Fackler et al., 1968; Lanferdi et al., 1988).

These complexes are in general prepared by an oxidative addition of sulfur to the corresponding dithiocarboxylate–metal complex. But formation of this mononuclear nickel thiolate from the reaction of Ni^II ions with thiolacetic acid, seems to be rather unusual and unique. Furthermore, we have also detected the formation of γ-sulfur by this reaction which makes the interpretation much more complicated. Complex (I) crystallizes in the monoclinic system with space group P2₁/n. The structure is centrosymmetric and the asymmetric unit contains only a half of the molecule. The complex consists of a planar rectangular NiS₄ unit with no trace of bridging by thiolate-S atom. The atomic numbering for the complex (I) is presented in Fig. 1. The bond distances and angles are about the same order as for other sulfur-rich nickel thiolates with a similar skeleton. The structure exhibits a hydrogen mediated interaction in the form of a weak hydrogen bonds of the type C—H···M forming molecular ribbons along a axis (see Fig. 2). The ability of metal centers to be involved in hydrogen bonds and hydrogen mediated interactions has been recently reviewed by Desiraju & Steiner (1999). For complex (I), the interaction C—H···Ni with an H···Ni distance of 3.15 Å and an angle of 134.3°, lies just in the range 2.5–3.2 Å to be regarded as a weak C—H···M hydrogen bond, and is shorter than the sum of van der Waals radii of 3.5 Å.

S2. Experimental

Complex (I) has been obtained by a microscale reaction of NiCl₂^.H₂O (Aldrich) and thiolacetic acid (Aldrich) in the presence of KOH in ethanol as solvent according to the method reported elsewhere (Mahmoudkhani & Langer, 1999a,b). Solvents were removed by vacuum distillation·The products were then isolated by microextraction with benzene and subsequent crystallization from benzene–acetone solution. Crystals of (I) suitable for X-ray diffraction analysis were obtained after few days by slow evaporation of the solution in acetone when allowed to stand over silica gel in a desiccator.

S3. Refinement

H atoms were constrained to the ideal geometry using an appropriate riding model. The C—H distances (0.96 Å) and C—C—H angles (109.5°) were kept fixed, while the torsion angles were allowed to refine with the starting position based on threefold averaged circular Fourier synthesis.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT and SADABS (Sheldrick, 2001); program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure of (I). Displacement ellipsoids are shown at the 50% probability level.
	Fig. 2. The molecular ribbons formed by weak hydrogen bonds in the crystal structure of (I).

(BMN)

Crystal data

[Ni(C2H3S3)2]	F(000) = 308
Mr = 305.16	Dx = 1.942 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 5.3169 (3) Å	Cell parameters from 3360 reflections
b = 6.1524 (3) Å	θ = 1–25°
c = 15.9722 (8) Å	µ = 2.99 mm^−1
β = 92.50 (1)°	T = 297 K
V = 521.98 (5) Å^3	Parallepide, dark red
Z = 2	0.30 × 0.25 × 0.04 mm

Data collection

Siemens SMART CCD diffractometer	992 independent reflections
Radiation source: fine-focus sealed tube	848 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
Detector resolution: no pixels mm^-1	θmax = 25.7°, θmin = 2.6°
ω scans	h = −6→6
Absorption correction: multi-scan Blessing (1995)	k = −7→7
Tmin = 0.467, Tmax = 0.890	l = −19→19
4984 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.087	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0565P)^2] where P = (Fo^2 + 2Fc^2)/3
992 reflections	(Δ/σ)max = 0.001
53 parameters	Δρmax = 0.56 e Å^−3
0 restraints	Δρmin = −0.46 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ni1	0.0000	0.0000	0.0000	0.0387 (2)
S3	0.07836 (17)	−0.17320 (15)	0.11602 (5)	0.0607 (3)
S2	0.35389 (19)	−0.00717 (14)	0.18086 (6)	0.0579 (3)
S1	0.27462 (17)	0.25107 (13)	0.02763 (5)	0.0542 (3)
C2	0.6249 (6)	0.3537 (6)	0.1523 (2)	0.0622 (9)
H2A	0.6870	0.3053	0.2065	0.093*
H2B	0.5583	0.4981	0.1568	0.093*
H2C	0.7600	0.3541	0.1143	0.093*
C1	0.4217 (6)	0.2036 (5)	0.12013 (18)	0.0464 (7)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0409 (3)	0.0398 (3)	0.0349 (3)	−0.0043 (2)	−0.0047 (2)	−0.00078 (19)
S3	0.0718 (6)	0.0588 (5)	0.0495 (5)	−0.0227 (4)	−0.0204 (4)	0.0135 (4)
S2	0.0594 (6)	0.0647 (6)	0.0477 (5)	−0.0121 (4)	−0.0191 (4)	0.0079 (3)
S1	0.0613 (5)	0.0536 (5)	0.0466 (5)	−0.0189 (4)	−0.0124 (4)	0.0057 (3)
C2	0.0541 (19)	0.074 (2)	0.057 (2)	−0.0187 (17)	−0.0132 (16)	−0.0069 (17)
C1	0.0419 (15)	0.0531 (18)	0.0436 (16)	−0.0037 (13)	−0.0034 (12)	−0.0053 (13)

Geometric parameters (Å, º)

Ni1—S1	2.1579 (8)	S1—C1	1.667 (3)
Ni1—S1^i	2.1579 (8)	C2—C1	1.496 (4)
Ni1—S3^i	2.1623 (8)	C2—H2A	0.96
Ni1—S3	2.1623 (8)	C2—H2B	0.96
S3—S2	2.0322 (12)	C2—H2C	0.96
S2—C1	1.668 (3)
S1—Ni1—S1^i	180.00 (5)	C1—C2—H2A	109.5
S1—Ni1—S3^i	85.75 (3)	C1—C2—H2B	109.5
S1^i—Ni1—S3^i	94.25 (3)	H2A—C2—H2B	109.5
S1—Ni1—S3	94.25 (3)	C1—C2—H2C	109.5
S1^i—Ni1—S3	85.75 (3)	H2A—C2—H2C	109.5
S3^i—Ni1—S3	180.00 (5)	H2B—C2—H2C	109.5
S2—S3—Ni1	107.26 (4)	C2—C1—S1	120.0 (2)
C1—S2—S3	105.29 (11)	C2—C1—S2	116.8 (2)
C1—S1—Ni1	110.05 (11)	S1—C1—S2	123.14 (18)

Symmetry code: (i) −x, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2C···Ni1^ii	0.96	3.15	3.880 (4)	134

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