Transition metal complexes with thio­semicarbazide-based ligands. XV. A square-pyramidal Ni^II complex with an asymmetric coordination of 2,6-di­acetyl­pyridine bis(S-methyl­iso­thio­semicarbazone)

The title compound, [di­acetyl­pyridine bis(S-methyl­iso­thio­semicarbazonato)]­iodo­nickel(II), [Ni(C₁₃H₁₈N₇S₂)I], is the first example of a complex involving the ²N coordination of the iso­thio­semicarbazide moiety. 2,6-Di­acetyl­pyridine bis(S-methyl­iso­thio­semicarbazone), as a potentially pentadentate ligand (N₅), is coordinated as a tetradentate species, whereby one (deprotonated) iso­thio­semicarbazide moiety is coordinated in the usual way (¹N⁴N), but the other (neutral) is bonded via the ²N atom only, the fourth ligator being the pyridine nitro­gen. The difference in coordination mode of the iso­thio­semicarbazide moiety is reflected in the ¹N-²N bond lengths of 1.359 (4) and 1.379 (3) Å in the deprotonated and undeprotonated moieties, respectively. The structure contains three fused chelate rings in a 5:5:6 arrangement. The six-membered ring has a non-planar conformation.

S1. Comment

Up to now, more than 60 metal complexes with isothiosemicarbazides and isothiosemicarbazones of different dentacity have been characterized by X-ray analysis (Malinovskii et al., 1985; Obadović et al., 1997; Bogdanović et al., 1999). At that, it has been found that the isothiosemicarbazone moiety is coordinated via the terminal nitrogen atoms ¹N and ⁴N. To our knowledge, the only exceptions are the Ni^II complex with diacethylmonoxime S-methylisothiosemicarbazone (Biyuskin et al., 1986) and the Pd^II complex with salicylaldehyde S-methylisothiosemicarbazide (Revenko et al., 1996), in which the isothiosemicarbazide moiety is coordinated only via ¹N and ¹N plus the alkylated sulfur atom, respectively.

The common ¹N⁴N coordination mode of both isothiosemicarbazide moieties has also been found in the pentagonal-bipyramidal Mn^II complex with 2,6-diacetylpyridine bis(S-methylisothiosemicarbazone) (L) as a pentadentate ligand (N₅), of the formula [Mn(NCS)L(MeOH)]NCS (Leovac et al., 1997).

The solved crystal structure of the Ni^II complex with the monoanion of this ligand (L—H), (I), described in the present work, represents the first example of a new mode of coordination of this class of ligands. Namely, one isothiosemicarbazide moiety is coordinated only through the nitrogen atom ²N which, together with common ¹N⁴N coordination of the other (deprotonated) isothiosemicarbazide moiety and the pyridine nitrogen, gives rise to a tetradentate character of this ligand (Fig. 1). \sch

The consequence of such an asymmetric coordination is most clearly seen as the difference in the N1—N2 and N1'-N2' bond lengths, which are 1.379 (3) and 1.359 (3) Å, as well as the location of the hydrogen atom in the neutrally coordinated isothiosemicarbazide fragment. Namely, if the isothiosemicarbazide moiety is coordinated in its neutral form in the usual way, one of the hydrogen atoms is always bound to ²N: ═ ¹N—²NH— ³C(—SR) ═⁴NH (imido form), so that this fragment has an E configuration. Such an instance has also been found in the structure of the previously mentioned Mn^II complex with L, in which a bidentate coordination (¹N⁴N) in the imido-form has been observed for the both isothiosemicarbazide fragments. In contrast to this, the neutral free ligands (Argay et al., 1983; Bourosh et al., 1987; Bourosh et al., 1989; Simonov et al., 1990) are characterized by a Z configuration with both H atoms located on the ⁴N atom: ═¹N—²N═ ³C(—SR)—⁴NH₂ (amido form). Because of the absence of the coordinated N3 atom in the titled Ni ^II complex, undeprotonated isothiosemicarbazide fragment from this complex retains a Z configuration and amido form as in the case with the non-coordinated ligands (contrary to the coordinated ligands).

The Ni atom is located in a pseudo-square-pyramidal surroundings (with the tetradentate ligand around the central ion in the basal plane and the I atom in the apical position). The bond Ni—I of 3.485 (2) Å is very elongated, and it can be considered as an electrostatic interaction between the two atoms. However, considering that the iodine is situated in the regular apical position, with angles to the corresponding coordinated atoms from the basal plane of less than 100.4°, it can be supposed that the Ni atom is in a pseudo-square-pyramidal surroundings. The basal coordination plane is slightly puckered showing a tetrahedral distortion with a maximum displacement of 0.097 (3) Å, while the Ni atom is displaced by 0.0495 (13) Å from this plane towards the apical iodine.

The basal coordination plane is characterized by the very deformed angles between the coordinated atoms and metal atom. The largest deviation shows the angle N2—Ni—N3', which is a consequence of the steric hindrance between the N3'H and N3H2 groups with the closest distance of 2.31 (5) Å between the hydrogen atoms. The N1', N2', C1', N3' fragment is nearly planar with a torsion angle of 3.4 (4)°, which is commonly observed with the isothiosemicarbazide ligands. However, in contrast to it, the corresponding N1, N2, C1, N3 fragment is not planar, the torsion angle being 167.5 (3)°. This difference is also a consequence of the ligand tendency to diminish the repulsion of the N3'H and N3H2 groups. The Ni—N1' distance is significantly shorter than the distances to the other nitrogen atoms, which could be related to the distribution of the negative charge on the deprotonated isothiosemicarbazide fragment to which N1' belongs.

The five-membered rings are almost planar. Their total puckering amplitudes are 0.074 (3) and 0.052 (2) Å for Ni,N1',N2',C1'N3' and Ni,N1',C3',C9,N4 showing half-chair and envelop conformation, respectively. The six-membered chelate ring is puckered and it assumes the conformation between half-chair and envelope, which can be explained in terms of the ⁶S₇ form (Boeyens, 1978) (the Ni atom was taken as the first atom in the ring). The puckering parameters (Cremer & Pople, 1975) for Ni,N4,C5,C3,N1,N2 sequence are q² = 0.210 (3) Å, q³ = −0.079 (3) Å, Q = 0.224 (3) Å, θ = 110.7 (9)° and ϕ = 139.4 (8)°. The maximum deviation from the best plane is 0.292 (3) Å for the N2 atom.

The crystal-packing arrangement in (I) consists of parallel layers with a shortest distance C1'···C8ⁱ of 3.455 (5) Å [symmetry code: (i) −x + 1, −y + 1, −z + 1). Inside the layers the shortest contact is between the sulfur atoms: S2···S2ⁱⁱ = 3.364 (2) Å [symmetry code: (ii) −x + 1, −y + 1, −z].

S2. Experimental

The dark-brown diamagnetic monocrystals of the title complex result from a template synthesis, i.e. the reaction of equimolar amounts of warm MeOH solutions (reflux, 40 min) of NiL'₂I₂ (L' = 3-methylisothiosemicarbazide) (Leovac et al., 1980) and 2,6-diacetylpyridine.

S3. Refinement

The structure was solved by Patterson and difference Fourier methods and refined by full-matrix least-squares methods. All H atoms were found in difference Fourier maps, but those connected to C atoms were placed at calculated positions using a riding model [isotropic displacement parameters equal to 1.2 (or 1.5 for methyl H atoms) times the equivalent isotropic displacement parameter of the parent atom]. The intensities were corrected for absorption with the program ABSORB (DeTitta, 1985).

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); data reduction: a local modification of MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97 and PARST (Nardelli, 1995).

Figures

Fig. 1. A view of the molecular structure of (I) showing the atom labels. Displacement ellipsoids are shown at the 50% probability level.

[2,6-diacetylpyridine bis(S-methylisothiosemicarbazone)]iodonickel(II)

Crystal data

[Ni(C13H18N7S2)I]	Z = 2
Mr = 522.07	F(000) = 516
Triclinic, P1	Dx = 1.878 Mg m^−3
a = 7.713 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.653 (3) Å	Cell parameters from 23 reflections
c = 12.535 (3) Å	θ = 12.1–16.6°
α = 108.08 (5)°	µ = 2.96 mm^−1
β = 101.01 (4)°	T = 293 K
γ = 101.51 (6)°	Prismatic, dark-brown
V = 923.4 (4) Å^3	0.34 × 0.29 × 0.28 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	2926 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.020
Graphite monochromator	θmax = 25.3°, θmin = 3.6°
ο/2θ scans	h = −9→9
Absorption correction: integration (ABSORB; De Titta, 1985)	k = −12→12
Tmin = 0.363, Tmax = 0.437	l = −14→15
4230 measured reflections	2 standard reflections every 120 min
3325 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: heavy-atom method
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.070	H atoms treated by a mixture of independent and constrained refinement
S = 1.36	Calculated w = 1/[σ^2(Fo^2) + (0.0337P)^2 + 0.0788P] where P = (Fo^2 + 2Fc^2)/3
3325 reflections	(Δ/σ)max < 0.001
229 parameters	Δρmax = 0.79 e Å^−3
0 restraints	Δρmin = −0.71 e Å^−3

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

	x	y	z	Uiso*/Ueq
I	−0.18566 (3)	0.16205 (2)	0.170131 (19)	0.05443 (10)
Ni	0.26735 (5)	0.24242 (4)	0.33439 (3)	0.03389 (11)
S2	0.41127 (14)	0.40533 (10)	0.07212 (8)	0.0532 (2)
N1'	0.2894 (3)	0.4240 (2)	0.3531 (2)	0.0365 (6)
N2'	0.3214 (4)	0.4686 (3)	0.2663 (2)	0.0436 (6)
N3'	0.3390 (4)	0.2432 (3)	0.1986 (2)	0.0414 (6)
C2'	0.3933 (6)	0.2423 (4)	−0.0329 (3)	0.0567 (9)
H2'1	0.4237	0.2547	−0.1004	0.085*
H2'2	0.2698	0.1846	−0.0551	0.085*
H2'3	0.4766	0.1998	0.0003	0.085*
C1'	0.3520 (4)	0.3633 (3)	0.1876 (3)	0.0402 (7)
C3'	0.2651 (4)	0.5032 (3)	0.4482 (3)	0.0370 (6)
C4'	0.2767 (5)	0.6521 (3)	0.4761 (3)	0.0466 (8)
H4'1	0.2982	0.6777	0.4117	0.070*
H4'2	0.3761	0.7061	0.5446	0.070*
H4'3	0.1634	0.6681	0.4898	0.070*
S1	0.22480 (13)	−0.20741 (8)	0.22971 (8)	0.0475 (2)
N1	0.2571 (4)	0.0114 (3)	0.4129 (2)	0.0412 (6)
N2	0.2342 (4)	0.0565 (2)	0.3206 (2)	0.0366 (5)
N3	0.1398 (5)	−0.0394 (3)	0.1206 (3)	0.0484 (7)
C1	0.1994 (4)	−0.0510 (3)	0.2211 (3)	0.0374 (7)
C2	0.1374 (6)	−0.3225 (4)	0.0806 (4)	0.0586 (10)
H2A	0.1453	−0.4128	0.0756	0.088*
H2B	0.2087	−0.2907	0.0345	0.088*
H2C	0.0113	−0.3255	0.0521	0.088*
C3	0.2496 (4)	0.0831 (3)	0.5147 (3)	0.0397 (7)
C4	0.2694 (6)	0.0132 (4)	0.6019 (3)	0.0556 (9)
H4A	0.2843	−0.0762	0.5655	0.083*
H4B	0.1615	0.0039	0.6295	0.083*
H4C	0.3752	0.0672	0.6663	0.083*
N4	0.2373 (3)	0.2970 (2)	0.4858 (2)	0.0340 (5)
C5	0.2243 (4)	0.2217 (3)	0.5537 (3)	0.0362 (6)
C6	0.1910 (5)	0.2764 (4)	0.6621 (3)	0.0448 (8)
H6	0.1769	0.2230	0.7078	0.054*
C7	0.1792 (5)	0.4094 (4)	0.7011 (3)	0.0505 (8)
H7	0.1546	0.4453	0.7725	0.061*
C8	0.2038 (5)	0.4890 (3)	0.6346 (3)	0.0466 (8)
H8	0.2004	0.5800	0.6613	0.056*
C9	0.2336 (4)	0.4308 (3)	0.5268 (3)	0.0355 (6)
H10	0.380 (5)	0.191 (4)	0.154 (3)	0.051 (11)*
H11	0.105 (6)	0.028 (5)	0.114 (4)	0.067 (13)*
H12	0.135 (5)	−0.102 (4)	0.056 (4)	0.059 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I	0.07527 (18)	0.05148 (16)	0.04053 (14)	0.03428 (13)	0.01922 (11)	0.00955 (11)
Ni	0.0480 (2)	0.0260 (2)	0.0320 (2)	0.01316 (16)	0.01684 (17)	0.01086 (16)
S2	0.0749 (6)	0.0474 (5)	0.0471 (5)	0.0148 (4)	0.0263 (4)	0.0259 (4)
N1'	0.0443 (14)	0.0279 (13)	0.0389 (14)	0.0095 (11)	0.0147 (11)	0.0127 (11)
N2'	0.0560 (16)	0.0350 (14)	0.0483 (16)	0.0146 (12)	0.0210 (13)	0.0210 (12)
N3'	0.0597 (17)	0.0349 (14)	0.0407 (15)	0.0196 (13)	0.0254 (13)	0.0178 (12)
C2'	0.067 (2)	0.061 (2)	0.0426 (19)	0.0158 (19)	0.0204 (17)	0.0176 (18)
C1'	0.0448 (17)	0.0398 (17)	0.0405 (17)	0.0121 (14)	0.0145 (14)	0.0188 (14)
C3'	0.0386 (15)	0.0274 (15)	0.0405 (16)	0.0092 (12)	0.0085 (13)	0.0075 (13)
C4'	0.055 (2)	0.0274 (16)	0.055 (2)	0.0134 (14)	0.0130 (16)	0.0121 (15)
S1	0.0674 (5)	0.0288 (4)	0.0474 (5)	0.0164 (4)	0.0161 (4)	0.0130 (4)
N1	0.0588 (16)	0.0312 (13)	0.0364 (14)	0.0140 (12)	0.0132 (12)	0.0150 (11)
N2	0.0520 (15)	0.0286 (13)	0.0308 (12)	0.0129 (11)	0.0132 (11)	0.0108 (11)
N3	0.077 (2)	0.0333 (15)	0.0349 (15)	0.0267 (15)	0.0126 (14)	0.0062 (13)
C1	0.0471 (17)	0.0324 (15)	0.0380 (16)	0.0157 (13)	0.0185 (13)	0.0129 (13)
C2	0.071 (2)	0.0321 (18)	0.062 (2)	0.0161 (17)	0.0146 (19)	0.0027 (17)
C3	0.0469 (17)	0.0370 (17)	0.0342 (16)	0.0070 (13)	0.0108 (13)	0.0145 (14)
C4	0.084 (3)	0.048 (2)	0.0428 (19)	0.0193 (19)	0.0193 (18)	0.0253 (17)
N4	0.0398 (13)	0.0293 (13)	0.0311 (12)	0.0094 (10)	0.0111 (10)	0.0077 (10)
C5	0.0395 (15)	0.0347 (16)	0.0311 (15)	0.0061 (13)	0.0093 (12)	0.0100 (13)
C6	0.0537 (19)	0.0466 (19)	0.0321 (16)	0.0087 (15)	0.0147 (14)	0.0129 (14)
C7	0.058 (2)	0.053 (2)	0.0343 (17)	0.0144 (17)	0.0195 (15)	0.0045 (15)
C8	0.0512 (19)	0.0351 (17)	0.0439 (18)	0.0109 (14)	0.0168 (15)	−0.0004 (15)
C9	0.0374 (15)	0.0286 (15)	0.0350 (15)	0.0089 (12)	0.0100 (12)	0.0043 (12)

Geometric parameters (Å, º)

Ni—N1'	1.844 (2)	S1—C2	1.793 (4)
Ni—N4	1.879 (2)	N1—C3	1.286 (4)
Ni—N3'	1.890 (3)	N1—N2	1.379 (3)
Ni—N2	1.893 (3)	N2—C1	1.343 (4)
S2—C1'	1.754 (3)	N3—C1	1.308 (4)
S2—C2'	1.785 (4)	C3—C5	1.471 (4)
N1'—C3'	1.300 (4)	C3—C4	1.503 (4)
N1'—N2'	1.359 (4)	N4—C5	1.342 (4)
N2'—C1'	1.339 (4)	N4—C9	1.365 (4)
N3'—C1'	1.315 (4)	C5—C6	1.397 (4)
C3'—C9	1.454 (4)	C6—C7	1.375 (5)
C3'—C4'	1.494 (4)	C7—C8	1.373 (5)
S1—C1	1.750 (3)	C8—C9	1.385 (4)
N1'—Ni—N4	83.92 (12)	C1—N2—Ni	125.9 (2)
N1'—Ni—N3'	80.91 (12)	N1—N2—Ni	125.0 (2)
N4—Ni—N3'	162.78 (12)	N3—C1—N2	120.1 (3)
N1'—Ni—N2	176.51 (11)	N3—C1—S1	121.3 (2)
N4—Ni—N2	93.21 (12)	N2—C1—S1	118.5 (2)
N3'—Ni—N2	102.21 (12)	N1—C3—C5	127.9 (3)
C1'—S2—C2'	103.2 (2)	N1—C3—C4	114.3 (3)
C3'—N1'—N2'	122.6 (3)	C5—C3—C4	117.8 (3)
C3'—N1'—Ni	117.7 (2)	C5—N4—C9	119.9 (3)
N2'—N1'—Ni	119.6 (2)	C5—N4—Ni	127.6 (2)
C1'—N2'—N1'	105.8 (2)	C9—N4—Ni	112.5 (2)
C1'—N3'—Ni	110.8 (2)	N4—C5—C6	120.0 (3)
N3'—C1'—N2'	122.4 (3)	N4—C5—C3	119.7 (3)
N3'—C1'—S2	125.1 (3)	C6—C5—C3	120.3 (3)
N2'—C1'—S2	112.5 (2)	C7—C6—C5	119.9 (3)
N1'—C3'—C9	111.7 (3)	C8—C7—C6	120.0 (3)
N1'—C3'—C4'	124.3 (3)	C7—C8—C9	118.6 (3)
C9—C3'—C4'	123.9 (3)	N4—C9—C8	121.5 (3)
C1—S1—C2	102.7 (2)	N4—C9—C3'	113.9 (3)
C3—N1—N2	122.5 (3)	C8—C9—C3'	124.6 (3)
C1—N2—N1	108.9 (2)
N4—Ni—N1'—C3'	−4.2 (2)	C2—S1—C1—N3	−3.9 (3)
N3'—Ni—N1'—C3'	−176.1 (3)	C2—S1—C1—N2	173.0 (3)
N2—Ni—N1'—C3'	30 (2)	N2—N1—C3—C5	−2.6 (5)
N4—Ni—N1'—N2'	178.7 (2)	N2—N1—C3—C4	177.3 (3)
N3'—Ni—N1'—N2'	6.9 (2)	N1'—Ni—N4—C5	−174.2 (3)
N2—Ni—N1'—N2'	−147 (2)	N3'—Ni—N4—C5	−145.9 (4)
C3'—N1'—N2'—C1'	175.8 (3)	N2—Ni—N4—C5	7.8 (3)
Ni—N1'—N2'—C1'	−7.4 (3)	N1'—Ni—N4—C9	4.2 (2)
N1'—Ni—N3'—C1'	−4.3 (2)	N3'—Ni—N4—C9	32.6 (5)
N4—Ni—N3'—C1'	−32.9 (5)	N2—Ni—N4—C9	−173.8 (2)
N2—Ni—N3'—C1'	174.1 (2)	C9—N4—C5—C6	5.5 (4)
Ni—N3'—C1'—N2'	1.5 (4)	Ni—N4—C5—C6	−176.1 (2)
Ni—N3'—C1'—S2	−178.9 (2)	C9—N4—C5—C3	−173.0 (3)
N1'—N2'—C1'—N3'	3.5 (4)	Ni—N4—C5—C3	5.3 (4)
N1'—N2'—C1'—S2	−176.1 (2)	N1—C3—C5—N4	−11.3 (5)
C2'—S2—C1'—N3'	12.9 (3)	C4—C3—C5—N4	168.7 (3)
C2'—S2—C1'—N2'	−167.5 (3)	N1—C3—C5—C6	170.1 (3)
N2'—N1'—C3'—C9	−179.9 (2)	C4—C3—C5—C6	−9.8 (5)
Ni—N1'—C3'—C9	3.2 (3)	N4—C5—C6—C7	−2.7 (5)
N2'—N1'—C3'—C4'	−2.6 (5)	C3—C5—C6—C7	175.9 (3)
Ni—N1'—C3'—C4'	−179.5 (2)	C5—C6—C7—C8	−1.3 (5)
C3—N1—N2—C1	−163.4 (3)	C6—C7—C8—C9	2.3 (5)
C3—N1—N2—Ni	21.4 (4)	C5—N4—C9—C8	−4.6 (4)
N1'—Ni—N2—C1	130 (2)	Ni—N4—C9—C8	176.9 (2)
N4—Ni—N2—C1	164.7 (3)	C5—N4—C9—C3'	174.9 (3)
N3'—Ni—N2—C1	−23.0 (3)	Ni—N4—C9—C3'	−3.7 (3)
N1'—Ni—N2—N1	−56 (2)	C7—C8—C9—N4	0.6 (5)
N4—Ni—N2—N1	−21.0 (3)	C7—C8—C9—C3'	−178.8 (3)
N3'—Ni—N2—N1	151.3 (2)	N1'—C3'—C9—N4	0.5 (4)
N1—N2—C1—N3	167.5 (3)	C4'—C3'—C9—N4	−176.9 (3)
Ni—N2—C1—N3	−17.4 (4)	N1'—C3'—C9—C8	179.9 (3)
N1—N2—C1—S1	−9.4 (3)	C4'—C3'—C9—C8	2.6 (5)
Ni—N2—C1—S1	165.7 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H11···I	0.84 (6)	2.97 (5)	3.635 (4)	138 (4)
N3—H12···I^i	0.86 (4)	2.83 (5)	3.583 (4)	147 (4)

Symmetry code: (i) −x, −y, −z.