Bis­[3-(o-methoxy­phenyl)-1-methyl­triazene 1-oxidato-O,N³,O']­zinc(II)

In the title compound, [Zn(C₈H₁₀N₃O₂)₂], the Zn atom displays a highly distorted octahedral coordination involving O and N atoms of two bidentate planar ligands approximately orthogonal to each other; the dihedral angle between the ligand planes is 84.95 (4)°. The ligand mol­ecules show great asymmetry in their bonding to the Zn²⁺ ion, with Zn-O bond distances ranging between 2.056 (2) and 2.534 (2) Å. The planar phenyl ring and the trigonal-planar geometry about the triazene N atom bonded to the phenyl ring suggest a resonance interaction extending over adjacent atoms.

S1. Comment

Substituted triazenes/triazene 1-oxides are potentially bidentate ligands forming both bis- and tris-chelate complexes with various metal ions (Rodriguez et al., 1999). The molecular conformations of bis-chelate complexes are extremely sensitive to the nature of substituents in the 1- and 3-N positions of the triazene moiety. The crystal structures of [Co(ept)₂] (ept is 1-ethyl-3-phenyltriazene 1-oxide; Rudolf et al., 1988) and [Ni(enpt)₂] (enpt is 1-ethyl-3-p-nitrophenyltriazene 1-oxide; Ciunik et al., 1991) reveal square-planar metal coordination geometry, with the two ligands in a trans configuration. The complexes M(cpmt)₂ [M = Cd or Zn; cpmt is 3-(o-carboxyphenyl)-1-methyltriazene 1-oxide] are, however, reported to be polymeric on the basis of spectroscopic data (Constable, 1984). As part of systematic studies on the synthesis and characterization of triazene 1-oxide derivatives and their metal complexes (Samanta et al., 1998) and to build up a hierarchy for such systems, the structure determination of the title complex, (I), was undertaken.

The crystal structure of (I) consists of discrete neutral [ZnL₂] molecules [Fig.1; L is 3-(o-methoxyphenyl)-1-methyltriazene 1-oxide]. The two bidentate triazene 1-oxide ligands are bonded to the Zn²⁺ ion through their N and O atoms. The Zn—N distances [1.974 (2) and 1.978 (2) Å] are comparable with corresponding values reported in the literature (Tatar et al., 1999). The coordination of the Zn²⁺ ion by the two phenolate O atoms of the ligands is substantially weakened. This is reflected in the significant lengthening of the Zn—O(phenolate) distances [2.491 (2) and 2.534 (2) Å] compared with Zn—O (triazene-oxo) bond lengths [2.056 (2) and 2.066 (2) Å], and is evidently due to steric hindrance between the essentially planar ligands. The Zn—O distances in bidentate Zn^II complexes vary over a wide range and values as different as 1.932 (2) and 2.460 (2) Å have been reported (Kremer-Aach et al., 1997) where the ligand shows great asymmetry in its bonding to the metal.

The Zn²⁺ ion coordination in (I) is highly distorted octahedral, with the N1, N4, O3 and O4 atoms defining the equatorial plane [maximum deviation for atom N4 of 0.028 (1) Å], and the O1 and O2 atoms occupy the axial sites; the Zn atom is displaced by 0.252 (1) Å towards O2. The distortion of the metal coordination sphere from octahedral geometry is revealed in the large variation of N/O—Zn—N/O cisoid [68.92 (8)–118.62 (8)°] and transoid [145.89 (9)–155.58 (9)°] angles from their ideal values. This is consistent with the fact that the metal coordination sphere in zinc(II) complexes has been exceptionally flexible and easily adaptable to the demands of the ligands. In the absence of crystal field stabilization effects, the stereochemistry of the ligands around the metal ion is determined essentially by size and electrostatic and covalent bonding forces, and the zinc coordination polyhedra show large deviations from regular geometries (Mangani et al., 1992). A comparison of geometrical parameters of different octahedral Zn^II complexes with N,O-donor atoms is given Table 2.

The five-membered chelate rings, i.e. Zn—N1—N2—N3—O2 and Zn—N4—N5—N6—O4, are essentially planar, with the maximum deviation of an in-plane atom being 0.036 (1) Å for N1. The two planar ligand molecules, A (N1–N3, O1, O2, C1—C8) and B (N4—N6, O3, O4, C9—C16). with r.m.s. deviations of 0.066 and 0.030 Å, respectively, are approximately orthogonal to each other, the dihedral angle between A and B is 84.95 (4)°. The N1 and N4 atoms, with bond angles summing to 360.0 (2) and 359.9 (2)°, respectively, are sp² hybridized. Each displays trigonal–planar bonding geometry and coplanarity with the phenyl group, strongly suggesting a resonance interaction extending to the adjacent atoms. This is reflected in the shorter N1—C7 [1.405 (3) Å] and N4—C15 [1.400 (3) Å] bond lengths compared with N3—C8 [1.454 (3) Å] and N6—C16 [1.450 (3) Å]. The short N2—N3 and N5—N6 distances [1.282 (3) and 1.275 (3) Å] indicate double-bond character, and the N1—N2 and N4—N5 bonds [1.318 (3) and 1.314 (3) Å] are shorter than pure single bonds. Similar observations have been reported for other substituted triazene 1-oxide compounds (Samanta et al., 1998).

Discrete monomeric molecules of (I) are held together in the crystal by van der Waals interactions. The minimum distances between two non-H atoms in neighbouring molecules are C16···O2, C5···O4, C8···O4 and C16···O4 with values of 3.227 (3), 3.431 (4), 3.498 (4) and 3.514 (4) Å, respectively.

S2. Experimental

The title compound was prepared following the procedure of Kumar et al. (1983). Single crystals were obtained by slow evaporation from hexane.

S3. Refinement

All H atoms were placed in calculated positions, each riding on their carrier atoms with an isotropic displacement parameter of 1.5 (for methyl H atoms) or 1.2 (for the other H atoms) times the equivalent isotropic displacement parameter of the attached atom.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1993); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1995); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ZORTEP (Zsolnai, 1995); software used to prepare material for publication: SHELXL97 and PARST95 (Nardelli, 1995).

Figures

Fig. 1. The molecular structure of (I) with 50% probability displacement ellipsoids.

Bis[3-(o-methoxyphenyl)-1-methyltriazene 1-oxide(1-)-O,N³,O']zinc(II)

Crystal data

[Zn(C8H10N3O2)2]	Z = 2
Mr = 425.75	F(000) = 440
Triclinic, P1	Dx = 1.547 Mg m^−3
a = 10.853 (1) Å	Cu Kα radiation, λ = 1.54180 Å
b = 11.547 (1) Å	Cell parameters from 25 reflections
c = 7.821 (1) Å	θ = 34.5–39.3°
α = 96.97 (1)°	µ = 2.19 mm^−1
β = 110.03 (1)°	T = 293 K
γ = 86.84 (1)°	Block, light yellow
V = 913.9 (2) Å^3	0.30 × 0.25 × 0.15 mm

Data collection

Rigaku AFC-5R diffractometer	3194 reflections with I > 2σ(I)
Radiation source: Rigaku rotating anode	Rint = 0.036
Graphite monochromator	θmax = 78.0°, θmin = 3.9°
ω–2θ scans	h = −7→13
Absorption correction: ψ scans (North et al., 1968)	k = −14→14
Tmin = 0.605, Tmax = 0.718	l = −9→9
3819 measured reflections	3 standard reflections every 150 reflections
3622 independent reflections	intensity decay: <3%

Refinement

Refinement on F^2	Primary atom site location: heavy atom
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.122	H-atom parameters constrained
S = 0.97	w = 1/[σ^2(Fo^2) + (0.0838P)^2 + 0.3895P] where P = (Fo^2 + 2Fc^2)/3
3622 reflections	(Δ/σ)max = 0.002
248 parameters	Δρmax = 0.59 e Å^−3
0 restraints	Δρmin = −0.36 e Å^−3

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

	x	y	z	Uiso*/Ueq
Zn	0.20340 (3)	0.25261 (3)	0.15980 (5)	0.04767 (15)
O1	0.2841 (3)	0.10648 (18)	−0.0407 (3)	0.0754 (7)
O2	0.1156 (2)	0.28213 (15)	0.3578 (3)	0.0543 (4)
O3	0.4374 (2)	0.2322 (2)	0.3736 (3)	0.0696 (6)
O4	0.07967 (18)	0.33203 (16)	−0.0583 (3)	0.0524 (4)
N1	0.1630 (2)	0.09339 (17)	0.1903 (3)	0.0432 (4)
N2	0.0963 (2)	0.08336 (17)	0.3001 (3)	0.0445 (4)
N3	0.0745 (2)	0.18202 (17)	0.3802 (3)	0.0457 (5)
N4	0.3148 (2)	0.37652 (17)	0.1394 (3)	0.0436 (4)
N5	0.2587 (2)	0.44876 (17)	0.0167 (3)	0.0440 (4)
N6	0.14082 (19)	0.42209 (17)	−0.0798 (3)	0.0431 (4)
C1	0.3406 (4)	0.1245 (3)	−0.1719 (5)	0.0760 (9)
H1A	0.3484	0.2067	−0.1738	0.114*
H1B	0.2861	0.0910	−0.2904	0.114*
H1C	0.4260	0.0883	−0.1413	0.114*
C2	0.2628 (3)	−0.0055 (2)	−0.0158 (4)	0.0505 (6)
C3	0.3033 (3)	−0.1058 (3)	−0.0990 (4)	0.0602 (7)
H3	0.3496	−0.1003	−0.1782	0.072*
C4	0.2752 (3)	−0.2146 (3)	−0.0648 (4)	0.0619 (7)
H4	0.3034	−0.2820	−0.1194	0.074*
C5	0.2053 (3)	−0.2221 (2)	0.0502 (4)	0.0581 (7)
H5A	0.1850	−0.2950	0.0713	0.070*
C6	0.1649 (3)	−0.1225 (2)	0.1350 (4)	0.0491 (6)
H6	0.1171	−0.1291	0.2119	0.059*
C7	0.1949 (2)	−0.0130 (2)	0.1063 (3)	0.0418 (5)
C8	−0.0027 (3)	0.1848 (3)	0.5004 (4)	0.0610 (7)
H8A	0.0486	0.2172	0.6214	0.092*
H8B	−0.0277	0.1070	0.5042	0.092*
H8C	−0.0800	0.2322	0.4548	0.092*
C9	0.4907 (4)	0.1529 (4)	0.4986 (6)	0.0949 (13)
H9A	0.4264	0.0957	0.4861	0.142*
H9B	0.5172	0.1928	0.6203	0.142*
H9C	0.5655	0.1150	0.4763	0.142*
C10	0.5109 (3)	0.3234 (3)	0.3700 (4)	0.0520 (6)
C11	0.6397 (3)	0.3423 (3)	0.4817 (4)	0.0642 (8)
H11	0.6831	0.2895	0.5640	0.077*
C12	0.7035 (3)	0.4395 (3)	0.4707 (4)	0.0700 (9)
H12	0.7899	0.4522	0.5461	0.084*
C13	0.6402 (3)	0.5174 (3)	0.3494 (5)	0.0651 (8)
H13	0.6839	0.5830	0.3434	0.078*
C14	0.5126 (3)	0.4994 (2)	0.2363 (4)	0.0535 (6)
H14	0.4710	0.5526	0.1537	0.064*
C15	0.4453 (2)	0.4023 (2)	0.2446 (3)	0.0441 (5)
C16	0.0675 (3)	0.4941 (2)	−0.2216 (4)	0.0548 (6)
H16A	0.0374	0.4467	−0.3372	0.082*
H16B	0.1230	0.5541	−0.2281	0.082*
H16C	−0.0065	0.5291	−0.1934	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn	0.0590 (2)	0.0395 (2)	0.0518 (2)	−0.00314 (14)	0.02607 (17)	0.01023 (14)
O1	0.1168 (19)	0.0504 (11)	0.0907 (16)	−0.0077 (11)	0.0754 (15)	0.0053 (11)
O2	0.0765 (12)	0.0353 (8)	0.0626 (11)	−0.0022 (8)	0.0383 (10)	0.0046 (8)
O3	0.0610 (12)	0.0761 (14)	0.0709 (13)	−0.0011 (10)	0.0129 (10)	0.0329 (11)
O4	0.0506 (9)	0.0514 (10)	0.0557 (10)	−0.0122 (8)	0.0144 (8)	0.0140 (8)
N1	0.0556 (11)	0.0370 (9)	0.0449 (11)	−0.0003 (8)	0.0270 (9)	0.0049 (8)
N2	0.0573 (12)	0.0371 (9)	0.0469 (11)	−0.0007 (8)	0.0279 (9)	0.0034 (8)
N3	0.0599 (12)	0.0389 (10)	0.0462 (11)	0.0000 (8)	0.0285 (10)	0.0043 (8)
N4	0.0459 (10)	0.0417 (10)	0.0445 (11)	−0.0027 (8)	0.0159 (8)	0.0071 (8)
N5	0.0481 (11)	0.0385 (10)	0.0480 (11)	−0.0016 (8)	0.0182 (9)	0.0085 (8)
N6	0.0444 (10)	0.0401 (10)	0.0464 (11)	−0.0015 (8)	0.0159 (8)	0.0090 (8)
C1	0.090 (2)	0.081 (2)	0.082 (2)	0.0007 (18)	0.056 (2)	0.0216 (18)
C2	0.0600 (15)	0.0466 (13)	0.0513 (14)	−0.0022 (11)	0.0283 (12)	0.0006 (11)
C3	0.0714 (18)	0.0600 (16)	0.0585 (16)	0.0012 (13)	0.0375 (14)	−0.0030 (13)
C4	0.0766 (19)	0.0478 (14)	0.0612 (17)	0.0043 (13)	0.0288 (15)	−0.0090 (12)
C5	0.0787 (19)	0.0391 (13)	0.0584 (16)	−0.0017 (12)	0.0271 (14)	0.0007 (11)
C6	0.0633 (15)	0.0409 (12)	0.0485 (14)	−0.0045 (10)	0.0257 (12)	0.0034 (10)
C7	0.0478 (12)	0.0400 (11)	0.0387 (12)	−0.0006 (9)	0.0165 (10)	0.0025 (9)
C8	0.083 (2)	0.0532 (15)	0.0649 (18)	−0.0006 (13)	0.0493 (16)	0.0026 (13)
C9	0.088 (3)	0.110 (3)	0.102 (3)	0.014 (2)	0.036 (2)	0.061 (3)
C10	0.0494 (13)	0.0660 (16)	0.0441 (13)	0.0024 (11)	0.0212 (11)	0.0053 (12)
C11	0.0488 (15)	0.094 (2)	0.0502 (15)	0.0114 (14)	0.0183 (12)	0.0088 (15)
C12	0.0425 (14)	0.107 (3)	0.0569 (17)	−0.0090 (15)	0.0196 (13)	−0.0144 (17)
C13	0.0521 (15)	0.074 (2)	0.0706 (19)	−0.0156 (14)	0.0287 (14)	−0.0172 (16)
C14	0.0518 (14)	0.0533 (14)	0.0587 (16)	−0.0067 (11)	0.0255 (12)	−0.0039 (12)
C15	0.0422 (11)	0.0497 (13)	0.0422 (12)	−0.0013 (9)	0.0187 (10)	−0.0012 (10)
C16	0.0557 (15)	0.0510 (14)	0.0559 (15)	0.0036 (11)	0.0135 (12)	0.0168 (12)

Geometric parameters (Å, º)

Zn—N1	1.974 (2)	C3—H3	0.9300
Zn—N4	1.978 (2)	C4—C5	1.372 (4)
Zn—O4	2.056 (2)	C4—H4	0.9300
Zn—O3	2.534 (2)	C5—C6	1.384 (4)
Zn—O2	2.066 (2)	C5—H5A	0.9300
Zn—O1	2.491 (2)	C6—C7	1.385 (3)
O1—C2	1.374 (3)	C6—H6	0.9300
O1—C1	1.404 (4)	C8—H8A	0.9600
O2—N3	1.314 (3)	C8—H8B	0.9600
O3—C10	1.364 (4)	C8—H8C	0.9600
O3—C9	1.378 (4)	C9—H9A	0.9600
O4—N6	1.321 (3)	C9—H9B	0.9600
N1—N2	1.318 (3)	C9—H9C	0.9600
N1—C7	1.405 (3)	C10—C11	1.384 (4)
N2—N3	1.282 (3)	C10—C15	1.403 (4)
N3—C8	1.454 (3)	C11—C12	1.376 (5)
N4—N5	1.314 (3)	C11—H11	0.9300
N4—C15	1.400 (3)	C12—C13	1.369 (5)
N5—N6	1.275 (3)	C12—H12	0.9300
N6—C16	1.450 (3)	C13—C14	1.375 (4)
C1—H1A	0.9600	C13—H13	0.9300
C1—H1B	0.9600	C14—C15	1.391 (4)
C1—H1C	0.9600	C14—H14	0.9300
C2—C3	1.384 (4)	C16—H16A	0.9600
C2—C7	1.405 (3)	C16—H16B	0.9600
C3—C4	1.386 (4)	C16—H16C	0.9600
N1—Zn—N4	155.58 (9)	C5—C4—H4	120.2
N1—Zn—O4	118.62 (8)	C3—C4—H4	120.2
N4—Zn—O4	77.75 (7)	C4—C5—C6	120.8 (3)
N1—Zn—O2	77.33 (7)	C4—C5—H5A	119.6
N4—Zn—O2	118.02 (8)	C6—C5—H5A	119.6
O4—Zn—O2	104.56 (8)	C7—C6—C5	120.5 (2)
N1—Zn—O1	69.91 (7)	C7—C6—H6	119.7
N4—Zn—O1	92.46 (8)	C5—C6—H6	119.7
O4—Zn—O1	92.96 (8)	C6—C7—N1	125.3 (2)
O2—Zn—O1	147.19 (7)	C6—C7—C2	118.5 (2)
O3—Zn—N4	68.92 (8)	N1—C7—C2	116.2 (2)
O3—Zn—N1	91.25 (8)	N3—C8—H8A	109.5
O3—Zn—O4	145.89 (9)	N3—C8—H8B	109.5
O1—Zn—O3	81.70 (8)	H8A—C8—H8B	109.5
O2—Zn—O3	97.44 (8)	N3—C8—H8C	109.5
C2—O1—C1	119.3 (2)	H8A—C8—H8C	109.5
C2—O1—Zn	111.35 (15)	H8B—C8—H8C	109.5
C1—O1—Zn	129.3 (2)	O3—C9—H9A	109.5
N3—O2—Zn	108.45 (13)	O3—C9—H9B	109.5
C10—O3—C9	119.5 (3)	H9A—C9—H9B	109.5
N6—O4—Zn	108.24 (13)	O3—C9—H9C	109.5
N2—N1—C7	114.64 (19)	H9A—C9—H9C	109.5
N2—N1—Zn	117.3 (2)	H9B—C9—H9C	109.5
C7—N1—Zn	128.01 (16)	O3—C10—C11	124.7 (3)
N3—N2—N1	112.55 (19)	O3—C10—C15	115.0 (2)
N2—N3—O2	123.98 (19)	C11—C10—C15	120.3 (3)
N2—N3—C8	118.6 (2)	C12—C11—C10	120.0 (3)
O2—N3—C8	117.37 (19)	C12—C11—H11	120.0
N5—N4—C15	114.4 (2)	C10—C11—H11	120.0
N5—N4—Zn	116.6 (2)	C11—C12—C13	120.3 (3)
C15—N4—Zn	128.88 (16)	C11—C12—H12	119.9
N6—N5—N4	113.22 (19)	C13—C12—H12	119.9
N5—N6—O4	123.93 (19)	C14—C13—C12	120.6 (3)
N5—N6—C16	119.0 (2)	C14—C13—H13	119.7
O4—N6—C16	117.0 (2)	C12—C13—H13	119.7
O1—C1—H1A	109.5	C13—C14—C15	120.5 (3)
O1—C1—H1B	109.5	C13—C14—H14	119.7
H1A—C1—H1B	109.5	C15—C14—H14	119.7
O1—C1—H1C	109.5	C14—C15—N4	125.5 (2)
H1A—C1—H1C	109.5	C14—C15—C10	118.4 (2)
H1B—C1—H1C	109.5	N4—C15—C10	116.1 (2)
O1—C2—C3	125.3 (2)	N6—C16—H16A	109.5
O1—C2—C7	114.4 (2)	N6—C16—H16B	109.5
C3—C2—C7	120.3 (2)	H16A—C16—H16B	109.5
C2—C3—C4	120.2 (3)	N6—C16—H16C	109.5
C2—C3—H3	119.9	H16A—C16—H16C	109.5
C4—C3—H3	119.9	H16B—C16—H16C	109.5
C5—C4—C3	119.6 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5A···O4^i	0.93	2.89	3.431 (4)	118
C8—H8A···O4^ii	0.96	2.61	3.498 (4)	154
C16—H16C···O2^iii	0.96	2.68	3.227 (3)	117
C16—H16C···O4^iii	0.96	2.69	3.514 (4)	144

Symmetry codes: (i) −x, −y, −z; (ii) x, y, z+1; (iii) −x, −y+1, −z.