Adducts of nickel(II) acetylacetonate chelating with heterocyclic bases: 3-­cyanopyridine and 4-cyanopyridine

In both title compounds, (acetyl­acetonato-O,O')­bis(3-cyano­pyridine-N)­nickel(II), (I), and (acetyl­acetonato-O,O')­bis(4-cyanopyridine-N)­nickel(II), (II), both [Ni(C₅­H₇O₂)₂(C₆H₄N₂)₂], the Ni^II atom, which is situated on a centre of symmetry, is octahedrally coordinated. Distances and angles for (I) and (II), respectively, are: Ni-O 2.009 (2)/2.016 (2) and 2.0110 (16)/2.0238 (18) Å, Ni-N 2.116 (3) and 2.179 (2) Å, O-Ni-O 91.86 (10) and 90.19 (7)°, and O-Ni-N 91.27 (11)/90.19 (11) and 89.65 (8)/90.79 (7)°.

S1. Comment

Adducts of Ni^II acetylacetonate (AcAc) chelate with heterocyclic bases were synthesized with the aim of establishing correlations between the bond energies and other thermochemical parameters (Dunstan, 1998). Among these compounds, of general formula [Ni(AcAc)₂·2L], were those with L = 3-cyanopyridine, (I), and 4-cyanopyridine, (II). Based on the Δ_rH^θ (standard enthalpy of the acid/base reaction) values of these adducts, Dunstan (1998) ascertained that the basicity order was 4-cyanopyridine > 3-cyanopyridine, instead of the reverse, expected, order. It was then postulated that this could be due to the contribution of another kind of interaction such as hydrogen bonding between the N atom of the cyano group and C atoms of the AcAc moiety. In order to study this possibility, crystal structure determinations were undertaken. \sch

In both compounds, the AcAc moiety is planar, to within experimental accuracy, the r.m.s. deviation of the seven atoms being 0.012 and 0.016 Å for (I) and (II), respectively. The Ni^II atom does not lie in the plane of the AcAc residue but 0.247 (4) and 0.139 (3) Å from it, for (I) and (II), respectively. The Ni^II atom is sited on a centre of symmetry and is octahedrally bonded to two equatorial AcAc groups and two 3-cyanopyridine [(I)] and two 4-cyanopyridine [(II)] groups, which are axially coordinated in a trans configuration. The Ni—O_AcAc distances in (II) of 2.0110 (16) and 2.0238 (18) Å give rise to tetragonal distortion; this is less important in (I), for which the Ni—O_AcAc distances are 2.009 (2) and 2.016 (2) Å.

In the solid state no short intramolecular distances were found. The shortest intermolecular distances found for the N atom of the cyano group and C atoms of the AcAc moiety are N2···H1Aⁱ = 2.90 and N2···C1ⁱ = 3.832 (6) Å, and N2···H1Aⁱ—C1ⁱ = 164° for (I), and N2···H5Cⁱⁱ = 2.65 and N2···C5ⁱⁱ = 3.533 (4) Å, and N2···H5Cⁱⁱ—C5ⁱⁱ = 153° for (II). Moreover, there is an additional interaction in (I) involving a phenyl H-atom, with N2···H9ⁱⁱⁱ = 2.79 and N2···C9ⁱⁱⁱ = 3.503 (6) Å, and N2···C9ⁱⁱⁱ—H9ⁱⁱⁱ = 134° [symmetry codes: (i) 3/2 − x, −1/2 + y, 1 − z; (ii) 1 − x, −1 − y, 1 − z; (iii) −1/2 + x, 1/2 − y, −1 + z].

Whether these interactions are true hydrogen bonds is difficult to assert because, as pointed out by Cotton et al. (1997), `the field is getting muddier and muddier as the definition of a hydrogen bond is relaxed'. In any case, in (II) the N···H distance is marginally shorter than the sum of the van der Waals radii of H and N (2.7 Å).

S2. Experimental

Crystals of both compounds were obtained by slow evaporation from ethanol at 277 K.

S3. Refinement

H atoms were located on stereochemical grounds and refined with fixed geometry, each riding on a carrier atom, with an isotropic displacement parameter amounting to 1.5 (for methyl H atoms) or 1.2 (for the other H atoms) times the value of the equivalent isotropic displacement parameter of the atom to which they were attached.

Computing details

For both compounds, data collection: CAD-4 Software (Enraf-Nonius,1989); cell refinement: CAD-4 Software; data reduction: MolEN (Fair, 1990); 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.

Figures

	Fig. 1. The molecular structure of (I) showing the atom-labelling scheme. Displacement ellipsoids are shown at the 50% probability level.
	Fig. 2. The molecular structure of (II) showing the atom-labelling scheme. Displacement ellipsoids are shown at the 50% probability level.

(I)

Crystal data

[Ni(C5H7O2)2(C6H4N2)2]	F(000) = 484.0
Mr = 465.14	Dx = 1.398 Mg m^−3
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
a = 7.8295 (6) Å	Cell parameters from 25 reflections
b = 19.3334 (18) Å	θ = 8.9–12.9°
c = 8.1244 (10) Å	µ = 0.91 mm^−1
β = 116.019 (8)°	T = 293 K
V = 1105.16 (19) Å^3	Irregular, blue
Z = 2	0.20 × 0.18 × 0.05 mm

Data collection

Enraf-Nonius CAD4 diffractometer	1131 reflections with F^2 > 2σF^2
Radiation source: fine-focus sealed tube	Rint = 0.022
Graphite monochromator	θmax = 27.5°
ω/2θ scans	h = −10→0
Absorption correction: ψ-scan (North et al., 1968)	k = 0→25
Tmin = 0.839, Tmax = 0.956	l = −9→10
2737 measured reflections	3 standard reflections every 30 min
2529 independent reflections	intensity decay: 0.8%

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.115	H-atom parameters constrained
S = 0.95	Calculated w = 1/[σ^2(Fo^2) + (0.0418P)^2] where P = (Fo^2 + 2Fc^2)/3
2529 reflections	(Δ/σ)max < 0.001
144 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.59 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 on F² for ALL reflections. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating R-factor-obs 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
Ni	1/2	1/2	1/2	0.0437 (2)
N1	0.5981 (4)	0.39799 (16)	0.5000 (4)	0.0465 (8)
N2	0.6458 (7)	0.2566 (2)	0.0414 (6)	0.0910 (14)
O1	0.7482 (3)	0.52655 (13)	0.7096 (3)	0.0501 (7)
O2	0.5928 (4)	0.52834 (13)	0.3144 (3)	0.0514 (7)
C1	1.0398 (5)	0.5839 (2)	0.8702 (5)	0.0673 (13)
H1A	1.0030	0.6237	0.9176	0.101*
H1B	1.1471	0.5954	0.8477	0.101*
H1C	1.0736	0.5470	0.9577	0.101*
C2	0.8758 (5)	0.56139 (19)	0.6930 (5)	0.0478 (10)
C3	0.8762 (6)	0.5805 (2)	0.5280 (6)	0.0561 (11)
H3	0.9767	0.6081	0.5360	0.067*
C4	0.7418 (6)	0.56265 (18)	0.3512 (6)	0.0489 (10)
C5	0.7715 (7)	0.5869 (2)	0.1899 (6)	0.0763 (14)
H5A	0.7210	0.5533	0.0935	0.114*
H5B	0.9050	0.5928	0.2261	0.114*
H5C	0.7075	0.6303	0.1470	0.114*
C6	0.5906 (5)	0.3700 (2)	0.3473 (5)	0.0488 (10)
H6	0.5409	0.3960	0.2402	0.059*
C7	0.6537 (5)	0.3040 (2)	0.3418 (5)	0.0477 (10)
C8	0.7266 (6)	0.2645 (2)	0.4990 (6)	0.0646 (13)
H8	0.7694	0.2197	0.4981	0.078*
C9	0.7342 (6)	0.2927 (2)	0.6551 (6)	0.0698 (13)
H9	0.7822	0.2675	0.7635	0.084*
C10	0.6701 (6)	0.3590 (2)	0.6508 (5)	0.0559 (11)
H10	0.6773	0.3779	0.7590	0.067*
C11	0.6471 (6)	0.2771 (2)	0.1729 (7)	0.0618 (12)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.0470 (4)	0.0449 (4)	0.0366 (3)	−0.0093 (4)	0.0159 (3)	−0.0015 (4)
N1	0.0474 (18)	0.0511 (19)	0.0377 (17)	−0.0056 (16)	0.0156 (15)	−0.0019 (16)
N2	0.107 (3)	0.091 (3)	0.089 (3)	−0.022 (3)	0.057 (3)	−0.034 (3)
O1	0.0479 (15)	0.0553 (17)	0.0417 (15)	−0.0102 (13)	0.0147 (12)	0.0037 (11)
O2	0.0563 (16)	0.0561 (16)	0.0445 (15)	−0.0092 (14)	0.0247 (13)	−0.0022 (12)
C1	0.060 (3)	0.063 (3)	0.057 (3)	−0.018 (2)	0.006 (2)	−0.005 (2)
C2	0.046 (2)	0.039 (2)	0.053 (2)	0.0002 (19)	0.017 (2)	0.0005 (19)
C3	0.050 (2)	0.056 (3)	0.064 (3)	−0.017 (2)	0.026 (2)	0.001 (2)
C4	0.058 (3)	0.035 (2)	0.062 (3)	0.004 (2)	0.034 (2)	0.0051 (19)
C5	0.092 (4)	0.082 (3)	0.072 (3)	−0.017 (3)	0.052 (3)	0.007 (3)
C6	0.053 (2)	0.046 (2)	0.042 (2)	−0.004 (2)	0.0164 (19)	0.0031 (19)
C7	0.043 (2)	0.049 (3)	0.051 (2)	−0.0112 (19)	0.0206 (19)	−0.008 (2)
C8	0.063 (3)	0.051 (3)	0.074 (3)	0.001 (2)	0.025 (2)	0.006 (3)
C9	0.075 (3)	0.065 (3)	0.057 (3)	0.007 (3)	0.018 (2)	0.015 (2)
C10	0.057 (3)	0.065 (3)	0.037 (2)	−0.006 (2)	0.0123 (19)	0.001 (2)
C11	0.063 (3)	0.051 (3)	0.076 (3)	−0.013 (2)	0.035 (3)	−0.009 (2)

Geometric parameters (Å, º)

Ni—O1	2.009 (2)	C2—C3	1.392 (5)
Ni—O2	2.016 (2)	C3—C4	1.401 (5)
Ni—N1	2.116 (3)	C4—C5	1.503 (5)
N1—C6	1.331 (4)	C6—C7	1.376 (5)
N1—C10	1.335 (5)	C7—C8	1.379 (5)
N2—C11	1.135 (5)	C7—C11	1.447 (6)
O1—C2	1.260 (4)	C8—C9	1.358 (6)
O2—C4	1.258 (4)	C9—C10	1.371 (6)
C1—C2	1.513 (5)
O1^i—Ni—O2^i	91.86 (10)	C3—C2—C1	118.7 (4)
O1—Ni—O2^i	88.14 (10)	C2—C3—C4	127.2 (4)
O1—Ni—O2	91.86 (10)	O2—C4—C3	125.1 (4)
O1^i—Ni—N1	88.73 (11)	O2—C4—C5	116.1 (4)
O1—Ni—N1	91.27 (11)	C3—C4—C5	118.9 (4)
O2^i—Ni—N1	89.81 (11)	N1—C6—C7	122.5 (3)
O2—Ni—N1	90.19 (11)	C6—C7—C8	119.5 (4)
C6—N1—C10	117.0 (3)	C6—C7—C11	119.9 (4)
C6—N1—Ni	120.8 (2)	C8—C7—C11	120.5 (4)
C10—N1—Ni	122.2 (3)	C9—C8—C7	118.2 (4)
C2—O1—Ni	124.3 (2)	C8—C9—C10	119.1 (4)
C4—O2—Ni	124.5 (3)	N1—C10—C9	123.6 (4)
O1—C2—C3	125.6 (4)	N2—C11—C7	178.5 (5)
O1—C2—C1	115.7 (3)

Symmetry code: (i) −x+1, −y+1, −z+1.

(II)

Crystal data

[Ni(C5H7O2)2(C6H4N2)2]	Z = 1
Mr = 465.14	F(000) = 242
Triclinic, P1	Dx = 1.379 Mg m^−3
a = 6.2795 (6) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.912 (1) Å	Cell parameters from 25 reflections
c = 10.392 (1) Å	θ = 8.2–13.9°
α = 64.96 (1)°	µ = 0.90 mm^−1
β = 86.441 (8)°	T = 293 K
γ = 73.333 (9)°	Irregular, blue
V = 560.10 (9) Å^3	0.22 × 0.18 × 0.05 mm

Data collection

Enraf-Nonius CAD4 diffractometer	1605 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.022
Graphite monochromator	θmax = 25.5°
ω/2θ scans	h = −7→7
Absorption correction: ψ-scan (North et al., 1968)	k = −11→10
Tmin = 0.855, Tmax = 0.961	l = −12→0
2180 measured reflections	3 standard reflections every 60 min
2059 independent reflections	intensity decay: 1.1%

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.084	H-atom parameters constrained
S = 1.06	Calculated w = 1/[σ^2(Fo^2) + (0.029P)^2 + 0.1589P] where P = (Fo^2 + 2Fc^2)/3
2059 reflections	(Δ/σ)max < 0.001
144 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.26 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 on F² for ALL reflections. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating R-factor-obs 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
Ni	0	0	0	0.03738 (18)
O1	0.1401 (3)	0.1561 (2)	0.00617 (18)	0.0430 (4)
O2	−0.1764 (3)	0.0057 (2)	0.16829 (19)	0.0459 (5)
N1	0.2667 (3)	−0.1908 (2)	0.1456 (2)	0.0411 (5)
N2	0.9547 (5)	−0.6553 (3)	0.4737 (4)	0.0932 (11)
C1	0.1161 (4)	0.2085 (3)	0.0995 (3)	0.0441 (7)
C2	0.2506 (5)	0.3191 (4)	0.0818 (4)	0.0646 (9)
H2A	0.4059	0.2680	0.0826	0.097*
H2B	0.2271	0.3501	0.1587	0.097*
H2C	0.2041	0.4092	−0.0070	0.097*
C3	−0.0168 (5)	0.1715 (3)	0.2133 (3)	0.0555 (8)
H3	−0.0146	0.2150	0.2767	0.067*
C4	−0.1543 (5)	0.0746 (3)	0.2417 (3)	0.0463 (7)
C5	−0.2871 (6)	0.0467 (4)	0.3723 (3)	0.0663 (9)
H5A	−0.4397	0.0633	0.3464	0.099*
H5B	−0.2793	0.1173	0.4115	0.099*
H5C	−0.2265	−0.0584	0.4419	0.099*
C6	0.4438 (4)	−0.1654 (3)	0.1852 (3)	0.0465 (7)
H6	0.4489	−0.0633	0.1511	0.056*
C7	0.6197 (4)	−0.2818 (3)	0.2739 (3)	0.0494 (7)
H7	0.7386	−0.2584	0.3002	0.059*
C8	0.6158 (5)	−0.4325 (3)	0.3224 (3)	0.0474 (7)
C9	0.4319 (5)	−0.4613 (3)	0.2838 (3)	0.0626 (9)
H9	0.4229	−0.5624	0.3164	0.075*
C10	0.2639 (5)	−0.3380 (3)	0.1966 (3)	0.0563 (8)
H10	0.1407	−0.3582	0.1716	0.068*
C11	0.8035 (6)	−0.5584 (4)	0.4092 (3)	0.0601 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.0367 (3)	0.0398 (3)	0.0407 (3)	−0.0128 (2)	−0.0009 (2)	−0.0201 (2)
O1	0.0433 (10)	0.0460 (11)	0.0477 (11)	−0.0173 (8)	−0.0002 (8)	−0.0242 (9)
O2	0.0457 (11)	0.0507 (11)	0.0476 (11)	−0.0169 (9)	0.0045 (9)	−0.0250 (9)
N1	0.0386 (12)	0.0421 (13)	0.0433 (13)	−0.0117 (10)	−0.0031 (10)	−0.0178 (11)
N2	0.097 (2)	0.0628 (19)	0.106 (3)	0.0196 (18)	−0.052 (2)	−0.0420 (19)
C1	0.0419 (15)	0.0352 (14)	0.0539 (17)	−0.0043 (12)	−0.0161 (13)	−0.0195 (13)
C2	0.064 (2)	0.061 (2)	0.085 (2)	−0.0227 (16)	−0.0069 (17)	−0.0404 (18)
C3	0.0666 (19)	0.0584 (18)	0.0560 (18)	−0.0187 (15)	0.0026 (16)	−0.0369 (16)
C4	0.0469 (16)	0.0430 (15)	0.0427 (15)	−0.0020 (13)	−0.0038 (13)	−0.0183 (13)
C5	0.077 (2)	0.066 (2)	0.0536 (19)	−0.0144 (17)	0.0125 (16)	−0.0291 (17)
C6	0.0415 (15)	0.0413 (15)	0.0539 (17)	−0.0140 (12)	−0.0044 (13)	−0.0152 (13)
C7	0.0403 (15)	0.0492 (17)	0.0573 (18)	−0.0135 (13)	−0.0067 (13)	−0.0194 (14)
C8	0.0487 (16)	0.0454 (16)	0.0455 (16)	−0.0062 (13)	−0.0084 (13)	−0.0201 (14)
C9	0.072 (2)	0.0394 (16)	0.072 (2)	−0.0161 (15)	−0.0243 (17)	−0.0160 (15)
C10	0.0543 (18)	0.0466 (17)	0.066 (2)	−0.0170 (14)	−0.0183 (15)	−0.0175 (15)
C11	0.069 (2)	0.0484 (18)	0.062 (2)	−0.0048 (16)	−0.0188 (17)	−0.0271 (16)

Geometric parameters (Å, º)

Ni—O1	2.0110 (16)	C1—C2	1.512 (4)
Ni—O2	2.0238 (18)	C3—C4	1.400 (4)
Ni—N1	2.179 (2)	C4—C5	1.513 (4)
O1—C1	1.264 (3)	C6—C7	1.377 (4)
O2—C4	1.255 (3)	C7—C8	1.367 (4)
N1—C10	1.330 (3)	C8—C9	1.386 (4)
N1—C6	1.332 (3)	C8—C11	1.447 (4)
N2—C11	1.133 (4)	C9—C10	1.367 (4)
C1—C3	1.384 (4)
O1—Ni—O2^i	89.81 (7)	C3—C1—C2	119.4 (3)
O1—Ni—O2	90.19 (7)	C1—C3—C4	126.0 (3)
O1—Ni—N1^i	89.21 (7)	O2—C4—C3	125.5 (3)
O2—Ni—N1^i	90.35 (8)	O2—C4—C5	116.0 (3)
O1—Ni—N1	90.79 (7)	C3—C4—C5	118.5 (3)
O2—Ni—N1	89.65 (8)	N1—C6—C7	123.7 (3)
C1—O1—Ni	126.17 (18)	C8—C7—C6	118.6 (3)
C4—O2—Ni	125.94 (18)	C7—C8—C9	118.6 (3)
C10—N1—C6	116.7 (2)	C7—C8—C11	120.1 (3)
C10—N1—Ni	121.98 (17)	C9—C8—C11	121.3 (3)
C6—N1—Ni	121.26 (18)	C10—C9—C8	118.7 (3)
O1—C1—C3	125.7 (2)	N1—C10—C9	123.7 (3)
O1—C1—C2	114.9 (3)	N2—C11—C8	177.7 (4)

Symmetry code: (i) −x, −y, −z.