Bis[μ-N,N′-bis­(3-methyl­salicyl­idene)propane-1,3-diaminato]dicobalt(II) 0.28-hydrate

The title complex, bis­{μ-6,6-dimeth­yl-2,2′-[propane-1,3-diyl­bis(nitrilo­methyl­idyne)]diphenolato}dicobalt(II) 0.28-hydrate, [Co₂(C₁₉H₂₀N₂O₂)₂]·0.28H₂O, is a dinuclear cobalt(II) complex, which crystallizes in the tetra­gonal space group P4₁2₁2. The complex mol­ecule is located on a twofold symmetry axis. Each Co^II ion is five-coordinated by two O and two N atoms from a Schiff base ligand, and by another bridging phenolate O atom from another Schiff base ligand, giving a severely distorted trigonal–bipyramidal coordination environment.

S1. Comment

Investigation into the magnetic properties of molecule-based materials containing a polymetallic assembly has become a fascinating subject in the field of condensed matter physics and materials chemistry (Dalai et al., 2002; Bhaduri et al., 2003). Much attention has been focused on coordination complexes with novel magnetic properties, which may have potentially useful applications in materials science (Ray et al., 2003). The prime strategy for designing these molecular materials is to use a suitable bridging ligand that determines the nature of the magnetic interactions (Koner et al., 2003).

Our work is aimed at obtaining polymetallic complexes. Based on the above considerations, we have designed and synthesized a flexible tetradentate bridging ligand, N,N'-bis(3-methylsalicylidene)-1,3-propanediamine (BMPD). The reason we do not use a rigid ligand is that the flexible BMPD ligand can adopt different coordination modes according to the geometric need of the transition metal ions and the coordination environment (You et al., 2004a). The phenolate O atoms, acting as the bridging ligands, can easily bridge different metal ions, forming polynuclear complexes (You & Zhu, 2004). To the best of our knowledge, Schiff base complexes synthesized under solvothermal conditions have rarely been reported (You et al., 2004b). Furthermore, very few Schiff bases have so far been derived from 3-methylsalicylaldehyde. Here, we report the title novel dinuclear cobalt(II) complex, (I), formed by the reaction of the BMPD ligand with cobalt(II) acetate under solvothermal conditions.

Complex (I) is a phenolate-O-bridged dinuclear cobalt(II) compound (Fig. 1), which crystallizes in the tetragonal space group P4₁2₁2. The complex molecule is located on a twofold symmetry axis. The structure contains a disordered lattice water molecule, with an occupancy of 0.28. Each cobalt(II) ion in the complex is five-coordinated, by two imine N and two phenolate O atoms from a Schiff base ligand, and another bridging phenolate O atom from another Schiff base ligand. The Co···Co separation is 3.124 (2) Å. The bond lengths related to the metal ion are comparable with the corresponding values observed in another Schiff base cobalt(II) complex (You et al., 2004c). It is obvious that the Co1—O2 distance [2.100 (2) Å; Table 1] is longer than the Co1—O1 distance [1.932 (2) Å], which is due to the coordination of atom O2 to both Co1 and Co1ⁱ ions [symmetry code: (i) 1 − y, 1 − x, 1/2 − z]. The coordination of atom O2 simultaneously to two metal ions weakens the Co—O bond. The bond lengths of C8═N1 [1.285 (3) Å] and C12═N2 [1.282 (3) Å] conform to the value for a double bond, while the bond lengths of C9—N1 [1.475 (3) Å] and C11—N2 [1.473 (3) Å] conform to the value for a single bond.

The question arises as to whether the coordination polyhedron around each cobalt(II) ion can be described as a distorted square pyramid or a distorted trigonal bipyramid. Further information can be obtained by determining the structural index τ which represents the relative amount of trigonality (square pyramid, τ = 0; trigonal bipyramid, τ = 1; Reference?). τ = (β - α)/60°, α and β being the two largest angles around the central atom. The value of τ for each Co^II ion in (I) is 0.629, indicating the coordination geometry of each Co^II ion is a severely distorted trigonal bipyramid. Atoms O1, N2 and O2ⁱ act as the basal plane of the trigonal bipyramid, while the apical positions are occupied by atoms N1 and O2. Atom O2ⁱ acts as a basal donor for the Co1 moiety and as an axial donor atom for the Co1ⁱ moiety. The deviation of atom Co1 from the least-squares plane defined by atoms N2, O1 and O2ⁱ towards N1 is 0.202 (2) Å.

The O2—Co1—O2ⁱ bond angle [79.91 (7) °] is much smaller than the N1—Co1—O2ⁱ angle [106.27 (7) °], which is due to the strain created by the four-membered bridging ring Co1/O2/Co1ⁱ/O2ⁱ. This ring is not planar but is slightly roof-shaped. The chelate ring formed by atoms Co1/N1/C9–C11/N2 has a chair conformation. The diagonally positioned atoms Co1 and C10 are displaced from the least-squares plane defined by atoms N1/N2/C9/C11 by −0.724 (2) and 0.702 (5) Å, respectively. The dihedral angle [61.2 (2)°] between the two phenyl rings, C1–C6 and C13–C18, is bigger than the corresponding value of 52.7 (3)° observed in another Schiff base cobalt(II) complex, [N,N'-bis(2-hydroxynaphthylmethylene)-1,3-propanediaminato]cobalt(II) (You et al., 2004d), which is probably due to the coordination of O2 to Co1ⁱ and O2ⁱ to Co1.

S2. Experimental

3-Methylsalicylaldehyde (0.2 mmol, 26.8 mg) and 1,3-propanediamine (0.1 mmol, 7.4 mg) were dissolved in MeOH (5 ml). The mixture was stirred at room temperature for 10 min to give a yellow mixture, to which was added an MeOH solution (3 ml) of Co(CH₃COO)₂·4H₂O (0.1 mmol, 25.1 mg). The mixture was stirred for another 10 min at room temperature and then transferred to a stainless steel bomb, which was sealed, heated at 423 K for 12 h, and cooled gradually to room temperature. Brown block-shaped crystals of (I) were formed.

S3. Refinement

All H atoms were placed in geometrically idealized positions and allowed to ride on their parent atoms, with C—H distances in the range 0.93–0.97 Å and with U_iso(H) = 1.2 or 1.5U_eq(C). The structure contains a disordered lattice water molecule, with an occupancy of 0.28. There are 1606 Friedel pairs.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. The structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Atoms labelled with the suffix (i) or unlabelled are at the symmetry position (1 − y, 1 − x, 1/2 − z). All H atoms have been omitted for clarity.

bis{µ-6,6-dimethyl-2,2'-[propane-1,3- diylbis(nitrilomethylidyne)]diphenolato}dicopper(II) 0.28-hydrate

Crystal data

[Co2(C19H20N2O2)2]·0.28H2O	Dx = 1.393 Mg m^−3
Mr = 739.08	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P41212	Cell parameters from 9201 reflections
Hall symbol: P 4abw 2nw	θ = 2.3–24.6°
a = 10.381 (2) Å	µ = 0.99 mm^−1
c = 32.513 (1) Å	T = 298 K
V = 3503.8 (10) Å^3	Block, brown
Z = 4	0.30 × 0.18 × 0.18 mm
F(000) = 1528

Data collection

Bruker SMART CCD area-detector diffractometer	4024 independent reflections
Radiation source: fine-focus sealed tube	3729 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
ω scans	θmax = 27.5°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −13→13
Tmin = 0.755, Tmax = 0.842	k = −13→13
30177 measured reflections	l = −42→42

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.033	H-atom parameters constrained
wR(F^2) = 0.078	w = 1/[σ^2(Fo^2) + (0.0334P)^2 + 0.8675P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max < 0.001
4024 reflections	Δρmax = 0.39 e Å^−3
221 parameters	Δρmin = −0.17 e Å^−3
0 restraints	Absolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.006 (16)

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	Occ. (<1)
Co1	0.70834 (3)	0.34696 (3)	0.296383 (9)	0.03352 (9)
O1	0.55675 (15)	0.42483 (17)	0.32007 (5)	0.0415 (4)
O2	0.58235 (15)	0.24241 (15)	0.25843 (5)	0.0353 (3)
O3	0.4513 (8)	0.5487 (8)	0.2500	0.065 (3)*	0.28
N1	0.82442 (18)	0.43612 (19)	0.33845 (6)	0.0390 (5)
N2	0.80477 (19)	0.17313 (19)	0.30260 (6)	0.0417 (5)
C1	0.6534 (2)	0.5596 (2)	0.37131 (7)	0.0381 (5)
C2	0.5477 (2)	0.5145 (2)	0.34769 (7)	0.0363 (5)
C3	0.4244 (2)	0.5685 (2)	0.35563 (8)	0.0436 (6)
C4	0.4118 (3)	0.6636 (3)	0.38491 (8)	0.0489 (6)
H4	0.3310	0.6997	0.3894	0.059*
C5	0.5150 (3)	0.7074 (3)	0.40791 (8)	0.0521 (7)
H5	0.5035	0.7716	0.4275	0.063*
C6	0.6333 (3)	0.6553 (3)	0.40145 (8)	0.0474 (6)
H6	0.7026	0.6834	0.4172	0.057*
C7	0.3111 (3)	0.5195 (3)	0.33206 (11)	0.0680 (9)
H7A	0.2341	0.5605	0.3419	0.102*
H7B	0.3040	0.4280	0.3357	0.102*
H7C	0.3223	0.5384	0.3034	0.102*
C8	0.7828 (2)	0.5139 (2)	0.36620 (7)	0.0410 (5)
H8	0.8432	0.5438	0.3850	0.049*
C9	0.9625 (2)	0.4030 (3)	0.33980 (9)	0.0485 (6)
H9A	1.0037	0.4505	0.3619	0.058*
H9B	1.0029	0.4281	0.3141	0.058*
C10	0.9822 (3)	0.2595 (3)	0.34664 (9)	0.0539 (7)
H10A	1.0724	0.2446	0.3528	0.065*
H10B	0.9328	0.2338	0.3706	0.065*
C11	0.9442 (2)	0.1742 (3)	0.31099 (9)	0.0504 (7)
H11A	0.9891	0.2031	0.2865	0.060*
H11B	0.9721	0.0868	0.3167	0.060*
C12	0.7511 (2)	0.0623 (2)	0.29947 (8)	0.0439 (6)
H12	0.8026	−0.0089	0.3050	0.053*
C13	0.6176 (2)	0.0363 (2)	0.28812 (7)	0.0401 (5)
C14	0.5378 (2)	0.1283 (2)	0.26886 (6)	0.0345 (5)
C15	0.4083 (2)	0.0958 (2)	0.26044 (7)	0.0412 (5)
C16	0.3666 (3)	−0.0279 (3)	0.26833 (8)	0.0524 (7)
H16	0.2816	−0.0494	0.2625	0.063*
C17	0.4468 (3)	−0.1206 (3)	0.28462 (9)	0.0566 (7)
H17	0.4170	−0.2042	0.2885	0.068*
C18	0.5702 (3)	−0.0893 (2)	0.29509 (8)	0.0493 (6)
H18	0.6235	−0.1511	0.3069	0.059*
C19	0.3209 (3)	0.1983 (3)	0.24393 (9)	0.0557 (7)
H19A	0.3448	0.2181	0.2161	0.084*
H19B	0.3283	0.2743	0.2606	0.084*
H19C	0.2335	0.1681	0.2445	0.084*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.03125 (16)	0.03596 (17)	0.03334 (14)	0.00331 (12)	−0.00202 (13)	−0.00019 (13)
O1	0.0314 (8)	0.0487 (10)	0.0444 (9)	−0.0005 (7)	0.0004 (7)	−0.0096 (8)
O2	0.0369 (8)	0.0339 (8)	0.0352 (8)	−0.0024 (6)	−0.0038 (7)	0.0012 (6)
N1	0.0321 (10)	0.0441 (11)	0.0408 (10)	−0.0030 (8)	−0.0040 (8)	0.0006 (9)
N2	0.0368 (10)	0.0438 (12)	0.0444 (11)	0.0083 (8)	−0.0042 (8)	0.0017 (9)
C1	0.0406 (12)	0.0391 (12)	0.0346 (11)	−0.0025 (11)	0.0004 (10)	0.0014 (9)
C2	0.0374 (13)	0.0348 (12)	0.0367 (11)	−0.0028 (9)	0.0027 (10)	0.0035 (10)
C3	0.0381 (13)	0.0411 (13)	0.0517 (14)	0.0005 (11)	0.0045 (11)	0.0035 (11)
C4	0.0489 (15)	0.0439 (14)	0.0538 (14)	0.0070 (12)	0.0131 (12)	0.0049 (12)
C5	0.0664 (18)	0.0429 (14)	0.0470 (14)	−0.0005 (13)	0.0100 (13)	−0.0084 (12)
C6	0.0532 (15)	0.0460 (14)	0.0431 (13)	−0.0050 (12)	−0.0022 (11)	−0.0054 (11)
C7	0.0398 (16)	0.064 (2)	0.100 (2)	0.0061 (14)	−0.0053 (16)	−0.0162 (18)
C8	0.0397 (13)	0.0461 (14)	0.0371 (12)	−0.0067 (11)	−0.0069 (10)	0.0006 (10)
C9	0.0314 (13)	0.0569 (16)	0.0573 (15)	0.0007 (11)	−0.0083 (12)	−0.0012 (13)
C10	0.0344 (13)	0.0664 (19)	0.0609 (17)	0.0057 (12)	−0.0133 (12)	0.0072 (14)
C11	0.0374 (13)	0.0542 (16)	0.0595 (15)	0.0104 (11)	−0.0042 (11)	0.0066 (13)
C12	0.0439 (13)	0.0408 (13)	0.0469 (13)	0.0127 (10)	−0.0015 (11)	0.0067 (11)
C13	0.0425 (13)	0.0390 (13)	0.0387 (12)	0.0049 (10)	0.0050 (10)	0.0009 (10)
C14	0.0391 (12)	0.0357 (12)	0.0288 (10)	−0.0002 (9)	0.0038 (9)	−0.0019 (8)
C15	0.0403 (13)	0.0453 (14)	0.0380 (12)	−0.0042 (10)	0.0016 (10)	−0.0030 (10)
C16	0.0488 (16)	0.0576 (17)	0.0509 (14)	−0.0158 (13)	0.0065 (12)	−0.0038 (12)
C17	0.071 (2)	0.0398 (14)	0.0586 (17)	−0.0117 (13)	0.0126 (14)	0.0040 (12)
C18	0.0580 (16)	0.0391 (13)	0.0509 (14)	0.0040 (11)	0.0080 (13)	0.0058 (12)
C19	0.0405 (15)	0.0606 (17)	0.0661 (17)	−0.0012 (12)	−0.0076 (12)	−0.0011 (14)

Geometric parameters (Å, º)

Co1—O1	1.930 (2)	C7—H7C	0.9600
Co1—O2^i	1.994 (2)	C8—H8	0.9300
Co1—N1	2.044 (2)	C9—C10	1.519 (4)
Co1—N2	2.074 (2)	C9—H9A	0.9700
Co1—O2	2.100 (2)	C9—H9B	0.9700
O1—C2	1.297 (3)	C10—C11	1.511 (4)
O2—C14	1.316 (3)	C10—H10A	0.9700
O2—Co1^i	1.9940 (16)	C10—H10B	0.9700
N1—C8	1.285 (3)	C11—H11A	0.9700
N1—C9	1.475 (3)	C11—H11B	0.9700
N2—C12	1.282 (3)	C12—C13	1.460 (4)
N2—C11	1.473 (3)	C12—H12	0.9300
C1—C6	1.411 (3)	C13—C14	1.411 (3)
C1—C2	1.418 (3)	C13—C18	1.411 (4)
C1—C8	1.435 (4)	C14—C15	1.414 (3)
C2—C3	1.421 (3)	C15—C16	1.378 (4)
C3—C4	1.378 (4)	C15—C19	1.498 (4)
C3—C7	1.493 (4)	C16—C17	1.379 (4)
C4—C5	1.383 (4)	C16—H16	0.9300
C4—H4	0.9300	C17—C18	1.365 (4)
C5—C6	1.358 (4)	C17—H17	0.9300
C5—H5	0.9300	C18—H18	0.9300
C6—H6	0.9300	C19—H19A	0.9600
C7—H7A	0.9600	C19—H19B	0.9600
C7—H7B	0.9600	C19—H19C	0.9600
O1—Co1—O2^i	114.31 (7)	C1—C8—H8	116.4
O1—Co1—N1	91.38 (7)	N1—C9—C10	111.3 (2)
O2^i—Co1—N1	106.27 (7)	N1—C9—H9A	109.4
O1—Co1—N2	136.01 (8)	C10—C9—H9A	109.4
O2^i—Co1—N2	106.47 (7)	N1—C9—H9B	109.4
N1—Co1—N2	92.54 (8)	C10—C9—H9B	109.4
O1—Co1—O2	86.74 (7)	H9A—C9—H9B	108.0
O2^i—Co1—O2	79.91 (7)	C11—C10—C9	115.3 (2)
N1—Co1—O2	173.77 (7)	C11—C10—H10A	108.4
N2—Co1—O2	84.73 (7)	C9—C10—H10A	108.4
C2—O1—Co1	129.51 (15)	C11—C10—H10B	108.4
C14—O2—Co1^i	126.19 (14)	C9—C10—H10B	108.4
C14—O2—Co1	122.17 (14)	H10A—C10—H10B	107.5
Co1^i—O2—Co1	99.41 (7)	N2—C11—C10	113.8 (2)
C8—N1—C9	116.9 (2)	N2—C11—H11A	108.8
C8—N1—Co1	123.76 (16)	C10—C11—H11A	108.8
C9—N1—Co1	119.16 (16)	N2—C11—H11B	108.8
C12—N2—C11	116.6 (2)	C10—C11—H11B	108.8
C12—N2—Co1	124.28 (16)	H11A—C11—H11B	107.7
C11—N2—Co1	119.08 (16)	N2—C12—C13	126.8 (2)
C6—C1—C2	119.6 (2)	N2—C12—H12	116.6
C6—C1—C8	116.8 (2)	C13—C12—H12	116.6
C2—C1—C8	123.5 (2)	C14—C13—C18	119.5 (2)
O1—C2—C1	123.8 (2)	C14—C13—C12	123.0 (2)
O1—C2—C3	118.3 (2)	C18—C13—C12	117.5 (2)
C1—C2—C3	117.9 (2)	O2—C14—C13	121.2 (2)
C4—C3—C2	119.6 (2)	O2—C14—C15	119.9 (2)
C4—C3—C7	121.6 (3)	C13—C14—C15	118.9 (2)
C2—C3—C7	118.8 (2)	C16—C15—C14	119.0 (2)
C3—C4—C5	122.4 (3)	C16—C15—C19	122.6 (2)
C3—C4—H4	118.8	C14—C15—C19	118.4 (2)
C5—C4—H4	118.8	C15—C16—C17	122.2 (3)
C6—C5—C4	119.1 (2)	C15—C16—H16	118.9
C6—C5—H5	120.5	C17—C16—H16	118.9
C4—C5—H5	120.5	C18—C17—C16	119.8 (3)
C5—C6—C1	121.4 (2)	C18—C17—H17	120.1
C5—C6—H6	119.3	C16—C17—H17	120.1
C1—C6—H6	119.3	C17—C18—C13	120.5 (3)
C3—C7—H7A	109.5	C17—C18—H18	119.8
C3—C7—H7B	109.5	C13—C18—H18	119.8
H7A—C7—H7B	109.5	C15—C19—H19A	109.5
C3—C7—H7C	109.5	C15—C19—H19B	109.5
H7A—C7—H7C	109.5	H19A—C19—H19B	109.5
H7B—C7—H7C	109.5	C15—C19—H19C	109.5
N1—C8—C1	127.1 (2)	H19A—C19—H19C	109.5
N1—C8—H8	116.4	H19B—C19—H19C	109.5

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