Bis[μ-4-(ethylammoniomethyl)-3,5-dimethylpyrazolato-κ²N¹:N²]bis[(η⁴-1,5-cyclooctadiene)rhodium(I)] dichloride dichloromethane methanol solvate

In the title compound, [Rh₂(C₈H₁₅N₃)₂(C₈H₁₂)₂]Cl₂·CH₂Cl₂·CH₃OH, the dinuclear Rh^I complex has C₂ symmetry and the two pyrazolato ligands act as μ-bridges. The coordination of each Rh^I cation is completed by one cyclo­octa­diene (COD) ligand. It is shown that the average Rh—C(COD) distance is linearly dependent on the Rh—N(pyrazole) distance in this type of compound, and this is ascribed to the steric hindrance produced by the packing.

S1. Comment

Research into the coordination chemistry of pyrazole-derived ligands has progressed rapidly over the last two decades. Mukherjee (2000) published an extensive review, completing those presented by La Monica & Ardizzoia (1997) and Trofimenko (1972, 1986, 1993). Only four structures of dinuclear rhodium(I) complexes with pyrazole bridges and cyclooctadiene ligands (COD) (Louie et al., 1984; Cano et al., 1997; Esquius et al., 2000) are present in the Cambridge Structural Database (CSD; Version?; Allen & Kennard, 1993). A feature of these compounds is the poorly understood variation of the Rh—C and Rh—N bond distances, with no explanation elucidated to date. In order to increase understanding of this distance variation, the title compound, (I), was prepared, which is similar to those previously published by Esquius et al. (2000). \sch

The molecular structure of (I) is shown in Fig. 1 and selected geometric details are given in Table 1. The structure of (I) consists of discrete molecules separated by van der Waals interactions and weak hydrogen bonds (Table 2).

The methanol molecules were located as disordered, and atom O1 seems to form a hydrogen bond with a Cl^- anion [O1···Cl1ⁱ 3.118 (4) Å; symmetry code (i) 1/2 - x, 1/2 - y, 1 - z]. Each Rh atom is linked to four C atoms of a cyclooctadiene ligand and two N atoms of two different pyrazole units. The pyrazole acts as a µ-N,N' bridge between two Rh atoms. The Rh—N1—N2—Rhⁱ torsion angle is 2.43 (19)°. The planarity of this moiety is similar to that observed when the pyrazole lacks a bulky substituent in position 4 (Louie et al., 1984; Esquius et al., 2000). The dihedral angle between the Rh/N1/N2/Rhⁱ and pyrazole planes is 20.17 (10)°. The ethylammoniomethyl moiety is planar and twisted by 87.0 (2)° with respect to the pyrazole plane.

If the average Rh—C(COD) and Rh—N(pyrazole) lengths are compared, it is observed that <Rh—C> increases when <Rh—N> increases (Fig. 2), while the N—N and C—C lengths remain practically constant [average values in the five structures 1.360 (7) and 1.375 (12) Å, respectively]. This suggests that the bond lengths involving the Rh atom are more affected by the steric hindrance of the packing than by electronic effects. This is corroborated by the two electronically more similar pyrazole ligands, 3,5-dimethyl-4-[N-(isopropyl)aminomethyl]pyrazolyl and 3,5-dimethyl-4-(ethylammonium)methylpyrazolato, presenting the limiting values.

S2. Experimental

To prepare (I), [RhCl(COD)]₂ (0.08 g, 0.16 mmol) dissolved in CH₂Cl₂ (5 ml) was added to a solution of 3,5-dimethyl-4-(ethylamino)methylpyrazole (0.08 g, 0.32 mmol) in CH₂Cl₂ (5 ml) and the mixture stirred for 15 h. The solvent was evaporated to dryness in vacuo and the residue was washed with Et₂O and dissolved in a minimum amount of CH₂Cl₂. The title complex was precipitated by adding hexane to the solution. A yellow-orange solid was filtered off and dried in vacuo. Crystals of (I) were obtained by evaporation of a methanol solution.

S3. Refinement

The methanol atoms O1 and C19 were located from a difference Fourier synthesis. Their occupancy factor of 0.5 was assigned according to the peak heights. The molar ratio with respect to the remaining formula was confirmed by elemetal analysis. The H atoms on N15 were refined freely. The positions of 27 H atoms were geometrically computed (C—H = 0.93–0.97 Å) and refined using a riding model, with U_iso(H) = 1.2U_eq(C). Dichloromethane H atoms were located from a difference Fourier synthesis, while methanol H atoms were not located.

Computing details

Data collection: CAD-4-PC (Kretschmar, 1996); cell refinement: CAD-4-PC; data reduction: CFEO (Solans, 1978); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3.2 (Brueggermann & Schmid, 1990); software used to prepare material for publication: PLATON (Spek, 1990).

Figures

	Fig. 1. A view of the molecular structure of (I) showing 50% probability displacement ellipsoids and the atom-numbering scheme. The H atoms, the Cl^- anions and the dichloromethane and methanol solvent molecules have been omitted for clarity.
	Fig. 2. A graph of average Rh—C versus average Rh—N bond length in µ-pyrazole [Rh(COD)]2 units.

Bis[µ-2-(ethylammoniomethyl)-3,5-dimethylpyrazolato-κ²N¹:N²] bis[(η⁴-1,5-cyclooctadiene)rhodium(I)] dichloride dichloromethane methanol solvate

Crystal data

[Rh2(C8H12)2(C8H15N3)2]Cl2·CH2Cl2·CH3OH	F(000) = 1888
Mr = 916.52	Dx = 1.492 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71069 Å
a = 12.587 (3) Å	Cell parameters from 25 reflections
b = 25.762 (9) Å	θ = 12–21°
c = 13.240 (13) Å	µ = 1.11 mm^−1
β = 108.24 (3)°	T = 293 K
V = 4078 (4) Å^3	Prism, yellow-orange
Z = 4	0.2 × 0.1 × 0.1 mm

Data collection

Enraf-Nonius CAD4 diffractometer	Rint = 0.061
Radiation source: fine-focus sealed tube	θmax = 30.0°, θmin = 2.9°
Graphite monochromator	h = −17→16
ω/2θ scans	k = 0→36
6120 measured reflections	l = 0→18
5860 independent reflections	3 standard reflections every 120 min
4234 reflections with I > 2σ(I)	intensity decay: none

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.079	H atoms treated by a mixture of independent and constrained refinement
S = 0.98	w = 1/[σ^2(Fo^2) + (0.0406P)^2] where P = (Fo^2 + 2Fc^2)/3
5860 reflections	(Δ/σ)max = 0.001
222 parameters	Δρmax = 0.58 e Å^−3
3 restraints	Δρmin = −0.35 e Å^−3

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Rh	0.368702 (14)	0.012875 (6)	0.223891 (13)	0.03982 (6)
Cl1	0.29491 (6)	0.24395 (3)	0.19975 (6)	0.06726 (19)
N1	0.45771 (15)	0.06334 (7)	0.34608 (14)	0.0405 (4)
N2	0.57245 (15)	0.06280 (7)	0.37158 (14)	0.0403 (4)
C1	0.2320 (2)	−0.01485 (11)	0.0936 (2)	0.0600 (7)
H1	0.2340	0.0165	0.0594	0.072*
C2	0.3204 (3)	−0.04776 (9)	0.1084 (2)	0.0565 (6)
H2	0.3797	−0.0372	0.0854	0.068*
C3	0.3272 (3)	−0.10054 (11)	0.1604 (2)	0.0823 (10)
H3	0.2567	−0.1183	0.1284	0.099*
H3A	0.3849	−0.1205	0.1437	0.099*
C4	0.3511 (4)	−0.10107 (12)	0.2772 (3)	0.0850 (10)
H4	0.4211	−0.1193	0.3088	0.102*
H4A	0.2928	−0.1208	0.2934	0.102*
C5	0.3592 (3)	−0.04897 (10)	0.3291 (2)	0.0563 (6)
H5	0.4290	−0.0382	0.3727	0.094 (11)*
C6	0.2704 (2)	−0.01616 (11)	0.3163 (2)	0.0570 (6)
H6	0.2835	0.0153	0.3525	0.068*
C7	0.1537 (3)	−0.02780 (19)	0.2476 (4)	0.0992 (13)
H7	0.1036	−0.0035	0.2656	0.119*
H7A	0.1341	−0.0623	0.2655	0.119*
C8	0.1320 (3)	−0.02559 (18)	0.1284 (4)	0.1025 (14)
H8	0.0999	−0.0585	0.0980	0.123*
H8A	0.0766	0.0011	0.0992	0.123*
C9	0.42690 (19)	0.10732 (8)	0.38193 (17)	0.0410 (5)
C10	0.52276 (19)	0.13607 (8)	0.43372 (17)	0.0434 (5)
C11	0.61203 (19)	0.10682 (8)	0.42437 (17)	0.0406 (5)
C12	0.3068 (2)	0.12061 (10)	0.3610 (2)	0.0533 (6)
H12	0.3000	0.1569	0.3747	0.064*
H12A	0.2770	0.1004	0.4068	0.064*
H12B	0.2660	0.1131	0.2882	0.064*
C13	0.7344 (2)	0.11906 (10)	0.4646 (2)	0.0557 (6)
H13	0.7758	0.0914	0.4459	0.067*
H13A	0.7574	0.1228	0.5405	0.067*
H13B	0.7484	0.1508	0.4330	0.067*
C14	0.5282 (2)	0.18736 (8)	0.48681 (18)	0.0478 (5)
H14	0.5994	0.1904	0.5426	0.057*
H14A	0.4695	0.1891	0.5198	0.057*
N15	0.51556 (17)	0.23207 (7)	0.41161 (16)	0.0456 (4)
H15	0.4514 (16)	0.2245 (13)	0.3597 (19)	0.090 (11)*
H15A	0.5720 (16)	0.2359 (10)	0.384 (2)	0.053 (8)*
C16	0.5197 (3)	0.28334 (9)	0.4674 (2)	0.0615 (7)
H16	0.5900	0.2863	0.5245	0.074*
H16A	0.4594	0.2850	0.4984	0.074*
C17	0.50856 (13)	0.32941 (6)	0.38751 (13)	0.0768 (9)
H17	0.4460	0.3233	0.3250	0.092*
H17A	0.5757	0.3320	0.3680	0.092*
H17B	0.4971	0.3612	0.4205	0.092*
Cl2	−0.01624 (13)	0.10663 (6)	0.13856 (13)	0.1601 (6)
C18	0.00000	0.14419 (6)	0.25000	0.137 (3)
H18	−0.0630	0.1732	0.2436	0.164*
O1	0.37938 (13)	0.23918 (6)	0.68000 (13)	0.152 (4)	0.50
C19	0.30026 (13)	0.24245 (6)	0.58611 (13)	0.198 (9)	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Rh	0.04882 (11)	0.03469 (9)	0.03230 (9)	−0.00783 (7)	0.00743 (6)	−0.00179 (7)
Cl1	0.0550 (4)	0.0763 (5)	0.0596 (4)	0.0027 (3)	0.0022 (3)	−0.0055 (3)
N1	0.0445 (9)	0.0367 (9)	0.0352 (9)	−0.0048 (7)	0.0051 (7)	−0.0039 (7)
N2	0.0483 (10)	0.0362 (9)	0.0339 (9)	0.0000 (7)	0.0092 (7)	−0.0044 (7)
C1	0.0712 (17)	0.0527 (14)	0.0415 (12)	−0.0145 (13)	−0.0033 (11)	−0.0058 (11)
C2	0.0790 (18)	0.0432 (13)	0.0430 (12)	−0.0175 (12)	0.0129 (12)	−0.0118 (10)
C3	0.123 (3)	0.0414 (14)	0.0623 (19)	−0.0038 (16)	−0.0003 (18)	−0.0068 (13)
C4	0.139 (3)	0.0491 (16)	0.083 (2)	−0.0006 (18)	0.058 (2)	0.0145 (15)
C5	0.0746 (17)	0.0503 (14)	0.0424 (12)	−0.0150 (13)	0.0158 (12)	0.0066 (11)
C6	0.0723 (17)	0.0546 (15)	0.0485 (13)	−0.0163 (13)	0.0253 (12)	−0.0035 (12)
C7	0.0619 (19)	0.116 (3)	0.114 (3)	−0.0118 (19)	0.020 (2)	0.041 (3)
C8	0.0613 (19)	0.126 (3)	0.107 (3)	−0.029 (2)	0.0061 (19)	−0.046 (3)
C9	0.0501 (12)	0.0382 (11)	0.0351 (10)	0.0007 (9)	0.0138 (9)	−0.0019 (9)
C10	0.0556 (13)	0.0337 (10)	0.0353 (11)	−0.0009 (9)	0.0062 (9)	−0.0033 (9)
C11	0.0453 (12)	0.0357 (10)	0.0357 (10)	−0.0032 (9)	0.0051 (9)	−0.0006 (8)
C12	0.0503 (13)	0.0510 (14)	0.0586 (15)	0.0044 (11)	0.0171 (11)	−0.0021 (12)
C13	0.0510 (13)	0.0467 (13)	0.0618 (15)	−0.0061 (11)	0.0066 (12)	−0.0033 (12)
C14	0.0633 (14)	0.0347 (10)	0.0406 (12)	0.0008 (10)	0.0094 (10)	−0.0041 (9)
N15	0.0500 (11)	0.0337 (9)	0.0450 (10)	−0.0007 (8)	0.0035 (9)	−0.0076 (8)
C16	0.0778 (18)	0.0372 (11)	0.0615 (16)	0.0040 (12)	0.0103 (13)	−0.0104 (12)
C17	0.086 (2)	0.0435 (14)	0.078 (2)	0.0089 (14)	−0.0060 (16)	−0.0054 (14)
Cl2	0.1539 (13)	0.1841 (16)	0.1469 (13)	0.0076 (11)	0.0535 (11)	0.0206 (11)
C18	0.105 (5)	0.094 (4)	0.192 (9)	0.000	0.021 (5)	0.000
O1	0.171 (8)	0.115 (5)	0.222 (10)	−0.042 (5)	0.137 (8)	−0.043 (6)
C19	0.225 (18)	0.117 (9)	0.33 (2)	0.000 (10)	0.209 (19)	−0.018 (14)

Geometric parameters (Å, º)

Rh—N2^i	2.095 (2)	C8—H8	0.9700
Rh—N1	2.104 (2)	C8—H8A	0.9700
Rh—C6	2.129 (3)	C9—C10	1.399 (3)
Rh—C2	2.137 (2)	C9—C12	1.489 (3)
Rh—C1	2.142 (3)	C10—C11	1.390 (3)
Rh—C5	2.144 (3)	C10—C14	1.488 (3)
Rh—Rh^i	3.1579 (9)	C11—C13	1.497 (3)
N1—C9	1.332 (3)	C12—H12	0.9600
N1—N2	1.377 (3)	C12—H12A	0.9600
N2—C11	1.343 (3)	C12—H12B	0.9600
N2—Rh^i	2.095 (2)	C13—H13	0.9600
C1—C2	1.364 (4)	C13—H13A	0.9600
C1—C8	1.496 (5)	C13—H13B	0.9600
C1—H1	0.9300	C14—N15	1.498 (3)
C2—C3	1.515 (4)	C14—H14	0.9700
C2—H2	0.9300	C14—H14A	0.9700
C3—C4	1.481 (5)	N15—C16	1.506 (3)
C3—H3	0.9700	N15—H15	0.903 (10)
C3—H3A	0.9700	N15—H15A	0.904 (10)
C4—C5	1.496 (4)	C16—C17	1.567 (3)
C4—H4	0.9700	C16—H16	0.9700
C4—H4A	0.9700	C16—H16A	0.9700
C5—C6	1.369 (4)	C17—H17	0.9600
C5—H5	0.9300	C17—H17A	0.9600
C6—C7	1.496 (5)	C17—H17B	0.9600
C6—H6	0.9300	Cl2—C18	1.7223
C7—C8	1.516 (6)	C18—Cl2^ii	1.722 (3)
C7—H7	0.9700	C18—H18	1.0741
C7—H7A	0.9700	O1—C19	1.3301
N2^i—Rh—N1	83.15 (9)	Rh—C6—H6	87.1
N2^i—Rh—C6	160.26 (10)	C6—C7—C8	116.6 (3)
N1—Rh—C6	92.33 (10)	C6—C7—H7	108.2
N2^i—Rh—C2	95.28 (11)	C8—C7—H7	108.2
N1—Rh—C2	164.91 (10)	C6—C7—H7A	108.2
C6—Rh—C2	93.91 (12)	C8—C7—H7A	108.2
N2^i—Rh—C1	93.74 (11)	H7—C7—H7A	107.3
N1—Rh—C1	157.72 (10)	C1—C8—C7	115.7 (3)
C6—Rh—C1	83.17 (13)	C1—C8—H8	108.4
C2—Rh—C1	37.17 (11)	C7—C8—H8	108.4
N2^i—Rh—C5	161.91 (10)	C1—C8—H8A	108.4
N1—Rh—C5	94.84 (10)	C7—C8—H8A	108.4
C6—Rh—C5	37.37 (11)	H8—C8—H8A	107.4
C2—Rh—C5	81.97 (12)	N1—C9—C10	108.80 (19)
C1—Rh—C5	94.66 (12)	N1—C9—C12	121.4 (2)
N2^i—Rh—Rh^i	65.70 (5)	C10—C9—C12	129.7 (2)
N1—Rh—Rh^i	64.07 (6)	C11—C10—C9	105.47 (19)
C6—Rh—Rh^i	129.11 (9)	C11—C10—C14	127.2 (2)
C2—Rh—Rh^i	101.56 (9)	C9—C10—C14	127.4 (2)
C1—Rh—Rh^i	134.27 (9)	N2—C11—C10	108.99 (19)
C5—Rh—Rh^i	97.19 (9)	N2—C11—C13	122.4 (2)
C9—N1—N2	108.73 (17)	C10—C11—C13	128.6 (2)
C9—N1—Rh	130.93 (15)	C9—C12—H12	109.5
N2—N1—Rh	116.59 (13)	C9—C12—H12A	109.5
C11—N2—N1	107.99 (17)	H12—C12—H12A	109.5
C11—N2—Rh^i	133.54 (16)	C9—C12—H12B	109.5
N1—N2—Rh^i	113.59 (13)	H12—C12—H12B	109.5
C2—C1—C8	124.6 (3)	H12A—C12—H12B	109.5
C2—C1—Rh	71.21 (14)	C11—C13—H13	109.5
C8—C1—Rh	110.8 (2)	C11—C13—H13A	109.5
C2—C1—H1	117.7	H13—C13—H13A	109.5
C8—C1—H1	117.7	C11—C13—H13B	109.5
Rh—C1—H1	88.0	H13—C13—H13B	109.5
C1—C2—C3	123.4 (3)	H13A—C13—H13B	109.5
C1—C2—Rh	71.63 (14)	C10—C14—N15	112.90 (19)
C3—C2—Rh	111.60 (19)	C10—C14—H14	109.0
C1—C2—H2	118.3	N15—C14—H14	109.0
C3—C2—H2	118.3	C10—C14—H14A	109.0
Rh—C2—H2	86.8	N15—C14—H14A	109.0
C4—C3—C2	116.6 (2)	H14—C14—H14A	107.8
C4—C3—H3	108.2	C14—N15—C16	111.6 (2)
C2—C3—H3	108.2	C14—N15—H15	103 (2)
C4—C3—H3A	108.2	C16—N15—H15	117 (2)
C2—C3—H3A	108.2	C14—N15—H15A	114.9 (17)
H3—C3—H3A	107.3	C16—N15—H15A	101.3 (17)
C3—C4—C5	115.7 (2)	H15—N15—H15A	110 (3)
C3—C4—H4	108.4	N15—C16—C17	110.5 (2)
C5—C4—H4	108.4	N15—C16—H16	109.5
C3—C4—H4A	108.4	C17—C16—H16	109.5
C5—C4—H4A	108.4	N15—C16—H16A	109.5
H4—C4—H4A	107.4	C17—C16—H16A	109.5
C6—C5—C4	124.2 (3)	H16—C16—H16A	108.1
C6—C5—Rh	70.73 (15)	C16—C17—H17	109.5
C4—C5—Rh	112.23 (19)	C16—C17—H17A	109.5
C6—C5—H5	117.9	H17—C17—H17A	109.5
C4—C5—H5	117.9	C16—C17—H17B	109.5
Rh—C5—H5	87.0	H17—C17—H17B	109.5
C5—C6—C7	124.0 (3)	H17A—C17—H17B	109.5
C5—C6—Rh	71.91 (15)	Cl2—C18—Cl2^ii	111.63 (8)
C7—C6—Rh	111.0 (2)	Cl2—C18—H18	115.9
C5—C6—H6	118.0	Cl2^ii—C18—H18	110.2
C7—C6—H6	118.0

Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N15—H15···Cl1	0.90	2.45	3.286 (4)	154
N15—H15A···Cl1^i	0.90	2.29	3.188 (4)	175

Symmetry code: (i) −x+1, y, −z+1/2.