Di-[mu]-methoxo-bis({N,N'-bis­[2-(3,5-di­methyl­pyrazol-1-yl)­ethyl]­amine-[kappa]³N}copper(II)) bis­(hexa­fluoro­phosphate)

The title compound, [Cu₂(C₁₄H₂₃N₅)₂(CH₃O)₂](PF₆)₂, has a doubly methoxo-bridged centrosymmetric copper dimer cation involving two tridentate bis­(pyrazolyl)­amine ligands. The geometry of each Cu^II atom is a distorted square pyramid with two N atoms of the pyrazole in bis­[2-(3,5-di­methyl-1-pyrazolyl)­ethyl]­amine (bpea) and two [mu]₂-bridging O atoms of the methoxo ligands forming the basal plane, and the amine N atom occupying the axial position. In the bridging plane, the Cu-O bond lengths are 1.940 (4) and 1.942 (4) Å, and the bond angles for O-Cu-O and Cu-O-Cu are 76.1 (2) and 103.9 (2)°, respectively. The Cu...Cu distance is 3.058 (1) Å. The central four-membered ring lies on an inversion centre.

S1. Comment

Copper plays an important role in a variety of biological functions as an essential trace element (Kaim & Rall, 1996). The copper ions as centres of the active site in metalloproteins are involved in biological processes like electron transfer, oxidation and dioxygen transport (Solomon et al., 1992). A great number of transition metal complexes of poly(pyrazolyl)borate (Trofimenko, 1993) and pyrazole-based chelating ligands (Mukherjee, 2000) have been found in coordination chemistry. However, the bis(pyrazolylethyl)amine derivative is rare in spite of the extensive studies for various nitrogen heterocyclic ligand systems (Sorrell & Malachowski, 1983; Martens et al., 1995). The Cu^I compound of bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine was investigated as well as that of bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl] ether having the unsaturated T-shape arrangement (Sorrell & Malachowski, 1983), but its crystal structure was not explored. More recently, the mononuclear Cu^II complexes of bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine involving T-shape and square pyramidal coordination geometry were prepared and their structures have been characterized (Martens et al., 1995), but their dicopper(II) complexes have not been reported yet. In this context, we report the crystal structure of the title compound, (I), as an extension of the doubly methoxo-bridged dimeric copper complex type. The title compound consists of doubly methoxo-bridged dinuclear copper(II) units, two bpea ligands and two hexafluorophosphates. \scheme

The dinuclear unit has a centre of symmetry at the mid-point of the bridging plane. The Cu—Cuⁱ [symmetry code: (i) −x, 2 − y, −z] distance [3.058 (1) Å] is slightly longer than the values in the range 2.970 (7)–3.037 (2) Å in analogous methoxo-bridged copper(II) complexes (Willett & Breneman, 1983; Drew et al., 1988; van Albada et al., 1995, 1997; Komaei et al., 1999). In the bridging plane, bond lengths of Cu—O1 and Cu—O1ⁱ are 1.940 (4) and 1.942 (4) Å, and bond angles of O1—Cu—O1ⁱ and Cu—O1—Cuⁱ are 76.1 (2) and 103.9 (2)°, respectively. Each copper ion is five-coordinate, surrounded by three N atoms of bpea and two O atoms of methoxy. The coordination geometry around each Cu atom is described as a distorted square pyramid. In the title compound, The N atom of each pyrazole in bpea and µ₂-bridging O atom in each methoxy are in the equatorial positions with bond angles ranging between 76.1 (2) and 94.4 (2)°, whereas nitrogen atom of amine in bpea is in the axial position. The Cu—N bond lengths [1.991 (5)–2.317 (5) Å] are slightly longer than those [1.923 (1)–2.075 (8) Å] in the related mononuclear copper complexes (Martens et al., 1995); these values are consistent with the distances between copper and typical σ-donor nitrogen heterocyclic rings. Each amine nitrogen atom is in an axial position trans to the equatorial plane containing nitrogen atom of each pyrazole in bpea and oxygen atom of each methoxy. The Cu—N(amine) [2.317 (5) Å] bond distance of the axial position, due to an elongation of Jahn-Teller effect, is about 0.309 Å longer than Cu—N(pyrazole) bond distances [average 2.009 (5) Å] in the equatorial plane.

S2. Experimental

All chemicals were purchased from Aldrich and used as received. All reactions were performed under argon using standard Schlenk technique and the solvents were freshly distilled prior to use. Elemental analyses were carried out on a FIFONS, EA 1110/EA1108 by Chemical Analysis Laboratory of Korea Basic Science Institute at Kyungpook National University. To a solution of 5 g (0.019 mol) of bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine (bpea), prepared according to the synthetic procedures of Sorrell and Martens groups (Sorrell & Malachowski, 1983; Martens et al., 1995), in 200 ml of acetonitrile was added slowly 7.13 g (0.019 mol) of [Cu(CH₃CN)₄](PF₆), prepared by the method of Kubas (1979) and the mixture was stirred for 5 days at room temperature. The white solid was precipitated within 1 day and the resulting solid was filtered off and dried in vacuo. The white solid (7.87 g) was dissolved in 50 ml of methanol, the solution was rapidly converted to dark green and was left to stand at room temperature for several days to afford the green crystals. Yield: 8.45 g (82% based on copper atom). Analysis calculated for C₃₀H₅₂N₁₀O₂Cu₂P₂F₁₂: C 35.97, H 5.23, N 13.98%; Found: C 36.12, H 5.16, N 13.98%.

S3. Refinement

A carbon atom of the methyl group at pyrazole and all fluorine atoms were disordered, and were refined with isotropic displacement parameters.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: XCAD (McArdle, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

(I)

Crystal data

[Cu2(C14H23N5)2(CH3O)2](PF6)2	F(000) = 2056
Mr = 1001.86	Dx = 1.472 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 25 reflections
a = 15.1607 (7) Å	θ = 9.8–12.5°
b = 12.7860 (9) Å	µ = 1.10 mm^−1
c = 23.316 (1) Å	T = 293 K
V = 4519.7 (4) Å^3	Tetragonal rod, green
Z = 4	0.40 × 0.30 × 0.30 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.007
Radiation source: fine-focus sealed tube	θmax = 25.5°, θmin = 1.8°
Graphite monochromator	h = 0→18
ω/2θ scans	k = 0→15
4256 measured reflections	l = 0→28
4174 independent reflections	2 standard reflections every 60 min
2065 reflections with I > 2σ(I)	intensity decay: 0.2%

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)] = 0.069	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.189	H-atom parameters constrained
S = 1.38	w = 1/[σ^2(Fo^2) + (0.072P)^2] where P = (Fo^2 + 2Fc^2)/3
4174 reflections	(Δ/σ)max = 0.014
255 parameters	Δρmax = 0.98 e Å^−3
0 restraints	Δρmin = −0.53 e Å^−3

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cu	0.03778 (4)	0.92866 (6)	0.04655 (3)	0.0399 (2)
N1	0.1639 (3)	0.9138 (4)	0.0742 (2)	0.0477 (14)
C1	0.2382 (4)	0.9068 (5)	0.0430 (3)	0.0501 (16)
C2	0.3097 (4)	0.8942 (6)	0.0806 (3)	0.063 (2)
H2	0.3685	0.8860	0.0702	0.076*
C3	0.2778 (5)	0.8962 (8)	0.1338 (4)	0.088 (3)
N2	0.1886 (4)	0.9059 (5)	0.1296 (2)	0.0627 (18)
C4	0.1253 (5)	0.9149 (7)	0.1754 (3)	0.072 (3)
H4A	0.1563	0.9130	0.2118	0.086*
H4B	0.0861	0.8549	0.1742	0.086*
C5	0.0699 (5)	1.0150 (7)	0.1727 (3)	0.067 (2)
H5A	0.0486	1.0327	0.2107	0.080*
H5B	0.1059	1.0725	0.1589	0.080*
N3	−0.0056 (4)	0.9989 (5)	0.1337 (2)	0.0525 (14)
H3N	−0.0259	1.0642	0.1254	0.063*
C6	−0.0791 (5)	0.9457 (6)	0.1622 (3)	0.065 (2)
H6A	−0.1213	0.9976	0.1752	0.078*
H6B	−0.0570	0.9093	0.1958	0.078*
C7	−0.1253 (5)	0.8691 (6)	0.1245 (4)	0.064 (2)
H7A	−0.1787	0.8451	0.1433	0.077*
H7B	−0.1422	0.9033	0.0890	0.077*
N4	−0.0683 (4)	0.7778 (4)	0.1113 (2)	0.0496 (14)
N5	0.0011 (4)	0.7877 (4)	0.0739 (2)	0.0496 (14)
C8	0.0350 (5)	0.6926 (5)	0.0689 (3)	0.0560 (18)
C9	−0.0118 (5)	0.6230 (6)	0.1020 (3)	0.073 (2)
H9	−0.0010	0.5517	0.1054	0.087*
C10	−0.0774 (5)	0.6786 (5)	0.1290 (3)	0.0569 (19)
C11	0.2385 (5)	0.9125 (6)	−0.0195 (3)	0.068 (2)
H11A	0.1792	0.9068	−0.0335	0.102*
H11B	0.2734	0.8563	−0.0347	0.102*
H11C	0.2632	0.9781	−0.0314	0.102*
C12a	0.3222 (13)	0.8440 (16)	0.1890 (8)	0.088 (6)*	0.50
H12A	0.2910	0.8656	0.2228	0.133*	0.50
H12B	0.3826	0.8659	0.1917	0.133*	0.50
H12C	0.3196	0.7693	0.1856	0.133*	0.50
C12b	0.3247 (11)	0.9113 (14)	0.1905 (7)	0.070 (4)*	0.50
H12D	0.3261	0.9843	0.1999	0.105*	0.50
H12E	0.3839	0.8852	0.1875	0.105*	0.50
H12F	0.2938	0.8738	0.2200	0.105*	0.50
C13	0.1110 (6)	0.6712 (7)	0.0304 (4)	0.083 (3)
H13A	0.1030	0.7079	−0.0051	0.124*
H13B	0.1146	0.5974	0.0231	0.124*
H13C	0.1644	0.6943	0.0485	0.124*
C14	−0.1455 (6)	0.6437 (7)	0.1705 (4)	0.089 (3)
H14A	−0.1355	0.6767	0.2068	0.134*
H14B	−0.1423	0.5691	0.1749	0.134*
H14C	−0.2029	0.6626	0.1564	0.134*
O1	0.0596 (2)	1.0599 (3)	0.00707 (17)	0.0421 (10)
C15	0.1108 (4)	1.1426 (6)	0.0301 (3)	0.057 (2)
H15A	0.0744	1.1854	0.0543	0.086*
H15B	0.1342	1.1842	−0.0006	0.086*
H15C	0.1585	1.1141	0.0523	0.086*
P	0.09211 (14)	0.80109 (18)	0.33879 (10)	0.0675 (6)
F1A	0.0437 (10)	0.8742 (12)	0.2916 (6)	0.123 (5)*	0.50
F1B	0.0569 (6)	0.9041 (8)	0.3097 (4)	0.066 (3)*	0.50
F2A	0.1416 (11)	0.6978 (13)	0.3595 (7)	0.136 (6)*	0.50
F2B	0.1226 (8)	0.7121 (9)	0.3820 (5)	0.085 (4)*	0.50
F3A	0.1057 (14)	0.8849 (15)	0.3861 (8)	0.175 (7)*	0.50
F3B	0.1564 (8)	0.8648 (10)	0.3795 (5)	0.095 (4)*	0.50
F4A	0.1706 (8)	0.7851 (10)	0.2957 (5)	0.097 (3)*	0.50
F4B	0.1809 (7)	0.8423 (9)	0.3088 (5)	0.093 (3)*	0.50
F5A	0.0205 (7)	0.8350 (9)	0.3867 (4)	0.087 (3)*	0.50
F5B	0.0051 (8)	0.7623 (11)	0.3660 (6)	0.112 (4)*	0.50
F6A	0.0176 (10)	0.7321 (11)	0.3120 (6)	0.127 (4)*	0.50
F6B	0.0697 (9)	0.7255 (10)	0.2851 (5)	0.116 (4)*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.0337 (4)	0.0419 (4)	0.0440 (4)	0.0029 (4)	−0.0020 (4)	0.0071 (4)
N1	0.041 (3)	0.063 (4)	0.039 (3)	0.010 (3)	−0.002 (2)	0.003 (3)
C1	0.039 (3)	0.052 (4)	0.059 (4)	0.005 (3)	0.005 (3)	−0.001 (4)
C2	0.035 (4)	0.089 (6)	0.066 (5)	0.013 (4)	−0.002 (3)	−0.004 (4)
C3	0.056 (5)	0.146 (9)	0.061 (5)	0.024 (5)	−0.013 (4)	0.009 (6)
N2	0.044 (3)	0.098 (5)	0.046 (3)	0.017 (3)	−0.006 (3)	0.012 (3)
C4	0.051 (4)	0.122 (8)	0.043 (4)	0.020 (5)	0.000 (3)	0.018 (5)
C5	0.066 (5)	0.090 (6)	0.044 (4)	0.005 (5)	0.005 (4)	−0.006 (4)
N3	0.049 (3)	0.055 (4)	0.053 (3)	0.011 (3)	0.006 (3)	0.001 (3)
C6	0.063 (5)	0.072 (6)	0.061 (5)	0.016 (4)	0.018 (4)	−0.003 (4)
C7	0.048 (4)	0.050 (5)	0.094 (6)	0.007 (4)	0.020 (4)	0.021 (4)
N4	0.047 (3)	0.047 (4)	0.054 (3)	0.004 (3)	0.010 (3)	0.012 (3)
N5	0.047 (3)	0.044 (3)	0.058 (3)	0.010 (3)	0.010 (3)	0.012 (3)
C8	0.056 (4)	0.045 (4)	0.067 (4)	0.011 (4)	0.020 (4)	0.013 (3)
C9	0.087 (6)	0.044 (4)	0.086 (6)	0.012 (4)	0.008 (5)	0.016 (4)
C10	0.057 (4)	0.046 (4)	0.067 (5)	0.003 (4)	0.012 (4)	0.022 (4)
C11	0.058 (5)	0.083 (6)	0.063 (4)	0.001 (4)	0.006 (4)	0.005 (4)
C13	0.106 (7)	0.057 (5)	0.085 (6)	0.016 (5)	0.037 (5)	0.011 (4)
C14	0.085 (6)	0.082 (7)	0.101 (7)	0.006 (5)	0.036 (5)	0.037 (5)
O1	0.037 (2)	0.038 (2)	0.051 (2)	−0.0031 (19)	−0.0078 (18)	0.006 (2)
C15	0.050 (4)	0.050 (5)	0.072 (5)	−0.010 (4)	−0.004 (3)	−0.004 (4)
P	0.0620 (13)	0.0616 (14)	0.0791 (15)	0.0044 (11)	0.0056 (12)	0.0200 (12)

Geometric parameters (Å, º)

Cu—O1^i	1.940 (4)	C10—C14	1.483 (9)
Cu—O1	1.942 (4)	O1—C15	1.418 (7)
Cu—N5	1.991 (5)	O1—Cu^i	1.940 (4)
Cu—N1	2.026 (5)	P—F5B	1.545 (12)
Cu—N3	2.317 (5)	P—F3A	1.551 (19)
Cu—Cu^i	3.0582 (14)	P—F6A	1.563 (14)
N1—C1	1.345 (8)	P—F4A	1.570 (11)
N1—N2	1.347 (7)	P—F1B	1.574 (10)
C1—C2	1.404 (9)	P—F3B	1.585 (12)
C1—C11	1.458 (9)	P—F2B	1.590 (12)
C2—C3	1.333 (10)	P—F2A	1.594 (16)
C3—N2	1.361 (9)	P—F4B	1.605 (11)
C3—C12b	1.512 (18)	P—F5A	1.617 (10)
C3—C12a	1.597 (19)	P—F6B	1.618 (13)
N2—C4	1.442 (8)	P—F1A	1.620 (15)
C4—C5	1.533 (11)	F1A—F1B	0.605 (17)
C5—N3	1.475 (9)	F2A—F2B	0.626 (18)
N3—C6	1.466 (9)	F3A—F3B	0.82 (2)
C6—C7	1.492 (10)	F3A—F5A	1.441 (19)
C7—N4	1.484 (9)	F3B—F4B	1.713 (15)
N4—C10	1.342 (8)	F4A—F4B	0.808 (13)
N4—N5	1.372 (7)	F4A—F6B	1.727 (17)
N5—C8	1.326 (8)	F5A—F5B	1.074 (14)
C8—C9	1.374 (10)	F5B—F6A	1.330 (16)
C8—C13	1.485 (10)	F6A—F6B	1.013 (15)
C9—C10	1.376 (10)
O1^i—Cu—O1	76.06 (18)	F3B—P—F2B	79.0 (6)
O1^i—Cu—N5	93.5 (2)	F5B—P—F2A	90.6 (8)
O1—Cu—N5	168.9 (2)	F3A—P—F2A	107.1 (9)
O1^i—Cu—N1	158.46 (19)	F6A—P—F2A	89.6 (8)
O1—Cu—N1	94.09 (19)	F4A—P—F2A	74.3 (7)
N5—Cu—N1	94.4 (2)	F1B—P—F2A	169.5 (7)
O1^i—Cu—N3	108.66 (19)	F3B—P—F2A	87.4 (7)
O1—Cu—N3	97.43 (19)	F2B—P—F2A	22.7 (6)
N5—Cu—N3	89.5 (2)	F5B—P—F4B	178.3 (6)
N1—Cu—N3	91.4 (2)	F3A—P—F4B	88.3 (9)
O1^i—Cu—Cu^i	38.05 (12)	F6A—P—F4B	128.1 (7)
O1—Cu—Cu^i	38.01 (11)	F4A—P—F4B	29.4 (5)
N5—Cu—Cu^i	131.49 (17)	F1B—P—F4B	79.8 (5)
N1—Cu—Cu^i	129.45 (16)	F3B—P—F4B	64.9 (6)
N3—Cu—Cu^i	106.56 (14)	F2B—P—F4B	105.5 (6)
C1—N1—N2	106.3 (5)	F2A—P—F4B	90.5 (7)
C1—N1—Cu	128.6 (4)	F5B—P—F5A	39.6 (5)
N2—N1—Cu	125.1 (4)	F3A—P—F5A	54.0 (8)
N1—C1—C2	108.4 (6)	F6A—P—F5A	86.7 (7)
N1—C1—C11	122.8 (6)	F4A—P—F5A	170.2 (6)
C2—C1—C11	128.8 (6)	F1B—P—F5A	81.1 (5)
C3—C2—C1	107.5 (6)	F3B—P—F5A	82.0 (6)
C2—C3—N2	107.1 (7)	F2B—P—F5A	87.1 (6)
C2—C3—C12b	130.2 (9)	F2A—P—F5A	109.2 (7)
N2—C3—C12b	121.3 (9)	F4B—P—F5A	140.8 (6)
C2—C3—C12a	126.1 (10)	F5B—P—F6B	86.9 (7)
N2—C3—C12a	121.0 (10)	F3A—P—F6B	172.2 (9)
C12a—C3—C12b	32.0 (8)	F6A—P—F6B	37.1 (6)
N1—N2—C3	110.7 (6)	F4A—P—F6B	65.6 (6)
N1—N2—C4	121.2 (5)	F1B—P—F6B	95.5 (6)
C3—N2—C4	127.9 (6)	F3B—P—F6B	154.0 (7)
N2—C4—C5	113.6 (6)	F2B—P—F6B	97.1 (6)
N3—C5—C4	109.5 (6)	F2A—P—F6B	80.7 (7)
C6—N3—C5	112.1 (6)	F4B—P—F6B	92.0 (6)
C6—N3—Cu	115.7 (4)	F5A—P—F6B	123.7 (7)
C5—N3—Cu	112.0 (4)	F5B—P—F1A	94.4 (7)
N3—C6—C7	113.2 (6)	F3A—P—F1A	98.3 (9)
N4—C7—C6	111.4 (6)	F6A—P—F1A	74.1 (7)
C10—N4—N5	111.2 (5)	F4A—P—F1A	89.1 (6)
C10—N4—C7	128.3 (6)	F1B—P—F1A	21.8 (6)
N5—N4—C7	120.4 (5)	F3B—P—F1A	112.9 (7)
C8—N5—N4	105.6 (5)	F2B—P—F1A	167.5 (7)
C8—N5—Cu	133.9 (5)	F2A—P—F1A	153.8 (8)
N4—N5—Cu	120.1 (4)	F4B—P—F1A	84.0 (7)
N5—C8—C9	110.1 (6)	F5A—P—F1A	90.6 (6)
N5—C8—C13	121.5 (6)	F6B—P—F1A	74.0 (7)
C9—C8—C13	128.3 (7)	F1B—F1A—P	75 (2)
C8—C9—C10	107.2 (7)	F1A—F1B—P	83 (2)
N4—C10—C9	105.8 (6)	F2B—F2A—P	78 (2)
N4—C10—C14	123.9 (7)	F2A—F2B—P	79 (2)
C9—C10—C14	130.3 (7)	F3B—F3A—F5A	134 (2)
C15—O1—Cu^i	127.2 (4)	F3B—F3A—P	77.1 (18)
C15—O1—Cu	123.9 (4)	F5A—F3A—P	65.3 (10)
Cu^i—O1—Cu	103.94 (18)	F3A—F3B—P	72.5 (17)
F5B—P—F3A	92.5 (9)	F3A—F3B—F4B	115.7 (19)
F5B—P—F6A	50.7 (6)	P—F3B—F4B	58.1 (5)
F3A—P—F6A	140.4 (10)	F4B—F4A—P	77.7 (13)
F5B—P—F4A	150.1 (7)	F4B—F4A—F6B	128.8 (16)
F3A—P—F4A	116.3 (9)	P—F4A—F6B	58.6 (6)
F6A—P—F4A	102.6 (7)	F4A—F4B—P	72.8 (13)
F5B—P—F1B	99.0 (6)	F4A—F4B—F3B	118.3 (15)
F3A—P—F1B	76.9 (8)	P—F4B—F3B	57.0 (5)
F6A—P—F1B	93.2 (6)	F5B—F5A—F3A	125.0 (14)
F4A—P—F1B	95.2 (6)	F5B—F5A—P	66.6 (9)
F5B—P—F3B	116.4 (7)	F3A—F5A—P	60.6 (9)
F3A—P—F3B	30.4 (7)	F5A—F5B—F6A	130.3 (15)
F6A—P—F3B	166.7 (7)	F5A—F5B—P	73.8 (9)
F4A—P—F3B	89.1 (6)	F6A—F5B—P	65.4 (9)
F1B—P—F3B	92.1 (6)	F6B—F6A—F5B	136.2 (17)
F5B—P—F2B	76.0 (6)	F6B—F6A—P	74.4 (12)
F3A—P—F2B	90.3 (8)	F5B—F6A—P	64.0 (8)
F6A—P—F2B	93.4 (7)	F6A—F6B—P	68.5 (12)
F4A—P—F2B	95.3 (6)	F6A—F6B—F4A	124.3 (15)
F1B—P—F2B	166.1 (6)	P—F6B—F4A	55.9 (6)

Symmetry code: (i) −x, −y+2, −z.