Bis[bis­(methoxy­carbimido)aminato]copper(II) 1-methyl­pyrrolidin-2-one disolvate

The title compound, [Cu(C₄H₈N₃O₂)₂]·2C₅H₉NO, consists of a neutral copper complex, in which the Cu^II centre coordinates to two bis­(methoxy­carbimido)aminate ligands, solvated by two mol­ecules of 1-methyl­pyrrolidin-2-one. The complex is planar and centrosymmetric, with the Cu^II centre occupying a crystallographic inversion centre and adopting approximately square-planar geometry. N—H...O hy­dro­gen-bonding inter­actions exist between the amine NH groups of the ligands and the O atoms of the 1-methyl­pyrrolidin-2-one mol­ecules. The associated units pack to form sheets.

S1. Comment

A number of copper(II) complexes of the bis(methoxycarbimido)amine ligand, HN[C(NH)OCH₃]₂ (HL), have previously been prepared by reacting Cu^II salts with sodium dicyanamide in methanolic solutions. The ligand is generated in situ by nucleophilic addition of the methanol to the dicyanamide anion and, depending on the reaction conditions, may occur in either the protonated or deprotonated form, i.e. as HL or L^- (Atkinson et al., 2002) (see scheme).

Neutral HL ligands are found in [Cu{HN[C(NH)OCH₃]₂}₂](ClO₄)₂.2X [X = CH₃OH (Liu et al., 2007) and H₂O (Zheng et al., 2008)] and [Cu{HN[C(NH)OCH₃]₂]Br₂.2C₂H₅N₃O₂.2CH₃OH.0.8CH₃CN (C₂H₅N₃O₂ = biuret, Bishop et al., 2000). The anion, L^-, occurs in the neutral monomeric complex, [Cu{N[C(NH)OCH₃]₂}₂] (Kožíšek et al., 1990; Boča et al., 1996; Tong et al., 2003), and in the dimer, [Cu(µ-OCH₃){N[C(NH)OCH₃]₂}₂]₂, in which two Cu(L)₂ units are linked via methoxide bridges (Zhao et al., 2006). On heating the neutral monomeric complex with NH₄PF₆ in a CH₃OH/CH₃CN mixture, [Cu{N[C(NH)OCH₃]₂}{HN[C(NH)OCH₃]₂}]PF₆.CH₃CN, in which both neutral and anionic ligand species occur, is generated (Atkinson et al., 2002). Recently, attempts to explain the different conformations adopted by the neutral and anionic forms of the ligand in terms of their geometries and electronic structures have been made using ab initio molecular orbital (MO) calculations (Majek et al., 2004; Brudíková & Breza, 2004).

In this work, the structure of the title compound, [Cu{N[C(NH)OCH₃]₂}₂].2C₅H₉NO (C₅H₉NO = 1-methylpyrrolidin-2-one), a solvate of the neutral complex, [Cu{N[C(NH)OCH₃]₂}₂], is reported. The starting materials for the synthesis were copper(I) dicyanamide, CuN(CN)₂, 1-methylpyrrolidin-2-one and methanol. Cu⁺ is oxidized to Cu²⁺ during the reaction. It has previously been reported that oxidation of the Cu⁺ in CuN(CN)₂ occurs in aqueous ammonia/hydrazine, accompanied by partial hydration of dicyanamide to cyanourea, H₂N—CO—NH—CN, to generate the layered copper(II) hydroxide, Cu₂(OH)₃[H₂NC(O)NCN].2H₂O (Chippindale et al., 2009).

In the title compound, copper(II) is coordinated to two {N[C(NH)OCH₃]₂}₂ ligands to form a neutral complex containing two six-membered metallo-rings (Fig. 1). The Cu^II ion lies on an inversion centre, at special position 2a, coordinated by four N atoms in a square-planar array. The bond lengths and angles within the complex are similar to those observed previously in [Cu{N[C(NH)OCH₃]₂}₂] (Boča et al., 1996). The (H)N—C bonds (N1–C1 and N3 – C2) and N2–C bonds (N2–C1 and N2–C2) have average lengths of 1.302 (1) and 1.335 (1) Å, respectively. These values, together with the planarity of the metallocycle, indicate a highly delocalized π-bonding system. The conformations adopted by the methyl groups at C3 and C4, which point away from N1 and N3 with torsion angles N1—C1—O1—C3 and N3—C2—O2—C4 of 178.7 (1) and 178.2 (1) ° respectively, agree with those predicted previously for the anionic form of the ligand from MO calculations (Majek et al., 2004; Brudíková & Breza, 2004) and database mining (Atkinson et al., 2002).

Associated with each copper complex are two 1-methylpyrrolidin-2-one molecules held in place by hydrogen-bonding interactions between N1 and N3 of the copper complex and O3 of the pyrrolidinone (average N—O3 distance, 3.01 Å) (Table 2). The associated units pack in flat sheets parallel to the (1 0 1) plane and these stack abab along the a axis (Fig. 2). There are no strong interactions between neighbouring units within or between the sheets.

On gentle heating in N₂, the single crystal of [Cu{N[C(NH)OCH₃]₂}₂].2C₅H₉NO loses all solvent with the formation of polycrystalline [Cu{N[C(NH)OCH₃]₂}₂] (Boča et al., 1996). The packing of the copper complexes in this case reflects the fact that weak hydrogen-bonding interactions are formed between the amine NH groups and the O atoms of methoxy groups in neighbours.

Related literature

For related literature, see: Atkinson et al. (2002); Bishop et al. (2000); Boča et al. (1996); Brudíková & Breza (2004); Chippindale et al. (2009); Kožíšek et al. (1990); Liu et al. (2007); Majek et al. (2004); Wang et al. (1990); Zhao et al. (2006); Zheng et al. (2008).

S2. Experimental

Copper(I) dicyanamide (50 mg) (Wang et al., 1990) was dissolved in 1-methylpyrrolidin-2-one (6 ml) to form a dark-green solution. A 2 ml portion of this solution was transferred to a small sample vial, which was sealed inside a larger vial containing methanol (8 ml). No solid appeared after a period of 1 month. However, vapour diffusion over 18 months led to the growth of a single crystal of [Cu{N[C(NH)OCH₃]₂}₂].2C₅H₉NO within the inner vial in the form of a dark-pink block of dimensions 0.2 × 0.2 × 5 mm. A fragment of the crystal was used for the diffraction experiment. Attempts have not so far been made to optimize the crystallization conditions. Heating the crystal of the title compound under nitrogen from room temperature to 350 K over 30 min led to complete loss of 1-methylpyrrolidin-2-one and formation of violet-red polycrystalline [Cu{N[C(NH)OCH₃]₂}₂] (Boča et al., 1996), as confirmed by powder X-ray diffraction. During the desolvation reaction, bubbles were observed on the surface of the crystal.

S3. Refinement

All H atoms were located in difference Fourier maps. Their fractional coordinates were refined subject to bond-length restraints [C—H = 0.95 (1) Å, N—H = 0.85 (1) Å] with isotropic displacement parameters fixed at U_iso(H) = 1.2U_eq(C)and 1.2U_eq(N), respectively.

Computing details

Data collection: Xcalibur (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).

Figures

	Fig. 1. The title compound consisting of a square-planar Cu^II complex and 1-methylpyrrolidin-2-one. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitary radius. The dashed lines represent NH···O interactions. [Symmetry code: (i) -x, -y + 1, -z + 1.]
	Fig. 2. View along the b axis showing the stacking of the Cu^II complex and associated solvent molecules. The dashed lines represent NH···O interactions. Large white spheres, Cu; small white spheres, O; small light-grey spheres, N; small dark-grey spheres, C.

Bis[bis(methoxycarbimido)aminato]copper(II)–1-methylpyrrolidin-2-one (1/2)

Crystal data

[Cu(C4H8N3O2)2]·2C5H9NO	F(000) = 550
Mr = 522.08	Dx = 1.453 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8090 reflections
a = 7.52863 (18) Å	θ = 2.3–32.9°
b = 11.5650 (3) Å	µ = 0.97 mm^−1
c = 14.0547 (3) Å	T = 150 K
β = 102.833 (2)°	Block, pink
V = 1193.15 (5) Å^3	0.36 × 0.17 × 0.15 mm
Z = 2

Data collection

Oxford Diffraction Xcalibur diffractometer	3244 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.013
ω/2θ scans	θmax = 32.9°, θmin = 2.3°
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	h = −6→10
Tmin = 0.82, Tmax = 0.87	k = −7→17
8090 measured reflections	l = −21→20
3880 independent reflections

Refinement

Refinement on F	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.022	Only H-atom coordinates refined
wR(F^2) = 0.025	Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)^2]^2 Ai are: 13.1 -5.57 11.7 Prince, E. (1982). Mathematical Techniques in Crystallography and Materials Science. New York: Springer-Verlag. Watkin, D. J. (1994). Acta Cryst. A50, 411–437.
S = 1.04	(Δ/σ)max = 0.001
3097 reflections	Δρmax = 0.33 e Å^−3
196 parameters	Δρmin = −0.41 e Å^−3
17 restraints

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

	x	y	z	Uiso*/Ueq
Cu1	0.0000	0.5000	0.5000	0.0164
N1	−0.07897 (10)	0.33988 (6)	0.48426 (5)	0.0218
N2	0.05242 (10)	0.26462 (6)	0.64206 (5)	0.0219
N3	0.11767 (10)	0.46531 (6)	0.63448 (5)	0.0220
N4	0.45562 (10)	0.74412 (6)	0.86909 (5)	0.0244
O1	−0.11707 (10)	0.15338 (5)	0.52146 (5)	0.0265
O2	0.22157 (10)	0.36290 (6)	0.77153 (5)	0.0309
O3	0.32620 (11)	0.67872 (7)	0.71593 (5)	0.0369
C1	−0.04474 (10)	0.25871 (6)	0.55014 (5)	0.0195
C2	0.12526 (10)	0.36510 (7)	0.67728 (5)	0.0206
C3	−0.08590 (14)	0.06180 (7)	0.59258 (7)	0.0300
C4	0.22943 (19)	0.25484 (10)	0.82308 (7)	0.0403
C5	0.36415 (12)	0.75736 (8)	0.77636 (6)	0.0245
C6	0.31810 (15)	0.88354 (9)	0.75882 (8)	0.0358
C7	0.38976 (14)	0.94372 (8)	0.85648 (9)	0.0356
C8	0.48593 (12)	0.84988 (8)	0.92629 (7)	0.0275
C9	0.52978 (15)	0.63505 (9)	0.90959 (8)	0.0345
H33	−0.1424	−0.0071	0.5640	0.0360*
H32	0.0417	0.0490	0.6142	0.0360*
H31	−0.1280 (18)	0.0820 (14)	0.6486 (8)	0.0360*
H41	0.298 (2)	0.2693 (15)	0.8869 (8)	0.0484*
H42	0.292 (2)	0.1995 (12)	0.7934 (12)	0.0484*
H43	0.1096 (15)	0.2330 (16)	0.8274 (13)	0.0484*
H61	0.3723 (19)	0.9112 (14)	0.7090 (9)	0.0429*
H62	0.1886 (12)	0.8932 (15)	0.7368 (11)	0.0429*
H71	0.470 (2)	1.0052 (11)	0.8504 (14)	0.0427*
H72	0.2914 (18)	0.9748 (14)	0.8806 (12)	0.0427*
H81	0.6146 (12)	0.8606 (13)	0.9483 (10)	0.0331*
H82	0.4320 (19)	0.8416 (13)	0.9813 (8)	0.0331*
H93	0.486 (2)	0.6185 (15)	0.9668 (9)	0.0414*
H92	0.6578 (12)	0.6401 (14)	0.9215 (11)	0.0414*
H91	0.4812 (19)	0.5757 (11)	0.8655 (10)	0.0414*
H11	−0.1467 (15)	0.3158 (12)	0.4308 (7)	0.0261*
H34	0.1756 (18)	0.5170 (10)	0.6728 (9)	0.0263*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.01915 (6)	0.01562 (6)	0.01437 (6)	0.00031 (5)	0.00329 (4)	0.00078 (4)
N1	0.0290 (3)	0.0187 (3)	0.0162 (3)	−0.0021 (2)	0.0016 (2)	0.0000 (2)
N2	0.0274 (3)	0.0188 (3)	0.0184 (3)	0.0006 (2)	0.0029 (2)	0.0022 (2)
N3	0.0275 (3)	0.0187 (3)	0.0175 (3)	−0.0021 (2)	0.0003 (2)	0.0007 (2)
N4	0.0271 (3)	0.0198 (3)	0.0229 (3)	0.0017 (2)	−0.0018 (2)	−0.0005 (2)
O1	0.0379 (3)	0.0170 (2)	0.0229 (3)	−0.0036 (2)	0.0034 (2)	0.0002 (2)
O2	0.0434 (3)	0.0256 (3)	0.0177 (2)	−0.0001 (3)	−0.0061 (2)	0.0033 (2)
O3	0.0467 (4)	0.0334 (4)	0.0257 (3)	−0.0102 (3)	−0.0028 (3)	−0.0041 (3)
C1	0.0231 (3)	0.0166 (3)	0.0193 (3)	0.0001 (2)	0.0057 (2)	−0.0009 (2)
C2	0.0229 (3)	0.0214 (3)	0.0164 (3)	0.0021 (2)	0.0021 (2)	0.0010 (2)
C3	0.0424 (5)	0.0170 (3)	0.0306 (4)	−0.0014 (3)	0.0079 (3)	0.0031 (3)
C4	0.0589 (6)	0.0319 (5)	0.0234 (4)	0.0018 (4)	−0.0052 (4)	0.0107 (3)
C5	0.0249 (3)	0.0233 (4)	0.0232 (3)	−0.0034 (3)	0.0006 (3)	0.0034 (3)
C6	0.0393 (5)	0.0269 (4)	0.0389 (5)	0.0005 (4)	0.0038 (4)	0.0133 (4)
C7	0.0347 (4)	0.0204 (4)	0.0527 (6)	0.0009 (3)	0.0120 (4)	−0.0023 (4)
C8	0.0264 (4)	0.0267 (4)	0.0294 (4)	−0.0052 (3)	0.0060 (3)	−0.0070 (3)
C9	0.0365 (4)	0.0278 (4)	0.0351 (4)	0.0081 (3)	−0.0010 (4)	0.0069 (3)

Geometric parameters (Å, º)

Cu1—N3^i	1.9427 (7)	C3—H33	0.950
Cu1—N1^i	1.9424 (7)	C3—H32	0.953
Cu1—N1	1.9424 (7)	C3—H31	0.941 (8)
Cu1—N3	1.9427 (7)	C4—H41	0.945 (9)
N1—C1	1.3034 (10)	C4—H42	0.944 (9)
N1—H11	0.855 (8)	C4—H43	0.952 (9)
N2—C1	1.3375 (10)	C5—C6	1.5074 (13)
N2—C2	1.3324 (10)	C6—C7	1.5267 (16)
N3—C2	1.3012 (10)	C6—H61	0.941 (9)
N3—H34	0.856 (8)	C6—H62	0.961 (8)
N4—C5	1.3407 (11)	C7—C8	1.5327 (15)
N4—C8	1.4536 (11)	C7—H71	0.950 (9)
N4—C9	1.4441 (12)	C7—H72	0.951 (9)
O1—C1	1.3585 (9)	C8—H81	0.957 (8)
O1—C3	1.4393 (11)	C8—H82	0.955 (8)
O2—C2	1.3618 (9)	C9—H93	0.952 (9)
O2—C4	1.4391 (12)	C9—H92	0.943 (8)
O3—C5	1.2339 (11)	C9—H91	0.943 (9)
N3^i—Cu1—N1^i	88.61 (3)	H41—C4—H42	108.6 (14)
N3^i—Cu1—N1	91.39 (3)	O2—C4—H43	109.2 (11)
N1^i—Cu1—N1	180	H41—C4—H43	108.1 (14)
N3^i—Cu1—N3	180	H42—C4—H43	114.8 (15)
N1^i—Cu1—N3	91.39 (3)	N4—C5—O3	125.12 (9)
N1—Cu1—N3	88.61 (3)	N4—C5—C6	108.62 (8)
Cu1—N1—C1	126.76 (6)	O3—C5—C6	126.25 (8)
Cu1—N1—H11	121.2 (9)	C5—C6—C7	105.77 (8)
C1—N1—H11	112.0 (9)	C5—C6—H61	109.2 (11)
C1—N2—C2	119.67 (7)	C7—C6—H61	112.9 (10)
Cu1—N3—C2	126.68 (6)	C5—C6—H62	110.2 (11)
Cu1—N3—H34	121.8 (9)	C7—C6—H62	111.5 (10)
C2—N3—H34	111.5 (9)	H61—C6—H62	107.3 (13)
C5—N4—C8	115.16 (7)	C6—C7—C8	105.96 (7)
C5—N4—C9	123.58 (8)	C6—C7—H71	111.5 (12)
C8—N4—C9	121.17 (8)	C8—C7—H71	111.6 (11)
C1—O1—C3	117.45 (7)	C6—C7—H72	110.2 (11)
C2—O2—C4	117.35 (7)	C8—C7—H72	109.5 (11)
O1—C1—N2	115.45 (7)	H71—C7—H72	108.1 (14)
O1—C1—N1	115.60 (7)	C7—C8—N4	104.36 (7)
N2—C1—N1	128.96 (7)	C7—C8—H81	114.5 (9)
O2—C2—N2	115.56 (7)	N4—C8—H81	108.1 (9)
O2—C2—N3	115.18 (7)	C7—C8—H82	111.3 (9)
N2—C2—N3	129.26 (7)	N4—C8—H82	108.7 (9)
O1—C3—H33	109.6	H81—C8—H82	109.5 (12)
O1—C3—H32	109.5	N4—C9—H93	109.5 (10)
H33—C3—H32	109.3	N4—C9—H92	107.9 (10)
O1—C3—H31	111.4 (10)	H93—C9—H92	113.0 (13)
H33—C3—H31	111.1	N4—C9—H91	108.5 (10)
H32—C3—H31	105.9	H93—C9—H91	104.6 (14)
O2—C4—H41	106.1 (11)	H92—C9—H91	113.2 (13)
O2—C4—H42	109.6 (11)

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O3^i	0.86 (1)	2.20 (1)	3.0168 (14)	159 (1)
N3—H34···O3	0.86 (1)	2.20 (1)	3.0113 (14)	158 (1)

Symmetry code: (i) −x, −y+1, −z+1.