Nucleophilic addition reaction in coordinated non-linear pseudohalides: experimental charge density analysis in trans-bis(cyanamidonitrato-N:O)bis-(imidazole-N³)copper(II) complex

The experimental crystal charge density of the complex [Cu(iz)₂(can)₂] (I) (where iz = imidazole, can = cyanamidonitrate anion), [Cu(C₃H₄N₂)₂(CN₃O₂)₂], crystallizing in centrosymmetric space group P2₁/c, has been determined at 120.0 (2) K, using Hansen and Coppens' aspherical atom multipole model. The central Cu atom is pseudo-octahedrally coordinated by four N atoms in an equatorial plane [two from iz molecules, 1.9660 (4) Å, two from can anions, 2.0273 (5) Å] and by two O atoms (from two adjacent molecules) in axial positions [2.5566 (5) Å]. The d-orbital population analysis shows that the oxidation state for the copper is +2 with the d⁹ configuration and that there is a hole in the orbital, located in the plane of the four nitrogen-ligating atoms. Electron lone pairs of these four N atoms are pointing into these regions of depleted electron density. In accordance with the medium-length Cu—O axial bonds, the d_z² orbital is almost fully occupied [1.79 (3) electrons]. The non-bonding d_xy orbital is fully occupied [2.05 (3) electrons]. Analysis of the atomic charges does indicate a deficit of +0.35 (4) e⁻ on the nitrile carbon, which provides evidence of β-carbon activation for a possible nucleophilic addition reaction. This reaction has been indirectly confirmed experimentally.

Computing details

Data collection: Stoe & Cie, (1991); cell refinement: Stoe & Cie, (1991); data reduction: Stoe & Cie, (1991); program(s) used to solve structure: Koritsanszky et al., (1995); program(s) used to refine structure: Koritsanszky et al., (1995); molecular graphics: Brandenburg, (1998) & Koritsanszky et al., (1995); software used to prepare material for publication: Koritsanszky et al., (1995).

(AN592)

Crystal data

C8H8CuN10O4	F(000) = 374
Mr = 371.76	Dx = 1.892 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71069 Å
a = 7.1248 (7) Å	Cell parameters from 56 reflections
b = 13.600 (3) Å	θ = 25.5–28.2°
c = 6.7973 (9) Å	µ = 1.64 mm^−1
β = 97.821 (11)°	T = 120 K
V = 652.49 (16) Å^3	Block, green-blue
Z = 2	0.41 × 0.40 × 0.23 mm

Data collection

STOE STADI4 diffractometer	10694 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.016
Graphite monochromator	θmax = 45.0°
ω scans	h = −14→14
Absorption correction: numerical (Stoe & Cie, 1997)	k = −26→24
Tmin = 0.552, Tmax = 0.706	l = −9→13
14953 measured reflections	3 standard reflections every 120 min
5382 independent reflections	intensity decay: none

Refinement

Refinement on F^2	w = 1/[σ^2(Fo^2)]
R[F^2 > 2σ(F^2)] = 0.016	(Δ/σ)max = 0.019
wR(F^2) = 0.017	Δρmax = 0.16 e Å^−3
S = 1.42	Δρmin = −0.18 e Å^−3
10694 reflections	Extinction correction: B-C type 2 Gaussian isotropic
247 parameters	Extinction coefficient: 0.08353
H-atom parameters constrained

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
CU(1)	0.50000	0.50000	0.00000	0.009	0.5000
O(11)	0.31779 (6)	0.52337 (3)	0.65234 (8)	0.016
O(12)	0.09841 (7)	0.61726 (4)	0.74348 (9)	0.024
N(2)	0.40935 (6)	0.36349 (3)	0.00133 (4)	0.011
N(5)	0.22114 (7)	0.23782 (4)	0.02532 (4)	0.015
N(7)	0.29967 (6)	0.54052 (3)	0.16918 (7)	0.013
N(9)	0.11689 (5)	0.60673 (3)	0.42461 (7)	0.014
N(10)	0.18172 (5)	0.58058 (3)	0.61467 (6)	0.012
C(3)	0.51005 (6)	0.27798 (3)	−0.01756 (5)	0.013
C(4)	0.39368 (7)	0.19927 (3)	−0.00279 (5)	0.014
C(6)	0.23547 (6)	0.33623 (3)	0.02686 (5)	0.014
C(8)	0.21996 (5)	0.56851 (3)	0.29626 (6)	0.011
H(3)	0.65739 (6)	0.27985 (3)	−0.03922 (5)	0.037 (2)
H(4)	0.41587 (7)	0.12095 (3)	−0.01238 (5)	0.038 (2)
H(5)	0.10018 (7)	0.20246 (4)	0.04406 (4)	0.029 (3)
H(6)	0.11944 (6)	0.38507 (3)	0.04465 (5)	0.036 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
CU(1)	0.01002 (3)	0.00745 (4)	0.00898 (3)	−0.00065 (3)	0.00431 (3)	−0.00057 (3)
O(11)	0.0163 (1)	0.0181 (1)	0.0132 (2)	0.0063 (1)	0.0011 (1)	0.0011 (1)
O(12)	0.0223 (2)	0.0369 (2)	0.0128 (2)	0.0121 (2)	0.0071 (1)	−0.0018 (1)
N(2)	0.0115 (1)	0.0083 (1)	0.0121 (1)	−0.0014 (1)	0.0043 (1)	−0.0004 (1)
N(5)	0.0157 (2)	0.0132 (2)	0.0155 (2)	−0.0062 (1)	0.0038 (1)	−0.0012 (1)
N(7)	0.0134 (1)	0.0128 (1)	0.0126 (1)	0.0007 (1)	0.0064 (1)	−0.0014 (1)
N(9)	0.0135 (1)	0.0181 (1)	0.0108 (1)	0.0064 (1)	0.0038 (1)	0.0003 (1)
N(10)	0.0114 (1)	0.0155 (1)	0.0099 (1)	0.0029 (1)	0.0034 (1)	0.0000 (1)
C(3)	0.0136 (1)	0.0094 (1)	0.0148 (2)	0.0000 (1)	0.0036 (1)	0.0009 (1)
C(4)	0.0184 (2)	0.0093 (1)	0.0152 (2)	−0.0022 (1)	0.0023 (1)	0.0005 (1)
C(6)	0.0120 (1)	0.0126 (2)	0.0161 (2)	−0.0028 (1)	0.0050 (1)	−0.0019 (1)
C(8)	0.0112 (1)	0.0119 (1)	0.0105 (1)	0.0009 (1)	0.0041 (1)	−0.0007 (1)

Geometric parameters (Å, º)

CU(1)—O(11)^i	2.5566 (5)	N(5)—C(4)	1.3735 (7)
CU(1)—O(11)^ii	2.5566 (5)	N(5)—C(6)	1.3421 (6)
CU(1)—N(2)	1.9660 (4)	N(5)—H(5)	1.010
CU(1)—N(2)^iii	1.9660 (4)	N(7)—C(8)	1.1607 (6)
CU(1)—N(7)	2.0273 (4)	N(9)—N(10)	1.3588 (6)
CU(1)—N(7)^iii	2.0273 (5)	N(9)—C(8)	1.3210 (6)
O(11)—N(10)	1.2422 (6)	C(3)—C(4)	1.3660 (6)
O(12)—N(10)	1.2285 (7)	C(3)—H(3)	1.080
N(2)—C(3)	1.3816 (5)	C(4)—H(4)	1.080
N(2)—C(6)	1.3270 (5)	C(6)—H(6)	1.080
O(11)^i—CU(1)—O(11)^ii	180.0	O(11)—N(10)—N(9)	121.0 (1)
O(11)^i—CU(1)—N(2)	89.8 (1)	O(12)—N(10)—N(9)	115.9 (1)
O(11)^i—CU(1)—N(7)	100.5 (1)	N(2)—C(3)—C(4)	108.9 (1)
N(2)—CU(1)—N(7)	89.8 (1)	N(2)—C(3)—H(3)	121.3 (1)
CU(1)^iv—O(11)—N(10)	123.5 (1)	C(4)—C(3)—H(3)	129.7 (1)
CU(1)—N(2)—C(3)	128.3 (1)	N(5)—C(4)—C(3)	105.9 (1)
CU(1)—N(2)—C(6)	125.3 (1)	N(5)—C(4)—H(4)	121.7 (1)
C(3)—N(2)—C(6)	106.4 (1)	C(3)—C(4)—H(5)	127.2 (1)
C(4)—N(5)—C(6)	108.3 (1)	N(2)—C(6)—N(5)	110.4 (1)
C(4)—N(5)—H(5)	129.1 (1)	N(2)—C(6)—H(6)	125.8 (1)
C(6)—N(5)—H(5)	122.6 (1)	N(5)—C(6)—H(6)	123.8 (1)
CU(1)—N(7)—C(8)	164.8 (1)	N(7)—C(8)—N(9)	173.2 (1)
N(10)—N(9)—C(8)	112.2 (1)

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