Triaqua­(1,4,7-triaza­cyclo­nonane-κ³N¹,N⁴,N⁷)nickel(II) bromide nitrate

In the title half-sandwich compound, [Ni(C₆H₁₅N₃)(H₂O)₃]Br(NO₃), the central Ni^II ion, lying on a threefold rotation axis, is six-coordinated by three amine N atoms from the face-capping triaza macrocycle and three water O atoms in a slightly distorted octa­hedral geometry. In the crystal, O—H...O hydrogen bonding and weak O—H...Br inter­actions associate the Ni^II cations and the counter-ions into a three-dimensional supra­molecular network.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.035
• wR factor = 0.072
• Data-to-parameter ratio = 142.9

checkCIF/PLATON results

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Alert level C
PLAT420_ALERT_2_C D-H Without Acceptor       N1     -   H3     ...          ?
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.39
           From the CIF: _reflns_number_total               1110
           Count of symmetry unique reflns          633
           Completeness (_total/calc)            175.36%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       477
           Fraction of Friedel pairs measured     0.754
           Are heavy atom types Z>Si present        yes
PLAT764_ALERT_4_G Overcomplete CIF Bond List Detected (Rep/Expd) .       1.30 Ratio

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The coordination chemistry of 1,4,7–triazacyclononane (TACN) has been extensively studied for its applications in the simulation of metalloenzymes and metalloproteins (Chaudhury et al., 1985; Deal et al., 1996; Hegg & Burstyn, 1995; Hegg et al., 1997; Lin et al., 2001; Williams et al., 1999) as well as in constructing molecule–based magnetic materials (Berseth et al., 2000; Cheng et al., 2004; Poganiuch et al., 1991). In general, TACN ligand can form stable sandwich complexes with many transition metals (Stranger et al., 1992; Zompa & Margulis, 1978) or functions as a terminal chelator for the assembly of binuclear/polynuclear species and coordination polymers supported by bridging ligands (Bencini et al., 1990; Wang et al., 2005; Wang et al., 2003). In this paper, a half–sandwich type Ni^II complex with TACN has been synthesized and characterized.

In the selected crystal, the title compound (I) crystallizes in a chiral space group P2₁3 and Flack parameter of 0.01 (3) indicates that a spontaneous resolution has been achieved during crystallization. As depicted in Fig. 1, the Ni^II center in the complex cation lies on a three–fold rotation axis and three amine N atoms from facially coordinated TACN and three water molecules complete the slightly distorted octahedral arrangement. Upon coordination, three five–membered Ni—N—C—C—N chelating rings subtended at metal center adopt (λλλ) conformation, which is the source of the chirality of the crystal. Ni—N [2.091 (3) Å] and Ni—O [2.089 (3) Å] bond lengths are both in the normal ranges, meanwhile N—Ni—N bond angle is smaller than that of O—Ni—O due to the small size of TACN ring. Counter–ions NO₃^- and Br^- interconnect neighbouring cations by O—H···O hydrogen bond and O—H···Br^- weak interaction (Table 1) into three–dimensional supramolecular network (Fig. 2).

Related literature

For the preparation of 1,4,7-triazacyclononane trihydrobromide, see: Koyama & Yoshino (1972). For the applications of metal complexes containing 1,4,7-triazacyclononane as small-molecule models of metalloenzymes and metalloproteins and as molecule-based magnets, see: Berseth et al. (2000); Chaudhury et al. (1985); Cheng et al. (2004); Deal et al. (1996); Hegg & Burstyn (1995); Hegg et al. (1997); Lin et al. (2001); Poganiuch et al. (1991); Williams et al. (1999). For related Ni^II complexes with 1,4,7-triazacyclononane, see: Bencini et al. (1990); Stranger et al. (1992); Wang et al. (2003, 2005); Zompa & Margulis (1978).

S2. Experimental

1,4,7–Triazacyclononane trihydrobromide (TACN^.3HBr) was prepared by following a modified published method (Koyama & Yoshino, 1972).

To a solution of 0.074 g (0.02 mmol) of TACN^.3HBr in water (10 ml), 0.1 M NaOH was added to adjust the pH to 6. Then aqueous solution (5 ml) of 0.058 g (0.02 mmol) of Ni(NO₃)₂^.6H₂0 was added and the resulting mixture was stirred under reflux for 6 h. After cooling, the mixture was filtered, and the filtrate was allowed to standing at ambient temperature. Plate–like green single crystals suitable for X–ray crystallographic analysis were collected by slow evaporation of the filtrate within two months.

S3. Refinement

All methylene H atoms were placed at calculated positions and refined as riding on their parent atoms [C—H = 0.97 Å and U_iso(H) = 1.2 U_eq(C)]. The H atoms of amine groups and water molecules were located in a difference Fourier map as riding atoms, with U_iso(H) = 1.5 U_eq(N) and 1.5 U_eq(O).

Computing details

Data collection: APEX2 (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. An ORTEP plot for the title compound (I) with the atom labelling scheme and 30% displacement ellipsoids. Symmetry codes: (i) y+1/2, -z+3/2, -x+2; (ii) -z+2, x-1/2, -y+3/2.
	Fig. 2. A view of the packing diagram of the title compound (I), showing the hydrogen–bonding supramolecular network. Hydrogen bonds are drawn in dashed lines. H atoms not involved in hydrogen bonds are omitted for clarity.

Triaqua(1,4,7-triazacyclononane- κ³N¹,N⁴,N⁷)nickel(II) bromide nitrate

Crystal data

[Ni(C6H15N3)(H2O)3]Br(NO3)	Dx = 1.767 Mg m^−3
Mr = 383.89	Mo Kα radiation, λ = 0.71073 Å
Cubic, P213	Cell parameters from 13409 reflections
Hall symbol: P 2ac 2ab 3	θ = 3.1–27.4°
a = 11.300 (1) Å	µ = 4.14 mm^−1
V = 1442.9 (3) Å^3	T = 298 K
Z = 4	Plate, green
F(000) = 784	0.29 × 0.27 × 0.18 mm

Data collection

Bruker APEXII CCD area-detector diffractometer	1110 independent reflections
Radiation source: fine-focus sealed tube	985 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.080
φ and ω scans	θmax = 27.4°, θmin = 3.1°
Absorption correction: multi-scan (SADABS; Bruker, 1998)	h = −14→14
Tmin = 0.320, Tmax = 0.480	k = −14→14
15223 measured reflections	l = −14→14

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)] = 0.035	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.072	w = 1/[σ^2(Fo^2) + (0.0232P)^2 + 1.6516P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max < 0.001
8717 reflections	Δρmax = 0.36 e Å^−3
61 parameters	Δρmin = −0.47 e Å^−3
0 restraints	Absolute structure: Flack (1983), 475 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.01 (3)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
Ni1	1.06169 (4)	0.56169 (4)	0.93831 (4)	0.02729 (19)
Br1	0.25347 (4)	0.24653 (4)	0.75347 (4)	0.0437 (2)
C1	0.8566 (4)	0.4233 (4)	0.8872 (4)	0.0437 (11)
H1A	0.8123	0.3498	0.8858	0.052*
H1B	0.8438	0.4636	0.8125	0.052*
C2	1.0118 (4)	0.3128 (4)	0.9995 (4)	0.0449 (11)
H2A	1.0326	0.2365	0.9660	0.054*
H2B	0.9417	0.3022	1.0478	0.054*
N1	0.9850 (3)	0.3973 (3)	0.9019 (3)	0.0353 (8)
H3	1.0226	0.3631	0.8407	0.053*
N2	0.9466 (3)	0.9466 (3)	0.9466 (3)	0.0316 (11)
O1	1.0196 (3)	0.6447 (3)	0.7786 (3)	0.0391 (8)
O2	0.8854 (3)	1.0345 (3)	0.9196 (3)	0.0577 (9)
H4B	0.947 (5)	0.659 (4)	0.765 (4)	0.050 (14)*
H4A	1.040 (4)	0.598 (4)	0.723 (4)	0.050 (14)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.02729 (19)	0.02729 (19)	0.02729 (19)	−0.0011 (2)	0.0011 (2)	0.0011 (2)
Br1	0.0437 (2)	0.0437 (2)	0.0437 (2)	−0.0012 (2)	0.0012 (2)	−0.0012 (2)
C1	0.041 (2)	0.042 (3)	0.049 (3)	−0.016 (2)	−0.009 (2)	0.005 (2)
C2	0.054 (3)	0.027 (2)	0.054 (3)	−0.0022 (19)	0.010 (2)	0.0063 (19)
N1	0.0365 (19)	0.0349 (19)	0.0346 (19)	−0.0022 (14)	0.0050 (14)	−0.0021 (14)
N2	0.0316 (11)	0.0316 (11)	0.0316 (11)	0.0002 (15)	0.0002 (15)	0.0002 (15)
O1	0.0424 (18)	0.0419 (18)	0.0330 (18)	0.0052 (14)	−0.0007 (13)	0.0024 (12)
O2	0.055 (2)	0.054 (2)	0.065 (2)	0.0156 (16)	0.0149 (17)	0.0133 (18)

Geometric parameters (Å, º)

Ni1—O1^i	2.089 (3)	C2—N1	1.490 (5)
Ni1—O1	2.089 (3)	C2—C1^ii	1.520 (6)
Ni1—O1^ii	2.089 (3)	C2—H2A	0.9700
Ni1—N1	2.091 (3)	C2—H2B	0.9700
Ni1—N1^ii	2.091 (3)	N1—H3	0.8987
Ni1—N1^i	2.091 (3)	N2—O2^iii	1.248 (3)
C1—N1	1.490 (6)	N2—O2^iv	1.248 (3)
C1—C2^i	1.520 (6)	N2—O2	1.248 (3)
C1—H1A	0.9700	O1—H4B	0.85 (5)
C1—H1B	0.9700	O1—H4A	0.84 (4)
O1^i—Ni1—O1	84.90 (14)	H1A—C1—H1B	108.1
O1^i—Ni1—O1^ii	84.90 (14)	N1—C2—C1^ii	111.7 (3)
O1—Ni1—O1^ii	84.90 (14)	N1—C2—H2A	109.3
O1^i—Ni1—N1	177.00 (13)	C1^ii—C2—H2A	109.3
O1—Ni1—N1	97.72 (13)	N1—C2—H2B	109.3
O1^ii—Ni1—N1	93.87 (12)	C1^ii—C2—H2B	109.3
O1^i—Ni1—N1^ii	93.87 (12)	H2A—C2—H2B	108.0
O1—Ni1—N1^ii	177.00 (13)	C1—N1—C2	114.0 (3)
O1^ii—Ni1—N1^ii	97.72 (12)	C1—N1—Ni1	104.5 (3)
N1—Ni1—N1^ii	83.58 (14)	C2—N1—Ni1	109.8 (3)
O1^i—Ni1—N1^i	97.72 (12)	C1—N1—H3	117.3
O1—Ni1—N1^i	93.87 (12)	C2—N1—H3	101.4
O1^ii—Ni1—N1^i	177.00 (13)	Ni1—N1—H3	109.7
N1—Ni1—N1^i	83.58 (14)	O2^iii—N2—O2^iv	119.999 (2)
N1^ii—Ni1—N1^i	83.58 (14)	O2^iii—N2—O2	120.000 (3)
N1—C1—C2^i	110.3 (4)	O2^iv—N2—O2	120.000 (2)
N1—C1—H1A	109.6	Ni1—O1—H4B	117 (4)
C2^i—C1—H1A	109.6	Ni1—O1—H4A	107 (4)
N1—C1—H1B	109.6	H4B—O1—H4A	104 (5)
C2^i—C1—H1B	109.6
C2^i—C1—N1—C2	72.1 (5)	N1^ii—Ni1—N1—C1	114.6 (2)
C2^i—C1—N1—Ni1	−47.8 (4)	N1^i—Ni1—N1—C1	30.4 (3)
C1^ii—C2—N1—C1	−133.2 (4)	O1—Ni1—N1—C2	174.6 (3)
C1^ii—C2—N1—Ni1	−16.3 (4)	O1^ii—Ni1—N1—C2	89.3 (3)
O1—Ni1—N1—C1	−62.7 (3)	N1^ii—Ni1—N1—C2	−8.1 (3)
O1^ii—Ni1—N1—C1	−148.0 (3)	N1^i—Ni1—N1—C2	−92.3 (2)

Symmetry codes: (i) y+1/2, −z+3/2, −x+2; (ii) −z+2, x−1/2, −y+3/2; (iii) z, x, y; (iv) y, z, x.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H4A···O2^v	0.84 (4)	1.95 (5)	2.776 (5)	162 (4)
O1—H4B···Br1^vi	0.85 (5)	2.48 (5)	3.312 (3)	167 (4)

Symmetry codes: (v) −x+2, y−1/2, −z+3/2; (vi) −x+1, y+1/2, −z+3/2.