Tris(1,2-diamino­ethane)­nickel(II) hexa­fluoridosilicate

The ionic title complex, [Ni(C₂H₈N₂)₃](SiF₆), is built up of [Ni(en)₃]²⁺ complex cations (en = 1,2-diamino­ethane) and hexa­fluoridosilicate anions. Single crystals of the title complex were isolated from an aqueous–ethano­lic Ni²⁺–en–SiF₆²⁻ system. The Ni(II) and Si atoms are each located on a special position with site symmetry 3.2. The Ni(II) atom coordination sphere is octa­hedrally deformed, being coordinated by three chelating diamine ligands with an Ni—N distance of 2.1233 (18) Å. The crystal packing of the respective ions corresponds to the structure type of the hexa­gonal form of BN. Beside ionic forces, the packing is governed by N—H...F hydrogen bonds, which lead to the formation of hydro­phobic channels running along the 6₃ screw axis. The structure was refined as an inversion twin [0.49 (3): 0.51 (3)].

Key indicators

• Single-crystal X-ray study
• T = 291 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.027
• wR factor = 0.064
• Data-to-parameter ratio = 16.8

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for    Si1    --  F1      ..       8.80 su

Alert level C
STRVA01_ALERT_4_C           Flack test results are ambiguous.
           From the CIF: _refine_ls_abs_structure_Flack    0.490
           From the CIF: _refine_ls_abs_structure_Flack_su    0.030
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       3.52
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Ni1    --  N1      ..       6.87 su
PLAT033_ALERT_4_C Flack x Parameter Value Deviates from Zero .....       0.49

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           27.43
           From the CIF: _reflns_number_total                554
           Count of symmetry unique reflns          369
           Completeness (_total/calc)            150.14%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       185
           Fraction of Friedel pairs measured     0.501
           Are heavy atom types Z>Si present        yes

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

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

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S1. Comment

The crystal structure of the title complex is ionic and is built up of [Ni(en)₃]²⁺ complex cations and SiF₆^2- anions, as shown in Fig. 1. The Ni^II atom (site symmetry 32) in the [Ni(en)₃]²⁺ complex cation has a slightly deformed octahedral coordination sphere, being coordinated by six nitrogen atoms from three chelate bonded en ligands.

As the studied single-crystal was an inversion twin [ratio of the two domains was 0.49 (3):0.51 (3)] both Λδδδ and Δλλλ configurations were present in the crystal. In the isostructural [Zn(en))₃]SiF₆ complex the cations exhibit Λδδδ absolute configuration (Li et al., 2009). The Ni—N bond lengths of 2.1234 (18) Å (6 ×) corresponds well to the value of 2.1318 (2) Å found in the analogous hexafluoridogermanate complex [Ni(en)₃]GeF₆ (Pan et al., 2005). The positive charge of the complex cation is compensated for by the non-coordinated SiF₆^2- anion, that exhibits almost ideal octahedral symmetry. The Si atom is located on the 3-fold axis (site symmetry 32). The Si—F bond length of 1.681 (2) Å (6 ×) is in line with the value of 1.6942 (15) Å found in [Zn(en)₃]SiF₆ (Li et al., 2009).

In the crystal the packing of the respective ions corresponds to the hexagonal structure of BN, with a Ni···Si distance of 5.2927 (4) Å within the hexagonal plane and a Ni···Si distance of 4.8815 (5) Å between the planes (Fig. 2). To the packing forces contribute also N—H···F type hydrogen bonds with N···F distances in the range 3.137 (2) - 3.235 (2) Å (Table 1, Fig. 3). Some of the hydrogen bonds are three-centered with two fluorido acceptors. The observed geometric parameters associated with the hydrogen bonds correspond to those in Zn(en))₃]SiF₆ (Li et al., 2009) where the N···F distances range from 3.113 (3) - 3.239 (3) Å. The hydrogen bonding leads to the formation of hydrophobic channels running along the 6₃ screw axis (Fig. 4a and 4 b), as was already observed in the GeF₆ analog (Pan et al., 2005).

Related literature

For the hexafluoridosilicate anion acting as simple counter-ion, see: Li et al. (2009). For two nickel(II) complexes containing the hexafluoridosilicate anion as counter-ion, see: Spek et al. (1988); Wu et al. (2008). For complexes containing the [Ni(en)₃]²⁺ complex cation and hexafluorido-type anions, see: Pan et al. (2005); Ribas et al. (1998); James et al. (1998); Contakes et al. (2000).

S2. Experimental

To a solution of 0.24 g of NiCl₂.6H₂O (1 mmol) in 10 cm³ of water:ethanol mixture (1:1 in vol) wre added successively 0.27 cm³ of 1,2-diaminoethane (en) (4 mmol) and 0.18 g of (NH₄)SiF₆ (1 mmol), dissolved in 10 cm³ of water:ethanol mixture (1:1 / v:v), under constant stirring. The dark pink solution that formed was filtered and left aside for crystallization at RT. Within a few days light-pink prisms were formed. They were collected by filtration and subsequently recrystallized from a water:ethanol mixture to give crystals suitable for X-ray diffraction analysis. Anal. [% '[%' %]], calculated for Ni₁C₆N₆H₂₄Si₁F₆: C, 18.92; H, 6.35; N, 22.05. Found: C, 18.97; H, 5.76; N, 14.55. IR (KBr pellets, FT—IR Avatar 330 (ThermoNicolet), cm^-1): 3300m; 3170m; 2954m; 2925m; 2887m; 1598 s; 1456 s; 1385w; 1370w; 1125 s; 1064 s, 717 s; 500 s; 478m. Thermal Analysis (TA Instrument, air atmosphere): the complex was thermally stable up to 501 K and decomposed in one step in the temperature range 501 - 693 K.

S3. Refinement

The structure was refined as an inversion twin [0.49 (3): 0.51 (3)]. All the H atoms were included in calculated positions and treated as riding atoms: N—H = 0.90 Å, C—H = 0.97 Å, with U_iso(H) = 1.2U_eq(parent N– or C-atom).

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Crystal Impact, 2007); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. Molecular structure of the title ionic complex along with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Packing of the ions in the title complex leading to the hexagonal BN structure type.
	Fig. 3. Detailed view of the hydrogen bonding scheme (dashed lines) in the title complex. For the sake of clarity only the NH2 groups of the en ligands are shown. Symmetry codes: (i) = y, x, -z; (ii) = 1 - x, 1 - x + y, z; (iii) = 1 - x + y, 1 - x, z.
	Fig. 4. Formation of hydrophobic pseudo-channels inside the hydrogen bonded complex cations and anions running along the 63 screw axis: view of one channel. Hydrogen atoms bonded to the carbon atoms are omitted for the sake of clarity.
	Fig. 5. Formation of hydrophobic pseudo-channels inside the hydrogen bonded complex cations and anions running along the 63 screw axis: arrangement of the neighbouring channels. Hydrogen atoms bonded to the carbon atoms are omitted for the sake of clarity.

Tris(1,2-diaminoethane)nickel(II) hexafluoridosilicate

Crystal data

[Ni(C2H8N2)3](SiF6)	Dx = 1.781 Mg m^−3
Mr = 381.11	Mo Kα radiation, λ = 0.71069 Å
Hexagonal, P6322	Cell parameters from 8628 reflections
Hall symbol: P 6c 2c	θ = 2.6–27.4°
a = 9.1670 (9) Å	µ = 1.52 mm^−1
c = 9.763 (1) Å	T = 291 K
V = 710.51 (12) Å^3	Prism, pink
Z = 2	0.42 × 0.21 × 0.15 mm
F(000) = 396

Data collection

Oxford Diffraction Xcalibur diffractometer with Sapphire2 detector	554 independent reflections
Radiation source: fine-focus sealed tube	489 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.050
Detector resolution: 8.3438 pixels mm^-1	θmax = 27.4°, θmin = 2.6°
ω scans	h = −11→11
Absorption correction: numerical [Clark & Reid (1995) in CrysAlis PRO (Oxford Diffraction, 2009)]	k = −11→11
Tmin = 0.834, Tmax = 0.859	l = −12→12
8628 measured reflections

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)] = 0.027	H-atom parameters constrained
wR(F^2) = 0.064	w = 1/[σ^2(Fo^2) + (0.0413P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
554 reflections	Δρmax = 0.68 e Å^−3
33 parameters	Δρmin = −0.19 e Å^−3
0 restraints	Absolute structure: Flack (1983), 89 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.49 (3)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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	0.3333	0.6667	0.2500	0.02783 (19)
N1	0.3156 (2)	0.4642 (2)	0.13146 (17)	0.0368 (4)
H1	0.3098	0.4839	0.0419	0.044*
H2	0.4076	0.4547	0.1449	0.044*
C1	0.1634 (3)	0.3071 (2)	0.1729 (2)	0.0432 (5)
H5	0.1732	0.2107	0.1455	0.052*
H6	0.0651	0.2992	0.1284	0.052*
Si1	0.6667	0.3333	0.2500	0.0267 (3)
F1	0.51790 (19)	0.18375 (19)	0.14983 (14)	0.0550 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0286 (2)	0.0286 (2)	0.0262 (3)	0.01432 (11)	0.000	0.000
N1	0.0401 (10)	0.0429 (11)	0.0319 (9)	0.0241 (9)	0.0020 (8)	−0.0013 (8)
C1	0.0428 (16)	0.0339 (10)	0.0489 (12)	0.0162 (13)	−0.0016 (11)	−0.0079 (8)
Si1	0.0270 (3)	0.0270 (3)	0.0262 (5)	0.01349 (17)	0.000	0.000
F1	0.0521 (8)	0.0495 (8)	0.0489 (8)	0.0145 (6)	−0.0110 (7)	−0.0086 (7)

Geometric parameters (Å, º)

Ni1—N1^i	2.1233 (18)	C1—C1^iv	1.515 (4)
Ni1—N1^ii	2.1233 (18)	C1—H5	0.9700
Ni1—N1^iii	2.1233 (18)	C1—H6	0.9700
Ni1—N1^iv	2.1233 (18)	Si1—F1^vi	1.6812 (14)
Ni1—N1	2.1233 (18)	Si1—F1^vii	1.6812 (14)
Ni1—N1^v	2.1233 (18)	Si1—F1	1.6812 (14)
N1—C1	1.475 (2)	Si1—F1^v	1.6812 (14)
N1—H1	0.9000	Si1—F1^viii	1.6812 (14)
N1—H2	0.9000	Si1—F1^ix	1.6812 (14)
N1^i—Ni1—N1^ii	81.62 (9)	N1—C1—C1^iv	109.08 (16)
N1^i—Ni1—N1^iii	93.12 (7)	N1—C1—H5	109.9
N1^ii—Ni1—N1^iii	92.62 (10)	C1^iv—C1—H5	109.9
N1^i—Ni1—N1^iv	92.62 (10)	N1—C1—H6	109.9
N1^ii—Ni1—N1^iv	93.12 (7)	C1^iv—C1—H6	109.9
N1^iii—Ni1—N1^iv	172.42 (9)	H5—C1—H6	108.3
N1^i—Ni1—N1	93.12 (7)	F1^vi—Si1—F1^vii	90.75 (10)
N1^ii—Ni1—N1	172.42 (9)	F1^vi—Si1—F1	90.12 (10)
N1^iii—Ni1—N1	93.12 (6)	F1^vii—Si1—F1	89.57 (7)
N1^iv—Ni1—N1	81.62 (9)	F1^vi—Si1—F1^v	89.57 (7)
N1^i—Ni1—N1^v	172.42 (9)	F1^vii—Si1—F1^v	90.12 (10)
N1^ii—Ni1—N1^v	93.12 (7)	F1—Si1—F1^v	179.56 (10)
N1^iii—Ni1—N1^v	81.62 (9)	F1^vi—Si1—F1^viii	89.57 (7)
N1^iv—Ni1—N1^v	93.12 (6)	F1^vii—Si1—F1^viii	179.56 (10)
N1—Ni1—N1^v	92.62 (10)	F1—Si1—F1^viii	90.75 (10)
C1—N1—Ni1	108.97 (13)	F1^v—Si1—F1^viii	89.57 (7)
C1—N1—H1	109.9	F1^vi—Si1—F1^ix	179.56 (10)
Ni1—N1—H1	109.9	F1^vii—Si1—F1^ix	89.57 (7)
C1—N1—H2	109.9	F1—Si1—F1^ix	89.57 (7)
Ni1—N1—H2	109.9	F1^v—Si1—F1^ix	90.75 (10)
H1—N1—H2	108.3	F1^viii—Si1—F1^ix	90.12 (10)
N1^i—Ni1—N1—C1	−78.08 (18)	N1^v—Ni1—N1—C1	106.88 (16)
N1^iii—Ni1—N1—C1	−171.38 (15)	Ni1—N1—C1—C1^iv	−39.4 (3)
N1^iv—Ni1—N1—C1	14.11 (12)

Symmetry codes: (i) −x+y, −x+1, z; (ii) x, x−y+1, −z+1/2; (iii) −y+1, x−y+1, z; (iv) −x+y, y, −z+1/2; (v) −y+1, −x+1, −z+1/2; (vi) −x+y+1, y, −z+1/2; (vii) −y+1, x−y, z; (viii) x, x−y, −z+1/2; (ix) −x+y+1, −x+1, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···F1^x	0.90	2.30	3.137 (2)	154
N1—H1···F1^xi	0.90	2.48	3.235 (2)	142
N1—H2···F1^ix	0.90	2.25	3.137 (2)	167

Symmetry codes: (ix) −x+y+1, −x+1, z; (x) y, x, −z; (xi) −x+1, −x+y+1, −z.