Crystal structure of (N¹-benzyl-N¹,N²,N²-tri­methyl­ethane-1,2-di­amine-κ²N,N′)di­chloridomercury(II)

The mol­ecular structure of [HgCl₂(C₁₂H₂₀N₂)] is a rare example where the Hg^II atom is bound to a Cl₂N₂ donor set for which the N atoms originate from aliphatic tertiary amine groups.

Key indicators

• Single-crystal X-ray study
• T = 200 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.044
• wR factor = 0.074
• Data-to-parameter ratio = 32.4

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT910_ALERT_3_B Missing # of FCF Reflections Below Th(Min) .....         23 Report

Alert level C
PLAT342_ALERT_3_C Low Bond Precision on  C-C Bonds ...............     0.0084 Ang.
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      2.397 Check
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          5 Report
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....          4 Note
PLAT973_ALERT_2_C Check Calcd Positive Residual Density on      Hg       1.04 eA-3

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF     Please Do !
PLAT063_ALERT_4_G Crystal Size Likely too Large for Beam Size ....       0.79 mm
PLAT793_ALERT_4_G The Model has Chirality at N1      .............          S Verify
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600        483 Note

   0 ALERT level A = Most likely a serious problem - resolve or explain
   1 ALERT level B = A potentially serious problem, consider carefully
   5 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   4 ALERT level G = General information/check it is not something unexpected

   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
   5 ALERT type 3 Indicator that the structure quality may be low
   3 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Chemical context

The chemistry of mercuric compounds with multidentate amine ligands is of inter­est due to the low coordination number and geometry preferences of Hg^II, which facilitates extraordinarily rapid exchange of simple ligands (Bebout et al., 2013; Carra et al., 2013). The enhanced binding thermodynamics of these multidentate ligands has been used to suppress inter­molecular ligand-exchange rates for a variety of Hg^II complexes in solution, greatly enhancing the meaningfulness of NMR characterization. Significantly, under conditions of slow inter­molecular exchange the rates of intra­molecular isomerization processes for Hg^II can still exceed both the chemical shift and coupling constant time scale, particularly when bond cleavage is unnecessary and structures of these complexes have been determined (Bebout et al., 2013; Carra et al., 2013).

In view of this inter­est in the coordination chemistry of mercury with multidentate amine ligands, and the lack of such structures involving tertiary amine donors, we report here the structure of the HgCl₂ adduct of N¹-benzyl-N¹,N²,N²-tri­methyl­ethane-1,2-di­amine. The o-di­amine-substituted aryl bromide, N¹-(2-bromo­benzyl)-N¹,N²,N²-tri­methyl­ethane-1,2-di­amine, can be prepared by the reaction of N¹,N¹,N²-tri­methyl­ethane-1,2-di­amine and ortho-bromo­benzyl bromide. The ligand is moisture sensitive and is difficult to purify by column chromatography. However, it could easily be purified by vacuum distillation. The moisture-sensitive ligand, when treated with n-BuLi in tetra­hydro­furan (THF) and mercuric chloride, afforded the title compound, [HgCl₂(C₁₂H₂₀N₂)], (3) (Fig. 1).

S2. Structural commentary

In the structure of (3), the Hg^II atom is four-coordinated by two tertiary amine N-atom donors, as well as two Cl^- anions to give a distorted tetra­hedral coordination environment (Fig. 2). The distortion from ideal values can be seen by the dihedral angle between the N1—Hg—N2 and Cl1—Hg—Cl2 planes of 82.80 (9)°. The Hg—N and Hg—Cl bond lengths are in the normal ranges for such bonds (Allen, 2002). The five-membered chelate ring adopts an envelope conformation with puckering parameters of Q(2) = 0.446 (6)Å and ϕ(2) = 88.8 (6)° (Cremer & Pople, 1975), with the two amine CH₃ substituents on opposite sides of the ring. Of the two reported structures which contain Hg^II attached to tertiary N donors (Choi et al., 2005; Niu et al., 2004), only one has Hg^II in an N₂Cl₂ coordination environment (Choi et al., 2005) and thus provides the best comparison. The Hg—Cl [2.3875 (14) and 2.4397 (13) Å] and Hg—N bond lengths [2.355 (4) and 2.411 (4) Å] in (3) agree well with those found in the previous example [Hg—Cl = 2.397 (3) and 2.374 (2) Å; Hg—N = 2.353 (7) and 2.391 (6) Å].

S3. Supra­molecular features

The molecular adducts are linked by C—H···Cl inter­actions (Table 1 and Fig. 3) into a zigzag chain parallel to [101]. As a result of the bulky nature of the complex, with the two amine CH₃ substituents on opposite sides of the chelate ring, there is no evidence of any π–π inter­actions.

S4. Database survey

In view of the inter­est in the coordination chemistry of mercury, it is surprising that a search of the Cambridge Structural Database (Version 5.35, November 2013 with one update; Allen, 2002) for structures of Hg^II with an N₂Cl₂ coordination sphere gave 96 hits, but the vast majority of these involved aromatic N donors such as pyridine and imidazole. There were only six hits involving aliphatic amine N-atom donors and only two (Choi et al., 2005; Niu et al., 2004) where the N atoms involved were both from tertiary amine functionalities.

S5. Synthesis and crystallization

A stirred solution of N¹-(2-bromo­benzyl)-N¹,N²,N²-tri­methyl­ethane-1,2-di­amine, (1), (1.10 ml, 5.34 mmol) in dry THF (15 ml) was treated dropwise with a 1.6 M solution of n-BuLi in hexane (3.80 ml, 6.15 mmol) via syringe under N₂ at 273 K. On stirring the reaction mixture for 2 h at this temperature, the li­thia­ted product (2) was obtained. Mercuric chloride (1.55 g, 5.70 mmol) was added to the reaction mixture under a brisk flow of N₂ gas and stirring was continued for an additional 6 h at room temperature. The reaction mixture was then removed from the N₂ line and evaporated to dryness to give a colourless hygroscopic solid. The solid was extracted with dry chloro­form. The organic phase was separated, dried over Na₂SO₄, and filtered. The filtrate was evaporated to dryness to give a colourless crystalline solid of the HgCl₂ adduct of N¹-benzyl-N¹,N²,N²-tri­methyl­ethane-1,2-di­amine, (3) (yield 1.25 g, 51%). The reaction scheme is shown in Fig. 1.

S6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances of 0.95 (aromatic) and 0.99 Å (methyl­ene), with U_iso(H) = 1.2U_eq(C), and C—H = 0.98 Å for methyl H atoms, with U_iso(H) = 1.5U_eq(C).

Related literature

For related literature, see: Allen (2002); Bebout et al. (2013); Carra et al. (2013); Choi et al. (2005); Cremer & Pople (1975); Niu et al. (2004).

Computing details

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); 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: WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).

Figures

	Fig. 1. Reaction scheme showing the synthesis of the title compound.
	Fig. 2. The molecular structure of [HgCl2(C12H20N2)], showing the atom labelling and displacement ellipsoids at the 30% probability level.
	Fig. 3. The molecular packing for [HgCl2(C12H20N2)] viewed along the c axis. C—H···Cl interactions are shown as dashed lines.

(N¹-Benzyl-N¹,N²,N²-trimethylethane-1,2-diamine-κ²N,N')dichloridomercury(II)

Crystal data

[HgCl2(C12H20N2)]	F(000) = 880
Mr = 463.79	Dx = 1.991 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1518 reflections
a = 9.0839 (3) Å	θ = 5.3–30.8°
b = 15.5367 (6) Å	µ = 10.27 mm^−1
c = 11.3161 (5) Å	T = 200 K
β = 104.324 (4)°	Plate, colorless
V = 1547.43 (10) Å^3	0.79 × 0.23 × 0.05 mm
Z = 4

Data collection

Agilent Xcalibur diffractometer	5125 independent reflections
Radiation source: fine-focus sealed tube	3248 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.067
Detector resolution: 10.5081 pixels mm^-1	θmax = 32.6°, θmin = 5.1°
ω scans	h = −13→11
Absorption correction: analytical [CrysAlis PRO (Agilent, 2014) using a multi-faceted crystal model based on expressions derived by Clark & Reid (1995)]	k = −16→23
Tmin = 0.026, Tmax = 0.339	l = −16→16
13173 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)] = 0.044	H-atom parameters constrained
wR(F^2) = 0.074	w = 1/[σ^2(Fo^2) + (0.0132P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.96	(Δ/σ)max = 0.001
5125 reflections	Δρmax = 1.54 e Å^−3
158 parameters	Δρmin = −1.61 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00248 (16)

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
Hg	0.11248 (2)	0.279066 (14)	0.55937 (2)	0.03718 (9)
Cl1	0.24245 (15)	0.15445 (9)	0.51432 (13)	0.0476 (4)
Cl2	−0.08589 (15)	0.34782 (10)	0.40263 (13)	0.0502 (4)
N1	0.0504 (5)	0.3190 (3)	0.7420 (4)	0.0402 (11)
N2	0.2991 (5)	0.3891 (3)	0.6352 (4)	0.0423 (11)
C1	−0.0894 (5)	0.1816 (4)	0.7510 (5)	0.0368 (13)
C2	−0.0412 (6)	0.1163 (4)	0.6876 (5)	0.0431 (14)
H2A	0.0635	0.1125	0.6885	0.052*
C3	−0.1412 (7)	0.0563 (4)	0.6228 (5)	0.0511 (16)
H3A	−0.1059	0.0123	0.5784	0.061*
C4	−0.2928 (7)	0.0605 (4)	0.6231 (5)	0.0531 (16)
H4A	−0.3624	0.0194	0.5788	0.064*
C5	−0.3428 (6)	0.1239 (4)	0.6871 (6)	0.0552 (17)
H5A	−0.4470	0.1263	0.6879	0.066*
C6	−0.2417 (6)	0.1853 (4)	0.7516 (5)	0.0481 (15)
H6A	−0.2773	0.2294	0.7957	0.058*
C7	0.0218 (6)	0.2459 (4)	0.8187 (5)	0.0455 (14)
H7A	0.1193	0.2163	0.8541	0.055*
H7B	−0.0163	0.2691	0.8870	0.055*
C8	0.1829 (7)	0.3687 (4)	0.8088 (6)	0.0572 (18)
H8A	0.2647	0.3280	0.8471	0.069*
H8B	0.1540	0.4009	0.8752	0.069*
C9	0.2449 (7)	0.4314 (4)	0.7321 (6)	0.0574 (17)
H9A	0.1644	0.4732	0.6950	0.069*
H9B	0.3298	0.4638	0.7852	0.069*
C10	0.3076 (7)	0.4511 (4)	0.5401 (6)	0.0597 (18)
H10A	0.3811	0.4962	0.5747	0.090*
H10B	0.2074	0.4770	0.5077	0.090*
H10C	0.3401	0.4216	0.4743	0.090*
C11	0.4498 (6)	0.3478 (4)	0.6837 (7)	0.064 (2)
H11A	0.5219	0.3906	0.7281	0.095*
H11B	0.4871	0.3247	0.6158	0.095*
H11C	0.4398	0.3008	0.7390	0.095*
C12	−0.0886 (6)	0.3744 (4)	0.7088 (6)	0.0575 (17)
H12A	−0.1164	0.3928	0.7833	0.086*
H12B	−0.1725	0.3415	0.6575	0.086*
H12C	−0.0679	0.4251	0.6641	0.086*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Hg	0.03850 (13)	0.03097 (13)	0.04205 (14)	−0.00121 (10)	0.00990 (8)	−0.00793 (11)
Cl1	0.0585 (9)	0.0360 (8)	0.0541 (9)	0.0049 (7)	0.0249 (7)	−0.0088 (7)
Cl2	0.0470 (8)	0.0549 (10)	0.0448 (9)	0.0077 (7)	0.0037 (6)	−0.0001 (8)
N1	0.050 (3)	0.032 (3)	0.041 (3)	−0.001 (2)	0.017 (2)	−0.006 (2)
N2	0.047 (3)	0.031 (3)	0.046 (3)	−0.004 (2)	0.007 (2)	−0.001 (2)
C1	0.034 (3)	0.039 (3)	0.037 (3)	0.007 (2)	0.008 (2)	0.012 (3)
C2	0.044 (3)	0.033 (3)	0.057 (4)	0.008 (3)	0.021 (3)	0.010 (3)
C3	0.069 (4)	0.040 (4)	0.048 (4)	0.003 (3)	0.022 (3)	0.009 (3)
C4	0.068 (4)	0.050 (4)	0.039 (4)	−0.013 (3)	0.009 (3)	0.009 (3)
C5	0.038 (3)	0.072 (5)	0.055 (4)	0.002 (3)	0.009 (3)	0.010 (4)
C6	0.046 (3)	0.055 (4)	0.047 (4)	0.003 (3)	0.018 (3)	0.006 (3)
C7	0.051 (3)	0.045 (4)	0.045 (4)	0.006 (3)	0.020 (3)	0.006 (3)
C8	0.076 (4)	0.050 (4)	0.046 (4)	−0.023 (3)	0.015 (3)	−0.018 (3)
C9	0.068 (4)	0.042 (4)	0.064 (4)	−0.018 (3)	0.020 (3)	−0.021 (3)
C10	0.075 (4)	0.043 (4)	0.061 (4)	−0.008 (3)	0.018 (3)	−0.001 (3)
C11	0.035 (3)	0.058 (5)	0.089 (5)	−0.006 (3)	−0.001 (3)	0.000 (4)
C12	0.062 (4)	0.048 (4)	0.069 (5)	0.026 (3)	0.029 (3)	0.003 (3)

Geometric parameters (Å, º)

Hg—N1	2.355 (4)	C5—C6	1.398 (8)
Hg—Cl1	2.3875 (14)	C5—H5A	0.9500
Hg—N2	2.411 (4)	C6—H6A	0.9500
Hg—Cl2	2.4397 (13)	C7—H7A	0.9900
N1—C8	1.472 (6)	C7—H7B	0.9900
N1—C7	1.491 (7)	C8—C9	1.503 (9)
N1—C12	1.497 (6)	C8—H8A	0.9900
N2—C10	1.460 (7)	C8—H8B	0.9900
N2—C9	1.465 (8)	C9—H9A	0.9900
N2—C11	1.489 (7)	C9—H9B	0.9900
C1—C2	1.375 (7)	C10—H10A	0.9800
C1—C6	1.386 (7)	C10—H10B	0.9800
C1—C7	1.491 (8)	C10—H10C	0.9800
C2—C3	1.379 (8)	C11—H11A	0.9800
C2—H2A	0.9500	C11—H11B	0.9800
C3—C4	1.380 (8)	C11—H11C	0.9800
C3—H3A	0.9500	C12—H12A	0.9800
C4—C5	1.364 (8)	C12—H12B	0.9800
C4—H4A	0.9500	C12—H12C	0.9800
N1—Hg—Cl1	129.73 (12)	C1—C7—N1	113.9 (5)
N1—Hg—N2	78.51 (16)	C1—C7—H7A	108.8
Cl1—Hg—N2	108.04 (12)	N1—C7—H7A	108.8
N1—Hg—Cl2	103.21 (11)	C1—C7—H7B	108.8
Cl1—Hg—Cl2	121.01 (5)	N1—C7—H7B	108.8
N2—Hg—Cl2	106.03 (11)	H7A—C7—H7B	107.7
C8—N1—C7	109.8 (4)	N1—C8—C9	114.7 (5)
C8—N1—C12	111.0 (5)	N1—C8—H8A	108.6
C7—N1—C12	109.0 (4)	C9—C8—H8A	108.6
C8—N1—Hg	104.3 (3)	N1—C8—H8B	108.6
C7—N1—Hg	115.1 (3)	C9—C8—H8B	108.6
C12—N1—Hg	107.6 (3)	H8A—C8—H8B	107.6
C10—N2—C9	110.1 (5)	N2—C9—C8	112.6 (5)
C10—N2—C11	110.1 (5)	N2—C9—H9A	109.1
C9—N2—C11	111.5 (5)	C8—C9—H9A	109.1
C10—N2—Hg	111.5 (3)	N2—C9—H9B	109.1
C9—N2—Hg	104.4 (3)	C8—C9—H9B	109.1
C11—N2—Hg	109.1 (3)	H9A—C9—H9B	107.8
C2—C1—C6	118.7 (5)	N2—C10—H10A	109.5
C2—C1—C7	119.9 (5)	N2—C10—H10B	109.5
C6—C1—C7	121.3 (5)	H10A—C10—H10B	109.5
C1—C2—C3	121.5 (5)	N2—C10—H10C	109.5
C1—C2—H2A	119.2	H10A—C10—H10C	109.5
C3—C2—H2A	119.2	H10B—C10—H10C	109.5
C2—C3—C4	119.5 (6)	N2—C11—H11A	109.5
C2—C3—H3A	120.2	N2—C11—H11B	109.5
C4—C3—H3A	120.2	H11A—C11—H11B	109.5
C5—C4—C3	119.9 (6)	N2—C11—H11C	109.5
C5—C4—H4A	120.0	H11A—C11—H11C	109.5
C3—C4—H4A	120.0	H11B—C11—H11C	109.5
C4—C5—C6	120.5 (6)	N1—C12—H12A	109.5
C4—C5—H5A	119.7	N1—C12—H12B	109.5
C6—C5—H5A	119.7	H12A—C12—H12B	109.5
C1—C6—C5	119.8 (6)	N1—C12—H12C	109.5
C1—C6—H6A	120.1	H12A—C12—H12C	109.5
C5—C6—H6A	120.1	H12B—C12—H12C	109.5
Cl1—Hg—N1—C8	89.5 (4)	C7—C1—C2—C3	−179.3 (5)
N2—Hg—N1—C8	−14.5 (4)	C1—C2—C3—C4	−1.2 (9)
Cl2—Hg—N1—C8	−118.5 (3)	C2—C3—C4—C5	0.0 (9)
Cl1—Hg—N1—C7	−30.9 (4)	C3—C4—C5—C6	0.7 (9)
N2—Hg—N1—C7	−134.9 (4)	C2—C1—C6—C5	−0.9 (8)
Cl2—Hg—N1—C7	121.2 (3)	C7—C1—C6—C5	−179.9 (5)
Cl1—Hg—N1—C12	−152.6 (3)	C4—C5—C6—C1	−0.3 (9)
N2—Hg—N1—C12	103.4 (4)	C2—C1—C7—N1	85.1 (6)
Cl2—Hg—N1—C12	−0.6 (4)	C6—C1—C7—N1	−95.8 (6)
N1—Hg—N2—C10	−132.3 (4)	C8—N1—C7—C1	−168.4 (5)
Cl1—Hg—N2—C10	99.4 (4)	C12—N1—C7—C1	69.8 (6)
Cl2—Hg—N2—C10	−31.7 (4)	Hg—N1—C7—C1	−51.1 (5)
N1—Hg—N2—C9	−13.4 (4)	C7—N1—C8—C9	166.8 (5)
Cl1—Hg—N2—C9	−141.7 (3)	C12—N1—C8—C9	−72.6 (7)
Cl2—Hg—N2—C9	87.2 (4)	Hg—N1—C8—C9	43.0 (6)
N1—Hg—N2—C11	105.9 (4)	C10—N2—C9—C8	160.3 (5)
Cl1—Hg—N2—C11	−22.4 (4)	C11—N2—C9—C8	−77.1 (6)
Cl2—Hg—N2—C11	−153.5 (4)	Hg—N2—C9—C8	40.5 (6)
C6—C1—C2—C3	1.6 (8)	N1—C8—C9—N2	−61.6 (7)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7A···Cl2^i	0.99	2.78	3.748 (6)	165

Symmetry code: (i) x+1/2, −y+1/2, z+1/2.