Poly­[mercury(II)-di-μ-chloro-μ-pyrazine-κ²N:N′]

In [HgCl₂(Pyp)]_n (Pyp = pyrazine, C₄H₄N₂), chloride-bridged HgCl_4/2 strands are connected into layers by pyrazine mol­ecules. The Hg atom is on a site of symmetry 2/m, the unique Cl atom is on a mirror plane, the unique N atom is on a twofold rotation axis, and the unique C and H atoms are in general positions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.023
• wR factor = 0.051
• Data-to-parameter ratio = 13.6

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .......       0.94

Alert level C
CHEMW01_ALERT_1_C  The difference between the given and expected weight for
            compound is greater 1 mass unit. Check that all hydrogen
            atoms have been taken into account.
REFLT03_ALERT_3_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           25.93
           From the CIF: _diffrn_reflns_theta_full           0.00
           From the CIF: _reflns_number_total                354
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns          378
           Completeness (_total/calc)             93.65%
PLAT022_ALERT_3_C Ratio Unique / Expected Reflections too Low ....       0.94
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT150_ALERT_1_C Volume as Calculated Differs from that Given ...     355.60 Ang-3
PLAT342_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          9
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          1
PLAT742_ALERT_1_C Angle   Calc    90.00(6), Rep       90.00 ......    Missing su
              N    -HG   -CL      1.555   1.555   1.555
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.11 Ratio

Alert level G
ABSTM02_ALERT_3_G  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.150     0.399
            Tmin' and Tmax expected:      0.005     0.012
            RR' =      0.814
            Please check that your absorption correction is appropriate.

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

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 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
   2 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-STEP32 (Stoe & Cie, 2000); data reduction: X-RED (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97.

Poly[di-µ-chloro-µ-pyrazine-κ²N:N'-mercury(II)]

Crystal data

[HgCl2(C4H4N2)]	F(000) = 308
Mr = 349.57	Dx = 3.265 Mg m^−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2y	Cell parameters from 1625 reflections
a = 11.8970 (17) Å	θ = 3.4–25.9°
b = 7.783 (3) Å	µ = 22.30 mm^−1
c = 3.840 (7) Å	T = 293 K
β = 90.99 (6)°	Prism, colorless
V = 355.6 (7) Å^3	0.2 × 0.2 × 0.2 mm
Z = 2

Data collection

Stoe IPDS-I diffractometer	354 independent reflections
Radiation source: fine-focus sealed tube	354 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.079
φ scans	θmax = 25.9°, θmin = 3.4°
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1998)	h = −14→14
Tmin = 0.150, Tmax = 0.399	k = −9→9
1625 measured reflections	l = −4→4

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)] = 0.023	H-atom parameters constrained
wR(F^2) = 0.051	w = 1/[σ^2(Fo^2) + (0.0286P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max < 0.001
354 reflections	Δρmax = 1.12 e Å^−3
26 parameters	Δρmin = −1.28 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0103 (13)

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	0.0000	−0.5000	0.5000	0.0346 (2)
Cl	0.15561 (15)	−0.5000	1.0698 (6)	0.0391 (4)
N	0.0000	−0.1776 (9)	0.5000	0.0339 (14)
C	0.0900 (4)	−0.0902 (8)	0.4042 (19)	0.0393 (12)
H0	0.1540	−0.1491	0.3362	0.047*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Hg	0.0386 (3)	0.0315 (3)	0.0342 (3)	0.000	0.01371 (15)	0.000
Cl	0.0304 (9)	0.0464 (10)	0.0408 (11)	0.000	0.0088 (7)	0.000
N	0.029 (3)	0.038 (3)	0.034 (4)	0.000	0.008 (2)	0.000
C	0.030 (3)	0.038 (3)	0.050 (4)	0.005 (2)	0.010 (2)	−0.002 (3)

Geometric parameters (Å, º)

Hg—Cl^i	2.503 (3)	Cl—Hg^iv	2.503 (3)
Hg—Cl^ii	2.503 (3)	N—C	1.326 (7)
Hg—N^iii	2.510 (7)	N—C^v	1.326 (7)
Hg—N	2.510 (7)	C—C^vi	1.404 (12)
Hg—Cl^iii	2.842 (4)	C—H0	0.930
Hg—Cl	2.842 (4)
Cl^i—Hg—Cl^ii	180	Cl^ii—Hg—Cl	88.35 (12)
Cl^i—Hg—N^iii	90	N^iii—Hg—Cl	90
Cl^ii—Hg—N^iii	90	N—Hg—Cl	90
Cl^i—Hg—N	90	Cl^iii—Hg—Cl	180
Cl^ii—Hg—N	90	Hg^iv—Cl—Hg	91.65 (12)
N^iii—Hg—N	180	C—N—C^v	118.3 (7)
Cl^i—Hg—Cl^iii	88.35 (12)	C—N—Hg	120.9 (4)
Cl^ii—Hg—Cl^iii	91.65 (12)	C^v—N—Hg	120.9 (4)
N^iii—Hg—Cl^iii	90	N—C—C^vi	120.9 (4)
N—Hg—Cl^iii	90	N—C—H0	119.6
Cl^i—Hg—Cl	91.65 (12)	C^vi—C—H0	119.6

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