Poly[bis(N-methylformamide)tetra-μ-thiocyanato-manganese(II)mercury(II)]

The title complex, [MnHg(NCS)₄(C₂H₅NO)₂]_n, consists of slightly distorted MnN₄O₂ octa­hedra and HgS₄ tetra­hedra. Each Mn^II cation is bound to four N atoms of the NCS groups and two O atoms of the N-methyl­formamide (NMF) ligands in a cis configuration. Each Hg^II cation is coordinated to four S atoms of NCS groups. Each pair of Mn^II and Hg^II cations is connected by an –NCS– bridge, forming an infinite three-dimensional –Mn—NCS—Hg– network.

S1. Comment

Versatile and efficient sources of blue–violet or UV light are of fundamental importance for many applications, such as high-density optical data storage, medical diagnosis, photolithography, underwater communications and laser displays. Second-order nonlinear optical (SONLO) materials capable of efficient frequency conversion of IR or visible laser radiation to visible or UV wavelengths are of considerable interest in these fields (Zhang et al., 2004). Materials with large second-order optical nonlinearities, transparency at all wavelengths involved and stable physicochemical performance (thermal and temporal stability) are needed in order to realise many of these applications. Manganese mercury thiocyanate (MMTC; Yan et al., 1999) and quite a few of its Lewis-base adducts (Wang, Yu, Xu, Lu & Yuan, 2000; Wang, Yu, Xu, Lu, Yuan & Lu, 2000; Wang, Yu, Xu, Lu, Yuan, Liu & Lu, 2000; Yu et al., 2001) have been found to crystallize in acentric structures. All of them exhibit good SONLO effects and a wide transparency wavelength region. To continue this work, a novel compound, the title complex, (I), the N-methylformamide (NMF) adduct of MMTC, has been prepared. The crystal structure of the NMF adduct of cobalt mercury thiocyante, bis(N-methylformamide)tetrakis(thiocyanato)cobalt(II)mercury(II), was reported nearly 20 years ago (Kinoshita & Ouchi, 1986). It crystallizes in a non-centrosymmetric space group, but unfortunately the low-energy d–d transitions present in this compound because of the Co²⁺ ion are normally observed in the visible light region, which limits its SONLO usefulness. This compound is isostructural with (I). However, (I) has many better characteristics. It possesses a high SONLO effect and a wide optical transparency range. Furthermore, it is very easy to grow large single crystals of high optical quality.

According to the hard and soft acids and bases (HSAB) concept (Pearson, 1966; Balarew & Duhlew, 1984), harder metals show a pronounced affinity for coordination with harder ligands, while softer metals prefer coordination with softer ligands. In the structure of (I), each hard Mn^II cation is six-coordinated by four hard SCN ligands via their N atoms and two hard NMF ligands via their O atoms in a slightly distorted octahedral geometry; the Hg^II cation is four-coordinated by four soft SCN ligands via their S atoms in a slightly distorted tetrahedral geometry.

In (I), the two O atoms of the NMF ligands coordinate to the Mn^II cation in a cis conformation. However, in the similar structure of the DMSO adduct (Wang, Yu, Xu, Lu & Yuan, 2000), two O atoms of the DMSO ligands coordinate to the Mn^II cation in a trans conformation. This difference is due to the smaller size of NMF molecules compared with DMSO molecules. In (I), the Mn—N [2.199 (12)–2.240 (12) Å] and Mn—O [2.178 (9) and 2.176 (9) Å] bond lengths are all much larger than the sums of the ionic radii (2.13 and 2.02 Å, respectively; Shannon, 1976). The Hg—S bond lengths are in the range 2.526 (4)–2.563 (4) Å, with an average of 2.543 Å, a little larger than the sum of the single-bond covalent radii (2.52 Å; Pauling, 1960). The S—Hg—S bond angles [101.65 (14)–117.21 (16)°] deviate markedly from the typical tetrahedral angle.

The C—N—Mn angles [164.8 (12)–175.5 (12)°] are close to 180°, while the C—S—Hg angles [94.2 (4)–97.1 (5)°] are much smaller than 180° and exhibit significant bending. The C—N and C—S bond lengths are slightly smaller than the accepted triple-bond length of 1.16 Å and the normal single C—S bond length of 1.81 Å, respectively (Reference for standard values?). The SCN groups are quasi-linear [N—C—S angles 176.7 (13)–179.0 (13)°].

The striking feature of this type of complex is the –SCN– bridge, which connects the two metals to form infinite two- or three-dimensional networks; a three-dimensional network is formed in (I).

The macroscopic nonlinear susceptibility of the crystal of (I) may be related to the microscopic hyperpolarizabilities of the dipolar SCN⁻ ions, and to the octupolar distorted MnN₄O₂ octahedra and HgS₄ tetrahedra (Zyss & Ledoux, 1994). The second-harmonic generation (SHG) effect of the crystals has been studied (Kurtz & Perry, 1968) and found to be nearly the same as that of urea. The optical transmission of a crystal of (I) was measured by a Hitachi U-3500 spectrophotometer; it was found that the transparency range is 365–2920 nm.

S2. Experimental

An NMF solution (5 ml) of MMTC (4.41 g, 9 mmol) was added slowly to water (25 ml) with stirring at room temperature. After a while, compound (I) was precipitated. The crystals used for the X-ray structure analysis were obtained from a mixed solvent of NMF and water (1:3, v/v) using a temperature-lowering method.

S3. Refinement

All H atoms were placed in calculated positions, with C—H distances of 0.93 or 0.96 Å and N—H distances of 0.86 Å [Please check added text], and refined using a riding model, with U_iso(H) values of 1.2U_eq(C,N), or 1.5U_eq(C) for CH₃ groups.

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: Please provide missing details.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii.
	Fig. 2. A packing diagram for (I), showing the three-dimensional network.

Poly[(µ-thiocyanato-1:2κ²S:N)bis(thiocyanato-2κN)bis(N-methylformamide- 2κO)manganese(II)mercury(II)]

Crystal data

[MnHg(C2H5NO)2(SCN)4]	Dx = 2.121 Mg m^−3
Mr = 605.99	Mo Kα radiation, λ = 0.71069 Å
Orthorhombic, Pna21	Cell parameters from 43 reflections
a = 16.1203 (15) Å	θ = 6.4–12.5°
b = 7.7373 (7) Å	µ = 9.20 mm^−1
c = 15.2135 (18) Å	T = 293 K
V = 1897.5 (3) Å^3	Prism, colourless
Z = 4	0.23 × 0.18 × 0.13 mm
F(000) = 1140

Data collection

Bruker P4 diffractometer	1656 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.030
Graphite monochromator	θmax = 27.5°, θmin = 2.5°
ω scans	h = −1→20
Absorption correction: ψ scan (XSCANS; Siemens, 1996)	k = −1→10
Tmin = 0.10, Tmax = 0.30	l = −19→1
2951 measured reflections	3 standard reflections every 97 reflections
2417 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.040	w = 1/[σ^2(Fo^2) + (0.0304P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.077	(Δ/σ)max = 0.001
S = 0.98	Δρmax = 0.68 e Å^−3
2417 reflections	Δρmin = −0.56 e Å^−3
203 parameters	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.00286 (17)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 162 Friedel pairs
Secondary atom site location: difference Fourier map	Absolute structure parameter: 0.12 (2)

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.

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

	x	y	z	Uiso*/Ueq
C1	0.7531 (8)	0.3591 (16)	0.6134 (9)	0.063 (4)
C2	0.9972 (7)	0.1733 (16)	0.4615 (9)	0.053 (3)
C3	0.9924 (8)	0.6752 (18)	0.6124 (10)	0.063 (4)
C4	0.9914 (7)	0.6918 (18)	0.2928 (8)	0.054 (3)
C5	0.8091 (10)	0.893 (2)	0.4438 (12)	0.073 (4)
H5A	0.8643	0.9196	0.4325	0.088*
C6	0.6709 (13)	0.989 (2)	0.466 (2)	0.142 (10)
H6A	0.6374	1.0731	0.4363	0.214*
H6B	0.6608	0.9965	0.5284	0.214*
H6C	0.6568	0.8754	0.4458	0.214*
C7	0.7269 (10)	0.457 (2)	0.3243 (12)	0.061 (4)
H7	0.7099	0.5657	0.3439	0.074*
C8	0.7017 (12)	0.229 (3)	0.2256 (15)	0.161 (11)
H8A	0.7024	0.2442	0.1630	0.242*
H8B	0.6615	0.1426	0.2409	0.242*
H8C	0.7556	0.1935	0.2453	0.242*
N1	0.7936 (7)	0.3996 (14)	0.5555 (8)	0.065 (3)
N2	0.9499 (7)	0.2800 (16)	0.4477 (9)	0.072 (3)
N3	0.9536 (7)	0.6263 (16)	0.5552 (9)	0.074 (3)
N4	0.9507 (7)	0.6468 (16)	0.3485 (7)	0.062 (3)
N5	0.7558 (11)	1.0222 (17)	0.4492 (16)	0.101 (5)
H5B	0.7727	1.1267	0.4422	0.121*
N6	0.6807 (7)	0.3838 (18)	0.2655 (9)	0.082 (4)
H6D	0.6351	0.4332	0.2505	0.098*
O1	0.7911 (5)	0.7407 (12)	0.4526 (8)	0.071 (3)
O2	0.7906 (6)	0.3990 (12)	0.3568 (6)	0.063 (3)
S1	0.6957 (2)	0.2982 (6)	0.6976 (3)	0.0829 (12)
Mn1	0.87366 (12)	0.5179 (2)	0.45198 (15)	0.0525 (5)
Hg1	0.56627 (3)	0.45301 (6)	0.64685 (5)	0.06246 (18)
S2	1.0660 (3)	0.0241 (5)	0.4798 (3)	0.0734 (11)
S3	1.0456 (3)	0.7393 (6)	0.6995 (3)	0.0876 (13)
S4	1.0481 (2)	0.7590 (5)	0.2100 (3)	0.0665 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.057 (7)	0.050 (7)	0.081 (11)	−0.003 (6)	−0.007 (7)	0.019 (8)
C2	0.057 (7)	0.050 (7)	0.052 (7)	0.002 (7)	0.008 (7)	−0.007 (7)
C3	0.058 (7)	0.059 (8)	0.072 (11)	0.005 (7)	0.001 (7)	0.012 (8)
C4	0.049 (7)	0.072 (10)	0.040 (7)	0.014 (7)	−0.001 (6)	0.004 (7)
C5	0.069 (10)	0.065 (10)	0.085 (12)	0.005 (9)	0.003 (10)	−0.016 (10)
C6	0.132 (19)	0.075 (13)	0.22 (3)	0.030 (12)	0.02 (2)	−0.019 (17)
C7	0.073 (10)	0.050 (10)	0.062 (9)	0.002 (9)	0.014 (8)	0.020 (9)
C8	0.138 (17)	0.16 (2)	0.18 (2)	0.053 (17)	−0.055 (16)	−0.124 (19)
N1	0.064 (6)	0.074 (8)	0.057 (6)	−0.003 (6)	0.002 (6)	0.006 (7)
N2	0.078 (8)	0.061 (7)	0.078 (8)	0.015 (7)	0.014 (8)	−0.002 (7)
N3	0.079 (8)	0.072 (8)	0.072 (8)	−0.024 (6)	−0.018 (7)	−0.001 (7)
N4	0.069 (7)	0.072 (8)	0.046 (6)	0.005 (6)	−0.006 (6)	0.005 (6)
N5	0.093 (11)	0.048 (8)	0.161 (15)	−0.015 (8)	−0.001 (12)	0.003 (12)
N6	0.063 (7)	0.110 (11)	0.073 (8)	0.004 (7)	−0.024 (7)	−0.025 (9)
O1	0.070 (6)	0.051 (6)	0.092 (7)	−0.003 (5)	−0.005 (6)	−0.002 (6)
O2	0.068 (6)	0.056 (6)	0.066 (6)	0.003 (5)	−0.021 (5)	−0.008 (5)
S1	0.061 (2)	0.107 (3)	0.081 (2)	0.017 (2)	0.011 (2)	0.040 (3)
Mn1	0.0554 (10)	0.0506 (11)	0.0514 (10)	−0.0027 (9)	−0.0033 (9)	−0.0002 (10)
Hg1	0.0621 (3)	0.0680 (3)	0.0573 (2)	0.0089 (3)	−0.0029 (5)	0.0093 (5)
S2	0.088 (2)	0.077 (2)	0.0551 (19)	0.030 (2)	0.003 (2)	−0.0005 (19)
S3	0.120 (3)	0.070 (2)	0.072 (2)	−0.017 (2)	−0.041 (3)	0.009 (2)
S4	0.0521 (18)	0.074 (2)	0.073 (2)	0.0007 (17)	0.0102 (19)	0.009 (2)

Geometric parameters (Å, º)

C1—N1	1.140 (15)	C8—H8A	0.9600
C1—S1	1.649 (14)	C8—H8B	0.9600
C2—N2	1.144 (14)	C8—H8C	0.9600
C2—S2	1.625 (13)	N1—Mn1	2.233 (12)
C3—N3	1.136 (16)	N2—Mn1	2.214 (12)
C3—S3	1.655 (15)	N3—Mn1	2.199 (12)
C4—N4	1.127 (15)	N4—Mn1	2.240 (12)
C4—S4	1.641 (14)	N5—H5B	0.8600
C5—O1	1.218 (17)	N6—H6D	0.8600
C5—N5	1.32 (2)	O1—Mn1	2.178 (9)
C5—H5A	0.9300	O2—Mn1	2.176 (9)
C6—N5	1.42 (2)	S1—Hg1	2.526 (4)
C6—H6A	0.9600	Hg1—S3^i	2.534 (5)
C6—H6B	0.9600	Hg1—S2^ii	2.548 (4)
C6—H6C	0.9600	Hg1—S4^iii	2.563 (4)
C7—O2	1.226 (17)	S2—Hg1^iv	2.548 (4)
C7—N6	1.30 (2)	S3—Hg1^v	2.534 (5)
C7—H7	0.9300	S4—Hg1^vi	2.563 (4)
C8—N6	1.38 (2)
N1—C1—S1	179.0 (13)	C7—N6—H6D	118.6
N2—C2—S2	178.8 (13)	C8—N6—H6D	118.6
N3—C3—S3	176.7 (13)	C5—O1—Mn1	128.2 (10)
N4—C4—S4	178.1 (12)	C7—O2—Mn1	128.9 (10)
O1—C5—N5	124.7 (16)	C1—S1—Hg1	95.2 (5)
O1—C5—H5A	117.7	O2—Mn1—O1	87.8 (4)
N5—C5—H5A	117.7	O2—Mn1—N3	176.0 (4)
N5—C6—H6A	109.5	O1—Mn1—N3	93.0 (4)
N5—C6—H6B	109.5	O2—Mn1—N2	88.3 (4)
H6A—C6—H6B	109.5	O1—Mn1—N2	175.8 (4)
N5—C6—H6C	109.5	N3—Mn1—N2	90.7 (5)
H6A—C6—H6C	109.5	O2—Mn1—N1	86.6 (4)
H6B—C6—H6C	109.5	O1—Mn1—N1	88.2 (4)
O2—C7—N6	126.6 (16)	N3—Mn1—N1	89.5 (5)
O2—C7—H7	116.7	N2—Mn1—N1	90.0 (4)
N6—C7—H7	116.7	O2—Mn1—N4	93.5 (4)
N6—C8—H8A	109.5	O1—Mn1—N4	89.3 (4)
N6—C8—H8B	109.5	N3—Mn1—N4	90.4 (4)
H8A—C8—H8B	109.5	N2—Mn1—N4	92.4 (4)
N6—C8—H8C	109.5	N1—Mn1—N4	177.5 (4)
H8A—C8—H8C	109.5	S1—Hg1—S3^i	117.21 (16)
H8B—C8—H8C	109.5	S1—Hg1—S2^ii	109.83 (15)
C1—N1—Mn1	171.3 (12)	S3^i—Hg1—S2^ii	104.46 (15)
C2—N2—Mn1	164.8 (12)	S1—Hg1—S4^iii	101.65 (14)
C3—N3—Mn1	175.5 (12)	S3^i—Hg1—S4^iii	109.72 (16)
C4—N4—Mn1	171.5 (13)	S2^ii—Hg1—S4^iii	114.40 (14)
C5—N5—C6	120.2 (15)	C2—S2—Hg1^iv	97.1 (5)
C5—N5—H5B	119.9	C3—S3—Hg1^v	95.5 (5)
C6—N5—H5B	119.9	C4—S4—Hg1^vi	94.2 (4)
C7—N6—C8	122.9 (15)
S1—C1—N1—Mn1	−117 (83)	C3—N3—Mn1—N4	−169 (16)
S2—C2—N2—Mn1	−87 (72)	C2—N2—Mn1—O2	−168 (4)
S3—C3—N3—Mn1	−5 (40)	C2—N2—Mn1—O1	−146 (6)
S4—C4—N4—Mn1	104 (44)	C2—N2—Mn1—N3	8 (4)
O1—C5—N5—C6	0 (4)	C2—N2—Mn1—N1	−81 (4)
O2—C7—N6—C8	−5 (3)	C2—N2—Mn1—N4	99 (4)
N5—C5—O1—Mn1	−176.5 (16)	C1—N1—Mn1—O2	−134 (7)
N6—C7—O2—Mn1	177.6 (12)	C1—N1—Mn1—O1	−46 (7)
N1—C1—S1—Hg1	−168 (86)	C1—N1—Mn1—N3	47 (7)
C7—O2—Mn1—O1	0.8 (12)	C1—N1—Mn1—N2	138 (7)
C7—O2—Mn1—N3	103 (6)	C1—N1—Mn1—N4	−41 (14)
C7—O2—Mn1—N2	179.3 (13)	C4—N4—Mn1—O2	−61 (7)
C7—O2—Mn1—N1	89.2 (12)	C4—N4—Mn1—O1	−149 (7)
C7—O2—Mn1—N4	−88.4 (13)	C4—N4—Mn1—N3	118 (7)
C5—O1—Mn1—O2	−130.0 (15)	C4—N4—Mn1—N2	28 (7)
C5—O1—Mn1—N3	53.9 (16)	C4—N4—Mn1—N1	−153 (9)
C5—O1—Mn1—N2	−152 (6)	C1—S1—Hg1—S3^i	−90.6 (5)
C5—O1—Mn1—N1	143.3 (15)	C1—S1—Hg1—S2^ii	28.3 (5)
C5—O1—Mn1—N4	−36.5 (15)	C1—S1—Hg1—S4^iii	149.8 (5)
C3—N3—Mn1—O2	0 (21)	N2—C2—S2—Hg1^iv	122 (71)
C3—N3—Mn1—O1	102 (16)	N3—C3—S3—Hg1^v	−144 (25)
C3—N3—Mn1—N2	−76 (16)	N4—C4—S4—Hg1^vi	20 (45)
C3—N3—Mn1—N1	14 (16)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N5—H5B···O2^vii	0.86	2.49	3.285 (19)	154

Symmetry code: (vii) x, y+1, z.