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Volume 67 
Part 9 
Pages m307-m310  
September 2011  

Received 8 June 2011
Accepted 11 August 2011
Online 26 August 2011

Two W/Cu/S clusters: tetraethylammonium bromidodi-[mu]2-sulfido-sulfido[tris(3,5-dimethylpyrazol-1-yl)borato]copper(I)tungsten(VI) and tetraethylammonium dibromido-[mu]3-sulfido-di-[mu]2-sulfido-[tris(3,5-dimethylpyrazol-1-yl)borato]dicopper(I)tungsten(VI)

aDepartment of Chemistry, Nanchang University, Nanchang 330031, People's Republic of China
Correspondence e-mail: weizh@ncu.edu.cn

The reaction of (Et4N)[Tp*WS3] [Tp* = hydrogen tris(3,5-dimethylpyrazol-1-yl)borate] with one or two equivalents of CuBr afforded the [1 + 1] and [1 + 2] addition products (Et4N)[Tp*WS([mu]-S)2(CuBr)] {or (C8H20N)[CuWBr(C15H22BN6)S3], (I)} and (Et4N)[Tp*W([mu]3-S)([mu]-S)2(CuBr)2] {or (C8H20N)[Cu2WBr2(C15H22BN6)S3], (II)}. The anion of (I) contains a [W([mu]-S)2Cu] core formed by the addition of one CuBr unit to the [Tp*WS3] species. The anion of (II) has a butterfly-shaped [W([mu]3-S)([mu]-S)2Cu2] core formed by the addition of two CuBr units to the [Tp*WS3] species. The [Tp*WS3] sections of each complex exhibit approximate C3v point symmetry and have closely comparable geometry. In (II), both the anion and cation lie on a crystallographic mirror plane. The structure of (I) is noncentrosymmetric and polar.

Comment

In the past decades, the chemistry of Mo(W)/Cu/S clusters derived from reactions of metal sulfide synthons such as [MOxS4-x]2- or [Cp*MS3]- (M = Mo or W, x = 0-3, Cp* = pentamethylcyclopentadienyl) with CuX (X = Cl, Br, I, NCS, CN) has been investigated extensively because of their novel structures (Chisholm et al., 2002[Chisholm, M. H., Gallucci, J. & Phomphrai, K. (2002). Inorg. Chem. 41, 2785-2794.]; Parkin, 2004[Parkin, G. (2004). Chem. Rev. 104, 699-767.]; Zulys et al., 2005[Zulys, A., Dochnahl, M., Hollmann, D., Lohnwitz, K., Herrmann, J.-S., Roesky, P. W. & Blechert, S. (2005). Angew. Chem. Int. Ed. 44, 7794-7798.]) and their potential applications in biological systems (Lewinski et al., 2006[Lewinski, J., Sliwinski, W., Dranka, M., Justyyniak, I. & Lipkowski, J. (2006). Angew. Chem. Int. Ed. 45, 4826-4829.]) and opto-electronic materials (Vahrenkamp, 1999[Vahrenkamp, H. (1999). Acc. Chem. Res. 32, 589-596.]). Among these Mo(W)/Cu/S clusters, a complete series of products obtained by the stepwise addition of CuX has not previously been realized in a system involving the same components CuX and [MS4]2- or [EMS3]n- (E = O, n = 2 or E = Cp*, n = 1) in different molar ratios (Bunge et al., 2007[Bunge, S. D., Lance, J. M. & Bertke, J. A. (2007). Organometallics, 26, 6320-6328.]; Boomishankar et al., 2006[Boomishankar, R., Richards, P. I. & Steiner, A. (2006). Angew. Chem. Int. Ed. 45, 4632-4634.]; Malik et al., 1997[Malik, M. A., O'Brien, P., Motevalli, M. & Jones, A. C. (1997). Inorg. Chem. 36, 5076-5081.]; Kaupp et al., 1991[Kaupp, M., Stoll, H., Preuss, H., Kaim, W., Stahl, T., Van Koten, G., Wissing, E., Smeets, W. J. J. & Spek, A. L. (1991). J. Am. Chem. Soc. 113, 5606-5618.]). Recently, we have investigated the preparation of Mo(W)/Cu/S clusters from the precursor (Et4N)[Tp*WS3], where Tp* = hydrogen tris(3,5-dimethylpyrazol-1-yl)borate (Seino et al., 2001[Seino, H., Arai, Y., Iwata, N., Nagao, S., Mizobe, Y. & Hidai, M. (2001). Inorg. Chem. 40, 1677-1682.]), and this compound has been found to undergo stepwise addition reactions with one to four equivalents of CuNCS to yield the products [Tp*WS3(CuNCS)n]- (n = 1 or 2), [Tp*WS3(CuNCS)3Br]2- and the polymeric {Tp*WS3(CuNCS)4}- (Wei, Li, Ren et al., 2009[Wei, Z. H., Li, H. X., Ren, Z. G., Lang, J. P., Zhang, Y. & Sun, Z. R. (2009). Dalton Trans. pp. 3425-3433.]). In a continuation of our work in this area, we treated the precursor (Et4N)[Tp*WS3] with one to three equivalents of CuBr in a stepwise manner (Scheme 1[link] shows the stepwise addition of Cu+ to the WS3 core to construct a cubane-like unit) and

[Scheme 1]
obtained the [1 + 1], [1 + 2] and [1 + 3] products, (Et4N)[Tp*WS([mu]-S)2(CuBr)], (Et4N)[Tp*W([mu]3-S)([mu]-S)2(CuBr)2] and (Et4N)[Tp*W([mu]3-S)3(CuBr)3]. We have reported the crystal structure of the [1 + 3] product previously (Wei, Li, Cheng et al., 2009[Wei, Z. H., Li, H. X., Cheng, M. L., Tang, X. Y., Zhang, Y. & Lang, J. P. (2009). Inorg. Chem. 48, 2808-2817.]). We report herein he crystal structures of the [1 + 1] and [1 + 2] complexes, (I)[link] and (II)[link].
[Scheme 2]

The anion of complex (I)[link] comprises a [Tp*WS3]- unit and one CuBr group, with a pair of [mu]-S atoms forming a WS2Cu ring (Fig. 1[link]). One terminal S atom is retained. The structure closely resembles that of the anion in the related compound (Et4N)[Tp*WS([mu]-S)2(CuNCS)] (Wei, Li, Ren et al., 2009[Wei, Z. H., Li, H. X., Ren, Z. G., Lang, J. P., Zhang, Y. & Sun, Z. R. (2009). Dalton Trans. pp. 3425-3433.]). It is noteworthy that the comparable [1 + 1] addition complex is not known among the M/Cu/S clusters based on the related precursor [PPh3][Cp*MS3], while for the (Et4N)[OMS3] precursor, reactions with one equivalent of CuCl and CuCN have been reported to yield the products [Me4N][WOS([mu]-S)2(CuCl)] (Shamsur Rahman et al., 2000[Shamsur Rahman, A. B. M., Boller, H. & Klepp, O. K. (2000). Inorg. Chim. Acta, 305, 91-94.]) and (Et4N)[MoOS([mu]-S)2(CuCN)] (Zhang et al., 2008[Zhang, W. H., Song, Y. L., Zhang, Y. & Lang, J. P. (2008). Cryst. Growth Des. 8, 253-258.]), respectively. In (I)[link], atom Cu1 adopts a trigonal planar geometry, coordinated by one terminal Br atom and two [mu]-S atoms. The W1...Cu1 distance of 2.5893 (11) Å is slightly shorter than those in other butterfly-shaped or incomplete cubane core clusters. The terminal W1-S3 bond length of 2.141 (3) Å is similar to that in [WS4Cu2(dppm)3] [2.146 (4) Å; dppm = bis(diphenylphosphino)methane; Lang & Tatsumi, 1998[Lang, J. P. & Tatsumi, K. (1998). Inorg. Chem. 37, 6308-6316.]], but slightly shorter than those in the corresponding precursor (Et4N)[Tp*WS3] (mean 2.193 Å; Seino et al., 2001[Seino, H., Arai, Y., Iwata, N., Nagao, S., Mizobe, Y. & Hidai, M. (2001). Inorg. Chem. 40, 1677-1682.]) and in the cluster (Et4N)[Tp*WS([mu]-S)2(CuNCS)] [2.154 (3) Å; Wei, Li, Ren et al., 2009[Wei, Z. H., Li, H. X., Ren, Z. G., Lang, J. P., Zhang, Y. & Sun, Z. R. (2009). Dalton Trans. pp. 3425-3433.]]. The mean W-[mu]-S (2.268 Å), Cu-[mu]-S (2.193 Å) and Cu-Br [2.2831 (14) Å] bond lengths are slightly longer than the corresponding values in the complex (Et4N)[Tp*WS([mu]3-S)3(CuBr)3] (Wei, Li, Cheng et al., 2009[Wei, Z. H., Li, H. X., Cheng, M. L., Tang, X. Y., Zhang, Y. & Lang, J. P. (2009). Inorg. Chem. 48, 2808-2817.]).

The anion of complex (II)[link] has a butterfly-shaped [WS3Cu2] structure in which one [Tp*WS3] unit and two CuBr groups are linked via one [mu]3-S and two [mu]-S atoms (Fig. 2[link]). Atoms W1, S1, B1, N3, N4 and C6-C10 lie on a crystallographic mirror plane. Similar butterfly-shaped [WS3Cu2] cores have been observed in (Et4N)[Tp*WS3(CuNCS)2] (Wei, Li, Ren et al., 2009[Wei, Z. H., Li, H. X., Ren, Z. G., Lang, J. P., Zhang, Y. & Sun, Z. R. (2009). Dalton Trans. pp. 3425-3433.]), (PPh4)[(Cp*WS3(CuCN)2] (Lang et al., 2004[Lang, J. P., Xu, Q. F., Ji, W., Elim, H. I. & Tatsumi, K. (2004). Eur. J. Inorg. Chem. pp. 86-91.]) and [MOS3M'2(PPh3)3] (M = W, Mo; M' = Cu, Ag) (Müller et al., 1983[Müller, A., Schimanski, U. & Schimanski, J. (1983). Inorg. Chim. Acta, 76, 245-246.]). Each Cu atom in (II)[link] adopts a trigonal planar geometry, coordinated by one [mu]-S atom, one [mu]3-S atom and one terminal Br atom. The W...Cu distance of 2.6239 (10) Å is longer than that in complex (I)[link], but similar to those found in other complexes containing three-coordinated Cu, such as (Et4N)[Tp*WS([mu]3-S)3(CuBr)3] [2.6404 (2) Å; Wei, Li, Cheng et al., 2009[Wei, Z. H., Li, H. X., Cheng, M. L., Tang, X. Y., Zhang, Y. & Lang, J. P. (2009). Inorg. Chem. 48, 2808-2817.]] and (PPh4)[Cp*WS3(CuCN)2] [2.666 (3) Å; Lang et al., 2004[Lang, J. P., Xu, Q. F., Ji, W., Elim, H. I. & Tatsumi, K. (2004). Eur. J. Inorg. Chem. pp. 86-91.]]. Because of the coordination of the S atoms to the Cu atoms, the W1-S1 bond length of 2.331 (2) Å is longer than the W1-S2 bond length of 2.2293 (18) Å, and both bonds are elongated relative to the mean W-S bond length (2.193 Å) in the precursor (Et4N)[Tp*WS3] (Seino et al., 2001[Seino, H., Arai, Y., Iwata, N., Nagao, S., Mizobe, Y. & Hidai, M. (2001). Inorg. Chem. 40, 1677-1682.]).

Fig. 3[link] illustrates how the S and CuI centres of (I)[link] and (II)[link] build up sequentially towards the corners of a cubane-like unit. Firstly, one CuI centre is added to the Tp*WS3 unit to construct the [Tp*WS([mu]-S)2Cu] core with one terminal S atom remaining. Secondly, the two CuI centres in (II)[link] form the butterfly core [Tp*W([mu]-S)2([mu]3-S)Cu2]. A third CuI centre can then be added to the butterfly core of (II)[link] to produce an incomplete cubane-like unit, [Tp*W([mu]3-S)3Cu3], as in the previously published structure (Et4N)[Tp*W([mu]3-S)3(CuBr)3] (Wei, Li, Cheng et al., 2009[Wei, Z. H., Li, H. X., Cheng, M. L., Tang, X. Y., Zhang, Y. & Lang, J. P. (2009). Inorg. Chem. 48, 2808-2817.]). Throughout this sequence, the geometry of the [Tp*WS3] unit remains essentially unchanged: the r.m.s. deviations for overlay of the 26 non-H atoms in the core onto the precursor [Tp*WS3] are 0.14, 0.10 and 0.30 Å for (I)[link], (II)[link] and (Et4N)[Tp*W([mu]3-S)3(CuBr)3], respectively. The [Tp*WS3] unit exhibits approximate C3v point symmetry and one of the mirror planes is retained as a crystallographic symmetry element in (II)[link].

Packing diagrams are shown for (I)[link] and (II)[link] in Figs. 4[link] and 5[link], respectively. The structures contain comparable stacks of alternating complexes and Et4N+ cations running along the b axes. In (I)[link], these stacks are arranged so that the Cu-Br bonds point towards the same direction along the c axis, forming a noncentrosymmetric and polar structure. In (II)[link], the stacks are arranged in a centrosymmetric manner.

[Figure 1]
Figure 1
The molecular structure of (I)[link], with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitrary size.
[Figure 2]
Figure 2
The molecular structure of (II)[link], with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitrary size. Methyl H atoms on C6, C10, C13 and C15 are disordered over the mirror plane. [Symmetry code: (i) x, -y + [{3\over 2}], z.]
[Figure 3]
Figure 3
A view of the anions in (I)[link] and (II)[link] along the approximate threefold axis of the Tp* group. [Symmetry code: (i) x, -y + [{3\over 2}], z.]
[Figure 4]
Figure 4
A packing diagram of (I)[link], viewed along the b axis, showing the noncentrosymmetric and polar arrangement. H atoms have been omitted.
[Figure 5]
Figure 5
A packing diagram of (II)[link], viewed along the b axis, showing the centrosymmetric arrangement. H atoms have been omitted.

Experimental

All manipulations were performed under an argon atmosphere using standard Schlenk-line techniques. The precursor (Et4N)[Tp*WS3] was prepared as reported previously (Seino et al., 2001[Seino, H., Arai, Y., Iwata, N., Nagao, S., Mizobe, Y. & Hidai, M. (2001). Inorg. Chem. 40, 1677-1682.]). For these reactions, CHCl3 is a better solvent than MeCN because CuBr is poorly soluble in CHCl3 and it can facilitate the stepwise introduction of CuBr into [Tp*WS3]-. Compound (I)[link] is air sensitive and easily oxidized in solution to form (Et4N)[Tp*WO([mu]-S)2(CuBr)]. Complex (II)[link] is relatively air and moisture stable in the solid state.

For the synthesis of (I)[link], CuBr (14.4 mg, 0.1 mmol) was added to a solution of (Et4N)[Tp*WS3] (75 mg, 0.1 mmol) in CHCl3 (15 ml). After being stirred for half an hour, the resulting red solution was filtered and Et2O (30 ml) was carefully layered onto the surface of the filtrate. After 4 d, red prisms of (I)[link] were collected by filtration, washed with Et2O and dried in vacuo {yield 72.3 mg, 80% based on (Et4N)[Tp*WS3]}. Analysis calculated: C 32.46, H 4.98, N 11.52%; found C 32.32, H 4.55, N 11.95%. IR (KBr disc, cm-1): 2978 (m), 2920 (m), 2554 (w), 1628 (w), 1546 (s), 1440 (s), 1435 (s), 1418 (s), 1035 (m), 860 (w), 806 (w), 691 (w), 651 (w), 459 (m), 416 (w). UV-visible {MeCN, [lambda]max [nm ([epsilon] M-1 cm-1)]}: 333 (14300), 445 (6400), 524 (3000). 1H NMR (400 MHz, CDCl3): [delta] 1.36-1.40 (t, 12H, CH2CH3), 2.37 (s, 9H, CH3 in Tp*), 2.95 (s, 9H, CH3 in Tp*), 3.33-3.39 (q, 8H, CH2CH3), 5.94 (s, 3H, CH in Tp*), the B-H proton was not identified.

For the synthesis of (II)[link], CuBr (28.8 mg, 0.2 mmol) was added to a solution of (Et4N)[Tp*WS3] (75 mg, 0.1 mmol) in CHCl3 (15 ml). A procedure identical to that used for (I)[link] afforded dark red blocks of (II)[link] {yield 93 mg, 85% based on (Et4N)[Tp*WS3]}. Analysis calculated: C 27.78, H 4.26, N 9.86%; found: C 27.32; H 4.55; N 9.95%. IR (KBr disc, cm-1): 2979 (m), 2921 (m), 2554 (w), 1628 (w), 1546 (s), 1440 (s), 1435 (s), 1418 (s), 1035 (m), 860 (w), 806 (w), 693 (w), 651 (w), 469 (w), 420 (w). UV-visible {MeCN, [lambda]max [nm ([epsilon] M-1 cm-1)]}: 323 (16300), 420 (8890), 544 (5800). 1H NMR (400 MHz, DMSO-d6): [delta] 1.36-1.40 (t, 12H, CH2CH3), 2.37 (s, 9H, CH3 in Tp*), 2.96 (s, 9H, CH3 in Tp*), 3.31-3.38 (q, 8H, CH2CH3), 5.92 (s, 3H, CH in Tp*), the B-H proton was not identified.

Compound (I)[link]

Crystal data
  • (C8H20N)[CuWBr(C15H22BN6)S3]

  • Mr = 850.95

  • Orthorhombic, P n a 21

  • a = 19.058 (4) Å

  • b = 10.276 (2) Å

  • c = 16.323 (3) Å

  • V = 3196.6 (11) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 5.73 mm-1

  • T = 293 K

  • 0.35 × 0.30 × 0.25 mm

Data collection
  • Rigaku Mercury CCD diffractometer

  • Absorption correction: multi-scan (Jacobson, 1998[Jacobson, R. (1998). Private communication to Rigaku Corporation, Tokyo, Japan.]) Tmin = 0.147, Tmax = 0.239

  • 29584 measured reflections

  • 5857 independent reflections

  • 5342 reflections with I > 2[sigma](I)

  • Rint = 0.044

Refinement
  • R[F2 > 2[sigma](F2)] = 0.038

  • wR(F2) = 0.084

  • S = 1.10

  • 5710 reflections

  • 344 parameters

  • 84 restraints

  • H-atom parameters constrained

  • [Delta][rho]max = 1.05 e Å-3

  • [Delta][rho]min = -0.59 e Å-3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 2678 Friedel pairs

  • Flack parameter: 0.004 (10)

Compound (II)[link]

Crystal data
  • (C8H20N)[Cu2WBr2(C15H22BN6)S3]

  • Mr = 994.40

  • Orthorhombic, P n m a

  • a = 12.808 (3) Å

  • b = 11.768 (2) Å

  • c = 22.569 (5) Å

  • V = 3401.7 (12) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 7.17 mm-1

  • T = 293 K

  • 0.40 × 0.30 × 0.17 mm

Data collection
  • Rigaku Mercury CCD diffractometer

  • Absorption correction: multi-scan (Jacobson, 1998[Jacobson, R. (1998). Private communication to Rigaku Corporation, Tokyo, Japan.]) Tmin = 0.087, Tmax = 0.295

  • 32255 measured reflections

  • 3282 independent reflections

  • 2999 reflections with I > 2[sigma](I)

  • Rint = 0.068

Refinement
  • R[F2 > 2[sigma](F2)] = 0.043

  • wR(F2) = 0.120

  • S = 1.09

  • 3276 reflections

  • 206 parameters

  • H-atom parameters constrained

  • [Delta][rho]max = 1.48 e Å-3

  • [Delta][rho]min = -1.15 e Å-3

H atoms were placed geometrically and constrained to ride on their parent atoms, with B-H = 0.98 Å and C-H = 0.96 (methyl), 0.97 (methylene) or 0.93 Å (aromatic), and with Uiso(H) = 1.5Ueq(C) for methyl H atoms or 1.2Ueq(C) otherwise. In (I), extensive rigid-bond and similarity restraints were applied to the displacement parameters of atoms C4, C5, C9, C10, N7 and C16-C23. In (II), the methyl H atoms on C6 and C10 (in the pyrazole ring) and on C13 and C15 (in the Et4N+ cation) are disordered over the mirror plane.

For both compounds, data collection: CrystalClear (Rigaku, 2001[Rigaku (2001). CrystalClear and CrystalStructure. Rigaku Corporation, Tokyo, Japan.]); cell refinement: CrystalClear; data reduction: CrystalStructure (Rigaku, 2001[Rigaku (2001). CrystalClear and CrystalStructure. Rigaku Corporation, Tokyo, Japan.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.


Supplementary data for this paper are available from the IUCr electronic archives (Reference: BI3020 ). Services for accessing these data are described at the back of the journal.


Acknowledgements

The authors acknowledge the Education Department of Jiangxi Province (grant No. GJJ11033) for financial support.

References

Boomishankar, R., Richards, P. I. & Steiner, A. (2006). Angew. Chem. Int. Ed. 45, 4632-4634.  [ISI] [CSD] [CrossRef] [ChemPort]
Bunge, S. D., Lance, J. M. & Bertke, J. A. (2007). Organometallics, 26, 6320-6328.  [CSD] [CrossRef] [ChemPort]
Chisholm, M. H., Gallucci, J. & Phomphrai, K. (2002). Inorg. Chem. 41, 2785-2794.  [ISI] [CSD] [CrossRef] [PubMed] [ChemPort]
Flack, H. D. (1983). Acta Cryst. A39, 876-881.  [CrossRef] [details]
Jacobson, R. (1998). Private communication to Rigaku Corporation, Tokyo, Japan.
Kaupp, M., Stoll, H., Preuss, H., Kaim, W., Stahl, T., Van Koten, G., Wissing, E., Smeets, W. J. J. & Spek, A. L. (1991). J. Am. Chem. Soc. 113, 5606-5618.  [CrossRef] [ChemPort] [ISI]
Lang, J. P. & Tatsumi, K. (1998). Inorg. Chem. 37, 6308-6316.  [ISI] [CrossRef] [ChemPort]
Lang, J. P., Xu, Q. F., Ji, W., Elim, H. I. & Tatsumi, K. (2004). Eur. J. Inorg. Chem. pp. 86-91.  [ISI] [CSD] [CrossRef]
Lewinski, J., Sliwinski, W., Dranka, M., Justyyniak, I. & Lipkowski, J. (2006). Angew. Chem. Int. Ed. 45, 4826-4829.  [ChemPort]
Malik, M. A., O'Brien, P., Motevalli, M. & Jones, A. C. (1997). Inorg. Chem. 36, 5076-5081.  [CrossRef] [ChemPort] [ISI]
Müller, A., Schimanski, U. & Schimanski, J. (1983). Inorg. Chim. Acta, 76, 245-246.
Parkin, G. (2004). Chem. Rev. 104, 699-767.  [ISI] [CrossRef] [PubMed] [ChemPort]
Rigaku (2001). CrystalClear and CrystalStructure. Rigaku Corporation, Tokyo, Japan.
Seino, H., Arai, Y., Iwata, N., Nagao, S., Mizobe, Y. & Hidai, M. (2001). Inorg. Chem. 40, 1677-1682.  [ISI] [CSD] [CrossRef] [PubMed] [ChemPort]
Shamsur Rahman, A. B. M., Boller, H. & Klepp, O. K. (2000). Inorg. Chim. Acta, 305, 91-94.  [CSD] [CrossRef] [ChemPort]
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.  [CrossRef] [details]
Vahrenkamp, H. (1999). Acc. Chem. Res. 32, 589-596.  [ISI] [CrossRef] [ChemPort]
Wei, Z. H., Li, H. X., Cheng, M. L., Tang, X. Y., Zhang, Y. & Lang, J. P. (2009). Inorg. Chem. 48, 2808-2817.  [ISI] [CSD] [CrossRef] [ChemPort]
Wei, Z. H., Li, H. X., Ren, Z. G., Lang, J. P., Zhang, Y. & Sun, Z. R. (2009). Dalton Trans. pp. 3425-3433.  [CSD] [CrossRef]
Zhang, W. H., Song, Y. L., Zhang, Y. & Lang, J. P. (2008). Cryst. Growth Des. 8, 253-258.  [CSD] [CrossRef]
Zulys, A., Dochnahl, M., Hollmann, D., Lohnwitz, K., Herrmann, J.-S., Roesky, P. W. & Blechert, S. (2005). Angew. Chem. Int. Ed. 44, 7794-7798.  [ISI] [CSD] [CrossRef] [ChemPort]


Acta Cryst (2011). C67, m307-m310   [ doi:10.1107/S0108270111032586 ]