PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of actaeInternational Union of Crystallographysearchopen accessarticle submissionjournal home pagethis article
 
Acta Crystallogr Sect E Struct Rep Online. 2009 January 1; 65(Pt 1): m105.
Published online 2008 December 20. doi:  10.1107/S1600536808042116
PMCID: PMC2968009

A crystallographically isolated dimeric hydrolyzed chloro­phosphazene dianion

Abstract

Single crystals of the title compound bis[bis­(1-ethyl-3-methyl-imidazol-2-yl­idene)silver(I)] 1,5,5,7,11,11-hexa­chloro-2,8-di­oxa-4,6,10,12,13,14-hexa­aza-1λ5,3,5λ5,7λ5,9,11λ5-hexa­phospha­tricyclo­[7.3.1.13,7]tetra­deca-1(13),4,7(14),10-tetra­ene-6,12-diide 3,9-dioxide, [Ag(C6H10N2)2](Cl6N6O4P6)0.5, were isolated from the reaction of the silver N-heteocyclic carbene complex [Ag(C6H10N2)2]Cl and hexa­chloro­cyclo­triphos­phazene [NPCl2]3 in the presence of water. The asymmetric unit contains one silver carbene cation with the carbene ligands bound to the Ag(I) in an almost linear arrangement and one half of a hydrolyzed phosphazene dianion. The second cation and additional half of the anion are generated by an inversion center.

Related literature

For background on phosphazene hydrolysis products, see: Allcock (2003 [triangle]); Allcock et al. (1975 [triangle]); Gabler & Haw (1990 [triangle]); Murray et al. (1994 [triangle]); van de Grampel (1992 [triangle]). For related structures, see: Bartlett et al. (2006 [triangle]); Brandt et al. (1991 [triangle]); Bullen (1971 [triangle]); Meetsma et al. (1990 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-0m105-scheme1.jpg

Experimental

Crystal data

  • [Ag(C6H10N2)2](Cl6N6O4P6)0.5
  • M r = 601.48
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-0m105-efi1.jpg
  • a = 9.3224 (15) Å
  • b = 10.6190 (18) Å
  • c = 12.257 (2) Å
  • α = 78.916 (3)°
  • β = 71.558 (3)°
  • γ = 76.107 (3)°
  • V = 1108.4 (3) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 1.51 mm−1
  • T = 100 (2) K
  • 0.30 × 0.08 × 0.04 mm

Data collection

  • Bruker SMART CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2001 [triangle]) T min = 0.660, T max = 0.942
  • 8912 measured reflections
  • 4459 independent reflections
  • 3484 reflections with I > \2s(I)
  • R int = 0.031

Refinement

  • R[F 2 > 2σ(F 2)] = 0.047
  • wR(F 2) = 0.123
  • S = 1.04
  • 4459 reflections
  • 257 parameters
  • H-atom parameters constrained
  • Δρmax = 2.25 e Å−3
  • Δρmin = −1.02 e Å−3

Data collection: SMART (Bruker, 2007 [triangle]); cell refinement: SAINT (Bruker, 2007 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Selected geometric parameters (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808042116/br2087sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808042116/br2087Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

We thank the National Science Foundation (USA) for support of this work under grants CHE-0316944 and CHE-0616601 and grant CHE-0116041 for the funds used to support the X-ray facilities at the University of Akron.

supplementary crystallographic information

Comment

Hexachlorocyclotriphosphazene [NPCl2]3 is used as a starting material for the synthesis of poly(dichlorophosphazene). This conversion can be achived by a ring opening melt polymerization process at high temperature, generally greater than 473 °K. It has long been contested that trace amounts of water not only accelerate the rate of polymerization but are necessray to generate active species needed to simply promote polymer formation (Allcock, 2003; Allcock et al., 1975). Isolation of hydrolyzed species gives insight into the still unclear role that water plays in this polymerization reaction (Gabler et al., 1990). As part of our broader studies on the irreproducibility in the synthesis of poly(dichlorophosphazene) we report the first crystal structure of a dimeric hydrolyzed chlorophosphazene dianion.

The asymmetric unit consists of one silver N-heteocyclic carbene cation [AgC12H20N4]+ and half of a hydrolyzed phosphazene dianion [Cl6N6O4P6]2-. The second cation and other half of the dianion are generated by a crystallographic inversion center at x,y,z (1/2,1/2,1/2) located between one of the bridging oxygen atoms of the dimeric dianion and its symmetry generated equivalent. Each of the Ag(I) atoms is bound to two identical N-heterocyclic carbene ligands in a linear fashion. Two partially hydrolyzed phosphazene rings are joined by bridging oxygen atoms from a phosphorus atom of one ring to the other to form the dimeric dianion. The P—O—P bonds of the bridging oxygen atoms are inequivalent . The P—N bond distances of the individual rings deviate from the reported values of hexachlorocyclotriphosphazene, all six being virtually equivalent (Bartlett et al., 2006; Bullen, 1971). Two of the P—N bonds on each of the rings show significant double bond character while the remaining P—N bonds are lengthened to give more single bond character.

Experimental

The title compound, bis[bis(1-ethyl-3-methylimidazol-2-ylidene)silver(I)] 1,5,5,7,11,11-hexachloro-2,8-dioxa-4,6,10,12,13,14-hexaaza-1λ5,3,5λ5,7λ5,9,11λ5-hexaphosphatricyclo[7.3.1.13,7]tetradeca-1(13),4,7(14),10-tetraene-6,12-diide 3,9-dioxide, [Ag(C6H10N2)2](Cl6N6O4P6)0.5, was isolated from the reaction of silver N-heteocyclic carbene complex [AgC12H20N4]+.Cl- (generated in situ) and hexachlorocyclotriphosphazene, [NPCl2]3. A small amount of crystals were obtained after removing volatiles from the reaction.

Refinement

Hydrogen atoms were calculated and palced in geometrically idealized positions with C—H distances of 0.95 Å (aromatic), 0.99 Å (methylene), and 0.98 Å (methyl). H atoms were constrained to ride on the parent carbon atom with Uiso(H) = 1.2 Ueq(C) for aromatic and methylene and Uiso(H) = 1.5 Ueq(C) for methyl protons.

Figures

Fig. 1.
Structure of the title compound, first crystallographically characterized dimeric oxygen-bridged chlorophosphazene dianion. A numbering scheme of the non-H atoms is shown and thermal ellipsoids shown at 50% probability.

Crystal data

[Ag(C6H10N2)2](Cl6N6O4P6)0.5Z = 2
Mr = 601.48F(000) = 600
Triclinic, P1Dx = 1.802 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 9.3224 (15) ÅCell parameters from 2618 reflections
b = 10.6190 (18) Åθ = 2.5–26.8°
c = 12.257 (2) ŵ = 1.51 mm1
α = 78.916 (3)°T = 100 K
β = 71.558 (3)°Plate, colourless
γ = 76.107 (3)°0.30 × 0.08 × 0.04 mm
V = 1108.4 (3) Å3

Data collection

Bruker SMART CCD area-detector diffractometer4459 independent reflections
Radiation source: fine-focus sealed tube3484 reflections with I > \2s(I)
graphiteRint = 0.031
[var phi] and ω scansθmax = 26.3°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Bruker, 2001)h = −11→11
Tmin = 0.660, Tmax = 0.942k = −13→13
8912 measured reflectionsl = −15→15

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.047Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.123H-atom parameters constrained
S = 1.04w = 1/[σ2(Fo2) + (0.0737P)2] where P = (Fo2 + 2Fc2)/3
4459 reflections(Δ/σ)max < 0.001
257 parametersΔρmax = 2.25 e Å3
0 restraintsΔρmin = −1.02 e Å3

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 (Å2)

xyzUiso*/Ueq
Ag0.92396 (4)0.82923 (3)0.02673 (3)0.02921 (14)
Cl10.20816 (15)0.96514 (11)0.50044 (11)0.0364 (3)
Cl20.06691 (14)0.72027 (14)0.58126 (11)0.0402 (3)
Cl30.32100 (13)0.28263 (12)0.39490 (11)0.0312 (3)
P10.50886 (13)0.63373 (11)0.34302 (10)0.0220 (3)
P20.27569 (13)0.76965 (11)0.50900 (10)0.0218 (3)
P30.46494 (13)0.36960 (11)0.43519 (10)0.0196 (3)
O10.5964 (4)0.6691 (3)0.2226 (3)0.0298 (8)
O20.4577 (3)0.4948 (3)0.3425 (3)0.0243 (7)
N10.6862 (5)1.0763 (4)0.0964 (4)0.0346 (10)
N20.6984 (5)1.0504 (4)−0.0734 (4)0.0330 (10)
N31.1582 (4)0.6223 (4)0.1266 (3)0.0298 (9)
N41.1637 (4)0.5782 (4)−0.0374 (3)0.0277 (9)
N50.6039 (4)0.5991 (3)0.4376 (3)0.0219 (8)
N60.3458 (4)0.7321 (4)0.3838 (3)0.0259 (9)
N70.3694 (4)0.7221 (3)0.6012 (3)0.0207 (8)
C10.7588 (5)0.9961 (4)0.0151 (4)0.0287 (11)
C20.5818 (6)1.1759 (5)0.0603 (6)0.0454 (15)
H20.51681.24410.10330.055*
C30.5876 (6)1.1600 (5)−0.0462 (5)0.0414 (14)
H30.52741.2135−0.09370.050*
C40.7138 (7)1.0544 (6)0.2095 (5)0.0455 (14)
H4A0.82421.01720.20130.055*
H4B0.68911.13910.24040.055*
C50.6220 (9)0.9672 (7)0.2893 (6)0.0638 (19)
H5A0.51271.00740.30280.096*
H5B0.64830.94940.36290.096*
H5C0.64230.88500.25690.096*
C60.7431 (8)0.9969 (6)−0.1845 (5)0.0513 (16)
H6A0.85450.9887−0.21950.077*
H6B0.68891.0558−0.23700.077*
H6C0.71550.9106−0.17070.077*
C71.0921 (5)0.6642 (5)0.0399 (4)0.0263 (10)
C81.2702 (6)0.5110 (5)0.1032 (5)0.0398 (13)
H81.33280.46320.15110.048*
C91.2735 (6)0.4839 (5)0.0001 (4)0.0375 (13)
H91.33890.4132−0.03940.045*
C101.1113 (6)0.6846 (5)0.2325 (4)0.0369 (12)
H10A1.20100.67080.26310.044*
H10B1.07810.78000.21350.044*
C110.9870 (8)0.6337 (8)0.3212 (6)0.074 (2)
H11A0.90420.63420.28780.111*
H11B0.94710.68840.38430.111*
H11C1.02550.54390.35160.111*
C121.1316 (6)0.5854 (5)−0.1481 (4)0.0313 (11)
H12A1.02300.6247−0.14050.047*
H12B1.15320.4971−0.16970.047*
H12C1.19700.6390−0.20810.047*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Ag0.0342 (2)0.0232 (2)0.0293 (2)0.00745 (15)−0.01754 (17)−0.00302 (15)
Cl10.0483 (7)0.0219 (6)0.0319 (7)0.0102 (5)−0.0150 (6)−0.0023 (5)
Cl20.0273 (6)0.0564 (9)0.0366 (7)−0.0102 (6)−0.0147 (5)0.0073 (6)
Cl30.0295 (6)0.0343 (7)0.0365 (7)−0.0071 (5)−0.0155 (5)−0.0084 (5)
P10.0282 (6)0.0178 (6)0.0176 (6)0.0025 (5)−0.0096 (5)0.0003 (4)
P20.0234 (6)0.0208 (6)0.0185 (6)0.0026 (5)−0.0095 (5)0.0015 (5)
P30.0223 (6)0.0175 (6)0.0200 (6)−0.0007 (4)−0.0114 (5)0.0005 (4)
O10.0401 (19)0.0250 (17)0.0163 (17)0.0015 (14)−0.0058 (14)0.0028 (13)
O20.0313 (17)0.0224 (16)0.0219 (17)0.0008 (13)−0.0180 (14)0.0010 (13)
N10.037 (2)0.025 (2)0.039 (3)0.0035 (18)−0.015 (2)−0.0027 (19)
N20.036 (2)0.025 (2)0.035 (2)−0.0018 (18)−0.0168 (19)0.0090 (18)
N30.030 (2)0.033 (2)0.027 (2)0.0016 (17)−0.0141 (18)−0.0029 (18)
N40.029 (2)0.027 (2)0.022 (2)0.0010 (17)−0.0080 (17)0.0022 (16)
N50.0208 (18)0.022 (2)0.022 (2)0.0016 (15)−0.0099 (15)−0.0025 (15)
N60.032 (2)0.024 (2)0.0180 (19)0.0097 (16)−0.0143 (16)0.0007 (15)
N70.0247 (19)0.0208 (19)0.0169 (19)−0.0001 (15)−0.0103 (15)−0.0007 (15)
C10.034 (3)0.023 (2)0.033 (3)−0.003 (2)−0.019 (2)0.000 (2)
C20.039 (3)0.027 (3)0.058 (4)0.005 (2)−0.010 (3)0.002 (3)
C30.033 (3)0.032 (3)0.048 (4)0.000 (2)−0.015 (3)0.018 (3)
C40.053 (4)0.041 (3)0.045 (3)−0.003 (3)−0.015 (3)−0.018 (3)
C50.088 (5)0.062 (4)0.055 (4)−0.026 (4)−0.032 (4)−0.004 (3)
C60.076 (4)0.048 (4)0.033 (3)−0.007 (3)−0.030 (3)0.006 (3)
C70.025 (2)0.027 (3)0.025 (2)−0.0039 (19)−0.010 (2)0.0021 (19)
C80.034 (3)0.040 (3)0.044 (3)0.010 (2)−0.024 (3)−0.001 (3)
C90.035 (3)0.036 (3)0.031 (3)0.013 (2)−0.011 (2)−0.003 (2)
C100.037 (3)0.045 (3)0.031 (3)−0.002 (2)−0.017 (2)−0.008 (2)
C110.086 (5)0.110 (6)0.034 (4)−0.055 (5)0.013 (3)−0.029 (4)
C120.032 (3)0.040 (3)0.016 (2)−0.004 (2)−0.003 (2)0.000 (2)

Geometric parameters (Å, °)

Ag—C12.065 (5)N5—P3i1.554 (4)
Ag—C72.070 (5)N7—P3i1.594 (4)
Cl1—P22.0118 (16)C2—C31.331 (8)
Cl2—P22.0171 (17)C2—H20.9500
Cl3—P32.0217 (16)C3—H30.9500
P1—O11.468 (3)C4—C51.432 (9)
P1—N51.610 (4)C4—H4A0.9900
P1—N61.615 (4)C4—H4B0.9900
P1—O21.657 (3)C5—H5A0.9800
P2—N61.555 (4)C5—H5B0.9800
P2—N71.578 (4)C5—H5C0.9800
P3—N5i1.554 (4)C6—H6A0.9800
P3—O21.578 (3)C6—H6B0.9800
P3—N7i1.594 (4)C6—H6C0.9800
N1—C11.341 (6)C8—C91.338 (8)
N1—C21.365 (6)C8—H80.9500
N1—C41.454 (7)C9—H90.9500
N2—C11.348 (6)C10—C111.448 (8)
N2—C31.374 (6)C10—H10A0.9900
N2—C61.475 (7)C10—H10B0.9900
N3—C71.345 (6)C11—H11A0.9800
N3—C81.385 (6)C11—H11B0.9800
N3—C101.465 (6)C11—H11C0.9800
N4—C71.347 (6)C12—H12A0.9800
N4—C91.374 (6)C12—H12B0.9800
N4—C121.464 (6)C12—H12C0.9800
C1—Ag—C7178.72 (19)C5—C4—H4A109.4
O1—P1—N5116.2 (2)N1—C4—H4A109.4
O1—P1—N6113.33 (19)C5—C4—H4B109.4
N5—P1—N6112.96 (19)N1—C4—H4B109.4
O1—P1—O2104.90 (18)H4A—C4—H4B108.0
N5—P1—O2104.43 (17)C4—C5—H5A109.5
N6—P1—O2103.29 (19)C4—C5—H5B109.5
N6—P2—N7120.75 (19)H5A—C5—H5B109.5
N6—P2—Cl1108.88 (15)C4—C5—H5C109.5
N7—P2—Cl1108.31 (15)H5A—C5—H5C109.5
N6—P2—Cl2110.61 (17)H5B—C5—H5C109.5
N7—P2—Cl2107.54 (15)N2—C6—H6A109.5
Cl1—P2—Cl298.43 (7)N2—C6—H6B109.5
N5i—P3—O2113.38 (18)H6A—C6—H6B109.5
N5i—P3—N7i119.10 (19)N2—C6—H6C109.5
O2—P3—N7i109.28 (18)H6A—C6—H6C109.5
N5i—P3—Cl3109.53 (15)H6B—C6—H6C109.5
O2—P3—Cl397.59 (12)N3—C7—N4104.7 (4)
N7i—P3—Cl3105.49 (14)N3—C7—Ag127.0 (3)
P3—O2—P1126.57 (19)N4—C7—Ag128.2 (3)
C1—N1—C2111.3 (5)C9—C8—N3106.8 (4)
C1—N1—C4123.2 (4)C9—C8—H8126.6
C2—N1—C4125.5 (5)N3—C8—H8126.6
C1—N2—C3111.5 (4)C8—C9—N4106.6 (4)
C1—N2—C6124.2 (4)C8—C9—H9126.7
C3—N2—C6124.3 (4)N4—C9—H9126.7
C7—N3—C8110.6 (4)C11—C10—N3112.4 (5)
C7—N3—C10123.6 (4)C11—C10—H10A109.1
C8—N3—C10125.7 (4)N3—C10—H10A109.1
C7—N4—C9111.2 (4)C11—C10—H10B109.1
C7—N4—C12124.6 (4)N3—C10—H10B109.1
C9—N4—C12124.2 (4)H10A—C10—H10B107.9
P3i—N5—P1124.3 (2)C10—C11—H11A109.5
P2—N6—P1123.1 (2)C10—C11—H11B109.5
P2—N7—P3i118.6 (2)H11A—C11—H11B109.5
N1—C1—N2103.8 (4)C10—C11—H11C109.5
N1—C1—Ag127.0 (4)H11A—C11—H11C109.5
N2—C1—Ag129.2 (4)H11B—C11—H11C109.5
C3—C2—N1107.4 (5)N4—C12—H12A109.5
C3—C2—H2126.3N4—C12—H12B109.5
N1—C2—H2126.3H12A—C12—H12B109.5
C2—C3—N2105.9 (4)N4—C12—H12C109.5
C2—C3—H3127.0H12A—C12—H12C109.5
N2—C3—H3127.0H12B—C12—H12C109.5
C5—C4—N1111.3 (5)
N5i—P3—O2—P147.2 (3)C7—Ag—C1—N1−47 (9)
N7i—P3—O2—P1−88.3 (3)C7—Ag—C1—N2133 (8)
Cl3—P3—O2—P1162.3 (2)C1—N1—C2—C3−0.3 (7)
O1—P1—O2—P3136.3 (2)C4—N1—C2—C3−178.1 (5)
N5—P1—O2—P313.5 (3)N1—C2—C3—N2−0.7 (6)
N6—P1—O2—P3−104.8 (3)C1—N2—C3—C21.5 (6)
O1—P1—N5—P3i146.1 (3)C6—N2—C3—C2−179.9 (5)
N6—P1—N5—P3i12.6 (4)C1—N1—C4—C5−84.8 (7)
O2—P1—N5—P3i−98.9 (3)C2—N1—C4—C592.9 (7)
N7—P2—N6—P15.5 (4)C8—N3—C7—N40.0 (6)
Cl1—P2—N6—P1131.7 (2)C10—N3—C7—N4−177.7 (4)
Cl2—P2—N6—P1−121.2 (3)C8—N3—C7—Ag−177.6 (4)
O1—P1—N6—P2−144.9 (3)C10—N3—C7—Ag4.7 (7)
N5—P1—N6—P2−10.1 (4)C9—N4—C7—N3−0.2 (6)
O2—P1—N6—P2102.2 (3)C12—N4—C7—N3−179.0 (4)
N6—P2—N7—P3i−2.2 (4)C9—N4—C7—Ag177.5 (4)
Cl1—P2—N7—P3i−128.6 (2)C12—N4—C7—Ag−1.4 (7)
Cl2—P2—N7—P3i125.9 (2)C1—Ag—C7—N340 (9)
C2—N1—C1—N21.2 (6)C1—Ag—C7—N4−137 (8)
C4—N1—C1—N2179.1 (5)C7—N3—C8—C90.1 (6)
C2—N1—C1—Ag−178.8 (4)C10—N3—C8—C9177.7 (5)
C4—N1—C1—Ag−0.9 (7)N3—C8—C9—N4−0.2 (6)
C3—N2—C1—N1−1.6 (6)C7—N4—C9—C80.2 (6)
C6—N2—C1—N1179.8 (5)C12—N4—C9—C8179.0 (5)
C3—N2—C1—Ag178.3 (4)C7—N3—C10—C1187.5 (7)
C6—N2—C1—Ag−0.2 (8)C8—N3—C10—C11−89.9 (7)

Symmetry codes: (i) −x+1, −y+1, −z+1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2087).

References

  • Allcock, H. R. (2003). Chemistry and Applications of Polyphosphazenes, pp. 137–187. New Jersey: Wiley-Interscience.
  • Allcock, H. R., Gardener, J. E. & Smeltz, K. M. (1975). Macromolecules, 8, 36–42.
  • Bartlett, S. W., Coles, S. J., Davies, D. B., Hursthouse, M. B., İbişogˇlu, H., Kiliç, A., Shaw, R. A. & Ün, İ. (2006). Acta Cryst. B62, 321–329. [PubMed]
  • Brandt, K., van de Grampel, J. C., Meetsma, A. & Jekel, A. P. (1991). Recl Trav. Chim. Pays Bas, 110, 27–28.
  • Bruker (2001). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
  • Bruker (2007). SMART andSAINT Bruker AXS Inc., Madison, Wisconsin, USA.
  • Bullen, G. J. (1971). J. Chem. Soc. A, 1450–1453.
  • Gabler, D. G. & Haw, J. F. (1990). Inorg. Chem.29, 4018–4021.
  • Meetsma, A., van der Lee, A., Jekel, A. P., van de Grampel, J. C. & Brandt, K. (1990). Acta Cryst. C46, 909–911.
  • Murray, M., Penkett, C. J., Rillie, I. M. & Singh, G. (1994). Phosphorus, Sulfur, Silicon.93–94, 313–316.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Grampel, J. C. van de (1992). Coord. Chem. Rev.112, 247-271.

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography