Scientific paper
The Crystal Structure of bis-(^-N-ethyi-N-phenyldithiocarbamato-S,S')-b/s[(N-ethyl-N-phenyldithiocarbamato-K2S,S')zinc(II)]
Robert A. Gossagea'* and Hilary A. Jenkinsb
a Department of Chemistry & Biology, Faculty of Engineering, Architecture & Science, 350 Victoria Street, Ryerson University, Toronto, ON B4P 2R6 Canada.
b Department of Chemistry, MAX Diffraction Facility, McMaster University, 1280 Main Street West,
Hamilton, ON L8S 4L9 Canada
* Corresponding author: E-mail: gossage@ryerson.ca Fax: +1(416)979-5044
Received: 30-06-2008
Abstract
The title material crystallises in the triclinio crystal system in space group P-1 with Z = 2. The unit cell dimensions are a = 8.7365(6)À, b = 10.6009(7)À, c = 12.0210(8)À with a = 66.343(1)°, ß = 79.566(1)°, Y = 83.150(1)° and V = 1001.6(1)À3. The final R value is 0.0307 (3905 observed reflections: I >2o(I)). The compound is best described as a species in which each metal atom is coordinated to two dithiocarbamato groups, one of which forms a secondary bridging interaction (through a S-atom) to a second [Zn(S2CNEtPh)2] unit. Thus, the title material is in the form of a dime-ric aggregate. This complex is compared to related materials which contain N-atoms within the dithiocarbamato ligand that are derived from secondary amines containing two different organic functionalities.
Keywords: Zinc dithiocarbamate, X-ray structure analysis, dithiolate, zinc(II), dimer
1. Introduction
The zinc dithiocarbamates (ZDTC) represent an important sub-class of the Group XII dithiolates.12 These materials have historically found application as pesticides, most notably the fungicide ZIRAM (i.e., [Zn2(S2CN Me2)4]), in addition to their widespread use as radical scavenging agents and as additives to commercial pavement asphalt. In addition, ZDTC are used in combination with high stress industrial lubricants to impart improved stability to the lubricant formulation; they can also promote the vulcanisation of rubber and act as Lewis acid frameworks in coordination chemistry.1-5 More recent investigations of ZDTC include their evaluation as potential precursors in chemical vapour deposition technology (e.g., ZnS thin film production)6-9 and in other materials science applica-tions.10 Although there are a number of complexes of general formula [Zn(S2CNRR')2]n found in the CCDC database, relatively few of these are of the class where R ^ R'. In this report, we detail the structural characterisation of
one of these derivatives, viz. bis-(^-N-ethyl-N-phenyldit-hiocarbamato-S,S')-bis[(N-ethyl-N-phenyl-dithiocarba-mato-K2S, S')zinc(II)] (1).
2. Experimental
2. 1. General
Compound 1 (purity > 98%) was obtained commercially from TCI Chemicals Co. Ltd. of Tokyo, Japan. Crystals of the title material that were suitable for X-ray diffraction work were obtained by suspending crude 1 (~10 g) in 140 mL of petroleum spirit (bp 90-120 °C). The mixture was heated on a steam bath to a temperature of about 80 °C and the solids quickly filtered off from the supernatant solution. This procedure was repeated four times. On cooling, the filtrates yielded copious quantities of well-formed crystals. One such crystal, with approximate dimensions 0.05 X 0.11 x 0.20 mm3, was selected and mounted on a glass fibre for characterisation by X-ray diffraction.
2. 2. X-ray diffraction study of 1		Zn(1)-S(1) Zn(1)-S(3)	2.4437(7) 2.7512(7)
		S(1)-C(1)	1.709(3)
Data were collected at -50 °C on a Bruker-AXS		S(2)-C(1)	1.725(2)
SMART 1K CCD diffractometer, and were processed us-		S(3)-C(11)	1.736(3)
ing SMART/SAINT V5.059; a semi-empirical absorption		S(4)-C(11)	1.718(2)
correction was applied using SADABS. The structure was		N(1)-C(1)	1.338(3)
solved with SHELXS-97 using the heavy atom method		N(1)-C(4)	1.443(3)
with full-matrix least squares refinement on F2 using		N(1)-C(2)	1.497(6)
SHELXL-97.10-15 All non-hydrogen atoms were refined		N(1)-C(2')	1.620(7)
anisotropically and H atoms were refined as riding on		N(2)-C(11)	1.328(3)
their constituent atoms. An approximate 60:40 disorder in		N(2)-C(14)	1.447(3)
the ethyl group bound to N1 was modelled with free va-		N(2)-C(12)	1.482(3)
riables on the occupancies of each atom; the major com-		C(2)-C(3) C(2')-C(3')	1.512(7) 1.486(9)
ponent constituted 61.2%. In the final cycles of refine-		C(4)-C(5)	1.377(4)
ment, R1 = 3.07% and wR	2 = 5.88%; the largest residual	C(4)-C(9)	1.381(4)
peak at 0.298 A3 was associated with Zn1. Details of the		C(5)-C(6)	1.380(4)
experimental parameters can be found in Tables 1 and 2.16		C(6)-C(7)	1.372(4)
		C(7)-C(8)	1.370(4)
Table 1. Crystal data, data collection and structure refinement for compound 1.		C(8)-C(9) C(12)-C(13)	1.376(4) 1.516(3)
Empirical formula	C18H18N2S4Zn	C(14)-C(19)	1.373(3)
M	455.95	C(14)-C(15)	1.382(3)
r Wavelength	0.71073 A	C(15)-C(16)	1.368(3)
Crystal system	Triclinic	C(16)-C(17)	1.377(4)
Space group a (A)	P-1, No. 2	C(17)-C(18)	1.379(4)
	8.7365(6)	C(18)-C(19)	1.376(4)
b (A)	10.6009(7)		
c (A)	12.0210(8)	S(4)-Zn(1)-S(2)	136.18(3)
«(°)	66.343(1)	S(4)-Zn(1)-S(3)#1	104.11(3)
ß(°)	79.566(1)	S(2)-Zn(1)-S(3)#1	117.50(3)
y(°)	83.150(1)	S(4)-Zn(1)-S(1)	107.35(3)
y (A3)	1001.6(1)	S(2)-Zn(1)-S(1)	75.50(2)
Z	2	S(3)#1-Zn(1)-S(1)	105.31(2)
p (Mg m-3)	1.519 (calc.)	S(4)-Zn(1)-S(3)	70.60(2)
T (K)	223(2) K	S(2)-Zn(1)-S(3)	95.99(2)
Absorption coefficient	1.647 mm-1	S(3)#1-Zn(1)-S(3)	88.86(2)
F(000)	472	S(1)-Zn(1)-S(3)	165.61(2)
0 range for data collection	1.87 to 26.00°.	C(1)-S(1)-Zn(1) C(1)-S(2)-Zn(1)	82.12(9) 84.21(9)
Index ranges	-10<=h<=10; -13<=k<=13;	C(11)-S(3)-Zn(1)#1	100.95(8)
	-14<=l<=14	C(11)-S(3)-Zn(1)	78.78(8)
Reflections collected	8090	Zn(1)#1-S(3)-Zn(1)	91.14(2)
Independent reflections	3905 [Rint = 0.0218]	C(11)-S(4)-Zn(1)	91.72(9)
Completeness to	99.4 %	C(1)-N(1)-C(4)	122.8(2)
theta = 25.00°		C(1)-N(1)-C(2)	124.3(3)
Absorption correction	Semi-empirical from equivalents	C(4)-N(1)-C(2)	110.9(3)
Data / restraints / parameters	3905 / 0 / 242	C(1)-N(1)-C(2')	112.8(3)
Goodness-of-fit on F2	0.918	C(4)-N(1)-C(2')	122.7(2)
Final R indices [I>2o(/)]	R1 = 0.0307, wR2 = 0.0588	C(2)-N(1)-C(2')	30.4(2)
R indices (all data)	R1 = 0.0534, wR2 = 0.0627	C(11)-N(2)-C(14)	121.1(2)
Largest diff. peak and hole (e.A-3)	0.298 and -0.214	C(11)-N(2)-C(12)	123.0(2)
		C(14)-N(2)-C(12) N(1)-C(1)-S(1) N(1)-C(1)-S(2)	115.9(2) 121.2(2) 120.7(2)
Table 2. Selected Bond Lengths (A) and Angles (°) for Compound 1.		S(1)-C(1)-S(2)	118.1(2)
		N(1)-C(2)-C(3)	103.7(4)
Zn(1)-S(4)	2.3516(7)	C(3')-C(2')-N(1)	102.6(6)
Zn(1)-S(2)	2.3655(7)	C(5)-C(4)-C(9)	120.5(3)
Zn(1)-S(3)#1	2.4033(7)	C(5)-C(4)-N(1)	119.6(3)
C(9)-C(4)-N(1)	119.9(3)
C(4)-C(5)-C(6)	119.2(3)
C(7)-C(6)-C(5)	120.6(3)
C(8)-C(7)-C(6)	119.7(3)
C(7)-C(8)-C(9)	120.6(3)
C(8)-C(9)-C(4)	119.4(3)
N(2)-C(11)-S(4)	120.94(19)
N(2)-C(11)-S(3)	120.67(18)
S(4)-C(11)-S(3)	118.35(15)
N(2)-C(12)-C(13)	112.5(2)
C(19)-C(14)-C(15)	120.1(3)
C(19)-C(14)-N(2)	120.4(2)
C(15)-C(14)-N(2)	119.4(2)
C(16)-C(15)-C(14)	119.8(3)
C(15)-C(16)-C(17)	120.6(3)
C(16)-C(17)-C(18)	119.3(3)
C(19)-C(18)-C(17)	120.5(3)
C(14)-C(19)-C(18)	119.6(3)
Symmetry transformations used to generate equivalent atoms: #1 -x + 1,-y,-z
3. Results and Discussion
A schematic representation of the title complex appears in Figure 1 and an ORTEP version, with select atoms and atomic labelling, appears in Figure 2.
Each Zn atom is coordinated by two chelating dit-hiocarbamate units; one of these forms a secondary bonding interaction with a second [Zn(S2CNRR')2] moiety via S3. This forms a dimeric aggregate situated on a centre of crystallographic inversion. The chelating S2CN(Et)Ph groups form a highly distorted square pyramidal array around the metal atom with one long (~2.75 À) and three short (between ~2.35-2.45 À) Zn-S bonds, where the smallest angle is between S4-Zn1-S3 at 70.60(2)°; the coordination sphere surrounding the Zn1 atom is completed by a further bridging Zn1-S3' bond (~2.40 À). Within each moiety there is a distinct angle between the planes formed by S1-C1-S2 and S3-C11-S4 of 40.59(5)° and a twist of 49.57(3)° between S1-Zn1-S4 and S2-Zn1-S3. The coordination motif can be best described as being midway between trigonal bipyramidal and square pyramidal (t = 0.491).17 Such a bonding pattern is also seen for related complexes such as [Zn2(S2CN{R} Et)4], (R = Et, ^Pr, nBu or Cy),18-21 [Zn2(S2CN{^h}Me)4],22 [Zn2(S2CN{R}H)4] (R = Et, nPr, ^Pr or n^u),23 [Zn2(S2CN {CH2CH20H}R)4] (R = Me or Et)24 and [Zn2(S2CN{Ph}
{C14H29})4].25
The core of the molecule of 1 adopts a "twisted chair" conformation in relation to the eight-membered [-S-M-S-C-]2 (M = Zn, Cd or Hg) ring system. Therefore, compound 1 is a representative of what has been refer-
Figure 1. Schematic representation of the observed form of compound 1 and a possible anti-isomer.
Figure 2. ORTEP representation of a molecule of 1 with selected atomic numbering; ethyl groups have been removed for clarity.
red to by Tiekink, in his seminal review on the structural properties of Group XII dithiolates, as Dithiolate Bonding Motif Type HI? This motif is also found in the complexes referred to above and is characterised by the observation that the bridging dithiolates are found on opposite sides of the eight-membered ring.18-25 Symmetry restrictions also impose that the molecule can be described as the syn-iso-mer, in relation to the orientation of opposing Ph or Et groups, of a possible syn- or anti-conformational pair (Figure 1). This syn isomeric form is also displayed in, for example, the complexes of general formula [Zn2(S2CN {R}H)4] where R = Et, nPr, 'Pr or nBu).23
Although the Cd analogue of 1 does not appear to have been structurally characterised, a Hg2+ derivative containing the [S2CN(Et)Ph] anion has been reported.26-28 The complex [Hg(S2CN{Et}Ph)2]2 (2) is not however, iso-structural to the Zn material described here.28 Complex 2 contains a metal atom in which the coordination environment is distinctly more pronounced towards square pyramidal (t = 0.201)17 although a similar twisted chair conformation of the [-S-Hg-S-C-]2 ring system is clearly visible (Figure 3). This distortion precludes the establishment of a definitive syn or anti structural isomer in contrast to that observed for 1.
Figure 3. Mercury representations of Hg compound 2 (left) and Zn derivative 1 (right).
4. Conclusions
The solid-state characterisation of [Zn(S2CN{Et} Ph)2]n (1) by single crystal X-ray diffraction reveals the compound to be a dimeric aggregate (i.e. n = 2) that may be described as the syn-isomer in relation to the orientation of ethyl and phenyl groups. In addition, compound 1 is a member of Tiekink's Dithiolate Bonding Motif Type III.2 The title material is also shown not to be isostructural with the Hg analogue reported previously.26-28
5. Acknowledgement
The authors are indebted to the support of NSERC (Canada), McMaster University and Ryerson University.
6. References
1.	M. J. Cox, E. R. T. Tiekink, Rev. Inorg. Chem. 1997, 17, 1-23.
2.	E. R. T. Tiekink, CrystEngCommun. 2003, 5, 101-113.
3.	G. D. Thorn, R. A. Ludwig: The Thiocarbamates and Related Compounds, Elsevier, Amsterdam, 1962.
4.	A. Decken, C. R. Eisnor, R. A. Gossage, S. M. Jackson, Inorg. Chim. Acta 2006, 359, 1743-1753.
5.	R. A. Gossage, H. A. Jenkins, Anal. Sci. 2008, 24, x155-x156.
6.	D. Zeng, M. J. Hampden-Smith, T. M. Alam, A. L. Rheingold, Polyhedron 1994, 13, 2715-2730.
7.	P. O'Brien, R. Nomura, J. Mater. Chem. 1995, 5, 1761-1773.
8.	L. V. Zavyalova, A. K. Savin, G. S. Svechnikov, Displays 1997, 18, 73-78.
9.	H. Cui, R. D. Pike, R. Kershaw, K. Dwight, A. Wold, J. Solid State Chem. 1992, 101, 115-118.
10.	For example: P. R. A. Webber, M. G. B. Drew, R. Hibbert, P. D. Beer, Dalton Trans. 2004, 1127-1135 and references therein.
11.	SMART V5.03. Program for Data Collection on Area Detectors, Bruker AXS Inc., 5465 E. Cheryl Parkway, Madison WI 53711-5373 U.S.A.
12.	SMART V5.03. Program for Reduction of Area Detector Data, Bruker AXS Inc., 5465 E. Cheryl Parkway, Madison WI 53711-5373 U.S.A.
13.	G. M. Sheldrick, SADABS: Program for Absorption Correction of Area Detectors, Bruker AXS Inc., 5465 E. Cheryl Parkway, Madison WI 53711-5373 U.S.A.
14.	G. M. Sheldrick, 1997, SHELXL-97: Program for Crystal Structure Refinement, Institüt für Anorganische Chemie der Universität, Tammanstrasse 4, D-3400 Göttingen, Germany.
15.	G. M. Sheldrick, 1990, SHELXS: Program for Crystal Structure Solution, Institüt für Anorganische Chemie der Universität, Tammanstrasse 4, D-3400 Göttingen, Germany.
16.	The CCDC number for complex 1 is 693033. These data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-quest/cif.
17.	A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn, G. C. Verschoor, J. Chem. Soc., Dalton Trans. 1984, 1349-1356.
18.	E. R. T. Tiekink, Z. Kristallogr. - New Cryst. Struct. 2000, 215, 445-446.
19.	I. Baba, Y. Farina, A. H. Othman, I. A. Razak, H.-K. Fun, S. W. Ng, Acta Cryst. E 2001, 57, m51-m52.
20.	I. Baba, Y. Farina, K. Kassim, A. H. Othman, I. A. Razak, H.K. Fun, S. W. Ng, Acta Cryst. E2001, 57, m55-m56.
21.	M. J. Cox, E. R. T. Tiekink, Z. Kristallogr. 1999, 214, 184-190.
22.	I. Baba, L. H. Lee, Y. Farina, A. H. Othman, A. R. Ibrahim, A. Usman, H.-K. Fun, S. W. Ng, Acta Cryst. E 2002, 58, m744-m745.
23.	M. Motevalli, P. O'Brien, J. R. Walsh, I. M. Watson, Polyhedron 1996, 15, 2801-2808.
24.	R. E. Benson, C. A. Ellis, C. E. Lewis, E. R. T. Tiekink, CrystEngCommun. 2007, 9, 930-940.
25.	C.-M. Jia, W.-B. Yuan, Q. Lin, Q. Zhang, J. Pei, Acta Cryst. E 2009, 65, m471.
26.	D. Ondrusova, E. Jóna, M. Koman, P. Simon, Chem. Listy 2003, 97, 649.
27.	D. Ondrusova, M. Pajtasova, E. Jóna, M. Koman, Sol. State Phenomena 2003, 90-91, 383-388.
28.	CCDC #297144 (code YEDQEE): monoclinic, P21/c (No. 14); Z = 4.	1
Povzetek
Opisana spojina kristalizira v triklinski prostorski skupini P-1 z osnovno celico a = 8.7365(6)À, b = 10.6009(7)À, c = 12.0210(8)À, a = 66.3430(10)°, ß = 79.5660(10)°, Y = 83.1500(10)° in V = 1001.56(12)À3, Z = 2, R = 0.0209 (3522 opaženih uklonov, I >2o(/)). V strukturi je kovinski atom koordiniran z dvema ditiokarbamatnima skupinama, ena od obeh ditiokarbamatnih skupin daje sekundarno interakcijo (preko S-atoma) do druge [Zn(S2CNEtPh)2] enote z nastankom dimere. Strukturo spojine primerjamo s podobno spojino z dušikovim atomom v ditiokarbamatnem ligandu.