Cobalt(II) mercury tetrathiocyanate complexes with Lewis bases—II

J. inorg, nucl. Chem., 1977, Vol. 39, pp. 683--685. Pergamon Press. Printed in Great Britain

COBALT(II) MERCURY TETRATHIOCYANATE COMPLEXES WITH LEWIS BASESmlI R. MAKHIJA and R. RIVEST D~partement de chimie, Universit6 de Montr6al, C.P. 6210, Succursale "A", Montr6al, Qu6bec H3C3V1

(Received 19 July 1976) Abstract--Eleven new complexes have been synthetized between tetrahydrofuran diadduct of CoHg(SCN)4with a variety of ligand molecules, 1.2 dimethoxyethane DME, tetramethylethylenediamine TMen, 2-amino-pyridine 2NH2-py, 3-amino-pyridine 3-NH2-py, 3-cyanopyfidine 3--CN-py, NN dimethylsulfoxide DMSO and hexamethylphosphoramide HMPA, three picolines (methylpyridines) 2-pic, 3-pic and 4-pic. The complexes obtained were of the type CoHg(SCN),.L, where L = DME TMen and 2-pic, CoHg (SCN),.2L where L = 3-pic, 2-NH:-py, 3-NH2-py, 3-CN-py, DMSO and HMPA, CoHg(SCN).3L where L = 4-pic and CoHg (SCNh.4L where L = 4-NH2-py. The complexes are yellow to pink except for the HMPA one which is blue and in all the new complexes, Co(II) is octahedral except for the HMPA one, where it is tetrahedral. INTRODUCTION In our earlier publications, we have synthetized and characterized complexes of MHg(SCN)4.2THF (M= Fe 2., Co 2÷, Ni 2+, Cu 2+, Zn 2÷ and Cd 2÷) with various ligand molecules[l-3]. The results showed that the complexes obtained are one of three types based upon the role of the - S C N - groups in the complex: type one in which they are bridging, type two in which they are terminal only and type three in which they are both bridging and terminal. The present work was initiated to study the reaction of CoHg(SCN)4.2 THF with a variety of ligands in order to see if the particular geometry of the ligands would lead to type one, two or three as defined above. It was also of interest to determine the coordination number of Co(ll) and Hg(ll) in those complexes. EXPERIMENTAL Materials, manipulations, synthesis of the complexes and physical measurements were essentially the same as discussed earlier[l-2]. The new complexes were analyzed for C, H and N by Chemalytics Inc. and Galbralth Laboratories Inc. Mercury and Sulphur were analyzed in this laboratory, mercury as HgS and sulphur as BaSO4. The analytical results are shown in Table 1. RESULTS AND DISCUSSION

The reaction of the tetrahydrofuran diadduct of CoHg(SCN)4.2THF with the ligand molecules used lead to adducts insoluble in common organic solvents, e.g. methanol, ethanol, dichloromethane, chloroform, carbon-

tetrachloride, benzene, hexane, acetone, ethylacetate and nitromethane. These are yellow to pink solids, nonmelting, which decompose on mild heating or long exposure to moist air. Molecular weights, conductance and solution spectra measurements could not be made due to insolubility. Electronic spectra of these compounds in Nujol mulls, although, of low intensity are reported in Table 2. The IR spectral results and their assignments are shown in Table 3. The position and nature of CN stretching, C-S stretching and -NCS bending modes suggest that fourNCS-groups are bridged between the cobalt and mercury atoms [4-7]. The strong C-O-C stretching modes due to coordinated tetrahydrofuran are replaced by those of the ligand used. The absorption bands in the ranges 21202145 cm -1, 730-760 cm -~ and 448-480 cm -! are assigned to CN and C-S stretching and -NCS bending modes respectively. These ranges are typical of the bridged thiocyanates [4]. IR spectra o[ CoHg(SCNh'(3-CN-py)2 and o1: CoHg(SCN)a.X aminopyridines. 3-cyanopyridine molecule has two strong coordinating groups but due to fixed orientation in space both groups cannot coordinate to the same metal atom. As a bidentate ligand cyanopyridine can, however, coordinate to two different metals. In our complex, we observe no change in the CN stretching mode as compared to the free base indicating that the cyano group is not involved in coordination, leaving pyridine nitrogen for coordination and indicating

Table 1. Analytical results Complex

Colour

Carbon Hydrogen Nitrogen Sulphur Mercury Found Calcd. Found Calcd. Found Calcd. Found Calcd. Found Calcd.

CoHg(SCNh'2(2-NH2) CoHg(SCN),.2(3-NH2.py) CoHg(SCN)4.2(3-pic) CoHg(SCNh. 2(3--CN-py) CoHg(SCN),.2(DMSO) CoHg(SCN),.4(4--NH2.py) CoI-Ig(SCN)4.3(4-pic) CoHg(SCN),.2-pic. CoHg(SCNh-DME CoHg(SCN),.(TMen) CoI-Ig(SCN)4.2I-IMPA

Brick Red Yellow Pink Pink Pink Pink Pink Violet Pink Pink Blue

24.68 25.68 28.90 27.27 14.85 33.83 33.66 21.36 16.26 20.26 21.02

24.73 24.73 28.34 27.47 14.82 33.20 34.27 20.53 16.52 19.76 22.61

1.89 2.03 2.11 1.10 1.84 3.14 2.65 1.37 1.90 2.40 4.13 683

1.78 1.78 2.08 1.15 1.87 2.29 2.74 1.21 1.73 2.65 4.27

15.97 16.43 12.31 15.17 8.65 18.15 12.07 11.03 9.49 12.60 15.05

16.54 16.54 12.45 16.02 8.65 19.44 12.77 12.04 9.63 13.83 16.47

17.95 17.81 17.79 17.11 29.86 13.57 15.% 20.63 21.66 19.25 15.65

18.82 18.82 18.88 18.30 29.68 14.74 16.60 21.88 22.00 21.06 15.06

29.38 28.66 28.65 29.19 30.62 23.15 26.31 34.33 35.09 33.27 23.91

29.50 29.56 29.58 28.67 30.95 23.10 26.01 34.29 34.48 33.00 23.60

684

R. MAKHIJA and R. RIVEST Table 2. Electronic spectra of complexes in Nujol mulls in kK UV

Visible

43.48, 38.83, 38.09, 31.52, 29.85 43.48, 37.95, 32.26, 34.19 47.62, 38.83, 32.74 47.62, 39.37, 33.90, 26.67 46.51, 43.96, 37.73, 27.02 45.21, 38.46, 35.40, 32.00 48.78, 44.94, 42.10, 32.52, 30.77 45 45.45, 39.22, 31.50

CoHg(SCN)4.2(2-NH2.py) CoHg(SCN),.2(3-NH2.py) CoHg(SCN),.2(3-pic) CoHg(SCN),.2(3-CN.py) CoHg(SCN),.4(4-NHz-py) CoHg(SCN),.3(4-pic) CoHg(SCN)4.(2-pic) CoHg(SCN),.DME CoHg(SCN)a.TMen CoHg(SCN)4.2DMSO CoHg(SCN),'2(CH3)2N)3PO

18.87 22.22, 16.60 21.16 16.60, 16.26

Table 3. IR spectra of CoHg (SCN)4.xL in the 2500-300 cm-' region for the HCS group*

CoHg(SCNL.2(2-NH2) CoHg(SCN)4.2(3-NH2.py)

CN stretching

28 (SCN) overtones

C-S stretching

Nujol

8 NCS deformation

2120-2142 sby 2093 sh 2130 s 2083 sh

925 w 895 w 950 w 890 w 940w 924 w 900 vw 940 mw 925 w 899 w

757 mw

714 w

745 w 730 m

710 w

468 w 451 m 470 m 448 m

752 mw 741 w

716 w

759 w 739 w

716 w

922 w 898 vw 920 w 895 vw

744 mw

719 w

755 w 745 w

719 w

922 w 881 w 932 w 898 w 930 w 892 w

756 m

716 mw

757 m 750 m 768 w 737 m

--717

890 w

730 m

715 w

CoHg(SCN)4.2(3-pic)

2132 s 2082 sh

CoHg(SCNL.2(3-CN-py)

2142 s

CoHg(SCNL-4(4-NH2'py) CoHg(SCN)4.3(4-pic)

CoHg(SCNL.2-pic. CoHg(SCNL.DME CoHg(SCN)4-TMen)

CoHg(SCN)4.2HMPA

2142 sh 2121 s 2103 sh 2138 s 2095 sh 2140 s 2058 sh 2133 s 2060 sh 2135 sh 2120 vs 2105 sh 2050-2080 vs br.

467 m 449 m 474 m 466 m 454 m 463 m 450 m 462 mw 457 w 476 m 465 m 442 m 466 ms 452 m 469 m 450 m 480 mw 465 mw

Ligand 419 420 m

414 mw

418 m

---

414 m ----

414 w

Table 4. Far IR spectra of CoHg(SCN)4x L complexes Complex

x/Co-NCS

x/Co-nitrogen 220 v.s.

CoHg(SCN)4.2DMSO

234-238 m. br. 235 m. 234 m. 232 m. 232 256 s. 262 s.br. 240 s. 238-242 s.br.

CoHg(SCN)4.TMen CoHg(SCN)4.2HMPA CoHg(SCN),.2(4--CN-py)

250 w. 290-310 s.br. 254 s.

CoHg(SCN)4.(2-pic) CoHg(SCN)2.2(3-pic) CoHg(SCN)4.3(4-pic) CoHg(SCN)4.2(2-NH2-Py) CoHg(SCN),.2(3-NH2-Py) CoHg(SCN),.4(4-NH2-Py) CoHg(SCN)4.DME

Co-oxygen

x/Hg-S

224 m.

212 v.s. 212-220 s. br. 192-196 s.br. 214 s. superimposed 216 v.s. 190 m.

222 v.s. 220 v.s.

Unassigned

Unassigned 154 m. 150 m.

188 m.

156-160 w. 170 s.br. 78s. 156-166 s.br. 132 m.,75 s.

210-216 s. 228 w. 231 m.

its more basic character. The two strong absorption bands at 1585 cm -1 and 1555 cm -1 in free 3-cyanopyridine are shifted to 1595 and 1570 cm -~ respectively in the complex which are assigned to ring stretching frequencies [8]. It is very easy to distinguish coordinated pyridine from the

180 s.br. 212-216 s.br. 194 s.

172 s, 154 w. 132 s.

115 m. 74 s. 66 m, 54 m.

non-coordinated since coordination causes a positive shift of 22 cm -l of a strong band located at 1578 cm -1 in free pyridine[9]. Similarly, in the case of 2, 3 and 4 aminopyridines complexes, no change is observed in the NH2 stretching modes and positive shifts are observed in

Cobalt(II)mercury tetrathiocyanate complexeswith Lewis bases--II the ring stretching bands. In the lower region, the two bands at 631 and 778 cm -~ are observed in the free base and on complexation these bands move to 643 and 812cm -~ respectively and are assigned to C-H out of plane and ring bonding. These results confirm the fact that in these complexes it is again the -pyridine nitrogen which is involved in coordination. IR spectrum o[ CoHg(SCN)4.TMen. This complex and its free ligand (TMen) show bands in the region 830-1040cm -1 which indicate that in the free and coordinated form the base molecule probably has gauche configuration. Sweeny et al. [10], Mizushima et al. [11] and Baldwin[12] have confirmed this by IR measurements. IR spectra of 2, 3 and 4-picoline complexes. These do not show any remarkable variation upon coordination of any of the bases. The pattern of the spectra is quite unchanged on coordination, though there are small but consistent shifts of some of the bands. For example, in the 4-pic complex the strong band at 799 cm ~ is shifted to 806 cm 1. The appearance of a new band at 1030cm -l indicates that the complex is octahedral [13]. Similar shifts occur in these bands in the complexes formed by 2-pic. IR spectrum of the HMPA complex. The most interesting complex obtained was with hexamethylphosphoramide. It is blue and has a magnetic moment of 4.6 B.M. indicating that cobalt(II) is tetrahedral. The IR spectrum is quite different from those of the other compounds. The presence of a strong broad band in the 2050-2080 cm t region along with a well defined shoulder at 2105cm' indicates the thiocyanate groups to be S-bonded as well as bridged[5-7]. Similar shifts are observed for C-S stretching and -NCS bending modes as shown in Table 2. The strong absorption at 1212 cm-' in pure HMPA is shifted to a lower wave number of 1165-1180 cm -~ which is due to coordination of cobalt(II) to the oxygen atom of the ligand. Similar shifts are generally observed for metal complexes of this ligand[1416]. Furthermore, the presence of a strong absorption at 290 cm -~ has been assigned to Co-NCS for a tetrahedral case[17]. On the basis of IR spectra and magnetic moment, we postulate the following structure. [(CH3)2N]3-P-O\ / N C S \ /SCN /Co\ /Hg\ [(CH3hN]3-P-O-- - - N C S --SCN Far IR spectra Metal-isothiocyanate, metaMigand and Hg-S stretching modes are observed in the 300-100 cm-~ region. These vibrations of the tetrahedral complexes are observed at higher frequencies than the metal isothiocyanate stretching modes of corresponding polymeric or monomeric octahedral complexes [18]. The medium to strong absorption bands at 290cm -~ and 240-255cm j have been assigned to CO-NCS (tetrahedrally attached) and CONCS) octahedrally attached) respectively in our complexes. Using compounds known to be tetrahedral by X-ray single crystal studies. Forster et a/.[19] have made similar assignments for their complexes of the same type. In the region of 228-232 cm J and of 180-216 cm -~, we observe for our complexes, bands which we have tentatively assigned to metal-ligand and Hg-S stretching

685

modes. In some cases, Co-NCS (octahedral) and Coligand vibrations superimpose each other due to the broadness of these bands, making difficult a very precise assignment which, however is in good agreement with reported values. Below 180cm -~, no assignments are proposed but they are probably due to ligand-metalligand stretching, metal-ligand bending and lattice vibrations. The magnetic susceptibility measurements at room temperature show magnetic moments of 5.00 B.M. except in the case of the HMPA complex, where it is 4.6 B.M.; electronic spectra show absorption bands around 20 kK which are of very low intensity, indicating cobalt(II) to be in an octahedral state, in all but one case. On the basis of our spectral measurements, the following conclusions can be drawn. (a) Bidentate ligands act as monodentates. (b) Thiocyanate groups are bridged. (c) Co(II) has an octahedral configuration in all the complexes but the hexamethylphosphoramide one where Co(II) is tetrahedral. (d) The steric requirements of the ligands appear to determine the maximum number of ligands which can coordinate to cobalt(II). For an a-substituted pyridine, no more than two molecules of ligand can coordinate to cobalt(II). For other pyridine systems where both a-positions are free, a maximum of four ligands can coordinate to Co(II). Acknowledgement--Authors are thankful to National Research Council of Canada for providing financial assistance. REFERENCES

1. R. Makhija, LeRoy Pazdernik and R. Rivest, Can. J. Chem. 51,438 (1973). 2. R. Makhija, LeRoy Pazdernik and R. Rivest, Can. J. Chem. 51, 2987 (1973), 3. R. Makhijaand R. Rivest, Spectrochim. Acta 30A,977 (1974). 4. R. A. Bailey, S. L. Kozak, T. W. Michelesenand W. N. Mills, Coord. Chem. Rev. 6, 407 (1971). 5. P. C. H. Mitchell and R. J. P. Williams,J. Chem. Soc. 1912 (1960). 6. M. M. Chamberlainand J. C. Bailar Jr., J. Am. Chem. Soc. 81, 6412 (1959). 7. A. Sabatini and I. Bertini, lnorg. Chem. 4, 1665 (1965). 8. C. N. Rao, Chemical Absorptions o[ Infrared Spectroscopy, p. 324. Academic Press, New York (1963). 9. N. S. Gill, R. H. Nuttall, D. E. Scaife and D. W. A. Sharp, 2.. Inorg. Nucl. Chem. 18, 79 (1961). 10. D. M. Sweeny, S. Mizushima and J. V. Quagliano, J. Am. Chem. Soc. 77, 6521 (1955). 11. S. Mizushima,I. Ichishima,I. Nakagawa and J. V. Quagliano, J. Phys. Chem. 59, 293 (1955). 12. M. E. Baldwin, J. Chem. Soc. 4369 (1960). 13. D. P. Graddon and E. C. Watton, Aust. J. Chem. 18, 507 (1965). 14. J. T. Donoghueand R. S. Drago, lnorg. Chem.2, 572 (1963). 15. J. T. Donoghueand R. S. Drago, lnorg. Chem., I, 866 (1%2). 16. J. T. Donoghueand R. S. Drago, lnorg. Chem. 2, 1158(1%3). 17. D. Forster and D. M. L. Goodgame, Inorg. Chem. 4, 175 (1%5). 18. R. J. H. Clark and C. S. Williams,Spectrochim. Acta 22, 1081 (1%6). 19. J. W. Jeffery, Acta Cryst. Suppl. 6, 466 0%3).