Reaction of carbon disulfide with nickel(i1)-amine complexes

Transcription

1 Reaction of carbon disulfide with nickel(i1)-amine complexes B. JACK MCCORMICK AND ROY I. KAPLAN Department of Cl~emistry, West Virginia Ut~iversity, Morgantown, W. Ya Received January 27, 1970 Can. J. Chem. Downloaded from by on 04/06/18 The reaction of carbon disulfide with a variety of nickel(i1)-amine complexes has been carried out. It has been found that dithiocarbamate complexes are readily formed under the proper conditions, and the synthetic procedures presented provide a convenient and direct route to such compounds. Complexes having hydroxyl and mercaptide groups in addition to amine groups have been found to give exclusively dithiocarbamate complexes, rather than xanthates or trithiocarbonates. The infrared and optical spectra of the complexes have been measured and are discussed in terms of the proposed structures of the complexes. Canadian Journal of Chemistry, 48, 1876 (1970) Introduction While N,N-dialkyldithiocarbamate complexes of nickel(i1) and other transition metal ions have been known for many years (I), most of them have been prepared by metathetical reactions between a salt of a transition metal and that of a N,N-dialkyldithiocarbamic acid. Very recently there have been a few reports on the preparation of dithiocarbamate complexes by carbon disulfide insertion reactions, viz. Bradley and Gitlitz (2, 3) have made use of the carbon disulfide insertion reaction to prepare a number of interesting complexes of early transition metals. In a review (4) Lappert has summarized the results of studies concerned with the insertion of carbon disulfide into several types of metal-nitrogen bonds. In view of the possible synthetic utility of carbon disulfide insertion reactions, we have investigated the reaction of CS, with a variety of nickel(i1)-amine complexes involving: (I), a monodentate amine; (11), bidentate primary amines; (111), bidentate amines in which one donor nitrogen atom is in a pyridine ring; (IV), bidentate amines containing hydroxyl and mercaptide functional groups; and (V), a tridentate amine. Six of the complexes prepared have not been reported previously. Studies of selected properties of the complexes have been made, and the results are discussed in relation to the structures of the complexes. Experimental All of the amine complexes were prepared by known or modifications of known procedures (5). Dimethyl sulfoxide was distilled under nitrogen before use, and solution spectra were measured in Fisher "Spectroanalyzed" solvents. Reaction Procedures Several solvents for the insertion reactions were examined. Among these were water, methanol, ethanol, acetone, and N,N-dimethylformamide. While the reactions did proceed in these solvents, they were very slow, requiring 3 to 4 days. In many cases the slow rate of reaction undoubtedly was due to the lack of mutual solubility of the metal amine and carbon disulfide in the solvent. The most suitable solvent found was dimethyl sulfoxide (DMSO), in which most of the reactions were complete in 30 min. The reactions were done under an atmosphere of N,, and the reaction products were not exposed to air until they had been partially dried. In general, the reactions were carried out by dissolving and/or suspending 0.05 mole of the amine complex in 50 ml of DMSO, to which was added 0.5 mole of carbon disulfide dissolved in loml of DMSO. Typically the solutions underwent a series of color changes, and after 30 min, 250 ml of water was added to the reaction mixture, whereupon a precipitate formed immediately. The precipitate was separated by filtration, washed with 500 ml of warm water and 200 ml of methanol, dried in a stream of nitrogen, and then dried at 64' in vacuo over P4OI0. The yields were high in all cases except system Ia. The reaction with bis(2-mercaptoethylamine)nickel(ii) proceeded very slowly at room temperature owing to the insolubility of the complex in DMSO, and the above general procedure was modified in that the reaction was carried out in a sealed, heavy walled glass tube at 70". Under these conditions the reaction was complete in 6 h. The analytical sample was recrystallized from DMSO. Special procedures also were necessary for the reaction of dichloro(l,l,7,7-tetraethyldiethylenetriamine)ni~kel(ii) with carbon disulfide. In this reaction, 0.03 mole of the amine complex in 50 ml of absolute ethanol was treated with 0.03 mole of CS,. The solution quickly turned from a deep red to a bright green color. After 20 min a green precipitate was filtered off, washed with ethanol, and air dried. Recrystallization from absolute ethanol followed by drying over P4OlO provided an analytically pure sample. Given in Table 1 are the systems studied and the products formed from each system. The systems are

2 McCORMICK AND KAPLAN: REACTION OF CS2 AND Ni(I1)-AMINE COMPLEXES

3 1878 CANADIAN JOURNAL OF CHEMISTRY. VOL. 48, 1970 Can. J. Chem. Downloaded from by on 04/06/18 - TABLE 2 Analytical data for dithiocarbamate complexes Carbon Hydrogen Nitrogen Sulfur Nickel Product* Calcd. Found Calcd. Found Calcd. Found Calcd. Found Calcd. Found IIa IIb IIc IId IIIa IIIb IVa IVb Va *The product numbers correspond to the systems and reactions given in Table 1. designated by numbers which correspond to those given in the Introduction for the various types of amines. Elemental analyses for all of the compounds are given in Table 2. Carbon, hydrogen, nitrogen, and sulfur analyses were done by Galbraith Laboratories, Knoxville, Tenn., but the nickel analyses were done in our laboratory by conductometric titrations with EDTA (5). Measurements Infrared spectra were recorded with Beckman IR-8 and IR-12 spectrometers using the Nujol mull technique. Solution spectra were measured with a Cary Model 14 Spectrophotometer; diffuse reflectance spectra were measured with the same instrument and a Model 1411 reflectance attachment. The proton nuclear magnetic resonance (n.m.r.) spectrum was obtained with a Varian Model HA-60 Spectrometer using TMS as a reference. Spectral data are summarized in Table 3. Results and Discussion General Aspects of Reactions Reaction of carbon disulfide with amine complexes of nickel(i1) provides a direct and convenient route to nickel(i1) dithiocarbamate complexes. This technique also should be suitable for the preparation of complexes of other transition metals. In many cases it is synthetically advantageous to use the direct method rather than a metathetical reaction. since the latter procedure requires the preparation of a dithiocarbamate salt, which frequently is unstable or difficult to prepare and isolate. While the detailed mechanism is not known. two mechanistic aspects of the reactions deserve comment. First, there is some indication that DMSO serves as a reactant, as well as a solvent. In all cases the initial product from the reactions is soluble in DMSO, and the addition of water is required for the precipitation of the desired complex. However, in several cases the complex precipitated is not soluble in DMSO. This may indicate that the initial species formed is a mixed ligand complex involving coordinated DMSO as well as dithiocarbamate. The second point concerns the fate of the proton displaced from the amine during the course of the reaction. In systems Ia through IVa, the protons, no doubt, react with excess amine displaced during the reaction, viz. R = alkyl, hydrogen In the case of Ni(mea), and Ni(tedt)Cl,, basic sites are maintained on the coordinated dithiocarbamate which accommodate the displaced protons. Specific Reactions, Properties, and Structures la. The reaction of carbon disulfide with N~(NH,),'+ is, in principle, the most simple system studied, and it was established from infrared studies that Ni(S,CNH,), is formed. However, the product obtained was not pure. This finding is not surprising since dithiocarbamic acid, its salts, and complexes are not stable (1). IIa-IId. The four starting complexes in this group involve bidentate diamine ligands, and there are two conceivable types of reaction products. Reaction can occur at one amine group of a given ligand, with the released proton reacting with the remaining amine group to give a zwitterion, or both amine groups can react to give a bisdithiocarbamate. Ethylenediamine forms a monodithiocarbamate zwitterion in the absence of added base (6) and a bisdithiocarbamate in the presence of sodium hydroxide (7). In the four cases studied here, bisdithiocarbamate

4 McCORMICK AND KAPLAN: REACTION OF CS2 AND Ni(I0-AMINE COMPLEXES 1879 TABLE 3 Infrared and electronic spectral data* - Vm,, Compound V(C=N) Reflectance DMSOt IIa( = IIb) (127) 23.3sh 23.5(1320)sh (4520) (23000) IIc (126) 24.0sh 24.1(1530)sh (3590) (23200) IId (68) 22.6sh 23.3(1620)sh (5560) (28200) IIIa (85) (234) 23.4 sh 23.8 (1400) sh IIIb (113) (220) 24.4 sh 23.8 (1420) sh IVa sh 16.1 (68) 23.5(1390)sh I (3860) *Electronic data is in kilokaysers (kk); sh ~ndicates a shoulder. Infrared data is in cm-1.?extinction coefficients (1 mole-' cm-1) are given in parentheses. ligands are formed, and the resulting insoluble, green complexes are undoubtedly polymeric, as indicated in Table 1. If zwitterionic ligands were involved, the complexes should show a degree of solubility in water, as well as infrared frequencies characteristic of quaternary ammonium groups. Similar complexes prepared by metathetical reactions have been reported previously (8). The structures given in Table 1 are idealized in the sense that only chelating dithiocarbamate groups are shown. Bridging ligands may be important, but such detailed structural features cannot be ascertained at this time. Aside from their polymeric nature, the complexes appear to be very similar to the many nickel(i1) dithio- carbamates that have been previously studied. The complexes are diamagnetic and show a characteristic (9) C=N stretching frequency in the cm-i region. The electronic spectra, as given in Table 3, are identical to that reported previously by Jorgensen (10) for bis(n,n-diethyldithiocarbamato)nickel(ii), except that the band at ca. 21 kk is not resolved. IIIa,b. In these chelating diamines there is one amine group that can react with carbon disulfide and one ring nitrogen atom that is not expected to enter into reaction with carbon disulfide. It was of interest to determine whether the pyridine nitrogen atom would remain coordinated after the primary amine had undergone reaction with carbon disulfide. The results indicate that the pyridine moiety is displaced from the coordination sphere by the dithiocarbamate formed from the primary amine group to give the usual type of dithiocarbamate complex. In contrast to the polymeric complexes formed in system 11, these green, diamagnetic monomers are somewhat soluble in a variety of polar organic solvents. The magnitude of the C=N stretching frequency suggests that double bond character increases in the (S,)C-N bond (11) in going from system I1 to system 111. Electronic spectra measured at room temperature are identical to those that have been reported previously (10) for nickel(i1) dithiocarbamates. Since Coucouvanis and Fackler (11) have shown that certain nickel(i1) dithiocarbamates form adducts at low temperatures with nitrogenous bases, it was of interest to determine whether the present complexes enter into intra- or inter-molecular association with the uncoordinated pyridine groups. That such association can take place in solution with the concomitant formation of pseudo-octahedral nickel(i1) complexes was indicated by low temperature spectral studies. An acetone solution of system IIIb at room temperature exhibited the same absorption bands as those given in Table 3. As the solution was cooled to - 12", the color became lighter and a weak absorption band appeared at 10.2 kk. Further cooling to -80" resulted in a very pale green solution (no precipitation) with a moderately intense band at 10.2 kk. These spectral changes are in close agreement with those reported by Coucouvanis and Fackler (10) for bis(n,n-diethyldithiocarbamato)nickel(ii) in pyridine at temperatures from -80 to 20".

5 1880 CANADIAN JOURNAL OF CHEMISTRY. VOL. 48, 1970 IVa. Ethanolamine, HOCH2CH2NH2, reacts presence of a sulfhydryl group was provided by with carbon disulfide under room conditions to an n.m.r. study in DMSO-d,, where a resonance provide the dithiocarbamate rather than the due to the proton on the sulfur atom was located xanthate, HS2COCH2CH2NH2, which goes to at 6.60 T. 2-mercaptooxazoline on standing (12). Hence, it Va. The tedt complex reacted quite readily to was of interest to determine the course of reaction give a complex of a positively charged dithioof carbon disulfide with a coordinated amine carbamate ligand. This complex, prepared by an containing an -OH group. In principle, it is alternate route, has been discussed elsewhere (15). possible to form a dithiocarbamate, a xanthate, or a mixed dithiocarbamate-xanthate complex. This work was supported by the National Science ~h~ results indicate that reaction takes place Foundation through Grant NO. GP-6671 and through a grant that supported the purchase of the IR-12 Specexclusively at the nitrogen atoms to provide a trometer. polymeric complex having the structure shown in Table 1. The color, solubility, magnetic, and 1. G. D. THORN and R. A. LUDWIG. The dithioelectronic spectral properties of the complex were carbamates and related compounds. Elsevier Publ. essentially identical to those shown by the com- Co., New York D. C. BRADLEY and M. GITLITZ. Chem. plexes in Group 11. The CLN and OH stretching Commun. 289 (1965). frequencies were located at 1520 and 3375 cm-l, 3. D. C. BRADLEY and M. H. GITLITZ. J. Chem. Soc. A, 1152 (1969). and there were no bands in the 4. M. F. LAPPERT. Advances in organometallic cm-' region that could be attributed chemistry. Edited by F. G. A. Stone and R. West. Academic Press, Inc., New York. pp a 'anthate (I3)' The was 5. R. I. KAPLAN. Ph.D. Thesis, West Virginia Universtable and did not decompose to provide a sity, Morgantown, West Virginia mercaptooxazoline. 6. A. W. HOFMAN. Ber. 5, 240 (1872). 7' IVb. 2-Mercaptoethylamine is known to react A' Y. YAKUBoVICH and V. A. KLIMovA. J. Chem. U.S.S.R., 9, 1777 (1939). with carbon disulfide to give the trithiocarbonate 8. L. c. A. THOMPSON and R. O. MOYER. J. Inorg. zwitterion (14), but it was found in this work that Chem (1965). 9. J. CHATT, L. A. DUNCANSON, and L. M. VENANZI. coordinated mea reacts to give the dithiocar- Suomen Kem. B29, 75 (1956). bamate. Upon displacement from the coordina- 10. C. K. JORGENSEN. J. Inorg. Nucl. Chem. 24, 1571 (1962). sphere the mercapto becomes 11. D. COUCOUVANIS and J. P. FACKLER, JR. Inorg. protonated to provide a monomer of the type Chem. 6,2047 (1967). shown,in Table 1. This reaction represents a 12. P. G. SERGEEV and S. N. IVANOVA. J. Gen. Chem. U.S.S.R., 7, distinct example of the mediation of an organic 1495 (1937). 13. G. W. WATT and J. MCCORMICK. Spectrochim. reaction by a metal ion. Complex IVb is green, Acta, 21, 753 (1965). slightly soluble in polar organic solvents, and l4 ~ p fii, k ~ ~ ~ i and ~ J- MICKLES. ~ 6 diamagnetic. CzN and weak S-H 15. B. J. MCCORMICK, B. P. STORMER, and R. I. KAPLAN. stretching frequencies were found at 1502 and Inorg. Chem. 8, 2522 (1969) cm-', respectively. Further evidence for the