The Preparation and Properties of l-Cyano-2,3,4-triammine(ethylenediamine)cobalt(III) Chloride

ALBERT RICHARD NORRIS Depcrrtrnent of C/~etnistry, Qrreen's University, kings to^^, Otztcrrio

Received August 2, 1973

The i.r., u.v.-visible, and p.m.r. spectral characteristics of a cyanotriammine(ethy1enediamine)cobalt- (111) chloride are described and compared to the corresponding spectral characteristics of the related compounds cis-[Coen2NH3CW]CI2, trans-[CoenzNH3CN]C12.H20, and [Co(NH3),CN]C12. Evidence is presented to support the formulation of the [Coen(NH3),CN]CI2 complex as a 1-cyano-2,3,4-triam- mine(ethylenediamine)cobalt(III) chloride.

Les caractiristiques spectrales du chlorure de cyanotriammine (Cthyltnediamine) cobalt(II1) obtenues en i.r., en u.v.-visible et en r.m.p. sont dicrites et compartes aux caracteristiques spectrales correspon- dantes des composts apparentb, cis-[Coen2NH3CN]C12, trans-[Coen2NH3CN]CI2.H20 et [Co(NH,),- CN]C12. On presente des preuves visant i demontrer que la formulation du complexe [Coen(NH,),CN]Cl2 correspond au chlorure de cyano-1 triammine-2,3,4 (Cthyltnediamine) cobalt(II1).

[Traduit par le journal] Can. J . Chem., 52,477 (1974)

Introduction In the course of studies of the hydrogen per-

oxide oxidation of coordinated thiocyanate ion in cis- and trans-[Coen2NH3NCSI2+ (1) we required authentic samples of the correspond- ing cyanoammine- and diamminebis(ethy1enedi-

I amine)cobalt(III) complexes for comparison pur- poses. Five early attempts to prepare cis-[Coen2- NH3CN]C12 according to a procedure reported by Ohkawa et al. (2) all led to a final cyanide ion- containing species which investigation showed to be the 1- cyano-2,3,4-triammine (ethylenedi- amine)cobalt(III) chloride. To our knowledge this particular complex has not been reported previously. We describe here some of the spectral and chemical properties of this complex and pre- sent the evidence upon which we base our conclu- sion regarding its configuration.

Experimental Reagents NH,[CO(SO,)~(NH~)~].~H~O was prepared according

to the procedure reported by Bailar and Peppard (3). [Co(NH3),CN]C12 was prepared and recrystallized fol- lowing Siebert's procedure (4). trans-[CoenzNH3CN]- C12.H20 was prepared and recrystallized as described previously (I). All other cobalt(II1)-containing complexes were prepared following the procedures described by Ohkawa et al. (2, 5).

All reagents used were A.R. grade or better and were used without further purification.

It~strurnerlts Ultraviolet-visible absorption spectra were recorded

on a Cary 14 recording spectrophotometer using matched silica cells of 1.0 cm path length. The temperature in the cells was maintained a t 25.0 "C by circulating water from a constant temperature bath through a specially designed cell holder in the spectrophotometer.

Infrared spectra were recorded on Beckman IR-10 and Perkin-Elmer 180 recording spectrophotometers operating in the double beam mode. Samples were. pre- pared in potassium bromide or cesium iodide discs (1% w/w concentration) and spectra recorded us. air or an attenuator in the reference beam path. Spectra were cali- brated using a polystyrene film and all frequencies are believed to be accurate to within + 5 cm-'.

Proton magnetic resonance spectra were recorded on a Varian T-60 spectrometer. Samples normally contained about 20 mg of complex dissolved in 0.50mI 1.8 M D2S04. The sodium salt of 3-(trimethylsilyl)propane sul- fonic acid (DSS) in 1.8 M D2S04 was used as an external standard. Chemical shift values (T) are given relative to the standard (T = 10.00 p.p.m.).

Procediires The techniques used in the ion-exchange, freeze-drying,

and recrystallization procedures have been described previously (1).

Elemental analyses were carried out by Galbraith Laboratories, Inc. (Knoxville, Tenn.).

Results and Discussion The reaction scheme outlined by Ohkawa et al.

(2, 5) involves the reaction of either the dark yellow form of N~,[CO(CN),(SO,),(NH,)~]~~ H 2 0 or the orange-yellow form of Na,[Co(CN),- (S03),(NH3),].5 H 2 0 with aqueous ethylene- diamine to yield cis-[Coen2CNS03], reaction of this complex with concentrated HBr to yield cis-

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478 C A N . J . CHEM.

[Coen,BrCN]Br.H,O, and ammonolysis of the latter compound to yield cis-[Coen,NH,CN]Cl,.

We found that when the dark yellow form of N~,[CO(CN),(SO,),(NH,)~].~ H 2 0 was heated with aqueous ethylenediamine, the solution changed color very slowly and, contrary to the observations of Ohkawa et al., brown crystals did not appear within a few minutes. After 2 h heating on a steam bath and evaporation to approximately one-half volume, yellow-brown crystals were present in solution. These were collected by filtra- tion of the hot solution and washed thoroughly with water, ethanol, and acetone.' Treatment of these yellow-brown crystals with concentrated HBr on a steam bath resulted in the formation of a deep purple solution from which a purple-red solid could be precipitated by the addition of ab- solute ethanol. Like cis-[Coen,BrCN]Br.H,O this solid possessed a visible absorption maxi- mum at 5 14 nm and a strong, sharp CEN stretch at 2130 cm-'. Unlike cis-[Coen,BrCN]Br.H,O (5) it was very soluble in water and could not be recrystallized successfully from this solvent. Treatment of this purple-red solid with liquid am- monia as per Ohkawa et al. (2) gave an orange- yellow solid which, when dissolved in water and chromatographed on Dowex 50W-X2 ion-ex- change resin, yielded at least four fractions: (i) unreacted starting material which was eluted with 0.50 M HCI, (ii) +2 charged species which were eluted with 1 M HC1, (iii) a +3 charged species which was eluted with 3 M HCl, and (iv) a species of unknown charge which was removed from the column with 6 M HCl (6). Only minor amounts of the total reaction product were in the 0.50, 3, and 6 M HCl fractions. The fractions from the column were freeze-dried and the solids obtained from the 1 M HC1 fractions recrystallized from ethanol-water as previously described (1). The solid obtained by freeze-drying of the 1 M HC1 fraction always contained a mixture of com- pounds as evidenced by the presence of at least three sharp bands of varying intensity in the

'Treatment of these yellow-brown crystals with an excess of 10% aqueous ethylenediamine solution for 3 h at 100 "C resulted in a quantitative conversion to cis- cyanosulfitobis(ethylenediamine)cobalt(III). When the orange-yellow form of Na3[Co(CN),(S03),(NH3),1- 5H,O was heated with aqueous ethylenediamine, cis- ~yanosulfitobis(ethylenediamine)cobalt(III) chloride crys- tallized from the reaction mixture as indicated by Ohkawa et 01. (2).

VOL. 52. 1974

2 100-21 50 cm- ' region. On recrystallization from ethanol-water a yellow solid was obtained which possessed only a single, strong, sharp C=N stretch at 2130 cm-I.

After drying to constant weight in vacuo over phosphorus(V) pentoxide, the recrystallized yellow solid yielded the following elemental analysis.

Anal. Calcd. for [Coen(NH3),CN]C1,(C3HI7- N7C1,Co): C, 13.50; H, 6.36; N, 31.50; C1,26.55. Found: C, 13.46; H, 6.31; N, 31.58; C1,27.01.

After recrystallization and drying in exactly the same manner cis-cyanoamminebis(ethy1enedi- amine)cobalt(III) chloride yielded the anhydrous salt whereas the trans isomer yielded the mono- hydrate, trans-[Coen2NH,CN]Cl2.H2O (1).

Assignments of configuration of cis and trans isomers using i.r. absorption spectra have fre- quently been recorded in the literature (7-12). The i.r. absorption characteristics of [Coen- (NH,),CN]Cl, were therefore examined in an effort to ascertain the geometrical arrangement of the ammonias and the cyanide ion in this com- plex. Like both cis-[Coen,NH,CN]Cl, and trans-[Coen2NH3CN]C12.H,0, [Coen(NH,),- CNIC1, showed a single, strong, sharp C=N stretch at 2130 cm- '. In the 1580-1620 cm- ' region (8, 9) the absorption pattern of [Coen- (NH,),CN]Cl, was similar to that observed for cis-[Coen,NH,CN]Cl, but the midpoint of the major peak was, as in the case of trans-[Coen, NH,CN]Cl,.H,O, at 1610 cm-'. In this region [Co(NH,),CN]Cl, showed a single, strong, broad peak centered at 1600 cm-'. Rigg and Sherwin (7) have assigned bands in the 1300 cm-' region to the asymmetric deformation of NH, and have concluded that, in isomeric diacidodiammine- (ethylenediamine)cobalt(III) complexes, the am- monia ligands are in a trans position if splitting is absent whereas, if splitting is present, no assign- ment of configuration can be made. In the 1300 cm-' region, the absorption pattern of [Coen- (NH,),CN]Cl, was much less complex than that observed for either cis-[Coen,NH,CN]Cl, or trans-[Coen,NH,CN]Cl,.H,O. However, by comparison to [Co(NH,),CN]Cl, which, in this region, showed single, sharp peaks at 1315 (s) and 1275 (w) cm-', splitting of the NH, bands was definitely present in [Coen(NH,),CN]CI,. Cham- berlain and Bailar (10) have attributed bands in the 1130-1150 cm-' region to N-H vibrations and have stated that in diacidobis(ethy1enedi-

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NORRIS: CORALT(1 Ill) COMPLEXES 479

amine)cobalt(TII) complexes trans isomers have one band in this region whereas cis isomers have two. Rigg and Sherwin (7) found the spectra of their isomeric diacidodiammine(ethy1enedi- amine)cobalt(III) complexes in this region to be too complex to enable them to apply this rule to their complexes. [Coen(NH,),CN]CI, showed a single, sharp, strong band at 1 150 cm- '. In the 850-900 cm-' region the spectruln of [Coen- (NH,),CN]CI, showed a very weak shoulder at 885cm-' associated with a weak peak at 870 cm-'. On the basis of Baldwin's (11) criterion and Rigg and Sherwin's (7) observations, [Coen- (NH,),CN]Cl, could be assigned a I-cyano- 2,3,4-triammine configuration. In the 610-500 cm-' region the spectrum of [Coen(NH,),CN]- C1, could be considered to possess four weak peaks if all shoulders were counted as peaks but the criterion advanced by Hughes and McWhinnie (12) to differentiate cis and trans isomers in the diacidobis(ethylenediamine)cobalt(III) series was very difficult to apply in this case. The overall ab- sorption pattern of [Coen(NH,),CN]Cl, in the 600-200 cm-' region was more like the absorp- tion pattern of cis-[Coen,NH,CN]Cl, than the absorption pattern of trans-[Coen,NH,CN]C&. H,O. In summary, i.r. data does no more than suggest a 1-cyano-2,3,4-triammine configuration for [Coen(NH,),CIU]Cl,. Certainly there is no one criterion of the several proposed (7-12) that can be said to establish unequivocally the con- figuration of the compound.

In the u.v.-visible region [ C O ~ ~ ( N H ~ ) ~ C N ] C ~ , possessed absorption maxima (A,,,) at 437 (E 69.0 M- ' cm-') and 327 nm (E 65.0 M-' cm-') and absorption minima (h,,,,) at 373 (E 1: 14.1 M- ' cm-') and 280 nm (E - 10.0 M- ' cm-'). The spectrum of the complex was un- affected by pH in the region pH 3.0-9.0. cis- [Coen2NH3CN]C1, showed absorption maxima at 436 (E 74.3 M- ' cm-') and 322 nm (E 82.3 M-'cm-') and minima at 371 (E 19.5 M-' cm- ') and 282 nm (E 22.0 M - ' cm- '). trans- [ C O ~ ~ , N H , C N ] C ~ ~ . H , O possessed absorption maxima at 434 (E 56.0 M- ' cm-') and 322 nm (E 59.9 M- ' cm-') and minima at 368 (E 14.0 M- ' cm-') and 287 nm (E 24.9 M- ' cm-') (1). [Co(NH,),CN]Cl, had absorption maxima at 441 (E 57.1 M- ' cm-') and 327 nm ( E 55.3 M- ' cm-') and absorption minima at 373 and 278 nm. The pattern observed for the A,,, and A m i n values of [Coen(NH,),CN]Cl, suggests it is a l-cyano-

2,3,4-triammine species. Strong support for this formulation is provided by the magnitude of E for [Coen(NH,),CN]Cl, at the long wavelength maxi~num : it is clearly much closer to the corre- sponding value of E forthecis-[Coen,NH,CN]CI, complex than it is to the value of E for the trans-[Coen2NH3CN]Cl2.H2O complex.

The p.m.r. spectrum of [Coen(NH,),CN]CI, in 1.8 M D2S04 showed resonance absorbances at 4.67, 5.00, and 7 . 1 0 ~ . The4.67 and 5.50 r resonances were fairly broad and of equal inten- sity and the 7.10 r resonance was very broad. Integrated areas were in the ratio of l(4.67 + 5.50 1):3.1 (7.10 7). On this basis the ab- sorbance~ at 4.67 and 5.50 are associated with the NH, protons of the ethylenediamine while the broad resonance at 7.10 obviously contains the resonances of both the NH, and CH, protons. Under similar conditions cis-[Coen2NH3CN]C12 showed resonance absorbances at 5.02,5.49,6.00 (very weak) and 7.23 r ; trans-[Coen,NH,CN]- CI,.H,O showed resonance absorbances at 5.23, 5.64, 6.37, and 7.14 T (1); and [Co(NH,),CN]CI, showed resonance absorbances at 6.00 and 6.95 t (integrated ratio 1 : 4). A major observation here is that in [Co(NH,),CN]Cl, the resonance ab- sorbance of the protons on the ammonia trans to the cyanide ion is 57 Hz downfield from the res- onance absorbance of the protons on the am- monias cis to the cyanide ion while the resonance absorbance of the protons on the ammonia in trans-[Coen,NH,CN]Cl,-H,O is approximately 50 Hz downfield from the resonance absorbance ofthe protons on the ammoniain cis-[Coen2NH3- CNIC1,. The proton resonance absorbance pat- tern for [Coen(NH,),CN]Cl, clearly indicates the absence in this complex of an ammonia group trans to a cyanide ion. On this basis, the com- pound is 1-cyano-2,3,4-triammine(ethy1enedi- arnine)cobalt(III) chloride. This conclusion con- tradicts none of the spectral information pre- viously presented and is in accord with the be- havior of this compound on recrystallization.

The nature of the other products produced from the reaction of liquid ammonia with the purple-red bromocyanodiammine(ethylene- diamine)cobalt(III) has not yet been clearly established. The solids obtained by freeze-drying of the 3 and the 6 M HCl fractions from the chromatography column both showed CGN stretches in the 2130 (w) and 2190 (m) cm-' region suggesting the presence of both terminal

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480 C A N . J . C H E M . VOL. 5 2 , 1974

and bridging cyanide groups in both complexes (13, 14). These compounds are undergoing further investigation.

Financial support by the National Research Council of Canada is acknowledged.

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