M.C. Chakravorti

Rhenium—V: Cyanogen compounds of quinquevalent rhenium

Abstract A new method for the preparation of K 3 [ReO 2 (CN) 4 ] from [ReO 2 py 4 ]Cl·2H 2 O is described. The acid association constants of [ReO 2 (CN) 4 ] 3− have been determined by Bjerrums method using Calvin-Wilson titration technique. The violet colour formed by the addition of acid to a solution of [ReO 2 (CN) 4 ] 3− has been shown by the method of continued variation to be due to a monoprotonated species [ReO(OH)(CN) 4 ] 2− . By the action of dilute hydrochloric acid on K 3 [ReO 3 (CN) 4 ] a deep pink crystalline substance of the composition ReO(CN) 3 · 2H 2 O has been isolated. This is acidic and very weakly paramagnetic. On the basis of interesting findings obtained in potentiometric and conductometric titrations of the substance with alkali, it has been formulated as H[ReO(OH)(H 2 O)(CN) 3 ] which remains in equilibrium in solution with its dibasic acid form H 2 [ReO(OH) 2 (CN) 3 ]. The dissociation constants of the acid have been determined. Various salts of both the mono-and dibasic acids, viz. M I ReO(OH)(H 2 O)(CN) 3 ] and M 2 I [ReO(OH) 2 (CN) 3 ] have been isolated. The i.r. spectra of the acid and also of the monopotassium salt gave both OH and H 2 O bands, while the spectra of the dipotassium salt gave OH, but no H 2 O band. The molecular conductance of the salt solutions also supports the formulae suggested. On strong desiccation and heating to 300°C the acid gave the polymeric substances H 2 [O(H 2 O)(CN) 3 Re·O·Re(CN) 3 (H 2 O)O] and O(CN) 2 Re·O·Re(CN) 2 O respectively.

Fluoro complexes of hexavalent uranium—IV Complexes of the series [UO2F3]− and [(UO2)2F5]−

Abstract The thermogravimetric studies of various salts of the ion [UO 2 F 3 ] − with organic basic cations have been made. By the pyrolysis of the salts with α-picoline, quinoline, 2,2′-dipyridyl and anthranilic acid, compounds of the type BH[(UO 2 ) 2 F 5 ] have been isolated. Similar salts with dimethyl aniline, cis - and trans -[Co(NH 3 ) 4 F 2 ] + and also the quinoline compound were obtained by direct precipitation of uranyl fluoride with the organic bases or with salts containing the complex cations in dilute HF medium. The conductivities and the solubilities of the salts and also of the salts belonging to the series [UO 2 F 3 ] − have been determined. A free acid formulated as H[UO 2 F 3 ].H 2 O has been isolated by reacting uranium trioxide with aqueous HF. It has been characterised by conductivity, and pH measurement of dilute solutions, potentiometric titration with alkali, determination of dissociation constant, thermogravimetric analysis and by a comparison of these results with those of UO 2 F 2 .2H 2 O.

Fluoro complexes of hexavalent uranium—III: Complexes of the series [UO2F4]2−

Abstract Complex uranyl fluorides of the general formulae BH 2 [UO 2 F 4 ]· n H 2 O, M II [UO 2 F 4 ]· n H 2 O and M 2 I [UO 2 F 4 ]· n H 2 O where B = organic diamine base, viz. biguanide and phenyl biguanide, M II = Ba 2+ and bivalent complex cations [Ni(py) 4 ] 2+ [Ni(en) 2 ] 2+ and M 1 = alkali metals Na + , K + and NH 4 + have been isolated in pure state. The compounds with organic bases were obtained by mixing the organic base fluorides with uranyl fluoride in 20% HF medium. The compounds with complex cations were obtained by the action of pyridine or ethylene diamine on a mixture of nickel fluoride and uranyl fluoride. The Na + , K + and NH 4 + salts were obtained by the metathesis of the compounds containing complex cations with NaClO 4 , KI and NH 4 I respectively. The barium salt was obtained by the metathesis between the potassium salt and BaCl 2 in the presence of boric acid. The solubilities of some of the salts in water have been determined. The salts have been characterised by elemental analysis, metathesis studies, conductivity measurement, thermogravimetric analysis and i.r. spectral studies.

A new series of molybdenum(V) fluoro complexes

Abstract The isolation and characterization of salts of a new series of fluoromolybdates(V) are described. The hydrazinium salt, N2H6[Mo(OH)F6]. H2O has been obtained by reducing a solution of MoO3 in 40 per cent HF with hydrazine fluoride. The rubidium, caesium and α-naphthyl aminium salts, M2[Mo-(OH)F6], where M = Rb, Cs and C10H10N have been obtained by crystallizing the fluorides of the respective cations with the hydrazinium(II) salt in 20 per cent HF medium. A potassium salt which has been formulated as K2[MoOF4(HF2)] or K[MoOF4]. KHF2 on the basis of i.r. spectra, has also been prepared by the same method. All the salts are green crystalline substances and stable when dry. The hydrazinium(II) and the potassium salts can be recrystallized from 20 per cent HF. The oxidation number of molybdenum determined by oxidation with dichromate and the magnetic moment values indicate the quinquevalency of molybdenum in the salts. The i.r. spectra of the rubidium and caesium salts give the characteristic ν(OH) bands, but no δ(HOH) band. Strong and sharp bands observed at around 980 cm−1 in the spectra of these hydroxo salts have been tentatively assigned as the deformation mode of MoOH group. The hydrazinium salt undergoes dehydrohalogenation and under different conditions the complexes N2H6-[MoOF5], [Mo(OH)F4(N2H4)] and [MoOF3(N2H4)] have been isolated.

Fluoro complexes of hexavalent uranium—V: Fluorooxalato complexes of dioxouranium(VI)

Abstract The salts of the new types M2[UO2F2(C2O4)], M4[UO2F2(C2O4)2] and M2[(UO2)2F4(C2O4)] (where M = potassium and rubidium) have been prepared by mixing saturated solutions of H[UO2F3]·H2O with alkali metal oxalate solutions in cold in different mole ratios. Molecular conductances of the salt solutions indicate that the ions are decomposed in dilute solution to a great extent. The complexes are also completely decomposed on passing their solutions through a column of cation exchange resin in hydrogen form. The IR spectra of the salts of [UO2F2(C2O4)]2− and [UO2F2(C2O4)2]4− indicate that oxalate is acting as a normal chelating agent, while the spectra of the salts of [(UO2)2F4(C2O4)]2− support that the ion contains bridged oxalate group. The lattice parameters of the three potassium salts have been reported.

Fluoro complexes of hexavalent uranium—VI adducts of dioxodifluorouranium (VI) with nitrogen and oxygen donor ligands

Abstract Adducts of uranyl fluoride of the types UO2F2·L·H2O and UO2F2·L′ (where L = 2,2′-dipyridyl, 1, 10-phenathroline and 8-hydroxyquinoline; L′ = dimethyl sulphoxide, dimethyl formamide, pyridine, α-picoline and γ-picoline) have been prepared by mixing uranyl fluoride and the corresponding ligand in 1:1 mole ratio in 50% aqueous ethanolic medium. Two adducts with urea, viz. [UO2F2(urea)] and [UO2F2(urea)2] have been obtained by reacting uranyl fluoride with urea in different mole ratios in dry methanolic medium. The molecular conductances of the complexes in methanol indicate their nonelectrolytic nature. IR spectral studies show that urea, dimethyl formamide and dimethyl sulphoxide complexes are oxygen bonded ones. Thermogravimetric analysis suggests that the dipyridyl, phenanthroline and oxine complexes contain coordinated water.

Rhenium—IX: Mixed ligand oxofluoropyridine complexes of quinquevalent rhenium and salts of a new cation [ReO2py2(H2O)2]+

Abstract Two oxofluoropyridine complexes, viz. [ReO2py3F] and [ReO2py2F], have been obtained by heating [ReO2py4]F at 70° and 100°C respectively. Digestion of an acetone solution of [ReO2py4]F in the presence of dimethyl sulphate gave a precipitate of [ReO2py2(H2O)F]. Treatment of [ReO2py4]F with 40% HF gave the fluoride salt of a new complex cation of rhenium(V), viz. [ReO2py2(H2O)2]F. The chloride and the perchlorate salts of the cation have also been prepared. I.R. spectra of [ReO2py4]F, [ReO2py2F], [ReO2py2(H2O)2]Cl and [ReO2py2(H2O)2]ClO4 show the characteristics of coordinated pyridine and in addition a strong band at about 825 cm−1 which indicates the presence of trans OReO grouping in the complexes. Log k for the equilibrium [ReO2py2(H2O)2]+ ⇋ [ReO(OH)py2(H2O)2]+2, determined potentiometrically by Bjerrums method is 1·9 at 30°C. The complexes [ReO2py4]F, [ReO2py2F], [ReO2py2(H2O)F], [ReO2py2(H2O)2]F and [ReO2py2(H2O)2]ClO4 were found to be very weakly paramagnetic, having the moments ranging from 0·28 to 0·61 B.M. at 303°K.

Rhenium — VII mixed ligand oxofluorooxalato complexes of quinquevalent rhenium

Abstract A mixed ligand oxofluorocyano complex of quinquevalent rhenium, viz. H[ReOF(H2O)-(CN)3] has been prepared by boiling K3[ReO2(CN)4] with 40% hydrofluoric acid. Sodium, potassium and ammonium salts, M1[ReOF(H2O)(CN)3] have been obtained by neutralising the acid with the corresponding alkali acetates and then precipitating with ethanol. Tl+, Ni2+, [Co(NH3)6]3+ and [Coen3]3+ salts have been prepared by precipitating the acid with the salts of these ions. The acid loses half a molecule of hydrogen fluoride at 110°C and forms the dinuclear acid H[Re2O2F(H2O)2(CN)6]. The potassium salt of this acid has been prepared by neutralising with caustic potash and precipitating with ethanol. The mononuclear acid is very weakly paramagnetic. The dissociation constant determined by Bjerrums method is pKa = 3·3 at 30°CC. The i.r. spectra of the acid and of its potassium salt have been reported.

Fluoro complexes of hexavalent uranium—VIII Mixed fluorochloro and fluorobromo complexes of dioxouranium(VI)☆

Abstract The fluorochloro and fluorobromo complexes K 2 [UO 2 F 3 Cl], Cs 2 [UO 2 F 2 Cl 2 ], phenH 2 [UO 2 F 3 Cl] and phenH 2 [UO 2 F 3 Br] have been prepared by crystallising solutions containing H[UO 2 F 3 ]·H 2 O and alkali metal chloride or 1,10-phenanthroline in dilute hydrochloric/hydrobromic acid medium. Molecular conductance data of the alkali metal salts are slightly higher than that of a 1:2 type electrolyte. Thermogravimetric studies on the two phenanthrolinium salts revealed that they decompose from about 80° with the formation of phenH[UO 2 F 3 ]. IR spectral and X-ray powder diffraction studies of the mixed halo complexes have been made.

Fluoro complexes of hexavalent uranium—III

Abstract Complex uranyl fluorides of the general formulae BH 2 [UO 2 F 4 ]· n H 2 O, M II [UO 2 F 4 ]· n H 2 O and M 2 I [UO 2 F 4 ]· n H 2 O where B = organic diamine base, viz. biguanide and phenyl biguanide, M II = Ba 2+ and bivalent complex cations [Ni(py) 4 ] 2+ [Ni(en) 2 ] 2+ and M 1 = alkali metals Na + , K + and NH 4 + have been isolated in pure state. The compounds with organic bases were obtained by mixing the organic base fluorides with uranyl fluoride in 20% HF medium. The compounds with complex cations were obtained by the action of pyridine or ethylene diamine on a mixture of nickel fluoride and uranyl fluoride. The Na + , K + and NH 4 + salts were obtained by the metathesis of the compounds containing complex cations with NaClO 4 , KI and NH 4 I respectively. The barium salt was obtained by the metathesis between the potassium salt and BaCl 2 in the presence of boric acid. The solubilities of some of the salts in water have been determined. The salts have been characterised by elemental analysis, metathesis studies, conductivity measurement, thermogravimetric analysis and i.r. spectral studies.