Mehrkernige Kobaltkomplexe. II. Herstellung und Struktur von [(tren) (NH3)Co(O2)Co(NH3) (tren)](SCN)4 · 2H2O

Polynuclear Cobalt Complexes. II. Preparation and Structure of [(tren) (NH₃)Co(O₂)Co(NH₃) (tren)](SCN)₄ · 2H₂O The title compound is obtained on oxygenation of [Co(tren)(H₂O)₂]²⁺ in 6M aqueous ammonia or by ligand exchange starting from [(NH₃)₅Co(O₂)Co(NH₃)₅]-(NO₃)₄. An X-ray structure determination was made. The substance forms monoclinic crystals, space group P2₁/c, lattice constants a=10,135, b=8,473, c=19,484 Å, β=108,58°, with two formula units in the cell. The final R is 0,066. The binuclear cation has a center of symmetry, so the Co? O? O? Co unit is planar; the Co? O? O angle is 111,5°. The tertiary nitrogen atoms of both chelate groups are cis to the O₂ bridge, as found in doubly bridged [(tren)Co(O₂,OH)Co(tren)](ClO₄)₃ · 3H₂O. On acidification in solution, the singly bridged cation [(tren) (NH₃)CoO₂Co(NH₃)(tren)]⁴⁺ (a) loses the bound O₂ completely. But unlike the doubly bridged cation b , the rate of dissociation of a is independent of pH (Fig. 5). At higher pH (8–10) bridging a→b (Fig. 2) occurs. Both reactions must have the same rate determining step, the first order rate constants being of the order of 2 · 10^?3 s^?1 (25°, 0,35M KCl).     

Tetraammine(selenito‐O,O′)cobaltate(III) nitrate monohydrate

The title compound crystallizes as the mono­hydrate, [Co(SeO₃)(NH₃)₄]NO₃·H₂O. The crystallographic mirror symmetry coincides with the molecular symmetry; the mirror plane passes through the cation, anion and water mol­ecule. The CoN₄O₂ octahedron is distorted, with the selenito group acting as a bidentate ligand through two bridging O atoms to the cobalt. The coordinated Se—O distance is 1.742 (2) Å, whereas the uncoordinated Se—O distance is 1.646 (3) Å. A three‐dimensional hydrogen‐bonded network exists between [Co(SeO₃)(NH₃)₄]NO₃ and the water mol­ecule. The nitrate anion and water mol­ecule form open pores in the structure when hydrogen bonded to two neighboring [Co(SeO₃)(NH₃)₄]⁺ cations. Selenium participates in two types of relatively close intermolecular interactions with neighboring charged species (Se?N1 and Se?O3), but does not participate in an interaction with a neighboring O2 atom, the nearest contact distance being 4.638 (3) Å.     

Über die Kristallstrukturen der Cyanokomplexe [Co(NH3)6][Fe(CN)6], [Co(NH3)6]2[Ni(CN)4]3 · 2 H2O und [Cu(en)2][Ni(CN)4]

On the Crystal Structures of the Cyano Complexes [Co(NH₃)₆][Fe(CN)₆], [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O, and [Cu(en)₂][Ni(CN)₄] Of the three title compounds X‐ray structure determinations were performed with single crystals. [Co(NH₃)₆][Fe(CN)₆] (a = 1098.6(6), c = 1084.6(6) pm, R3, Z = 3) crystallizes with the CsCl‐like [Co(NH₃)₆][Co(CN)₆] type structure. [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O (a = 805.7(5), b = 855.7(5), c = 1205.3(7) pm, α = 86.32(3), β = 100.13(3), γ = 90.54(3)°, P1, Z = 1) exhibits a related cation lattice, the one cavity of which is occupied by one anion and 2 H₂O, whereas the other contains two anions parallel to each other with distance Ni…Ni: 423,3 pm. For [Cu(en)₂][Ni(CN)₄] (a = 650.5(3), b = 729.0(3), c = 796.5(4) pm, α = 106.67(2), β = 91.46(3), γ = 106.96(2)°, P1, Z = 1) the results of a structure determination published earlier have been confirmed. The compound is weakly paramagnetic and obeys the Curie‐Weiss law in the range T < 100 K. The distances within the complex ions of the compounds investigated (Co–N: 195.7 and 196.4 pm, Ni–C: 186.4 and 186.9 pm, resp.) and their hydrogen bridge relations are discussed.     

Cobalt-Komplexe mit O2-Brücken: Die Struktur von μ-Peroxo-bis[pentaammincobalt(III)]-tetranitrat-dihydrat

Cobalt Complexes with 0₂ Bridges: Structure of μ-Peroxo-bis[pentaamminecobalt(III)] Tetranitrate Dihydrate An X-ray structure determination of the binuclear complex [(NH₃)₅CoO₂Co(NH₃)₅] (NO₃)₄ · 2 H₂O A has been performed; R = 0.051. A crystallizes in the space group P2₁/n with Z = 2 and with lattice constants a = 11.657(5), b = 11.977(6), c = 8.082(4) Å, and β = 91.58(4)°. The complex cation has crystallographic 1 -symmetry. The Co? O? O? Co unit is planar with an O? O distance of 1.472(6) Å. Two of the three crystallographically independent NO₃ groups show disorder.     

Mehrkernige Kobaltkomplexe. IV. Darstellung und Struktur von [(papd)Co(O2)Co(papd)](S2O6)(NO3)2 · 4 H2O1)

Polynuclear Cobalt Complexes. IV. Preparation and Structure of [(papd)Co(O₂)Co(papd)](S₂O₆)(NO₃)₂ · 4 H₂O The binuclear peroxo complex [(papd)Co(O₂)Co(papd)](S₂O₆)(NO₃)₂ · 4 H₂O I crystallizes in the triclinic space group P1 . Lattice constants are a = 9.405(4), b = 9.270(4), c = 12.218(6)Å, α = 89.58(5), β = 99.08(6), γ = 114.79(5)° for Z = 1. The binuclear cation has a center of symmetry, so the Co? O? O? Co unit is planar. Three chelate rings have a common plane, the ligand configuration is δ.     

Alkalimolybdotellurate: Darstellung und Kristallstruktur von Rb6[TeMo6O24] · 10H2O und Rb6[TeMo6O24] · Te(OH)6 · 6H2O

Alkaline Molybdotellurates: Preparation and Crystal Structures of Rb₆[TeMo₆O₂₄] · 10H₂O and Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6H₂O Single crystals of Rb₆[TeMo₆O₂₄] · 10 H₂O and Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6 H₂O, respectively, were grown from aqueous solution. Rb₆[TeMo₆O₂₄] · 10 H₂O possesses the space group P1 . The lattice dimensions are a = 963.40(13), b = 972.56(12), c = 1 056.18(13) pm, α = 97.556(10), β = 113.445(9), γ = 102.075(10)°; Z = 1, 2 860 reflections, 215 parameters refined, R_g = 0.0257. The centrosymmetrical [TeMo₆O₂₄]^6? anions are stacked parallel to [010]. Rb(2) is coordinated with one exception by water molecules only. Folded chains consisting of [TeMo₆O₂₄]^6? anions and Rb(2) coordination polyhedra which are linked to pairs represent the prominent structural feature. Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6 H₂O crystallizes monoclinically in the space group C2/c with a = 1 886.4(3), b = 1 000.9(1), c = 2 126.5(3) pm, and β = 115.90(1)°; Z = 4, 3 206 reflections, 240 parameters refined, R_g = 0.0333. It is isostructural in high extent with (NH₄)₆[TeMo₆O₂₄] · Te(OH)₆ · 7 H₂O. Hydrogen bonds between Te(OH)₆ molecules and [TeMo₆O₂₄]^6? anions establish infinite strands. The [TeMo₆O₂₄]^6? anions gather around Te(OH)₆ providing channel-like voids extending parallel to [001].     

On the proton-acceptor properties of [TeMo6O24]6− in Na4(NH4)2[TeMo6O24] · 16H2O

Colourless triclinic single crystals of Na₄(NH₄)₂[TeMo₆O₂₄] · 16H₂O were grown in aqueous solution (space group P1 , a = 1 075.3(1), b = 1 074.2(1), c = 1 089.8(1) pm, = 96.259(9), β = 118.556(7), γ = 113.355(8)°, Z = 1, 295 K, 311 parameters, 3 689 reflections, R_g = 0.0197). There are two crystallographically independent Na⁺ cations. Na(1) is coordinated octahedrally by four water molecules and two oxygen atoms of the centrosymmetric [TeMo₆O₂₄]^6? anion. Na(2) is bound to five water molecules in a considerably distorted trigonally bipyramidal fashion. These bipyramids are linked with NH₄⁺ by hydrogen bonds to yield centrosymmetric cluster cations consisting of two NH₄⁺ and two Na(H₂O)₅⁺ each. Hydrogen bonds envolving all except one (O(10)) of the oxygen atoms of the [TeMo₆O₂₄]^6? anion as almost equivalent proton acceptors regardless of their bonding mode to Te and Mo, respectively, establish further connections to NH₄⁺ and the water of crystallization.     

Tri­potassium hexa­hydrogen­hexa­molybdo­cobaltate(III) potassium nitrate tetra­hydrate,K3[H6CoMo6O24]·KNO3·4H2O

The title double salt was obtained from the reaction of Y(NO₃)₃ and K₆[H₄Co₂Mo₁₀O₃₈]·5H₂O at a pH of about 2.0. The [H₆CoMo₆O₂₄]^3? anion is a typical B‐type Anderson‐structure heteropolyanion, and has an inversion center, with Co—O bond lengths in the range 1.907 (4)–1.919 (4) Å and Mo—O bond lengths in the ranges 1.709 (5)–1.721 (5), 1.902 (5)–1.951 (5) and 2.274 (4)–2.312 (4) Å.     

Co(en)3[B4O5(OH)4]Cl·3H2O和[Ni(en)3][B5O6(OH)4]2·2H2O的合成、结构以及热力学性质

利用水热法合成了两种过渡金属配合物为模板剂的含水硼酸盐晶体Co(en)3[B4O5(OH)4]Cl·3H2O(1) 和 [Ni(en)3][B5O6(OH)4]2·2H2O (2),并通过元素分析、X射线单晶衍射、红外光谱及热重分析对其进行了表征。化合物1晶体结构的主要特点是在所有组成Co(en)33+, [B4O5(OH)4]2–, Cl– 和 H2O之间通过O–H…O、O–H…Cl、N–H…Cl和N–H…O四种氢键连接形成网状超分子结构。化合物2晶体结构的特点是[B5O6(OH)4]–阴离子通过O–H…O氢键连接形成沿a方向有较大通道的三维超分子骨架,模板剂[Ni(en)3]2+阳离子和结晶水分子填充在通道中。     

Double complexes [Co(NH3)5(H2O)]2[Zr3F18]·6H2O and [Co(NH3)6]2[Zr3F18]·6H2O

The structures of orthorhombic bis[pentaammineaquacobalt(III)] tetra‐μ₂‐fluorido‐tetradecafluoridotrizirconium(IV) hexahydrate (space group Ibam), [Co(NH₃)₅(H₂O)]₂[Zr₃F₁₈]·6H₂O, (I), and bis[hexaamminecobalt(III)] tetra‐μ₂‐fluorido‐tetradecafluoridotrizirconium(IV) hexahydrate (space group Pnna), [Co(NH₃)₆]₂[Zr₃F₁₈]·6H₂O, (II), consist of complex [Co(NH₃)_x(H₂O)_y]³⁺ cations with either m [in (I)] or and 2 [in (II)] symmetry, [Zr₃F₁₈]⁶⁻ anionic chains located on sites with 222 [in (I)] or 2 [in (II)] symmetry, and water molecules.     

Darstellung,Kristallstruktur, thermischer Abbau und Schwingungsspektren von [Co(NH3)6]2[Be4O(CO3)6] · 10 H2O

Preparation, Crystal Structure, Thermal Decomposition, and Vibrational Spectra of [Co(NH₃)₆]₂[Be₄O(CO₃)₆] · 10 H₂O [Co(NH₃)₆]₂[Be₄O(CO₃)₆] · 10 H₂O is a suitable compound for the quantitative determination of beryllium. It can be obtained by reaction of aqueous solutions of carbonatoberyllate with [Co(NH₃)₆]Cl₃. The crystal structure (trigonal‐rhombohedral, R3c (Nr. 161), a = 1071,6(1) pm, c = 5549,4(9) pm, V_EZ = 5519(1) · 10⁶ pm³, Z = 6, R1(I ≥ 2σ(I)) = 0,037, wR2(I ≥ 2σ(I)) = 0,094) contains [Co(NH₃)₆]³⁺‐ and [Be₄O(CO₃)₆]^6–‐ions, which are directly hydrogen bonded as well as with water molecules. The complex cations and anions occupy the positions of a distorted anti‐CaF₂‐type. The thermal decomposition, IR and Raman spectra are presented and discussed.     

New Perspectives in Polyoxometalate Chemistry by isolation of compounds containing very large moieties as transferable building blocks: (NMe4)5[As2Mo8V4AsO40] · 3H2O, (NH4)21[H3Mo57V6(NO)6O183(H2O)18] · 65 H2O, (NH2Me2)18(NH4)6[Mo57V6(NO)6O183(H2O)18] · 14 H2O,and (NH4)12[Mo36(NO)4O108(H2O)16] · 33 H2O

The compounds (NMe₄)₅[As₂Mo₈V₄AsO₄₀] · 3 H₂O 2a , (NH₄)₂₁[H₃Mo₅₇V₆(NO)₆O₁₈₃(H₂O)₁₈] · 65 H₂O 3a , (NH₂Me₂)₁₈(NH₄)₆[Mo₅₇V₆(NO)₆O₁₈₃(H₂O)₁₈] · 14 H₂O 3b and (NH₄)₁₂[Mo₃₆(NO)₄O₁₀₈(H₂O)₁₆] · 33 H₂O 4a ( 3a and 4a were not correctly reported in the literature regarding to their composition, structures and the oxidation states of the metal centres) which contain large isolated anionic species, have been prepared (among them 3a, 3b , and 4a in rather high yield) and characterized by complete crystal structure analysis as well as IR/Raman, UV/VIS/NIR, ESR spectroscopy and magnetic susceptibility measurements, redox titrations, bond valence sum calculations, elemental analyses and thermogravimetric studies. Perspectives for polyoxometalate chemistry referring to the synthesis of “extremely” large nanoscaled species are discussed, together with the occurrence of a large transferable {Mo₁₇} building block in the compounds 3a, 3b and 4a which also exists in the corresponding iron compound Na₃(NH₄)₁₂[H₁₅Mo₅₇Fe₆(NO)₆O₁₈₃(H₂O)₁₈] · 76 H₂O 7a .     

Double complex salts [Pt(NH3)5Cl][M(C2O4)3] · n H2O (M = Fe, Co, Cr): Synthesis and study

Double complexes [Pt(NH₃)₅Cl][Fe(C₂O₄)₃] · 4H₂O, [Pt(NH₃)₅Cl][Co(C₂O₄)₃] · 2H₂O, and [Pt(NH₃)₅Cl][Cr(C₂O₄)₃] · 4H₂O were synthesized and studied by single-crystal X-ray diffraction, X-ray phase analysis, differential thermal analysis, elemental analysis, and IR spectroscopy. The crystal structures of the compounds were examined from the viewpoint of the close packing of coordination polyhedra. The thermal properties of the synthesized complexes and K₃[M(C₂O₄)₃] salts (M = Fe, Co, Cr) were compared. A procedure for the synthesis of the FePt, CoPt, and CrPt intermetallic compounds through the thermolysis of the obtained complexes was developed. Original Russian Text ? K.V. Yusenko, D.B. Vasil’chenko, A.V. Zadesenets, I.A. Baidina, Yu.V. Shubin, S.V. Korenev, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 10, pp. 1589–1593.     

Synthesis,Crystal Structure and Vibrational Spectroscopy of NH4[Co(NH3)5(H2O)][B4O5(OH)4]2·6H2O

A novel hydrated cobalt tetraborate complex NH₄[Co(NH₃)₅(H₂O)][B₄O₅(OH)₄]₂·6H₂O, was synthesized by the reaction of NH₄‐borate aqueous with CoCl₂ and its structure was determined by single crystal X‐ray diffraction. The crystal system of this complex is orthorhombic, the space group is Pnma, and the unit cell parameters are a=1.2901(2) nm, b=1.6817(3) nm, c=1.1368(2) nm, α=β=γ=90°, V=2.4742(8) nm³, and Z=4. This compound contains infinite borate layers constructed from [B₄O₅(OH)₄]^2? units via hydrogen bonds. The adjacent polyborate anion layers are further linked together with the octahedral [Co(NH₃)₅(H₂O)]³⁺ groups through hydrogen bonds to form 3D framework. The groups and guest water molecules are deposited in the empty space of this framework and interact with the layers by extensive hydrogen bonds. Infrared and Raman spectra (4000–400 cm^?1) of NH₄[Co(NH₃)₅(H₂O)][B₄O₅(OH)₄]₂·6H₂O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The middle band observed at 575 cm^?1 in Raman spectrum is the pulse vibration of [B₄O₅(OH)₄]^2?.     

Transition Metal Complexes Containing Dihydrogen Hypodiphosphate in Eclipsed Conformation as Ligand: Preparation,Crystal Structure,Vibrational Spectra,and Thermal Behavior of K2[M(H2P2O6)2(H2O)2]·H2O (M = Co,Ni, Cu,and Zn)

The transition metal dihydrogen hypodiphosphate hydrates K₂[Co(H₂P₂O₆)₂(H₂O)₂] · H₂O ( 1 ), K₂[Ni(H₂P₂O₆)₂(H₂O)₂] · H₂O ( 2 ), K₂[Cu(H₂P₂O₆)₂(H₂O)₂] · H₂O ( 3 ) and K₂[Zn(H₂P₂O₆)₂(H₂O)₂] · H₂O ( 4 ) were synthesized and characterized by single crystal structure determination. The compounds 1 – 4 crystallize isotypic in the monoclinic space group C2/m (no. 12) with two formula units in the unit cell. The crystal structure is built up by [H₂P₂O₆]^2– units in an eclipsed conformation, by the corresponding transition metal, potassium cations, and water molecules. The eclipsed conformation of the [H₂P₂O₆]^2– has not been previously observed in none of known hypodiphosphates(IV) analyzed via X‐ray diffraction. However, its proposed based on spectroscopic methods. FT‐IR/FIR and FT‐Raman spectra of the crystalline salts were recorded and the thermal behavior of the compounds was investigated.     

Neue Oxonium-Bromochalkogenate(IV) — Darstellung,Struktur und Eigenschaften von [H3O][TeBr5] · 3C4H8O2 und [H3O]2[SeBr6]

New Oxonium Bromochalcogenates(IV) — Synthesis, Structure, and Properties of [H₃O][TeBr₅] · 3 C₄H₈O₂ and [H₃O]₂[SeBr₆] Dark red crystals of the composition [H₃O][TeBr₅] · 3 C₄H₈O₂ ( 1 ) were isolated from a saturated solution of TeBr₄ in 1,4-dioxane containing a small amount of water. In this compound (space group P2₁/m, a = 8.922(4) Å, b = 13.204(7) Å, c = 9.853(5) Å, β = 91.82(4)° at 150 K) a square pyramidal [TeBr₅]^? anion has been isolated for the first time. The coordination sphere of the anion is completed to a distorted octahedron by weak interaction with a dioxane molecule of the cationic system. The [H₃O]⁺ cations are connected to chains by dioxane molecules. At room temperature the compound is stable only in its mother liquor. Crystalline [H₃O]₂[SeBr₆] ( 2 ) (space group Fm3m, a = 10.421(1) Å at 170 K) is a bromoselenous acid of high symmetry. The [H₃O]⁺ ion is only weakly coordinated by Br atoms of the anion. The anions are isolated octahedral [SeBr₆]^2? units. The structure is isotypic to the K₂[PtCl₆] structure. Despite being a halogenochalcogen(IV) acid, 2 exhibits a remarkable thermal stability. Both oxonium compounds were characterized by single-crystal X-ray structure analyses. Vibrational spectra of 2 are reported.     

Water‐soluble and Halogen‐free Hexaammine Complexes of Metal Ions of Group 9 – Synthesis,Crystal Structures,and Vibrational Spectra

Reaction of [M(NH₃)₆]Cl₃ (M = Co, Rh, Ir) and [Ir(NH₃)₅(OH₂)]Cl₃ with (NH₄)₂C₂O₄ · H₂O in aqueous solution resulted in the isolation of [M(NH₃)₆]₂(C₂O₄)₃ · 4 H₂O and [Ir(NH₃)₅(OH₂)]₂(C₂O₄)₃ · 4 H₂O, respectively. The complexes have been characterized by X‐ray crystallography, IR and UV/VIS spectroscopy. The isomorphous compounds crystallize in the orthorhombic space group Pnnm (No. 58). Four molecules of crystal water are involved in an extended three‐dimensional hydrogen bonding network. The librational modes of the lattice water around 600 cm^–1 allow the characterization of [Ir(NH₃)₆]₂(C₂O₄)₃ · 4 H₂O and [Ir(NH₃)₅(OH₂)]₂(C₂O₄)₃ · 4 H₂O, respectively, by IR spectroscopy. The band around 600 cm^–1 shows a significant frequency shift in the IR spectra of the hexaammine and aquapentaammine complex of iridium(III) and, by that, a distinction is possible.     

Computer-aided measurement of kinetic parameters of electrode reactions of cobalt(III)—ammine complexes at mercury electrodes

A computer-aided technique based on Tast polarography is examined for the determination of kinetic parameters of electrode reactions. It is particularly useful for the investigation of unstable species because of the simple and rapid processing of data. Kinetic parameters of cobalt(III)—ammine complexes at mercury electrodes are given for [Co(NH₃)₆]Cl₃, [Co(H₂O)(NH₃)₅](ClO₄)₃, [Co(NO₃)(NH₃)₅](NO₃)₂ [CoF(NH₃)₅](Cl0₄)₂, [Co(C0₃)(NH₃)₅] NO₃ ,cis-[Co(H₂O)₂(NH₃)₄] (Cl0₄)₃ [Co(CO₃)(NH₃)₄] NO₃ · 0.5H₂0, [Co(ox)(NH₃)₄]Cl · H₂0, and NH₄[Co(ox)₂(NH₃)₂] · H₂O, which are obtained in solutions containing 0.1 M acetate buffer and 0.005% gelatin at 25°C.     

Na7Y2(P2O7)2 (P3O10) – A New Layer and Tunnel Structure

A new layered phosphate, Na₇Y₂(P₂O₇) ₂(P₃O₁₀), containing both [P₂O₇]^4? and [P₃O₁₀]^5? groups, has been prepared. It crystallizes in the monoclinic space group P2/c with a = 16.205(4), b = 5.3746(9), c = 12.309(4) Å, β = 97.96(2)°, V = 1061.7(5) ų and Z = 2. The structure was solved and refined to R₁ = 0.0298 and wR₂ = 0.0698 for 1844 independent reflections with I > 2σ(I). It consists of layers of corner and edge-sharing YO₇ polyhedra, P₂O₇ and P₃O₁₀ groups. Each layer is built up from two parallel [YP₂O₇] slabs, held together by the P₃O₁₀ groups. This arrangement gives rise to intersecting tunnels within the layer. The Na⁺ cations are located in the tunnels and between the layers. Both P₂O₇ and P₃O₁₀ groups contain unshared oxygen atoms directed toward the interlayer space and toward the tunnels. The P₂O₇ groups show a staggered configuration. In addition to this original layered framework, the title compound provides the third example of a compound containing a mixed anion of [P₂O₇]^4? and [P₃O₁₀]^5?. The structure was compared with the two previously reported ones, containing such a mixed anion: NH₄Cd₆(P₂O₇) ₂(P₃O₁₀) [6] and Cs₂Mo₅O₂(P₂O₇)₃ · (P₃O₁₀) [7].     

Zur Kenntnis der Sulfito-kobalt(III)-Ammine. III. Hydrogensulfitokobalt(III)-Ammine

Sulphito Cobalt(III) Ammines. III. Hydrogensulphito Cobalt(III) Ammines Concentrated acids react with [CoSO₃(NH₃)₅]⁺ salts hydrogen- sulphitopentaamminecobalt(III) complexes. [Co(HSO₃)(NH₃)₅]Cl₂, [Co(HSO₃)(NH₃)₅]Br₂ and [Co(HSO₃)(NH₃)₅](HSO₄)₂·H₂O have been isolated. These substances are yellow coloured in contrast to an earlier work which reported red colour. Furthermore, the hydrogensulphitoacidotetreaammine complexes [Co(HSO₃)Cl(NH₃)₄]Cl, [Co(HSO₃)Cl(NH₃)₄]ClO₄·H₂O, [Co(HSO₃)Br(NH₃)₄]Br and [Co(HSO₃) CN(NH₃)₄]Cl habe been prepared. [Co(HSO₃)Br(NH₃)₄]Br is losing spontaneously HBr forming [CoSO₃Br(NH₃)₄]. The neutral complex [Co(HSO₃)SO₃(NH₃)₄]·1/2H₂O has been obtained from cis- NH₄[Co(SO₃)₂(NH₃)₄] and HCl. The absorption spectra in the IR, visible and UV region are reported and discussed. The HSO₃ group is coordinated to Co through the S atom. The Co? S bond is weaker than in the sulphito complexes as concluded from the RAMAN spectrum. In the new complexes, the hydrogensulphito ligand causes a minor trans effect than the sulphito ligand.