Complexes sulfito

Ruthenium(IV) produces few other complexes of interest but osmium(IV) yields several sulfito complexes (e.g. [0s(S03)6] and substituted derivatives) as well as a number of complexes, such as [Os(bipy)Cl4] and [Os(diars)2X2] (X = Cl, Br, I), with mixed halide and Group 15 donor atoms. The iron analogues of the latter complexes (with X = Cl, Br), are obtained by oxidation of... 

The first step in the reaction of ran,.s-[Fe(salpn)(H20)2l+, salpn=A(A7v-propylene-l,2-bis-salicylidiniminate, with sulfur(IV) is the formation of [Fe(S03)(salpn)(H20)], with the pH-rate profile showing greater trans-labilization by hydroxide than by water, in that traras-[Fe(salpn) (H20)2]+, reacts 10 times less rapidly than traras-[Fe(salpn)(OH)(H20)]. A limiting dissociative (D) mechanism is proposed for reaction of the latter formation of the sulfito complex is followed by a slow intermolecu-lar redox reaction (346). A similar situation prevails for the analogous irans-[Fe(salen)(H20)2]+/sulfur(IV) system (347). 

The most controversial issue is the number and exact stoichiometries of the iron(III)-sulfito complexes formed under different experimental conditions. Earlier, van Eldik and co-workers reported the formation of a series of [Fe(SO ) ]3-2" (n = to 3) complexes and the [Fe(S03)(0H)] complex (89,91,92). The stability constants of these species were determined by evaluating time resolved rapid-scan spectra obtained from the sub-second to several minutes time domain. The cis-trans isomerization of the complexes was also considered, under feasible circumstances. In contrast, Betterton interpreted his results assuming the formation and linkage isomerization of a single complex, [Fe(SC>3)]+ (93). In agreement with the latter results, Conklin and Hoffmann also found evidence only for the formation of a mono-complex (94). However, their results were criticized on the basis that the experiments were made in 1.0 M formic acid/formate buffer where iron(III) existed mainly as formato complex(es). Although these reactions could interfere with the formation of the sulfito complex, they were not considered in the evaluation of the results (95). Finally, van Eldik and co-workers re-examined the complex-formation reactions and presented additional data in support of... 

Although the above model was developed under non-catalytic conditions, some of the results may bear significance under natural conditions or in the presence of excess sulfite ions. Thus, the decomposition of the mono-sulfito complex was considered to be the rate-determining step in the catalytic cycle, but only estimates could be given for the rate constant in earlier studies. The comprehensive data treatment used by Lente and Fabian yielded a well established value for this parameter (106), which can then be used to improve previous kinetic models. Furthermore, the participation of reactions of the [Fe2(0H)(S03)]3+ complex was never considered in kinetic studies where excess sulfite ion was used over low iron(III) concentration in mildly acidic solution (pH 2.5-3.0). The above model predicts that in some cases the formation of the dimeric sulfito complex could make a substantial contribution to the spectral changes and omission of this species could lead to biased conclusions. Reevaluation of data sets reported earlier by including the reactions of [Fe2(0H)(S03)]3+ may resolve some of the controversies found in literature results. 

As noted before, many conventional methods rely on hydrolysis/precipi-tation chemistry to deposit Pt and other metals onto carbon, followed by chemical or gas-phase reduction. One common method is the use of metal sulfito chemistry. This method involves the preparation of metal sulfito complexes (e.g., Na3[Pt(S03)2(0H)2]) in water, the addition of carbon, and precipitation of metal by oxidation to deposit metal oxide particles. The route has advantages in that alkali metals and halides are excluded from the preparation. The method has been extended to bimetallics such as PtRu. 

The results of a vibrational spectroscopic study of the SO2 complexes [RuX(S02)(NH3)4]" (X = Cl, Br) and [Ru(H20)(S02)NH3)4] + have been reported the j/(sym) and j/(asym) modes of the 5 -bound SO2 ligand come at lower frequencies than those of the free molecule. The ammonium salt of the sulfito complex tra 5-[Ru(S03-5)2(NH3)4] 4H20 has been structurally characterized. Although the crystals are stable when retained in the mother liquor, the isolated compound is only stable at 298 K for several days. Relationships between the structural and vibrational spectroscopic data are discussed. ... 

O-sulfinato complex, 37 287 sulfito complexes, 37 293 sulfur, selenium, and tellurium tetrahal-ide complexes, 37 299 thiocyanato complexes, 37 264 thioether and selenoether complexes, 37 288... 

Oxygen-bonded sulfito complexes of platinum(IV) can be prepared by the reaction of aqueous sulfite with [Pt(NH3)5(H20)]4+ to give the O-bonded sulfito complex [Pt(NH3)5(0S02)]2+. This compound rearranges to the S-bonded sulfite complex, or at elevated temperatures in addic solution a single-step two-electron reduction occurs to yield a platinum(II) complex Pt(S03)(NH3)3 (equation 480).1631 The O-bonded sulfite complexes show a series of IR bands in the range 460-960 cm-1.1632... 

There are early reports of sulfito complexes of osmium, but only recently has some of this work been reexamined. It appears that osmium binds to the sulfur atom rather than oxygen in S032, even for the presumably hard osmyl unit in [0s02(S03)4]6. ... 

Many similar sulfito complexes are known 300), e.g., NH4[CuS03], [NH4]4[Cu2(S03)3]-3H20, and [NH4]g[Cu(S03)g].H20, but in the sodium and potassium series double-salt formation is even more... 

Oxygen tracer experiments 25) confirmed that the cobalt-oxygen bond remained intact throughout the reaction. The nitrito complexes of penta-amminerhodium(III), pentaammineiridium(III), and pentaammineplati-num(IV) have been obtained by the same method (5). In a similar way, adding sulfur dioxide or sodium sulfite to solutions of aquopentaammine-cobalt (III) ion at low temperatures and low pH yields the unstable pink oxygen-bonded sulfito complex rather than the stable yellow-brown sulfur-bonded isomer. 

In conclusion, the authors of paper (332) proposed that sulfito complexes are formed prior to electron transfer and, even if the results... 

Tarle 111-28. Infrared Spectra of Unidentate Sulfito Complexes (cm )... 

In an extraction-photometric method for the determination of rhenium, a sulfito complex [(Me2CHCH2CH2)2NH2]2Re0(S03)Cl2 is supposedly formed when Re is extracted from 3.2 M hydrochloric acid containing SO3 with diisoamylamine in ethyl acetate or This formulation... 

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