Halogeno Complexes

Halogeno-complexes. This section includes studies on oxy- and thio-halide species, and 1 1 halide adducts with a variety of donor atoms. Phase diagrams for the HF-NbFj and HF-TaFj systems have been presented. The anti- 

Hubert-Pfalzgraf, J. Guion, and J. G. Riess, Bull. Soc. chim. France, 1971, 3855. 

Fedorov, F.. G. Rakov, B. N. Sudarikov, and V. A. Starobinskii, Trudy Moskov. Khim-Tekhnol. Inst., 1970, No. 67, 89. 

Charge-transfer interactions have been observed between NbFj and MX4 (M = Si, Ge. or Sn. X = alkyl M = C, Si, or Sn, X = Cl) and several organic solvents, and for NbClj and TaClj with aromatic hydrocarbons and fluorocarbons. Tn these latter cases the enthalpies of interaction were estimated as 6.3 kJ mol The new complexes [MF L] (M = Nb or Ta, L = DMSO, EtCN, or CH CICN), [TaF, 2-Mepy)]. and [tap5(4-Mepy)2] have been prepared. Their vibrational spectra have been recorded and. together with those of [MF5(MeCN)] and [MFjLJ (M = Nb or Ta and L - DMSO or py), discussed in terms of MFjL and [MF L4][MFg] structures.  

New H n.m.r. methods for determining the relative stability constants have been developed and used to study the 1 1 adducts of NbClj and TaClj with a series of ethers, sulphides, and nitriles. 

Protactinium(V) is stable in aqueous hydrofluoric acid at quite high concentrations, but irreversible hydrolytic condensation occurs in other halogen acid solutions even at protactinium(V) concentrations of the order of 10 to 10 M. Consequently, only fluoroprotactinates(V) have been prepared in aqueous solution. Raman studies (97) have established 

Since protactinium(IV) is readily oxidized in the atmosphere halo-genoprotactinates(IV) must be prepared in oxygen-free solvents or by heating the component halides together in an inert atmosphere. It is reported that solvent extraction studies have established the existence of the fluoro and chloro species PaX + and PaX + in aqueous acid solution (S2) 

Potassium heptafluoroprotactinate(V), K2PaF7, was first prepared (79) by reacting PaF5-2H20 with potassium fluoride in water. However, this and other heptafluoro complexes (M = NH4, Rb, and Cs), for which the solubility in water increases with the size of the unipositive cation, are conveniently precipitated from 11 M hydrofluoric acid solution by the addition of acetone (37). Li2PaF7 and Na2PaF7 are not obtained by 

Protactinium(V) octafluoro complexes, MlPaF, have been prepared (5, 35, 37, 59) by precipitation from aqueous hydrofluoric acid (M = Li, Na, and Rb), by heating the alkali metal fluoride with the corresponding heptafluoro complex in argon (M = K and Cs) or by fluorinating the product obtained by evaporation of a hydrofluoric acid solution containing 3 1 mixtures of MF and Pa(V). 

The protactinium(V) fluoro complexes are all air-stable, white solids. Available crystallographic data are compared with those for analogous actinide complexes in Tables V and VI. Of the hexafluoro complexes only AgPaFg, LiPaFg, and NaPaFe have not been characterized structurally. The remaining complexes and certain of the hexafluorouranates(V), 

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Numerous tetrahedral halogeno complexes [T1" X4] (X = Cl, Br, I) have been prepared by reaction of quaternary ammonium or arsonium halides on TIX3 in nonaqueous solution, and octahedral complexes TI "X< ] (X = Cl, Br) are also well established. The binuclear complex Cs3[Tl2"Cl<)J is an important structural type which features two TlCls octahedra sharing a common face of 3 bridging Cl atoms (Fig. 7.9) the same binuclear complex structure is retained when Tl " is replaced by Ti ", V ", Cr " and Fe " and also in K3W2CIS and CssBiily, etc. 

A fascinating variety of discrete (or occasionally polymeric) polynuclear halogeno complexes of As, Sb and Bi have recently been characterized. A detailed discussion would be inappropriate here, but structural motifs include face-shared and edge-shared distorted (MXe) octahedral units fused into cubane-like and other related clusters or cluster fragments. Examples (see also preceding paragraph) are ... 

Similar halogeno complexes are produced in solution, and several salts of [HgXs]" have been isolated and characterized they display a variety of stereochemistries. In [HgCl3] the environment of the Hg is either distorted octahedral (with small cations such as NHj" "... 

Thermodynamics of Plutonium Halides and Halogeno Complexes in the Solid State and in Aqueous Media... 

In spite of well identified deficiencies, the status of the existing thermodynamic data on solid halides and related compounds is rather satisfactory. By contrast, the data on aqueous halogeno-complexes are fragmentary, sometimes contradictory and in most cases limited to stability constants in such a context, recommendation of best values can be made for a few species only. 

Mossbauer studies on gold compounds were first reported by Roberts et al. [337] and Shirley et al. [338, 339]. They observed rather large isomer shift changes in some simple gold (I) and gold (III) halides and in halogeno-complexes such as AuX (X = Cl, Br, I), AuXj (X = F, Cl), K[AuX4] (X = F, Cl, Br), and... 

The reaction of [LnM-SiR3]" with transition metal halides or halogeno complexes L mM Xx gives silyl-substituted heteronuclear complexes [Ln(R3Si)M]xM L m [2,5,18]. Stable complexes are usually only obtained if the metal complex fragment M L m is not too sterically demanding and if the resulting M-M bond is not too polar. A few examples are shown in Scheme 3. 

Carbonyl Halides and Hydrides. Fe2(CO) reacts with HBr or HI and Fe(CO)j with HBr under u.v. light to yield the halogeno-complexes [Fe(CO)3.X]2. Structure (16) is postulated, on the basis of the close similarity in i.r. spectra with those of [Fe(CO)3SR]2 complexes. 

S- and P-donor ligands. The complexes [(YPPh2 CH PPh2Y)2Fe] (Y = S or Se) are prepared by treating (Ph2PY)2CH with Bu"Li, followed by addition of an Fe" halogeno-complex anion. The complexes are both tetrahedral and the Se complex is the first example of tetrahedral co-ordination of Se to Fe". ... 

Ph2PY)2CH2 with Bu"Li followed by addition of metal halogeno-complex anions. Both compounds are tetrahedral and the Se complex is the first example of a tetrahedral [CoSe ] core. The tetrahedral [Co(S2AsMe2)2] ° and [Co(WOS3)2] "" " have been reported, the latter having only co-ordinated sulphur atoms. 

Ni(SSePPh2)2], and the complexes [NiCYPPh CH Ph2PY)2] (Y = S or Se) have been prepared by deprotonation of (Ph2PY)2CH2 with BuLi followed by addition of a nickel halogeno complex anion. Both complexes are planar. ... 

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