Antimony halides, halide complexes

Antimony(III) halides are powerful halide acceptors and form complexes with, for example, monovalent halides to give a variety of interesting structures, e.g. (54)-(56). The tetramethyl-ammonium nonabromodiantimonate(III) dibromine is of interest since the crystal structure contains bromine molecules which bridge the [Sb2Br9]3 anions (56).158... 

One of the more notable features of antimony(V) halide chemistry is the tendency to achieve a CN of six, thus resulting in the facile formation of complex anions, particularly with halide donors (Table 21) the d(Sb—F) depends on the nature of the cation. Their structures are related to the F—Sb- -F interactions between crystal structure units, which is dependent upon the potential field of the cation. 

Hydrogen bonding is so common that coordinate bonds between other elements are sometimes overlooked. Antimony(Ill) halides form very few complexes with other halides, whereas aluminum halides readily form complexes. The octet of electrons is complete in all atoms of the antimony halides, but is incomplete in die aluminum atom of aluminum halides ... 

Aluminum can accept two electrons to complete its octet. The pair of electrons is available from the halogen. An alkali halide can supply the electrons and form a complex (c), or the electron pair may come from the halogen of another aluminum chloride. Association with other aluminum halides accounts for the higher melting point of aluminum halides over antimony(lll) halides which have a formula weight of 95 or more. The association of aluminum sulfate, alkali metal sulfate, and water to form the stable alums is one of the more complex examples. 

Several intermediate antimony halides, such as (SbF3)I(SbF5)y, with jc = y — 1 x = 6 and y = 5 x = 2 and y = 1 x = 3 and y = 1 are known. Their existence, and their structures, depend on the high fluoride ion affinity of SbF5, whereby SbF6 and Sb2F i ions and complex polymeric cations, such as (Sb3Fg ) are formed. 

Finally here, it is useful to note that arsenic tribromide forms a 2 1 complex with hexaethylbenzene , with a structure similar to those of the Menshutkin complexes, obtained from antimony halides and arenes (see Section III.A.6). Complex formation between AsClj and both 15-crown-5 and [2.2.2]paracyclophane has also been investigated. 

Mesitylene " and hexaethylbenzene each give 1 1 complexes with half-sandwich structures with antimony trichloride and a similar 1 1 complex is known for the tribromide with mesitylene. The 2 1 adduct of antimony tribromide with biphenyl is centrosymmetric with a molecule of the antimony halide coordinated to each phenyl group and on opposite sides a similar picture is found with 2SbCl3.(2,2 -dithienyl), 2SbBr3-(9,10-dihyd-roanthracene) and 2SbCl3. (pyrene) . In the complex of [2.2.2]paracyclophane with two molecules of SbCl3, two of the benzene rings are almost symmetrically coordinated to antimony . 

Bismuth trichloride forms a 1 1 Menshutkin-like complex with mesitylene " and a 2 1 complex with hexamethylbenzene , in which the arene is bonded to bismuth at distances to the ring centre of ca 3.1 A. As with the related antimony complexes, there are also a number of intermolecular chlorine bridges, raising the bismuth coordination number and leading to either sheets or tetrameric bismuth chloride networks. These compounds differ from the antimony halide analogues where the arene is usually acentrically bonded. 

Antimony has a great affinity for charged sulfur ligands which include thiolates, xanthates (R0CS2 ), dithiocarbamates (R2NCS2 ), and dithiophosphates ((RO)2PS2 ). In contrast to arsenic, where this chemistry is limited to oxidation state III, antimony forms compounds in oxidation states III and V. The xanthate, dithiocarbamate, and dithiophosphate complexes are mostly made by reaction of antimony(III) halides or organohalides with Na, NH4, or Ag salts of the acids. Complexes... 

Photoelectron spectra for the antimony trihalides and Sb, Cl, and Br n.q.r. spectra for a number of adducts of the trichloride and bromide have been reported. The complex SbCl3,GaCl3 has been isolated, whereas a simple eutectic only is observed in the SbCl3-AlCl3 system. Antimony and bismuth halide complexes with substituted l,2-dithiol-3-thiones can be obtained, and the... 

Antimony(m) and bismuth(iii) halides form complexes with one or three... 

Interesting examples of self-assembly are provided by the arene complexes of antimony halides (so-called Menschutkin-type complexes). The addition compound between benzene and antimony trichloride, C6H6-2SbCl3, has been known for a long time [407, 408], but its crystal structure has been determined by X-ray diffraction only recently [409], It consists of SbCls molecules r-bonded to both faces of the benzene ring, to form an inverse sandwich moiety, 164. Further secondary Sb - bonds connect these tectons into a self-organized layer structure. 

Some other arene-antimony halide complexes have been structurally characterized all have intermolecular secondary Sb - -X interactions and supramolecular self-organization. Examples are naphthalene-2SbCl3 [414], phenanthrene-2SbCl3 [415], pyrene-2SbBr3 [416], and [(SbCl3)2(//- / -[2 ](l,4)cyclophane].v-0,5C6H6 [417], In the naphthalene complex [414] pairs of SbCl3 molecules are interconnected in planar stacks, with shorter primary bonds (axial Sb-Cl 2.367 A, equatorial Sb-Cl 2.347 A) and intermolecular distances Sb- -Cl 3.581-3.832 A. 

Fig. 2.6. Isomer shifts for systems with pyramidal geometry (a) antimony(lll) halides and chalcogenides, and (b) tin(ll) complexes, Et4N(SnX2Y) (X, Y = F, Cl, Br, 1). The isomer shifts are relative to InSb for the antimony compounds and relative to SnOj for the tin complexes.

Fromherz and his colleagues began in 1927 a study of the halide complexes of the family tin(II), thallium(I), and lead(II), > > where the corresponding gaseous ions contain two s electrons. The present author has measured antimony(III), while Hume and Newman studied bismuth(III). This family became interesting to solid state physicists investigating the mixed crystals with alkali halides, and Seitz proposed, 1938, that the weaker band of T1(I) in such crystals is caused by the atomic transition Sq(6s ) —> Pi(6s6 ), while the stronger band is caused by... 

---