Distibine

Distibines and Distibenes. A considerable number of tetraalkyl- and tetraaryldistibines have been investigated. These are usually obtained by the reduction of a dialkyl- or diaryUialostibine with sodium hypophosphite (111,112) or magnesium (108,116). Distibines can also be prepared by the treatment of a metal dialkyl- or diarylstibide with a 1,2-dihaloethane (70,71,77,85,91,128)... 

Unlike many distibines and dibismuthines, diarsines do not appear to exhibit thermochromic effects (105). 

Disiloxane, tetramesityl-, 3,206 Disproportionation iridium catalysts, 4,1159 Dissolution nuclear fuels, 6, 927 Distannene, 3,217 Distannoxane, 1,3-dichloro-, 3,207 Distibine, tetraphenyl-, 2,1008 Distibines, 2,1008 Disulfido ligands metal complexes, 2,531-540, 553 bonding, 2, 539 electron transfer, 2, 537 intramolecular redox reactions, 2,537 reactions, 2, 537... 

Syntheses and Solid State Structures of Group 13-Distibine... 

Structures 5 and 6 display the solid state structures of two representative distibine and dibismuthine adducts. The ligands bound to the central Sb and Bi atoms adopt a staggered conformation in relation to one another, with the bulky M(t-Bu)3 groups arranged in a trans-position. This is likely due to repulsive steric interactions. The central Sb—Sb [281.1(1) 32 283.9(1) pm 35] and Bi—Bi bond distances [298.3(1) 36 and 298.4(1) pm 37] are almost unchanged compared to the uncomplexed distibines and dibismuthines, as can be seen... 

An intermolecular analog of this inter-ring pnictogen bonding is found in the thermochromic distibines and dibismuthines.45 For example, 2,2, 5,5 -tetramethylbistibole (87) crystallizes so that the Sb atoms are aligned in chains with close contacts between the Sb atoms of adjacent molecules. It seems more than coincidental that the intermolecular contacts in 87 occur at virtually the same distance as the intramolecular contacts in 29. See Figure 3. 

An alternative preparative route to R2QER acid esters (Q = P, As, Sb, Bi E = S, Se, Te) of interest due to its generally applicability to all the heavier group 15 and 16 elements, is the dismutation reaction between diorganodichalco-genides and tetraorgano-diphosphines, -diarsines, -distibines or -dibismuthines (Equation 17).2... 

Preceding reviews on distibines, R2Sb-SbR25,7,66-68 feature mainly the structural aspects in relation to the thermochromic properties of some of these compounds, but also overviews on the earlier work of the coordination chemistry of distibine ligands have been reported.7,68 All the distibines that... 

Distibines react as monodentate (type 5) or bridging bidentate (type 6) ligands through donation of the lone pairs of electrons to main group or transition metal centers. Fission of the Sb-Sb bond leads to complexes with bridging R2Sb ligands (type 7, 8 and 9) (Scheme 3). 

In order to describe the different conformations in distibines or in distibine complexes, the torsion angles Ep-Sb-Sb-Ep (cp) for the free ligand... 

Bidentate coordination leading to bis-adducts is observed in reactions of distibines with aluminium or gallium trialkyls in absence of solvent at low temperatures (Equation 2).76... 

The bis-adducts are stable in the solid state at low temperatures. They dissociate in solution at ambient temperature. In the case of Me2Sb-SbMe2 a stable complex was formed only with the sterically hindered and less electrophilic t-Bu3Al. X-ray crystal structure analyses for [( -Bu)3M(R2Sb-SbR2)M( -Bu)3] (R = Me, Et M = Al, Ga) revealed that the distibine ligands adopt the anti conformation (Structural parameters of distibine complexes are summarized in Table I. 

A general reaction of binuclear distibine complexes is the fission of the Sb-Sb bond and transformation of the R2Sb-SbR2 into a R2Sb groups. 

Fission of the Sb-Sb bond is even more facile in the distibine-group 13 element complexes and with migration of an alkyl group four- and six-membered heterocycles (type 7 and 8) are formed.76,82... 

In these mixtures the catena-tvistibines are by far the most abundant chain species and even under favorable conditions [excess of cyc/6>-(RSb) ] the caten -tetrastibines form only as minor components. Nevertheless, recently the selective extraction and stabilization of these tetrastibines in the coordination sphere of a transition metal carbonyl complex was achieved by reacting mixtures of distibines and cyclostibines with... 

In sharp contrast to the intensely studied reactions of dipenteles with transition metal compounds, reactions with group 13 metal compounds are almost unknown. Only two diphosphine-borane bisadducts of Type C ([H3B]2[Me4P2], [H2(Br)B]2[Me4P2]) have been synthesized and structurally characterized65 but no diarsine, distibine or dibismuthine adducts. We, therefore, became interested in the synthesis of such compounds, focusing... 

Bond Lengths [pm] and Angles [°] of Distibine Adducts and Pure Distibines... 

Scheme 10. Proposed reaction mechanism for the distibine cleavage reaction.

Diels-Alder reactions, 160-161, 163 Dissociation enthalpy, 229-232, 236, 237, 247 Distibines, 251, 253, 254, 263-265 adducts, 252-255 ligands, 99-106, 124, 125 Dmap-stabilized monomers, 276-291 Dodecatrienediyl-Ni11 complex, 169,... 

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