1,1.1-Trihalides from 2 molecules

When looking for other molecules with lone electron-pairs that perhaps will combine these electrons with d electrons of platinum metals, there are, first of all, the trihalides of the nitrogen-phosphor group of elements. Complexes formed from chlorides of the platinum... 

Being powerful acceptors, the gallium trihalides react with donor molecules L to form the adducts GaX3-L, and in some instances GaX3-2L, with a coordinate bond from the group V or VI ligand, which are treated in earlier sections. 

The arsenic trihalides have been shown by a variety of techniques (Table 9) to be pyramidal molecules in the gas phase. The X—As—X angles increase from X = F 96° to X = I 100°. The d(As—X) values increase with increase of temperature,53 and the X—As—X angle changes in proportion. 

Alkyl tellurium halides, RTeX, in general, have no importance as starting materials for the preparation of alkyl tellurium trihalides. The alkyl tellurium halides are synthesized from dialkyl ditellurium compounds and elemental halogens. When alkyl tellurium trihalides are the desired products, there is no reason to prepare the monohalides first. However, when the tellurium monohalide is formed during the introduction of tellurium into an organic molecule, the reaction of this primary product with halogens is the method of choice for the preparation of the tellurium trihalides. This situation is realized for 3-oxo-l-propen-l-yl tellurium halides2,3. 

The unsaturated character of these trialkyl esters was shown by the ease with which they were attacked by nitric acid, but still more clearly by the formation, with evolution of heat, of stable crystalline addition compounds when they were mixed with cuprous halides. Thus CuC1.P(OC2H5)3 was described as consisting of colourless crystals melting at 190° to 192° C. and soluble in organic solvents.4 This property they share with phosphine, alkylphosphines and phosphorus trihalides. The phosphoric esters were quite indifferent to cuprous halides. Nor were such addition compounds formed either by phosphorous acid itself or by the dialkyl esters, which may show that the latter compounds have the unsymmetrical formula. Phosphorous acid probably exists in both forms, but first as P(OH)3, i.e. when produced from PC13 and Ha0.5 This may be transformed into the unsym-metrieal form through an addition compound HC1.P(0H)3,4 and probably also exists in the form of complex molecules, such as... 

Reaction of a donor molecule with a previously equilibrated mixture of free boron trihalides gives an initial adduct mixture corresponding to the equilibrium mixture of the free boron trihalides. This method should be suitable for all mixtures except BF3/BI3 (as noted previously). However, equilibria in the adducts can be quite different from the corresponding equilibria in the free boron trihalides. If halogen redistribution is fast and if the mixed adducts are discriminated against, then this method does not succeed (28). 

Figure 6-43. The two types of structures that might result from an e -type vibration of a metal trihalide molecule.

The dimeric trihalides form discrete molecules (Fig. 6-2). The halides dissolve readily in aromatic solvents such as benzene, in which they are dimeric. As Fig. 6-2 shows, the configuration of halogen atoms about each metal atom is far from ideally tetrahedral. The formation of such dimers is attributable to the tendency of the metal atoms to complete their octets. 

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