Subhalides, coordination

The easily available subhalide Gal (see above) has often been employed for the synthesis of unusual secondary products. Treatment with PEt3 yielded the trigallium derivative Ga3I5(PEt3)3 (131) in moderate yield, which contains a chain of three Ga atoms.28 Each Ga atom is coordinated by a triethylphosphane ligand, and the oxidation states are + 2 (terminal Ga atoms) and +1 (inner Ga atom). The Ga-Ga bond lengths (245.6 pm on average) are as expected. 

E-C bonds, 79 E-E bond lengths, 58-59, 72 E-E bonds, 70, 73, 79-80, 83, 92 chalcogen atoms coordinating, 59-61 homoleptic dielement compounds with pnicogen atoms coordinated to, 61-65 E-E single bonds, 59, 78, 100-101 formation by coordination of subhalides,... 

There is little information on rates of initiation in coordination polymerization. With the soluble catalyst (7r-CsHs)2TiCl2—AlMejCl for ethylene, Chien [111] reported = 4.99 x 10 1 mole s at 15°C Ei = 15.5 kcal mole ). This was determined from the rate of incorporation of C14 labelled AlMe2 Cl into the polymer. In most systems examined the initiating centres have been preformed and reaction starts immediately. This is the case with Natta type catalysts from transition metal subhalides with the alkyls of aluminium, beryllium and zinc. With some catalysts the rate rises rapidly to a steady value but with others there is a rapid rise to a maximum followed by a decline to a constant rate, the latter being... 

Coordination geometries of tellurium in tellurium subhalides clearly follow from a consideration of the structural units presented in Fig. 19. Even if the conditions of chemical bonding in these units are not quite clear at first sight, they are easily integrated into accepted conc ts using the common valence rules in connection with Gillespie-Nyhohn rules and taking into account the different coordination... 

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