Rhenium iodide

Several rhodium(I) complexes have also been employed as ATRP catalysts, including Wilkinson s catalyst, (177),391 421 422 ancj complex (178).423 However, polymerizations with both compounds are not as well-controlled as the examples discussed above. In conjunction with an alkyl iodide initiator, the rhenium(V) complex (179) has been used to polymerize styrene in a living manner (Mw/Mn< 1.2).389 At 100 °C this catalyst is significantly faster than (160), and remains active even at 30 °C. A rhenium(I) catalyst has also been reported (180) which polymerizes MM A and styrene at 50 °C in 1,2-dichloroethane.424... 

The external rhenium unit is removed from 92 through iodine oxidation, and its place is taken by an iodide ligand in 93 (7 74). The reactivity of iodine towards clusters therefore can lie in one-electron oxidation (Section II), electrophilic attack (Section III,B), or partial degradation. 

Potassium chlororhenite has been prepared by reducing potassium perrhenate with potassium iodide in hydrochloric acid solution.1-4 The identity of the product has been questioned, and various formulae have been assigned to the compound. The difficulties encountered in obtaining a pure product were probably due to the inclusion of a double chloride of potassium and pentavalent rhenium. It is known that the primary reduction involves formation of pentavalent rhenium. 

Rhenium complexes 22a,b were designed as ditopic receptors for the cooperative complexation of ion pairs [21]. As proved by H NMR titration experiments in CD3CN,the receptors form complexes of 2 1 stoichiometry with alkali metal cations (interaction with both ethyl acetate cavities on the lower rim) and exhibit [16] a positive allosteric effect for iodide complexation compare... 

This is, as expected, the rarest oxidation state as far as non-organometallic complexes of rhenium are concerned. The dirhenium phosphite complex Re2[P(OMe)3]10 has been prepared12,13 in low yield by several methods, viz. the potassium-potassium iodide reduction of ReOCl3(py)2 or an ReCLj-pyridine complex, followed by treatment with trimethyl phosphite. This yellow complex displays a 31P H) NMR spectrum that appears as a first order AB4 pattern, and is isoelectronic with Re2(CO)l0. It reacts with H2 upon photolysis in THF solution to produce hydridorhenium(III) and other species.13 The related triphenyl phosphite derivative Re2[P(OPh)3]l0 has been described14 as a product of the reaction between ReH3(PPh3)4 and P(OPh)3. 

Treatment of an ethereal solution of lithiated bis(7r-cyclopenta-dienyl)rhenium hydride, (C5H4Li)oReH, with an excess of methyl iodide yields a rather unstable yellow compound of composition CisHmRe (125). The infrared and NMR spectra indicate that the complex is (methylcyclopentadiene)(cyclopentadienyl)dimethylrhenium for which the structure (48) has been deduced by X-ray analysis (5). The methyl-... 

The iodide reaction was first studied by incremental addition of thiosulphate ( The method of constant rates ) . This use of the method was attacked by Bell . Bray s work established the two rate terms shown in Table 28. The reaction has also been studied in the presence of arsenite , which does not interfere as thiosulphate does, and kj =3.3x10 l .mole .sec at 25 °C. Catalysis of the reaction has been demonstrated in presence of vanadium(IV) , ruthenium(III) , rhenium(II) osmium tetroxide " and iron(III) , together with retardation by Mn(II) - Ni(II) and chloride . These measurements were made at moderate acidities and appear to involve quite different dependence of rate on acid concentration from the reaction in absence of catalyst (half-order for Ru(OH), first-order for Re ). The mechanisms may also be quite different. 

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