Copper monohalides

The same paper describes the reaction of trialkyl phosphites with isatin arylazomethines in the presence of nickel or copper monohalides, leading to the previously unknown phosphorus-containing derivatives of 2-indolinone 68 ... 

A possibility of obtaining complexes 153 involving P(III)-containing indoles 4a and copper monohalides has been demonstrated [17] ... 

Passing back to the boron group, if it is desired to form anhydrous chloride, it is necessary either to heat the element, or its oxide mixed with charcoal, in a current of chlorine, or, except in the case of boron, to prepare a double salt of the chloride with ammonium chloride, and to volatilise the latter after driving off the water the aqueous chlorides are formed by dissolving the oxides or hydroxides in hydrochloric acid. Thallium forms monohalides, sparingly soluble in cold water, and thereby attaches itself to the copper group. 

These early successes with carbonyl complexes of rhenium encouraged me to undertake systematic research on the carbon monoxide chemistry of the heavy transition metals at our Munich Institute during the period 1939-45, oriented towards purely scientific objectives. The ideas of W. Manchot, whereby in general only dicarbonyl halides of divalent platinum metals should exist, were soon proved inadequate. In addition to the compounds [Ru(CO)2X2] (70), we were able to prepare, especially from osmium, numerous di- and monohalide complexes with two to four molecules of CO per metal atom (29). From rhodium and iridium (28) we obtained the very stable rhodium(I) complexes [Rh(CO)2X]2, as well as the series Ir(CO)2X2, Ir(CO)3X, [Ir(CO)3]j (see Section VII,A). With this work the characterization of carbonyl halides of most of the transition metals, including those of the copper group, was completed. 

The monohalides of the coinage metals, with the exception of AgF, are almost insoluble in polar solvents. Copper(I) halides all have the zinc blende structure they show a predominantly covalent character in agreement with the observed lattice energies (p. 92) (Table 130). 

Carbothermic reduction in the presence of an alloying element, such as copper, iron, or silicon, to decrease aluminum vapor pressures decreases volatility problems but requires a further stage to recover aluminum from the alloy product. It may be selectively dissolved from the alloy with a more volatile metal, such as mercury, lead, or zinc, and then the aluminum recovered by distillation. Or, the tendency for aluminum halides to form more volatile monohalides at high temperatures, which revert to the trihalides at lower temperatures (Eq. 12.25) may be employed. 

Zinc in various solvents, most frequently acetic acid and ethanol, is a powerful reducing agent for monoreduction of 1,1-dihalocyclopropanes. Mechanistic studies indicate that cyclopropyl radicals as well as cyclopropyl anions, are involved as intermediates. In most cases the monohalides are obtained as stereoisomeric mixtures. Typical examples are compiled in Table 3, other examples can be found in refs 38,42,47, 51,69,108,112-121,774,782 (dibromo derivatives), refs 108, 112, 122, 762, 777, 888, 936 (dichloro derivatives), ref 47 (bromofluoro derivatives) and ref 112 (bromochloro derivatives). Thus, reduction of 2,2-dichlorocyclopropyl-methanol using a mixture of zinc and copper(II) chloride in ethylene glycol gave 2-chlorocyclo-propylmethanol (30) in 74% yield as an equimolar mixture of the cis- and tranj-isomers. ... 

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