Metal-halogen bridges

Unusual behavior results from d7r-p7r interactions between open-shell metal ions and organic radicals as illustrated by the family of 3-D metals [Cu(R R -DCNQI)2] (DCNQI = 7V,A -dicyanoquinonediimine) (Figure 14). The halogen-bridged binuclear-metal mixed-valence complex, [Pt2(dta)4l] (dta = dithioacetate) (1-D linear chain Scheme 5a), exhibits metallic conduction above room temperature, representing the first example of a metallic halogen-bridged 1-D transition-metal complex. ... 

Group IVA Donor Ligands. The anomalous reactions of PhaSiCl with metal carbonyl anions are discussed on p. 180. Only in the case of [Co(CO)3PPh3] was the normal substitution product obtained. GeH3Br reacts with Na-[Co(CO)4] in ether to produce [H3GeCo(CO)4]. The trideuterio-compound has also been prepared and spectroscopic properties reported for both compounds. The preparation and attempted preparation of halogen-bridged Ge-M compounds is referred to on pp. 180 and 200. In the case of cobalt. 

Gallium(III) chloride also combines with other metal chlorides such as CaCls or CrCls to form mixed chlorides that have halogen bridge structures i.e., Cl4Ta(-Cl)2. Many such compounds are volatile. 

My last comment concerns the reaction of palladium olefin complexes with carbon monoxide discovered by Tsuji. I agree that this is most likely to proceed by an insertion rather than an ionic mechanism. Chloride attack on coordinated olefin is rare however. Chloride ion is an inhibitor, for example in the palladous chloride catalyzed hydration of ethylene (0). I, therefore, wondered whether carbon monoxide was affecting the ease with which chloride attacks olefin. One can postulate that carbon monoxide participates in this insertion either as a gas phase reactant or by first forming a carbonyl olefin complex. Such complexes of the noble metals were unknown, but examining the reaction between carbon monoxide and the halogen bridged olefin complexes of platinum revealed that they are formed very readily... 

A considerable number of NQR studies have been made on zinc and cadmium complexes, for example, the 35C1, 81Br and 127I NQR spectra of a number of CdX2-polyether complexes have been reported and indicate that the compounds are dimeric in solution, with symmetrical halogen bridges between the metal atoms.69 A number of amino acids and peptide complexes of cadmium(II) have been investigated by 14N NQR spectroscopy.70... 

Both 1 1 and 2 1 complexes of Af,.ZV-diethyl- and N,iV-dimethyl-thiourea with zinc, cadmium and mercury halides have been prepared. The 2 1 complexes are either monomeric and tetrahedral or polymeric and halogen-bridged with octahedral metal coordination the 1 1 complexes also possess a polymeric, halogen-bridged structure, but with tetrahedral metal coordination.894 5... 

Asymmetry of halogen bridges arising from the geometry of the coordination arrangement of the metal is illustrated by compounds containing five-coordinated metals, with an idealized arrange-... 

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