Halogens transition-metal halides

The metal-metal bonds in the complexes [M(CO)4(Sime3)]2 are readily attacked by halogens, triphenylphosphine, trimethylsilane, and sodium amalgam. Sodium amalgam produces the anion [M(CO)4(Sime3)] which reacts with main-group or transition-metal halide species to give a series of new complexes,74, 160>161) e.g. 

Table 9. Halogen nuclear quadrupole resonance frequencies of some transition metal halides forming molecular crystals or one dimensional polymers...

The synthesis of transition metal alkyls usually involves the interaction of a very reactive metal alkyl, with a transition metal halide or alkoxide. This approach necessarily involves having two metals in the system which considerably complicates the problem of isolation of single pure compounds. In addition, low-valence transition metal compounds are electron-deficient molecules, and, for this reason, they will attempt to expand their coordination number by sharing ligands (halogen, alkyl, etc.) between two metal centers with the formation of bimetallic complexes. 

Wilkinson and coworkers obtained stable alkyl complexes by the reaction of transition metal halides or complex halides with trimethylsilylmethyl lithium 72 With these alkyl complexes, no /3-elimination reaction proceeds. The action of Grignard or organolithium reagents on halogen complexes of Pt(II) and Pd (II) has been widely used for the preparation of alkyl complexes, and quite stable alkyl complexes of noble metals can be prepared 73K... 

Transition metal halides LmMX (L = ligand, X = halogen, m = 0, 1, 2. . . ) undergo multiple reduction with BSD. The reaction products are transition metal halides LmMX p in lower oxidation states, complexes such as LmM, or the metal itself (49). The products, LmMX p, LmM, or M can, in some cases, react further with BSD to form complexes (cf. Section VII). In this way, BSD in methylene chloride transforms titanium tetrachloride, TiCl4, to titanium dichloride which, being a very mild oxidizing agent, is incapable of further reduction (with BSD) to the metallic state (50) [Eq. (90)]. Complete reduction to the metallic state, on the other hand, has been observed... 

Halogens Lewis acids Protonic acids Transition-metal halides... 

A successful ATRP reaction depends on the reversible activation of a dormant species, such as an alkyl halide (R—X), by a transition metal halide catalyst (MpY/L). The metal halide catalyst abstracts the halogen atom (X) from the dormant species to... 

Table 2. Physical properties of transition metal halides. The heat of formation data was taken from [99C] and the stmctural data from [65Wj. The structures listed are for the most stable phase at 300 K. The column labeled "Minimum Interhalogen Distance" lists the halogen nearest neighbor separations for those halides that form structures with close-packed halogen planes.

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