With metal halides bonding

Group-IIIB-Transition- or-Inner Transition-Metal Bonds 6.5.3. Formation from Other Group-IIIB Compounds 6.S.3.4. by Reaction with Metal Halides... 

Unlike the di-f dihalides, such compounds differ little in energy from both the equivalent quantity of metal and trihalide, and from other combinations with a similar distribution of metal-metal and metal-halide bonding. So the reduced halide chemistry of the five elements shows considerable variety, and thermodynamics is ill-equipped to account for it. All four elements form di-iodides with strong metal-metal interaction, Prl2 occurring in five different crystalline forms. Lanthanum yields Lai, and for La, Ce and Pr there are hahdes M2X5 where X=Br or I. The rich variety of the chemistry of these tri-f compounds is greatly increased by the incorporahon of other elements that occupy interstitial positions in the lanthanide metal clusters [3 b, 21, 22]. 

Ge—metal bonds can be built in analogy as described for Ge—C bonds by the reaction of organolithium compounds with metal halides. With trans-dichlorobis(triethylphosphine)platinum(II), new germyl transition metal complexes were synthesized (equation 36)41. 

These Sn/Li transmetallations involve nucleophilic attack of an alkyl anion at the tin center. Transmetallations with metal halides on the other hand involve electrophilic attack of the metal at the allylic double bond. 

In this context it is interesting to note that benzonitrile, Ph—C=N, trimerizes to a triazine on a Raney nickel surface. It was assumed that Jt-bonded nitriles were involved in the reaction mechanism.10 This reaction resembles the well-known template synthesis of phthalocyanine complexes from phthalodinitrile. Formation of linear polymers [—C(R)—N—] occurs on heating aryl or alkyl cyanides with metal halides.11... 

The mechanism of hydrogen evolution has been investigated by impedance measurements [371] and hydrogen-tritium kinetic isotope effects [375]. The effect of halides dissolved in solution has been studied [372, 376] these ions increase the overpotential in the sequence Cl- Adsorption isotherms for halides have been derived. They conform to the Temkin adsorption model with partial charge transfer. The lateral interaction between adsorbed particles has been calculated. It is higher for Br- than for I- and increases with overpotential on account of the weakening in the metal-halide bond. Thus, halides are substantial poisons for hydrogen evolution on iron. Poisons also include metal ions such as Cd2+, Zn2+, and Mn2+ [26]. 

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