Dimethylbenzylamine cyclometallation

Many different palladium complexes have been used to form chelates via cyclometalation. Li2PdCLi is preferred over PdCb for solubility reasons. Also commonly used are (PhCN)2PdCl2, Pd(OAc)2, Pd(02CCp3)2, and Pd(acac)2. Where amines are the donor atom, dozens of different ligand types have reacted to form five-membered C,N-chelates. These include Al,Al-dimethylbenzylamines (23) and 3,2 -dimethylene-2-phenylpyridines (24). 

Scheme 6.3 Computed reaction profile (kcal/mol) and key distances (A) for the cyclometalation of Pd(OAc)2 with iVAl-dimethylbenzylamine via an agostic interaction [24]...

As for the computer chemistry of cyclometalation reactions, the reaction with the most representative substrate, A,A-dimethylbenzylamine in a palladium compound, was studied. This reaction proceeds very easily, and its intermediate state, or agostic interaction, is therefore not actually isolated. As shown in Scheme 6.3, however, the activation energy for the agostic interaction is only 13 kcal/mol. It may be pointed out that the acyl group assists the formation of the agostic interaction in the reaction, as exhibited by the agostic intermediate 6.6 shown in Scheme 6.3 [24]. 

In the cyclometalation reaction of A,A-dimethylbenzylamine with palladium acetate, palladium acetate is thought to play the dual roles of electrophilic activation... 

The synthesis of dimethyl carbonate by reaction of CO2 with methanol generally results in a low yield, because many catalysts are deactivated by the formation of water. However, Sakakura et al. [92, 93] reported an excellent process using an acetal and a molecular sieve 3A as dehydrating agents in the presence of a Bu2Sn(OMe)2 catalyst, as described in a previous review [87, 88]. The reactions with the organotin cyclometalated with A,A-dimethylbenzylamine compounds 9.43 show promising yields of dimethyl carbonate, as shown in Eq. (9.12) [94]. 

As other applications for cyclometalation reaction five-membered ring products, they can be utilized for the compounds for CO2 fixation. For example, the pincer A,A-dimethylbenzylamine-type tin compound 9.44 readily absorbs CO2 at room temperature to yield organotin carbonate 9.45 [95]. Easy desorption and reversible CO2 fixation is achieved. 

Neutral and cationic complexes with cyclometallated A, A -dimethylbenzylamine and monodentate aminophos-phine ligands have been prepared 458-461, where the phosphine ligand occupies the position trans to the nitrogen of the cyclometallated ligand. ... 

The ethylene ligand of the Pt complex with cyclometallated 7V,7V-dimethylbenzylamine 465 may be substituted by cyclooctene to form the complex with a 7r-coordinated cyclooctene 466. The reaction proceeds via an associative pathway (Equation (114). 

The insertion of alkynes into the carbon-cobalt bond of cyclometallated compounds has also been reported for A, A -dimethylbenzylamine cobalt derivatives 96 leading to organic products and new organometallic cobalt(ni) complexes. The reaction was unfortunately limited to terminal alkynes bearing one bulky substituent, for example, SiMe3 or Bu. The reaction pathway was dependent upon the regioselectivity of the alkyne insertion into the Co-C bond, the selectivity of the product obtained being mainly a result of the steric interactions between the alkyne substituents and the CoCp unit (Scheme 12). ... 

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