Stable Catalyst Motifs for CH Activation

The primary issue with the Shilov system [9], PtCl2(H20)2, that is profiosed to operate via an oxidative addition (OA) pathway, is catalyst instability due to irreversible decomposition to Pt metal or insoluble, polymeric Pt salts such (PtCyn- This can be addressed by the use of ligands as has been done with the high yield, Pt(bpym)Cl2/H2S04 system (bpym= K - 2,2 -bipyrimidyl ) [6]. This system is stable and active for the conversion of methane to methanol in concentrated sulfuric acid (Eq. 2). Yields of over 70% methanol (based on methane) with selectivities of 90% and turn-overs of -1000 have been observed with tum-over-frequencies of 10 s .  

In this system, experimental and theoretical studies show that this complex is thermally stable to strong acid solvents due to the unique stracture and composition of the bpym (bipyrimidine) ligand (Fig. 7.17) [6, 5]. 

Theoretical and experimental studies show that, as in the case of the electrophilic [XHg] system, this cationic Pt(II) catalyst also operates via an electrophilic substitution reaction pathway as shown in Fig. 7.18 and Fig. 7.19. This switch 

In this case, the inhibition limits the product concentration to -1.5 M and remains too low for commercialization. 

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