Solid state cyclometallation

The reaction involves orthometallation of two aromatic rings with formation of two five-membered metallocycles. DTA/TG and mass-spectrometric analyses were performed to study the thermal process under a nitrogen atmosphere. In general, dehydrohalogenation reactions are not well suited to study by thermal analysis methods because evolution of corrosive hydrogen halides is deleterious to the equipment. 

Two distinct pathways for this reaction have been suggested oxidative addition of the C-H bond followed by reductive elimination of HCl, and direct electrophilic attack on the formyl group by platinum(II) with displacement of a proton. 

For complexes with P-donor ligands, metallation often occurs in solution with elimination of an alkane and such reactions also occur in the solid state. For example, the solid state cyclometallation of [PtMe2 PMe2(l-naphthyl) 2l has been investigated. When heated to 200 C, the complex evolved methane (monitored by IR spectroscopy) and gave a product cyclometallated in the 8 (peri) position, containing a stable five-membered 

The majority of N- and 0-donor ligands form five-membered rings in cyclometallation reactions. In contrast, S- and P-containing ligands show a tendency to form three- and four-membered rings, especially when formation of a five-membered ring is precluded. 

The his-chelate complex was prepared by slow heating in vacuo at 180 C and contains metallated nitrogen and phosphorus donor ligands in six- and four- 

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Solid state cyclometallation that results in the formation of two different chelate rings has been demonstrated by Canty and Minchin, Scheme 12.15 ... 

The solution and solid state structural features of the optically pure [Rh(TpMenth)(CO)2] have been reported, TpMenth being found in both k2- and k3-coordination modes. The optically active TpMenth and XpMementh are able to control the stereoselectivity of the C-H bond activation by their coordinated rhodium center. Irradiation of [Rh(TpMenth)(CO)2] under N2 resulted in the generation of an 85 15 mixture of diastereomeric alkyl hydrides due to intramolecular cyclometalation reaction involving the methyl substituents on the ligand isopropyl group (Fig. 3.51).240... 

Two cyclometallated iridium(III) complexes were developed by Li et ah, one showing increased luminescence in the solid state. This feature was exploited by inserting the complex into polymer nanoparticles and visualised in epidermal carcinoma (KB) cells. Furthermore, an exciting development towards multimodal imaging and with theranostic potential was carried out by Hsiao et al. using multi-purpose silica-coated iron oxide nanoparticles functionalised with an iridium complex for MRI, in vitro phosphorescence imaging and photodynamic therapy." ... 

Solid-state thermolysis of 1 -alkyl-2,4-bipyridinium palladium complexes gave cyclometallated complexes [PdCl2(2,4 -R-bipy-H)] (R = H, Me, Bu, CsHu, CgHi, or C10H21) in quantitative yield. ... 

Yang C-H, Li S-W, Chi Y, Cheng Y-M, Yeh Y-S, Chou P-T, Lee G-H, Wang C-H, Shu C-F (2005) Heteroleptic cyclometalated iridium(III) complexes display blue phosphorescence in solution and solid state at room temperature. Inorg Chem 44 7770-77780... 

The thermolysis of the zwitterionic platinum and palladium(Il) compounds [M(Cl)3(2- />-N-alkylpyridinium pyridine)]proceeds by loss of hydrogen chloride and the formation of a five membered cyclometallated ring. In the solid state longer alkyl groups (CgHn and C10H21) make the metallation easier than for the methyl to hexyl derivatives. The reverse applies in aqueous solution... 

Cyclometallation reactions that occur in solution are very well documented and such reactions often involve dehydrohalogenation. A solid state orthometallation reaction that occurs via dehydrohalogenation S has been reported. Scheme 12.13 ... 

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