Platinum cyclometalated

The cyclometallated palladium and platinum derivatives of trimesityl phosphine or arsine react with pyrazole or 3,5-dimethylpyrazole to form metal chelates 243 (E = P, As M = Pd, Pt R = H, Me) having the trans configuration (81TMC24). 

Cyclometallation of thiophene imine 110 with platinum complex 111 proceeded to give metallacycle 112 via an intramolecular C-H insertion on the thiophene ring . 

The ruthenium(II) polypyridyl complexes are also popular but the brightnesses do not exceed 15,000 and thermal quenching is rather significant. This property can be utilized to design temperature-sensitive probes providing that the dyes are effectively shielded from oxygen (e.g., in polyacrylonitrile beads). Despite often very high emission quantum yields the visible absorption of cyclometallated complexes of iridium(III) and platinum(II) is usually poor (e < 10,000 M-1cm-1), thus,... 

A special type of reaction is observed with the platinum(IV) complex [PtI(Me)3] which cleaves the Af,N,Af, A -tetraphenyltetraaminoethylene under reduction to form the dimeric cyclometallated mono(NHC) complex of platinum(II) iodide [Eq. (31)]. Cyclometallation with the same ligand is also observed for ruthe-nium. Additional cyclometallations with various substituents of NHCs have been reported for ruthenium(II), rhodium(III), iridium(I), palladium(II), " and platinum(II). In the case of iridium, alkyl groups can be activated twice. In rare cases like for nickel(II) /x-bridging NHCs have been obtained. ... 

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

As shown in Sec. 2.2.5.1, the majority of reported data on cyclometallation is related to metals of the platinum group, for example 606 [49]. In this respect, the cyclomer-curation, described by reactions (3.42) and (3.43) which results in mercury complexes 607 and 608 [50], represents a definite interest ... 

Because of the creative minds contributing to the field, the tools of C-H bond transformation available to synthetic chemists are actively expanding [1], Among these, coordination-directed C-H bond-activation has long preserved its appeal, because it enables selective functionalization of a particular C-H bond in the presence of other functional groups. This can be achieved by using a heteroatom (FG = functional group shown in Scheme 1) in the substrate structure to direct the metal complex to the proximity of the specific C-H bond. Even unactivated sp3-centered C-H bonds tend to react in a cyclometalation step with palladium, platinum [2], and ruthenium catalysts [3]. 

Keohan FL, Lewis LN (1985) Heat curable silicone polyimide rubber compositions containing cyclometallized platinum phosphite compounds. US Patent 4634610 A... 

Notably, it is not just heteroatom-functionalized alkenes that can behave as dienophiles with metal-bound phospholes. It has been demonstrated that reaction of 2equiv of 3,4-dimethyl-l-phenylphosphole with a cationic platinum(n) complex of an enantiomerically pure cyclometallated A, A -dimethyl-l-(l-naphthyl)ethylamine ligand affords, following decomplexation with cyanide, the novel optically pure diphosphine (-f)-267 quantitatively as an air-sensitive oil (Scheme 93) <2000CC167>. The high-frequency chemical shift of one of the phosphoms centers (5 4.9 and 104.2 ppm (7pp = 43.9 Hz)) is indicative of rwt>-jy -stereochemistry. Similar reactivity has been... 

Aldehyde C-H bonds can also undergo cyclometalation with palladium salts. Reaction of 8-quinolinecarbaldehyde with PdCLt gives a chloride-bridged dimer with a palladium-acyl bond (equation 75). No intermediates could be isolated in case of the palladium reaction, but when [(PEt3)PtCl2]2 is reacted with 8-quinolinecarbaldehyde, a platinum complex is isolated with an intact aldehyde C-H bond. The nitrogen atom of the quinoline is coordinated to the platinum, and the aldehyde C-H bond occupies an axial site in the complex. Heating this material results in insertion into the aldehyde C-H bond and formation of a chelated platinmn acyl. 

A dinuclear cyclometalated platinum(II) complex [Pt2L2 (dppm)] + (L = 4-(jo-diethylphosphonophenyl)-6-phenyl-2, 2 -bipyridine) has been employed as a luminescent probe for SDS micelles. Addition of SDS micelles to an aqueous solution of the complex led to an entission band at 530 mn, which was similar to the MLCT emission of mononuclear species. The observations were attributed to the absence of intramolecular and/or intermolecular Pt(II) Pt(II) interactions when the complex was incorporated in the SDS nticelles. Addition of NaCl solution into a micellar solution of the complex resulted in an additional MMLCT ((da )— (tt )) emission band at 650 nm. It was suggested that addition of sodium cations would force two cyclometalated platinum(II) units sufficiently close for intramolecular metal-metal and/or ligand-ligand interactions to occur, and thus the observation of MMLCT luminescence. 

---