Platinum complexes pyrazolates

Organonickel derivatives also offer cases of the -coordination of the substituted hydrotrisfpyrazol- l-yl)borate ligand. For the palladium and platinum complexes, the M(II) M(IV) (M = Pd, Pt) transformation is facile. Organopalla-dium chemistry offers anew type of agostic interactions, C—H - - - Pd, where the C—H bond belongs to one of the pyrazolate rings. Cyclopalladation of various pyrazol-l-ylborates and -methanes does not modify their structure. 

The two platinum complexes 478 and 479 are less fluxional, the pzTp complex 478 being stereochemically rigid below 110 °C, above which it becomes unstable in solution, while for the Tp analogue 479 equivalence of the pyrazole groups is achieved at 85 °C. This equilibration slows at ambient temperature, but poor solubility below 10 °C precluded acquisition of limiting spectra. 

Several trifluoromethylpyrazoles, for instance 3(5)-trifluoromethyl-5(3)-methylpyrazole (44) were used to prepare platinum complexes and the x-ray structure of the resulting complex reported <83 C774>. The ligand tris[3-trifluoromethyl-5-methyl(pyrazol-l-yl)]borate (82) yields a hydridovinyl iridium complex more stable than its j/ -ethylene isomer <89JA5480>. The x-ray structure of the related platinum complex (83) has been described <831C774>. 

NjCjH, lH-Pyrazole, 3,5-dimethyl-, boron-copper complex, 21 109 N2C8H20, 1,2-Ethanediamine, A,/V -bis(l-meth-ylethyl)-, platinum complex, 21 87 N2C10HS, 2,2 -Bipyridine, ruthenium complex, 21 127... 

In addition to a boron atom fusing pyrazole ligands, platinum complexes have been prepared from ligands having pyrazole groups coupled by phosphazenes ° and a methane carbon. 

A recent example [31] from Falvello et al. on bimetallic, pyrazolate-bridged complexes of platinum(II) and palladium(II) is instructive (Scheme 8). These two compounds exhibit differentiated behavior in the presence of silver(I) perchlorate the platinum complex binds silver through two donor-acceptor metal-metal bonds supplemented by silver-tolyl n interactiOTis, while the palladium complex binds silver through the 71-electron density of the pyrazolate ligands. 

The following compounds have been obtained from thiete 1,1-dioxide Substituted cycloheptatrienes, benzyl o-toluenethiosulfinate, pyrazoles, - naphthothiete 1,1-dioxides, and 3-subst1tuted thietane 1,1-dioxides.It is a dienophile in Diels-Alder reactions and undergoes cycloadditions with enamines, dienamines, and ynamines. Thiete 1,1-dioxide is a source of the novel intermediate, vinylsulfene (CH2=CHCH=SQ2). which undergoes cyclo-additions to strained olefinic double bonds, reacts with phenol to give allyl sulfonate derivatives or cyclizes unimolecularly to give an unsaturated sultene. - Platinum and iron complexes of thiete 1,1-dioxide have been reported. 

The reactivity of the closely related system TpMe2PtMeH2 toward electrophiles in arene solvents has also been reported recently (68). The boron-based Lewis acid B(C6F5)3 induced elimination of methane and formation of an aryl(dihydrido) platinum(IV) complex via arene C-H activation (Scheme 17, A -> C). The active acid may be either B(C6F5)3 or alternatively a proton generated from B(C6F5)3 and trace water. It was proposed that the acid coordinates to a pyrazole nitrogen (shown in Scheme 17, B) forming an intermediate five-coordinate platinum(IV) complex, which readily eliminates methane. 

Protonation reactions of the related dimethyl(hydrido)platinum(IV) complex TpMe2PtMe2H (58) leading to rapid methane reductive elimination have also been reported (86). This protonation was shown to occur exclusively at the pyrazole nitrogen, presumably forming a five-coordinate Pt(IV) intermediate. This species should undergo C-H coupling, and while a Pt(II) methane complex is not observed, trapping with... 

Bis(phosphoranimine) ligands, chromium complexes, 5, 359 Bis(pinacolato)diboranes activated alkene additions, 10, 731—732 for alkyl group functionalization, 10, 110 alkyne additions, 10, 728 allene additions, 10, 730 carbenoid additions, 10, 733 diazoalkane additions, 10, 733 imine additions, 10, 733 methylenecyclopropane additions, 10, 733 Bisporphyrins, in organometallic synthesis, 1, 71 Bis(pyrazol-l-yl)borane acetyl complexes, with iron, 6, 88 Bis(pyrazolyl)borates, in platinum(II) complexes, 8, 503 Bispyrazolyl-methane rhodium complex, preparation, 7, 185 Bis(pyrazolyl)methanes, in platinum(II) complexes, 8, 503 Bis(3-pyrazolyl)nickel complexes, preparation, 8, 80-81 Bis(2-pyridyl)amines... 

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