Methylplatinum complexes

Attempts have been made to mimic proposed steps in catalysis at a platinum metal surface using well-characterized binuclear platinum complexes. A series of such complexes, stabilized by bridging bis(diphenyl-phosphino)methane ligands, has been prepared and structurally characterized. Included are diplati-num(I) complexes with Pt-Pt bonds, complexes with bridging hydride, carbonyl or methylene groups, and binuclear methylplatinum complexes. Reactions of these complexes have been studied and new binuclear oxidative addition and reductive elimination reactions, and a new catalyst for the water gas shift reaction have been discovered. 

Shilov found that a methylplatinum complex, [MePt03(Pni3)2], was formed from methane and H2PtG6 at 120 C, followed by reaction with PPhs. 

An anionic pentamethylplatinate(IV) complex, LilPtMesCPPhs)], and homolep-tic hexamethylplatinate(IV), Li2[PtMe6], were prepared analogously by stepwise methylation of the neutral methylplatinum complexes [35,36], Eq. 5.10 shows the preparation of the hexamethylrhodate(III) complex, Li3[RhMe6] [37],... 

It is more facile than the reaction of NiBr(Ar)(bpy), whose disproportionation via intermolecular aryl ligand transfer requires polar solvents to assist Ni-halogeno bond activation as mentioned in a previous section. Methylplatinum complexes with monodentate phosphine, arsine and thioether hgands cause methyl ligand transfer leading to disproportionation and cis-trans isomerization [207] (Eq. 5.63). 

For palladium systems the dissociative pathway is often preferred. Cationic four-coordinate methyl(carbonyl)palladium complexes, [PdCH3(CO)L2]+, have been observed by spectroscopic means [64,71] and sometimes isolated [65d,72] as key intermediates in the formation of the acyl complexes. The dissociative pathway has also been confirmed in the reaction of CO with neutral methylplatinum complexes having a bidentate P-N ligand from which CO-coordinated intermediates were formed with dissociation of N atom of the ligand (Scheme 7.10) [64,73], The P-N ligand forms a chelate again after the reaction at ambient temperature to give the isolable acetylplatinum product. 

A methylplatinum complex with a siloxo ligand has been prepared by the metathesis reaction of a chloro(methyl)-platinum complexes with Na[SiOPh3]/ A dinuclear Pt complex with bis(trimethylsilyl)methyl ligands and bridging chloro ligands 52 reacts with /-butyl isocyanide and then with NaCp to produce the platina(amino)fulvene 53 via addition of Cp to the coordinated isonitrile and migration of the hydrogen atom (Equation (15))/ ... 

TMEDA forms cationic methylplatinum complexes with OEt2 or THF as ligands. Intramolecular activation of a C-H bond of the OEt2 ligand, accompanied by elimination of methane to produce the cationic complex with a Fischer-type carbene ligand 103, occurs via an intermediate with hydride and vinyl ethyl ether as the ligands (Equation (23)). ... 

Bis(2-pyridyl)amine forms square-planar cationic methylplatinum complexes with a DMSO ligand.A DFT study has been reported for the oxidative addition reaction of methyl imidazolium to Pt(PH3)2 to give a cationic complex, [PtMe(CNMeCH=CHNMe)(PH3)2], and the geometry of the product optimized. ... 

The cationic methylplatinum complex with a 1,3-diaza-l,4-butadiene ligand having 2,6-dichlorophenyl groups 127 promotes G-H bond activation of benzene to afford the cationic phenylplatinum complex 128 (Equation (30))2 ... 

The cationic methylplatinum complex with terpy as a ligand 138 is prepared from the neutral chloro(methyl)platinum(ii) complex of the ligand in the presence of NaBPh4 (Equation (31)). The crystal structure showed that the coordination planes of the two crystallographically independent molecules are parallel with head-to-tail packing. 

A cationic methylplatinum complex having the two pyridinoaminophosphine ligands in P- and T,jY-coordination 139 is obtained from PtClMe(cod) (Scheme 23). It reacts with KOBu to cause substitution of the monodentate ligand and NH hydrogen abstraction of the other ligand to form the neutral complex. 

Triphos, (Ph2PCH2CH2)2P, also forms the cationic methylplatinum complex with the tridentate ligand, [PtMe2(triphos)]OTf. Optically active P,N- and P,iV, -chelating ligands have been employed in the preparation of cationic methylplatinum complexes with these ligands/ " ... 

A neutral complex with the Ph3PG=G=0 ligand 191 undergoes addition of secondary amine and alcohols to give 192 (Equation (51)), similar to the cationic methylplatinum complex (Scheme 25). A bis(ketenyl)platinum(ii) complex is also formed. ... 

Bis(A7-azaindolyl)methane-coordinated complexes have been prepared and fully characterized, and addition of [H(OEt2)2] to the dimethylplatinum(ii) complex 200 forms the cationic methylplatinum complex with the ligand, whereas the reaction in benzene forms the cationic phcnylplatinum complex 201 via C-H bond activation of the solvent by the cation (Equation (52)). 

Analogous complexes with chloro and fluoro substituents on the aromatic group have been prepared 623-628." A methylplatinum complex with the CNN ligand formed from furan carboxyaldehyde has been prepared 629, while the imine of 3-pyridine carboxyaldehyde coordinates as an iV,A -bidentate chelate and does not undergo cyclometallation 630. ... 

Relief of ring strain facilitates P-carbon elimination both thermodynamically and kinetically, as is the case with oxidative addition. Thus, a cyclobutyl-methylplatinum complex underwent P-carbon elimination, even at —40"C, to furnish a ring-opened product (Scheme 1.36) [44]. 

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