Platinum zero-valent complexes, addition

Secondary phosphines are more reactive toward zero-valent complexes. When zero-valent platinum Pt(tran5-stilbene)(dppe) reacts with PHMesa (Mes = mesityl), competitive oxidative addition of P-H and P-C bonds takes place via a three-coordinate Pt(dppe)PHMes2 common intermediate (Scheme 3.84) [168]. Since the P-H bond cleavage product is converted to the P-C bond cleavage product, the former is regarded as a kinetic product and the latter is a thermodynamic one. 

Further unequivocal examples for oxidative addition of organometallic M-C bond to a zero-valent complex were obtained by the reactions of Me-MoCp(CO)3 and AcCo(CO)4 with palladium(O) and platinum(O) complexes giving (dppe)RM-M L (M = Pt, Pd. M = Mo, Co) in high yields (Eq. 3.50) [177]. Such oxidative addition reaction is considered to be reversible, since the organic group in L2RM-M Cp(CO)3 transfers to M to give RM Cp(CO)3 by reductive elimination at M [178]. 

Hydrophosphination of ethyl acrylate using PH3 (R = C02Me, Equation (17)) is catalyzed by a mixture of the zero-valent platinum complexes (72a c), which are formed upon addition of P CH2CH2C02Et 3 to Pt(norbornene)3] (Scheme 44). Failure of these complexes to bring about P H addition to CH2 = CHCF3 indicates that Michael activation of the alkene through I and R effects of the substituents is crucial for catalytic activity in this class of metal complexes.190... 

Harrison, K.N., Hoye, P.A.T., Orpen, A.G., Pringle, P.G., and Smith, M.B., Water-soluble, zero-valent, platinum-, palladium,- and nickel-P(CH2OH)3 complexes catlaysts for the addition of phosphine to formaldehyde, J. Chem. Soc., Chem. Commun., 1096, 1989. 

Hydrides of Pt(II) are the most numerous of any transition metal hydride group. In addition to the presence of the hydride ligand, the complexes invariably have a coordinated phosphine, and synthetic routes to these compounds using both hydridic and protonic reagents have been reported (I). The pure complexes are usually both air stable and kinetically inert. The purpose of this chapter is to show the diversity of hydrides that can be obtained from protonation reactions on zero-valent and di-valent triphenylphosphine platinum compounds, and to rationalize the type and nature of the product formed from the character of the acid HX. 

Ethylene (tert-phosphine) complexes of zero-valent nickeP and platinum have been known for years. Analogous palladium complexes can be synthesized along the same lines as those reported for the nickel compounds, using ethoxy-diethylaluminum(III) as the reducing agent in the presence of ethylene. These palladium-ethylene complexes may serve as starting materials for oxidative addition reactions, since the ethylene ligand is loosely bonded. ... 

Manners first proposed that the transition-metal-catalyzed ROP occurred via a homogenous mechanism.157 However, a heterogenous catalytic cycle has been reported.158 The proposed mechanism for the Pt(l,5-cod)2 (cod-cyclooctadiene) catalyzed reaction is shown in Scheme 2.24. The Pt(l,5-cod)2 forms a [2]platinasilaferrocenophane through oxidative addition to the zero-valent Pt complex via elimination of a 1,5-cod ligand. Platinum colloids are then formed by the elimination of the second 1,5-cod ligand these platinum colloids are proposed to be the active catalysts. The polymers are then formed by subsequent oxidative addition and reductive eliminations at the colloid surface. 

The prior r -coordination is also proposed for oxidative addition of phenyl-propargyl halides to zero-valent platinum complex Pt(PPh3)4, where Pt(PPh3)2 and Pt(PPh3)3 are active species for the oxidative addition. Kinetic study reveals slow formation of Pt(r/ -PhC=CCH2X)(PPh3) n = 2, 3), from which... 

As a rare example, oxidative addition via ionic mechanism to give the cis product is also known [16,17,24]. Oxidative addition of propargyl halides to a zero-valent platinum complex results in cA-(halogeno)(j7 -propargyl)platinum(ll) complex as a kinetic product (Scheme 3.10). 

Oxidative addition of vinylic C-S bond to zero-valent platinum complex has recently been investigated in detail [139], The reaction of Pt(C2H4)(PPh3)2 with... 

P-Se bond oxidatively adds to zero-valent palladium and platinum complexes [170], Treatment of M(PEt3)3 (M = Pd, Pt) with PhSeP(0)(0R)2 results in oxidative addition to give tran5-M(SePh)[P(0)(0R)2](PEt3)2 (Eq. 3.45). Catalytic addition of selenophosphates PhSeP(0)(0Ph)2 to terminal alkynes RC CH giving R(SePh)C=CHP(0)(0Ph)2 is also performed by Pd(PPh3)4 via similar mechanism shown in Scheme 3.85. 

Oxidative addition of other group 14 atom-tellurium bonds (Si-Te, Ge-Te, and Sn-Te) is also achieved (Eq. 3.47) [172]. Reactions of zero-valent platinum complex R(PEt3)3 with RTeMMcs (M = Se, Ge, Sn) at 25°C result in the formation of the tra 5 -Pt(TeR)(MMe2)(PEt3)2 within 10 min. 

Oxidative addition of transition metal-hydride and transition metal-carhon bonds to zero-valent transition metal complexes provides convenient method for preparation of homo- and heterodinuclear organometallic complexes. Oxidative addition of iron-hydride to zero-valent platinum complex giving Fe-Pt heterodinuclear complexes was demonstrated hy the reaction of HFe[Si(OMe)3](CO)3(/c -dppe) with zero-valent platinum complex such as Pt(C2H4)3 or Pt( 1,5-cod)2 giving eventually heterodinuclear ethyl or cyclooctenyl complex (Scheme 3.86) [175]. The resulting heterodinuclear structure is stahihzed hy the bridging dppe ligand and the siloxo moiety. 

Another route to p.-Carbido complexes which we have found is oxidative addition of Lalor s halocarbyne complexes [21] to zero valent triphenylphosphine compounds of nickel, palladium and platinum. In these reactions the heterodimetalla cyclopropenes could be isolated which isomerize at higher temperatures to the dimetalla allene complexes. The first adducts of arylcarbyne complexes to zerovalent platinum complexes (arylcarbyne as analogue of ace-... 

The latter carbonylation involves the formation of PtH(SR)(PPh3)2 by the oxidative addition of RSH to the zero-valent platinum complex. A possible pathway may include the CO insertion into the S-Pt bond of PtH(SR)(PPh3)2. Then, acylplatination of alkynes generates p-thiocarbonyl-substituted vinylplatinum intermediate, which undergoes reductive elimination to give the a,p-unsaturated thioesters with regeneration of the catalyst. 

Harrison KN, Hoye PAT, Orpen AG, Pringle PG, Smith MB (1989) Water soluble, zero-valent, platinum- palladium-, and nickel-P(CH20H)3 complexes eatalysts Pot the addition of PH3 to CH2O. J Chem Soc Chem Commun 1096-1097... 

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