Platinum, alkylplatinum complexes

Oxidation and H-D exchange reactions apparently begin with the attack by the reactive form of the platinum(II) complex on the hydrocarbon molecule, RH, which results in the formation of an alkylplatinum(II) a-complex ... 

On the other hand, H—Pt(ll) complexes are the only group VIll transition metal species for which the anti-Markownikoff insertion of 1-olefins does not clearly prevail 74-76) Thus, rrans[HPt (acetone) (PR3)2]" PF6 [PR3 = CH3P(C6H5)2] inserts pro-pene and butene-1 giving n-propyl- and n-butylplatinum(Il) complexes Attempts to prepare sec-alkylplatinum compounds by an independent route resulted in the formation of the platinum-hydiido bond It was concluded that sec-alkylplatinum complexes are generally unstable. A reason for this behavior of Pt(II), which evidently contrasts with Co(I), Ni(II), Rh(III), Ir(III), and Pd(II) (Table 6) is not known. 

Bipyridine and phenanthroline are employed as auxiliary ligands of the alkylplatinum(iv) complexes, for example, 921-923, and methyl(iodo)bis(thiolato)-platinum(iv) complexes are obtained as a mixture of the two geometrical isomers 924 and 925. The dimethyl(iodo)phenoxoplatinum(iv) complex 926 has also been prepared. Halogenation of the five-coordinated olefin-platinum(ii) complex with a phen ligand affords the Pt(iv) complex with three halides and a halogenoalkyl ligand. 

Alkylplatinum(IV) complexes exhibit considerable stability. When /ac-trimethyl-platinum(IV) species are heated, however, they eliminate ethane cleanly ... 

Following this oxidative addition, insertion of the olefin or alkyne occurs into the platinum-hydride bond to form an alkyl or vinyl hydride complex. The regioselectivity of the insertion step and the chemistry of the alkyl silyl complexes control the overall regioselectivity of the hydrosilylation of olefins. Recall that these platinum catalysts form terminal alkylsilane products. This regioselectivity indicates that insertions of terminal olefins occur in order to generate a linear alkylplatinum intermediate. Apparently, the insertions of styrene and acrylic acid derivatives into the platinum hydride in these catalysts occur with the same regiochemistry. 

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