Platinum complexes cleavage

In platinum chemistry, cleavage of bis(silyl) compounds by HCl may be used [Eqs. (58), (59)] to generate monosilyl complexes 63). 

The first cleavage reported is the displacement of platinum in silicon-platinum complexes by LiAlH and is believed to proceed by nucleophilic attack at silicon ... 

As mechanistic hypothesis it was proposed (9-11) that the excited platinum complex undergoes homolytic Pt Cl cleavage affording a Ptm intermediate and an adsorbed chlorine atom (Scheme 1), by analogy with the known photochemistry of hexachloroplatinate in homogeneous solution (23,31). Electron injection from the platinum(III) complex into the titania conduction band reforms PtIv. Thus, the... 

A benzylic platinum complex treated with excess HCl results in the loss of MeCl, presumably via an unusual methylene transfer (Scheme 67). Ring opening by relief of strain is a useful route for C bond cleavage. The reaction of biphenylene with a series of Pt bisphosphine... 

Unequivocal evidence for the ring-opening cleavage was provided by the reaction of the isolated neutral (cyclobutylmethyl)platinum complex 71 [85]. On thermal generation of a vacant coordination site, 71 undergoes (3-carbon elimination to afford 2-methyl-l,4-pentadiene together with a hydride complex. 

The interaction of the complex tetracarbonyldi-fj-chlorodirhodium with cyclopropane and substituted cyclopropanes produced complexes 3 and 4a, ° respectively, with the same dimeric structure. Contrary to the reaction with the platinum complex a five-membered ring 3 or 4120 jjj which both the metal and the carbon of one of the carbonyl groups were incorporated was formed. The cleavage site was the least substituted C —C bond. Analogous products 4c and 4b (75%) were obtained with bicyclo[4.1.0]heptane and phenylcyclopropane, respective-... 

The Pt2(pop)4 complex offers a unique opportunity for studying hydrogen transfer reactivity of nucleotides and DNA. The DNA cleavage reactions are unique in that the tetraanionic platinum complex is repelled from DNA, so if hydrogen abstraction does occur, it must proceed via an unfavorable binding equilibrium ... 

Deuterium labeling has been used to detect a cyclobutylmethylplatinum formation and ring cleavage by -alkyl elimination that occurs in a reversible way for the platinum complex in Scheme 6.51 [150]. A similar degenerate rearrangement occurs for the pentenyl derivative [Y(Cp )2() -) -CH2(CH2)2CH=CH2 ] [151]. 

The oxidative addition of disilanes occurs to palladium complexes of isonitrile ligands and platinum complexes of trialkylphosphine ligands as part of tiie catalytic silylation of alkynes and aryl halides. The addition of stannylboranes to Pd(0) complexes has also been reported,and the addition of diboron compounds to many metal systems, such as Pt(0) complexes (Equation 6.67), is now common. These reactions all occur with metal complexes that do not undergo intermolecular reactions with alkane C-H bonds, let alone C-C bonds. Thus, the Lewis acidic character of these reagents must accelerate the coordination of substrate and cleavage of the E-E bonds. 

Shilov reported some of the earliest evidence that transition metal complexes could selectively cleave the C-H bonds of alkanes in a catalytic fashion. Shilov showed that H/D exchange would occur between alkanes and deuterated acid in the presence of platinum complexes (Equation 18.5 and Table 18.1). In addition, Shilov showed that the oxidation of alkanes occurred in the presence of a platinum(II) catalyst, although a platinum(IV) complex was needed as the oxidant. These reactions led to a mixture of alkyl halides formed from the halide of the Pt(IV) oxidant (Equation 18.6) and trifluoroacetate from the trifluoroacetic acid solvent. The cost of platinum(IV) as an oxidant makes this reaction impractical. However, these results provided hope that selective alkane functionalization could be developed because H/D exchange occurred faster at primary C-H bonds than at secondary C-H bonds (Table 18.1), and some selectivity for oxidations of primary C-H bonds over secondary C-H bonds was observed. As noted in Chapter 6, these results motivated a large number of groups to seek transition metal complexes that would insert into, or by other means selectively cleave, the C-H bond of alkanes and create products from this bond cleavage that could be observed directly. 

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