Cyclooctadiene complexes with platinum

Platinum complexes incorporating an optically active amine have been employed for resolution of racemic mixtures of optically active olefins by reaction of the olefin with dichloro-platinum(II). The differing solubility of the diastereoisomers permits separation by fractional crystallization and the olefin can be recovered by reaction of the complex with aqueous alkali cyanide. Using either (-f)-l-phenyl-2-aminopropane (Dexedrine) or (-f)- or (—)-a-phenyl-ethylamine. Cope and co-workers have resolved the optical isomers of trans double bond coordinated and, with (—)-phenylethyl-amine)dichloroplatinum(II), a bridged complex with each double bond coordinated to a different platinum atom. 

Of the new Pt catalysts reported since 1990 platinum complexes with new ligands and activators are noteworthy. Cyclodextrin complexes of platinum (as host-guest complexes) have been employed as hydrosilylation catalysts active at elevated temperature after releasing the guest compound [40]. Some other organic compounds have recently been used as activators (ligands) of Pt complexes, e. g., unsaturated secondary and tertiary alcohols and silylated unsaturated alcohols [41], alkadiynes, cyclooctadiene [42], and vinylnorbomene as well as quinones and methylnaphthoquinones [43]. 

In all these reactions of chloroiridium complexes no insertion into the Ir — Cl bond was observed. For chloroplatinum(ii) complexes, however, such insertions have been observed. McCrindle and McAlees (1993) investigated the reaction of the dichloro(l,5-cyclooctadiene)platinum complex with three monosubstituted diazo-... 

Dinuclear Pt-Rh (336a-c, 339) and Pt-Ir (337a-c, 338) complexes with doubly alkynyl bridging systems have been isolated from the reactions between platinum alkynyl complex, 40 and from cyclooctadiene complexes of rhodium and iridium (Scheme 91). ... 

A novel chiral dissymmetric chelating Hgand, the non-stabiUzed phosphonium ylide of (R)-BINAP 44, allowed in presence of [Rh(cod)Cl]2 the synthesis of a new type of eight-membered metallacycle, the stable rhodium(I) complex 45, interesting for its potential catalytic properties (Scheme 19) [81]. In contrast to the reactions of stabihzed ylides with cyclooctadienyl palladium or platinum complexes (see Scheme 20), the cyclooctadiene is not attacked by the carbanionic center. Notice that the reactions of ester-stabilized phosphonium ylides of BINAP with rhodium(I) (and also with palladium(II)) complexes lead to the formation of the corresponding chelated compounds but this time with an equilibrium be-... 

Cyclooctenyl and norbomenyl platinum complexes analogous to 14 and 15 have been proposed in the reactions of 1,5-cyclooctadiene and norborna-diene with HPt(N03)(PEt3)2 (57). 

The complexes (l,5-cyclooctadiene)(2,4-pentanedionato)-palladium(II) and platinum(II) tetrafluoroborate are air-stable solids, soluble in polar organic solvents such as chloroform, methylene chloride, acetonitrile, acetone, or methanol but insoluble in nonpolar solvents such as alkanes, benzene, or ether. Their solutions in acetone have conductivities typical of 1 1 electrolytes. Their proton magnetic resonance spectra (in CDC13 solutions, internal tetramethylsilane reference at 60 MHz.) show peaks due to coordinated cyclooctadiene at 3.78 and 6.7-7.4r (Pd) and at 4.25 and 6.9-7.6r (Pt) and due to the chelated /3-diketone at 4.39 and 7.88r (Pd) and at 4.15 and 7.81r (Pt) with the expected area ratios. In the spectrum of the platinum compound coupling with the 95Pt isotope (33 %... 

The reaction of (93b) with Pt(COD)Cl2 gave (96) and when the reaction was carried out in the presence of silver tetrafluoroborate, the crystalline salt (97) was formed. An X-ray crystallographic structure determination of (97) showed a distorted tbp around phosphorus with the platinum fragment in an equatorial position and a near square-planar coordination geometry around the Pt atom. On heating to 60°C, (97) lost cyclooctadiene to form (98). Variable temperature P NMR studies were reported for (96) and (97). This work, using ligands (92) and (93a), was extended to complexes of Pt and Rh with similar results. ... 

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