Platinum complexes configuration

The mechanistic study on the hydrophosphination of activated olefins, in conjunction with rapid inversion of the configuration at the phosphorus center, was elaborated to develop asymmetric hydrophosphination catalyzed by a chiral phosphine platinum complex although the % ee is not excitingly high yet (Scheme 9) [15]. 

Fig. 15. The stereoisomeric thiourea-platinum complexes shown in (a) display large 4/ptjC couplings for the a-carbon atom in that branch of the X.X-dialkyl substituent which is in a favourable W configuration with respect to the metal atom (thick bonds). The assignment of the (fortuitously overlapping) H and 195Pt NMR signals of all three stereoisomers was feasible by means of indirect detection of these couplings from a XH detected H/(13C)/195Pt correlation spectrum which is shown in (b) together with the one-dimensional and 195Pt NMR projections. Reproduced from Ref. 44 by permission of John Wiley Sons.

As part of a search for other ligands capable of adopting a square-planar configuration about a metal atom and thus potentially able to form stacked units our attention was drawn to the ligand H2P2052- (diphosphonate), usually abbreviated pop. Platinum complexes of this ligand - in particular [Pt2 (pop) i,] l - have already been subject to interesting studies of their luminescence, electronic, Raman and infrared spectra (12-161. Our initial objectives were to try to incorporate [Pt v(en)2X2]2+ (en =... 

Fig. 2. Molecular structures of anticancer active (cis-configurations) and nonactive (transconfigurations) platinum complexes, a) d.v-I)ichlorodiammineplatinum(II) b) frans-dichlo-rodiammineplatinum(II) c) cw-tetrachlorodiammineplatinum(IV) d) frans-tetrachlorodiam-...

Platinum and palladium complexes of thietane and 3,3-dimethylthietane have been prepared as illustrated for 90. The platinum complexes exist in cis and trans configurations, but no cis-trans isomerization of the palladium complexes in the solid state was observed. Stability constants of thietane with Mn(ll), Co(II), and Ni(II) chelates have been determined. Proton nmr studies show that the absorption of the a-methylene protons, which are syn to the metal, is shifted downfield (about 0.7 ppm) more than the absorption of the protons anti to the metal (about 0.4 ppm downfield). Energies of activation for pyramidal inversion were determined. Bis-ruthenium complexes of di-, tri- and tetraspirothietanes (e.g., 90a) show rapid electron transfer between the ruthenium ions long-range electron tunneling was proposed. ... 

In this new class of platinum complexes some examples do not present the necessary cis configuration with respect to the chlorines. Oxaliplatin has been approved for clinical use in France and China for colorectal cancer. The interest in developing platinum complexes that bind to DNA in a fundamentally different manner to cisplatin is an attempt to overcome the resistance pathways that have evolved to eliminate the drug. 

GpG, d-GpG and d-pGpG Platinum Complexes. Only one complex is obtained for each dinucleotide. The comparative NMR data are collected in Table I. The anti - anti configuration has been previously assigned to these three complexes (23) on the basis of the following results - a - The comparison of the 3 - and 5 -H8 deuterium exchange rates in D2O (pD 10) with those of the... 

Oxalipladn was developed in an attempt to circumvent the problem of cispladn resistance noted in padents treated with cisplatin who subsequendy relapse and are retreated with cisplatin. This drug and the resistance to cisplatin are described in Chapter 15. Transplatin was included to demonstrate one of the primary structural requirements of the platinum complexes, that being that the stable ammines must be in the cis configuration. Ammines in the trans configuration, as in the case of transplatin, result in pladnum complexes that lack antitumor activity. 

Extensive mechanistic studies have been performed on reactions catalyzed by rhodium and platinum complexes containing enantiopure C2-symmetric diphosphine ligands.As discussed above, (1) the formation of the Tr-olefin-Rh(H) complex 19, (2) stereospecific cis addition of the hydridorhodium to the coordinated olefin to form the alkyl-Rh complex 20 (and then 2, and (3) the migratory insertion of a carbonyl ligand giving the acyl-Rh complex 17 with retention of configuration, have been established in the hydroformylation of 1-alkenes or substituted ethenes. Thus, it is reasonable to assume that the enantioselectivity of the reaction giving a branched aldehyde is determined at the diastereomeric (1) TT-olefin-Rh complex 19 formation step, (2) alkyl-Rh complex 20 formation step, or (3) acyl-Rh complex 17 formation step. 

Nickel is an analogue of platinum and its oxidation state at which methane is produced is Ni(II) with a d electronic configuration, that is the same as that of Pt(II) which activates methane and other alkanes (see Chapter VII). Evidently the activation of methane on platinum complexes may be considered a conditional model for biological anaerobic oxidation of alkanes. It is of importance that Ni(II) as well as Pt(II) is a so-called soft acid and could prefer to react with methane ( soft base) rather than with such strong hard base as water, therefore surrounding water does not prevent this reaction. 

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