Platinum -, trans

Case, F. N. and Acree, E. H. Purification of Curie Quantities of Fission-Produced 1-131 by Sorption on Platinum. Trans. Am. Nucl. Soc. 

Freunscht P, Van Duyne R P and Schneider S 1997 Surface-enhanced Raman spectroscopy of trans-stilbene adsorbed on platinum- or self-assembled monolayer-modified silver film over nanosphere surfaces Chem. Phys. Lett. 281 372-8... 

Johnson and Whitehead have further shown that the reductive elimination of the pyrrolidine group from the pyrrolidine enamine of 2,4-dimethyl-cyclohexanone (16), which involved treating it with a mixture of lithium aluminum hydride and aluminum chloride (9), gave the trans isomer of 3,5-dimethyl-/l -cyclohexene (17) which on subsequent hydrogenation on a platinum catalyst led to the // onr-3,5-dimethylcyclohexane (18). 

Compound [PtCl( Bu2PCMe2CH2)2l reacts with pyrazole or 3,5-dimethyl-pyrazole in the presence of sodium hydroxide to form 242 (R = H, Me) [84ICA (82)L9]. The chelate ring is not planar in this case, and the trans strucmre of the pyrazolate derivative was demonstrated. Tlie four-coordinated platinum atoms are characterized by a distorted square-planar coordination. 

The cyclometallated palladium and platinum derivatives of trimesityl phosphine or arsine react with pyrazole or 3,5-dimethylpyrazole to form metal chelates 243 (E = P, As M = Pd, Pt R = H, Me) having the trans configuration (81TMC24). 

Tetrahydro derivatives are formed when either quinoxaline or 6-chloroquinoxaline is reduced with lithium aluminum hydride in ethereal solution. Similar reduction of 2,3-dimethylquinoxaline gives the meso-(cts)-1,2,3,4-tetrahydro derivative. This is shown to be a stereospecific reduction since lithium aluminum hydride does not isomerize the dl-(trans)-compound. Low temperature, platinum catalyzed, hydrogenation of 2,3-dimethylquinoxaline in benzene also gives meso (cis) -l,2,3,4-tetrahydro-2,3-dimethylquinoxaline. ... 

Butylcyclohexanol has been prepared from />-/-butylphenol by reduction under a variety of conditions.3 4 Winstein and Holness5 prepared the pure trans alcohol from the commercial alcohol by repeated crystallization of the acid phthalate followed by saponification of the pure trans ester. Eliel and Ro 6 obtained 4-f-butylcyclohexanol containing 91% of the trans isomer by lithium aluminum hydride reduction of the ketone. Iliickel and Kurz 7 reduced />-/-butylphenol with platinum oxide in acetic acid and then separated the isomers by column chromatography. 

There are many more examples of cis- and trans-isomers for platinum (a consequence of (2)). 

X = H, F). The platinum analogue behaves similarly, and it also reacts with H2 to form trans-Pt(Pcy3)2H2. 

It has recently been shown that 1H NMR spectra can distinguish between cis- and trans-isomers of this type. The 3J(Pt-H) coupling constants between platinum and the a-hydrogen of the pyridines are slightly higher for the cw-isomers therefore for ct s-Ptpy2Cl2 3/(Pt-H) is 42 Hz while 3/(Pt-H) is 34 Hz for the trans-isomer [83]. 

Tertiary phosphine complexes of platinum and palladium M(PR3)2X2 are important [95]. The cis- and trans- somers are readily obtained for platinum,... 

The structures of the series trans-Pt(PMePh2)2 RC1 (R = Me, CF2CF3) show Pt-C bonds of 2.081 and 2.013 A, respectively, with the electron-withdrawing fluoroalkyl leading to a shorter and stronger bond. (Data for some other platinum alkyls are discussed in section 3.8.10.)... 

Platinum (II) carbenes should be mentioned as <7-bonded organometallics. An important general synthesis by cleavage of an electron-rich alkene affords a pair of isomers, the trans-form isomerizing to the thermodynamically more stable cw-form on heating (Figure 3.61). 

For complexes like PtL2X2 (X = halogen L = NH3, PR3, etc.) where cis-and trans-isomers exist, the trans-isomer is usually thermodynamically more stable. The c/s-isomer may be formed first in a reaction and, in the case of platinum, may be relatively inert to substitution. (Thermodynamic data are relatively scarce trans-Pt(NH3)2Cl2 is some 13kJmol-1 more stable than the cis-isomer.)... 

In the 1920s, the Russian chemist Il ya Il ich Chemyaev systematized reactions of complexes of several metals, particularly platinum(II and IV), by noting that a ligand bound to a metal ion influenced the ease of replacement of the group trans to it in the complex [139]. 

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

A seminal paper [155] examined platinum-phosphorus NMR coupling constants in a series of cis- and trans-platinum(II and IV) complexes. The trans-influence had hitherto been explained in terms of d7r-p7r bonding, in other words, such a mechanism dominated with trans-effect... 

The most important of the tertiary phosphine complexes of platinum(IV) are Pt(QR3)2X4, generally prepared by halogen oxidation [174] of cis- or trans-Pt(QR3)2X2 (Q = P, As, R = alkyl Q = Sb, R = Me), since direct reaction of the platinum(IV) halides with the ligands leads to reduction. Once made, the platinum(IV) compounds are stable to reduction ... 

Figure 3.102 Far-IR spectra of (a) traris-Pt(PEt3 )2C14 (b) rram-Pt(PEt3)2Br4 (c) trans-Pt(PEt3)2l4 (d) cis-Pt(PEt3)2Cl4 (e) cis-Pt(PEt3)2Br4. Platinum-halogen vibrations are shaded.

Halogen oxidation of platinum(II) complexes generally occurs trans, as does reaction with H202 to afford dihydroxy complexes (Figure 3.106). 

The use of this phosphine facilitates assignment of configuration as virtual coupling is observed when the phosphines are trans (section 2.9.5).) Syntheses follow established routes using methyllithium as an alkylating agent the platinum(iV) complexes can be made by direct alkylation of platinum(IV) compounds or by oxidative addition to platinum(II) species. 

Figure 3.116 Platinum compounds studied for possible anti-tumour activity. I, ris-Dichlorodi-ammineplatinum(II) cisplatin, platinol NSC 119875 neoplatin platinex. II, a.s-Diammine(l,l-cyclobutanedicarboxylato)platinum(II) JM-8 paraplatin NSC 241240. Ill, Oxiplatin. IV, Tetraplatin. V, Amminediacetatodichloro(cyclohexylamine)platinum(IV). VI, cis-Dich oro-trans-dihydroxy-cis-bis(isopropylamine)platinum(IV) iproplatin JM-19 CHIP NSC 256927.

Platinum, dichlorobis(dimethyl sulfide)-isomerization, 1, 318 trans-... 

DNA polymerases, 5, 1007 Trans effect, 1,16, 26, 315 metal complexes, 2, 705, palladium(II) amine complexes, 5, 1115 platinum complexes, 5, 353, 493 six-coordinate compounds. 1, 49 T ransestcrification metal alkoxide synthesis, 2, 340 Transferases zinc, S, 1002... 

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