Rare gas-halogen complexes

Alternatively, one may pump an excited electronic state of the diatomic moiety with subsequent dissociation within the excited state. Representative examples are the rare gas-halogen complexes like... 

The van der Waals attraction between Br and I2 is estimated to be 400 cm-1 by analogy with halogen/rare gas complexes (Bieler and Janda 1990 Bieler et al. 1991). This ensures that photodissociation of the HBr moiety cannot produce Br + I2 except via quenching of Br or the unlikely instance in which the hydrogen is trapped efficiently between the heavv particles. With the Br atom unable to escape from the I2 because of the Br-I2 van der Waals attraction, the system is ensured of an essentially unity quantum yield. 

Sb-H bonds, 489 Sb-halogen bonds, 489 Se-H bonds, 451 Se-halogen bonds, 451 Si-Br bonds, 465 Si-Cl bonds, 464 Si-F bonds, 464 Si-H bonds, 455 Si-1 bonds, 465 Sn-Br bonds, 475-476 Sn-Cl bonds, 475 Sn-F bonds, 475 Sn-H bonds, 473 Sn-1 bonds, 476 Te-H bonds, 453 Te-halogen bonds, 453 Rare gas complexes anions, 1452 cations, 1446-1452 neutrals, diatomic, 1429-1436 polyatomic, 1436-1446 Rb-contarnmg species neutrals, 557-559 Rb clusters, 559-562 Rb clusters, 562-563 Re-containing species neutrals,796-799 Re clusters, 799-801 Re clusters, 801 Rh-contarnmg species neutrals, 882-892 Rh clusters, 892-894 Ru-containing species neutrals, 840-848 Ru clusters, 849-851... 

THE RARE GAS(Rg)+HALOGEN(X2) REACTIONS WITHIN THE Rg-X2 VAN DER WAALS COMPLEX... 

For all systems the fluorescence of the first excited state Xe-X2(B3llu) has not been observed as it has been for lighter rare gas [10]. Here the excitation does not bring enough energy into the system to allow a chemical reactioa The absence of fluorescence arises from the electronic predissociation of the halogen induced by the presence of the heavy atom in the complex. 

The electronically excited rare gas atom is sometimes called a super-alkali because its ionization potential is so low. There are also super-halogens and not only super-alkalis (Herschbach, 1966 Bersohn, 1976). The super-halogen has a particularly high electronic affinity NO2, with an electron affinity of about 2.4 eV, is an example so is (CN)2. Excited states of organic molecules are used as effective electron donors. Complexes of transition metals in unusually high oxidation states are keen acceptors and vice versa for complexes where the metal is nominally neutral. 

My last comment concerns the reaction of palladium olefin complexes with carbon monoxide discovered by Tsuji. I agree that this is most likely to proceed by an insertion rather than an ionic mechanism. Chloride attack on coordinated olefin is rare however. Chloride ion is an inhibitor, for example in the palladous chloride catalyzed hydration of ethylene (0). I, therefore, wondered whether carbon monoxide was affecting the ease with which chloride attacks olefin. One can postulate that carbon monoxide participates in this insertion either as a gas phase reactant or by first forming a carbonyl olefin complex. Such complexes of the noble metals were unknown, but examining the reaction between carbon monoxide and the halogen bridged olefin complexes of platinum revealed that they are formed very readily... 

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