H-'H coupling pattern may not be resolved, precluding the use of this method for assigning sugar pucker. Clearly, the 'H and 13C methods are complementary and both can be very useful. Finally, l3C signals are useful in defining metal-binding sites. The same advantages of this method for mononucleotide studies are passed on to oligonucleotide studies.25 Signals for carbons remote from the metal binding site appear to be most useful. discussions with Prof. David Live.

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064ChemInform Abstract Discussion of the data of nearly one hundred carbonyl and dinitrogen complexes with application to understand the bonding and reactivity of related hydrogen complexes.

Can. J. Chem. 72,547 (1994). The synthesis and properties of dihydrogen complexes trans-[MH(H2)L]+, M = Fe, Ru, Os, which contain the ligand mesotetraphos-1, S,R-Ph2PCH2CH2P(Ph)CH2CH2P(Ph)CH2CH2PPh2 (L) are described. There are interesting possibilities of isomerism in such trans complexes because the axial binding sites at the metal are different, one being surrounded by four phenyl groups and the other by two phenyl groups. The osmium complex is prepared in an unusual reaction of ci.~-p-Os(Cl)~L with HI, (1 atm) and NaBPh4 (1 mol) in THF or by the reaction of trans-OsH(C1)L with NaBPh4 and H2. The iron and ruthenium complexes were made by a reaction of HBF4 with complexes t r a n~-M ( H )~L that have inequivalent trans hydrides. The ruthenium complex was also prepared starting from isomers of t r a n s -R U H ( C~) L .~T~~ H-H distance in the rapidly spinning dihydrogen ligand has been calculated from Tl(min) data to be 0. [Traduit par la rtdaction]

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