abstracts - Институт катализа им. Г.К. Борескова

OP-II-1the η 2 -H 2 ligand does not necessarily need the intervention of molecular hydrogen to beformed as it may also be obtained from a terminal hydride by treatment with various protondonors, including many solvents of common use in organometallic synthesis andhomogeneous catalysis (e. g. alcohols) [2]. The formation of η 2 -H 2 complexes inhomogeneous processes is therefore a facile route and should always be considered in themechanistic elaboration of any reaction involving either H 2 and a metal complex or ametalhydride and a Brønsted acid.Thus, the proton-transfer processes to and from transition metal centers and hydrideligand sites have received a great deal of attention over the last two decades. It is now wellestablished that the proton transfer occurs via intermediates, for which characteristicspectroscopic signatures have been established, that contain hydrogen bonds between theproton donor and the proton acceptor (the metal center or a hydride ligand). [3] The term“non-classical hydrogen bonding” has been coined to address these interactions, while H-bonding specifically involving a hydride ligand has also been termed “dihydrogenbonding”.[4]Scheme 3.MH+ ++HXHHM H MMHHH XX -Dihydrogen Proton Ion pairbonding transfer dissociationX -MHH+L-H 2 M L+X -The relationship between the transition metal hydride structure and the mechanism of theproton transfer reaction, its thermodynamics and kinetics has been of interest to us in recentyears. The recent results obtained for the protonation of PP 3 MH n (PP 3 = P(CH 2 CH 2 PPh 2 ) 3 ; n =2 M = Fe, Ru, Os; [5] n = 1 M = Co) and Cp*MH n (dppe) (M = Fe, n = 1;[5] M = Mo, n = 3)will be discussed in this presentation. The combination of spectroscopic (IR, UV, NMR)studies at 190-290 K with DFT calculations disclosed the static and dynamic features of thesehydrogen bonds. The nature, properties and guiding role of hydrogen bonded complexes inthe proton transfer processes were elucidated. Proton transfer kinetics and thermodynamicswere studied. Peculiarities were found in the relationship between the strength of hydrogenbonds and ease of proton transfer to unconventional basic sites. These studies led to the180