Hydrogenation and Silylation of a Double-Cyclometalated Ruthenium Complex: Structures and Dynamic Behavior of Hydrido and Hydridosilicate Ruthenium Complexes

A double-cyclometalated
ruthenium complex containing a chiral tripodal
phospholane has been prepared by reaction with [Ru­(η4-COD)­(η3-methylallyl)2] via elimination
of isobutene. The ruthenium–carbon bonds of this compound were
reversibly cleaved by H2, resulting in an equilibrium between
a tri- and a tetrahydride (4 and 5). T1 relaxation time measurements revealed the
nonclassical nature of the fluctuating hydrides. Release of the gas
led to complete re-formation of the cyclometalated compound. Reaction
of 3 with D2 afforded D10-5, in which six ortho-phenyl protons and four hydrides were replaced by deuterium. Furthermore,
diphenylsilane was found to readily insert into one Ru–C bond
to form 6, containing a κ3-dihydridosilicate
fragment. On the basis of deuterium labeling experiments, the fast
exchange between the two hydrides was shown to include a reductive
elimination/oxidative addition step involving the remaining metalated
phenyl group. Again, pressurization of 6 with H2 resulted in reversible cleavage of the remaining Ru–C bond,
yielding the corresponding trihydride 7.