Cooperative
E–H (E = B, Si) bond activations employing κ2-N,S-chelated ruthenium borate species, [PPh3{κ2-N,S-(NS2C7H4)}Ru{κ3-H,S,S′-H2B(NC7H4S2)2}], (1) are established. Treatment of 1 with BH3·SMe2 yielded the six-membered
ruthenaheterocycle [PPh3{κ2-S,H-(BH3NS2C7H4)}Ru{κ3-H,S,S’-H2B(C7H4NS2)2}] (2) formed
by a hemilabile ring opening of a Ru–N bond and capturing of
a BH3 unit coordinated in an “end-on” fashion.
On the other hand, the bulky borane H2BMes shows different
reactivity with 1 that led to the formation of the two
dihydroborate complexes [{κ3-S,H,H-(NBH2Mes)(S2C7H4)}Ru{κ3-H,S,S’-H2B(C7H4NS2)2}] (3) and [PPh3{κ3-S,H,H-(NBH2Mes)(S2C7H4)}Ru(κ2-N,S-C7H4NS2)]
(4), in which H2BMes has been inserted into
the Ru–N bond of the initial κ2-N,S-chelated ligand. In an attempt to directly activate hydrosilanes
by 1, reactions were carried out with H2SiPh2 that yielded two isomeric five-membered ruthenium silyl complexes,
namely [PPh3{κ2-S,Si-(NSiPh2)(S2C7H4)}Ru{κ3-H,S,S’-H2B(C7H4NS2)2}] (5a,b), and the hydridotrisilyl complex [Ru(H){κ2-S,Si-(SiPh2NC7H4S2}3] (6). These complexes were
generated by Si–H bond activation with the release of H2 and the formation of N–Si and Ru–Si bonds.
When the reaction of 1 was carried out in the presence
of PhSiH3, the reaction only produced the analogous complexes
[PPh3{κ2-S,Si-(NSiPhH)(S2C7H4)}Ru{κ3-H,S,S’-H2B(C7H4NS2)2}] (5a′,b′). Density functional theory (DFT) calculations have been used to
probe the bonding modes of boranes/silane with the ruthenium center.
