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Cooperative B–H and Si–H Bond Activations by κ2N,S‑Chelated Ruthenium Borate Complexes

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posted on 2021-01-04, 09:29 authored by Mohammad Zafar, Rongala Ramalakshmi, Asif Ahmad, P. K. Sudhadevi Antharjanam, Sébastien Bontemps, Sylviane Sabo-Etienne, Sundargopal Ghosh
Cooperative E–H (E = B, Si) bond activations employing κ2-N,S-chelated ruthenium borate species, [PPh32-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 [PPh32-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 [PPh33-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 [PPh32-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 [PPh32-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.

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