Reversible hydrosilane addition to pyridines enabled by low-coordinate Ca(ii) and Yb(ii) hydrides

Abstract

The reactions of amides [tBu₂CarbAr₂]MN(SiMe₃)₂(THF) (M = Ca (5), Yb (6)) and [tBu₂CarbAr₂]MN(SiMe₃)₂ (M = Ca (7), Yb (8)) coordinated by a bulky carbazolyl ligand (tBu₂CarbAr₂ = 3,6-di-tert-butyl-1,8-bis(3,5-di-tert-butylphenyl)-carbazolyl) with PhSiH₃ allowed for the synthesis of isolable low-coordinate hydrides {[tBu₂CarbAr₂]MH(THF)}₂ (M = Ca (11), Yb (12)) and {[tBu₂CarbAr₂]MH(η⁶-C₇H₈)}₂ (M = Ca (11), Yb (12)) featuring dimeric structures. Hydrides 11 and 12, as well as amides 7 and 8, proved to be efficient catalysts for PhSiH₃ addition to pyridines at ambient T. However, the same catalyst at 90° C catalyzes the opposite reaction: the release of the parent silane and the restoration of the aromatic pyridine system.