Formation of a Cationic Calcium Hydride Cluster with a “Naked” Triphenylsilyl Anion by Hydrogenolysis of Bis(triphenylsilyl)calcium

Protonolysis of bis­(triphenylsilyl)­calcium
[Ca­(SiPh3)2(THF)4] (1; THF = tetrahydrofuran) with the NNNN-type macrocyclic amido triamine
(Me3TACD)H (TACD = 1,4,7-triazacyclododecane) gave the
heteroleptic calcium complex [Ca­(Me3TACD)­SiPh3] (2) in quantitative yield. Hydrogenolysis of 2 gave the cationic tricalcium dihydride cluster [Ca3H2(Me3TACD)3]+(SiPh3)−·2THF (4a) in high yield
with concomitant formation of HSiPh3. In the crystal, 4a consists of a cluster cation and a free triphenylsilyl
anion. 1H NMR spectroscopy and deuterium labeling experiments
confirmed the selective cleavage of dihydrogen by the highly polar
Ca–Si bond in 1.