Hydrogenolysis of the half‐sandwich penta‐arylcyclopentadienyl‐supported heavy alkaline‐earth‐metal alkyl complexes (CpAr)Ae[CH(SiMe3)2](S) (CpAr=C5Ar5, Ar=3,5‐iPr2‐C6H3; S=THF or DABCO) in hexane afforded the calcium, strontium, and barium metal–hydride complexes as the same dimers [(CpAr)Ae(μ‐H)(S)]2 (Ae=Ca, S=THF, 2‐Ca; Ae=Sr, Ba, S=DABCO, 4‐Ae), which were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. 2‐Ca, 4‐Sr, and 4‐Ba catalyzed alkene hydrogenation under mild conditions (30 °C, 6 atm, 5 mol % cat.), with the activity increasing with the metal size. A variety of activated alkenes including tri‐ and tetra‐substituted olefins, semi‐activated alkene (Me3SiCH=CH2), and unactivated terminal alkene (1‐hexene) were evaluated.

Hydrogenolysis of the scorpionate-supported barium alkyl complex (Tp )Ba[CH(SiMe ) ](THF) (Tp =hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate) afforded the dinuclear barium hydrido complex [(Tp )Ba(μ-H)] (2), which was characterized by NMR spectroscopy and single-crystal X-ray analysis. Exposure of 2 with 1 atm of CO resulted in a reductive coupling process to form the cis-ethendiolate dianion (3). Reaction of 2 with one equivalent of PhC≡C-C≡CPh gave barium 1,4-diphenyl-2-butyne-1,4-diyl complex {[(Tp )Ba] (PhCH-C≡C-CHPh) (4).