Complex [( DIPeP BDI)Ca] 2 (C 6 H 6 ), with a C 6 H 6 2À dianion bridging two Ca 2 + ions, reacts with benzene to yield [( DIPeP BDI)Ca] 2 (biphenyl) with a bridging biphenyl 2À dianion ( DIPeP BDI = HC[C(Me)N-DIPeP] 2 ; DIPeP = 2,6-CH(Et) 2 -phenyl). The biphenyl complex was also prepared by reacting [( DIPeP BDI)Ca] 2 (C 6 H 6 ) with biphenyl or by reduction of [( DIPeP BDI)CaI] 2 with KC 8 in presence of biphenyl. Benzene-benzene coupling was also observed when the deep purple product of ballmilling [( DIPP BDI)CaI(THF)] 2 with K/KI was extracted with benzene (DIPP = 2,6-CH(Me) 2 -phenyl) giving crystalline [( DIPP BDI)Ca(THF)] 2 (biphenyl) (52 % yield). Reduction of [( DIPeP BDI)SrI] 2 with KC 8 gave highly labile [( DIPeP BDI)Sr] 2 (C 6 H 6 ) as a black powder (61 % yield) which reacts rapidly and selectively with benzene to [( DIPeP BDI)Sr] 2 (biphenyl). DFT calculations show that the most likely route for biphenyl formation is a pathway in which the C 6 H 6 2À dianion attacks neutral benzene. This is facilitated by metal-benzene coordination.

Complex [( DIPeP BDI)Ca] 2 (C 6 H 6 ), with a C 6 H 6 2À dianion bridging two Ca 2 + ions, reacts with benzene to yield [( DIPeP BDI)Ca] 2 (biphenyl) with a bridging biphenyl 2À dianion ( DIPeP BDI = HC[C(Me)N-DIPeP] 2 ; DIPeP = 2,6-CH(Et) 2 -phenyl). The biphenyl complex was also prepared by reacting [( DIPeP BDI)Ca] 2 (C 6 H 6 ) with biphenyl or by reduction of [( DIPeP BDI)CaI] 2 with KC 8 in presence of biphenyl. Benzene-benzene coupling was also observed when the deep purple product of ballmilling [( DIPP BDI)CaI(THF)] 2 with K/KI was extracted with benzene (DIPP = 2,6-CH(Me) 2 -phenyl) giving crystalline [( DIPP BDI)Ca(THF)] 2 (biphenyl) (52 % yield). Reduction of [( DIPeP BDI)SrI] 2 with KC 8 gave highly labile [( DIPeP BDI)Sr] 2 (C 6 H 6 ) as a black powder (61 % yield) which reacts rapidly and selectively with benzene to [( DIPeP BDI)Sr] 2 (biphenyl). DFT calculations show that the most likely route for biphenyl formation is a pathway in which the C 6 H 6 2À dianion attacks neutral benzene. This is facilitated by metal-benzene coordination.

Low‐valent MgI complexes like (BDI)Mg‐Mg(BDI) have found wide‐spread application as specialty reducing agents (BDI = β‐diketiminate). Also their redox reactivity was extensively investigated. In contrast, attempts to isolate similar CaI complexes led to reduction of the aromatic solvents or N2. Complex (DIPePBDI)Ca(μ6,μ6‐C6H6)Ca(DIPePBDI) (VIII) should be regarded a CaII complex with a bridging C6H62ˉ dianion (DIPePBDI = HC[C(Me)N‐DIPeP]2, DIPeP = 2,6‐C(H)Et2‐phenyl). It can react as a CaI synthon by releasing benzene and two electrons. Herein we describe the reactivity of VIII with benzene, biphenyl, naphthalene, anthracene, COT, Ph3SiCl, PhSiH3, a (BDI)AlI2 complex, H2, PhX (X = F, Cl, Br, I), tBuOH and tBuCH2I. The C6H62ˉ dianion in VIII can react as a 2eˉ source, a nucleophile or a Brønsted base. In some cases radical reactivity cannot be excluded. Crystal structures of (DIPePBDI)Ca(μ8,μ8‐COT)Ca(DIPePBDI) (1) and [(DIPePBDI)CaX·(THF)]2 (X = F, Cl, Br, I) (2‐5) are described.