In order to isolate a monometallic Mg radical, the precursor (Am)MgI⋅(CAAC) (1) was prepared (Am=tBuC(N‐DIPP)2, DIPP=2,6‐diisopropylphenyl, CAAC=cyclic (alkyl)(amino)carbene). Reduction of a solution of 1 in toluene with the reducing agent K/KI led to formation of a deep purple complex that rapidly decomposed. Ball‐milling of 1 with K/KI gave the low‐valent MgI complex (Am)Mg⋅(CAAC) (2) which after rapid extraction with pentane and crystallization was isolated in 15 % yield. Although a benzene solution of 2 decomposes rapidly to give Mg(Am)2 (3) and unidentified products, the radical is stable in the solid state. Its crystal structure shows planar trigonal coordination at Mg. The extremely short Mg−C distance of 2.056(2) Å indicates strong Mg−CAAC bonding. Calculations and EPR measurements show that most of the spin density is in a π* orbital located at the C−N bond in CAAC, leading to significant C−N bond elongation. This is supported by calculated NPA charges in 2: Mg +1.73, CAAC −0.82. Similar metal‐to‐CAAC charge transfer was calculated for M0(CAAC)2 and [MI(CAAC)2+] (M=Be, Mg, Ca) complexes in which the metal charges range from +1.50 to +1.70. Although the spin density of the radical is mainly located at the CAAC ligand, complex 2 reacts as a low‐valent MgI complex: reaction with a I2 solution in toluene gave (Am)MgI⋅(CAAC) (1) as the major product.

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.

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The previously reported K aluminyl complex [(BDI-H)AlˉK+]2 was converted in Li+ or Na+ salts by a salt metathesis reaction with Li(BPh4) or Na(BPh4), respectively; BDI-H = dianionic [(DIPP)N-C(Me)=C(H)-C(=CH2)-N(DIPP)2ˉ] and DIPP...

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.