A Dinitrogen Dicopper(I) Complex via a Mixed‐Valence Dicopper Hydride

Low‐temperature reaction of the tris(pyrazolyl)borate copper(II) hydroxide [ iPr2 TpCu] 2 (μ‐OH) 2 with triphenylsilane under a dinitrogen atmosphere gives the bridging dinitrogen complex [ iPr2 TpCu] 2 (μ‐1,2‐N 2 ) ( 3 ). X‐ray crystallography reveals an only slightly activated N 2 ligand (N‐N: 1.111(6) Å) that bridges between two monovalent iPr2 TpCu fragments. While DFT studies of mono‐ and dinuclear copper dinitrogen complexes suggest weak π‐backbonding between the d 10 Cu I centers and the N 2 ligand, they reveal a degree of cooperativity in the dinuclear Cu‐N 2 ‐Cu interaction. Addition of MeCN, CNAr 2,6‐Me , or O 2 to 3 releases N 2 with formation of iPr2 TpCu(L) (L=NCMe, CNAr 2,6‐Me2 ) or [ iPr2 TpCu] 2 (μ‐η 2 :η 2 ‐O 2 ) ( 1 ). Addition of triphenylsilane to [ iPr2 TpCu] 2 (μ‐OH) 2 in pentane allows isolation of a key intermediate [ iPr2 TpCu] 2 (μ‐H) ( 5 ). Although 5 thermally decays under N 2 to give 3 , it reduces unsaturated substrates, such as CO and HC≡CPh to HC(O)H and H 2 C=CHPh, respectively.