Binding, Release and Functionalization of Intact Pnictogen Tetrahedra Coordinated to Dicopper Complexes.

The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu (μ,η  : η -MeCN)][X] (X=weakly coordinating anion, NTf (1 a), FAl[OC F (C F )] (1 b), Al[OC(CF ) ] (1 c)) was replaced by white phosphorus (P ) or yellow arsenic (As ) to yield [(DPFN)Cu (μ,η  : η -E )][X] (E=P (2 a-c), As (3 a-c)). The molecular structures in the solid state reveal novel coordination modes for E tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E tetrahedra with release of P or As and formation of [(DPFN)Cu (μ,η  : η - NHC)][X] (4 a,b) or to an opening of one E-E bond leading to an unusual E butterfly structural motif in [(DPFN)Cu (μ,η  : η -E NHC)][X] (E=P (5 a,b), E=As (6)). With a cyclic alkyl amino carbene ( CAAC), cleavage of two As-As bonds was observed to give two isomers of [(DPFN)Cu (μ,η  : η -As CAAC)][X] (7 a,b) with an unusual As -triangle+1 unit.