Copper and sliver complexes containing organic azide ligands: Syntheses, structures, and theoretical investigation of [HB(3,5-(CF3)(2)Pz)(3)]CuNNN(1-Ad) and [HB(3,5-(CF3)(2)Pz)(3)]AgN(1-Ad)NN (where Pz = pyrazolyl and 1-Ad=1-adamantyl)

Treatment of [HB(3,5-(CF3)(2)Pz)(3)]Na(THF) with. CF3SO3Cu followed by 1-az idoadamantane affords [HB(3,5-(CF3)(2)Pz)(3)]CuNNN(1-Ad) in 65% yield. The solid state structure shows that the copper atom is coordinated to the term inal nitrogen atom (N-T) of the azidoadamantane ligand. The related silver( I) adduct can be prepared in 80% yield by the treatment of [HB(3,5-(CF3)(2) Pz)(3)]Ag(THF) with 1-azidoadrunantclne. However, [HB(3,5-(CF3)(2)Pz)(3)]Ag N(1-Ad)NN shows a different bonding mode where the silver atom coordinates to the alkylated nitrogen atom (N-A) Of the azidoadamantane ligand. Asymmet ric stretching bands of the azido group for copper and silver adducts appea r at 2143 and 2120 cm(-1), respectively. Theoretical investigation shows th at steric effects do not play a dominant role in determining the bending mo de of the azide ligand in these two metal complexes. Although the copper(I) ion affinity for the two coordinating sites NT and NA is nearly identical, copper-azide back-bonding interactions favor the copper-N-T mode of bondin g over the copper-N-A mode. Silver (a very poor back-bonding metal) prefers the NA Site for coordination. The NA Site has a significantly higher proto n affinity and slightly higher sodium ion affinity. Important structural pa rameters for [HB(3,5-(CF3)(2)Pz)(3)]CuNNN( 1-Ad) and [HB(3,5-(CF3)(2)Pz)(3) ]AgN(1-Ad)NN are as follows: Cu-N-T 1.861(3) Angstrom, N-T-N 1.136(4) Angst rom, N-N-A 1.219(4) Angstrom, N-T-N-N-A 173.1(3)degrees; Ag-N-A 2.220(5) An gstrom, N-T-N 1.143(12) Angstrom, N-N-A 1.1227(10) Angstrom N-T-N-N-A 176.8 (12)degrees. Overall, the azidoadamantane ligand does not undergo any signi ficant changes upon coordination to Cu(I) or Ag(I) ions.