(TRIALKYLSTANNYL)CUPRATES - A SPECTROSCOPIC AND CHEMICAL INVESTIGATION

Low-temperature H-1, C-13, and Sn-119 NMR spectroscopic techniques wer e used to probe the nature of cuprates derived from Me(2)SnLi, CuCN, o r CuBr . Me(2)S. In THF, addition of Me(2)SnLi , and CuX (X = Br or CN ) gives aggregated [Me(3)SnCu . LiX](n). When the ratio of stannyl ani on to cuprous cation is 2:1, mixtures of (Me(3)Sn)(3)Cu2Li, (Me(3)Sn)( 2)CuLi . LiX, and (Me(3)Sn)(3)CuLi2 are formed. This behavior is unlik e either homo trialkylsilylcyanocuprates, which form (R(3)Si)(2)Cu(CN) Li-2 at 2:1 ratios of silyl anion to cuprous ion, or mixed trialkylsta nnyl- or trialkylsilylcuprates, which exist as (R(3)M)Cu(R')(CN)Li-2 ( M = Si or Sn and R' = Me or Bu). (R(3)Sn)(3)CuLi2 is the major species when the stannyl anion to cuprous cation ratio reaches 3:1. On the ot her hand, the analogous magnesium cuprates are discrete species in sol ution and possess differential reactivity.