AbstractLow‐temperature1H,13C, and119Sn NMR spectroscopic techniques were used to probe the nature of cuprates derived from Me3SnLi, CuCN, or CuBr · Me2S. In THF, addition of Me3SnLi and CuX (X = Br or CN) gives aggregated [Me3SnCu · LiX]n. When the ratio of stannyl anion to cuprous cation is 2 : 1, mixtures of (Me3Sn)3Cu2Li, (Me3Sn)2CuLi · LiX, and (Me3Sn)3CuLi2are formed. This behavior is unlike either homo trialkylsilycyanocuprates, which form (R3Si)2Cu(CN)Li2at 2 : 1 ratios of silyl anion to cuprous ion, or mixed trialkylstannyl‐ or trialkylsilyl‐cuprates, which exist as (R3M)Cu(R′)(CN)Li2(M = Si or Sn and R′ = Me or Bu). (R3Sn)3CuLi2is the major species when the stannyl anion to cuprous cation ratio reaches 3 : 1. On the other hand, the analogous magnesium cuprates are discrete species in solution and possess differentia