The compound (SiEt3)2(B12F12) was generated in hexane by reacting SiHEt3 with (CPh3)2(B12F12) in a 2:1 mol ratio. A small crop of crystals of the very reactive compound (SiEt3)2(B12F12) suitable for diffraction was isolated and its structure was determined by X-ray crystallography (Pbca, a = 16.67(1) Å, b = 17.77(1) Å, c = 18.53(1) Å). Two SiR3+ cation-like moieties are weakly bonded to F atoms on opposite sides of the B12F122− anion. The SiF distances are 1.832(2) and 1.842(2) Å. The BF(Si) distances, at 1.459(5) and 1.464(5) Å, are 0.087−0.109 Å (i.e., 17–21 σ) longer than the other ten BF distances. This is the first time that statistically significant BF bond lengthening due to coordination of B12F122− to a cation has been observed.