The reaction of [PPh4][MoCl4(THF)2] with PEt3 affords [PPh4]2[Mo2Cl8(PEt3)] as a dark red solid with two molecules of Ch2Cl2 of crystallization. The crystals are triclinic (P1) with Z = 2 for a unit cell of the following dimensions: a = 13.168(5), b = 21.436(6), c = 11.852(4) A ̊, α = 91.16(3), β = 100.07(3), γ = 107.22(3)°, V = 3337 A ̊3. In the face-sharing bioctahedral (FSBO) anion, the MoMo distance is 2.767(2) Å. The structure is compared to a number of other FSBO structures of general formula Mo2Cl9-n(PR3)n. © 1995.