Novel tetrameric rhenium(V) complexes have been prepared from [ReNCl2(PPh3)2] and [ReN(PMe2Ph) · (S2CNEt)2], respectively. [ReNCl2(PPh3)2] reacts with 1.5 equivalents of KS2CNEt2 in methanol to yield the unusual dark red species [{cyclo-ReN}4(S2CNEt2)6(MeOH) 2 · (PPh3)2][BPh4]2 · CH2Cl2 · 2 H2O (1). The crystal structure of the tetramer (triclinic, space group P1, a = 13.842(2), b = 15.213(2), c = 16.796(3) Å, α = 67.88(1), β = 70.90(1), γ = 88.05(1)°, U = 3080.2(8) Å3, Z = 1) shows four rhenium atoms in a square configuration which are bridged via linear asymmetric Re≡N-Re groups with bond lengths of about 169 and 203 pm. The molecule contains a centre of symmetry with two distinct octahedral rhenium environments. The first rhenium environment contains two bidentate dithiocarbarnate ligands which complete the octahedral geometry and the second contains a bidentate dithiocarbamate ligand, coordinated methanol and has retained a single phosphine coligand. A symmetric compound containing the {cyclo-ReN}4 core is obtained from the reaction of [ReN(PMe2Ph)(S2CNEt2)2] with Al2Cl6 in acetone. [{cyclo-ReN}4(S2CNEt2)4Cl4 (PMe2Ph)4] · 2 acetone (2) forms red crystals (monoclinic, space group C2/c. a = 21.432(6), b = 13.700(3), c = 28.060(9) Å, β = 102.37(1)°, U = 8048(4) Å3, Z = 4) with each rhenium atom coordinated by a bidentate dithiocarbamato, a phosphine and a chloro ligand. The non-planar 8-membered {ReN}4 ring contains asymmetric Re≡N-Re bridges (mean values: 1.69 Å and 2.029 Å, respectively). In contrast, reaction of [ReNCl(S2CNEt2)(PMe2Ph)2] with one equivalent of K[S2CN(Me)CH2CH2NMe3]I gave the mixed dithiocarbamato-cation [ReN(S2CNEt2) · (S2CN(Me)CH2CH2NMe3)(PMe 2Ph)]+ (3) which was isolated as a tetraphenylborate salt.
