Triangular trinuclear clusters of tungsten containing bromine atoms as terminal ligands: syntheses and structural characterizations of [W 3S 4Br 3(dmpe) 3][Y], where dmpe=1,2-bis(dimethylphosphino)-ethane and Y −Br − or PF 6−

Abstract

The triangular trinuclear cluster [W 3S 4Br 3(dmpe) 3] + has been prepared in high yield by reactions between WBr 5 and NaBH 4 or NaB(C 2H 5) 3H as reducing agent in THF, and subsequent addition of methanolic solutions of NaHS and dmpe ligand. It has been isolated as the bromide, [W 3S 4Br 3(dmpe) 3]Br ( 1) and as the fluorophosphate, [W 3S 4Br 3(dmpe) 3]PF 6 ( 2). Compound 1 crystallizes in the orthorhombic space group Fdd2 with a=26.112(7), b=64.970(21), c=20.555(4) Å, V=34881(27) Å 3 and Z=32. The final refinement converged to the residual values R=0.053 and R w=0.068. There are two independent formula units in the unit cell, but the virtually identical cations are both chiral and possess C 3 symmetry. Compound 2 crystallizes in the cubic space group I23 with a=20.999(2) Å, V=9260(3)Å 3 and Z=8; R=0.039, R w=0.057. The cation has crystallographic three-fold symmetry. The cation in 2 is identical to those in 1. The WW distances are in the range 2.760–2.770 Å (for 1a) and 2.732–2.766 Å (for 1b) and the average WBr distances in 1a and 1b are 2.640(4) and 2.626(4) Å, respectively. The WW distances and the WBr distances in 2 are 2.759(2) and 2.641(4) Å, respectively. Each metal atom in the [W 3S 4Br 3(dmpe) 3] + ions is attached to one capping sulfur atom, two bridging sulfur atoms, one bromine atom and one chelating dmpe ligand. One P atom in dmpe ligand is trans to μ 3-S and the other P atom is trans to a μ 2-S atom. UV-Vis and NMR spectra for 1 are also reported.