Reactions of WCl2L4 (L = a phosphine). 1. A new class of tungsten(II) ethylene complexes

Article abstract of DOI:10.1021/om00086a013

WCl₂L₄ can be prepared by reducing WCl₄L_n with 2 equiv of sodium amalgam in the presence of L (L = PMe₃, n = 3; L = PMe₂Ph and PMePh₂, n = 2). Phosphine is displaced from WCl₂L₄ by ethylene to give first WCl₂L₃(C₂H₄) (L = PMe₃) and then WCl₂L₂(C₂H₄)₂. WCl₂(PMe₃)₂(C₂H₄) ₂ reacts with TlBF₄, AlCl₃, and AlMe₃ to give cationic complexes. The X-ray crystal structure of one of these, [WMe-(PMe₃)₂(C₂H₄) ₂][ClAlMe_xCl_3-x], was determined. The crystals are monoclinic (P2₁/n) with a = 9.922 (2) ?, b = 7.419 (1) ?, c = 29.241 (4) ?, β = 92.79 (2)°, V = 2150 ?³, and Z = 4. The three-dimensional X-ray data were measured with the θ-2θ scan technique with a scintillation detector. The structure was resolved by Patterson and Fourier methods and refined by full-matrix least-squares calculations to give R(F_o) = 0.025 and R_w(F_o) = 0.032 for 1362 observations above 2σ. The solid state structure consists of monomeric units with cis ethylenes, trans phosphines, and a weakly coordinated aluminate. NMR and conductivity data suggest the equilibrium in solution of this structure with an ionic complex formed by loss of the aluminate. The reaction of this complex with tmeda (N,N,N′,N′ -tetramethylethylenediamine) or other Lewis bases gives neutral WMeCl(PMe₃)₂(C₂H₄)₂ that loses Cl^- in polar, noncoordinating solvents.