The preparation of [M2Cp2(CO)(4)(mu-eta(2)-PE)] (E = As or Sb), the first complexes with naked heterodiatomic Group 15 ligands, and of their adducts with W(CO)(5)

摘要

Addition of one equivalent of the Group 15 trichlorides ECl3 (E=P, As, or Sb) to the phosphido-bridged dimetallic anions [M2Cp2(CO)(4)(mu-PH2)](-) (M=Mo or W) afforded moderate yields of the complexes [M2Cp2(CO)(4)(mu-eta(2)-PE)], which feature a pseudo-tetrahedral M2PE core. Treatment of the new complexes with [W(CO)(5)(THF)] led to preferential co-ordination of this Lewis acid to the phosphorus atom. The additional co-ordination of a W(CO)(5) fragment to the As atom in [M2Cp2(CO)(4)(mu-eta(2)-PAs)] to give a 2:1 adduct is reversible at room temperature on dissolution in solvents such as CH2Cl2 and THF; similar co-ordination to the Sb atom in [M2Cp2(CO)(4)(mu-eta(2)-PSb)] is not observed. The crystal structures of the 1:1 adducts and of one 2:1 adduct have been determined. The P-As distances in [W2Cp2(CO)(4){mu-eta(2)-AsPW(CO)(5)}] (2.217(5) Angstrom) and that in [Mo2Cp2(CO)(4)(mu-eta(2)-AsP{W(CO)(5)}(2))], in which the As and P atoms are disordered (2.223(3) Angstrom), are intermediate between the P-P and As-As distances in homodiatomic E-2 complexes. Similarly, the P-Sb distances in the two crystallographically independent molecules of [Mo2Cp2(CO)(4){mu-eta(2)-SbPW(CO)(5)}] (2.401(2), 2.410(2) Angstrom) are intermediate in length between the P-P and Sb-Sb distances in related homodiatomic E-2 complexes. [References: 17]