Synthesis and characterization of the metalloplumbylenes (eta(5)-C5H5) (CO)(3)M-Pb-C6H3-2,6-Trip(2) (M = Cr, Mo, or W; Trip = -C6H2-2,4,6-i-Pr-3)

The reaction of Pb(Br)C6H3-2,6-Trip(2) (Trip = C6H2-2,4,6-i-Pr-3), generate d in situ, with the salts Na[M(eta(5)-C5H5)(CO)(3)]. DME (M = Cr, Mo, or W; DME = 1,2-dimethoxyethane) affords the novel green, crystalline metalloplu mbylenes (eta(5)-C5H5)(CO)(3)M-Pb-C6H3-2,6 -Trip(2) (M = Cr, 1; Mo, 2; W, 3 ) in moderate yield. The compounds were characterized spectroscopically (H- 1, C-13, and Pb-207 NMR, IR, and UV-vis) and by combustion analysis. In add ition the X-ray crystal structures of 1-3 were determined. The compounds fe ature strongly bent geometries at lead (M-Pb-C = 108.6(2)-113.58(9)degrees) and relatively long M-Pb distances (2.9092(9) Angstrom, Cr; 2.9845(7) Angs trom, Mo; 2.9809(10) Angstrom, 3.0055(6) Angstrom W), which are consistent with single M-Pb bonding. The stability of the complexes, which melt with d ecomposition in the range 210-226 degrees C, is attributed to steric protec tion of the metal centers by the very large -C6H3-2,6-Trip(2) substituent. The compounds are the first examples of metalloplumbylenes that feature a b ent two-coordinate lead geometry.