Studies on transition-metal peroxo complexes. Part 7. Molybdenum( VI ) and tungsten( VI ) carboxylato peroxo complexes, and the X-ray crystal structure of K ₂ [MoO(O ₂ ) ₂ (glyc)]·2H ₂ O

New complexes [MoO(O2)2L]2–[L = malate, tartrate (tart), tartronate, quinate, or glycolate (glyc)], [WO(O2)2L]2–(L = citrate, tartrate, malate, or glycolate), and [W2O2(O2)4(tart)]4– are reported, and modified preparations given for [MO(O2)2L]2– and [MO2(O2)L(H2O)]2–(M = Mo or W; L = oxalate). Raman and i.r. spectra of the solid complexes, and Raman, 13C and 95Mo n.m.r. spectra of their aqueous solutions, have been measured and are used to suggest the structures of the species in the solid state and solution. The X-ray crystal structure of K2[MoO(O2)2(glyc)]·2H2O has been determined: triclinic, space group P, with a= 7.222(4), b= 7.950(6), c= 10.450(5)Å, α= 67.81(4), β= 73.72(7), γ= 64.84(4)° at 20 °C, and Z= 2; the structure has been refined to R= 0.035.