Structural investigations of the hexavanadium core {V₆O₁₉} in 'oxidized', mixed valence and 'reduced' clusters of the type [V^V_6-nV^IV_n O_13-n(OH)_n{(OCH₂)₃CR}₂]^2-, n=0, 3 and 6

The reactions of [(n-C₄H₉)₄N]₃[H₃V₁₀O₂₈] with the tris(hydroxymethyl)methane derived ligands (HOCH₂)₃CR yield hexavanadate clusters of the type [(n-C₄H₉)₄N]₂[V₆O₁₃{(OCH₂)₃CR}2] (R-NHC(O)CHCH₂ (1) and -NO₂ (1a)) and [C₅H₅NH]₂[V₆O₁₃{(OCH₂)₃CCH₃}₂]·2Me₂NCOH (2). These V(V) clusters are readily reduced by organohydrazines to yield the mixed valence V(V)/V(IV) cluster [(n-C₄H₉)₄N]₂[V^V₃V^IV₃O₁₀(OH)₃{(OCH₂)₃CNO₂}₂]·0.67CH₂Cl₂ (3) and the reduced V(IV) cluster [(n-C₄H₉)₄N]₂[V^IV₆O₇(OH)₆{(OCH₂)₃CCH₃}₂]·2HNPhNHPh (4). Complexes 1-4 share the common hexametalate core {M₆O₁₉} which is, however, distorted from the regular octahedral symmetry adopted by [Mo₆O₁₉]^2- and [Nb₆O₁₉]^8- because of the substitution of doubly-bridging oxo groups of the parent structure type by alkoxy donor oxygens and as a consequence of the reduction of metal sites in 3 and 4. Crystal data: 1, space group P2₁/c, a=10.602(3), b=17.774(5), c=16.451(6) Å, β=95.42(2)°, V=3086(2) ų, Z=2, D_calc=1.44 g/cm³; R=0.060 based on 2631 reflections. 2, orthorhombic Pbca,a=16.966(4), b=20.235(4), c=11.524(2) Å, V=3956(2) ų, Z=4, D_calc=1.77 g/cm³; R=0.034 based on 2729 reflections; 3, triclinic P1, a=13.526(2), b=27.032(5), c=12.950(2) Å, α=100.70(1), β=104.33(1), γ=75.56(1)°, V=4403(2) ų, Z=3, D_calc=1.52 g/cm³; R=0.058 based on 4494 reflections. 4, monoclinic P2₁/c, a=13.357(2), b=14.416(2), c=21.584(4) Å, β=105.83(2)°, V=3998(2) ų, Z=2, D_calc=1.33 g/cm³; R=0.058 based on 2972 reflections.