Stepwise Cluster Assembly Using VO₂(acac) as a Precursor:  cis-[VO(OCH(CH₃)₂)(acac)₂], [V₂O₂(μ-OCH₃)₂(acac)₂(OCH₃)₂], [V₃O₃{μ,μ-(OCH₂)₃CCH₃}₂(acac)₂(OC₂H₅)], and [V₄O₄(μ-O)₂(μ-OCH₃)₂(μ₃-OCH₃)₂(aca

Abstract

The studies of an underexplored synthetic reagent, VO(2)(acac) (Hacac = acetylacetone) and semirational strategies for the formation of a complete series of simple vanadium(V) alkoxide clusters in alcohol-containing solvents. The neutral mono-, di-, tri-, and tetranuclear oxovanadium(V) complexes [V(2)O(2)(&mgr;-OCH(3))(2)(acac)(2)(OCH(3))(2)] (1), [V(4)O(4)(&mgr;-O)(2)(&mgr;-OCH(3))(2)(&mgr;(3)-OCH(3))(2)(acac)(2)(OCH(3))(2)].2CH(3)CN (2), [V(4)O(4)(&mgr;-O)(2)(&mgr;-OCH(3))(2)(&mgr;(3)-OCH(3))(2)(acac)(2)(OCH(3))(2)] (3), [V(3)O(3){&mgr;,&mgr;-(OCH(2))(3)CCH(3)}(2)(acac)(2)(OR)] (R = CH(3) (4), C(2)H(5) (5)), and cis-[VO(OCH(CH(3))(2))(acac)(2)] (6) with alkoxide and acac(-) ligands were obtained by reaction of VO(2)(acac) with a monoalcohol and/or a tridentate alcohol. The structures of complexes 1-3, 5, and 6 were determined by X-ray diffraction methods. Complex 1 crystallized in the monoclinic system, P2(1)/n, with a = 7.8668(5) Å, b = 15.1037(9) Å, c = 8.5879(5) Å, beta = 106.150(1) degrees, V = 980.1(1) Å(3), Z = 2, and R (wR2) = 0.040 (0.121). Complex 2 crystallized in the monoclinic system, P2(1)/n, with a = 8.531(2) Å, b = 14.703(3) Å, c = 12.574(2) Å, beta = 95.95(2) degrees, V = 1568.7(5) Å(3), Z = 2, and R (wR2) = 0.052 (0.127). Complex 3 crystallized in the triclinic system, P&onemacr;, with a = 8.5100(8) Å, b = 8.9714(8) Å, c = 10.3708(10) Å, alpha = 110.761(1) degrees, beta = 103.104(1) degrees, gamma = 100.155(1) degrees, V = 691.85(11) Å(3), Z = 1, and R (wR2) = 0.040 (0.105). Complex 5 crystallized in the monoclinic system, P2(1)/n, with a = 14.019(2) Å, b = 11.171(2) Å, c = 19.447(3) Å, beta = 109.18(1) degrees, V = 2876.5(8) Å(3), Z = 4, and R (wR2) = 0.062 (0.157). Complex 6 crystallized in the monoclinic system, P2(1)/n, with a = 15.0023(8) Å, b = 8.1368(1) Å, c = 26.5598(2) Å, beta = 95.744(1) degrees, V = 3225.89(8) Å(3), Z = 8, and R (wR2) = 0.060 (0.154). Complex 1 is a discrete, centrosymmetric dimer in which two vanadium atoms are bridged by two methoxide ligands. Compound 2 contains a V(4)O(4) eight-membered ring with both &mgr;-oxo and &mgr;-alkoxo bridging ligands; the ring is capped above and below by two triply bridging methoxo ligands. Compound 3 has the same structure as 2. The three vanadium atoms in complex 5 are linked by four bridging oxygen atoms from two tridentate thme(3)(-) ligands to form a V(3)O(4) chain in which V-O bonds alternate in length. The V-O(isopropoxo) bond in 6 is cis to V=O, and the V-O(acac) bond trans to the oxo group is relatively long. The V(2)O(2) rings of complex 1 and the mononuclear 1:2 complex can be considered to be the basic building block of the trinuclear complexes 4 and 5 and the tetranuclear complex 2, acting to extend the vanadium-oxide framework. (51)V and (1)H NMR spectroscopic studies of the solution state of complexes 1-6 revealed dramatic differences in structural and hydrolytic stability of these complexes. Compounds 1 and 3 only remained intact at low temperature in CDCl(3) solution, whereas the mononuclear compound 6 could remain a...

Synthesis and Interconversion of V4, V7, and V8 Oxide Clusters: Unexpected Formation of Neutral Heptanuclear Oxido(alkoxido)vanadium(V) Clusters [V7O17(OR)(4,4′-tBubpy)3] (R = Et, MeOC2H4)

“…This transformation was investigated in some detail by spectral measurements. When 2 was dissolved in CD 2 Cl 2 and analyzed by 1 H NMR, signals similar to those of the 4,4′- t Bubpy ligands in 3a and 3b were observed along with a broad singlet at δ 4.07 assigned to a terminal methoxido moiety (Figure c). 51 V NMR (CD 2 Cl 2 ) spectrum of 2 also showed signals similar to those of 3a and 3b (see Figure S8).…”

Solvent‐free oxidation of straight‐chain aliphatic primary alcohols by polymer‐grafted vanadium complexes

“…The characteristic V═O stretching band of oxidovanadium(IV) complexes 1 – 3 appears at 1001, 978, and 997 cm −1 , respectively, [ 37,38 ] which is also present in the polymer‐grafted complexes 4–6 with slight shifting from the original position, confirming the presence of homogeneous complexes 1 – 3 in the polymer chain (shown in Figure 1).…”

Complexes Formed in Solution Between Vanadium(IV)/(V) and the Cyclic Dihydroxamic Acid Putrebactin or Linear Suberodihydroxamic Acid

“…The 51 V NMR spectrum from an approximately V(IV):pbH 2 = 1:1 solution at pH = 2 showed a signal at −443.3 ppm (Figure 6a), which was within the range for selected five- and six-coordinate V(V)–hydroxamato complexes at low pH values and also other V(V) complexes with O,O′ coordination, such as diols and α-hydroxycarboxylic acids. 65−69 There were no signals attributable to polyoxovanadate species ([HVO 4 ] 3– , −557 ppm; [V 2 O 7 ] 4– , −571 ppm; [V 4 O 12 ] 4– ,–577 ppm) in the spectrum(70) which suggested that the signal was attributable to [V V O(pb)] + or [V V O(OH)(pb)].…”