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  • Author: Fritz Preuss x
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Abstract

Syntheses of oxovanadium(V) thiolates such as O = V(SR)3 (R = tC4H9 , SiPh3 ) and O=V(OtC4H9 )n(StC4H9)3-n(n = 1, 2) are described. The thiovanadium(V) compounds S=V(OtC4H9 )3 , S = V(StC4H9)(OtC4H9) 2 and S=V(SSiPh3)3 have been prepared by various methods :substition using Lawesson reagent, oxidation of V(OtC4H9)4 by sulfur, or disproportionation reaction of VCl4 with LiSSiPh3 ; O = V (OSiR3)3 (R = Me , Ph) undergoes a reaction with Lawesson reagent to yield dithiophosphonate complexes. All compounds obtained are characterized by 1H and 51V NMR spectroscopy; the stability of thiovanadium(V) compounds is discussed. V(StC4H9)4 has been synthesized as a first example of vanadium(IV) thiolates

The compounds tC4H9N=VR(OtC4H9)2 (R = CH3, nC4H9, CH2SiMe3, Mes) and tC4H9N = VMes2(OtC4H9) have been prepared by reaction of tert-butyliminovanadium (V) chlorides with LiR; tC4H9N=V(CH2SiMe3)2(OtC4H9) and tC4H9N=VR3 (R = CH2SiMe3, Mes) could only be characterized by NMR spectroscopy. The 1H, 13C and 51V NMR spectra are discussed; the constants of 51V , 14N coupling have been determined.

Abstract

Tris-tert-butylorthovanadate VO(OC4H9)3 undergoes reaction with monocarboxylic acids to yield monomeric VO(OC4H9)(RCOO)2; no VO(OC4H9)2(RCOO) or VO(RCOO)3 could be isolated from the reaction mixture. Polymeric dioxovanadium(V)-monocarbox-ylates(VO2RCOO)n are formed by thermolysis or partial hydrolysis of VO(OC4H9)(RCOO)2; the reaction mechanism is studied and discussed. Syntheses of Ba[VO2(CH3COO)3], Ba[VO2(C2H5COO)3] and N(C4H9)4[V4O8Br(CH3COO)4] are described. All compounds obtained are characterized by IR and 1H NMR spectroscopy as well as by chemical reactions. The carboxyl groups are mostly acting as bidentate ligands.

Abstract

1C4H9N = V(OSiMe3)3 has been prepared by reaction of NH4VO3 with HNSiMe3(tC4H9). This compound is the starting material for the synthesis of C6H5N = V(OSiMe3)3 and tG4H9N = VCl3 by transamination with aniline or redistribution with VOCl3, respectively. The properties of the trichloride are studied by chemical reactions such as redistribution, complex formation and substitution with silver carboxylates. All compounds are mono-meric in solution, probably containing a nitrogen vanadium triple bond. The structure of 2,2'-dipyridyl complexes [tC4H9N = VX3 · C10H8N2] (X = Cl, CH3COO) has been found to be octahedral with meridional arrangement of chloride or acetate ligands.

The compounds Li[nC4H9VO(OtC4H9)3], Me3SiCH2V(OtC4H9)3, (CH3)2V(OSiMe3)2 and V(OtC4H9)4 have been prepared by reaction of esters VO(OR)3(R = tC4H9, SiMe3) with lithium alkyls. RVO(OtC4H9)2 species are not formed by direct alkylation of VO(OtC4H9)3 with LiR; albeit in small yields, these compounds (R = CH3, CH2SiMe3) can be synthesized however from VO(OtC4H9)2Cl. The 51V, 1H and 13C NMR spectra of the vanadium(V) and vanadium(IV) compounds are discussed; the constants of 51V, 1H and 51V, 13C coupling have been determined.

Yellow phosphatovanadates M2O · V2O5 · P2O5 · H2O (M = K, Rb, Cs, NH4), 2 K2O · V2O5 · P2O5 and M2O · 2 V2O5 · P2O5 · aq (M = K, Rb, NH4) are prepared; their properties studied by chemical reactions, 1H NMR and IR spectroscopy indicate a polymeric constitution of these compounds. No polyphosphatovanadic acid can be isolated; condensation reactions in highly acidified sodium metavanadate solutions, containing an excess of sodium dihydrogenphosphate, yield polymeric oxide hydrate VPO5 · 2 H2O.

Deep red heteropolyvanadates of phosphorus(V) n M2O:P2O5: 13 V2O5 · aq (n = 3, 5, 6; M = Na, K, Rb, Cs, NH4) and n M2O: P2O5: 14 V2O5 · aq (n = 4, 7; M = K, Rb, Cs, NH4, (n-C4H9)4N) were prepared. Recrystallization of 1: 13- and 1: 14-heteropolyvanadates and determination of molecular weight by ultracentrifuge technique in solutions from V2O5 and NaH2PO4 indicate 1: 14-heteropolyvanadate ions to be stable species over a wide range of pH, while 1: 13-heteropolyvanadate ions are only stabilized in higher acidified solutions containing H2PO4 - or as slightly soluble salts. Wide line 1H NMR spectra are interpreted in terms of OH groups and H2O of cristallization, the isolated heteropolyvanadates of both series consisting of protonated anions; the basicity of heteropolyvanadic acids of phosphorus(V) is unknown.

Abstract

The cyclopentadienyl compounds tC4R9N = VCpCl2 (2). tC4H9N = VCp(OtC4H9)Cl, tC4H9N = VCp(OtC4H9)(R) (R = CH3, "C4H9, CH2SiMe3), tC4H9N = VCp2(OtC4H9) (5) and ,tC4H9N = VCp(OtC4H9)2 have been prepared starting from tC4H9N = VCl3 1H and 51V NMR spectra are discussed; except for 5, the C5H5 rings are η5-coordinated to the metal atom. The temperature dependence of the 1H NMR spectrum of 5 indicates two types o f intramolecular rearrangements: η15-Interchange of the C5H5 rings and fluxional behavior of the η1-C5H5 ring. The molecular structure of 2 has been investigated by X-ray diffraction analysis.

The complexes ′C4H9N = V(O′C4H9)3-n[SSi(O′C4H9)3]n, O = V(O′C4H9)3-n[SSi(O′C4H9)3]n, O=V[SSi(O′C4H9)3]2 (9) and VCl[SSi(O′C4H9)3]2 have been prepared by reaction of chlorovanadium compounds with LiSSi(O′C4H9)3. All complexes are characterized by NMR (1H, 51V) and ESR spectroscopy. 9 has been found by X-ray diffraction analysis to be a distorted trigonal bipyramidal complex with bidentate thiolate ligands.

The cyclopentadienyl compounds tC4C4H9N=VCp(NHtC4C4H9)Cl, tC4C4H9N=VCp[N(SiMe3)2]Cl, tC4C4H9N=VCp(NHtC4C4H9)(R) (R = CH3, ⁿC4H9, 5C4H9, tC4H9, CH2SiMe3), Li[(tC41H9N)2VCp(CH3)]-OEt2, tC4H9N=VCp2(NHtC4H9) and tC4H9N=VCp(CH3)2 have been prepared starting from tC4H9N = V CpCl2. All compounds obtained are characterized by 1H and 51V NMR spectroscopy; the stability of monoalkylvanadium(V) complexes is discussed.