Stéréoch1mie en chimie minérale: Complexes moléculaires de l'oxo et du dioxo-vanad1um (V) avec le coordinat fluor et des molécules organiques

Abstract: While most high and medium oxidation state (O.S. ≥ 3) metal and non-metal fluorides and oxide fluorides are strong Lewis acids, exploration of their coordination chemistry with neutral ligands has been limited and mostly non-systematic. This is despite the very different properties conferred on the acceptor centre by the small electronegative fluoride ligands compared to the heavier halides. This article sets out these key differences, discusses possible synthetic routes, the key characterisation techniques, and appropriate bonding models. Current knowledge of the coordination chemistry of d, f and p-block fluorides and oxide fluorides with neutral ligands (with donor atoms drawn from Groups 15 and 16 and including N-heterocyclic carbenes) is then presented and discussed, and the differences in properties compared to complexes containing the heavier halides are illustrated. The emphasis is on work published post 1990, but earlier work is also included as essential background and where no more recent information exists. Attention is drawn to unexplored areas meriting investigation and to possible applications of these complexes.

Abstract: [VO2F(L–L)] (L–L = 2,2′-bipyridyl, 1,10-phenanthroline, Me2N(CH2)2NMe2) and [VO2F(py)2] (py = pyridine) have been prepared from the corresponding [VOF3(L–L)] or [VOF3(py)2] and O(SiMe3)2 in MeCN solution. VO2F (itself made from VOF3 and O(SiMe3)2 in MeCN) forms [Me4N][VO2F2] with [Me4N]F, but does not react with neutral N- or O-donor ligands. VO2Cl, prepared from VOCl3 and ozone, reacts with 2,2′-bipyridyl or 1,10-phenanthroline to form [VO2Cl(L–L)], with pyridine or pyridine-N-oxide (L) to produce [VO2Cl(L)2], and with OPPh3 or OAsPh3 (L′) gives [VO2Cl(L′)]. A second product from the OPPh3 system is the ionic [VO2(OPPh3)3][VO2Cl2] containing a trigonal bipyramidal cation. Neither VO2F nor VO2Cl form isolable complexes with MeCN, thf or MeO(CH2)2OMe, and both are reduced by P-, As-, S- or Se-donor ligands. [Ph4As][VO2X2] (X = F or Cl) react with 2,2′-bipyridyl to form [VO2X(2,2′-bipyridyl)], but similar reactions with weaker O-donor ligands fail. The complexes have been characterised by IR, multinuclear NMR (1H, 19F, 51V or 31P) and UV-visible spectroscopy. X-ray crystal structures are reported for [VO2F(py)2], [VO2Cl(L)2] (L = py or pyNO) and [VO2(OPPh3)3][VO2Cl2].

Abstract: [VOF3(MeCN)], obtained by dissolving VOF3 in dry acetonitrile, is a useful synthon for the preparation of complexes of the oxide-fluoride, and the reaction with 2,2-bipyridyl, 1,10-phenanthroline, Me2N(CH2)2NMe2 and Ph2P(O)CH2P(O)Ph2 (L-L), or Ph3PO, Me3PO, Ph3AsO, pyridine and pyridine N-oxide (L), produces the complexes [VOF3(L-L)] or [VOF3(L)2] respectively. These were characterised by microanalysis, IR, UV/Vis and multinuclear NMR [51V, 19F{1H}, 31P{1H}, 1H] spectroscopy, the data showing them to besix-coordinate with trans F-V-F units and the neutralligands trans to O and F, respectively. X-ray crystal structures of [VOF3(1,10-phenanthroline)], [VOF3(Ph3PO)2] and [VOF3(pyNO)2] confirm the geometry, although the first two exhibit O/F disorder trans to the neutral ligand. Unstable complexes with ether and thioether ligands including [VOF3{MeO(CH2)2OMe}], [VOF3{MeS(CH2)2SMe}] and [VOF3(15-crown-5)] are also described; these decompose rapidly even in the solid state, with fluorination of the ligands. The [VOF3(Ph3AsO)2] also decomposes in solutionto a mixture of products including Ph3AsF2 and [V6O12F4(Ph3AsO)2(Ph2AsO2)2] identified crystallographically. Comparisons with complexes of VOCl3 are also described.

Abstract: The first series of complexes of niobium(V) oxide trifluoride, [NbOF3(OPR3)2] (R = Me or Ph), [NbOF3(dppmO2)] (dppmO2 = Ph2P(O)CH2P(O)Ph2), [NbOF3(dmso)2], [NbOF3(tmeda)] (tmeda = Me2N(CH2)2NMe2) and [NbOF3(diimine)] (diimine = 2,2′-bipy, 1,10-phen) have been prepared, either by reaction of the corresponding complexes of NbF5 and hexamethyldisiloxane (HMDSO) in CH2Cl2–MeCN solution, or directly from NbF5, ligand and HMDSO. They were characterised by IR, 1H, 31P{1H} and 19F{1H} NMR spectroscopy, and X-ray crystal structures are reported for [NbOF3(OPR3)2] (R = Me or Ph) and [NbOF3(dppmO2)]. Complexes of NbOCl3, [NbOCl3(OPPh3)2], [NbOCl3(dppmO2)], [NbOCl3(dppeO2)] (dppeO2 = Ph2P(O)(CH2)2P(O)Ph2), [NbOCl3(tmeda)] and [NbOCl3(diimine)] were made from NbCl5 and HMDSO in MeCN (which forms [NbOCl3(MeCN)2] in situ), followed by addition of the neutral ligand. Their properties are compared with the oxide fluoride analogues. X-ray structures are reported for [NbOCl3(dppmO2)], [NbOCl3(dppeO2)], [NbOCl3(tmeda)] and [NbOCl3(2,2′-bipy)]. The synthesis and spectroscopic characterisation of [MF5L] (M = Nb or Ta; L = OPR3, OAsPh3) and [MF4(diimine)2][MF6] are also described, and the key properties of the four series of complexes compared.

Abstract: (NH4)2VO2F(C2O4) kristallisiert in der Raumgruppe P21/c mit 4 Formeleinheiten pro Elementarzelle und a = 11,362(2), b = 9,503(2), c = 7,190(1) A und β = 96,02(2)° Der R-Wert mit 1046 Reflexen betragt 0,038 Im komplexen Anion ist Vanadin verzerrt trigonal-bipyramidal von 2 Sauerstoffatomen, dem Fluoratom und dem Oxalation als zweizahnigem Liganden koordiniert Das Zentralatom, Fluor und die Oxalatgruppe liegen in einer Ebene Die sehr kurzen Abstande in der cis-Dioxogruppe betragen 1,617(4) bzw 1,614(4) A bei einem Winkel von 107,5(2)°, die V–O(Oxalat)-Abstande 2,016(4) und 2,031(4) A, der Vanadin-Fluor-Abstand 1,893(3) A Die Schwingungen νas bzw νsVO2 liegen bei 930 bzw 948 cm−1 Die weiteren Banden des Schwingungsspektrums werden ebenfalls zugeordnet Dioxofluorooxalatovanadate: a Monomeric, Fivefold Coordinated Complex Ion of Vanadium(V) (NH4)2VO2F(C2O4) crystallises in the space group P21/c with 4 formula units per unit cell and a = 11362(2), b = 9503(2), c = 7190(1) A und β = 9602(2)° 1046 reflection data were refined to R = 0038 In the complex anion vanadium is trigonal bipyramidally coordinated by two terminal oxygen atoms in cis position, fluorine and a bidentate oxalate ion The coordination polyhedron is highly distorted The very short bonds in the dioxo-group forming an angle of 1075° have lengths of 1617(4) and 1614(4) A The V—O (oxalate) distances are 2016(4) and 2031(4) A, the V—F distance is 1893(3) A The vibrations νas VO2 and νsVO2 are observed at 930 and 948 cm−1, respectively The remaining bands of the vibrational spectra are also assigned

Abstract: The infra-red spectra of various types of complexes of pyridine N-oxide with cobalt(II), nickel(II), zinc(II), aluminum(III), chromium(III), iron(II), iron(III) and tin(IV) were measured in the 3–15 μ region. All significant infra-red absorption bands of the spectra of the twenty-three investigated complexes have been assigned.

Abstract: Infrared spectra of pyridine N-oxide and its metal complexes of the type [M(pyridine N-oxide)6](ClO4)n (MMn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cr3+, Fe3+, Al3+, n = 2 or 3) were observed in the 2000–300 cm−1 region. The metal-ligand stretching and the N-O stretching vibration bands were respectively assigned below 450 cm−1 and at about 1200 cm−1. The CH out-of-plane vibration bands of the free and co-ordinated pyridine N-oxide, appearing in the region 1000–700 cm−1, were assigned by analysis of their combination bands. The frequencies of the metal-ligand stretching, of the N-O stretching and of the CH out-of-plane bending vibrations were found to be closely correlated. The CO stretching frequencies of 3- and 4-acetylpyridine N-oxide and of their metal complexes [M(acetylpyridine N-oxide)6](ClO4)n (MCo2+, Ni2+, Zn2+, Fe3+) were also obtained and are discussed.