- Chelated hydrazido(3-)rhenium(V) complexes: On the way to the nitrido-M(V) core (M = Tc, Re)
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Neutral and asymmetrical hydrazido(3-)rhenium(V) heterocomplexes of the type [Re(η2-L4)(Ln)(PPh3)] (η2-L4 = NNC(SCH3)S; H2L1 = S-methyl β-N-((2-hydroxyphenyl)ethylidene)dithiocarbazate, 1, H2L2 = S-methyl β-N-((2-hydroxyphenyl)methylidene)dithiocarbazate, 2) are prepared via ligand-exchange reactions in ethanolic solutions starting from [ReV(O)Cl4]- in the presence of PPh3 or from [ReV(O)Cl3(PPh3)2]. The distorted octahedral coordination sphere of these compounds is saturated by a chelated hydrazido group, a facially ligated ONS Schiff base, and PPh3. Reduction-substitution reactions starting from [NH4][ReVIIO4] in acidic ethanolic mixtures containing PPh3 and H2Ln (or its dithiocarbazic acid precursor H3L4) produce another example of chelated hydrazido(3-) rhenium(V) derivative, namely [Re(η2-L4)Cl2(PPh3) 2], 3. On the contrary, the N-methyl-substituted dithiocarbazic acid H2L3 reacts with perrhenate to give the known nitrido complex [Re(N)Cl2(PPh3)2]. Rhenium(V) complexes incorporating the robust η2-hydrazido moiety represent key intermediates helpful for the comprehension of the reaction pathway which generates nitridorhenium(V) species starting from oxo precursors. An essential requirement for the stabilization of such chelated hydrazido-Re(V) units is the triple deprotonation at the hydrazine nitrogens, thereby providing efficient π-electron circulation in the resulting five-membered ring. The thermal stability of these units is affected by the nature of the anchoring donor, thione sulfur ensuring stronger chelation than nitrogen and oxygen. The η2-hydrazido complexes are characterized by conventional physicochemical techniques, including the X-ray crystal structure determination of 1 and 3.
- Mevellec, Franck,Lepareur, Nicolas,Roucoux, Alain,Noiret, Nicolas,Patin, Henri,Bandoli, Giuliano,Porchia, Marina,Tisato, Francesco
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- Rhenium(V) and technetium(V) complexes with phosphoraneimine and phosphoraneiminato ligands
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Air-stable rhenium(V) nitrido complexes are formed when [ReOCl 3(PPh3)2], [NBu4][ReOCl 4], or [NBu4][ReNCl4] are treated with an excess of silylated phosphoraneiminates of the composition Me 3SiNPPh3 or Ph2P(NSiMe3)CH 2PPh2 in CH2Cl2. Complexes of the compositions [ReNCl(Ph2PCH2PPh2NH) 2]Cl (1), [ReN(OSiMe3)(Ph2PCH 2PPh2NH)2]Cl (2) or [ReNCl2(PPh 3)2] (3) were isolated and structurally characterized. The latter compound was also produced during a reaction of the rhenium(III) precursor [ReCl3(PPh3)2(CH3CN) and Me3SiNPPh3. Nitrogen transfer from the phosphorus to the rhenium atoms and the formation of nitrido ligands were observed in all examples. All products of reactions with an excess of the potentially chelating phosphoraneiminate Me3SiNP(Ph2)CH2PPh 2 contain neutral Ph2PCH2PPh2NH ligands. The required protons are supplied by a metal-induced decomposition of the solvent dichloromethane. The Re-N(imine) bond lengths (2.055-2.110 A) indicate single bonds, whereas the N-P bond with lengths between 1.596 A and 1.611 A reflect considerable double bond character. An oxorhenium(V) phosphoraneiminato complex, the dimeric compound [ReOCl2(μ-N- Ph2PCH2PPh2N)]2 (4), is formed during the reaction of [NBu4][ReOCl4] with an equivalent amount of Ph2P(NSiMe3)CH2PPh2 in dry acetonitrile. The blue neutral complex with two bridging phosphoraneiminato units is stable as a solid and in dry solvents. It decomposes in solution, when traces of water are present. The rhenium-nitrogen distances of 2.028(3) and 2.082(3) A are in the typical range of bridging phosphoraneiminates and an almost symmetric bonding mode. Technetium complexes with phosphoraneimine ligands were isolated from reactions of [NBu4][TcOCl4] with Me3SiNPPh3, and [NBu4][TcNCl4] with Me3SiNP(Ph2)CH2PPh2. Nitrogen transfer and the formation of a five-coordinate nitrido species, [TcNCl 2(HNPPh3)2] (5), was observed in the case of the oxo precursor, whereas reduction of the technetium(VI) starting material and the formation of the neutral technetium(V) complex [TcNCl2(Ph 2PCH2PPh2NH)] (6) or [TcNCl(Ph 2PCH2PPh2NH)2]Cl (7) was observed in the latter case. Both technetium complexes are air stable and X-ray structure determinations show bonding modes of the phosphoraneimines similar to those in the rhenium complexes.
- Hecht, Maren,Anaya, Sonia Saucedo,Hagenbach, Adelheid,Abram, Ulrich
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p. 3172 - 3180
(2008/10/09)
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- Solid state study on rhenium dimethylphosphinoethane complexes: X-ray crystal structures of trans-[ReO2 (dmpe)2]PF 6·2H2O, trans-[ReO(OH)(dmpe)2](CF 3SO3)2, trans-[ReN(Cl)(dmpe) 2]CF3SO3 and trans-[ReCl2(dmpe) 2]ReO4
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The reaction of trans-[ReO2(en)2]Cl with dimethylphosphinoethane (dmpe) yielded the yellow complex trans-[ReO2 (dmpe)2]Cl (1), which, upon reaction with CF3SO 3H, yields orange crystals of the oxo-hydroxo complex trans-[ReO (OH)(dmpe)2](CF3SO3)2 (2). Reaction of trans-[ReNCl2(PPh3)2] with dmpe resulted in orange crystals of trans-[ReN(Cl)(dmpe)2]-CF3SO 3 (3). Adjustment of the pH of a solution of trans-[ReN(Cl)(dmpe) 2]CF3SO3 to 11.7 with NaOH resulted in the formation of yellow crystals of trans-[ReCl2(dmpe) 2]ReO4 (4). A shortening of the Re-P bond distances were observed as the axial ligands (i.e., core: O=ReV-OH V=O V-Cl III-Cl) increased the electron density on the metal center, allowing for better Re-P π back bonding. The preliminary pKa determination for the protonation of [ReO2(dmpe)2]+ to form [ReO(OH)(dmpe)2]2+ showed the pKa2 to be 2(dmpe)2]+: monoclinic space group P21/c with a = 11.5299(7) A, b = 15.2397(9) A, c = 15.0230(9) A, β = 97.7260(10)°, Z = 4; trans-[ReO(OH)(dmpe)2]2+: monoclinic space group P2 1/c with a = 8.0426(4) A, b = 11.5472(6) A, c = 16.0303(8) A, β = 101.9360(10)°, Z = 2; trans-[ReN(Cl) (dmpe)2]+: orthorhombic space group Pmc21 with a = 11.5068(10) A, b = 9.6656(8) A, c = 12.1772(11) A, Z = 2; trans-[Re(Cl)2(dmpe)2]+: monoclinic space group P21/c with a = 19.375(3) A, b = 8.6840(12) A, c = 15.910(2) A, β = 111.270(3)°, Z = 4. The conformation of the two dmpe ligands in all of the complexes described were λδ (eclipsed). Copyright
- Engelbrecht,Jurisson,Cutler,Den Drijver,Roodt
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- [NBu4][ReNCl4]: Facile synthesis, structure, electron paramagnetic resonance spectroscopy and reactions
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The compound [NBu4][ReNCl4] has been found to be easily accessible by the reaction of [NBu4][ReO4] with sodium azide and HCl gas in ethanol and represents an excellent precursor for the synthesis of further rhenium nitrido complexes. It has been studied by X-ray crystallography. Rhenium(VI) compounds of the general formula [ReNX4(5)]-,2- (X = Br or NCS) were obtained when [NBu4][ReNCl4] reacts with HBr or KSCN. The products as well as mixed-ligand intermediates which are formed during the ligand exchange have been studied by EPR spectroscopy. The EPR parameters of the individual mixed-ligand compounds are clearly correlated to the composition of the co-ordination sphere and can be used to characterize the mixed-ligand species unambiguously. This is shown by a nearly linear dependence of g0, g∥, a0Re and A∥Re on the spin-orbit coupling constants of the equatorial donors. Reactions of [NBu4][ReNCl4] with most organic ligands yielded rhenium(V) compounds. A number of phosphine complexes and chelates with sulfur-containing ligands have been prepared and spectroscopically characterized. A crystallographic study on [ReN(Hdetcb)2] (Hdetcb- = N2-diethylthiocarbamoylbenzamidinate) shows cis co-ordination for the chelating S,N-donor ligands. Weak intermolecular hydrogen bridges have been found between the co-ordinated nitrogen atoms and the lone pair of the nitrido nitrogen. A comparison between the crystal structural data of [NBu4]2[ReN(mnt)2] (mnt2- = 1,2-dicyanoethene-1,2-dithiolate), prepared from [NBu4][ReNCl4] and Na2mnt, and [NBu4][ReO(mnt)2] shows longer Re-S bonds in the nitrido anion but markedly higher O-Re-S bond angles indicating higher steric requirements of the oxo ligand compared with 'N3-'.
- Abram, Ulrich,Braun, Martin,Abram, Sonja,Kirmse, Reinhard,Voigt, Andreas
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p. 231 - 238
(2007/10/03)
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- Co-ordination chemistry of S-methyl 2-methyldithiocarbazate and formation of [M≡N]2+(M = Tc or Re) species
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Reaction of [TcOCl4]- and [ReOCl3(PPh3)2] with S-methyl 2-methyldithiocarbazate [H2L = H2NNMeC(S)SMe] under mild conditions gave the oxo-technetium(V) and -rhenium(V) S,N-chelated complexes [MO(HL)2]Cl (M = Tc or Re). These were transformed to the corresponding nitrido-complexes [MNCl2(PPh3)2] under reflux and in the presence of HCl and PPh3. The technetium(IV) complex [TcCl4(PPh3)2] under reflux and in presence of an excess of H2L and NEt3 gave the nitrido-compound [TcN(HL)2]. This was also obtained when [TcNCl2(PPh3)2] was used as precursor in the presence of NEt3. The complex [TcNCl2{NPr(CH2CH2PPh2) 2}] reacted with an excess of H2L to give the monosubstituted compound [TcN(HL){NPr(CH2CH2PPh2)2}]X (X = Cl, BF4 or BPh4). A crystal structure determination of the complex [ReO(HL)2]Cl showed a distorted square-pyramidal geometry with the oxygen atom in apical position. The Cl- ion is bound to NH groups by means of two hydrogen bonds. A set of reactions using 99mTc were carried out in order to understand the formation of the 99mTcN core.
- Marchi, Andrea,Uccelli, Licia,Marvelli, Lorenza,Rossi, Roberto,Giganti, Melchiore,Bertolasi, Valerio,Ferretti, Valeria
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p. 3105 - 3109
(2007/10/03)
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- Stereoisomerism of oxotrichlorobis(triphenylphosphine)rhenium(V), ReOCl3(PPh3)2: a reinvestigation
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The various preparative procedures described in the literature for ReOCl3(PPh3)2 were repeated.The standard methods were found to yield a yellow triclinic material (P1, a = 11.793, b = 14.300, c = 16.422 Angstroem, α = 64.04 deg, β = 84.31 deg, γ = 87.32 deg, R = 0.064).The unit cell contains three discrete monomeric molecules with the trans-bis(phosphine) configuration, one of which has its Cl-Re=O unit disordered over two opposite directions.Recrystallization in CH2Cl2 yielded crystals of the bright green monoclinic polymorph (C2/c, a = 24.347, b = 9.604, c = 15.666 Angstroem, β = 116.77 deg, R = 0.025) containing the same monomeric molecule, but with a different conformation of the PPh3 ligands and a different packing pattern.These two polymorphs actually correspond to 'isomers' 1 and 2 described by Johnson, Lock, and Wilkinson in l964.Attempts to prepare their third 'isomer' yielded powders containing ReOCl3(PPh3)2 (green polymorph) and ReNCl2(PPh3)2.The IR and (31)P NMR spectra of these samples are discussed.
- Lebuis, Anne-Marie,Beauchamp, Andre L.
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p. 441 - 449
(2007/10/02)
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