Trigonal-bipyramidal vs. octahedral coordination in indium(III) complexes with potentially S,N,S‐tridentate thiosemicarbazones

Three bis‐chelates of indium(III) with (partially fluorinated) S,N,S‐tridentate thiosemicarbazones (H2L) were prepared and their structures were studied in solution and in the solid state by NMR, ESI MS and single‐crystal X‐ray diffraction. The three compounds are isostructural in solution with five‐coordinate InIII ions and two differently coordinated thiosemicarbazonato ligands, [In(L)(HL)]. A temperature‐dependent 1H NMR study reflects the presence of dynamic processes in the molecules such as the resolution of hindered rotation around CN bonds with partial double‐bond character and the pH‐triggered isomerization between 5‐ and 6‐coordinate species. The latter is confirmed by the isolation of compounds with different solid‐state structures, [In(L)(HL)] and [In(L)2]–, depending on fluorine‐substitutions in the periphery of the thiosemicarbazones

[ReH3(PPh3)4] - A Key Compound in the Rhenium Hydride Chemistry

The chemistry of the rhenium trihydrido complex [ReH3(PPh3)4] (1) has been reinvestigated. An improved synthesis and the solid-state structure of the compound as well as several reactions are reported. The solid-state structure of 1 is similar to that of [TcH3(PPh3)4] having a capped-octahedral coordination sphere. The PPh3 ligands surround the Tc atom in a trigonal-pyramidal mode with a short apical Re-P bond (2.300(2) Å) and three longer basal bonds (2.429(2)-2.449(2) Å). Reactions of 1 with monodentate phosphines such as PMe3 or PBu3 give the mono-substituted complexes [ReH3(PPh3)3(PMe3)] (2) and [ReH3(PPh3)3(PBu3)] (3) under retention of the apical PPh3 ligand and substitution of one of the basal PPh3 ligands. The stability of the phosphine trihydride complexes decreases in the order PPh3>PMe3>PBu3. Treatment of [ReH3(PPh3)4] with trityl hexafluorophosphate in CH3CN does not result in a hydride abstraction, but gives the tetrahydrido cation [ReH4(NCCH3)(PPh3)3]+ (4), while reactions with nitriles give unstable azavinylidene complexes of the composition [ReH2(PPh3)3(NC(H)R)] (5). They are formed by an insertion of the nitrile into a Re-H bond. The solid-state structure of the methyl derivative [ReH2(PPh3)3­(NC(H)CH3)] (5a) was determined showing a linear Re-N-C unit with rhenium-nitrogen and nitrogen-carbon double bonds, while the N=CH-C bond is clearly bent with an angle of 124°. Two previously unknown polymorphs of [ReH5(PPh3)3] were isolated from reactions of 1 with HOC6H3(CH3)2 and thiourea after prolonged heating in toluene and characterized by IR spectroscopy and X-ray diffraction

Tricarbonylrhenium(I) Complexes with Tridentate Schiff Bases

Potentially tridentate, phosphine-containing Schiff bases with P,N,O and P,N,P donor sets have been prepared from 2-(diphenylphosphino)benzaldehyde, salicylaldehyde, 2-aminophenol and 2-((diphenylphosphino)phenyl)methylamine and reacted with (NEt4)(2)[Re(CO)(3)Br-3] in methanol. Deprotonation and the formation of neutral [Re(CO)(3)(L)] complexes with tridentate coordination of the Schiff bases has been obtained for the salicylidene derivatives, while the potential P,N,P ligand L-3 forms [Re(CO)(3)Br(L-3)] with the Schiff base in a bidentate bonding mode. The formation of a cationic [Re(CO)(3)(L-3)](+) complex with tripodal coordination of the organic ligand could be achieved by the addition of Ag(PF6) to the reaction mixture. The obtained rhenium(I) complexes were studied spectroscopically and by X-ray diffraction

Application of technetium and rhenium carbonyl chemistry to nuclear medicine. Preparation of [NEt4]2[TcCl3(CO)3] from [NBu4][TcO4] and structure of [NEt4][Tc2(μ-Cl)3(CO)6]; structures of the model complexes [NEt4][Re2(μ-OEt)2(μ-OAc)(CO)6] and [ReBr({-CH2S(CH2)2Cl}2)(CO)3]

A detailed investigation of the one-pot synthesis of [NEt4]2[MX3(CO)3] [M=Tc (1a) or Re (1b); X= Cl−, Br−] is presented. The intermediates [NEt4][Tc2-(μ-Cl)3(CO)6] (2a), [NBu4][Tc3(μ3-H)(μ-H)3(CO)9] (3) and [Tc3(μ-H)3(CO)12] (4) have been isolated and characterized. The X-ray structure of (2a) is described. Complex (2a) crystallizes in the monoclinic space group P21/c with a=19.491(6), b=18.323(2) and c=17.497(9)AÅ, and β=97.59(2)°. Quantitative conversion of (2a), (3) and (4) into the aqua-ion [M(OH2)3(CO)3]+ [M=Tc (5a) or Re (5b)] is described. To evaluate an optimal and simple chelating group for the "fac-M(CO)3” moiety, the reaction with the bidentate thioether ligand Cl(CH2)2S(CH2)2S(CH2)2Cl (qyp) has been investigated and the structure of the neutral complex [ReBr(qyp)(CO)3] (6) is described. Complex (6) crystallizes in the monoclinic space group P21/c with a=15.935(6), b=2.788(4) and c= 7.955(10)AÅ, and β=98.57(1)°. To extend the knowledge about substitution chemistry of organometallic complexes in aqueous solution, the acetato ligand [OOCCH3]− has been reacted with (1b), resulting in the formation of the dinuclear, acetato-bridged complex [NEt4][Re2(μ-OH)2(μ-OAc)(CO)6], which converted into [Re2(μ-OEt)2(μ-OAc)(CO)6]− (7) after recrystallization from EtOH. The X-ray structure of (7) has been determined. Complex (7) crystallizes in the monoclinic space group P21/c with a=16.288(3), b=12.4272(10) and c=13.620(3)AÅ, and β=76.63(1)°. For a future application of the small "fac-M(CO)3” moiety, it seems thus advantageous to combine these two ligand groups in one simple chelating functio

Tricarbonylrhenium(I) and ‐technetium(I) Complexes with Tris(1,2,3‐triazolyl)phosphine Oxides

Two potentially tripodal ligands, tris(1-phenyl-1H-1,2,3-triazol-4-yl)phosphine oxide (OP((1,2,3)Tz(1-Ph))(3)) and tris(1-benzyl-1H-1,2,3-triazol-4-yl)phosphine oxide (OP((1,2,3)Tz(1-benz))(3)), were used in reactions with [Re(CO)(5)Br] and (NEt4)(2)[Tc(CO)(3)Cl-3]. While the formation of rhenium complexes with bidentate and tridentate coordinated phosphine oxides was observed, for technetium only cationic complexes with tripodal coordinated OP((1,2,3)Tz(1-R)) ligands were isolated. The products have been characterized spectroscopically and by single crystal X-ray diffraction

Na[Tc(CO)(CNp-F-ArDArF2)4]: an isocyanide analogue of the elusive Na[Tc(CO)5]

The first crystalline technetium complex in a negative oxidation state, [Tc−I(CO)(CNp-F-ArDArF2)4]−, was isolated and structurally characterized as its [Na(Crypt-2.2.2)]+ salt. It mirrors the properties of the textbook organometallic compound Na[Tc(CO)5], which has eluded isolation and structural characterization until today. [Na(Crypt-2.2.2)][Tc−I(CO)(CNp-F-ArDArF2)4] reacts expectedly as a nucleophile, which is demonstrated by reactions with HCl and ClSnMe3. They give the unprecedented monohydrido and trimethylstannyl complexes of technetium

Thionitrosyl Complexes of Rhenium and Technetium with PPh3 and Chelating Ligands - Synthesis and Reactivity

In contrast to corresponding nitrosyl compounds, thionitrosyl complexes of rhenium and technetium are rare. Synthetic access to the thionitrosyl core is possible by two main approaches: (i) the treatment of corresponding nitrido complexes with S2Cl2 and (ii) by reaction of halide complexes with trithiazyl chloride. The first synthetic route was applied for the synthesis of novel rhenium and technetium thionitrosyls with the metals in their oxidation states “+1” and “+2”. [MVNCl2(PPh3)2], [MVNCl(PPh3)(LOMe)] and [MVINCl2(LOMe)] (M = Re, Tc; {LOMe}− = (η5-cyclopentadienyl)tris(dimethyl phosphito-P)cobaltate(III)) complexes have been used as starting materials for the synthesis of [ReII(NS)Cl3(PPh3)2] (1), [ReII(NS)Cl3(PPh3)(OPPh3)] (2), [ReII(NS)Cl(PPh3)(LOMe)]+ (4a), [ReII(NS)Cl2(LOMe)] (5a), [TcII(NS)Cl(PPh3)(LOMe)]+ (4b) and [TcII(NS)Cl2(LOMe)] (5b). The triphenylphosphine complex 1 is partially suitable as a precursor for ongoing ligand exchange reactions and has been used for the synthesis of [ReI(NS)(PPh3)(Et2btu)2] (3a) (HEt2btu = N,N-diethyl-N′-benzoyl thiourea) containing two chelating benzoyl thioureato ligands. The novel compounds have been isolated in crystalline form and studied by X-ray diffraction and spectroscopic methods including IR, NMR and EPR spectroscopy and (where possible) mass spectrometry. A comparison of structurally related rhenium and technetium complexes allows for conclusions about similarities and differences in stability, reaction kinetics and redox behavior between these 4d and 5d transition metals

Rhenium(V) complexes with selenolato‐ and tellurolato‐substituted Schiff bases – Released PPh3 as a facile reductant

The salicylidene Schiff bases of bis(2‐aminophenyl)diselenide and ‐ditelluride react with [ReOCl3(PPh3)2] or the arylimidorhenium(V) compounds [Re(NPhR)Cl3(PPh3)2] (R = H, F, CF3) with formation of rhenium(V) complexes with tridentate {O,N,Se/Te} chalcogenolato ligands. The ligands adopt a facial coordination mode with the oxygen donors trans to the multiply bonded O2– or NPhR2– ligands. The reduction of the dichalcogenides and the formation of the chalcogenolato ligands occurs in situ by released PPh3 ligands. The absence of additional reducing agents provides good yields of products with rhenium in the high formal oxidation state “+5”. A mechanism for the dichalcogenide reduction is proposed on the basis of the experimental results. In accordance with the proposed mechanism, best yields are obtained with a strict exclusion of oxygen, but in the presence of water

[{TcI(NO)(LOMe)(PPh3)Cl}2Ag](PF6) and [TcII(NO)(LOMe)(PPh3)Cl](PF6): Two Unusual Technetium Complexes with a “Kläui-type” Ligand

The reaction of [TcI(NO)(LOMe)(PPh3)Cl] ({LOMe}−=η5-cyclopentadienyltris(dimethyl phosphito-P)cobaltate(III)) with Ag(PF6) gives two unexpected products: the dimeric technetium(I) complex [{Tc(NO)(LOMe)(PPh3)Cl}2Ag](PF6) with a central Ag+ ion and the cationic Tc(II) compound [Tc(NO)(LOMe)(PPh3)Cl](PF6). The products have been studied spectroscopically and by X-ray diffraction