Rhenium(I) and Technetium(I) Tricarbonyl Complexes with Phosphoraneimines

[NEt₄]₂[Re(CO)₃Br₃] and [NEt₄]₂[Tc(CO)₃Cl₃] react with trimethylsilyltriphenylphosphoraneimine, Me₃SiNPPh₃, under exchange of the bromo ligands and the formation of cationic [M(CO)₃(HNPPh₃)₃]⁺ complexes (M = Re, Tc). The required protons are abstracted from the solvent CH₂Cl₂. The steric bulk of the organic ligands causes a marked distortion of the established coordination polyhedra from an idealized octahedron with bond angles between neighbouring donor atoms between 81.81(8)° and 96.66(8)°. The reaction of [NEt₄]₂[Re(CO)₃Br₃] with Me₃SiNP(Ph₂)CH₂PPh₂ in CH₂Cl₂ yields the neutral complex [Re(CO)₃Br{HNP(Ph₂)CH₂PPh₂)], which contains a neutral, chelate‐bonded (diphenylphosphinomethyl)diphenylphosphoraneimine ligand. A similar reaction with the bifunctional phosphoraneimine Me₃SiNP(Ph₂)CH₂(Ph₂)PNSiMe₃ gives only small amounts of a binuclear rhenium(I) complex of the composition [{Re(CO)₃Br₂}₂(HNP(Ph₂)CH₂(Ph₂)PNH)]^2‐, whereas the major amount of the bis‐phosphoraneimine undergoes an intramolecular rearrangement to yield [H₂NP(Ph₂)NP(Ph₂)CH₃]Br. An X‐ray structure analysis shows a widespread delocalization of electron density over the central part of the cation.     

Dimeric Rhenium(I) Carbonyl Complexes with Thiosemicarbazone Backbone

Dimeric, neutral rhenium(I) complexes of the composition [Re₂(CO)₆X(L^R)] (X = Cl or Br) are formed when [NEt₄]₂[Re(CO)₃Br₃] or [Re(CO)₃Cl(CH₃CN)₂] react with 2, 2′-dipyridylketone thiosemicarbazones (HL^R, R = H, Ph). The thiosemicarbazones deprotonate during the reaction and connect two tricarbonylrhenium(I) units as formally pentadentate bridging ligands. This results in an extremely rare coordination mode, in which the two nitrogen atoms of the hydrazone unit bind to each one of the rhenium atoms. The bond lengths inside the thiosemicarbazonato backbone reflect a large degree of delocalization of electron density.     

Tricarbonyl complexes of rhenium(I) and technetium(I) with thiourea derivatives

fac-[M(CO)₃X₃]²⁻ complexes (M=Re, X=Br; M=Tc, X=Cl) react with thiourea derivatives under formation of stable rhenium(I) and technetium(I) complexes. The composition of the products can be controlled by the steric requirements of the ligands and their ability to form chelates.The products of reactions with tetramethylthiourea, Me₄tu (I), N,N-diethylthiocarbamoylbenzamidine, H₂Et₂tcb (II), and morpholinylthiocarbamoylbenzamidine, H₂morphtcb (III), have been studied by X-ray crystallography showing that the products belong to three different structural types. A mononuclear complex of the composition fac-[Re(CO)₃Br(Me₄tu)₂] has been isolated with tetramethylthiourea, whereas the thiocarbamoylbenzamidines deprotonate and act as N,S-chelating ligands. This results in the formation of a dimeric [Tc(CO)₃(HEt₂tcb-N,S)]₂ complex with a central, almost square Tc₂S₂ unit and a monomeric compound of the composition [Tc(CO)₃(Hmorphtcb-N,S)(H₂morphtcb-S)]. The latter compound contains a neutral, S-bonded morpholinylthiocarbamoylbenzamidine in the unusual imine form in addition to a chelate-bonded Hmorphtcb⁻ ligand.     

Rhenium Complexes with p-Fluorophenylisocyanide

p-Fluorophenylisocyanide (CNPh^pF) reacts with [Re(CO)₅Br] under stepwise exchange of the carbonyl ligands depending on the conditions applied. The reaction stops with the formation of fac-[Re(CO)₃Br(CNPh^pF)₂] in boiling THF. An ongoing carbonyl exchange is observed at higher temperatures, e. g. in refluxing toluene, with the final formation of the [Re(CNPh^pF)₆]⁺ cation. The progress of the reactions has been studied by ¹⁹F NMR spectroscopy and the structures of [Re(CO)Br(CNPh^pF)₄] and [Re(CNPh^pF)₆](BPh₄) have been elucidated by X-ray diffraction.     

Phenylimido Complexes of Technetium and Rhenium with Maleonitriledithiolate

[Tc(NPh)Cl₃(PPh₃)₂] or [Re(NPh)Cl₃(PPh₃)₂] react with two equivalents of Na₂mnt (mnt^2– = 1,2‐dicyanoethene‐1,2‐dithiolate) with formation of anionic complexes of the composition [M(NPh)(mnt)₂]^–. The products can be isolated as large red blocks of their AsPh₄⁺ salts. The complex anions contain square‐pyramidal coordinated metal atoms with the phenylimido ligands in apical positions. The M–N–C bonds are almost linear. A similar phenylimido complex with an additional amino group was synthesized from [Re(NC₆H₄‐4‐NH₂)Cl₃(PPh₃)₂]. The presence of such substituents may allow coupling of the metal complexes to biomolecules such as peptides, proteins, or sugars, provided the M=N bonds are sufficiently stable against hydrolysis.     

Dioxouranium Complexes with Acetylpyridine Benzoylhydrazones and Related Ligands

Acetylpyridine benzoylhydrazone and related ligands react with common dioxouranium(VI) compounds such as uranyl nitrate or [NBu₄]₂[UO₂Cl₄] to form air‐stable complexes. Reactions with 2, 6‐diacetylpyridinebis(benzoylhydrazone) (H₂L^1a) or 2, 6‐diacetylpyridinebis(salicylhydrazone) (H₂L^1b) give yellow products of the composition [UO₂(L¹)]. The neutral compounds contain doubly deprotonated ligands and possess a distorted pentagonal‐bipyramidal structure. The hydroxo groups of the salicylhydrazonato ligand do not contribute to the complexation of the metal. The equatorial coordination spheres of the complexes can be extended by the addition of a monodentate ligand such as pyridine or DMSO. The uranium atoms in the resulting deep‐red complexes have hexagonal‐bipyramidal coordination environments with the oxo ligands in axial positions. The sterical strains inside the hexagonal plane can be reduced when two tridentate benzoylhydrazonato ligands are used instead of the pentadentate 2, 6‐diacetylpyridine derivatives. Acetylpyridine benzoylhydrazone (HL²) and bis(2‐pyridyl)ketone benzoylhydrazone (HL³) deprotonate and form neutral, red [UO₂(L)₂] complexes. The equatorial coordination spheres of these complexes are puckered hexagons. X‐ray diffraction studies on [UO₂(L^1a)(pyridine)], [UO₂(L^1b)(DMSO)], [UO₂(L²)₂] and [UO₂(L³)₂] show relatively short U—O bonds to the benzoylic oxygen atoms between 2.328(6) and 2.389(8) Å. This suggests a preference of these donor sites of the ligands over their imino and amine functionalities (U—N bond lengths: 2.588(7)—2.701(6) Å ).     

Rhenium(I) and technetium-99m(I) fac-tricarbonyl complexes with 4-(imidazolin-2-yl)-3-thiabutanoic acid derivatives as tridentate ligands: Synthesis and structural characterization

Two rhenium(I) tricarbonyl complexes, with the monoanionic tridentate NSO type ligand, 4-(imidazolin-2-yl)-3-thiabutanoic acid and 4-(N-ethylimidazolin-2-yl)-3-thiabutanoic acid were synthesized and isolated in pure form. Both complexes were characterized by spectroscopic methods and elemental analysis. The solid-state structure of 4-(imidazolin-2-yl)-3-thiabutanoic acid and of both complexes was established by X-ray crystallography. The geometry about the rhenium is octahedral. The analogous technetium-99m complexes were also prepared quantitatively by the reaction of both ligands with the fac-[^99mTc(CO)₃(H₂O)₃]⁺ synthon and their identity was established by chromatographic comparison to their rhenium congeners.     

Rhenium(V) Complexes with Bidentate N,O-Donor Imidazole Derivatives

The reaction of a two-fold molar excess of the potential N,O-donor ligand 2-(hydroxymethyl)-1-methylimidazole (Hmi) with trans-[ReOCl₃(PPh₃)₂] led to the isolation of cis-[ReOCl₂(mi)(PPh₃)]. An X-ray structure determination indicated that the complex has distorted octahedral geometry, and that mi coordinates as a bidentate with the alcoholate oxygen trans to the oxo group. A similar reaction with 2-(1-ethyloxomethyl)-1-methylimidazole (eomi), the ethyl substituted analogue of Hmi, led to the formation of the oxo-bridged dinuclear complex [(μ-O){ReOCl₂(eomi)₂}₂]. The ligand eomi coordinates as a monodentate via the imidazole nitrogen, with the "hard" ether oxygen uncoordinated. An X-ray crystal structure indicates that the chlorides are trans to each other in the ReN₂Cl₂ planes, which are orthogonal to the O=Re-O-Re=O backbone.     

Tricarbonylrhenium(I) and -technetium(I) complexes with bis(2-pyridyl)phenylphosphine and tris(2-pyridyl)phosphine

(NEt₄)₂[Re(CO)₃Br₃] or (NEt₄)₂[Tc(CO)₃Cl₃] react with bis(2-pyridyl)phenylphosphine (PPhpy₂) or tris(2-pyridyl)phosphine (Ppy₃) under formation of neutral tricarbonyl complexes of the composition [M(CO)₃X(L)] (M = Re, X = Br; M = Tc, X = Cl; L = PPhpy₂ or Ppy₃). In all isolated products, the ligands coordinate solely via two of their nitrogen atoms. All attempts to force a tripodal coordination of the phosphinopyridines failed. Removal of the bromo ligands from (NEt₄)₂[Re(CO)₃Br₃] by the addition of AgNO₃ in THF/water, and subsequent reaction of the resulting [Re(CO)₃(THF)₃](NO₃)with Ppy₃ yielded the complex [Re(CO)₃(NO₃)(Ppy₃-N,N′)] with a monodentate coordinated nitrato ligand. The products have been characterized spectroscopically and by X-ray structure analyses.     

Oxorhenium(V) Complexes with Thiosemicarbazones

Neutral oxorhenium(V) complexes with thiosemicarbazones derived from 2‐pyridine formamide, HL¹, are formed when [ReOCl₃(PPh₃)₂] reacts with equimolar amounts of the ligands. Reduction of the metal and the formation of rhenium(III) complexes of the composition [Re(L¹)₂]⁺ occurs when an excess of thiosemicarbazones is used and the reaction is performed in boiling toluene for a prolonged period of time. The thiosemicarbazones deprotonate and act as tridentate ligands as has been confirmed by an X‐ray structure of [ReOCl₂(L^1b)], where HL^1b is 2‐pyridineformamide‐N(4)‐ethylthiosemicarbazone and the ligand occupies the equatorial coordination sphere of the complex together with one of the chloro ligands.     

Syntheses and Structures of Tris-(1,2-Benzosemiquinone DIimine) Complexes of Rhenium(IV)

Reactions of trans-[ReO₂(py)₄Cl] and cis-[ReO₂I(PPh₃)₂] with 2,3-diaminophenol (H₂dab-OH) and 1,2-diaminobenzene (H₂dab), respectively, in ethanol under aerobic conditions led to the corresponding isolation of [Re(sbqdi-OH)₃]Cl (1) and [Re(sbqdi)₃]I (2). Crystallographic data show that the ligand sbqdi represents the monoanionic N,N-coordinated π-radical form of the 1,2-benzosemiquinone diimine of H₂dab. The ligands in Complex 1 clearly show semiquinoid character; e.g., the two C-N and two Re-N bondlengths differ considerably. In 2, the phenyl rings display typical quinoid distortions with two localized double bonds, and the C-N bondlengths are short, approaching double bonds. Rhenium is formally in the +IV oxidation state.     

Preparation and Structures of Several Complexes Containing Carbon-Rich Ligands Attached to Polynuclear Metal Carbonyls

Several new gold-containing cluster complexes have been prepared from the reactions of gold alkynyl complexes, L _n M-C _x -Au(PPh₃), (x = 3, 4, 6) with Ru₃(CO)₁₀(NCMe)₂. The bis-cluster complex 1,4-{AuRu₃(CO)₉(PPh₃)(μ₃-C₂)}₂C₆H₄ was obtained from Ru₃(CO)₁₀(NCMe)₂ and 1,4-{(Ph₃P)Au(C≡C)}₂C₆H₄. The complexes Ru₃(μ-H){μ₃-C₂C≡C[Ru(PP)Cp′]}(CO)₉ [PP = (PPh₃)₂, Cp′ = Cp; PP = dppe, Cp′ = Cp*] were also obtained as minor by-products and synthesised independently from Ru(C≡CC≡CH)(PP)Cp′. A reaction between Co₃{μ₃-CC≡CC≡CAu(PPh₃)}(μ-dppm)(CO)₇ and Ru₃(CO)₁₂ afforded {(Ph₃P)(OC)₉AuRu₃}C≡CC≡CC{Co₃(μ-dppm)(CO)₇} 7. Related complexes AuRu₃{μ₃-C₂C≡[M(CO)₂Tp]}(CO)₉(PPh₃) (M = Mo 8, W 9) were obtained from {Tp(OC)₂M}≡CC≡C{Au(PPh₃)}, while the mixed metal cluster complexes MoM₂(C₂Me)(CO)₈Tp (M = Ru 13, Fe 14) were obtained from M(≡CC≡CSiMe₃)(CO)₂Tp (M = Mo, W) with Fe₂(CO)₉ and Ru₃(CO)₁₂, respectively. Reactions of the Mo carbyne complex with Co₂(LL)(CO)₆ [LL = (CO)₂, μ-dppm] or nickelocene afforded complexes 15–17 in which Co₂ and Ni₂ fragments, respectively, had coordinated to the C≡C triple bond. XRD structural determinations of 7, 8, 14, 16 and {Tp(OC)₂W}≡CC≡CC≡{Co₃(μ-dppm)(CO)₇} (18-W) are reported. In memoriam: F. Albert Cotton (1930–2007).     

Oxorhenium(V)‐ and Tricarbonylrhenium(I) Complexes with Substituted Pyrazoles as Products of the Degradation of Hydrotrispyrazolylborates

Hydrotris(3, 5‐dimethylpyrazol‐1‐yl)borate and hydrotris(3‐phenylpyrazol‐1‐yl)borate decompose during reactions with [ReOCl₃(PPh₃)₂] and [NEt₄]₂[Re(CO)₃Br₃], respectively. The generated pyrazole ligands form complexes with the rhenium(V) oxo and the rhenium(I ) tricarbonyl cores. X‐ray crystal structures of the oxo‐bridged dimer [Cl(PPh₃)(O)Re(μ‐O)(μ‐Me₂pz)₂Re(O)(HMe₂pz)Cl] ( 1 ) and [Re(CO)₃(HPhpz)₂(Phpz)] ( 2 ) (HMe₂pz = 3, 5‐dimethylpyrazole, HPhpz = 3‐phenylpyrazole) show that the substituted pyrazoles can readily deprotonate and act as monodentate or bridging anionic ligands. Re‐N bond lengths between 2.09 and 2.14Å have been observed for the bridging and between 2.12 and 2.23Å for the terminal pyrazole ligands.     

Oxidorhenium(V) and Rhenium(III) Complexes with m-Terphenyl Isocyanides

Reactions of the sterically encumbered m-terphenyl isocyanides CNAr^Dipp2 (Dipp = 2,6-diisopropylphenyl) and CNAr^Mes2 (Mes = 2,4,6-trimethylphenyl) with (NBu₄)[ReOCl₄] in CH₂Cl₂ form stable complexes of the composition (NBu₄)[ReOCl₃(CNAr^R)] or [ReOCl₃(CNAr^R)₂] depending on the amount of isocyanide added. In the [ReOCl₃(CNAr^R)₂] complexes, cis coordination of the two isocyanides is observed for CNAr^Mes2, while the sterically more demanding CNAr^DIPP2 ligands are found in trans positions. The rhenium(III) species [ReCl₃(PPh₃)(CNAr^Mes2)₂] was obtained from the reaction of [ReOCl₃(PPh₃)₂] and CNAr^Mes2. The ν(CN) IR frequencies measured for the Re^V complexes appear at higher wavenumbers than for the uncoordinated isocyanides, which suggests a low degree of backdonation into anti-bonding orbitals of these ligands.     

Silver(I) Complexes with Dithioether Ligands: Syntheses,Crystal Structures,and Fluorescence Properties

Two new dithioether ligands, 1,4‐bis[(phenylsulfanyl)methyl]naphthalene ( L¹ ), and 4,4′‐bis[(tert‐butylsulfanyl)methyl]biphenyl ( L² ) were synthesized and their silver(I) complexes were studied. Both Ag^I complexes, [Ag L¹ (NO₃)]_n ( 1 ) and [Ag L² (NO₃)]₂ ( 2 ), were synthesized at ambient temperature and characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction analysis. Single‐crystal X‐ray analysis shows that complex 1 has a one‐dimensional helical chain structure with the neutral repeating unit [Ag(μ₂‐ L¹ )(NO₃)], whereas complex 2 has a centrosymmetrical neutral dinuclear structure. Moreover, complexes 1 and 2 are further extended into three‐dimensional supramolecular frameworks by hydrogen bonding and π–π stacking interactions, respectively. In addition, complexes 1 and 2 display strong blue emission in the solid state at room temperature.     

Dinuclear Molybdenum(II) Complexes with Thioether Functionalized Silylamide Ligands

Treatment of molybdenum(II) acetate with thioether functionalized silylamides R₂Si(NLi-C₆H₄–2-SR')₂ leads to the formation of dinuclear Mo^II complexes [Mo₂{R₂Si(NC₆H₄-2-SR')₂}₂]. According to X-ray crystal structure analyses the complexes [Mo₂{Me₂Si(NC₆H₄-2-SMe)₂}₂] and [Mo₂{Ph₂Si(NC₆H₄-2-SPh)₂}₂] comprise a Mo₂-unit which is coordinated by two μ-κ-N,N' silylamide ligands. The coordination sphere around the molybdenum atoms consists of two amide nitrogen atoms and two thioether sulfur atoms in a distorted square-planar arrangement. The Mo-Mo distances are 211.0(1) and 211.7(1) pm, resp. In the complex [Mo₂{Ph₂Si(NC₆H₄-2-SMe)₂}₂] the silyl amide units act as tetradentate κ-N,N',S,S'chelating ligands and the Mo-Mo distance is 218.6(1) pm.     

Complexes of cis -dihalogenorhenium(V) with iminophenol

Complexes cis-[ReOX₂(msa)(PPh₃)]?[X?=?Cl(1), I(2)] were prepared from trans-[ReOCl₃(PPh₃)₂] or trans-[ReOI₂(OEt)(PPh₃)²] with 2-(1-iminoethyl)phenol (Hmsa) in acetonitrile. An X-ray crystallographic study shows that the bonding distances and angles in 1 and 2 are nearly identical, and that the two halides in each complex are coordinated cis to each other in the equatorial plane cis to the oxo group. Rhenium(V) complexes with cis diiodides are rare. All bonding distances and angles are in the expected ranges.     

Reactions of Rhenium and Technetium Nitrido Complexes with ER3 Fragments (E = B,Ga, Al,C, P; R = H,Alkyl, Aryl)

Terminal ‘N^3—’ ligands in rhenium and technetium nitrido complexes are sufficiently nucleophilic to react with Lewis acids under formation of nitrido‐bridged compounds. The reactivity of the nucleophilic centre and the nature of the formed compounds are strongly dependent on the Lewis acid and the composition of the metal complex used. Air‐stable compounds with Re≡N‐ER₃ bridges are formed when ER₃ is BR₃ (R = H, Cl, Br, Ethyl, Phenyl, C₆F₅), BCl₂Ph, GaCl₃, CPh₃⁺, or PPh₃. The six‐co‐ordinate rhenium(V) complexes [ReNX₂(PMe₂Ph)₃] (X = Cl, Br), [ReN(X)(Et₂dtc)(PMe₂Ph)₂] (Et₂dtc^— = diethyldithiocarbamate) and [ReN(Et₂dtc)₂(PMe₂Ph)] have been proved to be excellent starting materials for this type of reactions, whereas the five‐co‐ordinate precursors [ReNCl₂(PPh₃)₂], [ReN(Et₂dtc)₂], [ReN{Ph₂P(S)NP(S)Ph₂}₂] or [ReNCl₄]^— only react with the most reactive Lewis bases of the examples mentioned above such as BCl₂Ph or B(C₆F₅)₃. The rhenium‐nitrido bond lengths remain almost unchanged by the adduct formation, whereas a significant decrease of the trans‐influence of the nitrido complexes has been observed as can be seen by a shortening of the corresponding bond lengths or dimerization of five‐co‐ordinate precursors. Electrophilic attack of the Lewis acid to a donor atom of the equatorial co‐ordination sphere of the rhenium complex results in the formation of ‘underco‐ordinate’ metal centres which resemble to di‐, tri or tetrameric units with asymmetric nitrido bridges between each two rhenium atoms. EPR spectroscopy is an excellent tool to reflect the formation of nitrido bridges at the paramagnetic (d¹) [ReNX₄]^— core (X = F, Cl, Br, NCS). The spectral parameters derived for the products of reactions of [ReNCl₄]^— with various boron compounds indicate an increase of the covalency of the equatorial Re‐L bonds as a consequence of the formation of a nitrido bridge. The tendency for the formation of nitrido bridges with Lewis acids is significantly lower for technetium compounds compared to their rhenium analogues. Only a few examples with BH₃ and BPhCl₂ have been established.     

Tricarbonyl Derivatives of Manganese(I) with Diphosphinite Chelating Ligands

Reaction of [MnBr(CO)₃L] [L = Ph₂POCH₂CH₂OPPh₂, L¹ , {(CH₃)₂CH}₂POCH₂CH₂OP{CH(CH₃)₂}₂, L² ] with AgO₃SCF₃ and AgO₂CCF₃ in dichloromethane afforded the new complexes [Mn(O₃SCF₃)(CO)₃L] and [Mn(O₂CCF₃)(CO)₃L], respectively. Substitution of O₃SCF₃ resulted in the new species [Mn(SCN)(CO)₃L], [Mn(NCCH₃)(CO)₃L](O₃SCF₃) and, in the case of L² , [Mn(CN)(CO)₃L²]. By contrast, any attempt to displace the O₂CCF₃ ligand in the same way was unsuccessful. After maintaining for some days the complex [Mn(CH₃CN)(CO)₃L¹](O₃SCF₃) in dichloromethane at room temperature, the new complex [MnCl(CO)₃L¹] was formed. All the new complexes were characterized by elemental analysis, mass spectrometry and IR and NMR spectroscopies. In the case of [Mn(O₃SCF₃)(CO)₃L¹], [Mn(O₂CCF₃) (CO)₃L¹], [MnCl(CO)₃L¹], [Mn(CH₃CN) (CO)₃L²] (O₃SCF₃), [Mn(CN)(CO)₃L²] and [Mn(O₂CCF₃)(CO)₃L²], together with the previously synthesized complex [MnBr(CO)₃L²], suitable crystals for X‐ray structural analysis were isolated. In all of them the Mn atom adopts six‐coordination by bonding to the three CO ligands, the two P atoms of L and either one C atom (CN), one oxygen atom (O₂CCF₃, O₃SCF₃), one N atom (CH₃CN, SCN) or the halogen atom (Cl, Br).