Schwefel(IV)-Verbindungen als Liganden XVII. Übergangsmetall-vermittelte Insertion von Schwefeldioxid in die C---O-Einfachbindung

Methoxyethyliron complexes [Cp(CO)(L)Fe(CH₂CHROMe)] (L = CO, P(OPh)₃; R = H, Me) insert SO₂ into the C---O single bond wih formation of metalated sulphonic acid esters [Cp(CO)(L)Fe(CH₂-CHRSO₂OMe)]. the insertion is stereospecific wih retention of configuration at carbon. The complexes [Cp(CO)₃M(CH₂CHRSO₂OMe)] (M = Mo, W; R = H, Me) are obtained analogously. Oxidation of [Cp(CO)₃W(CH₂CH₂SO₂OMe)] wih iodine gives the ionic tungsten(IV) alkyl complex [Cp(CO)₃(I)W(CH₂CH₂SO ₂OMe)]⁺. Triphenylphosphine converts [Cp(CO)₃Mo(CH₂CHRSO₂OMe)] into acyl complexes [Cp(CO)₂(Ph₃P)Mo(C(O)CH₂CHRSO ₂OMe)] (R = H, Me), which upon oxidation with Ce^IV in MeOH yield the diesters MeOC(O)CH₂CHRSO₂OMe.     

Half-sandwich and mixed-ring uranium complexes

The monocyclooctatetraene uranium complex [U(COT)(I)₂(THF)₂] (COT=η-C₈H₈; THF=tetrahydrofuran), isolated from the reaction of bis(cyclooctatetraene)uranium with iodine, is a precursor for the synthesis of the alkyl derivatives [U(COT)(CH₂Ph)₂i (HMPA) ₂], [U(COT)(CH₂SiMe₃)₂(HMPA)] (HMPA=hexamethyl phosphorous triamide) and [U(COT)CH₂SiMe₃)₃] [Li(THF)₃] and of the mixed-ring compounds [U(COT)(η-C₅R₅)(I)] (R=H or Me). The last were used to prepare the amide and alkyl complexes [U(COT)(η-C₅H₅)(N{SiMe₃}₂)] and [U(COT)(η-C₅Me₅)(CH₂SiMe₃)].     

Preparation, properties, and reactions of metal-containing heterocycles: Part CV. Synthesis and structure of polyoxadiphosphaplatinaferrocenophanes

A series of novel heterobimetallic crown ether-like polyoxadiphosphaplatinaferrocenophanes cis-[1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂PPh₂)₂]PtCl₂ (n=1–3) (4a–c) was synthesized in good yield by cyclization of the bis(phosphine) ligands 1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂PPh₂)₂ (n=1–3) (3a–c) and (PhCN)₂PtCl₂ under high dilution conditions in CH₂Cl₂. The bisphosphines 3a–c are obtained by reaction of the corresponding diols 1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂OH)₂ (n=1–3) (1a–c) with: (i) CH₃SO₂Cl in CH₂Cl₂ and (ii) LiPPh₂ in THF. Although the X-ray crystal structure of 4a shows that the cavity is large enough for the encapsulation of small metal cations, inclusion experiments of 4a–c with Group 1 cations, and Mg²⁺, or NH₄⁺ in solution applying NMR titration and cyclovoltammetric methods reveal no evidence for the formation of host–guest complexes for 4a,b. In the case of 4c only the addition of Na⁺ or K⁺ leads to an insignificant effect.     

Alkylaminophosphanyl substituted half-sandwich complexes of vanadium(III) and chromium(III): preparation and reactivity in ethylene polymerisation

[Cp^R(RPNEt₂)]M (Cp^R=t-BuC₅H₃, C₅(CH₃)₄, indenyl, fluorenyl; M=Li, K) smoothly react with VCl₃(Me₃P)₂ and CrCl₃(THF)₃ systems giving paramagnetic complexes [Cp^R(R¹PNEt₂)]MCl₂ (M=V(Me₃P)₂, Cr). After reaction with MAO these complexes are active in the polymerisation of ethylene yielding highly crystalline, high-density products of high molecular weight (M_w ranging from 100 000 to 4.5×10⁶ g mol⁻¹, 20≤T_p≤100 °C). Polymerisation with chromium complexes leads to the formation of polyethylenes with broad molecular weight distribution.     

Chemie polyfunktioneller moleküle : LXXXVII. Synthese und reaktionsverhalten von 4-methyl-1,2,6-tristiba-tricyclo[2.2.1.0]heptan (Sb3-nortricyclan) gegenüber chrom-, molybdän- und wolframhexacarbonyl

The reaction of CH₃C(CH₂Cl)₃ and NaSb(C₆H₅)₂ in liquid ammonia leads to Sb₂(C₆H₅)₄ (I). Using CH₃C(CH₂Br)₃ instead of CH₃C(CH₂Cl)₃ results in the formation of I and CH₃C[CH₂Sb(C₆H₅)₂]₃ (II). Treatment of II with gaseous HCl in dry CH₂Cl₂ yields CH₃C(CH₂SbCl₂)₃ (III) under elimination of benzene. The reduction of III with Na in THF gives the first all-cis-organocyclotristibane (Sb₃-nortricyclane) CH₃C(CH₂Sb)₃ (IV) which forms the new CH₃C(CH₂Sb)₃M(CO)₅ complexes (Va---Vc) with M(CO)₅THF (M = Cr, Mo, W).     

New heterodimetallic cyclopentadienyl carbonyl complexes: crystal structure of (C5Me4Et)(μ-CO)3Ru(C5Me5)

A series of heterodimetallic complexes of general formula (C₅R₅)M(μ-CO)₃RuC₅Me₅ (M = Cr, Mo, W; R = Me, Et) has been prepared in good yields by the reaction of [C₅R₅M(CO)₃]⁻ with [C₅Me₅Ru(CH₃CN)₃]⁺. (C₅Me₄Et)W(μ-CO)₃Ru(C₅Me₅) was characterized by a crystal structure determination. The W---Ru bond length of 2.41 Å is consistent with the formulation of a metal-metal triple bond, while the unsymmetrical bonding mode of the three bridging carbonyl groups reflects the inherent non-equivalence of the two different C₅R₅M-units. Using [CpRu(CH₃CN)₃]⁺ or [CpRu(CO)₂(CH₃CN)]⁺ as the cationic precursor leads to the formation of dimetallic species (C₅R₅)M(CO)₅RuC₅H₅ with both bridging and terminal carbonyl groups.     

Group 3 and 4 metal alkyl and hydrido complexes containing a linked amido-cyclopentadienyl ligand: “constrained geometry” polymerization catalysts for nonpolar and polar monomers

In order to understand the nature of the putative cationic 12-electron species [M(η⁵:η¹-C₅R₄SiMe₂NR′)R″]⁺ of titanium catalysts supported by a linked amido-cyclopentadienyl ligand, several derivatives with different cyclopentadienyl C₅R₄ and amido substituents R′ were studied systematically. The use of tridentate variants (C₅R₄SiMe₂NCH₂CH₂X)²⁻ (C₅R₄=C₅Me₄, C₅H₄, C₅H₃^tBu; X=OMe, SMe, NMe₂) allowed the NMR spectroscopic observation of the titanium benzyl cations [Ti(η⁵:η¹-C₅Me₄SiMe₂NCH₂CH₂X)(CH₂Ph)]⁺. Isoelectronic neutral rare earth metal complexes [Ln(η⁵:η¹-C₅R₄SiMe₂NR′)R″] can be expected to be active for polymerization. To arrive at neutral 12-electron hydride and alkyl species of the rare earth metals, we employed a lanthanide tris(alkyl) complex [Ln(CH₂SiMe₃)₃(THF)₂] (Ln=Y, Lu, Yb, Er, Tb), which allows the facile synthesis of the linked amido-cyclopentadienyl complex [Ln(η⁵:η¹-C₅Me₄SiMe₂NCMe₃)(CH₂SiMe₃)(THF)]. Hydrogenolysis of the linked amido-cyclopentadienyl alkyl complex leads to the dimeric hydrido complex [Ln(η⁵:η¹-C₅Me₄SiMe₂NCMe₃)(THF)(μ-H)]₂. These complexes are single-site, single-component catalysts for the polymerization of ethylene and a variety of polar monomers such as acrylates and acrylonitrile. Nonpolar monomers such as -olefins and styrene, in contrast, give isolable mono-insertion products which allow detailed studies of the initiation process.     

Electron transfer in organometallic clusters : XI. Redox chemistry of M3(CO)12(M = Ru, Os) and PPh3 derivatives; mechanism of catalysed nucleophilic substitution

The generality of a two-electron reduction process involving an mechanism has been established for M₃(CO)₁₂ and M₃(CO)₁₂−n(PPh₃)_n (M = Ru, Os) clusters in all solvents. Detailed coulometric and spectral studies in CH₂Cl₂ provide strong evidence for the formation of an ‘opened’ M₃(CO)₁₂²⁻ species the triangulo radical anions M₃(CO)₁₂^−· having a half-life of < 10⁻⁶ s in CH₂Cl₂. However, the electrochemical response is sensitive to the presence of water and is concentration dependent. An electrochemical response for “opened” M₃(CO)₁₂²⁻ is only detected at low concentrations < 5 × 10⁻⁴ mol dm⁻³ and under drybox conditions. The electroactive species ground at higher concentrations and in the presence of water M₃(CO)₁₁²⁻ and M₆(CO)₁₈²⁻ were confirmed by a study of the electrochemistry of these anions in CH₂Cl₂; HM₃(CO)₁₁⁻ is not a product. The couple [M₆(CO)₁₈]^−/2− is chemically reversible under certain conditions but oxidation of HM₃(CO)₁₁⁻ is chemically irreversible. Different electrochemical behaviour for Ru₃(CO)₁₂ is found when [PPN][X] (X = OAc⁻, Cl⁻) salts are supporting electrolytes. In these solutions formation of the ultimate electroactive species [μ-C(O)XRu₃(CO)₁₀]⁻ at the electrode is stopped under CO or at low temperatures but Ru₃(CO)₁₂^−· is still trapped by reversible attack by X presumably as [η¹-C(O)XRu₃(CO)₁₁]⁻. It is shown that electrode-initiated electron catalysed substitution of M₃(CO)₁₂ only takes place on the electrochemical timescale when M = Ru, but it is slow, inefficient and non-selective, whereas BPK-initiated nucleophilic substitution of Ru₃(CO)₁₂ is only specific and fast in ether solvents particulary THF. Metal---metal bond cleavage is the most important influence on the rate and specificity of catalytic substitution by electron or [PPN]-initiation. The redox chemistry of M₃(CO)₁₂ clusters (M = Fe, Ru, Os) is a consequence of the relative rates of metal---metal bond dissociation, metal-metal bond strength and ligand dissociation and in many aspects resembles their photochemistry.     

Studies on organolanthanide complexes : LXIII. Synthesis, spectroscopic and X-ray crystallographic characterization of new early organolanthanide, organoyttrium hydride and organoholmium hydroxide complexes

Organolanthanide chloride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-Cl)]₂ (Ln = La, Pr, Ho and Y) react with excess NaH in THF at 45°C to give the dimeric hydride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-H)]₂, which have been characterized by IR, ¹H NMR, MS and XPS spectroscopy, elemental analyses and X-ray crystallography. [(CH₃OCH₂CH₂C₅H₄)₂Y(μ-H)]₂ crystallizes from THF/n-hexane at −30°C, in the triclinic space group P1 with a = 8.795(2) Å, b = 11.040(1) Å, c = 16.602(2) Å, = 93.73(1)°, β = 91.82(1)°, γ = 94.21(1)°, D_c = 1.393 gcm⁻³ for Z = 2 dimers. However, crystals of [(CH₃OCH₂CH₂C₅H₄)₂Ho(μ-OH)]₂ were obtained by recrystallization of holmium hydride in THF/n-hexane at −30°C, in the orthorhombic space group Pbca with a = 11.217(2) Å, b = 15.865(7) Å, c = 17.608(4) Å, D_c = 1.816 gcm⁻³ for Z = 4 dimers. In the complexes of yttrium and holmium, each Ln atom of the dimers is coordinated by two substituted cyclopentadienyl ligands, one oxygen atom and two hydrogen atoms (for the Y atom) or two hydroxyl groups (for the Ho atom) to form a distorted trigonal bipyramid if the C(η⁵)-bonded cyclopentadienyl is regarded as occupying a single polyhedral vertex.     

Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen : XLV. Eigenschaften und Reaktionsverhalten von Hydrogenchalkogenid-Komplexen der Metalle Chrom, Molybdän und Wolfram

Hydrogensulfido and hydrogenselenido complexes of general composition (η⁵-C₅R₅(CO)3M(EH) (R = H, CH₃; M = Cr, Mo, W; E = S, Se) react at the EH functions by deprotonation, bimolecular elimination of H₂E, or by loss of the chalcogen atoms E. Reactions with Lewis-acidic complex cations such as [((η⁵-C₅R₅)(CO)₃M]⁺ (R = H, CH₃; M = Mo, W) are useful for the synthesis of chalcogen bridged compounds (μ-E)[(η⁵-C₅R₅)(CO)₃M]₂. The heterodinuclear chalcogen bridge complexes thus generated form metathesis equilibria with their corresponding homodinuclear systems.     

Synthesis, characterization of new Rh---Co mixed-metal clusters and reactions of clusters containing [Rh2Co2C2] core with 1-alkynes and/or carbon monoxide

Six new cluster derivatives [Rh₂Co₂(CO)₆(μ-CO)₄(μ₄,η²-HCCR)] (R=FeCp₂ 1, CH₂OH 2, (CH₃O)C₁₀H₆CH(CH₃)COOCH₂CCH 3) and [RhCo₃(CO)₆(μ-CO)₄(μ₄,η²-HCCR)] (R=FeCp₂ 4, CH₂OH 5, (CH₃O)C₁₀H₆CH(CH₃)COOCH₂CCH 6) were obtained by the reactions of [Rh₂Co₂(CO)₁₂] and [RhCo₃(CO)₁₂] with substituted 1-alkyne ligands HCCR [R=FeCp₂ 7, CH₂OH 8, (CH₃O)C₁₀H₆CH(CH₃) COOCH₂CCH 9] in n-hexane at room temperature, respectively. Alkynes insert into the Co---Co bond of the tetranuclear clusters to give butterfly clusters. [Rh₂Co₂(CO)₆(μ-CO)₄(μ₄,η²-HCCFeCp₂)] (1) was characterized by a single-crystal X-ray diffraction analysis. Reactions of 1, 2 with 7, 8 and ambient pressure of carbon monoxide at 25 °C gave two known cluster complexes [Co₂(CO)₆(μ₂, η²-HCCR)] (R=FeCp₂ 10, CH₂OH 11), respectively. All clusters were characterized by element analysis, IR and ¹H-NMR spectroscopy.     

Tris(pyrazolyl)methane–chromium(III) complexes as highly active catalysts for ethylene polymerization

Reaction of complex CrCl₃(THF)₃ with the tris(pyrazolyl)methane ligands, HC(Pz)₃, HC(3,5-Me₂Pz)₃ and their substituted derivatives RC(Pz)₃ (R = Me, CH₂OH, CH₂OSO₂Me) in THF lead to the formation of neutral complexes of the types [RC(Pz)₃CrCl₃] and [RC(3,5-Me₂Pz)₃CrCl₃]. After reaction with methylalumoxane (MAO) these complexes are active in the polymerization of ethylene. The substituent on the methane central carbon atom of the ligand has some influence in polymerization behavior. This compounds present higher activities than similar chromium complexes, in the ethylene polymerization reaction.     

Aminosubstituierte 2-azoniaallenyliden-komplexe des chroms und wolframs

The successive reaction of chromium and tungsten hexacarbonyl, (CO)₆M (M = Cr, W), with [N=C(Ph)R]⁻ and [Et₃O]BF₄ yields the alkylideneamino(ethoxy)carbene complexes (CO)₅M[C(OEt)N=C(Ph)R] (M = Cr (1), W (2); R = NMe₂ (a), ^tBu (b)). Ethoxide abstraction from 1 and 2 affords 2-azoniaallenylidene complexes, {(CO)₅M[CNC(Ph)R]}⁺BF₄⁻ (3/4). The complexes 3 and 4 are best described as resonance hybrids of several limiting structures. On the basis of the spectroscopic data of the complexes 3a and 4a the limiting structure of an iminium-substituted isocyanide complex dominates.     

Synthesis of Re-Ru heterobimetallic polyhydride complexes. Study of the influence of ligands bonded to the monometallic precursors on the nature of the isolated binuclear complexes

The reaction of K[H₆ReL₂] with [RuHCl(CO)(PPh₃)_3−x {P(OPrⁱ}₃)_x](L₂ = (PMePh₂)₂, dppe, (AsPh₃)₂, or (PPh₃)₂; x = 0, 1 or 2) leads to [L₂(CO)HRe(μ-H)₃RuH(PPh₃)_2−y{P(OPrⁱ)₃}_y] (x = 0 or 1, Y = 0; X = 2, Y = 1(L₂ = PPh₃)) in a first step. Under the reaction conditions most of these complexes react rapidly with the liberated phosphine giving [L₂(CO)Re(μ-H)₃Ru(PPh₃)_3−y- {P(OPrⁱ)₃}_y] (L₂ = (PMePh₂)₂ or dppe, Y = 0; L₂ = (PPh₃)₂, Y = 1) as the only iso complexes. The structure of [(PMePh₂)₂(CO)Re(μ-H)₃Ru(PPh₃)₃] has been establishedby X-ray structure analysis. The complex [(PPh₃)₂(CO)Re(μ-H)₃Ru(PPh₃)₂(P(OPrⁱ)₃)] reacts with molecular hydrogen under pressure to generate [L₂(CO)HRe(μ-H)₃RuH(PPh₃)(P(OPrⁱ)₃) as the sole product.     

Multiple ligand transfer reaction between [CpRu(L)(AN)2][PF6] (L=AN, CO, P(OMe)3; AN=acetonitrile) and CpFe(CO)L′X (L′=CO, PMe3, PMe2Ph, PMePh2, PPh3, P(OPh)3; X=Cl, Br, I)

Treatment of ruthenium complexes [CpRu(AN)₃][PF₆] (1a) (AN=acetonitrile) with iron complexes CpFe(CO)₂X (2a–2c) (X=Cl, Br, I) and CpFe(CO)L′X (6a–6g) (L′=PMe₃, PMe₂Ph, PMePh₂, PPh₃, P(OPh)₃; X=Cl, Br, I) in refluxing CH₂Cl₂ for 3 h results in a triple ligand transfer reaction from iron to ruthenium to give stable ruthenium complexes CpRu(CO)₂X (3a–3c) (X=Cl, Br, I) and CpRu(CO)L′X (7a–7g) (L′=PMe₃, PMe₂Ph, PMePh₂, PPh₃, P(OPh)₃; X=Br, I), respectively. Similar reaction of [CpRu(L)(AN)₂][PF₆] (1b: L=CO, 1c: P(OMe)₃) causes double ligand transfer to yield complexes 3a–3c and 7a–7h. Halide on iron, CO on iron or ruthenium, and two acetonitrile ligands on ruthenium are essential for the present ligand transfer reaction. The dinuclear ruthenium complex 11a [CpRu(CO)(μ-I)]₂ was isolated from the reaction of 1a with 6a at 0°C. Complex 11a slowly decomposes in CH₂Cl₂ at room temperature to give 3a, and transforms into 7a by the reaction with PMe₃.     

Acyl complexes of molybdenum: structural and reactivity studies

The following structural peculiarities of the agostic acyl structure ₂R) (R = H, SiMe₃) and some characteristic chemical reactivity of the M-η²-acyl and iminoacyl linkage are described. (i) A structural comparison of the bonding parameters within three agostic acetyl Mo complexes containing the dithioacid ligand, indicates that the agostic interaction strengthens upon increasing the electron-releasing properties of the S-chelating ligand. (ii) The acyl-xanthate complex Mo(C(O)Me)(S₂COR)(CO)(PMe₃)₂ undergoes loss of a sulfur atom from the coordinated xanthate and coupling with the acyl ligand to form complexes containing coordinated alkoxythiocarbonyl and monothioacetate ligands. The latter can be metathetically replaced by KS₂COR. (iii) Upon heating at 70°C η²-acyl-dicarbonyl bispirazolilborate complexes of molybdenum of the type Mo(H₂B(pz^*)₂)(η²-C(O)Me)(CO)₂(PMe₃) (pz^* = 3,5-dimethyl-pyrazol-1-yl) yield functionalized acyl ligands derived from the stereo- and regioselective intramolecular addition of one of the B---H bonds of the H₂B(pz^*)₂ group across the C=O moiety of the η²-acyl group. (iv) The η²-acyl-isocyanide complexes {Mo}(η²-C(O)R)(CNR′) ({Mo} = Mo(H₂B(pz^*)₂)(CO)(PMe₃)) undergo irreversible thermal isomerization to the corresponding η²-iminoacyl-carbonyl derivatives {MO}(η²-C(NR′)R)(CO). This isomerization reaction follows first-order kinetics.     

M(CO)4 (M = Mo or W) complexes of 2,6-bis(methylthiomethyl)pyridine (L) and 2,6-bis(p-tolylthiomethyl)pyridine (L): a dynamic NMR study

The hybrid S/N/S donor ligands 2,6-bis(methylthiomethyl)pyridine (L¹) and 2,6-bis(p-tolylthiomethyl)pyridine (L²) react with the [M(CO)₅(THF)] (M = Mo or W) compounds to form complexes of general formula [M(CO)₄L] (M = Mo, L = L²; M = W, L = L¹ or L²), where both L¹ and L² act in a S/N bidentate chelate fashion. In solution, these complexes undergo three fluxional processes, viz. inversion at the coordinated S atom, S¹–S² switching, and combined inversion and S¹–S² switching, leading to an interconversion of the four possible permutational isomers. Energy barriers for all three processes have been evaluated by standard one-dimensional band-shape analysis techniques. The mechanism of the S¹–S² switch is discussed.     

Synthesis, structure and reactivity of homobimetallic Rh(I) and Ir(I) complexes of s- and as-indacene-diide

The Rh(COD) and Ir(COD) homobimetallic complexes of s-indacene-diide, 2,6-dimethyl-s-indacene-diide, as-indacene-diide, and 2,7-dimethyl-as-indacene-diide have been synthesized from the di-lithium salts of the dianions and metal dimers [M(μ-Cl)L₂]₂ (M = Rh, Ir; L₂ = COD, NBD, (ethylene)₂, (CO)₂ as mixtures of syn and anti isomers. The syn/anti ratio depends on the nature of the ancillary ligands at the metal and on the s or as geometry of the bridging ligand. In the reaction of the 2,7-dimethyl-as-indacene-diide-[M(COD)]₂ species with CO, the higher reactivity of the syn isomers has been justified on the basis of a greater instability of the ground state due to steric interactions between the COD groups. Bis-η¹ metal-bonded intermediates have been identified in the carbonylation of iridium derivatives; on the other hand, the formation of the bis-η⁵ mixed complexes syn and anti-{2,7-dimethyl-as-indacene-diide-[Rh(COD)][Rh(CO)₂]} and their reactivity strongly support the existence of metal---metal interaction in the rhodium derivatives.     

Complexes of nitrilotrimethylphosphonic acid with cobalt, nickel, copper and zinc

Substances of the types MH₄ntmp, Mg₃[M(Hntmp)]₂, M₂H₂ntmp and Mg[M₂(Hntmp)]₂, where M = Co, Ni, Cu, Zn and H₆ntmp = N[CH₂PO(OH)₂]₃ were prepared. The sodium and cesium salts of the [Co(Hntmp)]³⁻ complexes were also prepared. The IR and electronic spectra and the experimental magnetic susceptibilities indicate that these are high-spin complexes. The coordination surroundings of the central atom consist of a highly distorted octahedron of the ligand oxygen atoms. The nitrogen atom is not coordinated to the central atom.     

Tricarbonylrhenium(I) complexes of phosphine-derivatized amines, amino acids and a model peptide: structures, solution behavior and cytotoxicity

Modified Mannich reactions of amines, amino acids and a model peptide with Ph₂PH and CH₂O gave bis(diphenylphosphinomethyl)amines (Ph₂PCH₂)₂NR [R=Ph (1), CH₂CH₂OH (2), CH₂COOCH₂Ph (3), CH₂CONHCH₂COOCH₂Ph (4), CH₂COOH (5)] and (Ph₂PCH₂)₂NCH₂CH₂N(CH₂PPh₂)₂ (6). Reaction with [ReBr₃(CO)₃]²⁻ under mild conditions led to [ReBr(CO)₃]{(Ph₂PCH₂)₂NR} [R=Ph (7), CH₂CH₂OH (8), CH₂COOCH₂Ph (9), CH₂CONHCH₂COOCH₂Ph (10), CH₂COOH (11)] and [ReBr(CO)₃(Ph₂PCH₂)₂NCH₂]₂ (12). All new complexes have been characterized by NMR and IR spectroscopy and for 7, 9 and 10, single-crystal X-ray diffraction analyses. Electrospray mass spectrometric studies show that the rhenium–phosphine chelates are very stable, especially in neutral methanolic solution. Hydrolysis of the ester and amide linkages slowly occur in acidic and basic solutions over several weeks; displacement of the bromide ligand also occurs in basic medium. Cytotoxicity testing of 7–10 and 12 showed that all the complexes are active against specific tumor cell lines, especially MCF-7 breast cancer and HeLa-S³ suspended uterine carcinoma.