Rhenium(I) carbonyl complexes of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPT). Rhenium(I)-promoted methoxylation of the triazine ring carbon atom in dinuclear rhenium complexes

2,4,6-Tris(2-pyridyl)-1,3,5-triazine (TPT) bridged dinuclear rhenium(I) tricarbonyl halide complexes with the composition (mu-TPT)[ReX(CO)(3)](2) (3, X = Cl; 4, X = Br) can be made either by one-pot reaction of TPT with 2 equiv of [ReX(CO)(5)] (X = Cl and Br) in chloroform or by reacting mononuclear [ReX(CO)(3)(TPT)] (2) (1, X = Cl; 2, X = Br) with an excess amount of [ReX(CO)(5)]. Crystal data are as follows. 1: monoclinic, P2(1)/c, a = 11.751(1) A, b = 11.376(1) A, c = 15.562(2) A, beta = 103.584(2) degrees, V = 2022.0(4) A(3), Z = 4. 2: monoclinic, P2(1)/c, a = 11.896(1) A, b = 11.396(1) A, c = 15.655(1) A, beta = 104.474(2) degrees, V = 2054.9(3) A(3), Z = 4. 3: triclinic, P1, a = 11.541(2) A, b = 12.119(2) A, c = 13.199(2) A, alpha = 80.377(2) degrees, beta = 76.204(3) degrees, gamma = 66.826(2) degrees, V = 1642.5(4) A(3), Z = 2. Crystals of 4 crystallized from acetone: triclinic, P1, a = 11.586(5) A, b = 12.144(5) A, c = 13.364(6) A, alpha = 80.599(7) degrees, beta = 76.271(8) degrees, gamma = 67.158(8) degrees, V = 1678.0(12) A(3), Z = 2. Crystals of 4' are obtained from CH(2)Cl(2)-pentane solution: monoclinic, C2/c, a = 17.555(4) A, b = 15.277(3) A, c = 13.093(3) A, beta = 111.179(3) degrees, V = 3274.0(12) A(3), Z = 4. By contrast, similar reactions in the presence of methanol yielded complexes with the composition [mu-C(3)N(3)(OMe)(py)(2)(pyH)][ReX(CO)(3)](2) (5, X = Cl; 6, X = Br). Crystal data for 5: monoclinic, C2/c, a = 26.952(2) A, b = 16.602(1) A, c = 14.641(1) A, beta = 116.147(1) degrees, V = 5880.5(8) A(3), Z = 8. 6: monoclinic, C2/c, a = 27.513(3) A, b = 16.740(2) A, c = 14.837(2) A, beta = 116.925(2) degrees, V = 6092.8(10) A(3), Z = 8. An unusual metal-induced methoxylation at the carbon atom of the triazine ring of the bridging TPT ligand was observed. The nucleophilic attack of MeO(-) on C(3) results in a tetrahedral geometry around the carbon atom. Concomitantly, the uncoordinated pyridyl ring is protonated and rotated into a perpendicular orientation relative to the central C(3)N(3) ring. Reaction of TPT with [NEt(4)](2)[ReBr(3)(CO)(3)] in benzene-methanol resulted in an unexpected dinuclear complex 7, with formulation [mu-C(3)N(3)(OMe)(py)(3)][Re(CO)(3)][ReBr(CO)(3)]. The methoxylated TPT ligand functions simultaneously as a tridentate and bidentate ligand with two fac-Re(CO)(3)(+) cores. Crystal data for 7: monoclinic, P2(1)/n, a = 12.114(1) A, b = 14.878(1) A, c = 15.807(1) A, beta = 104.601(1) degrees, V = 2756.9(3) A(3), Z = 4.     

Rhenium(V) methylmercaptobenzimidazole complexes

Rhenium(V) complexes with 1-methyl-1H-benzo[d]imidazole-2-thiol (L) and their ammonia and thiocyanate complexes have been synthesized. The composition, structure, and thermal stability of all compounds have been determined by modern physicochemical methods.     

1,2-Dithiooxalatokomplexe von Rhenium(I) und Rhenium(V)

1,2-Dithiooxalato Complexes of Rhenium(I) and Rhenium(V) Cs₄[Re₂(CO)₆(dtox)₃] (dtox ? 1,2-dithiooxalate) is formed by the reaction of Re(CO)₅Br with Cs₂dtox. The dimeric complex ion contains one ligand in a transplanar conformation connecting the two Re atoms, each bearing one chelating dtox ligand. The structure of Cs[ReO (dtox)₂] has been determined from X-ray data. Re is pentacoordinated with one oxygen and four sulfur atoms, which form the basis of a tetragonal pyramid. Re is situated 0.752 Å above the basal plane. The i.r. spectra of both compounds have been assigned.     

Rhenium(I) carbonyl complexes derived from tris(3,5-dimethylpyrazolyl)borate ion

Treatment of [Re(CO)₄Cl]₂ with K[HB(3,5-Me₂C₃HN₂)₃] giving Re{HB(3,5-Me₂C₃HN₂)₃} (CO)₃ and Re(3,5-Me₂C₃HN₂)₂(CO)₃Cl, and bromination of the former to give Re{HB(3,5-Me₂-4-BrC₃N₂)₃}(CO)₃, without displacement of CO, is described.     

Rhenium(I)- and technetium(I) tricarbonyl complexes anchored by bifunctional pyrazole-diamine and pyrazole-dithioether chelators

The novel pyrazolyl containing ligands 4-(HOOC)pz(CH₂)₂NH(CH₂)₂NH₂ (L¹) and 4-(HOOCCH₂)-3,5-Me₂pz(CH₂)₂NH(CH₂)₂NH₂ (L²), and 3,5-Me₂pz(CH₂)₂S(CH₂)₂SCH₂CH₃ (L³), 3,5-Me₂pz(CH₂)₂S(CH₂)₂SCH₂COOEt (L⁴) and 3,5-Me₂pz(CH₂)₂S(CH₂)₂SCH₂COOH (L⁵) were synthesized, and their ability to stabilise complexes with the fac-[M(CO)₃]⁺ (M = Re,^99mTc) moiety was evaluated. Reactions of L¹-L⁵ with the Re(I) tricarbonyl starting materials (NEt₄)₂[Re(CO)₃Br₃] and/or [Re(CO)₅Br] afforded complexes fac-[Re(CO)₃(κ³-L)] (L = L¹-L⁵ (1-5)), which contain the pyrazolyl ancillary ligands coordinated in a tridentate fashion. Complexes 1-5 were characterized by the common analytical techniques, which included single crystal X-ray diffraction analysis in the case of 4. The structural analysis of 4 confirmed the tridentate coordination mode of the pyrazole-dithioether ligand, which is facially coordinated to the Re(I) centre through the nitrogen from the pyrazole ring and the two thioether sulphur atoms, without involvement of the terminal ester functional group. The distorted octahedral coordination environment around the metal is completed by the three facial carbonyl ligands. The radioactive congeners of complexes 1, 3 and 4, fac-[^99mTc(CO)₃(κ³-L)]⁺ (L = L¹ (1a), L³ (3a), L⁴ (4a)), have been prepared by reacting the precursor fac-[^99mTc(CO)₃(H₂O)₃]⁺ with the corresponding ligands, and their identity confirmed by HPLC comparison with the rhenium surrogates. Complexes 1a and 3a have been challenged in the presence of a large excess of histidine or cysteine, in order to evaluate their in vitro stability. Only a negligible displacement was observed, indicating that pyrazole-diamine and pyrazole-dithioether chelators provide a high kinetic inertness and/or stability to organometallic complexes with the fac-[^99mTc(CO)₃]⁺ moiety.     

Rhenium(I) tricarbonyl complexes of 5,10,15,20-tetraphenyl-21-thia and 21-oxaporphyrins

The hexa-coordinated rhenium(I) tricarbonyl complexes of 5,10,15,20-tetraphenyl-21-thiaporphyrin 1 and 5,10,15,20-tetraphenyl-21-oxaporphyrin 2 have been synthesized by thermal reaction of corresponding free base porphyrin with Re(2)(CO)(10). The compounds 1 and 2 are characterized by HR-MS mass, (1)H, and (13)C NMR, FTIR, UV-vis, and electrochemical techniques and the structures are determined by X-ray single crystal analysis. The X-ray analysis revealed different coordination behavior of Re(CO)(3) with 21-thiaporphyrin and 21-oxaporphyrin. Interestingly, the Re(CO)(3) coordinates to two of the three inner nitrogens and one sulfur instead of three inner nitrogens as generally expected to produce unique compound 1 whereas it coordinates to three inner nitrogens but not with furan oxygen to form compound 2. The 21-thiaporphyrin ring is more distorted in compound 1 compared to 21-oxaporphyrin ring in compound 2 on complexation with Re(CO)(3). The presence of three carbonyl groups in compounds 1 and 2 are verified by (13)C NMR and IR spectroscopy. The absorption spectra of compounds 1 and 2 showed ill-defined Q-bands along with broad Soret band and the extinction coefficients are much lower than their corresponding free base porphyrins. The compounds 1 and 2 showed two reversible porphyrin ring based reductions supporting their electron deficient nature. The compound 1 is very stable under protonation conditions, and the protonation occurs at the uncoordinated pyrrole ring whereas the compound 2 undergoes decomplexation under same conditions. Furthermore, compound 1 showed the fluxional behavior in coordination mode of binding in solution.     

Transition metal complexes of bis(diphenylphosphine oxide)methane

Complexes of bis(diphenylphosphine oxide)methane with Fe(III), Ni(II), Co(II), Cu(II) and Zn(II) have been prepared and characterized. Experimental data are in support of chelation by the ligand to give 6-coordinate metal ions. The properties of the complexes are similar to those for the corresponding complexes of octamethylpyrophosphoramide.     

Rhenium(V) complexes with vinyl amides

Summary The reactions oftrans-ReOCl₃(PPh₃)₂ with vinyl amides such as RCOCH=C(R)NH₂, where R = CH₂CH₂CO₂H and R = Ph and C₆H₁₃; or R = Me, CH₂CH₂CO₂Me and R = Ph, give complexes of the type ReOCl₂-[RC(O^–)=CHC(R)=NH]PPh₃, the coordination geometry of which have been deduced from i.r. and¹H n.m.r. spectroscopic data.     

Reactions of bis(diphenylphosphine)acetylene with metal carbonyl complexes

The reaction of [Co₂(CO)₈] with DPPA at room temperature yields a diphosphine bridged product [Co₄(CO)₁₂(μ-Ph₂-P-C≡C-P-Ph₂)₂] 1. Heating of 1 at 45°C promoted cleavage of the P-C_sp bond with the formation of binuclear, phosphido-bridged σ-π-acetylide isomer complexes [Co₂(CO)₅(μ-PPh₂) (μ-σ-π-C≡C-PPh₂ )] 2a, 2b. Heating (60°C) of the complex [CpFe(CO)₂CH₃] and DPPA affords mono and binuclear acetyl, P-coordinated diphenylphosphinoalkyne metal complexes [CpFe(Ph₂P-C≡C-PPh₂)CO(COCH₃)] 3, [CpFeCO(COCH₃)]₂-μ-(Ph₂P-C≡C-PPh₂) 4.     

Rhenium(V) complexes with sulfur-containing amino acids

Rhenium(V) complexes with 2-amino-4-(methylthio)butanoic acid (methionine, Met) and 2-amino-3-sulfopropionic acid (cysteine, Cys) have been synthesized. Depending on the initial reagent ratio, the resulting complexes contain one or two ligand molecules. On heating the compounds with one amino acid molecule, two hydrogen halide molecules are removed at 128–132°C to form a molecular complex. The composition, structure, and thermal stability of the complexes have been studied by elemental analysis, conductometry, IR spectroscopy, NMR, and mass spectrometry.     

Rhenium(V) oxo complexes with N-heterocyclic carbenes

Air-stable rhenium(V) oxo complexes are formed when [ReOCl(3)(PPh(3))(2)] is treated with N-heterocyclic carbenes of the 1,3-dialkyl-4,5-dimethylimidazol-2-ylidene type, L(R) (R = Me, Et, i-Pr). Complexes of the compositions [ReO(2)(L(R))(4)](+), [ReOCl(L(R))(4)](2+), or [ReO(OMe)(L(R))(4)](2+) can be isolated depending on the alkyl substituents at the nitrogen atoms of the ligands and the reaction conditions applied. Despite the steric overcrowding of the equatorial coordination spheres of the metal atoms by each of the four carbene ligands, stable complexes with six-coordinate rhenium atoms are obtained. Steric demands of the alkyl groups allow control of the stability of the mono-oxo intermediates. Air-stable cationic complexes of the compositions [ReOCl(L(Me))(4)](2+), [ReOCl(L(Et))(4)](2+), and [ReO(OMe)(L(Me))(4)](2+) have been isolated, whereas reactions of [ReOCl(3)(PPh(3))(2)] or other rhenium(V) precursors with the more bulky 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (L(i)(-)(Pr)) directly yield the dioxo complex [ReO(2)(L(i)(-)(Pr))(4)](+). X-ray structures of [ReO(2)(L(i)(-)(Pr))(4)][ReO(4)], [ReO(2)(L(i)(-)(Pr))(4)][PF(6)], [ReO(2)(L(Me))(4)][ReO(4)](0.45)[PF(6)](0.55), [ReO(MeOH)(L(Me))(4)][PF(6)](2), and [ReOCl(L(Et))(4)][PF(6)](2) show that the equatorial coordination spheres of the rhenium atoms are essentially planar irrespective of the steric demands of the individual carbene ligands.     

Synthesis and characterisation of chelated (1-cyanoethyl)ruthenium(II) carbonyl complexes

The reaction between acrylonitrile and the RuH bond in HRu(CO)Cl(PPh₃)₃ results in the formation of a binuclear ruthenium(II) complex having chlorine bridges which are easily broken by sodio-derivatives of bidentate chelating ligands giving mononuclear hexacoordinated ruthenium(II) compounds. The RuC bond in these new complexes has been found to be stable towards nucleophilic reagents. The stereochemistry for these complexes has been suggested on the basis of IR, ¹H and ³¹P NMR spectra.     

Photocatalytic properties of new cyclopentadienyl and indenyl rhodium(I) carbonyl complexes with water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) and tris(2-cyanoethyl)phosphine

Reactions of [(η⁵-R)Rh(CO)₂] (R = cp, ind) with water-soluble phosphines (L = 1,3,5-triaza-7-phosphaadamantane and tris(2-cyanoethyl)phosphine) give the new rhodium(I) complexes of the types [Rh(η⁵-cp)(CO)(PTA)] (1), [Rh(η⁵-cp)(CO)(P(CH₂CH₂CN)₃)] (2), [Rh(η⁵-ind)(CO)(PTA)] (3) and [Rh(η⁵-ind)(CO)(P(CH₂CH₂CN)₃)] (4) in isolated yields of 52-75%. All these compounds have been fully characterized by IR, ¹H, ³¹P{¹H} and ¹³C{¹H} NMR, FAB-MS spectroscopies and elemental analyses. Reactivity for the substitution of phosphine is greater for [(η⁵-ind)Rh(CO)(L)] comparing to [(η⁵-cp)Rh(CO)(L)] because of a flexibility of the indenyl ligand to undergo facile η⁵-η³ coordinative isomerizations. The obtained complexes are active catalyst precursors for the dehydrogenation of propan-2-ol, octane and cyclooctane under photoassisted conditions without any organic hydrogen transfer acceptors, giving TOFs of 26-56 using 3 as precatalyst.     

Heterofunctionalized phosphines derived from (2-formylphenyl)diphenylphosphine and their reactions with oxorhenium(V) complexes

Reactions of [ReOCl₃(PPh₃)₂] with a potentially tridentate Schiff base derived from (2-formylphenyl)diphenylphosphine and 2-aminophenol, HL¹P, (HL¹P = Ph₂PC₆H₄-2-HCN(C₆H₄-2-OH)) result in a rapid decomposition of the Schiff base and the formation of a large number of hitherto non-identified metal-containing species, while from similar reactions with the analogoue phosphine oxide HL¹PO, (HL¹PO = Ph₂P(O)C₆H₄-2-HCN(C₆H₄-2-OH)) products of the compositions [ReOCl₂(PPh₃)(L¹PO)] (1) and [Re(NC₆H₄-2-OH)Cl₃(PPh₃)₂] (2) could be isolated. The structure of 2 is an experimental proof of the preceding, metal-induced cleavage of the C–N double bond. A subsequent reaction of the released 2-aminophenol forms the final phenylimido ligand.Reduction of HL¹P with NaBH₄ gives the phosphine amine H₂L²P (H₂L² = Ph₂P(C₆H₄-2-CH₂NH(C₆H₄-2-OH))) in good yield. Reactions of H₂L²P with common oxorhenium(V) complexes result in the formation of the stable rhenium(V) complex [ReOCl₂(HL²P)] (3) with a facially coordinated HL²P^? ligand.     

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.