Preparation of trihydridostannyl complexes of rhenium stabilised by isocyanide ligands

Mixed-ligand complexes [ReBr(CO)₂(CNR)_nL_3−n] (1-4) [R = 4-CH₃OC₆H₄, 4-CH₃C₆H₄, C(CH₃)₃; L = P(OEt)₃, PPh(OEt)₂; n = 1, 2] were prepared by allowing carbonyl compounds [ReBr(CO)₄L] and [ReBr(CO)₃L₂] to react with an excess of isocyanide. Treatment of these bromocomplexes [ReBr(CO)₂(CNR)_nL_3−n] with SnCl₂ · 2H₂O yielded the trichlorostannyl derivatives [Re(SnCl₃)(CO)₂(CNR)_nL_3−n] (5-8). Trihydridestannyl complexes [Re(SnH₃)(CO)₂(CNR)_nL_3−n] (9-12) were prepared by allowing trichlorostannyl compounds 5-8 to react with NaBH₄ in ethanol. The trimethylstannyl derivative [Re(SnMe₃)(CO)₂(CNC₆H₄-4-CH₃){PPh(OEt)₂}₂] (13b) was also prepared by treating [Re(SnCl₃)(CO)₂(CNC₆H₄-4-CH₃){PPh(OEt)₂}₂] with an excess of MgBrMe in diethylether. Reaction of the tin trihydride complexes [Re(SnH₃)(CO)₂(CNR)_nL_3−n] (9-12) with CO₂ (1 atm) led to dinuclear OH-bridging bis(formate) derivatives [Re{Sn(OC(H)O)₂(μ-OH)}(CO)₂(CNR)_nL_3−n]₂ (14, 15). The complexes were characterised spectroscopically (IR, ¹H, ³¹P, ¹³C, ¹¹⁹Sn NMR) and by X-ray crystal structure determination of [Re(SnH₃)(CO)₂{CNC(CH₃)₃}{PPh(OEt)₂}₂] (10b).     

Reactivity of the bridged borylene complex [μ-BCl{η-C5H4Me)Mn(CO)2}2]

The reactivity of the bridged chloro borylene complex [μ-BCl{(η⁵-C₅H₄Me)Mn(CO)₂}₂] (2a) towards various protic reagents was studied. Reaction of 2a with isopropanol yielded the alkoxy borylene complex [μ-BOiPr{(η⁵-C₅H₄Me)Mn(CO)₂}₂] (3d) in very high yield. A further series of protic reagents HX (X=HS⁻, BF₄⁻, Co(CO)₄⁻) gave, in the presence of pyridine, the new amino borylene complex [1-(μ-B)-4-H-(NC₅H₅){(C₅H₄Me)Mn(CO)₂}₂] (5a), which represents the product of an unprecedented 1,4-hydroboration of pyridine. Complex 5a was fully characterised in solution by multinuclear NMR studies, in the solid state by X-ray diffraction, and was also subject to DFT-studies.     

Synthesis and X-ray structures of rhenium(I) carbonyl aminoalkoxide and aminocarboxylate complexes

The complexes [Re{MeN(CH₂CH₂O)(CH₂CH₂OH)-κ³N,O,O}(CO)₃] (1), [Re{N(CH₂CH₂O)(CH₂CH₂OH)₂-κ³N,O,O}(CO)₃] (2), [Me₃NH]₂[(OC)₃Re{N(CH₂CO₂)₂-κ³N,O,O}CH₂CH₂{N(CH₂CO₂)₂-κ³N,O,O}Re(CO)₃] (3), [Me₃NH]₂[Re₂{μ₂-2,6-(O₂C)₂(C₅H₃N)-κ³N,O,O}₂(CO)₆] (4) and [Re₂{μ₂-2,6-(OCH₂)(C₅H₃N)(CH₂OH)-κ²N,O}₂(CO)₆] (5) were synthesized in high yields via the reactions of [Re₂(CO)₁₀] and Me₃NO with MeN(CH₂CH₂OH)₂, N(CH₂CH₂OH)₃, EDTA, pyridine-2,6-dicarboxylic acid and pyridine-2,6-dimethanol, respectively. Complexes 1-5 were characterized by IR and ¹H NMR spectroscopy, elemental analysis and X-ray crystallography.     

Transformations of the Vaska-type complex trans-[RhCl(CO)(PTA)2] (PTA = 1,3,5-triaza-7-phosphaadamantane) during stepwise addition of HCl: Synthesis, characterization and crystal structure of trans-[RhCl2(PTA)(PTAH)]

The new aqua-soluble rhodium(I) complex trans-[RhCl₂(PTA)(PTAH)] (1) {PTAH = N-protonated form of 1,3,5-triaza-7-phosphaadamantane (PTA)} has been synthesized via the reaction of trans-[RhCl(CO)(PTA)₂] with aqueous HCl or N-chlorosuccinimide, or by the treatment of RhCl₃ with PTA. Compound 1 has been characterized by IR, ¹H and ³¹P{H} NMR spectroscopies, ESI-MS(+), elemental and single crystal X-ray diffraction analyses, the latter showing a square planar {RhCl₂P₂} geometry. Besides, the stepwise addition of diluted HCl to an aqueous solution of trans-[RhCl(CO)(PTA)₂] has been monitored by ³¹P{¹H} NMR and ESI-MS(+) techniques, allowing to detect a number of intermediate Rh(I) species.     

Synthesis of iron thienyl complexes

Dimetallation of thiophene (TH₂), bithiophene (BTH₂) and 3,6-dimethyl[3,2-b]thienothiophene (TTH₂) using a slight excess of butyl lithium, followed by the addition of [FeCp(CO)₂I], resulted in the formation of [2,5-{FeCp(CO)₂}₂T], 1 and [2-{FeCp(CO)₂}T]. The analogous reaction with bithiophene as precursor afforded similar products [2,2′-{FeCp(CO)₂}₂BT] 2 and [2-{FeCp(CO)₂}BTH] 3. In addition to the expected mono- ([2-{FeCp(CO)₂}-TTH] 4) and binuclear ([2,2′-{FeCp(CO)₂}₂-TT] 5) products, dimetallation of 3,6-dimethyl[3,2-b]thienothiophene and the subsequent reaction with [FeCp(CO)₂I] yielded carbonyl inserted mono-([2-{FeCp(CO)₂}C(O)-{TT}₂H] 6) and binuclear ([2-{FeCp(CO)₂}C(O)-{TT}₂-2′-{FeCp(CO)₂}] 7) carbon-carbon coupled products. The precursor [2,7-{SnMe₃}₂-TT] (8) was prepared and reacted with [FeCp(CO)(PEt₃)I] in the presence of a palladium catalyst to afford [2-{FeCp(CO)(PEt₃)}C(O)-{TT}₂-2′-{SnMe₃}] 10.     

Aggregation of imino-phosphonate monoester complexes

The aggregates {[Zn(L¹)]H₂O}_∞ and {[Y(L²)]₄Na₃(H₂O)₂(MeOH)_1.2}(NO₃)₃·2H₂O·5.6MeOH have been assembled from complexes of imino-phosphonate monoester ligands [L¹]²⁻ {CH₂[CH₂NC(CH₃)PO₂(OMe)]₂}²⁻ and [L²]³⁻ {N[CH₂CH₂NC(CH₃)PO₂(OMe)]₃}³⁻, the topology of these materials differing from that of their imino-carboxylate analogues.     

Complexes with 6-amino-5-nitroso-2-thiouracil and violuric acid derivatives containing the fac-Re(CO)3 core: Synthesis, XRD structural and photoluminescence characterization

The fac-tricarbonylrhenium(I) complexes of the 6-amino-1,3-dimethyl-5-nitroso-2-thiouracil (DANTU) and violuric acid (VIO) and its mono- (MVIO) and dimethyl (DVIO) derivatives have been prepared. The complexes have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectral methods and luminescence spectroscopy. The structures of [ReCl(CO)₃(DANTU)], [Re(H₂O)(CO)₃(VIOH₋₁)] and [Re(H₂O)(CO)₃(DVIOH₋₁)] complexes were solved from single-crystal X-ray diffraction experiments. The coordination environment around the Re(I) may be described as a distorted octahedron in which the ligand behaves in a bidentate fashion through the nitrogen atom of the nitroso group and an adjacent carbonylic oxygen, making a five-membered chelate ring. The coordination sphere is completed with three carbonyl groups in fac-arrangement and one chlorine atom (DANTU complex) or water molecule (VIO complexes). The higher acidity of violuric acids, if compared with DANTU one, may explain both synergic deprotonation and chloride substitution in the [ReCl(CO)₃]⁺ moiety to form the Re-violurato complexes.     

High-temperature spin-crossover in coordination compounds of iron(II) with tris(pyrazol-1-yl)methane

Novel mononuclear Fe(II) complexes of tris(pyrazol-1-yl)methane [Fe{HC(pz)₃}₂]²⁺ with and p-sulfonatothiacalix[4]arene (TCAS⁴⁻) as counterions were obtained. The compounds were characterized by magnetic susceptibility method, IR and UV-Vis spectroscopy. The structure of [Fe{HC(pz)₃}₂]SiF₆ has been analyzed by single-crystal X-ray diffraction. The ¹H NMR spectroscopy measurements of [Fe{HC(pz)₃}₂]₂(TСAS) in aqueous solution reveal the outer sphere inclusion of [Fe{HC(pz)₃}₂]²⁺ into the cyclophanic cavity of TCAS⁴⁻. The temperature induced spin-crossover ¹А₁ ⇔ ⁵Т₂, accompanied by thermochromism, has been revealed from the temperature dependence of μ_eff and IR spectra for both complexes. The comparative analysis of magnetochemical and spectroscopy data elucidates the effect of the cyclophanic counterion on the physico-chemical properties of Fe(II) complex.     

Synthesis and characterization of mixed-ligand ruthenium(III) complexes with oxalate and acetylacetonate ions

Two mononuclear mixed-ligand ruthenium(III) complexes with oxalate dianion (ox²⁻) and acetylacetonate ion (2,4-pentanedionate, acac⁻), K₂[Ru(ox)₂(acac)] (1) and K[Ru(ox)(acac)₂] (2), were prepared as a candidate for a building block. In fact, reaction of complex 2 with manganese(II) sulfate gave a heterometallic tetranuclear complex, TBA[Mn^II{(μ-ox)Ru^III(acac)₂}₃] (5) in the presence of tetrabutylammonium (TBA) bromide. The ¹H NMR, UV-Vis, selected IR and FAB mass spectral data of these complexes are presented. Both mixed-ligand ruthenium(III) complexes gave a Nernstian one-electron reduction step in 0.1 mol dm⁻³ Na₂SO₄ aqueous solution on a mercury electrode at 25 °C. Comparison of observed reversible half-wave potentials with calculated values for a series of [Ru(ox)_n(acac)_3 − n]ⁿ⁻ (n=0-3) complexes by using Lever’s ligand electrochemical parameters is presented.     

Syntheses, stereochemistry, reactivity, and some properties of sulfur-bridged cobalt(III)-cadmium(II) polynuclear complexes derived from mononuclear cobalt(III) complex with d-penicillaminate

A reaction of the octahedral bidentate metalloligand, trans(N)-[Co(d-pen)₂]⁻ (d-pen=d-penicillaminate) with Cd(NO₃)₂ or Cd(ClO₄)₂ gave a novel S-bridged trinuclear complex, [Cd(H₂O){Co(d-pen)₂}₂] (1). In this complex molecule, the central Cd atom is surrounded by four S atoms from two [Co(d-pen)₂]⁻ units and one O atom of a H₂O molecule to form a distorted five-coordinated geometry. Each of two terminal [Co(d-pen)₂]⁻ units takes an approximately octahedral geometry and has a similar trans(N) geometry to that of the starting material. On the other hand, the reaction of trans(N)-[Co(d-pen)₂]⁻ with CdCl₂ in the molar ratio of 1:1 gave an S-bridged dinuclear complex, [CdCl{Co(d-pen)₂}(H₂O)_m]·nH₂O (m+n=4) (2). The reactivity of trans(N)-[Co(d-pen)₂]⁻ toward CdCl₂ is significantly influenced by the ratio of two components, and the formation of a similar trinuclear species to 1 is also suggested under the condition with excess amount of trans(N)-[Co(d-pen)₂]⁻. Some spectrochemical properties of these complexes are also discussed in relation to their structures.     

Stereosensitive formation and interconversion of sulfur-bridged cobalt(III)-mercury(II) polynuclear complexes with d- and/or l-penicillaminates

The reaction of trans(N)-[Co(d-pen)₂]⁻ (pen = penicillaminate) with HgCl₂ or HgBr₂ in the molar ratios of 1:1 gave the sulfur-bridged heterodinuclear complex, [HgX(OH₂){Co(d-pen)₂}] (X = Cl (1a) or Br (1b)). A similar reaction in the ratio of 2:1 produced the trinuclear complex, [Hg{Co(d-pen)₂}₂] (1c). The enantiomers of 1a and 1c, [HgCl(OH₂){Co(l-pen)₂}] (1a′) and [Hg{Co(l-pen)₂}₂] (1c′), were also obtained by using trans(N)-[Co(l-pen)₂]⁻ instead of trans(N)-[Co(d-pen)₂]⁻. Further, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 1:1 resulted in the formation of [HgCl(OH₂){Co(d-pen)(l-pen)}] (2a). During the formations of the above six complexes, 1a, 1b, 1c, 1a′, 1c′, and 2a, the octahedral Co(III) units retain their configurations. On the other hand, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 2:1 gave not [Hg{Co(d-pen)(l-pen}₂] but [Hg{Co(d-pen)₂}{Co(l-pen)₂}] (2c), accompanied by the ligand-exchange on the terminal Co(III) units. The X-ray crystal structural analyses show that the central Hg(II) atom in 1c takes a considerably distorted tetrahedral geometry, whereas that in 2c is of an ideal tetrahedron. The interconversion between the complexes is also examined. The electronic absorption, CD, and NMR spectral behavior of the complexes is discussed in relation to the crystal structures of 1c and 2c.     

Reactivity of phenyldi(2-thienyl)phosphine towards group 7 metal carbonyls: Carbon-phosphorus bond activation

Addition of phenyldi(2-thienyl)phosphine (PPhTh₂) to [Re₂(CO)_10−n(NCMe)_n] (n = 1, 2) affords the substitution products [Re₂(CO)_10−n(PhPTh₂)_n] (1, 2) together with small amounts of fac-[ClRe(CO)₃(PPhTh₂)₂] (3) (n = 2). Reaction of [Re₂(CO)₁₀] with PPhTh₂ in refluxing xylene affords a mixture which includes 2, [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-H)] (4), [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-η¹,κ¹(S)-C₄H₃S)] (5) and mer-[HRe(CO)₃(PPhTh₂)₂] (6). Phosphido-bridged 4 and 5 are formed by the carbon-phosphorus bond cleavage of the coordinated PPhTh₂ ligand, the cleaved thienyl group being retained in the latter. Reaction of [Mn₂(CO)₁₀] with PPhTh₂ in refluxing toluene affords [Mn₂(CO)₉(PPhTh₂)] (7) and the carbon-phosphorus bond cleavage products [Mn₂(CO)₆(μ-PPhTh)(μ-η¹,η⁵-C₄H₃S)] (8) and [Mn₂(CO)₅(PPhTh₂)(μ-PPhTh)(μ-η¹,η⁵-C₄H₃S)] (9). Both 8 and 9 contain a bridging thienyl ligand which is bonded to one manganese atom in a η⁵-fashion.     

Syntheses, properties, and structural characteristics of several new [tetrakis(1-pyrazolyl)borato]samarium(III) complexes: comparative study of the B(pyrazolyl)4 and BH(pyrazolyl)3 ligation

Although reactions of samarium(III) chloride, SmCl₃ · 6H₂O, with potassium hydrotris(1-pyrazolyl)borate K[BH(pz)₃] (pz = 1-pyrazolyl) in a molar ratio of (1/1) in THF afford [SmCl{BH(pz)₃}₂(Hpz)], similar reactions with K[B(pz)₄] gave rise to separation of anhydrous H[B(pz)₄]. The homoleptic eight-coordinate complex [Sm{B(pz)₄}₃] obtained from SmCl₃ · 6H₂O and threefold moles of K[B(pz)₄] was allowed to react with twofold moles of K[BH(pz)₃] to give a mixture of three major species [Sm{B(pz)₄}_n{BH(pz)₃}_(3 − n)] (n = 2, 1, 0), whereas similar reactions of [Sm{BH(pz)₃}₃] with K[B(pz)₄] did not proceed at all. The acetylacetonato (acac) complex [Sm{B(pz)₄}₂(acac)], derived from the triflate “Sm{B(pz)₄}₂(OTf)”, was treated with twofold moles of K[BH(pz)₃] and showed its quantitative conversion to [Sm{BH(pz)₃}₂(acac)]. However, analogous reaction of [Sm{BH(pz)₃}₂(acac)] with K[B(pz)₄] did not proceed. Accordingly, samarium(III) ion was determined to prefer coordination of BH(pz)₃ ligand to that of B(pz)₄, indicating less σ-donating electronic character of the latter. The complexes [Sm{B(pz)₄}₂(L-L)] (L-L = β-ketoenolato) in toluene-d₈ exhibited ¹H NMR spectroscopic equivalence of all four pyrazolyl groups at high temperatures, and are regarded as a new class of B(pz)₄ complexes, showing fast intramolecular exchange of their coordinated and uncoordinated pyrazolyl groups. Four compounds were crystallographically characterized.     

Ligand substitution reactions of the [ReX6] (X = Cl, Br) anions. Synthesis and crystal structure of novel oxalato complexes of rhenium(IV)

The reaction of K₂[ReX₆] (X = Cl, Br) with oxalic acid and triethylamine in dimethylformamide solution yields the substituted complexes [ReX₄(ox)]²⁻ and cis-[ReX₂(ox)₂]²⁻, which can be obtained separately depending on the amount of added amine. The crystal structures of (PPh₄)₂[ReBr₄(ox)], cis-(PPh₄)₂[ReBr₂(ox)₂] and cis-(AsPh₄)₂[ReCl₂(ox)₂] have been determined by single-crystal X-ray diffraction. The anionic complexes are octahedral with only slight distortions. The direct isolation of the pure complexes as well as the formation of only the cis isomers - without the presence of trans isomers and/or [Re(ox)₃]²⁻ - is probably due to the kinetic inertness of Re(IV)-X bonds, which increases with the number of oxalato ligands bound to the metal ion.     

Electrospray identification of new polyoxochromate species

Electrospray ionization mass spectrometry (ESI MS) has been conducted on the ammonium and alkali metal (A=Li⁺, Na⁺ and K⁺) dichromate systems. A large number of previously unknown polyoxochromate species have been characterized. Major series that have been identified include [A_x+1H_xCr^VI_xO_4x]⁺ (Li⁺, x=1-5; Na⁺, x=1-7; K⁺, x=1-4) and [A_2x−1Cr^VI_xO_4x−1]⁺ (Li⁺, x=2, 3; Na⁺, x=2-4; K⁺, x=2, 3) in the alkali metal dichromate systems, and [HCr^VI_xO_3x+1]⁻ (x=1-5) in the ammonium dichromate system. Several series also contain mixed oxidation state species, ranging from Cr(V) to Cr(II) in conjunction with Cr(VI), which is consistent with the ease of reduction of Cr(VI). Negative ion ESI MS spectra clearly demonstrate the existence of [HCrO₄]⁻ as the most abundant ion at −20 V, suggesting that its existence in solution is not just hypothetical, as was previously thought. The polymerization units for the series observed include {AHCrO₄}, {A₂CrO₄} and {CrO₃}, with the latter prominent in the alkali metal systems. This presumably arises from the fragmentation of dichromate, A₂Cr₂O₇→{A₂CrO₄}+{CrO₃}. Moreover, the ESI MS of the dichromate compounds have illustrated that the preservation of tetrahedral stereochemistry is of paramount importance for these systems, which leads to only limited polymerization compared to the related molybdate and tungstate systems.     

Complexes of [Re(CO)3Cl] with different oxidation states of the polyfunctional bmtz/H2bmtz ligand system (bmtz=3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine)

Combining fac-[Re(CO)₃Cl] with components of the ligand redox system bmtz/bmtz⁻/H₂bmtz/H₂bmtz⁻ (bmtz=3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine) has led to the isolation of the complexes (H₂bmtz)Re(CO)₃Cl, (μ-H₂bmtz)[Re(CO)₃Cl]₂ and (μ-bmtz)[Re(CO)₃Cl]₂. Other species characterized were (bmtz)Re(CO)₃Cl (UV/Vis, IR), [(H₂bmtz)Re(CO)₃Cl]⁻ (UV/Vis, IR, EPR), {(μ-H₂bmtz)[Re(CO)₃Cl]₂}⁻ (UV/Vis, IR, EPR) and {(μ-bmtz)[Re(CO)₃Cl]₂}⁻ (UV/Vis, IR, X band and high-field EPR). The results confirm bmtz as very strong and H₂bmtz as moderate π acceptor ligand versus one or two chelate-bonded low-valent metal centers. Reactivity is observed in terms of oxidative proton and reductive chloride dissociation.     

Theoretical calculations on a series of dinuclear vanadium and niobium clusters

Electronic structures of chalcogenide-bridged binuclear clusters of vanadium and niobium with the {M₂(μ-Q₂)₂}⁴⁺, {M₂(μ-Q)₂}⁴⁺ and {M₂(μ-Q)(μ-Q)₂}⁴⁺ cores (Q = S, Se, Te) have been studied by density functional theory methods. In the vanadium clusters, the V-V distances are calculated to be in the range of 2.766-3.193 ?, whereas in the niobium clusters the calculated Nb-Nb bond lengths fall in the range of 2.881-3.380 ?, in accordance with the experimentally determined values. The calculated M-M bond distances generally decrease in the order {M₂(μ-Q₂)₂}⁴⁺ > {M₂(μ-Q)₂}⁴⁺ > {M₂(μ-Q)(μ-Q)₂}⁴⁺ (M = V, Nb, Q = S, Se). The calculated enthalpies of formation for the V clusters are higher than for the corresponding Nb clusters. On the other hand, the M₂Q₂ clusters have always higher enthalpies of formation than the M₂Q₃ species, and also (with the exception of M = V, Q = S) higher values of enthalpy of formation than for the M₂Q₄ species. The hardness η of the niobium clusters are higher than that of the vanadium analogs, except for the [V₂S₂(SH₂)₈]⁴⁺ case. The enthalpies ΔH₂₉₈ and the free energies ΔG₂₉₈ for the reactions of hydrogen addition to the [V₂(μ-S₂)₂(H₂O)₈]⁴⁺ and the [Nb₂(μ-S₂)₂(H₂O)₈]⁴⁺ clusters at constant pressure are −121.75 and −59.73 kJ/mol for the vanadium cluster, and 13.97 and 75.15 kJ/mol for the niobium cluster.     

Syntheses and structures of Group 12 metal thioacetate anions, [M(SC{O}Me)nCl4−n] (n=3 and 4) and [Cd2Cl2(SC{O}Me)4]

We have utilized the possibility of altering the ratio of reactants to result in tetrahedral anions, [M(SC{O}Me)_nCl_4−n]²⁻ (n=3, 4) and [Cd₂Cl₂(SC{O}Me)₄]²⁻. Complexes of the formula [Ph₄P]₂[M(SC{O}Me)₄] (M=Zn(II) (1), Cd(II) (2) or Hg(II) (3)) were synthesized by the reaction of thioacetate ligand with the metal salts and Ph₄PCl in 4:1:2 molar ratio in suitable solvents. The geometry of Zn(II) in 1 is nearly tetrahedral and the distortion in tetrahedron increases in the order of 1<2<3 as observed from the SMS angles in the crystal structures. The tendency of monoanionic complexes [Ph₄P][M(SC{O}Me)₃] to react with 1 mole equivalent of Ph₄PCl resulted in complexes of the type [Ph₄P]₂[M(SC{O}Me)₃Cl] (M=Cd(II) (4) or Hg(II) (5)). In the structures of 4 and 5, three sulfur atoms and one chloride atom occupy the corners of the tetrahedron around the metal centers. However, in a 4:2:2 or 2:1:2 molar reaction of Me{O}CS⁻ with CdCl₂ and Ph₄PCl in aqueous medium resulted in a chloro bridged dimer, [Ph₄P]₂[Cd₂(μ-Cl)₂(SC{O}Me)₄] (6) as determined by X-ray crystallography.     

Mixed chloride-phosphine complexes of the dirhenium core. Part 11. Reactions of [Re2Cl8] with secondary phosphines, PCy2H and PPh2H

The reaction between the dirhenium(III,III) anion, [Re₂Cl₈]²⁻, and the secondary phosphine, PCy₂H, yields a mixture of products as a result of disproportionation, namely, a dirhenium(II,III) chloride-phosphine complex 1,3,6-Re₂Cl₅(PCy₂H)₃ (1) and a dirhenium(IV) face-sharing bioctahedral compound with bridging phosphido groups, [Buⁿ ₄N][Re₂(μ-PCy₂)₃Cl₆] (2). The diphenylphosphine analogue of 2, [Buⁿ ₄N][Re₂(μ-PPh₂)₃Cl₆] (3) has been similarly prepared from the reaction of [Re₂Cl₈]²⁻ with PPh₂H. An interesting dirhenium(III,III) complex, [Buⁿ ₄N]₂[Re₂(μ-PPh₂)₂(PPh₂H)₂Cl₆] (4) having both neutral terminal phosphines and anionic phosphido bridges, has also been isolated as an intermediate in the latter system. Crystal structures of 1-4 have been determined by X-ray crystallography. The compounds were also characterized by cyclic voltammetry, IR and ³¹P NMR spectroscopy.     

Studies of rheniumtricarbonyl complexes of tripodal pyridyl-based ligands

The reaction of N-benzoyl and N-acetyl tris(pyridin-2-yl)methylamine 1b and 1c (LH = tpmbaH and tpmaaH) with [Re(CO)₅Br] has been investigated and shown to proceed via the initial formation of a cationic rheniumtricarbonyl complex [(LH)Re(CO)₃]Br in which coordination of the ligand occurs via the three pyridine rings. For tpmbaH 1b, but not tpmaaH 1c, this initial complex 2b readily undergoes the loss of HBr to give a neutral octahedral complex 4b [(L)Re(CO)₃] where coordination occurs via two of the pyridine rings and the deprotonated amide nitrogen. The ¹H NMR spectrum of the latter complex 4b is very unusual in that at room temperature the signals for the 3-H protons on the coordinated pyridine rings are not visible due to extreme broadening of these resonances. Comparison with the analogous complex 7 from N-benzoyl bis(pyridin-2-yl)methylamine 6b (bpmbaH) confirms that this is due to rotation of the uncoordinated pyridine ring. The structure of the cationic complex 3d [(LH)Re(CO)₃]Br formed from N-benzyl tris(pyridin-2-yl)methylamine 1d (bz-tpmaH) is also discussed. The crystal structures of complexes [(tpmba)Re(CO)₃] 4b, [(bz-tpmaH)Re(CO)₃]Br 3d and [(bpmba)Re(CO)₃] 7 have been determined. In all complexes the coordination geometry around Re is distorted octahedral with a fac-{Re(CO)₃}⁺ core.