Molybdenum doubly bridged and chelate nitrosyl complexes incorporating saturated n-alkanediolate ligands

The redox-active doubly bridged species [{Mo(NO)(Tp^Me2)Q}₂] [Tp^Me2 = tris(3,5-dimethylpyrazol-1-yl)hydroborate, Q = O(CH₂)_nO, n = 3, 5, or OCH₂(CF₂)_n−2CH₂O, n = 5, 6], and a chelate complex [Mo(NO)-(Tp^Me2)O(CH₂)₅O] were prepared and characterised by elemental and mass analyses, ¹H NMR and IR spectroscopy. The bimetallic species with C₃, C₅, and C₅(F) bridges exhibit two well-resolved reduction processes in their cyclic voltammograms (ΔE_1/2 values of 290, 170, and 170 mV, respectively). These results indicate that the presence of the second bridge increases the extent of electrochemical interactions (by ca. 90-130 mV) in comparison with their singly bridged analogues. All non-fluorinated and the chelate species were catalytically active in cathodic reduction of chloroform.     

Synthesis, characterisation and crystal structure of hydroxylamido-κN,O(iodo)[tris(3,5-dimethylpyrazol-1-yl)borato]nitrosylmolybdenum(II)

The unusual 18e seven-coordinate Mo(II) complex [Mo(NO)(H₂NO-κ²N,O)(Tp^Me2)I] (1; [Tp^Me2]⁻ is hydrotris(3,5-dimethylpyrazol-1-yl)borate) has been synthesised and characterised by IR, ¹H NMR and ESI-MS spectroscopies and by a single crystal X-ray diffraction study. The complex has a distorted pentagonal bipyramid structure with equatorial κ²-NH₂O⁻ ligand (d_N-O = 1.387 Å, d_Mo-N and d_Mo-O equal 2.049 and 2.092 Å, respectively). In the solid state 1 exists as a dimer (the point group C_i) due to the formation of two NH?O hydrogen bonds (d_N-H?O = 2.064 Å) between the adjacent NH₂O⁻ ligands, whilst in solution at/or above RT it resolves itself giving a monomer, which readily isomerises to more thermodynamically stable diastereoisomer.     

Heteroleptic lanthanide terphenyl/tris(pyrazolyl)borate compounds of ytterbium

The synthesis and structural characterization of the two novel unsolvated heteroleptic ytterbium compounds DanipYb(Tp^Me,Me)Cl (1) and DanipYb(Tp^Me,Me)CH₂SiMe₃ (2) by simple salt metathesis reaction is reported [Danip = 2,6-di(o-anisol)phenyl); Tp^Me,Me = hydrotris(3,5-dimethyl-pyrazolyl)borate]. In the molecular structure of 2 a flexible bonding mode of the donor-functionalized terphenylic ligand is observed.     

Isovalent and mixed-valent molybdenum complexes containing Mo(μ-E)(μ-S2)Mo (E = O, S) core units

The reactions of Tp^iPrMoO(SR)(NCMe) (Tp^iPr = hydrotris(3-isopropylpyrazolyl)borate) with propylene sulfide in toluene result in the formation of the diamagnetic, isovalent Mo(V) complex, [Tp^iPrMo^VO]₂(μ-S)(μ-S₂). This complex and its previously reported μ-oxo analog, [Tp^iPrMo^VO]₂(μ-O)(μ-S₂), react with cobaltocene to produce one-electron-reduced, mixed-valent complexes, [CoCp₂][{Tp^iPrMo^IV,VO}₂(μ-E)(μ-S₂)] (E = S or O, respectively). All complexes have been isolated and characterized by microanalysis, mass spectrometry, IR and ¹H NMR or EPR spectroscopies, and X-ray crystallography. Neutral [Tp^iPrMo^VO]₂(μ-S)(μ-S₂) exhibits a pseudo-C₂ symmetric structure, with distorted octahedral anti oxo-Mo(IV) centers coordinated by Tp^iPr and linked by μ-sulfido and μ-disulfido ligands. A similar structure is adopted by the anion in mixed-valent [CoCp₂][{Tp^iPrMo^IV,VO}₂(μ-S)(μ-S₂)]; this compound adopts a hexagonal, supramolecular structure with columns of tight ion-pairs with interactions, interconnected through weaker contacts to three neighboring columns. The structure contains large interstitial voids filled with lattice solvent molecules. EPR investigation of the mixed-valent complexes gave rise to unusually broad signals with no evident hyperfine splitting. The synthesis and characterization of a number of cis-dioxo-Mo(VI) precursors are also reported.     

Synthesis and isocyanate insertion reactions of tungsten(IV) imido complexes formed from W(CO)(acac)(N3)(PMe3)3 with azide as the oxidant

Addition of excess trimethylphosphine and a halide source to a solution of W(CO)(acac)₂(η²-L) (L = NCPh and OCMe₂) leads to displacement of L and one acetylacetonate chelate to produce electron-rich, seven-coordinate complexes of the formula W(CO)(acac)(X)(PMe₃)₃ (X = Cl, Br, and I). Use of NaN₃ instead of a halide source leads primarily to loss of carbon monoxide and dinitrogen, and protonation from adventitious water yields the cationic imido complex [W(NH)(acac)(PMe₃)₃]⁺. Heating [W(NH)(acac)(PMe₃)₃]⁺ in aromatic isocyanates at high temperature results in isocyanate insertion into the NH imido bond to form new C-N bonds. An alternate route to related imido complexes involves heating [W(O)(acac)(PMe₃)₃]⁺ with phenyl isocyanate at high temperatures to yield the substituted imido complex [W(NPh)(acac)(PMe₃)₃]⁺.     

Insertion of heteroallenes into the rhenium-hydride bond

Dithioformato [Re{η²-SC(H)S}(NO)P₃]BPh₄ (1), thioformamido [Re{η²-RNC(H)S}(NO)P₃]BPh₄ (2) (R = Et, p-tolyl), formamido [Re{η²-PhNC(H)O}(NO)P₃]BPh₄ (3) and formamidinato [Re{η²-p-tolylNC(H)Np-tolyl}(NO)P₃]BPh₄ (4) (P = PPh₂OEt) complexes were prepared by allowing the hydride ReH₂(NO)P₃ to react first with triflic acid and then with the appropriate heteroallene CS₂, RNCS, PhNCO and p-tolylNCNp-tolyl. Treatment of the ReH₂(NO)L(PPh₃)₂ [L = P(OEt)₃, PPh(OEt)₂] and ReH₂(NO)(PPh₃)₃ hydrides first with triflic acid and then with isothiocyanate RNCS (R = Et, p-tolyl) gave the [Re{η²-RNC(H)S}(NO){P(OEt)₃}(PPh₃)₂]BPh₄ (5, 6) and [Re(η²-RNC(H)S)(NO)(PPh₃)₃]BPh₄ (7) derivatives. Depending on the nature of the phosphite, instead, the reaction of ReH₂(NO)L(PPh₃)₂ and ReH₂(NO)(PPh₃)₃ hydrides first with CF₃SO₃H and then with isocyanate R1NCO (R1 = Ph, p-tolyl) gave the chelate [Re{η²-R1NC(H)O}(NO){P(OEt)₃}(PPh₃)₂]BPh₄ (8) and [Re{η²-R1NC(H)O}(NO)(PPh₃)₃]BPh₄(10) complexes with P(OEt)₃ or PPh₃, while the η¹-coordinate [Re{η¹-RNC(H)S}(NO){PPh(OEt)₂}₂(PPh₃)₂]BPh₄ (9) derivative was obtained with the PPh(OEt)₂ phosphite ligand. η¹-Coordinate dithioformato [Re{η¹-SC(H)S}(NO){PPh(OEt)₂}₂(PPh₃)₂]BPh₄ (11) and formato [Re{η¹-OC(H)O}(NO){PPh(OEt)₂}₂(PPh₃)₂]BPh₄ (12) complexes, as well as the formamidinato [Re{η²-p-tolylNC(H)Np-tolyl}(NO){P(OEt)₃}(PPh₃)₂]BPh₄ (13) derivative were also prepared.     

Synthesis of dimethylcobalt(III) complexes containing trimethylphosphine and 2-formyl-phenolato- or 2-formyl-enolato(O:O) ligands

Substituted salicylaldehydes [C₆HR¹R²R³(CHO)(OH)] react with CoMe₃(PMe₃)₃ to afford 6-coordinate (cis-dimethyl)(2-formyl-phenolato)trans-bis(trimethylphosphine)cobalt(III) compounds Co[C₆HR¹R²R³(CHO)(O)Me₂](PMe₃)₂ (1: R¹ = H; R² = Me; R³ = tert-Bu; 2: R¹, R² = C₆H₄; R³ = H). Accordingly, substituted enolated malonic dialdehydes (CHO-CR⁴CR⁵-OH) react with CoMe₃(PMe₃)₃ to afford 6-coordinate (cis-dimethyl)(2-formyl-enolato)trans-bis(trimethylphosphine)cobalt(III) compounds Co[(CHO-CR⁴CR⁵-O)(Me)₂](PMe₃)₂ (3: R⁴, R⁵ = (CH₂)₂C₆H₄; 4: R⁴ = R⁵ = C₆H₅). In the molecular structure of 4, the cobalt atom is centred in an octahedral coordination geometry brought about by a six-membered chelate ring (O:O-ligand), cis-dimethyl and trans-trimethylphosphine groups. A reaction mechanism is suggested.     

A new tris(2-furyl) substituted pyrazolylborate ligand and its zinc complex chemistry

The new ligand hydrotris(3-(2′-furyl)-5-methylpyrazolyl)borate (Tp^Fu,Me) was prepared by the usual procedure. With zinc salts, it forms the Tp^Fu,MeZn-X complexes (X = Cl, Br, I, NCS, CH₃COO, CF₃COO). With zinc perchlorate, the bis-ligand complex Zn(Tp^Fu,Me)₂ is formed preferrably, but by carefully controlling the reaction conditions, the “enzyme model” Tp^Fu,MeZn-OH could be obtained. The latter models carbonic anhydrase by inserting CO₂ and CS₂ in methanol producing Tp^Fu,MeZn-OCOOMe and Tp^Fu,MeZn-SCSOMe. It models hydrolases by the hydrolytic cleavage of tris(p-nitrophenyl)phosphate and γ-thiobutyrolactone. It does not hydrolyse trifluoroacetamide, but instead deprotonates it, yielding Tp^Fu,MeZn-NHCOCF₃.     

Controlled nitric oxide photo-release from nitro ruthenium complexes: The vasodilator response produced by UV light irradiation

Preliminary pharmacological studies of various nitric oxide (NO) photo-releasing agents are reported based on the flash-photolysis studies of the nitro ruthenium complexes cis-[Ru^II(NO₂)L(bpy)₂]⁺ (bpy = 2,2′-bipyridine and L = pyridine, 4-picoline and pyrazine) and [Ru^II(NO₂)(bpy)(terpy)]⁺ (terpy = terpyridine) in physiological medium. The net photoreactions under these conditions are two primary photoproducts, in (I) there is Ru^II-NO₂ photoaquation, where the photoproducts are Ru^II-H₂O plus and (II) homolytic dissociation of NO from a coordinated nitrito to derive the Ru^II-OH₂ specie and NO. Based on photochemical processes, the nitro ruthenium complexes were incorporated in water in oil (W/O) microemulsion and used in the vasorelaxation induced experiment. Denuded rat aortas were contracted with KCl and nitro ruthenium complexes in microemulsion were added. Perfusion pressures were recorded while arteries were irradiated at 355 nm The time to reach maximum relaxation was longer for [Ru^II(NO₂)(bpy)(terpy)]⁺ complex (ca. 50 min, n = 6) than for cis-[Ru(NO₂)L(bpy)₂]⁺ with L = py and 4-pic complex (ca. 28 min, n = 6) and cis-[Ru(NO₂)(bpy)₂ (pz)]²⁺ complex (ca. 24 min, n = 5).     

Preparation of benzophenone imine complexes of transition metals

Benzophenone imine [M(η¹-NHCPh₂)(CO)_nP_5-n]BPh₄ [M = Mn, Re; n = 2, 3; P = P(OEt)₃, PPh(OEt)₂, PPh₂OEt, PPh₃] complexes were prepared by allowing triflate M(κ¹-OTf)(CO)_nP_5-n compounds to react with an excess of the imine. Hydride-imine [MH(η¹-NHCPh₂)P₄]BPh₄ (M = Ru, Os), triflate-imine [Os(κ¹-OTf)(η¹-NHCPh₂)P₄]BPh₄ and bis(imine) [Ru(η¹-NHCPh₂)₂P₄](BPh₄)₂ [P = P(OEt)₃] derivatives were also prepared. The complexes were characterized spectroscopically (IR, ¹H, ³¹P, ¹³C NMR) and a geometry in solution was also established. Hydride-benzophenone imine [IrHCl(η¹-NHCPh₂)L(PPh₃)₂]BPh₄and [IrHCl(η¹-NHCPh₂)L(AsPh₃)₂]BPh₄ [L = P(OEt)₃ and PPh(OEt)₂] complexes were prepared by reacting hydride IrHCl₂L(PPh₃)₂ and IrHCl₂L(AsPh₃)₂ precursors with an excess of imine. Dihydride IrH₂(η¹-NHCPh₂)(PPh₃)₃ complex was also obtained and a geometry in solution was proposed.     

Synthesis and characterization of sterically hindered tris(pyrazolyl)borate Ni complexes

Addition of KTp^Ph2 to a solution of NiX₂ (X = Cl, Br, NO₃, OAc and acac) or NiBr(NO)(PPh₃)₂ in THF yields the structurally characterized series [NiCl(Hpz^Ph2)Tp^Ph2] (1) and [NiXTp^Ph2] (X = Br 2, NO 3, NO₃4, OAc 5 and acac 6) including the first example of a tris(pyrazolyl)borate nickel nitrosyl complex. IR spectroscopy confirms that all the Tp^Ph2 ligands are κ³ coordinated and that the NO ligand in 3 is linearly bound. Electronic spectra are consistent with four- or five-coordinate species in solution. NMR spectroscopic studies indicate that the complexes are paramagnetic, with the exception of 3. This is confirmed by magnetic susceptibility studies, which suggest that complexes 1, 2 and 4-6 are paramagnetic with two unpaired electrons. X-ray crystallographic studies of 5 reveal a distorted trigonal bipyramidal nickel centre with a symmetrically coordinated acetate ligand.     

Properties of homo- and heteronuclear mixed biscarbene complexes with conjugated bithiophene units

The syntheses and structures of homo- and heteronuclear biscarbene complexes with bithiophene spacers were investigated. The complexes were synthesized by lithiation of bithiophene followed by metallation using combinations of the metal precursors MnMeCp(CO)₃, W(CO)₆, Mo(CO)₆ and Cr(CO)₆, after which the reaction was quenched with triethyloxonium tetrafluoroborate. This classical Fischer method yielded monocarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₃S], ([ML_n] = Cr(CO)₅1a, W(CO)₅2a or MnMeCp(CO)₂3a), homonuclear biscarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₂SC(OEt)ML_n], ([ML_n] = Cr(CO)₅1b, W(CO)₅2b or MnMeCp(CO)₂3b) and heteronuclear biscarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₂SC(OEt)M′L_n] (1d: [ML_n] = Cr(CO)₅ and [M′L_n] = W(CO)₅; 1e: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = Cr(CO)₅; 1f: [ML_n] = Cr(CO)₅ and [M′] = Mo(CO)₅); 2d: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = W(CO)₅; 3c: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = Mo(CO)₅). Electron density calculations with the gaussian03 software package of 1e revealed a polar rod with the negative pole towards the chromium carbene side, whereas the biscarbenes 1d and 1b showed very little polarity. By-products resulting from activation of the carbene moieties in homonuclear biscarbene complexes included (i) ester-type complexes of the form [ML_nC(OEt)C₄H₂S-C₄H₂SC(O)OEt], ([ML_n] = Cr(CO)₅1c or W(CO)₅2c), formed in situ in the reaction of 1b and 2b, (ii) the organic bis-ester compound [EtOC(O)C₄H₂S-C₄H₂SC(O)OEt] 4, where both metal moieties had been substituted by oxygen and (iii) the carbon-carbon coupled dimeric bithienyl compound [C₄H₃S-C₄H₂SC(O)C(O)C₄H₂S-C₄H₃S] 5. By-products obtained from heteronuclear biscarbene reactions contain the former diketo compound (or a derivative) as spacer between two metal carbonyl fragments and have the general formula [ML_nC(OEt)C₄H₂S-C₄H₂SCR-CR′C₄H₂S-C₄H₂SC(OEt)ML_n] (5a: [M] = Cr(CO)₅, R = OH, R′ = OEt; 5b: [M] = W(CO)₅, R = R′ = O; 5c: [M] = Mo(CO)₅, R = R′ = O). Reaction of 1d, 1e and 1f with hex-3-yne resulted in the formation of benzannulated products 6a, 6b and 6c. All novel complexes were fully characterized using various spectroscopic techniques. The crystal structures of 1b, 2a and 5 are reported.     

Magnesium (II) poly(pyrazolyl)borate derivatives - Synthesis, spectral and structural studies

A series of magnesium complexes of general formula [Mg(Tp^x)₂] (Tp^x = Tp, Tp^∗, Tp^∗Cl, pzTp) and [Mg(Tp^x)X] (X = Cl, Tp^x = Tp^tBu or pz⁰Tp^p-Tol; X = acetate, Tp^x = Tp^tBu) were synthesised from magnesium chloride or acetate and M(Tp^x) (M = K, Na or Tl) in dichloromethane or alcoholic solution. These compounds are air-stable solids, sparingly soluble in most organic solvents; they have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectra and, in selected cases, also by conductivity and molecular weight measurements. Single crystal X-ray diffraction studies of [Mg(Tp)₂], [Mg(Tp*)₂] and [Mg(Tp*^Cl)₂] show unsolvated neutral bis(tripod ligand)magnesium(II) molecules with six-coordinate magnesium atoms (〈Mg-N〉 2.167(6), 2.19(2), 2.205(4) Å).     

Diiron and diruthenium aminocarbyne complexes containing pseudohalides: stereochemistry and reactivity

Acetonitrile is easily displaced from [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] (R = 2,6-Me₂C₆H₃ (Xyl) (1a); Me (1b)) upon stirring in THF at room temperature in the presence of [NBu₄][SCN]. The resulting complexes trans-[Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)₂] (R = Xyl (trans-2a); Me (trans-2b)) are completely isomerised to cis-[Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)₂] (R = Xyl (cis-2a); Me (cis-2b)) when heated at reflux temperature. Similarly, the complexes cis-[M₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCO)(Cp)₂] (M = Fe, R = Me (4a); M = Ru, R = Xyl (4b); M = Ru, R = Me (4c)) and cis-[M₂{μ-CN(Me)(R)}(μ-CO)(CO)(N₃)(Cp)₂] (M = Fe, R = Xyl (5a); M = Fe, R = Me (5b); M = Ru, R = Xyl (5c)) can be obtained by heating at reflux temperature a THF solution of [M₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] (M = Fe, R = Xyl (1a); M = Fe, Me (1b); M = Ru, R = Xyl (1c); M = Ru, R = Me (1d)) in the presence of NaNCO and NaN₃, respectively. The reactions of 5 with MeO₂CCCCO₂Me, HCCCO₂Me and (NC)(H)CC(H)(CN) afford the triazolato complexes [M₂{μ-CN(Me)(R)}(μ-CO)(CO){N₃C₂(CO₂Me)₂}(Cp)₂] (M = Fe, R = Xyl (6a); M = Fe, R = Me (6b); M = Ru, R = Xyl (6c)), [M₂{μ-CN(Me)(R)}(μ- CO)(CO){N₃C₂(H)(CO₂Me)}(Cp)₂] (M = Fe, R = Me (7a); M = Ru, R = Xyl (7b)) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃C₂(H)(CN)}(Cp)₂] (8), respectively. The asymmetrically substituted triazolato complexes 7-8 are obtained as mixtures of N(1) and N(2) bonded isomers, whereas 6 exists only in the N(2) form. Methylation of 6-8 results in the formation of the triazole complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃(Me)C₂(CO₂Me)₂}(Cp)₂][CF₃SO₃] (9), [M₂{μ-CN(Me)(R)}(μ-CO)(CO){N₃(Me)C₂(H)(CO₂Me)}(Cp)₂][CF₃SO₃] (M = Fe, R = Me (10a); M = Ru, R = Xyl (10b)) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃(Me)C₂(H)(CN)}(Cp)₂][CF₃SO₃], 11. The crystal structures of trans-2b, 4b · CH₂Cl₂, 5a, 6b · 0.5CH₂Cl₂ and 8 · CH₂Cl₂ have been determined.     

1,2-Borotropic shifts and B-N bond cleavage reactions in molybdenum hydrotris(3-isopropylpyrazolyl)borate chemistry: Mixed-valence MoMo2 and pyrazole-rich oxo-Mo complexes

Red-black [Tp^iPr∗Mo^VO]₂(μ-O)(μ-Mo^VIO₄) (1, Tp^iPr∗ = hydrobis(3-isopropylpyrazolyl)(5-isopropylpyrazolyl)borate) has been isolated as a by-product in the synthesis of NEt₄[Tp^iPrMo(CO)₃] (Tp^iPr = hydrotris(3-isopropylpyrazolyl)borate) and characterized by spectroscopic and X-ray crystallographic techniques. The trinuclear, mixed-valence complex contains two distorted octahedral anti-Tp^iPr∗Mo^VO centers bridged by bent oxo (Mo-O-Mo av. 158.7°) and tetrahedral κO,κO′-molybdate ligands. The complex contains a six-membered, non-planar Mo₃(μ-O)₃ core and two 1,2-borotropically-shifted Tp^iPr∗ ligands (with the shifted pyrazolyl trans to Mo^V=O). Aerial decomposition of solid NEt₄[Tp^iPrMo(CO)₃] produces sky-blue, diamagnetic Tp^iPrMoO(ⁱPrpz)(ⁱPrpzH) (2, ⁱPrpz^- = 3-isopropylpyrazolate, ⁱPrpzH = 3-isopropyl-2H-pyrazole). Molecules of 2 feature a tridentate fac-Tp^iPr ligand and mutually cis terminal oxo (MoO = 1.665(2) Å) and monodentate ⁱPrpz⁻ and ⁱPrpzH ligands. The latter are formed by B-N bond cleavage of Tp^iPr. The complex can also be synthesized by reacting NEt₄[Tp^iPrMo(CO)₃] with excess 3-isopropylpyrazole and dioxygen at 100 °C. Cleavage of the B-N bond(s) of Tp^iPr was also observed in the formation of Tp^iPrMoO(SPh)(ⁱPrpzH) (3) as a by-product in the synthesis of Tp^iPrMoO₂(SPh). In the monohydrate, 3 exhibits a distorted octahedral geometry defined by a tridentate fac-Tp^iPr ligand and mutually cis terminal oxo (MoO = 1.676(3) Å) and monodentate SPh⁻ and ⁱPrpzH ligands. The pyrazole β-NH group is observed to participate in a hydrogen-bond to the lattice water molecule. The complex can be synthesized in high yield by reducing Tp^iPrMoO₂(SPh) by HSPh or PPh₃ in the presence of excess 3-isopropylpyrazole.     

Synthesis and reactivity of cationic bipyridine tungsten(0) and molybdenum(0) nitrosyl complexes

A variety of Group 6 mono bipyridine (bpy) complexes were prepared, and substitution reactions of [(bpy)(MeIm)M(CO)₂(NO)]PF₆ complexes (MeIm = 1-methylimidazole, M = W or Mo) were investigated. Nitrosylation of complexes having the general formula (bpy)(L)M(CO)₃ (L = a variable ligand) gave cationic complexes of the form [(bpy)(L)M(CO)₂(NO)]PF₆. The structure of [(bpy)(MeIm)W(CO)₂(NO)]PF₆ was confirmed by single-crystal X-ray diffractometry. [(bpy)(MeIm)M(CO)₂(NO)]PF₆ complexes undergo facile substitutions with mono-, tri- and tetra-dentate ligands, yielding di- or mono-carbonyl mononitrosyl complexes. The structures of [(bpy)(PMe₃)₂W(CO)(NO)]PF₆ and [(dien)(PMe₃)W(CO)(NO)]PF₆ (dien = diethylenetriamine) were determined by X-ray diffraction.     

Syntheses, crystal structures, and characterization of heteronuclear complexes based on a versatile ligand with both acetylacetonate and bis(2-pyridyl) units

A new type of multidentate ligand with both acetylacetonate and bis(2-pyridyl) units on the 1,3-dithiole moiety, 3-[2-(dipyridin-2-yl-methylene)-5-methylsulfanyl-[1,3]dithiol-4-ylsulfanyl]-pentane-2, 4-dione (L), has been prepared. Through reactions of the ligand with Re(CO)₅X (X = Cl, Br), new rhenium(I) tricarbonyl complexes ClRe(CO)₃(L) (2) and BrRe(CO)₃(L) (3), have been obtained. With the use of 2 or 3 as the precursors, the further reactions with (Tp^Ph2)Co(OAc)(Hpz^Ph2) (Tp^Ph2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate); Hpz^Ph2 = 3,5-diphenyl-pyrazole) or M(OAc)₂(M = Mn, Zn), afford four new heteronuclear complexes: ClRe(CO)₃(L)Co(Tp^Ph2) (4), BrRe(CO)₃(L)Co(Tp^Ph2) (5), [ClRe(CO)₃(L)]₂Mn(CH₃OH)₂ (6) and [ClRe(CO)₃(L)]₂Zn(CH₃OH)₂ (7), respectively. Crystal structures of complexes 2 and 4-7 have been determined by X-ray diffraction. Their absorption spectra, photoluminescence and magnetic properties have been studied.     

Structure and solution behaviour of cyclooctadiene complexes of platinum(II)

The substitution behaviour of [PtCl(R)(COD)] (R⁻ = Me and Fc) complexes, by the stepwise addition of phosphine ligands, L (L = PPh₃, PEt₃ and P(NMe₂)₃), were investigated in situ by ¹H and ³¹P NMR spectroscopy. Addition of less than two equivalents of the phosphine ligand results in the formation of dimeric molecules with the general formula trans-[Pt(R)(μ-Cl)(L)]₂ for the sterically demanding systems where R⁻ = Me/L = P(NMe₂)₃ and R⁻ = Fc/L = PEt₃, PPh₃ and P(NMe₂)₃ while larger quantities resulted in cis- and trans mixtures of mononuclear complexes being formed. In the case of the relatively small steric demanding, strongly coordinating, PEt₃ ligand the trans-[PtCl(R)(PEt₃)₂] mononuclear complexes were exclusively observed in both cases. The crystal structures of the two substrates, [PtCl(R)(COD)] (R⁻ = Me or Fc), as well as the cis-[PtCl(Fc)(PPh₃)₂] substitution product are reported.     

Quantification of cis and trans influences in [PtX(PPh3)3] complexes. A P NMR study

In [PtX(PPh₃)₃]⁺ complexes (X = F, Cl, Br, I, AcO, NO₃, NO₂, H, Me) the mutual cis and trans influences of the PPh₃ groups can be considered constants in the first place, therefore the one bond Pt-P coupling constants of P_(cis) and P_(trans) reflect the cis and trans influences of X. The compounds [PtBr(PPh₃)₃](BF₄) (2), [PtI(PPh₃)₃](BF₄) (3), [Pt(AcO)(PPh₃)₃](BF₄) (4), [Pt(NO₃)(PPh₃)₃](BF₄) (5), and the two isomers [Pt(NO₂-O)(PPh₃)₃](BF₄) (6a) and [Pt(NO₂-N)(PPh₃)₃](BF₄) (6b) have been newly synthesised and the crystal structures of 2 and 4·CH₂Cl₂·0.25C₃H₆O have been determined. From the ¹J_PtP values of all compounds we have deduced the series: I > Br > Cl > NO₃ > ONO > F > AcO > NO₂ > H > Me (cis influence) and Me > H > NO₂ > AcO > I > ONO > Br > Cl > F > NO₃ (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh₃)₂] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X = Cl, were found to depend on the charge and nature of the complex.     

A high-spin Fe(II)/low-spin Fe(III) redox couple featuring the hydro[tris(4-chloro-3,5-dimethyl-pyrazolyl)]borate ligand: Synthesis, spectroscopic and X-ray crystallographic characterization

The white homoleptic high-spin iron(II) complexes Fe[Tp^Me2,4Cl]₂ (1) was isolated in quantitative yield from reaction mixtures containing 1 equiv of FeCl₂(THF)_1.5 and 2 equiv of K[Tp^Me2,4Cl] (Tp^Me2,4Cl = hydrotris[(4-chloro-3,5-dimethyl-pyrazolyl)]borate). Its purple low-spin iron(III) counterparts 1[O₃SCF₃] and 1[PF₆] were synthesized and isolated in 85% yields upon treatment of 1 with 1 equiv of silver triflate and silver hexafluorophosphate, respectively. The three paramagnetic compounds are air and thermally stable as solids and in solution; they were characterized by elemental analyses, IR, magnetic susceptibility measurements, ¹H NMR, and Mössbauer spectroscopy. In addition, 1[PF₆] was authenticated by a single-crystal X-ray diffraction. The two scorpionate ligands are κ³-N,N′,N′′ ligated to the central Fe^III ion, forming an almost perfect FeN₆ octahedron with an average Fe-N bond distance of 1.9551(18) Å. In addition, complex 1 which oxidizes reversibly at E_1/2 = 0.483 V/SCE (ΔE_p = 94 mV), remains high-spin (S = 2) when the temperature is lowered to 2 K.