Rhenium(V) oxocomplexes with novel pyrazolyl-based N4- and N3S-donor chelators

The novel pyrazolyl-based ligands 3,5-Me2pz(CH2)2NH(CH2)2NH(CH2)2NH2 and pz*(CH2)2NH-Gly-CH2STrit (pz*=pz, 3,5-Me2pz, 4-(EtOOC)CH(2)-3,5-Me2pz) were synthesized, and their suitability to stabilize Re(V) oxocomplexes was evaluated using different starting materials, namely (NBu4)[ReOCl4], [ReOCl3(PPh3)2] and trans-[ReO2(py)4]Cl. Compound reacts with trans-[ReO2(py)4]Cl yielding the cationic compound [ReO(OMe){3,5-Me2pz(CH2)2N(CH2)2NH(CH2)2NH2}](BPh4) in a low isolated yield. In contrast, the neutral complexes [ReO{pz*(CH2)2NH-Gly-CH2S}] (pz*=pz, 3,5-Me2pz, 4-(EtOOCCH2)-3,5-Me2pz) were synthesized almost quantitatively by reacting [ReOCl3(PPh3)2] or (NBu4)[ReOCl4] with the trityl-protected chelators. The X-ray diffraction analysis of and confirmed the tetradentate coordination mode of the respective ancillary ligands. In the monoanionic chelator coordinates to the metal through four nitrogen atoms, while in the chelator is trianionic, coordinating to the metal through three nitrogens and one sulfur atom. Solution NMR studies of , including two-dimensional NMR techniques (1H COSY and 1H/13C HSQC), confirmed that the N3S coordination mode of the chelators is retained in solution. Unlike , complexes may be considered relevant in the development of radiopharmaceuticals, as further corroborated by the synthesis of the congener [99mTcO{pz(CH2)2-NH-Gly-CH2S}]. This radioactive compound was obtained from 99mTcO4- in aqueous medium, in almost quantitative yield and with high specific activity and radiochemical purity.     

Syntheses of Cationic, Six-Coordinate Cadmium(II) Complexes Containing Tris(pyrazolyl)methane Ligands. Influence of Charge on Cadmium-113 NMR Chemical Shifts

Treating a thf (thf = tetrahydrofuran) suspension of Cd(acac)(2) (acac = acetylacetonate) with 2 equiv of HBF(4).Et(2)O results in the immediate formation of [Cd(2)(thf)(5)](BF(4))(4) (1). Crystallization of this complex from thf/CH(2)Cl(2) yields [Cd(thf)(4)](BF(4))(2) (2), a complex characterized in the solid state by X-ray crystallography. Crystal data: monoclinic, P2(1)/n, a = 7.784(2) ?, b = 10.408(2) ?, c = 14.632(7) ?, beta = 94.64(3) degrees, V = 1181.5(6) ?(3), Z = 2, R = 0.0484. The geometry about the cadmium is octahedral with a square planar arrangement of the thf ligands and a fluorine from each (BF(4))(-) occupying the remaining two octahedral sites. Reactions of [Cd(2)(thf)(5)](BF(4))(4) with either HC(3,5-Me(2)pz)(3) or HC(3-Phpz)(3) yield the dicationic, homoleptic compounds {[HC(3,5-Me(2)pz)(3)](2)Cd}(BF(4))(2) (3) and {[HC(3-Phpz)(3)](2)Cd}(BF(4))(2) (4) (pz = 1-pyrazolyl). The solid state structure of 3 has been determined by X-ray crystallography. Crystal data: rhombohedral, R&thremacr;, a = 12.236(8) ?, c = 22.69(3) ?, V = 2924(4) ?(3), Z = 3, R = 0.0548. The cadmium is bonded to the six nitrogen donor atoms in a trigonally distorted octahedral arrangement. Four monocationic, mixed ligand tris(pyrazolyl)methane-tris(pyrazolyl)borate complexes {[HC(3,5-Me(2)pz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF(4)) (5), {[HC(3,5-Me(2)pz)(3)][HB(3-Phpz)(3)]Cd}(BF(4)) (6), {[HC(3-Phpz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF(4)) (7), and {[HC(3-Phpz)(3)][HB(3-Phpz)(3)]Cd}(BF(4)) (8) are prepared by appropriate conproportionation reactions of 3or 4 with equimolar amounts of the appropriate homoleptic neutral tris(pyrazolyl)borate complexes [HB(3,5-Me(2)pz)(3)](2)Cd or [HB(3-Phpz)(3)](2)Cd. Solution (113)Cd NMR studies on complexes 3-8 demonstrate that the chemical shifts of the new cationic, tris(pyrazolyl)methane complexes are very similar to the neutral tris(pyrazolyl)borate complexes that contain similar substitution of the pyrazolyl rings.     

Carbophosphazene-supported ligand systems containing pyrazole/guanidine coordinating groups

Carbophosphazene-based coordination ligands [{NC(NMe(2))}(2){NP(3,5-Me(2)Pz)(2)}] (1), [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(3,5-Me(2)Pz)(2)}] (2), [NC(3,5-Me(2)Pz)](2)[NP(3,5-Me(2)Pz)(2)] (3), [{NCCl}(2){NP(NC(NMe(2))(2))(2)}] (4), and [{NC(p-OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}] (5) were synthesized and structurally characterized. In these compounds, the six-membered C(2)N(3)P ring is perfectly planar. The reaction of 1 with CuCl(2) afforded [{NC(NMe(2))}(2){NHP(O)(3,5-Me(2)Pz)}·{Cu(3,5-Me(2)PzH)(2)(Cl)}][Cl] (6). The ligand binds to Cu(II) utilizing the geminal [P(O)(3,5-Me(2)Pz)] coordinating unit. Similarly, the reaction of 2 with PdCl(2) afforded, after a metal-assisted P-N hydrolysis, [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(O)(3,5-Me(2)Pz)}·{Pd(3,5-Me(2)PzH)(Cl)}] (7). In the latter, the [P(O)(3,5-Me(2)Pz)] unit does not coordinate; in this instance, the Pd(II) is bound by a ring nitrogen atom and a carbon-tethered pyrazolyl nitrogen atom. The reaction of 3 with PdCl(2) also results in P-N bond hydrolysis affording [{NC(3,5-Me(2)Pz)(2)}{NP(O)(3,5-Me(2)Pz)}{Pd(Cl)}] (8). In contrast to 7, however, in 8, the Pd(II) elicits a nongeminal η(3) coordination from the ligand involving two carbon-tethered pyrazolyl groups and a ring nitrogen atom. Metalated products could not be isolated in the reaction of 3 with K(2)PtCl(4). Instead, a P-O-P bridged carbodiphosphazane dimer, [{NC(3,5-Me(2)Pz)NHC(3,5-Me(2)Pz)}{NP(O)}](2) (9), was isolated as the major product. Finally, the reaction of 5 with PdCl(2) resulted in [{NC(OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}·{PdCl(2)}] (10). In the latter, the exocyclic P-N bonds are quite robust and are involved in binding to the metal ion. Compounds 6-10 have been characterized by a variety of techniques including X-ray crystallography. In all of the compounds, the bond parameters of the inorganic heterocyclic rings are affected by metalation.     

Synthesis and catalytic properties of molybdenum(VI) complexes with tris(3,5-dimethyl-1-pyrazolyl)methane

The complex [MoO(2)Cl{HC(3,5-Me(2)pz)(3)}]BF(4) (1) (HC(3,5-Me(2)pz)(3) = tris(3,5-dimethyl-1-pyrazolyl)methane) has been prepared and examined as a catalyst for epoxidation of olefins at 55 °C using tert-butyl hydroperoxide (TBHP) as the oxidant. For reaction of cis-cyclooctene, epoxycyclooctane is obtained quantitatively within 5 h when water is rigorously excluded from the reaction mixture. Increasing amounts of water in the reaction mixture lead to lower activities (without affecting product selectivity) and transformation of 1 into the trioxidomolybdenum(VI) complex [{HC(3,5-Me(2)pz)(3)}MoO(3)] (4). Complex 4 was isolated as a microcrystalline solid by refluxing a suspension of 1 in water. The powder X-ray diffraction pattern of 4 can be indexed in the orthorhombic Pnma system, with a = 16.7349(5) ?, b = 13.6380(4) ?, and c = 7.8513(3) ?. Treatment of 1 in dichloromethane with excess TBHP led to isolation of the symmetrical [Mo(2)O(4)(μ(2)-O){HC(3,5-Me(2)pz)(3)}(2)](BF(4))(2) (2) and unsymmetrical [Mo(2)O(3)(O(2))(2)(μ(2)-O)(H(2)O){HC(3,5-Me(2)pz)(3)}] (3) oxido-bridged dimers, which were characterized by single-crystal X-ray diffraction. Complex 2 displays the well-known (Mo(2)O(5))(2+) bridging structure where each dioxidomolybdenum(VI) center is coordinated to three N atoms of the organic ligand and one μ(2)-bridging O atom. The unusual complex 3 comprises dioxido and oxidodiperoxo molybdenum(VI) centers linked by a μ(2)-bridging O atom, with the former center being coordinated to the tridentate N-ligand. The dinuclear complexes exhibit a similar catalytic performance to that found for mononuclear 1. For complexes 1 and 2 use of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate and N-butyl-3-methylpyridinium tetrafluoroborate as solvents allowed the complexes to be completely dissolved, and in each case the catalyst and IL could be recycled and reused without loss of activity.     

Re(V) and Re(III) complexes with sal2phen and triphenylphosphine: rearrangement, oxidation and reduction

Reactions of Re(V), tetradentate Schiff base complexes with tertiary phosphines have previously yielded both rearranged Re(V) and reduced Re(III) complexes. To further understand this chemistry, the rigid diiminediphenol (N(2)O(2)) Schiff base ligand sal(2)phen (N,N'-o-phenylenebis(salicylaldimine)) was reacted with (n-Bu(4)N)[ReOCl(4)] to yield trans-[ReOCl(sal(2)phen)] (1). On reaction with triphenylphosphine (PPh(3)), a rearranged Re(V) product cis-[ReO(PPh(3))(sal(2)phen*)]PF(6) (2), in which one of the imines was reduced to an amine during the reaction, and the reduced Re(III) products trans-[ReCl(PPh(3))(sal(2)phen)] (4) and trans-[Re(PPh(3))(2)(sal(2)phen)](+) (5) were isolated. Reaction of sal(2)phen with [ReCl(3)(PPh(3))(2)(CH(3)CN)] resulted in the isolation of [ReCl(2)(PPh(3))(2)(salphen)] (3). The compounds were characterized using standard spectroscopic methods, elemental analyses and single crystal X-ray crystallography.     

Isomerism in rhodium(I) N,S-donor heteroscorpionates: ring substituent and ancillary ligand effects

The heteroscorpionate ligands [HB(taz)(2)(pz(R))](-) (pz(R) = pz, pz(Me2), pz(Ph)) and [HB(taz)(pz)(2)](-), synthesised from the appropriate potassium hydrotris(pyrazolyl)borate salt and 4-ethyl-3-methyl-5-thioxo-1,2,4-triazole (Htaz), react with [{Rh(cod)(μ-Cl)}(2)] to give [Rh(cod)Tx] {Tx = HB(taz)(2)(pz), HB(taz)(2)(pz(Me2)), HB(taz)(2)(pz(Ph)), HB(taz)(pz)(2)}; the heteroscorpionate rhodaboratrane [Rh{B(taz)(2)(pz(Me2))}{HB(taz)(2)(pz(Me2))}] is the only isolable product from the reaction of [{Rh(nbd)(μ-Cl)}(2)] with K[HB(taz)(2)(pz(Me2))]. Carbonylation of the cod complexes gave a mixture of [Rh(CO)(2)Tx] and [(RhTx)(2)(μ-CO)(3)] which reacts with PR(3) to give [Rh(CO)(PR(3))Tx] (R = Cy, NMe(2), Ph, OPh). In the solid state the complexes are square planar with the particular structure dependent on the steric and/or electronic properties of the scorpionate and ancillary ligands. The complex [Rh(cod){HB(taz)(pz)(2)}] has the heteroscorpionate κ(2)[N(2)]-coordinated to rhodium with the B-H bond directed away from the rhodium square plane while [Rh(cod){HB(taz)(2)(pz(Me2))}] is κ(2)[SN]-coordinated, with the B-H bond directed towards the metal. The complexes [Rh(CO)(PPh(3)){HB(taz)(2)(pz)}] and [Rh(CO)(PPh(3)){HB(taz)(2)(pz(Me2))}] are also κ(2)[SN]-coordinated but with the pyrazolyl ring cis to PPh(3); in the former the B-H bond is directed towards rhodium while in the latter the ring is pseudo-parallel to the rhodium square plane, as also found for [Rh(CO)(2){HB(taz)(2)(pz(Me2))}]. The analogues [Rh(CO)(PR(3)){HB(taz)(2)(pz(Me2))}] (R = Cy, NMe(2)) have the phosphines trans to the pyrazolyl ring. Uniquely, [Rh(CO)(PPh(3)){HB(taz)(2)(pz(Ph))}] is κ(2)[S(2)]-coordinated. A qualitative mechanism is given for the rapid ring-exchange, and hence isomerisation, observed in solution.     

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.     

Rhenium and technetium complexes with N,N-dialkyl-N'-benzoylthioureas

N,N-Dialkyl-N'-benzoylthioureas, HR(1)R(2)btu, react under single deprotonation and form air-stable chelate complexes with common rhenium or technetium complexes such as (NBu(4))[MOCl(4)] (M = Re, Tc) or [ReOCl(3)(PPh(3))(2)]. Compositions and molecular structures of the products are strongly dependent on the precursors used and the reaction conditions applied. Reactions with [ReOCl(3)(PPh(3))(2)] in CH(2)Cl(2) give complexes of the general formula [ReOCl(2)(R(1)R(2)btu)(PPh(3))] (3), with the benzoyl oxygen atom of the chelating benzoylthiourea being trans to the oxo ligand, and/or Re(III) complexes of the composition [ReCl(2)(R(1)R(2)btu)(PPh(3))(2)] (4) with the PPh(3) ligands in trans positions to each other. In polar solvents such as MeOH, EtOH or acetone, corresponding reactions without addition of a supporting base only result in intractable brown solutions, from which no crystalline complexes could be isolated. The addition of NEt(3), however, allows the isolation of the bis-chelates [ReOCl(R(1)R(2)btu)(2)] (1) in good yields. In this type of complex, one of the chelating R(1)R(2)btu- ligands coordinates equatorially, while the second occupies the position trans to the oxo ligand with its oxygen atom. The latter compounds can also be prepared from (NBu(4))[ReOCl(4)] in MeOH when no base is added, while the addition of NEt(3) results in the formation of [ReO(OMe)(R(1)R(2)btu)(2)] (5) complexes with the methoxo ligand trans to O(2-). Compounds of the type 5 can alternatively be prepared by heating 1 in MeOH with addition of NEt(3). A reversible conversion of 5 into oxo-bridged dimers of the composition [{ReO(R(1)R(1)btu)(2)}(2)O] (6) is observed in water-containing solvents. Starting from (NBu(4))[TcOCl(4)], a series of technetium complexes of the type [TcOCl(R(1)R(2)btu)(2)] (2) could be prepared. The structures of such compounds are similar to those of the rhenium analogues 1. Reduction of 2 with PPh(3) in CH(2)Cl(2) gives Tc(III) complexes of the composition [TcCl(R(1)R(2)btu)(2)(PPh(3))] (7) having the chloro and PPh(3) ligands in cis positions. When this reaction is performed in the presence of excess chelating ligand, the Tc(III) tris-chelates [Tc(R(1)R(2)btu)(3)] (8) are formed.     

蝎型钒氧苯甲酸配合物的合成、结构及量化计算

设计合成了两种以聚吡唑硼酸盐、苯甲酸为配体的钒氧配合物VO[HB(pz)3](pzH)(C6H5COO)(1)和VO[HB(3,5-Me2pz)3](3,5-Me2pzH)(C6H5COO)(2)((HB(pz)3: 聚吡唑硼酸钠盐; pzH: 吡唑; HB(3,5-Me2pz)3: 聚甲基吡唑硼酸钠盐; 3,5-Me2pzH: 3,5-二甲基吡唑). 通过元素分析、红外光谱和X射线单晶衍射方法对配合物进行了表征. 并结合从头计算结果进一步分析了配合物的稳定性及分子中配键的共价特征. 分析结果表明, 配合物2的稳定性大于配合物1, 中心钒原子周围的价键类型都属于共价键范畴, 键序分析结果与晶体结构测定的键长结果是一致的.     

Syntheses and structures of pyrazolylmethane complexes of rhenium(III), (IV) and (V)

Reaction of [ReOCl3(PPh3)(2)] with HCpz(3) (pz = pyrazole) in dichloromethane leads to the formation of a new Re(iv) complex [ReCl3(HCpz3)]X (X=Cl, [ReO4]) with loss of the rhenium-oxo group. We also report a convenient, high-yield synthetic route to complexes of the type [ReOXn(L)](3-n)+ (X=Cl, Br, n = 2, 3) by the reaction of bis(pyrazolylmethane) and bis(pyrazolylacetate) ligands with [ReOCl3(PPh3)2]. Dinuclear complexes containing the O=Re-O-Re=O group were also isolated and structurally characterised. We have also investigated the reactions of these ligands with diazenide precursors and isolated and characterised complexes of the type [ReClx(N2Ph) (L)(PPh3)] (x = 1,2). The potential applications of these complexes as radiopharmaeuticals is discussed.     

Rhenium and technetium tricarbonyl complexes anchored by pyrazole-based tripods: novel lead structures for the design of myocardial imaging agents

This report describes the synthesis and biological evaluation of cationic (99m)Tc-tricarbonyl complexes anchored by ether-containing tris(pyrazolyl)methane or bis(pyrazolyl)ethanamine ligands to be applied in the design of radiopharmaceuticals for myocardial imaging: fac-[(99m)Tc(CO)(3){RC(pz)(3)}](+) (R = H (1a), MeOCH(2) (2a), EtOCH(2) (3a), (n)PrOCH(2) (4a)) and fac-[(99m)Tc(CO)(3){RNHCH(2)CH(pz)(2)}](+) (R = H (5a), MeO(CH(2))(2) (6a)) (pz = pyrazolyl). At the no carrier added level, complexes 1a-6a were obtained in high radiochemical yield (> 98%) by reaction of fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) with the corresponding tripod chelator in aqueous medium. All these complexes display a high in vitro and in vivo stability, except 6a which metabolizes in vivo yielding fac-[(99m)Tc(CO)(3){HO(CH(2))(2)NHCH(2)CH(pz)(2)}](+) (7a). Biological studies in mice have shown that among the radiotracers evaluated in this work, 3a, anchored by a tris(pyrazolyl)methane chelator bearing an ethyl methyl ether substituent, has the highest heart uptake (3.6 +/- 0.5%ID g(-1) at 60 min p.i.). Complex 3a presents also the best heart: blood, heart: liver and heart: lung ratios, appearing as the most promising as a potential myocardial imaging agent. The chemical identity of 1a-7a was ascertained by HPLC comparison with the previously reported fac-[Re(CO)(3){HC(pz)(3)}]Br (1) and with the novel fac-[Re(CO)(3){RC(pz)(3)}]Br (R = MeOCH(2) (2), EtOCH(2) (3), (n)PrOCH(2)(4)) and fac-[Re(CO)(3){RNHCH(2)CH(pz)(2)}]Br (R = H (5), MeO(CH(2))(2) (6) HO(CH(2))(2) (7)). The novel Re(I) tricarbonyl complexes, 2-7, were characterized by the common analytical techniques, including single crystal X-ray diffraction analysis. The solid state structure confirmed the presence of facial and tridentate (kappa(3)-N(3)) anchor ligands. Solution NMR studies have also shown that this kappa(3)-N(3) coordination mode is retained in solution for all complexes (2-7).     

Solid-state structural and magnetic investigations of [M[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (M = Fe,Co, Ni,Cu): observation of a thermally induced solid-state phase change controlling an iron(II) spin-state crossover

The reaction of M(BF(4))(2).xH(2)O (M = Co, Ni, and Cu) and HC(3,5-Me(2)pz)(3) in a 1:2 ratio yields [Co[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (2), [Ni[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (3), and [Cu[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (4). Over the temperature range from 5 to 350, 345, or 320 K, Curie law behavior is observed for microcrystalline samples of all three compounds showing them to have three, two, and one unpaired electrons, respectively, with no spin-crossover observed for 2. Crystalline samples of these compounds torque in the applied magnetic field the first time the sample is cooled to 5 K. The solid-state structures of all three are isomorphous at 220 K, monoclinic in the space group C2/c. The metal is located on a unique crystallographic site and has a trigonally distorted octahedral structure, with 4 showing the expected Jahn-Teller distortions. Cooling crystals of all three to low temperatures leads to the observation of the same phase change to triclinic in the new space group P(-)1 with nonmerohedral twinning. This change is reversible and yields two crystallographically unique metal sites at low temperature. The bond angles and distances for the two different metal sites for each compound in the low temperature structures are very similar to each other and to those in the 220 K structures. The same phase change, monoclinic to triclinic, has been observed previously for [Fe[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (1), except in this case, the phase change results in half of the cations changing over from the high-spin state to the low-spin state while the other half of the cations remain high-spin, with the low-spin form decreasing its Fe-N bond distances by 0.19 A. The new results with 2-4 show that it is the phase transition, which occurs in complexes of the type [M[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) with first row transition metals, that is driving the unusual spin-crossover behavior of [Fe[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2).     

Mononuclear and binuclear sandwich copper(II) complexes with poly(pyrazolyl)borate ligands: syntheses, structures and properties

A series of Cu(II) complexes Cu(2)[micro-pz](2)[HB(pz)(3)](2) (1), Cu[H(2)B(pz)(2)](2) (2), Cu[HB(pz)(3)](2) (3), Cu[HB(pz(Me2))(3)](2) (4), Cu[B(pz)(4)](2) (5) (pz=pyrazole), have been synthesized and characterized by elemental analysis, IR, UV-vis, X-ray diffraction, thermal analysis and theoretical analysis. The IR spectra give the Cu-N vibration modes at 322, 366, 344, 387, and 380 cm(-1) in complexes 1-5, respectively. The UV spectra show all the complexes have same UV absorption at 232 nm; there is another band at 332 nm for complexes 1, 2 and 4, while for complexes 3 and 5, the bands are at 272 and 308 nm, respectively. Complex 1 has a binuclear structure in which two pyrazole ligands bridge two Cu-Tp units. In 2-5, the Cu(II) centers are coordinated with dihydrobis(pyrazolyl)borate (Bp), hydrotris(pyrazolyl)borate (Tp), hydrotris(3,5-Me2pyrazolyl)borate (Tp'), tetrakis(pyrazolyl)borate (Tkp) respectively to form a mononuclear structure. The results of thermal analysis for complexes 1-5 are discussed too.     

A Six-Coordinate Tris(3,5-dimethyl-1-pyrazolyl)methane-Thallium(I) Complex with a Stereochemically Inactive Lone Pair: Syntheses and Solid State Structures of {[HC(3,5-Me(2)pz)(3)](2)Tl}PF(6) and {[HC(3,5-Me(2)pz)(3)]Tl}PF(6) (pz = Pyrazolyl)

The addition of the tris(pyrazolyl)methane ligand HC(3,5-Me(2)pz)(3) (pz = pyrazolyl ring) to a THF solution of TlPF(6) results in the immediate precipitation of {[HC(3,5-Me(2)pz)(3)](2)Tl}PF(6). The structure has been determined crystallographically. The arrangement of the nitrogen donor atoms about the thallium is best described as a trigonally distorted octahedron. The thallium atom sits on a crystallographic center of inversion; thus the planes formed by the three nitrogen donor atoms of each ligand are parallel. The Tl-N bond distances range from 2.891(5) to 2.929(5) ? (average = 2.92) ?. The lone pair on thallium is clearly stereochemically inactive and does not appear to influence the structure. The pyrazolyl rings are planar, but are tilted with respect to the thallium atom so as to open up the N.N intraligand bite distances. The thallium(I) complex with a ligand to metal ratio of 1/1, {[HC(3,5-Me(2)pz)(3)]Tl}PF(6), is prepared in acetone by the reaction of equimolar amounts of HC(3,5-Me(2)pz)(3) and TlPF(6). The structure of the cation is a trigonal pyramid, with Tl-N bond distances that range from 2.64(1) to 2.70(1) ? (average = 2.67) ?. Pyrazolyl ring tilting is also observed in this complex, but the degree of tilting is smaller. Crystal data for {[HC(3,5-Me(2)pz)(3)](2)Tl}PF(6): monoclinic, P2(1)/c, a = 9.210(6) ?, b = 13.36(1) ?, c = 16.067(8) ?, beta = 92.48(5) degrees, V = 1975(2) ?(3), Z = 2, R = 0.029. For {[HC(3,5-Me(2)pz)(3)]Tl}PF(6): monoclinic, P2(1)/n, a = 10.685(2) ?, b = 16.200(5) ?, c = 13.028(3) ?, beta = 94.02(2) degrees, V = 2249.6(8) ?(3), Z = 4, R = 0.042.     

C-H activation and C=C double bond formation reactions in iridium ortho-methyl arylphosphane complexes

The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species.     

Rhenium complexes with 2-(diphenylphosphinomethyl)aniline: formation of a cyclic, trinuclear oxorhenium(V) core

Reactions of 2-(diphenylphosphinomethyl)aniline, H(2)L(2), with (NBu(4))[ReOCl(4)] yield different oxo rhenium(V) complexes depending on the conditions applied. This comprises monomeric compounds such as [ReOCl(3)(H(2)L(2))] (1), [ReOCl(2)(OMe)(H(2)L(2))] (2), or [ReO(2)(H(2)L(2))(2)]Cl (5) as well as the dimeric μ-oxo complex [{ReOCl(2)(H(2)L(2))}(2)]O] (3) and the oxo-bridged trimer [{ReOCl(H(2)L(2))}O](3) (4). The latter compound represents the first example of a hitherto unknown trinuclear, cyclic oxo(V) core. [{ReOCl(H(2)L(2))}O](3) contains a tensed 6-membered metallacycle, which readily undergoes rearrangements and reactions with additional ligands. Compounds of the compositions 5 and [ReO(2)(H(2)L(2))(H(2)L(1))]Cl (6) were isolated either from the decomposition of 4 in CH(2)Cl(2)/n-pentane or from reactions with 2-(diphenylphosphino)aniline, H(2)L(1).     

Coordination features of a hybrid scorpionate/phosphane ligand exemplified with Iridium

Although the pentacoordinated complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(cod)] (1; pz=pyrazolyl, cod=1,5-cyclooctadiene), isolated from the reaction of [{Ir(mu-Cl)(cod)}(2)] with [Li(tmen)][B(allyl)(CH(2)PPh(2))- (pz)(2)] (tmen=N,N,N',N'-tetramethylethane-1,2-diamine), shows behavior similar to that of the related hydridotris(pyrazolyl)borate complex, the carbonyl derivatives behave in a quite different way. On carbonylation of 1, the metal--metal-bonded complex [(Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}CO)(2)(mu-CO)] (2) that results has a single ketonic carbonyl bridge. This bridging carbonyl is labile such that upon treatment of 2 with PMe(3) the pentacoordinated Ir(I) complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PMe(3))] (3) was isolated. Complex 3 shows a unique fac coordination of the hybrid ligand with the allyl group eta(2)-bonded to the metal in the equatorial plane of a distorted trigonal bipyramid with one pyrazolate group remaining uncoordinated. This unusual feature can be rationalized on the basis of the electron-rich nature of the metal center. The related complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PPh(3))] (4) was found to exist in solution as a temperature-dependent equilibrium between the cis-pentacoordinated and trans square planar isomers with respect to the phosphorus donor atoms. Protonation of 3 with different acids is selective at the iridium center and gives the cationic hydrides [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PMe(3))]X (X=BF(4) (5), MeCO(2) (6), and Cl (7)). Complex 7 further reacts with HCl to generate the unexpected product [Ir(CO)Cl{(Hpz)B(CH(2)PPh(2))(pz)CH(2)CH(Me)}(PMe(3))]Cl (9; Hpz=protonated pyrazolyl group) formed by the insertion of the hydride into the Ir-(eta(2)-allyl) bond. In contrast, protonation of complex 4 with HCl stops at the hydrido complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PPh(3))]Cl (8). X-ray diffraction studies carried out on complexes 2, 3, and 9 show the versatility of the hybrid scorpionate ligand in its coordination.     

Hybrid dibismuthines and distibines as ligands towards transition metal carbonyls

The hybrid dibismuthines O(CH(2)CH(2)BiPh(2))(2) and MeN(CH(2)-2-C(6)H(4)BiPh(2))(2) react with [M(CO)(5)(thf)] (M = Cr or W) to form [{M(CO)(5)}(2){O(CH(2)CH(2)BiPh(2))(2)}] and [{Cr(CO)(5)}(2){MeN(CH(2)-2-C(6)H(4)BiPh(2))(2)}] containing bridging bidentate (Bi(2)) coordination. The unsymmetrical tertiary bismuthine complexes [M(CO)(5){BiPh(2)(o-C(6)H(4)OMe)}] are also described. Depending upon the molar ratio, the hybrid distibines O(CH(2)CH(2)SbMe(2))(2) and MeN(CH(2)-2-C(6)H(4)SbMe(2))(2) react with [M(CO)(5)(thf)] to give the pentacarbonyl complexes [{M(CO)(5)}(2){O(CH(2)CH(2)SbMe(2))(2)}] and [{Cr(CO)(5)}(2){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}] or tetracarbonyls cis-[M(CO)(4){O(CH(2)CH(2)SbMe(2))(2)}] and cis-[M(CO)(4){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}]. The latter can also be obtained from [Cr(CO)(4)(nbd)] or [W(CO)(4)(pip)(2)], and contain chelating bidentates (Sb(2)-coordinated) as determined crystallographically. S(CH(2)-2-C(6)H(4)SbMe(2))(2) coordinates as a tridentate (SSb(2)) in fac-[M(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}] (M = Cr or Mo) and fac-[Mn(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}][CF(3)SO(3)]. Fac-[Mn(CO)(3){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}][CF(3)SO(3)] contains NSb(2)-coordinated ligand in the solid state, but in solution a second species, Sb(2)-coordinated and with a κ(1)-CF(3)SO(3) replacing the coordinated amine is also evident. X-ray crystal structures were also determined for fac-[Cr(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}], fac-[Mn(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}][CF(3)SO(3)] and fac-[Mn(CO)(3){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}] [CF(3)SO(3)]. Hypervalent N···Sb interactions are present in cis-[M(CO)(4){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}] (M = Mo or W), but absent for M = Cr.     

A mercury bis(tricarbido) complex: [Hg{C triple bond C-C triple bond W(CO)2Tp}2(dmso)4](dmso)2 (Tp = hydrotrispyrazolylborate)

Fluoride mediated desilylation of the propargylidyne complex [W(triple bond C-C triple bond CSiMe(3))(CO)(2){HB(pz)(3)}] (pz = pyrazol-1-yl) in the presence of mercury(II) chloride provides the novel bis(tricarbido)complex [Hg{C triple bond C-C triple bond W(CO)(2){HB(pz)(3)}}(2)], which was structurally characterised as a dmso hexasolvate.     

A mechanistic investigation of oxidative addition of methyl iodide to [Tp*Rh(CO)(L)

Reaction of methyl iodide with square planar [kappa(2)-Tp*Rh(CO)(PMe(3))] 1a (Tp* = HB(3,5-Me(2)pz)(3)) at room temperature affords [kappa(3)-Tp*Rh(CO)(PMe(3))(Me)]I 2a, which was fully characterized by spectroscopy and X-ray crystallography. The pseudooctahedral geometry of cationic 2a, which contains a kappa(3)-coordinated Tp* ligand, indicates a reaction mechanism in which nucleophilic attack by Rh on MeI is accompanied by coordination of the pendant pyrazolyl group. In solution 2a transforms slowly into a neutral (acetyl)(iodo) rhodium complex [kappa(3)-Tp*Rh(PMe(3))(COMe)I] 3a, for which an X-ray crystal structure is also reported. Kinetic studies on the reactions of [kappa(2)-Tp*Rh(CO)(L)] (L = PMe(3), PMe(2)Ph, PMePh(2), PPh(3), CO)] with MeI show second-order behavior with large negative activation entropies, consistent with an S(N)2 mechanism. The second-order rate constants correlate well with phosphine basicity. For L = CO, reaction with MeI gives an acetyl complex, [kappa(3)-Tp*Rh(CO)(COMe)I]. The bis(pyrazolyl)borate complexes [kappa(2)-Bp*Rh(CO)(L)] (L = PPh(3), CO) are much less reactive toward MeI than the Tp* analogues, indicating the importance of the third pyrazolyl group and the accessibility of a kappa(3) coordination mode. The results strengthen the evidence in favor of an S(N)2 mechanism for oxidative addition of MeI to square planar d(8) transition metal complexes.