Chiral poly(pyrazolyl)borate ligands and complexes: III. Chiral poly(pyrazolyl)borate isonitrile complexes of molybdenum and tungsten

The syntheses of enantiomeric and diastereoisomeric Bpz₄M★(CO)(NO)(CNR) complexes (M = Mo, W; R = CH₂CH₃, CH₂Ph, C★H(CH₃)(C₆H₅)) are reported. When R = CH₂CH₃ or CH₂C₆H₅ the presence of the diastereotopic methylene hydrogens does not allow the detection of the neighbouring chiral center, because they are magnetically equivalent. The diastereoisomeric complexes show different ¹H NMR signals, but cannot be resolved by liquid chromatography or by crystallization.     

Sterically bulky tris(triazolyl)borate ligands as water-soluble analogues of tris(pyrazolyl)borate

The recently synthesized 3-tert-butyl-5-methyl-1,2,4-triazole reacted with KBH4 to give the new potassium tris(3-tert-butyl-5-methyl-1,2,4-triazolyl)borate K(Ttz(tBu,Me)) ligand. Ttz(tBu,Me) formed a four-coordinate (Ttz(tBu,Me))CoCl complex and five-coordinate (Ttz(tBu,Me))CoNO3 and (Ttz(tBu,Me))ZnOAc complexes. When these complexes were compared to their Tp(tBu,Me) analogues, it was found that Ttz(tBu,Me) resulted in negligible steric differences. K(Ttz(tBu,Me)) is more water-soluble than K(Tp(tBu,Me)), so bulky tris(triazolyl)borate ligands should lead to functional models for enzyme active sites in an aqueous environment and the creation of water-soluble analogues of Tp catalysts.     

Tricarbonylmanganese(I) derivatives of [Di(pyrazolyl)(2-pyridyl)methyl]aryl scorpionates

The cobalt(II) chloride catalyzed Peterson rearrangement reactions between sulfinyldi-(pyrazolyl) and aryl(pyridyl)methanone derivatives yield di(pyrazolyl)(pyridyl)hetero-scorpionate ligands. Reaction of these ligands with Mn(CO)₅Br in the presence of a silver salt produces the monometallic complexes {[κ³-PhC(pz)₂(2-py)]Mn(CO)₃}(O₃SCF₃) (1a), {[κ³-PhC(pz)₂(2-py)]Mn(CO)₃}(PF₆) (1b), {[κ³-PhC(^4-Mepz)₂(2-py)]Mn(CO)₃}(PF₆) (2), {[κ³-p-BrC₆H₄C(pz)₂(2-py)]Mn(CO)₃}(PF₆) (3), and the bimetallic complexes [(CO)₃Mn{m-C₆H₄[C(pz)₂(2-py)]₂}Mn(CO)₃](BF₄)₂ (5a) and {m-C₆H₄[C(pz)₂(2-py)Mn(CO)₃]₂}(PF₆)₂ (5b) (pz = pyrazolyl ring, py = pyridyl ring). These octahedral manganese complexes show interesting structural diversity, with the complexes being organized in the solid state into complex supramolecular structures by an array of non-covalent forces.     

Structural analysis of the conformational flexibility of tris(pyrazolyl)borate ligands and their analogues

Database analysis and molecular mechanics were used to determine the conformational flexibility of tridentate scorpionate ligands. The tris(pyrazolyl)methane and tris(pyrazolyl)borate ligands act like molecular vises, opening their tripodal structure for larger metals and closing around smaller metal ions. Tris(3-tert-butylpyrazolyl)methane has significant preference for larger metal ions than its unsubstituted parent compound. Tris(pyrazolyl)methanes and tris(pyrazolyl)borates have similar conformational flexibilities. Placing sterically hindered groups on the central carbon or boron has only a minor effect on the geometry of the tris(pyrazolyl)methanes and tris(pyrazolyl)borates. However, it does influence the flexibility of the ligands, particularly when they have to open far from their ideal geometry, which commonly occurs.     

Syntheses and structures of lanthanide(III) complexes with some bis(pyrazolyl)borate and tris(pyrazolyl)borate podand ligands

Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4-^tbutyl)-pyrid-2-yl}-pyrazol-1-yl]hydroborate (KTp^BuPy) which has three bidentate arms and is therefore hexadentate; and potassium bis[3-(2-pyridyl)-5-(methoxymethyl)pyrazol-1-yl]-dihydroborate (KBp^(COC)Py) which has two bidentate arms and is therefore tetradentate. The crystal structures of their lanthanide complexes [La(Tp^BuPy)(NO₃)₂] and [La(Bp^(COC)Py)₂X] (X=nitrate or triflate) have been determined. In [La(Tp^BuPy)(NO₃)₂] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp^(COC)Py)₂(NO₃)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp^(COC)Py)₂(CF₃SO₃)] the metal ion is nine-coordinate because the triflate anion is monodentate. Two unexpected new complexes which arose from partial decomposition of the poly(pyrazolyl)borate ligands have also been characterised structurally. In [La(^BuPypzH)₃(O₃SCF₃)₃] the metal ion is nine-coordinate from three bidentate pyrazolyl-pyridine arms (liberated by decomposition of KTp^BuPy) and three triflate anions; there is extensive NH· · · O hydrogen-bonding between the pyrazolyl and triflate ligands. [Nd(Tp^Py)(Bp^Py)][Nd(PypzH)(NO₃)₄] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-yl]hydroborate (Tp^Py) with Nd(NO₃)₃. One of the Tp^Py ligands has lost one bidentate pyrazolyl-pyridine ‘arm’ (PypzH) to leave tetradentate tris[3-(2-pyridyl)-pyrazol-1-yl]dihydroborate (Bp^Py). In this structure, the cation [Nd(Tp^Py)(Bp^Py)]⁺ is ten-coordinate from inter-leaved hexadentate and tetradentate ligands, and the anion [Nd(PypzH)(NO₃)₄]⁻ is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates.     

Solid-state structure and solution behavior of eight-coordinate Sm(III) poly(pyrazolyl)borate compounds

[Sm(Tp(Me2)(2)(kappa(2)-S(2)CNR(2))] compounds (R = Et (1), Me (2); Tp(Me2) = HB(3,5-Me2pz)(3)) have been isolated from reaction of (R(2)NC(S)S)(2) with 2 equiv of [Sm(Tp(Me2)(2)]. Reductive cleavage of 2,2'-dipyridyl disulfide or 2,2'-dipyridyl diselenide by [Sm(Tp(Me2)(2)] afforded good yields of [Sm(Tp(Me2)(2)(kappa(2)-Y)] compounds (Y = 2-SC(5)H(4)N (3), 2-SeC(5)H(4)N (4)). 4 is the first selenopyridine complex of an f-block element. Sm(Tp(Me2)(2)(2-OC(5)H(4)N) (5) has been synthesized by salt metathesis of [Sm(Tp(Me2)(2)Cl] with the sodium salt of the 2-hydroxypyridine. The solid-state structures of 1, 3, 4, and 5 were determined by single-crystal X-ray diffraction analysis and revealed that the compounds are all eight-coordinate with dodecahedral geometry. The samarium atoms are bound in tridentate fashion to two pyrazolylborate ligands and in bidentate fashion by the third ligand. The solution behavior of the compounds was studied by (1)H NMR techniques. (1)H-(1)H exchange spectroscopy experiments give evidence for two distinct dynamic regimes occurring in solution.     

VIB金属蝎型配合物(Scorpionate)的研究进展

综述了VIB金属(Mo、W)多吡唑硼配合物近年来的研究进展。详细地叙述了第二代多吡唑硼配体的合成与表征。     

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.     

Elucidating drug-metalloprotein interactions with tris(pyrazolyl)borate model complexes

The tetrahedral zinc complex [(Tp(Me,Ph))ZnOH] (Tp(Me,Ph) = hydrotris(5,3-methylphenylpyrazolyl)borate) was combined with acetohydroxamic acid, 3-mercapto-2-butanone, N-(methyl)mercaptoacetamide, beta-mercaptoethanol, 3-mercapto-2-propanol, and 3-mercapto-2-butanol to generate the complexes [(Tp(Me,Ph))Zn(ZBG)] (ZBG = zinc-binding group). These complexes were prepared to determine the mode of binding for three different types of thiol-derived matrix metalloproteinase (MMP) inhibitors. The solid-state structures of all six metal complexes were determined by X-ray crystallography. The structures reveal that while beta-mercaptoketones and beta-mercaptoamides bind the zinc ion in a bidentate fashion, the three beta-mercaptoalcohol compounds only demonstrate monodentate coordination via the sulfur atom. Prior to this work, no experimental data were available for the binding conformation of these types of inhibitors to the zinc active site of MMPs. The results of these model studies reveal different binding modes for these ZBGs and are useful for explaining the results of inhibition assays and in second-generation drug design. This work demonstrates the utility of model complexes as a tool for revealing drug-metalloprotein interactions.     

Solid state and solution structures of rhodium and iridium poly(pyrazolyl)borate diene complexes

The structures adopted by a range of poly(pyrazolyl)borate complexes [ML2Tp(x)] [M = Rh, Ir; L2 = diene; Tp(x) = Bp' {dihydrobis(3,5-dimethylpyrazolyl)borate}, Tp' {hydrotris(3,5-dimethylpyrazolyl)borate}, Tp {hydrotris(pyrazolyl)borate}, B(pz)4 {tetrakis(pyrazolyl)borate}] have been investigated. Low steric hindrance between ligands in [Rh(eta-nbd)Tp] (nbd = norbornadiene), [Rh(eta-cod)Tp] (cod = cycloocta-1,5-diene) and [Rh(eta-nbd)Tp'] results in K3 coordination of the pyrazolylborate but [M(eta-cod)Tp'] (M = Rh, Ir) are kappa2 coordinated with the free pyrazolyl ring positioned above and approximately parallel to the square plane about the metal. All but the most sterically hindered Tp(x) complexes undergo fast exchange of the coordinated and uncoordinated pyrazolyl rings on the NMR spectroscopic timescale. For [Rh(eta-cod){B(pz)4}], [Rh(eta-dmbd)Tp'] (dmbd = 2,3-dimethylbuta-1,3-diene) and [Rh(eta-cod)Tp(Ph)] {Tp(Ph) = hydrotris(3-phenylpyrazolyl)borate} the fluxional process is slowed at low temperatures so that inequivalent pyrazolyl rings are observed. The bonding modes of the Tp' ligand (but not of other pyrazolylborate ligands) can be determined by 11B NMR and IR spectroscopy. The 11B chemical shifts (for a series of Tp' complexes) show the general pattern, kappa3 < -7.5 ppm < kappa2 and the nu(BH) stretch kappa3 > 2500 cm(-1) > kappa2. The electrochemical behaviour of the pyrazolylborate complexes is related to the degree of structural change which occurs on electron transfer. One-electron oxidation of complexes with Tp', Tp and B(pz)4 ligands is generally reversible although that of [Ir(etacod)Tp] is only reversible at higher scan rates and that of [Ir(eta-cod){B(pz)4}] is irreversible. Of the complexes with the more sterically hindered Tp(Ph) ligand, only [Rh(eta-nbd)Tp(Ph)] shows any degree of reversible oxidation. The ESR spectra of a range of Rh(II) complexes show coupling to both 14N and 103Rh nuclei in most cases but what appears to be coupling to rhodium and one hydrogen atom, possibly a hydride ligand, for the oxidation product of [Rh(eta-nbd)Tp(Ph)].     

Photochemistry of tris(pyrazolyl)borate titanium(IV) complexes

The electronic features and photochemistry of TpTiCl₃ (1) (Tp = hydrotris(pyrazol-1-yl)borate) and Tp*TiCl₃ (2) (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) were studied in THF. Reactive decay of the excited states produced either (or ) and metal center Ti(III) radicals via homolytic cleavage of the Tp → Ti (Tp* → Ti) bond. Cleavage of the Tp → Ti and the Tp* → Ti bond as a primary photoprocess is shown to be consistent with LMCT Tp → Ti and Tp* → Ti excitation. TpTiCl₂(THF) (3) and Tp*TiCl₂(THF) (4) were also prepared by stoichiometric reduction of 1 and 2 with Li₃N. The THF ligand in 3 and 4 was replaced by the stable nitroxyl radical TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to provide the new complexes TpTiCl₂(TEMPO) (5) and Tp*TiCl₂(TEMPO) (6) in which the TEMPO ligand is η¹ coordinated to Ti(IV). Photolysis of 5 and 6 generate Ti(III) and the TEMPO radical in the primary photochemical step.     

Ruthenium tris(pyrazolyl)borate diazo complexes: preparation of aryldiazenido, aryldiazene, and hydrazine derivatives

Tris(pyrazolyl)borate aryldiazenido complexes [RuTpLL'(ArN(2))](BF(4))(2) (1-3) [Ar = C(6)H(5), 4-CH(3)C(6)H(4); Tp = hydridotris(pyrazolyl)borate; L = P(OEt)(3) or PPh(OEt)(2), L' = PPh(3); L = L' = P(OEt)(3)] were prepared by allowing dihydrogen [RuTp(eta(2)-H(2))LL'](+) derivatives to react with aryldiazonium cations. Spectroscopic characterization (IR, (15)N NMR) using the (15)N-labeled derivatives strongly supports the presence of a linear [Ru]-NN-Ar aryldiazenido group. Hydrazine complexes [RuTp(RNHNH(2))LL']BPh(4) (4-6) [R = H, CH(3), C(6)H(5), 4-NO(2)C(6)H(4); L = P(OEt)(3) or PPh(OEt)(2), L' = PPh(3); L = L' = P(OEt)(3)] were also prepared by reacting the [RuTp(eta(2)-H(2))LL'](+) cation with an excess of hydrazine. The complexes were characterized spectroscopically (IR and NMR) and by X-ray crystal structure determination of the [RuTp(CH(3)NHNH(2))[P(OEt)(3)](PPh(3))]BPh(4) (4d) derivative. Tris(pyrazolyl)borate aryldiazene complexes [RuTp(ArN=NH)LL']BPh(4) (7-9) (Ar = C(6)H(5), 4-CH(3)C(6)H(4)) were prepared following three different methods: (i). by allowing hydride species RuHTpLL' to react with aryldiazonium cations in CH(2)Cl(2); (ii). by treating aryldiazenido [RuTpLL'(ArN(2))](BF(4))(2) with LiBHEt(3) in CH(2)Cl(2); (iii). by oxidizing arylhydrazine [RuTp(ArNHNH(2))LL']BPh(4) complexes with Pb(OAc)(4) in CH(2)Cl(2) at -30 degrees C. Methyldiazene complexes [RuTp(CH(3)N=NH)LL']BPh(4) were also prepared by the oxidation of the corresponding methylhydrazine [RuTp(CH(3)NHNH(2))LL']BPh(4) with Pb(OAc)(4).     

Structural and electronic differences of copper(I) complexes with tris(pyrazolyl)methane and hydrotris(pyrazolyl)borate ligands

Copper(I) complexes with tripodal nitrogen-containing neutral ligands such as tris(3,5-diisopropyl-1-pyrazolyl)methane (L1') and tris(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)methane (L3'), and with corresponding anionic ligands such as hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (L1-) and hydrotris(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)borate (L3-) were synthesized and structurally characterized. Copper(I) complexes [Cu(L1')Cl] (1), [Cu(L1')(OClO3)] (2), [Cu(L1')(NCMe)](PF6) (3a), [Cu(L1')(NCMe)](ClO4) (3b), [Cu(L1')(CO)](PF6) (4a), and [Cu(L1')(CO)](ClO4) (4b) were prepared using the ligand L1'. Copper(I) complexes [Cu(L3')Cl] (5) and [Cu(L3')(NCMe)](PF6) (6) with the ligand L3' were also synthesized. Copper(I) complexes [Cu(L1)(NCMe)] (7) and [Cu(L1)(CO)] (8) were prepared using the anionic ligand L1-. Finally, copper(I) complexes with anionic ligand L3- and acetonitrile (9) and carbon monoxide (10) were synthesized. The complexes obtained were fully characterized by IR, far-IR, 1H NMR, and 13C NMR spectroscopy. The structures of both ligands, L1' and L3', and of complexes 1, 2, 3a, 3b, 4a, 4b, 5, 6, 7, and 10 were determined by X-ray crystallography. The effects of the differences in (a) the fourth ligand and the counteranion, (b) the steric hindrance at the third position of the pyrazolyl rings, and most importantly, (c) the charge of the N3 type ligands, on the structures, spectroscopic properties, and reactivities of the copper(I) complexes are discussed. The observed differences in the reactivities toward O2 of the copper(I) acetonitrile complexes are traced back to differences in the oxidation potentials determined by cyclic voltammetry. A special focus is set on the carbonyl complexes, where the 13C NMR and vibrational data are presented. Density functional theory (DFT) calculations are used to shed light on the differences in CO bonding in the compounds with neutral and anionic N3 ligands. In correlation with the vibrational and electrochemical data of these complexes, it is demonstrated that the C-O stretching vibration is a sensitive probe for the "electron richness" of copper(I) in these compounds.     

Synthesis and characterization of poly(pyrazolyl)borate tantalum amide complexes and their reactivities toward oxygen

Reaction of TaCl(NMe2)4 (1) with KTp* [Tp* = tris(3,5-dimethylpyrazolyl)borohydride] yields two products: Tp*Ta(NMe2)4 (2), in which one N atom of the Tp* ligand binds to Ta, and [Tp*Ta(NMe2)4]· 2KTp* (3) where three N atoms of the Tp* ligand in [Tp*Ta(NMe2)4] (2a) bind to Ta. Addition of excess 1 to 3 did not exclude KTp*. Further reaction of 2 with oxygen affords Tp*BH(NMe2) (4). TpTa(NMe2)4 (5) has been synthesized by a similar procedure through the reaction of 1 with TpK [Tp = tris(pyrazolyl)borohydride...     

Structural and spectroscopic characterization of first-row transition metal(II) substituted blue copper model complexes with hydrotris(pyrazolyl)borate

[CuL(SC(6)F(5))] (1) (L = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate anion) has been reported as a good model for blue copper proteins [Kitajima, N.; Fujisawa, K.; Tanaka, M.; Moro-oka, Y. J. Am. Chem. Soc. 1992, 114, 9232-9233]. To obtain more structural and spectroscopic insight, the first-row transition metal(II) substituted complexes of Cu(II) (1) to Mn(II) (2), Fe(II) (3), Co(II) (4), Ni(II) (5), and Zn(II) (6) were synthesized and their crystal structures were determined. These model complexes have a distorted tetrahedral geometry arising from the tripodal ligand L. The d value, which is defined by the distance from the N(2)S basal plane to the metal(II) ion, and the bond angles such as N-M-N and S-M-N are good indicators of these structural distortions. The obtained complexes were characterized by UV-vis absorption, EPR, NMR, far-IR, and FT-Raman spectroscopies and electrochemical and magnetic properties. In UV-vis absorption spectra, the sulfur-to-metal(II) CT bands and the d-d transition bands are observed for 1 and 3-5. For 1, the strong sulfur to Cu(II) CT band at 663 nm, which is one of the unique properties of blue copper proteins, is observed. The CT energies of the Fe(II) (3), Co(II) (4), and Ni(II) (5) complexes are shifted to higher energy (308 and 355 nm for 3, 311 and 340 nm for 4, 357 and 434 nm for 5) and are almost the same as the corresponding Co(II)- and Ni(II)-substituted blue copper proteins. In the far-IR spectra, three far-IR absorption bands for 2-6 at ca. 400, ca. 350, and ca. 310 cm(-1) are also observed similar to those for 1. Other properties are consistent with their distorted tetrahedral geometries.     

Tris(pyrazolyl)borate amidoborane complexes of the group 4 metals

Treatment of the tris(pyrazolyl)borate metal triamides Tp'M(NMe(2))(3), where Tp' = (C(3)H(3)N(2))(3)BH (Tp) or (3,5-Me(2)C(3)HN(2))(3)BH (Tp*) and M = Ti, Zr and Hf, with the Br?nsted acidic Lewis adduct (C(6)F(5))(3)B·NH(3) in toluene solution leads to the formation of Tp'M(NMe(2))(2){NH(2)B(C(6)F(5))(3)} complexes. The exception to this was the attempted preparation of Tp*Ti(NMe(2))(2){NH(2)B(C(6)F(5))(3)} which was unsuccessful. Where Tp' = Tp and M = Ti and Zr and where Tp' = Tp* and M = Zr the complexes have been characterized by single crystal X-ray diffraction methods, revealing the first examples of octahedral amidoborane complexes of the group 4 metals. Attempts to drive the reactions to completion resulted in competing preferential hydrolysis of the amidoborane group, regenerating (C(6)F(5))(3)B·NH(3).     

Unusual reactivity of tris(pyrazolyl)borate zirconium benzyl complexes

The synthesis and reactivity of [Tp*Zr(CH2Ph)2][B(C6F5)4] (2, Tp* = HB(3,5-Me2pz)3, pz = pyrazolyl) have been explored to probe the possible role of Tp'MR2+ species in group 4 metal Tp'MCl3/MAO olefin polymerization catalysts (Tp' = generic tris(pyrazolyl)borate). The reaction of Tp*Zr(CH2Ph)3 (1) with [Ph3C][B(C6F5)4] in CD2Cl2 at -60 degrees C yields 2. 2 rearranges rapidly to [{(PhCH2)(H)B(mu-Me2pz)2}Zr(eta2-Me2pz)(CH2Ph)][B(C6F5)4] (3) at 0 degrees C. Both 2 and 3 are highly active for ethylene polymerization and alkyne insertion. Reaction of 2 with excess 2-butyne yields the double insertion product [Tp*Zr(CH2Ph)(CMe=CMeCMe=CMeCH2Ph)][B(C6F5)4] (4). Reaction of 3 with excess 2-butyne yields [{(PhCH2)(H)B(mu-Me2pz)2}Zr(Cp*)(eta2-Me2pz)][B(C6F5)4] (6, Cp* = C5Me5) via three successive 2-butyne insertions, intramolecular insertion, chain walking, and beta-Cp* elimination.     

Step-by-step uncoordination of the pyrazolyl rings of hydrotris(pyrazolyl)borate ligands in comlexes of Rh and RhIII

Compounds of rhodium(I) and rhodium(III) that contain ancillary hydrotris(pyrazolyl)borate ligands (Tp') react with monodentate and bidentate tertiary phosphanes in a step-wise manner, with incorporation of P-donor atoms and concomitant replacement of the Tp' pyrazolyl rings. Accordingly, [Rh(kappa3-TpMe2)(C2H4)(PMe3)] (1b), converts initially into [Rh(kappa2-TpMe2)-(PMe3)2] (3), and then into [Rh(kappa1-TpMe2)-(PMe3)3] (2) upon interaction with PMe3 at room temperature, in a process which can be readily reversed under appropriate experimental conditions. Full disengagement of the Tp' ligand is feasible to give Tp' salts of rhodium(I) complex cations, for example, [Rh(CO)(dppp)2]-[TpMe2,4-Cl] (5; dppp = Ph2P(CH2)3PPh2), or [Rh(dppp)2][TpMe2,4-Cl] (6). Bis(hydride) derivatives of rhodium(III) exhibit similar substitution chemistry, for instance, the neutral complex [Rh(Tp)-(H)2(PMe3)] reacts at 20 degrees C with an excess of PMe3 to give [Rh(H)2-(PMe3)4][Tp] (9b). Single-crystal X-ray studies of 9b, conducted at 143 K, demonstrate the absence of bonding interactions between the [Rh(H)2(PMe3)4]+ and Tp ions, the closest Rh...N contact being at 4.627 A.     

Proton-assisted addition reactions on trimethylsilylalkynyl nitrosylrutheniums of hydrotris(pyrazolyl)borate

Incorporation of H₂O or HCl on treatment of trimethylsilylalkynyl nitrosylruthenium TpRuCl(CCSiMe₃)(NO) (1) (Tp = hydrotris(pyrazolyl)borate) with protic acid, and the dependence of its product formation on the reaction solvents, are reported. Reactions of 1 with HBF₄ or HCl (aq.) in MeOH gave rise to the mixture of the mono(ethynyl) TpRuCl(CCH)(NO) (2) and the mono(acyl) TpRuCl{C(O)CH₃}(NO) (3). The H₂O-incorporated 3 was quantitatively obtained from the reactions of 2 with HCl (aq.) in MeOH. On the other hand, reactions of 1 with HCl (aq.) in CH₂Cl₂ gave the η¹-α-chlorovinyl TpRuCl{C(Cl)CH₂}(NO) (4). In the bis(alkynyl) system TpRu(CCSiMe₃)₂(NO) (5), the similar reactivities were observed. Proton-assisted hydration of 5 afforded the bis(acyl) TpRu{C(O)CH₃}₂(NO) (6), while the HCl-treatment led to the formation of the bis(α-chlorovinyl) TpRu{C(Cl)CH₂}₂(NO) (7).     

Structural and near-IR photophysical studies on ternary lanthanide complexes containing poly(pyrazolyl)borate and 1,3-diketonate ligands

The ligands tris[3-(2-pyridyl)pyrazol-1-yl]hydroborate (L1, potentially hexadentate) and bis[3-(2-pyridyl)pyrazol-1-yl]dihydroborate (L2, potentially tetradentate) have been used to prepare ternary lanthanide complexes in which the remaining ligands are dibenzoylmethane anions (dbm). [Eu(L1)(dbm)2] is eight-coordinate, with L1 acting only as a tetradentate chelate (with one potentially bidentate arm pendant) and two bidentate dbm ligands. [Nd(L1)(dbm)2] was also prepared but on recrystallization some of it rearranged to [Nd(L1)2][Nd(dbm)4], which contains a twelve-coordinate [Nd(L1)2]+ cation (two interleaved hexadentate podand ligands) and the eight-coordinate anion [Nd(dbm)4]- which, uniquely amongst eight-coordinate complexes having four diketonate ligands, has a square prismatic structure with near-perfect O8 cubic coordination. Formation of this sterically unfavourable geometry is assumed to arise from favourable packing with the pseudo-spherical cation. The isostructural series of complexes [Ln(L2)(dbm)2](Ln = Pr, Nd, Eu, Gd, Tb, Er, Yb) was also prepared and all members structurally characterised; again the metal ions are eight-coordinate, from one tetradentate ligand L2 and two bidentate dbm ligands. Photophysical studies on the complexes with Ln = Pr, Nd, Er, and Yb were carried out; all show the near-IR luminescence characteristic of these metal ions, with longer lifetimes in CD3OD than in CH3OH. For [Yb(L2)(dbm)2], two species with different luminescence lifetimes were observed in CH3OH solution, corresponding to species with zero or one coordinated solvent molecules, in slow exchange on the luminescence timescale. For [Nd(L2)(dbm)2] a single average solvation number of 0.7 was observed in MeOH. For [Pr(L2)(dbm)2] a range of emission lines in the visible and NIR regions was detected; time-resolved measurements show a particularly high susceptibility to quenching by solvent CH and OH oscillators.