Reactions of pentaborane(9) with electron-rich molybdenum and tungsten phosphine polyhydrides

Reaction of [W(PMe₂Ph)₃H₆] with pentaborane(9) gives nido-2-[W(PMe₂Ph)₃H₂B₄H₈] (1) as well as nido-2-[W(PMe₂Ph)₃HB₅H₁₀] (2). The crystal structure of (2) has been determined. Compound (2) has a novel metallaborane structure containing an edge-bridging {BH₃} group between the tungsten atom and one of the basal boron atoms in a “nido-WB₄” pyramid. Reaction of [W(PMe₃)₄(η²-CH₂PMe₂)H] with pentaborane(9) gives nido-2-[W(PMe₃)₃H₂B₄H₈] (3) whilst reaction of [Mo(L)₄H₄] with pentaborane(9) gives nido-2-[Mo(L)₃H₂B₄H₈] [L = PMe₃ (4), PMe₂Ph (5)]. Treatment of [Mo(PMe₃)₄H₄] with excess BH₃ · thf gives the known borohydride [Mo(PMe₃)₄H(η²-BH₄)].     

Formation of ferraboranes from pentaborane(9) or BH3 · thf and an electron-rich cyclopentadienyl iron phosphine hydride

[(η⁵-C₅R₅)Fe(PMe₃)₂H] (R = H, Me) can be made in good yields in a simple one-pot reaction between FeCl₂, PMe₃, C₅R₅H (R = H, Me) and Na/Hg in thf. Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with pentaborane(9) gives the known metallaborane [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (1) in improved yield as well as the new metallaboranes [(η-C₅H₅)-nido-2-FeB₅H₈{μ-5,6-Fe(η⁵-C₅H₅)(PMe₃)(μ-6,7-H)}] (2), [(η-C₅H₅)(PMe₃)-arachno-2-FeB₃H₈] (3), [(η⁵-C₅H₅)₂-capped-nido-2,3-Fe₂B₄H₈] (4), [(η⁵-C₅H₅)-nido-2-FeB₄H₇(PMe₃)] (5) and [(η⁵-C₅H₅)-nido-2-FeB₅H₈(PMe₃)] (6). Reaction of [(η⁵-C₅Me₅)Fe(PMe₃)₂H] with pentaborane(9) gives predominantly [(η⁵-C₅Me₅)-nido-2-FeB₅H₁₀] (7) and [(η⁵-C₅Me₅)(PMe₃)-arachno-2-FeB₃H₈] (8). Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with 2 equiv. of BH₃ · thf gives low yields of ferrocene and compound 3. Compound 7 thermally isomerises to the apical isomer [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (9) in low yield. Compounds 1 and 7 deprotonate cleanly in the presence of KH at the unique B-H-B bridge to give [(η⁵-C₅H₅)-nido-2-FeB₅H₉⁻][K⁺] (10) and [(η⁵-C₅Me₅)-nido-2-FeB₅H₉⁻][K⁺] (11) respectively, whilst 6 deprotonates more slowly at one of two equivalent B-H-B bridges to give the fluxional anion [(η⁵-C₅H₅)-nido-2-FeB₅H₇(PMe₃)⁻] (12).     

Polyhedral metallathiaborane chemistry: Synthesis and characterisation of metallathiaboranes based on the twelve-vertex icosahedral closo-{MSB10H10} unit, where M is Rh or Ir

The reaction of [nido-7-SB₁₀H₁₂] with [RhCl(PPh₃)₃] in the presence of N,N,N′N′-tetramethylnaphthalene-1,8-diamine (tmnd) in CH₂Cl₂ gives twelve-vertex [2,2-(PPh₃)₂-2-H-closo-2,1-RhSB₁₀H₁₀] (1) and eleven-vertex [8,8-(PPh₃)₂-nido-8,7-RhSB₉H₁₀] (2), as major products, plus the dimeric species [{(PPh₃)-closo-RhSB₁₀H₁₀}₂] (3) as a minor product. Reaction of 1 with PMe₂Ph in CH₂Cl₂ results in phosphine exchange and hydride substitution, affording the chloro analogue of 1, [2,2-(PMe₂Ph)₂-2-Cl-closo-2,1-RhSB₁₀H₁₀] (4). By contrast, reaction between [IrCl(PPh₃)₃] and [nido-7-SB₁₀H₁₂] in CH₂Cl₂ with tmnd affords only one product, twelve-vertex [2,2-(PPh₃)₂-2-H-closo-2,1-IrSB₁₀H₁₀] (5). [RhCl₂(η⁵-C₅Me₅)]₂ with [nido-7-SB₁₀H₁₂] under the same conditions gives twelve-vertex [2-(η⁵-C₅Me₅)-closo-2,1-RhSB₁₀H₁₀] (6). All the compounds are characterised by NMR spectroscopy, and by mass spectrometry, and the molecular structure of [2,2-(PMe₂Ph)₂-2-Cl-closo-2,1-RhSB₁₀H₁₀] (4) was established by single-crystal X-ray diffraction analysis. This last rhodathiaborane 4 is fluxional in solution through a process that involves a reversible partial rotation of the {RhCl(PMe₂Ph)₂} unit above the {SB₄} pentagonal face of the {SB₁₀H₁₀} fragment.     

Synthesis and structures of 3-sila-β-diketiminato complexes of the coinage metals

The dimeric copper(I) 3-sila-β-diketiminate [Cu{(N(R)C(Ar))₂SiR}]₂ · (thf) (1) was obtained from CuI and [Li{(N(R)C(Ar))₂SiR}(thf)₂] (B) in toluene (R = SiMe₃, Ar = C₆H₃Me₂-2,6). When [CuI(PPh₃)₃] was used as a starting material, the LiI-containing compound [Cu{Si(R)(C(Ar)N(R))₂Li(μ-I)}(PPh₃)] (2) was isolated. The reaction of [MI(PPh₃)_n] (M = Ag, n = 3; M = Au, n = 2) with two equivalents of B in toluene gave the isomorphous silver and gold 3-sila-β-diketiminates [M{Si(R)(C(Ar)N(R))₂Li}₂(μ-I)] [M = Ag (3), Au (4)]. Each of 1-4 was characterised by the multinuclear NMR spectroscopy and single-crystal X-ray diffraction crystallography.     

Syntheses and characterization of cyano-bridged homo and hetero bimetallic complexes containing η and η-cyclic hydrocarbons

The reactions of [(ind)Ru(PPh₃)₂CN] (ind = η⁵-C₉H₇) (1) and [CpRu(PPh₃)₂CN] (Cp = η⁵-C₅H₅) (2) with [(η⁶-p-cymene)Ru(bipy)Cl]Cl (bipy = 2,2′-bipyridine) (3) in the presence of AgNO₃/NH₄BF₄ in methanol, respectively, yielded dicationic cyano-bridged complexes of the type [(ind)(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (4) and [Cp(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (5). The reaction of [CpRu(PPh₃)₂CN] (2), [CpOs(PPh₃)₂CN] (6) and [CpRu(dppe)CN] (7) with the corresponding halide complexes and [(η⁶-p-cymene)RuCl₂]₂ formed the monocationic cyano-bridge complexes [Cp(PPh₃)₂Ru(μ-CN)Os(PPh₃)₂Cp](BF₄) (8), [Cp(PPh₃)₂Os(μ- CN)Ru(PPh₃)₂Cp](BF₄) (9) and [Cp(dppe)Ru(μ-CN)Os(PPh₃)₂Cp](BF₄) (10) along with the neutral complexes [Cp(PPh₃)₂Ru(μ-CN)Ru (η⁶-p-cymene)Cl₂] (11), [Cp(PPh₃)₂Os(μ-CN)Ru(η⁶-p-cymene)Cl₂] (12), and [Cp(dppe) Ru(μ-CN)Ru(η⁶-p-cymene)Cl₂] (13). These complexes were characterized by FT IR, ¹H NMR, ³¹P{¹H} NMR spectroscopy and the molecular structures of complexes 4, 8 and 11 were solved by X-ray diffraction studies.     

Diastereoselectivity at chiral metal center of half-sandwich-type ruthenium complexes with planar-chiral cyclopentadienyl ligands in multiple ligand transfer reaction

The triple ligand transfer reaction between planar-chiral cyclopentadienyl-ruthenium complexes [Cp′Ru(NCMe)₃][PF₆] (1) (Cp′ = 1-(COOR²)-2-Me-4-R¹C₅H₂; R¹ = Me, Ph, t-Bu) and iron complexes CpFe(CO)(L)X (2) (L = PMe₃, PMe₂Ph, PMePh₂, PPh₃; X = I, Br) resulted in the formation of metal-centered chiral ruthenium complexes Cp′Ru(CO)(L)X (3) in moderate yields with diastereoselectivities of up to 68% de. The configurations of some major diastereomers were determined to be by X-ray crystallography. The diastereoselectivity of 3 was under kinetic control and not affected by the steric effect of the substituents on the Cp′ ring of 1 and the phosphine of 2. Although the double ligand transfer reaction between [Cp′Ru{P(OMe)₃}(NCMe)₂][PF₆] (7) and CpFe(CO)₂X (8) produced Cp′Ru{P(OMe)₃}(CO)X (9), the selectivity at the ruthenium center was low.     

Synthesis and reactivity of hydride and dihydrogen complexes of ruthenium with tris(pyrazolyl)borate and phosphite ligands

Chloro phosphite complexes RuClTpL(PPh₃) (1a, 1b) [L = P(OEt)₃, PPh(OEt)₂] and RuClTp[P(OEt)₃]₂ (1c) [Tp = hydridotris(pyrazolyl)borate] were prepared by allowing RuClTp(PPh₃)₂ to react with an excess of phosphite. Treatment of the chloro complexes 1 with NaBH₄ in ethanol yielded the hydride RuHTpL(PPh₃) (2a, 2b) and RuHTp[P(OEt)₃]₂ (2c) derivatives. Protonation reaction of 2 with Brønsted acids was studied and led to thermally unstable (above 10 °C) dihydrogen [Ru(η²- H₂)TpL(PPh₃)]⁺ (3a, 3b) and [Ru(η²-H₂)Tp{P(OEt)₃}₂]⁺ (3c) complexes. The presence of the η²-H₂ ligand is indicated by short T_1 min values and J_HD measurements of the partially deuterated derivatives. Aquo [RuTp(H₂O)L(PPh₃)]BPh₄ (4), carbonyl [RuTp(CO)L(PPh₃)]BPh₄ (5), and nitrile [RuTp(CH₃CN)L(PPh₃)]BPh₄ (6) derivatives [L = P(OEt)₃] were prepared by substituting H₂ in the η²-H₂ derivatives 3. Vinylidene [RuTp{CC(H)R}L(PPh₃)]BPh₄ (7, 8) (R = Ph, ^tBu) and allenylidene [RuTp(CCCR1R2)L(PPh₃)]BPh₄ (9-11) complexes (R1 = R2 = Ph, R1 = Ph R2 = Me) were also prepared by allowing dihydrogen complexes 3 to react with the appropriate HCCR and HCCC(OH)R1R2 alkynes. Deprotonation of vinylidene complexes 7, 8 with NEt₃ was studied and led to acetylide Ru(CCR)TpL(PPh₃) (12, 13) derivatives. The trichlorostannyl Ru(SnCl₃)TpL(PPh₃) (14) compound was also prepared by allowing the chloro complex RuClTpL(PPh₃) to react with SnCl₂ · 2H₂O in CH₂Cl₂.     

Dimerization of terminal alkynes catalyzed by chloro(η-pentadienyl) bis(triphenylphosphine)ruthenium(II) and kinetics of phosphine substitution

Exchange of PMe₂Ph for PPh₃ in (η⁵-pentadienyl)ruthenium{bis(triphenylphosphine)}chloride, (η⁵-C₅H₇)Ru(PPh₃)₂Cl (1) under first order conditions proceeds rapidly in THF at room temperature. A pseudo-first order rate constant of 17 ± 2 × 10⁻⁴ s⁻¹ is obtained for the reaction at 21 °C. The rate constant is essentially independent of the phosphine concentration. The activation parameters, ΔH^† = 16.1 ± 0.4 kcal mol⁻¹ and ΔS^† = −16 ± 1 cal K⁻¹ mol⁻¹ differ from those reported for phosphine exchange in CpRu(PPh₃)₂Cl (2) and (η⁵-indenyl)Ru(PPh₃)₂Cl (3). The reaction of 1 with PMe₂Ph is about 70 times faster than the reaction of 2 at 30 °C and some 40 times faster than the reaction of 3 at 20 °C. (η⁵-C₅H₇)Ru(PPh₃)₂Cl(1) is more active than the ruthenium(II) complexes 2, 3, and TpRu(PPh₃)₂Cl (4) in the catalytic dimerization of terminal alkynes with nearly quantitative conversion of PhCCH and FcCCH at ambient temperature in 24 h. The enhanced substitution rate is accompanied by >50% conversion of phenylacetylene to oligomeric products. Reaction of 1 with NaPF₆ in acetonitrile yields the cationic ruthenium(II) complex [(η⁵-C₅H₇)Ru(PPh₃)₂(CH₃CN)][PF₆] (7). The latter complex is much less active in reactions with phenylacetylene than 1 but avoids the formation of oligomeric products.     

Nucleophilic substitution reactions at the Si-Cl bonds of the dichloro(methyl)silyl ligand in five- and six-coordinate complexes of ruthenium(II) and osmium(II)

Treatment of either RuHCl(CO)(PPh₃)₃ or MPhCl(CO)(PPh₃)₂ with HSiMeCl₂ produces the five-coordinate dichloro(methyl)silyl complexes, M(SiMeCl₂)Cl(CO)(PPh₃)₂ (1a, M = Ru; 1b, M = Os). 1a and 1b react readily with hydroxide ions and with ethanol to give M(SiMe[OH]₂)Cl(CO)(PPh₃)₂ (2a, M = Ru; 2b, M = Os) and M(SiMe[OEt]₂)Cl(CO)(PPh₃)₂ (3a, M = Ru; 3b, M = Os), respectively. 3b adds CO to form the six-coordinate complex, Os(SiMe[OEt]₂)Cl(CO)₂(PPh₃)₂ (4b) and crystal structure determinations of 3b and 4b reveal very different Os-Si distances in the five-coordinate complex (2.3196(11) Å) and in the six-coordinate complex (2.4901(8) Å). Reaction between 1a and 1b and 8-aminoquinoline results in displacement of a triphenylphosphine ligand and formation of the six-coordinate chelate complexes M(SiMeCl₂)Cl(CO)(PPh₃)(κ²(N,N)-NC₉H₆NH₂-8) (5a, M = Ru; 5b, M = Os), respectively. Crystal structure determination of 5a reveals that the amino function of the chelating 8-aminoquinoline ligand is located adjacent to the reactive Si-Cl bonds of the dichloro(methyl)silyl ligand but no reaction between these functions is observed. However, 5a and 5b react readily with ethanol to give ultimately M(SiMe[OEt]₂)Cl(CO)(PPh₃)(κ²(N,N-NC₉H₆NH₂-8) (6a, M = Ru; 6b, M = Os). In the case of ruthenium only, the intermediate ethanolysis product Ru(SiMeCl[OEt])Cl(CO)(PPh₃)(κ²(N,N-NC₉H₆NH₂-8) (6c) was also isolated. The crystal structure of 6c was determined. Reaction between 1b and excess 2-aminopyridine results in condensation between the Si-Cl bonds and the N-H bonds with formation of a novel tridentate “NSiN” ligand in the complex Os(κ³(Si,N,N)-SiMe[NH(2-C₅H₄N)]₂)Cl(CO)(PPh₃) (7b). Crystal structure determination of 7b shows that the “NSiN” ligand coordinates to osmium with a “facial” arrangement and with chloride trans to the silyl ligand.     

Ruthenium and rhodium nitrosyl complexes containing dichalcogenoimidodiphosphinate ligands

Interaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(R₂PS)₂] in refluxing N,N-dimethylformamide afforded trans-[Ru(NO)Cl{N(R₂PS)₂}₂] (R = Ph (1), Prⁱ (2)). Reaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(Ph₂PSe)₂] led to formation of a mixture of trans-[Ru(NO)Cl{N(Ph₂PSe)₂}₂] (3) and trans-[Ru(NO)Cl{N(Ph₂PSe)₂}{Ph₂P(Se)NPPh₂}] (4). Reaction of Ru(NO)Cl₃ · xH₂O with K[N(Ph₂PO)₂] afforded cis-[Ru(NO)(Cl){N(Ph₂PO)₂}₂] (5). Treatment of [Rh(NO)Cl₂(PPh₃)₂] with K[N(R₂PQ)₂] gave Rh(NO){N(R₂PQ)₂}₂] (R = Ph, Q = S (6) or Se (7); R = Prⁱ, Q = S (8) or Se (9)). Protonation of 8 with HBF₄ led to formation of trans-[Rh(NO)Cl{HN(Prⁱ₂PS)₂}₂][BF₄]₂ (10). X-ray diffraction studies revealed that the nitrosyl ligands in 2 and 4 are linear, whereas that in 9 is bent with the Rh–N–O bond angle of 125.7(3)°.     

Synthesis, and characterization of ruthenium(II) polypyridyl complexes containing α-amino acids and its DNA binding behavior

Reactivity of the ruthenium complexes [Ru(κ³-tptz)(PPh₃)Cl₂] (1) and [Ru(κ³-tpy)(PPh₃)Cl₂] (2) [tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine; tpy = 2,2′:6′,2″-terpyridine] with several α-amino acids [glycine (gly); leucine (leu); isoleucine (isoleu); valine (val); tyrosine (tyr); proline (pro) and phenylalanine (phe)] have been investigated. Cationic complexes with the general formulations [Ru(κ³-L)(κ²-L″)(PPh₃)]⁺ (L = tptz or tpy; L″ = gly, leu, isoleu, val, tyr, pro, and phe] have been isolated as tetrafluoroborate salts. The resulting complexes have been thoroughly characterized by analytical, spectral and electrochemical studies. Molecular structures of the representative complexes [Ru(κ³-tptz)(val)(PPh₃)]BF₄ (6)_, [Ru(κ³-tpy)(leu)(PPh₃)]BF₄ (10) and [Ru(κ³-tpy)(tyr)(PPh₃)]BF₄ (13) have been determined crystallographically. The complexes [Ru(κ³-tptz)(leu)(PPh₃)]BF₄ (4), [Ru(κ³-tptz)(val)(PPh₃)]BF₄ (6), [Ru(κ³-tpy)(leu)(PPh₃)]BF₄ (10) [Ru(κ³-tpy)(tyr)(PPh₃)] BF₄·3H₂O (13) exhibited DNA binding behavior and acted as mild Topo II inhibitors (10-40%). The complexes also inhibited heme polymerase activity of the malarial parasite Plasmodium yoelii lysate.     

Synthesis and reactivity of ruthenium complexes with 1,1′-dithiolate ligands

Reactions of [Ru(PPh₃)₃Cl₂] with ROCS₂K in THF at room temperature and at reflux gave the kinetic products trans-[Ru(PPh₃)₂(S₂COR)₂] (R = ⁿPr 1, ⁱPr 2) and the thermodynamic products cis-[Ru(PPh₃)₂(S₂COR)₂] (R = ⁿPr 3, ⁱPr 4), respectively. Treatment of [RuHCl(CO)(PPh₃)₃] with ROCS₂K in THF afforded [RuH(CO)-(S₂COR)(PPh₃)₂] (R = ⁿPr 5, ⁱPr 6) as the sole isolable products. Reaction of [RuCl₂(PPh₃)₃] with tetramethylthiuram disulfide [Me₂NCS₂]₂ gave a Ru(III) dithiocarbamate complex, [Ru(PPh₃)₂(S₂CNMe₂)Cl₂] (7). This reaction involved oxidation of ruthenium(II) to ruthenium(III) by the disulfide group in [Me₂NCS₂]₂. Treatment of 7 with 1 equiv. of [M(MeCN)₄][ClO₄] (M = Cu, Ag) gave the stable cationic ruthenium(III)-alkyl complexes [Ru{C(NMe₂)QC(NMe₂)S}(S₂CNMe₂)(PPh₃)₂][ClO₄] (Q = O 8, S 9) with ruthenium-carbon bonds. The crystal structures of complexes 1, 2, 4·CH₂Cl₂, 6, 7·2CH₂Cl₂, 8, and 9·2CH₂Cl₂ have been determined by single-crystal X-ray diffraction. The ruthenium atom in each of the above complexes adopts a pseudo-octahedral geometry in an electron-rich sulfur coordination environment. The 1,1′-dithiolate ligands bind to ruthenium with bite S-Ru-S angles in the range of 70.14(4)-71.62(4)°. In 4·CH₂Cl₂, the P-Ru-P angle for the mutually cis PPh₃ ligands is 103.13(3)°, the P-Ru-P angles for other complexes with mutually trans PPh₃ ligands are in the range of 169.41(4)-180.00(6)°. The alkylcarbamate [C(NMe₂)QC(NMe₂)S]⁻ (Q = O, S) ligands in 8 and 9 are planar and bind to the ruthenium centers via the sulfur and carbon atoms from the CS and NC double bonds, respectively. The Ru-C bond lengths are 1.975(5) and 2.018(3) Å for 8 and 9·2CH₂Cl₂, respectively, which are typical for ruthenium(III)-alkyl complexes. Spectroscopic properties along with electrochemistry of all complexes are also reported in the paper.     

Molecular and spectroscopic properties of hydridecarbonyl ruthenium complexes with pyrazine carboxylic acid ligands

The hydride carbonyl ruthenium(II) [RuH(CO)(pyzCOO)(PPh₃)₂] (1), [RuH(CO)(pyz-2,3-COO[CH₃])(PPh₃)₂]·H₂O (2) and dinuclear Ru(II)/Ru(III) [RuH(CO)(PPh₃)(pyz-2,3-COO)Ru(CO)Cl₂(PPh₃)₂] (3) complexes were synthesized and characterized by IR, ¹H, ³¹P NMR, UV-Vis spectroscopy and X-ray crystallography. The experimental studies were complemented by quantum chemical calculations, which were used to identify the nature of the interactions between the ligands and the central ion, and the orbital composition in the frontier electronic structure. Based on a molecular orbital scheme, the calculated results allowed the interpretation of the UV-Vis spectra obtained at an experimental level. The luminescence property of the complex 2 was determined. The ac magnetic susceptibility measurements showed a residual magnetism evidenced by the small values of the molar susceptibility, not exceeding 0.5 emu/mol at 2 K, a lack of a Curie-Weiss region and weak magnetic interactions below 20 K.     

Synthesis and characterization of new paramagnetic tetraaryl derivatives of chromium and molybdenum

The low-temperature reaction of [CrCl₃(thf)₃] with LiC₆H₃Cl₂-2,6 yields the organochromium(III) compound [Li(thf)₄][Cr^III(C₆H₃Cl₂-2,6)₄] (1) in 48% yield. The homoleptic, anionic species [Cr^III(C₆H₃Cl₂-2,6)₄]⁻ is electrochemically related to the neutral one [Cr^IV(C₆H₃Cl₂-2,6)₄] (2) through a reversible one-electron exchange process (E_1/2 = 0.16 V, ΔE_p = 0.09 V, i_pa/i_pc = 1.18). Compound 2 was isolated in 74% yield by chemical oxidation of 1 with [N(C₆H₄Br-4)₃][SbCl₆]. Attempts to prepare the salt [NBu₄][Cr^III(C₆Cl₅)₄] (4) by direct arylation of [CrCl₃(thf)₃] with LiC₆Cl₅ in the presence of [NBu₄]Br gave the organochromium(II) salt [NBu₄]₂[Cr^II(C₆Cl₅)₄] (3) instead, as the result of a reduction process. The salt [NBu₄][Cr^III(C₆Cl₅)₄] (4) was cleanly prepared by comproportionation of 3 and [Cr^IV(C₆Cl₅)₄]. The reaction of [MoCl₄(dme)] with LiC₆Cl₅ in Et₂O solution proceeded with oxidation of the metal center to give the paramagnetic (S = 1/2), five-coordinate salt [Li(thf)₄][Mo^VO(C₆Cl₅)₄] (5). The crystal and molecular structures of 1 and 2 have been established by X-ray diffraction methods. The magnetic properties of 1 and 4 (S = 3/2) as well as those of 2 (S = 1) have been established by EPR spectroscopy as well as by ac and dc magnetization measurements.     

Synthesis of [Ru(CO)2(PPh3)(SP)] and [Ru(CO)(PPh3)2(SP)] and their catalytic activities for the hydroamination of phenylacetylene

The reaction of [Ru(CO)₂(PPh₃)₃] (1) with o-styryldiphenylphophine (SP) (2) gave [Ru(CO)₂(PPh₃)(SP)] (3) in 83% yield. This styrylphosphine ruthenium complex 3 can also be synthesized by the reaction of [Ru(p-MeOC₆H₄NN)(CO)₂(PPh₃)₂]BF₄ (4) with NaBH₄ and 2 in 50% yield. When “Ru(CO)(PPh₃)₃” generated by the reaction of [RuH₂(CO)(PPh₃)₃] (8) with trimethylvinylsilane reacted with 2, [Ru(CO)(PPh₃)₂(SP)] (10) was produced in moderate yield as an air sensitive solid. The spectral and X-ray data of these complexes revealed that the coordination geometries around the ruthenium center of both complexes corresponded to a distorted trigonal bipyramid with the olefin occupying the equatorial position and the C-C bonding in the olefin moiety in 3 and 10 contained a significant contribution from a ruthenacyclopropane limiting structure. Complexes 3 and 10 showed catalytic activity for the hydroamination of phenylacetylene 11 with aniline 12. Ruthenium complex 3 in the co-presence of NH₄PF₆ or H₃PW₁₂O₄₀ proves to be a superior catalyst system for this hydroamination reaction. In the case of the reaction using H₃PW₁₂O₄₀ as an additive, ketimines (13) was obtained in 99% yield at a ruthenium-catalyst loading of 0.1 mol%. Some aniline derivatives such as 4-methoxy, 4-trifluoromethyl-, and 4-bromoanilines can also be used in this hydroamination reaction.     

Synthesis and characterisation of [AlMen{Si(SiMe3)3}3−n(thf)] (n = 1 or 2)

The crystalline compounds [AlMe_n{Si(SiMe₃)₃}_3−n(thf)] [n = 2 (1) or 1 (2)] were prepared from the lithium sisyl [Li{Si(SiMe₃)₃}(thf)₃] (A) and the appropriate methylaluminium chloride [AlCl_3−nMe_n] in thf. The X-ray structure of 1 is reported. Unlike A or a magnesium sisyl [Mg{Si(SiMe₃)₃}₂(thf)₂] (B), neither 1 nor 2 underwent an insertion reaction with an α-H-free nitrile.     

Reaction of aryl azides with tris(trimethylsilyl)silyllithium: Synthesis of tmeda or thf adducts of [Li{N(Ar)Si(SiMe3)3}] and 1,4-trimethylsilyl migration from oxygen to nitrogen

Reaction of ArN₃ (Ar = Ph, p-MeC₆H₄, 1-naphthyl) with [Li{Si(SiMe₃)₃}(thf)₃] yielded lithium amides [Li{N(Ar)Si(SiMe₃)₃}L] (L = tmeda or (thf)₂). Similar treatment of o-phenylene diazide with 2 equiv. of [Li{Si(SiMe₃)₃}(thf)₃] formed dilithium diamide complex 4. Reaction between o-Me₃SiOC₆H₄N₃ and [Li{Si(SiMe₃)₃}(thf)₃] afforded, via 1,4-trimethylsilyl migration from oxygen to nitrogen, [Li{OC₆H₄{N(SiMe₃)Si(SiMe₃)₃}-2}]₂ (5). The structures of complexes 3 and 5 have been determined by single crystal X-ray diffraction techniques.     

Bio-catalysts and catalysts based on ruthenium(II) polypyridyl complexes imparting diphenyl-(2-pyridyl)-phosphine as a co-ligand

Reactions of the ruthenium complexes [Ru(κ³-tpy)(PPh₃)Cl₂], [Ru(κ³-tptz)(PPh₃)Cl₂] and [Ru(κ³-tpy)Cl₃] [tpy = 2,2′:6′,2′′-terpyridine; tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine] with diphenyl-(2-pyridyl)-phosphine (PPh₂Py) have been investigated. The complexes [Ru(κ³-tpy)(PPh₃)Cl₂] and [Ru(κ³-tptz)(PPh₃)Cl₂] reacted with PPh₂Py to afford [Ru(κ³-tpy)(κ¹-P-PPh₂Py)₂Cl]⁺ (1) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py)₂Cl]⁺ (2), which were isolated as their tetrafluoroborate salts. Under analogous conditions, [Ru(κ³-tpy)Cl₃] gave a neutral complex [Ru(κ³-tpy)(κ¹-PPh₂Py)Cl₂] (3). Upon treatment with an excess of NH₄PF₆ in methanol, 1 and 2 gave [Ru(κ³-tpy)(κ¹-P-PPh₂Py)(κ²-P,N-PPh₂Py)](PF₆)₂ (4) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py)(κ²-P,N-PPh₂Py)](PF₆)₂ (5) containing both monodentate and chelated PPh₂Py. Further, 4 and 5 reacted with an excess of NaCN and CH₃CN to afford [Ru(κ³-tpy)(κ¹-P-PPh₂Py)₂(CN)](PF₆) (6), [Ru(κ³-tpy)(κ¹-P-PPh₂Py)₂(NCCH₃)](PF₆)₂ (7), [Ru(κ³-tptz)(κ¹-P-PPh₂Py)₂(CN)]PF₆ (8) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py)₂(NCCH₃)](PF₆)₂ (9) supporting hemi labile nature of the coordinated PPh₂Py. The complexes have been characterized by elemental analyses, spectral (IR, NMR, electronic absorption, FAB-MS), electrochemical studies and structures of 1, 2 and 3 determined by X-ray single crystal analyses. At higher concentration level (40 μM) the complexes under investigation exhibit inhibitory activity against DNA-Topo II of the filarial parasite S. cervi and 3 catalyses rearrangement of aldoximes to amide under aerobic conditions.     

Synthesis, spectroscopy and structures of palladium(II) and platinum(II) complexes containing mercapto-o-carborane

The reactions of [M₂Cl₂(μ-Cl)₂(PMe₂Ph)₂] with mercapto-o-carboranes in the presence of pyridine afforded mono-nuclear complexes of composition, [MCl(SCb°R)(py)(PMe₂Ph)] (M = Pd or Pt; Cb° = o-C₂B₁₀H₁₀; R = H or Ph). The treatment of [PdCl₂(PEt₃)₂] with PhCb°SH yielded trans-[Pd(SCb°Ph)₂(PEt₃)₂] (4) which when left in solution in the presence of pyridine gave another substitution product, [Pd(SCb°Ph)₂(py)(PEt₃)] (5). The structures of [PdCl(SCb°Ph)(py)(PMe₂Ph)] (1), [Pd(SCb°Ph)₂(PEt₃)₂] (4) and [Pd(SCb^oPh)₂(py)(PEt₃)] (5) were established unambiguously by X-ray crystallography. The palladium atom in these complexes adopts a distorted square-planar configuration with neutral donor atoms occupying the trans positions. Thermolysis of [PdCl(SCb°)(py)(PMe₂Ph)] (2) in TOPO (trioctylphosphine oxide) at 200 °C gave nanocrystals of TOPO capped Pd₄S which were characterized by XRD pattern and SEM.     

Heterocyclic thioamides of copper(I): Synthesis and crystal structures of copper complexes with 1,3-imidazoline-2-thiones in the presence of triphenyl phosphine

Reaction of copper(I) chloride with 1,3-imidazoline-2-thione (imzSH) in the presence of Ph₃P in 1:2:2 or 1:1:2 (M:L:PPh₃) molar ratios yielded a compound of unusual composition, [Cu₂(imzSH)(PPh₃)₄Cl₂] · CH₃OH (1), whose X-ray crystallography has shown that its crystals consist of four coordinated [CuCl(1κS-imzSH)(PPh₃)₂] (1a), and three coordinated [Cu(PPh₃)₂Cl] (1b) independent molecules in the same unit cell. In contrast, crystals of complexes of copper(I) bromide/iodide are formed by single molecules of [CuBr(1κS-imzSH)(PPh₃)₂] · H₂O (2) and [CuI(1κS-imzSH)(PPh₃)₂] (3), respectively, similar to molecule 1a. The related ligand, 1,3-benzimidazoline-2-thione (bzimSH) formed a complex [CuBr(1κS-bzimSH)(PPh₃)₂] · CH₃COCH₃ (4), similar to 2. The formation of 1a and 1b has been also revealed by NMR spectroscopy. The NMR spectra of 2–4 also showed weak signals indicating formation of compounds similar to 1b. It reveals that the lability of the Cu–S bond varies in the order: Cl ? Br ∼ I. Weak interactions {e.g. C–H?π electrons of ring, –NH?halogens/oxygen, C–H?halogens/oxygen, π?π (between rings)} have played an important role in building 2D chains of complexes 1–4.