Reactions of 2-pyridinethiolate cobalt(III) complexes with pyridinethiolate or benzenethiolate ligands

Four half-sandwich cobalt complexes, Cp^∗Co(2-PyS)₂ (2), Cp^∗Co(2-PyS)₂ · HI (3), Cp^∗Co(2-PyS) (4-PyS) (4), (Cp^∗Co)₂(μ-PhS)₂(μ-2-PyS)I (5) [Cp^∗ = pentamethylcyclopentadienyl, 2-PyS = 2-pyridinethiolate, 4-PyS = 4-pyridinethiolate, PhS = benzenethiolate] were successfully synthesized by the reactions of 2-pyridinethione, lithium 4-pyridinethiolate and lithium benzenethiolate with Cp^∗Co(2-PyS)I (1), respectively. Complexes 2 and 3 have the structures with two 2-pyridinethiolates ligands coordinated to the cobalt atom. Two different pyridinethiolates ligands can be identified in complex 4. The molecular structure of 5 consists of two Cp^∗-Co fragments, which are triply bridged by three sulfur atoms from different ligands. The molecular structures of 3 and 5 were determined by X-ray crystallographic analysis. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.     

Syntheses and molecular structures of 18/16-electron half-sandwich iridium(III) complexes with chelating anilido-imine ligands

A 18-electron complex Cp^∗IrCl[o-C₆H₄N(C₆H₃-Me-p) (CHNC₆H₃-Me-p)] (Cp^∗ = η⁵-pentamethylcyclopentadienyl) (1a) was obtained by the reaction of the lithium salt of o-C₆H₄N (C₆H₃-Me-p)(CHNHC₆H₃-Me-p) (L₁) with [Cp^∗IrCl(μ-Cl)]₂ in toluene. However, when bulkier ligands (L₂ = o-C₆H₄N(C₆H₃-Me-p)(CHNHC₆H₃-i-Me₂-2,6), L₃ = o-C₆H₄N(C₆H₃-Me-p) (CHNHC₆H₃-i-Pr₂-2,6)) were employed in the same reaction, two 16-electron complexes {Cp^∗Ir[o-C₆H₄N(C₆H₃-Me-p)(CHNC₆H₃-i-Me₂-2,6)]}⁺Cl⁻ (2b) and {Cp^∗Ir[o-C₆H₄N(C₆H₃-Me-p)(CHNC₆H₃-i-Pr₂-2,6)]}⁺Cl⁻ (3b) were formed. A 16-electron complex {Cp^∗Ir [o-C₆H₄N(C₆H₃-Me-p) (CHNC₆H₃-Me-p)]}⁺SO₃ CF⁻₃ (1b) bearing L₁ could be achieved by the reaction of 1a with AgSO₃CF₃ in CH₃CN solution. The molecular structures of 1a and 2b were determined by X-ray crystallography. Theoretical calculations of all the 18/16-electron species were performed to study their bonding characters and electronic properties. Electron donating effect of Cp^∗ and steric effect of anilido-imine ligand were considered as major factors in the formation of coordinative unsaturated complexes 1b, 2b, 3b.     

Synthesis and characterization of hetero-binuclear Co-Rh complexes [CpCoS2C2(B9H10)][Rh(COD)] and [CpCoSe2C2(B10H10)][Rh(COD)]

Two hetero-binuclear complexes [Cp^∗CoS₂C₂(B₉H₁₀)][Rh(COD)] (2a) and [Cp^∗CoSe₂C₂(B₁₀H₁₀)][Rh(COD)] (2b) [Cp^∗ = η⁵-pentamethylcyclopentadienyl, COD = cyclo-octa-1,5-diene (C₈H₁₂)] were synthesized by the reactions of half-sandwich complexes [Cp^∗CoE₂C₂(B₁₀H₁₀)] [E = S (1a), Se (1b)] with low valent transition metal complexes [Rh(COD)(OEt)]₂ and [Rh(COD)(OMe)]₂. Although the reaction conditions are the same, the structures of two products for dithiolato carborane and diselenolato carborane are different. The cage of the carborane in 2a was opened; However, the carborane cage in 2b was intact. Complexes 2a and 2b have been fully characterized by ¹H, ¹¹B NMR and IR spectroscopy, as well as by elemental analyses. The molecular structures of 2a and 2b have been determined by single-crystal X-ray diffraction analyses and strong metal-metal interactions between cobalt and rhodium atoms (2.6260 Å (2a) and 2.7057 Å (2b)) are existent.     

Half-sandwich Ru(II), Ir(III) and Rh(III) complexes with bridging or chelating N-heterocyclic bis-carbene ligand: Synthesis and characterization

N-heterocyclic bis-carbene ligand (bis-NHC) which was derived from 1,1′-diisopropyl-3,3′-ethylenediimidazolium dibromide (L·2HBr) via silver carbene transfer method, reacted with [(η⁶-p-cymene)RuCl₂]₂ and [Cp^∗MCl₂]₂ (Cp^∗ = η⁵-C₅Me_5, M = Ir, Rh) respectively, afforded complexes [(η⁶-p-cymene)RuCl₂]₂(L) (1), [Cp^∗IrCl₂]₂(L) (2) and [Cp^∗RhCl(L)][Cp^∗RhCl₃] (3). When [Cp^∗IrCl₂]₂ was treated with 2 equiv AgOTf at first, and then reacted with bis-NHC ligand, [Cp^∗IrCl(L)]OTf (4) was obtained. The molecular structures of complexes 1-4 were determined by X-ray single crystal analysis, showing that 1 and 2 adopted bridging coordination mode, 3 and 4 adopted chelating coordination mode. All of these complexes were characterized by ¹H, ¹³C NMR spectroscopy and element analysis.     

Synthesis and characterization of half-sandwich iridium complexes containing 2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene and ancillary ortho-carborane-1,2-dichalcogenolato ligands

The binuclear half-sandwich iridium complexes {Cp^∗IrCl₂}₂(μ-2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene) (3) and {Cp^∗Ir[E₂C₂(B₁₀H₁₀)]}₂(μ-2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene) (E = S(5a), Se(5b)) were prepared from the reaction of [Cp^∗IrCl(μ-Cl)]₂ or the “pseudo-aromatic” half-sandwich iridium complex Cp^∗Ir[E₂C₂(B₁₀H₁₀)] (E = S(4a), Se(4b)) with a tetrathiafulvalene (TTF) derivative 2,6-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene (2) at room temperature. The complexes (3, 5a and 5b) have been fully characterized by IR and NMR spectroscopy, as well as elemental analysis. And the molecular structures of 2 and 5a were established through X-ray crystallography. It is interesting that infinite tunnels are created by repeating ‘buckled bowl’ molecules of 5a.     

Insertion of nitrene and chalcogenolate groups into the Ir-C σ bond in a cyclometalated iridium(III) complex

Treatment of [Cp∗Ir(ppy)Cl] (Cp∗ = η⁵-C₅Me₅, ppyH = 2-(2-pyridyl)phenyl) with Ag(OTf) (OTf⁻ = triflate) in MeOH and MeCN gave the solvento complexes [Cp∗Ir(ppy)(solv)][OTf] (solv = MeOH (1) and MeCN (2)). Complex 1 is capable of catalyzing oxidation and azirdination of styrene with PhIO and PhINTs (Ts = tosyl), respectively. Treatment of 2 with a stoichiometric amount of PhINTs resulted in the insertion of the NTs group into the Ir-C(ppy) bond and formation of [Cp∗Ir(η²-ppy-NTs)(MeCN)][OTf] (3). Treatment of 1 with R₂E₂ afforded [Cp∗Ir(ppy)(η¹-R₂E₂)][OTf] (E = S (4), Se (5), Te (6)). Reactions of 4 and 5 with Ag(OTf) resulted in cleavage of the E-E bond and insertion of an ER group into the Ir-C(ppy) bond. The crystal structures of complexes 2-6 and [Cp∗Ir(η²-ppy-S-p-tol)(H₂O)][OTf]₂ have been determined.     

Half-sandwich rhodium complexes containing both N-heterocyclic carbene and ortho-carborane-1,2-dithiolate ligands

A new route was used to synthesize half-sandwich rhodium complexes containing both N-heterocyclic carbenes (NHC) and carborane ligands. The rhodium carbene complexes Cp^∗Rh(L)[S₂C₂(B₁₀H₁₀)] (Cp^∗ = pentamethylcyclopentadienyl, L = 1,3-dimethylimidazolin-2-ylidene; 4) can be obtained from the reaction of Cp^∗Rh(L)Cl₂ (2) with Li₂S₂C₂(B₁₀H₁₀) or from the reaction of Cp^∗Rh[S₂C₂(B₁₀H₁₀)] (3) with silver-NHC complex prepared by direct reaction of an imidazolium precursor and Ag₂O. Complexes 2 and 4 were characterized by IR, NMR spectroscopy, element analysis and X-ray structure analyses.     

Synthesis and characterization of heterometallic Rh/Ru complexes supported by 1,2-dichalcogenolato-o-carborane ligands

The 16-electron half-sandwich complexes Cp^∗Rh[E₂C₂(B₁₀H₁₀)] (E = S, 1a; Se, 1b) react with [Ru(COD)Cl₂]_x under different conditions to give different types of heterometallic complexes. When the reactions were carried out in THF for 24 h, the binuclear Rh/Ru complexes [Cp^∗Rh(μ-Cl)₂(COD)Ru][E₂C₂(B₁₀H₁₀)] (E = S, 2a; Se, 2b) bridged by two Cl atoms and the binuclear Rh/Rh complexes (Cp^∗Rh)₂[E₂C₂(B₁₀H₁₀)] (E = S, 3a; Se, 3b) with direct Rh-Rh bond can be isolated in moderate yields. [Ru(COD)Cl₂] fragments in 2a and 2b have inserted into the Rh-E bond. If the [Ru(COD)Cl₂]_x was reacted with 1a in the presence of K₂CO₃ in methanol solution, the product [Cp^∗Rh(COD)]Ru[S₂C₂(B₁₀H₁₀]] (4a), K[(μ-Cl)(μ-OCH₃)Ru(COD)]₄ (5a) and 3a were obtained. The B(3)-H activation in complex 4a was found. However, when the reaction between 1b and [Ru(COD)Cl₂]_x was carried out in excessive NaHCO₃, the carborane cage opened products {Cp^∗Rh[S₂C₂(B₉H₁₀)]}Ru(COD) (6b), {Cp^∗Rh[S₂C₂(B₉H₉)]}Ru(COD)(OCH₃) (7b) and 3b were obtained. All complexes were fully characterized by their IR, ¹H NMR and elemental analyses. The molecular structures of 2a, 2b, 3b, 4a, 5a, and 7b have been determined by X-ray crystallography.     

Conformational study of lanthanide(III) complexes of N-(2-salicylaldiminatobenzyl)-1-aza-18-crown-6 by using X-ray and ab initio methods

A structural study of lanthanide complexes with the deprotonated form of the monobracchial lariat ether N-2-salicylaldiminatobenzyl-aza-18-crown-6 (L⁴) (Ln = La(III)–Tb(III)) is presented. Attempts to isolate complexes of the heaviest members of the lanthanide series were unsuccessful. The X-ray crystal structures of [Pr(L⁴)(H₂O)](ClO₄)₂ · H₂O · C₃H₈O and [Sm(L⁴)(H₂O)](ClO₄)₂ · C₃H₈O show the metal ion being bound to the eight donor atoms of the ligand backbone. Coordination number nine is completed by the oxygen atom of an inner-sphere water molecule. Two different conformations of the crown moiety (labelled as A and B) are observed in the solid state structure of the Pr(III) complex, while for the Sm(III) complex only conformation A is observed. The complexes were also characterized by means of theoretical calculations performed in vacuo at the HF level, by using the 3-21G^∗ basis set for the ligand atoms and a 46 + 4fⁿ effective core potential for lanthanides. The optimized geometries of the Pr(III) and Sm(III) complexes show an excellent agreement with the experimental structures obtained from X-ray diffraction studies. The calculated relative energies of the A and B conformations for the different [Ln(L⁴)(H₂O)]²⁺ complexes (Ln = La, Pr, Sm, Ho or Lu) indicate a progressive stabilization of the A conformation with respect to the B one upon decreasing the ionic radius of the Ln(III) ion. For the [Ln(L⁴)(H₂O)]²⁺ systems, most of the calculated bond distances between the metal ion and the coordinated donor atoms decrease along the lanthanide series, as usually observed for Ln(III) complexes. However, our ab initio calculations provide geometries in which the Ln–O(5) bond distance [O(5) is an oxygen atom of the crown moiety] increases across the lanthanide series from Sm(III) to Lu(III).     

Crystal structures of (azido)(pentamethylcyclopentadienyl)iridium(III) complexes containing various types of bidentate ligands

Several (azido)iridium(III) complexes having a pentamethylcyclopentadienyl (Cp∗) group, [Cp∗Ir(N₃)₂(Ph₂Ppy-κP)] (1: Ph₂Ppy = 2-diphenylphosphinopyridine), [Cp∗Ir(N₃)(Ph₂Ppy-κP,κN)]CF₃SO₃ (2), [Cp∗Ir(N₃)(dmpm)]PF₆ (3: dmpm = bis(dimethylphosphino)methane), [Cp∗Ir(N₃)(Ph₂Pqn)]PF₆·$·$CH₃OH (4·$·$CH₃OH: Ph₂Pqn = 8-diphenylphosphinoquinoline), and [Cp∗Ir(N₃)(pybim)] (5: Hpybim = 2-(2-pyridyl)benzimidazole) have been prepared and their crystal structures have been analyzed by X-ray diffraction. In complex 1, the Ph₂Ppy ligand is only coordinated via the P atom (-κP), while in 2 it acts as a bidentate ligand through the P and N atoms (-κP,κN) to form a four-membered chelate ring. Comparing the structural parameters of the chelate ring in 2 with those of a similar five-membered chelate ring formed by Ph₂Pqn in 4, it became apparent that the angular distortion in the Ph₂Ppy-κP,κN ring was remarkable, although the Ir–P and Ir–N bonds in the Ph₂Ppy-κP,κN ring were not elongated very much from the corresponding bonds in the Ph₂Pqn-κP,κN ring. In the pybim complex 5, the five-membered chelate ring was coplanar with the pyridine and benzimidazolyl rings. With the related (azido)iridium(III) complexes analyzed previously, comparison of the structural parameters of the Ir–N₃ moiety in [Cp∗Ir^III(N₃)(L–L′)]^+/0 complexes reveals an anomalous feature of the 2,2′-bipyridyl (bpy) complex, [Cp∗Ir(N₃)(bpy)]PF₆.     

Straightforward synthesis of phosphametallocenium cations of Rh and Ir

Reaction of 3,4-dimethylphospholylthallium (Tl-1) with [Cp^∗MCl₂]₂ (M = Rh, Ir) leads to the formation of the dimeric species [(Cp^∗M)₂(Me₂C₄H₂P)₃]⁺2 and 3 with bridging μ-η¹:η¹-phospholyl ligands. The phosphametallocenium sandwich complexes [Cp^∗M(Me₂C₄(SiMe₃)₂P)]⁺7 (M = Rh) and 8 (M = Ir) could be obtained from the reaction of [Cp^∗MCl₂]₂ and the 2,5-bis(trimethylsilyl)-1-trimethylstannylphosphole 6, with the bulky trimethylsilyl groups preventing the phosphole from η¹- and enforcing a η⁵-coordination. The structures of phospharhodocenium cation 7 and a byproduct 9 containing a phosphairidocenium moiety could be determined by X-ray diffraction.     

Formations and electrochemical behavior of mononuclear and binuclear molybdenum dithiolene complexes with nitrosyl ligands: Evidence for the formation of a coordinatively unsaturated species [CpMo(NO)(dithiolene)]

The one-pot reaction of [Cp^∗Mo(NO)(CO)₂] with elemental sulfur and dimethyl acetylenedicarboxylate (C₂Z₂ (Z = COOMe)) gave the [2+2] cycloadduct of the mononuclear molybdenum dithiolene complex [Cp^∗Mo(NO)(S₂C₂Z₂)(C₂Z₂)] (1), and some binuclear complexes:[Cp^∗Mo(NO)(S₂C₂Z₂)]₂ (2), [Cp^∗₂Mo₂(NO)₂S₂(S₂C₂Z₂)] (3) and [Cp^∗Mo(NO)S₂]₂ (4).The reaction of [Cp^∗Mo(NO)(Cl)(μ-Cl)]₂ with OC{S₂C₂(COOMe)₂} in the presence of sodium methoxide also produced complex 2 and the paramagnetic Cp^∗Mo bisdithiolene complex [Cp^∗Mo(S₂C₂Z₂)₂] (5, Z = COOMe).The structures of complexes 1-5 were determined by X-ray crystal structure analysis.The nitrosyl ligands of complexes 1-4 showed a linear coordination to the molybdenum center (the Mo-N-O bond angles = 169-174°), and their N-O bond lengths were 1.17-1.20 Å.In the binuclear complexes 2-4, two nitrosyl ligands were placed at cis-position.Complexes 1 and 2 were characterized by cyclic voltammetry and spectroelectrochemistry (visible and IR). The electrochemical reduction of the dimeric complex 2 formed the monomeric dithiolene complex[Cp^∗Mo(NO)(S₂C₂Z₂)]⁻ (X⁻) whose lifetime was several minutes. When the anion X⁻ was electrochemically oxidized, the coordinatively unsaturated species X was generated, but it was immediately dimerized to afford the original dimeric complex 2. The reduction of the complex 1 included the elimination of the bridged DMAD moiety (C₂Z₂) to give the anion X⁻.     

Synthesis and structural aspects of M-allyl (M = Ir, Rh) complexes

The synthesis, characterization and chemistry of novel η³-allyl metal complexes (M = Ir, Rh) are described. The structures of compounds (C₅Me₄H)Ir(PPh₃)Cl₂ (1), (C₅Me₄H)Ir(PPh₃)(η³-1-methylallyl)Br (3a), (C₅Me₄H)Ir(η⁴-1,3,5-hexatriene) (8), and (C₅Me₅)Rh(η³-1-ethylallyl)Br (5d) have been determined by X-ray crystallography. Structural comparisons among these complexes are discussed. It is found that the neutral metal allylic complex [Cp^∗IrCl(η³-methylallyl)] (5) ionizes in polar solvents to give [Cp^∗Ir(η³-methylallyl)]⁺Cl⁻ (6) and reaches equilibrium (5 ? 6) at room temperature. Addition of tertiary phosphine ligands to neutral complexes such as [Cp^∗Ir(η³-methylallyl)Cl], results in the formation of stable ionic phosphine adducts. Factors such as solvent, length of carbon chain, temperature and light are discussed with respect to the formation, stability and structure of the allyl complexes.     

Some complexes containing carbon chains end-capped by M(CO)2Tp′ [M = Mo, W; Tp′ = HB(pz)3, HB(dmpz)3] groups

Complexes M(CCCSiMe₃)(CO)₂Tp′ (Tp′ = Tp [HB(pz)₃], M = Mo 2, W 4; Tp′ = Tp^∗ [HB(dmpz)₃], M = Mo 3) are obtained from M(CCCSiMe₃)(O₂CCF₃)(CO)₂(tmeda) (1) and K[Tp′].Reactions of 2 or 4 with AuCl(PPh₃)/K₂CO₃ in MeOH afforded M{CCCAu(PPh₃)}(CO)₂Tp′ (M = Mo 5, W 6) containing C₃ chains linking the Group 6 metal and gold centres.In turn, the gold complexes react with Co₃(μ₃-CBr)(μ-dppm)(CO)₇ to give the C₄-bridged {Tp(OC)₂M}CCCC{Co₃(μ-dppm)(CO)₇} (M = Mo 7, W 8), while Mo(CBr)(CO)₂Tp^∗ and Co₃{μ₃-C(CC)₂Au(PPh₃)}(μ-dppm)(CO)₇ give {Tp^∗(OC)₂Mo}C(CC)₂C{Co₃(μ-dppm)(CO)₇} (9) via a phosphine-gold(I) halide elimination reaction. The C₃ complexes Tp′(OC)₂MCCCRu(dppe)Cp^∗ (Tp′ = Tp, M = Mo 10, W 11; Tp′ = Tp^∗, M = Mo 12) were obtained from 2-4 and RuCl(dppe)Cp^∗ via KF-induced metalla-desilylation reactions. Reactions between Mo(CBr)(CO)₂Tp^∗ and Ru{(CC)_nAu(PPh₃)}(dppe)Cp^∗ (n = 2, 3) afforded {Tp^∗(OC)₂Mo}C(CC)_n{Ru(dppe)Cp^∗} (n = 2 13, 3 14), containing C₅ and C₇ chains, respectively. Single-crystal X-ray structure determinations of 1, 2, 7, 8, 9 and 12 are reported.     

Catalytic hydrogenation of CO and CN bonds via heterolysis of H2 mediated by metal-sulfur bonds of rhodium and iridium thiolate complexes

Coordinatively unsaturated rhodium and iridium complexes having a bulky thiolate, [Cp∗M(PMe₃)(SDmp)](BAr^F₄) (1a: M = Rh; 1b: M = Ir; Dmp = 2,6-(mesityl)₂C₆H₃, Ar^F = 3,5-(CF₃)₂C₆H₃), catalyzed the hydrogenation of benzaldehyde, N-benzylideneaniline, and cyclohexanone, under 1 atm of H₂ at low temperatures. In these catalytic reactions, the M-H/S-H complexes [Cp∗M(PMe₃)(H)(HSDmp)](BAr^F₄) (2a: M = Rh; 2b: M = Ir) generated via H₂ heterolysis by 1a or 1b were suggested to transfer both M-H hydride and S-H proton to substrates. The catalytic reactions were terminated by the dissociation of H-SDmp from the metal centers of 2a and 2b that occurs at ambient temperature under H₂ atmosphere.     

Addition of benzenethiol to terminal alkynes catalyzed by hydrotris(3,5-dimethylpyrazolyl)borate-Rh(III) bis(thiolate) complex: Mechanistic studies with characterization of the key intermediate

The Rh(III)-thiolate complex [Tp^∗Rh(SPh)₂(MeCN)] (2; Tp^∗ = hydrotris(3,5-dimethylpyrazolyl)borate) readily undergoes substitution of MeCN by XyNC (Xy = 2,6-dimethylphenyl) to give the isocyanide complex [Tp^∗Rh(SPh)₂(XyNC)] (3), whereas reaction of 2 with terminal alkynes results in the formation of the rhodathiacyclobutene complex [Tp^∗Rh(SPh){η²-CHCR(SPh)}] (4; R = aryl, alkyl). Molecular structures of 3 and 4 (R = CH₂Ph) have been determined by single crystal X-ray diffraction. Complex 2 as well as [Tp^∗Rh(cyclooctene)(MeCN)] have been found to catalyze regioselective addition of benzenethiol to terminal alkynes RCCH at 50 °C to give R(PhS)CCH₂ in moderate to high yields. The above products are selectively formed when R = CH₂Ph and n-C₆H₁₃, while cis-RCHCHSPh and RC(SPh)₂CH₃ are also obtained as by-products when R = p-MeOC₆H₄. Catalytic cycle involving 2 and 4 is proposed based on the mechanistic studies using NMR measurement.     

Synthesis of sulfido- and thiolato-bridged Ir3 cluster and its reactions with alkyne and isocyanide including highly regioselective cyclotrimerization of methyl propiolate

Reactions of a sulfido- and thiolato-bridged diiridium complex [(Cp^∗Ir)₂(μ-S)(μ-SCH₂CH₂CN)₂] (Cp^∗ = η⁵-C₅Me₅) with [(Cp^∗MCl)₂(μ-Cl)₂] (M = Ir, Rh) afforded the sulfido- and thiolato-bridged trinuclear clusters [(Cp^∗M)(Cp^∗Ir)₂(μ₃-S)(μ₂-SCH₂CH₂CN)₂(μ₂-Cl)]Cl (4: M = Ir, 5: M = Rh). Upon treatment with XyNC (Xy = 2,6-Me₂C₆H₃) in the presence of KPF₆ at 60 °C, 4 was converted into a mixture of a mononuclear XyNC complex [Cp^∗Ir(SCH₂CH₂CN)(CNXy)₂][PF₆] (6) and a dinuclear XyNC complex [{Cp^∗Ir(CNXy)}₂(μ-S)(μ-SCH₂CH₂CN)][PF₆] (7). On the other hand, reactions of 4 and 5 with methyl propiolate in the presence of KPF₆ at 60 °C resulted in the formation of a cyclic trimer of the alkyne 1,3,5-C₆H₃(COOMe)₃ as the sole detectable organic product. The reactions proceeded catalytically with retention of the cluster cores of 4 and 5, whereby the activity of the former was much higher than that of the latter.     

Reactions of Ru(Cp) complexes with P(o-tolyl)3

Reaction of [Ru(Cp^∗)(CH₃CN)₃](PF₆) with P(o-tolyl)₃ affords [Ru(Cp^∗){(η⁶-o-tolyl)P(o-tolyl)₂}](PF₆) (4) in which the P-atom is not coordinated to the metal. The solid-state structure of 4 has been determined. A related reaction with P(p-tolyl)₃ reveals a small quantity [Ru(Cp^∗){(η⁶-p-tolyl)P(o-tolyl)₂}](PF₆), in solution, but mostly the expected bis-phosphine complex. Reaction of the Ru(IV) dication, [Ru(Cp^∗)(η³-PhCHCHCH₂)(DMF)₂](PF₆)₂, with P(o-tolyl)₃ gives a mixture of the phosphonium salt, C₆H₅CHCHCH₂P(o-tolyl)₃ (9) and the dication [Ru(Cp^∗) (η⁶-C₆H₅CHCHCH₂P(o-tolyl)₃)](PF₆)₂ (10). Salt 9 forms via attack of the P-atom on the allyl ligand. The latter product results from complexation of 9 via the phenyl group of the former allyl ligand. It would seem that the sterically demanding P(o-tolyl)₃ ligand is not readily compatible with the Ru(Cp^∗) fragment, in either the +2 or +4 oxidation state. Detailed NMR studies are reported.     

Synthesis, structure and characterization of dimolybdaheteroboranes

Chalcogen-stabilized dimolybdaboranes 3-5 (3: [(Cp^∗Mo)₂B₄H₅Se(Ph)], 4: [(Cp^∗Mo)₂B₄H₃Se₂(SeCH₂Ph)] and 5: [(Cp^∗Mo)₂B₃H₆(BSR)(μ-η¹-SR)] (R = 2,6-(^tBu)₂-C₆H₂OH)) have been isolated from the mild pyrolysis of dichalcogenide ligands, RE-E‘R (R = Ph: E = S, E‘ = Se; R = CH₂Ph, [2,6-(^tBu)₂-C₆H₂OH]: E = E‘ = Se, S) and [(Cp^∗Mo)₂B₄H₈], 2, an intermediate generated from the reaction of [Cp^∗MoCl₄] (1) (Cp^∗ = η⁵-C₅Me₅), with [LiBH₄.thf]. The geometry of [(Cp^∗Mo)₂B₄H₅Se(Ph)] is similar to that of [(Cp^∗Mo)₂B₅H₉], in which one BH₃ unit on the open face is replaced by a triple bridged selenium atom. All the compounds have been characterized in solution by ¹H, ¹¹B, ¹³C NMR and IR spectroscopy and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 3-5.     

Synthetic and X-ray diffraction studies of borosiloxane cages [R′Si(ORBO)3SiR′] and the adducts of [BuSi{O(PhB)O}3SiBu] with pyridine or N,N,N′,N′-tetramethylethylenediamine

Eleven borosiloxane [R′Si(ORBO)₃SiR′] compounds where R′ = Bu^t and R = Ph (1), 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), 4-CH(O)C₆H₄ (5), CpFeC₅H₄ (6), 4-C(O)CH₃C₆H₄ (7), 4-ClC₆H₄ (8), 2,4-F₂C₆H₃ (9), and R′ = cyclo-C₆H₁₁ and R = Ph (10), and 4-BrC₆H₄ (11) have been synthesized and characterized by spectroscopic (IR, NMR), mass spectrometric and, for compounds where R′ = Bu^t and R = 4-PhC₆H₄ (2), 4-Bu^tC₆H₄ (3), 3-NO₂C₆H₄ (4), CpFeC₅H₄ (6) and 2,4-F₂C₆H₃ (9), X-ray diffraction studies. These compounds contain trigonal planar RBO₂ and tetrahedral R′SiO₃ units located around 11-atom “spherical” Si₂O₆B₃ cores. The dimensions of the Si₂O₆B₃ cores in compounds 2, 3, 4, 6 and 9 are remarkably similar. The reaction between [Bu^tSi{O(PhB)O}₃SiBu^t] (1), and excess pyridine yields the 1:1 adduct [Bu^tSi{O(PhB)O}SiBu^t]. NC₅H₅ (12) while the reaction between 1 and N,N,N′,N′-tetramethylethylenediamine in equimolar amounts affords a 2:1 borosiloxane:amine adduct [Bu^tSi{O(PhB)O}₃SiBu^t]₂ · Me₂NCH₂CH₂NMe₂ (13). Compounds 12 and 13 were characterised with IR and (¹H, ¹³C and¹¹B) NMR spectroscopies and the structure of the pyridine complex 12 was determined with X-ray techniques.