Hexapalladium cluster: Unique cluster construction reaction of cyclic Pd3(CNC6H3Me2-2,6)6 and linear [Pd3(CNC6H3Me2-2,6)8]

Reaction of a triangle Pd(0) complex, Pd₃(CNXyl)₆ (1; Xyl = 2,6-C₆H₃Me₂), with a dicationic linear trinuclear complex [Pd₃(CNXyl)₈][PF₆]₂ (3) afforded a dicationic hexapalladium complex [Pd₆(CNXyl)₁₂][PF₆]₂ (4), while the reaction of 1 with a dicationic dinuclear complex [Pd₂(CNXyl)₆][PF₆]₂ (2) resulted in the formation of 3. The molecular structure of the complex 4 was determined by X-ray crystallography and spectroscopic analysis.     

Intramolecular nucleophilic substitution in C6F5 moiety. The fluoride-dialkylamino exchange in decafluorodiphenlamino moiety

The reactions of [In(NEt₂)₃]₂ and Sb(NEt₂)₃ with an equimolar amount of decafluorodiphenylamine (DFDPA, LH) lead to the indium or antimony amides [(C₆F₅)₂NIn(NEt₂)₂]₂ (1) and (C₆F₅)₂NSb(NEt₂)₂ (2). Compound 2 rearranged further to give monofluoride Et₂NSb(F)[N(o-Et₂N-C₆F₄)(C₆F₅)] (3) and then difluoride F₂Sb[N(o-Et₂N-C₆F₄)₂] (4). The hydrolysis of 4 gave free ligand HN(o-Et₂N-C₆F₄)₂ (5). Closely related HN(o-Me₂N-C₆F₄)₂ (6) was prepared from the reaction of Bi(NMe₂)₃ with DFDPA. The reactions of LiN(C₆F₅)₂·THF with metal halides gave Sb[N(C₆F₅)₂]₃ (7), Me₃Sb(Br)[N(C₆F₅)₂] (8), Me₃Sb(Cl)[N(C₆F₅)₂] (9), Me₃Sb[N(C₆F₅)₂]₂ (10), [Li(THF)₂][In{N(C₆F₅)₂}₃Cl] (11). The X-ray structural investigations of 2 and 8 are presented.     

Group 12 metal aryl selenolates. Crystal and molecular structure of [2-(Et2NCH2)C6H4]2Se2 and [2-(Me2NCH2)C6H4Se]2M (M = Zn, Cd)

Diorganodiselenide [2-(Et₂NCH₂)C₆H₄]₂Se₂ (1) was obtained by hydrolysis/oxidation of the corresponding [2-(Et₂NCH₂)C₆H₄]SeLi derivative. The treatment of [2-(Et₂NCH₂)C₆H₄]₂Se₂ with elemental sodium in THF resulted in [2-(Et₂NCH₂)C₆H₄]SeNa (2). Reactions between alkali metal selenolates [2-(R₂NCH₂)C₆H₄]SeM′ (R = Me, Et; M′ = Li, Na) and MCl₂ (M = Zn, Cd) in a 2:1 molar ratio resulted in the [2-(R₂NCH₂)C₆H₄Se]₂M species [R = Me, M = Zn (3), Cd (4); R = Et, M = Zn (5), Cd (6)]. The new compounds were characterized by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, ¹¹³Cd) and mass spectrometry. The crystal and molecular structures of 1, 3 and 4 revealed monomeric species stabilized by N → Se (for 1) and N → M (for 3 and 4) intramolecular interactions.     

New versatile organyltellurium(IV) halides: Synthesis and X-ray structural features of the telluronium tellurolate salts [PhTe(CH3)2]2[TeX6] (X = Cl, Br) and [Ph3Te][PhTeX4] (X = Cl, Br, I)

TeX₄ (X = Cl, Br) react in HCl/HBr with [Ph(CH₃)₂Te]X (X = Cl, Br) to give [PhTe(CH₃)₂]₂[TeCl₆] (1) and [PhTe(CH₃)₂]₂[TeBr₆] (2). The reaction of PhTeX₃ (X = Cl, Br, I) in cooled methanol with [(Ph)₃Te]X (X = Cl, Br, I) leads to [Ph₃Te][PhTeCl₄] (3), [Ph₃Te][PhTeBr₄] (4) and [Ph₃Te][PhTeI₄] (5). In the lattices of the telluronium tellurolate salts 1 and 2, octahedral TeCl₆ and TeBr₆ dianions are linked by telluronium cations through Te?Cl and Te?Br secondary bonds, attaining bidimensional (1) and three-dimensional (2) assemblies. The complexes 3, 4 and 5 show two kinds of Te?halogen secondary interactions: the anion-anion interactions, which form centrosymmetric dimers, and two identical sets of three telluronium-tellurolate interactions, which accomplish the centrosymmetric fundamental moiety of the supramolecular arrays of the three compounds, with the tellurium atoms attaining distorted octahedral geometries. Also phenyl C-H?halogen secondary interactions are structure forming forces in the crystalline structures of compounds 3, 4 and 5.     

Lutetium gets a crown: Synthesis, structure and reaction chemistry of the separated ion pair complex, [Li(12-crown-4)2][(C5Me5)2LuMe2]

Reaction of (C₅Me₅)₂Lu(Me)(μ-Me)Li(THF)₃ (2) with excess 12-crown-4 affords the new separated ion pair complex, [Li(12-crown-4)₂][(C₅Me₅)₂LuMe₂] (3), in excellent yield. This complex reacts with 2,6-diisopropylaniline and phenylacetylene to give the methyl amide complex [Li(12-crown-4)₂][(C₅Me₅)₂Lu(Me)(NH-2,6-ⁱPr₂C₆H₃)] (4) and the bis(acetylide) complex [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5), respectively. Attempts to promote methane loss from complexes 3 and 4 to generate a lutetium methylidene or imido complex, respectively, were unsuccessful. The ability of the bis(acetylide) complex 5 to act as a π-tweezer complex was also explored. Reaction between [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5) and CuSPh gave only intractable lutetium products and the copper(I) species [Li(12-crown-4)₂][Cu(C≡C-Ph)₂] (8). The new lutetium complexes have been characterized by elemental analysis and NMR spectroscopy. Finally, the X-ray crystal structures of (C₅Me₅)₂Lu(Me)(μ-Me)Li(THF)₃ (2), [Li(12-crown-4)₂][(C₅Me₅)₂LuMe₂] (3), [Li(12-crown-4)₂][(C₅Me₅)₂Lu(Me)(NH-2,6-ⁱPr₂C₆H₃)] (4), [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5), and [Li(12-crown-4)₂][Cu(C≡C-Ph)₂] (8) are also reported.     

Synthesis and crystal structures of organometallic compounds containing the ligands C(SiMe3)2(SiMe2H) and C(SiMe2Ph)2(SiMe2H)

Metallation of (HMe₂Si)(Me₃Si)₂CH (1) by LiMe gave the organolithium compound Li(THF)₂C(SiMe₃)₂(SiMe₂H) (2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF)₄][Li{C(SiMe₃)₂(SiMe₂H)}₂] (2b). Treatment of a mixture of 1 and LiMe with KOBu^t gave KC(SiMe₃)₂(SiMe₂H) (3). This reacted with AlMe₂Cl in hexane/THF to give Al(THF)Me₂{C(SiMe₃)₂(Si Me₂H)} (4). Treatment of (HMe₂Si)(PhMe₂Si)₂CH (5) with LiMe in Et₂O/THF gave the THF adduct [Li(THF)₂C(SiMe₂Ph)₂(SiMe₂H)] (6); in the presence of KOBu^t the solvent-free [K][C(SiMe₂Ph)₂(SiMe₂H)] (7) was obtained. Crystal structure determinations showed that 6 crystallizes in a molecular lattice and 7 in an ionic lattice in which the coordination sphere of the potassium comprises phenyl groups and hydrogen atoms attached to silicon, as well as the central carbon of the bulky carbanion. Compound 7 reacted with an excess of AlMe₂Cl to give [AlClMe{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (8) and AlMe₃. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (9) was obtained as a byproduct, presumably after the accidental admission of traces of air. X-ray structural determinations showed that 8 forms halogen-bridged dimers, with the bulky ligands in the anti-configuration, and 9 forms methoxo-bridged species in which the bulky ligands are syn.     

Coordination properties of N2S (1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N2S2 (1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane or 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene) donor ligands toward Rh(I)

The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane ligand (bdtp) reacts with [Rh(COD)(THF)₂][BF₄] to give [Rh(COD)(bdtp)][BF₄] ([1][BF₄]), which is fluxional in solution on the NMR time scale. Its further treatment with carbon monoxide leads to a displacement of the 1,5-cyclooctadiene ligand, generating a mixture of two complexes, namely, [Rh(CO)₂(bdtp)][BF₄] ([2][BF₄]) and [Rh(CO)(bdtp-κ³N,N,S)][BF₄] ([3][BF₄]). In solution, [2][BF₄] exists as a mixture of two isomers, [Rh(CO)₂(bdtp-κ²N,N)]⁺ ([2a]⁺) and [Rh(CO)₂(bdtp-κ³N,N,S)]⁺ ([2b]⁺; major isomer) rapidly interconverting on the NMR time scale. At room temperature, [2][BF₄] easily loses one molecule of carbon monoxide to give [3][BF₄]. The latter is prone to react with carbon monoxide to partially regenerate [2][BF₄]. The ligands 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene (bddf) and 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) are seen to react with two equivalents of [Rh(COD)(THF)₂][BF₄] to give the dinuclear complexes [Rh₂(bddf)(COD)₂][BF₄]₂ ([4][BF₄]₂) and [Rh₂(bddo)(COD)₂][BF₄]₂ ([5][BF₄]₂), respectively. In such complexes, the ligand acts as a double pincer holding two rhodium atoms through a chelation involving S and N donor atoms. Bubbling carbon monoxide into a solution of [4][BF₄]₂ results in loss of the COD ligand and carbonylation to give [Rh₂(bddf)(CO)₄][BF₄]₂ ([6][BF₄]₂). The single-crystal X-ray structures of [3][CF₃SO₃], [5][BF₄]₂ and [6][BF₄]₂ are reported.     

Syntheses, crystal structures and DFT studies of [Me3EM(CO)5] (E = Sb, Bi; M = Cr, W), cis-[(Me3Sb)2Mo(CO)4], and [Bu3BiFe(CO)4]

Syntheses of [Me₃SbM(CO)₅] [M = Cr (1), W (2)], [Me₃BiM(CO)₅] [M = Cr (3), W (4)], cis-[(Me₃Sb)₂Mo(CO)₄] (5), [^tBu₃BiFe(CO)₄] (6), crystal structures of 1-6 and DFT studies of 1-4 are reported.     

Synthesis and structure of the silylated benzene radical anion salts [K([18]crown-6){C6H4(SiMe3)2-1,4}] and [K([18]crown-6)(THF)2][C6H2(SiMe3)4-1,2,4,5]

The crystalline compound [K([18]crown-6){C₆H₄(SiMe₃)₂-1,4}] (1) was prepared by the low-temperature reduction of the para-disilylated benzene with K/[18]crown-6 in toluene followed by recrystallisation from the same solvent. Reduction of 1,2,4,5-tetrasilylated benzene with 2(K/[18]crown-6) in toluene produced a hydrocarbon-insoluble powder identified as the dianionic derivative [K([18]crown-6)]₂[C₆H₂(SiMe₃)₄-1,2,4,5)] (2), which upon crystallisation from THF/Et₂O yielded [K([18]crown-6)(THF)₂][C₆H₂(SiMe₃)₄-1,2,4,5] (3). An X-ray diffraction study revealed that 1 comprised a contact ion pair with the crown-encapsulated K cation η⁵-connected to the planar ring of the substituted benzene radical anion, while 3 contained a well separated cation and anion.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.     

Selenium-capped trimolybdenum and tritungsten carbonyl clusters [Se2M3(CO)10] (M = Mo, W)

A facile synthesis of the novel selenium-capped trimolybdenum and tritungsten ring carbonyl clusters [Se₂M₃(CO)₁₀]²⁻ (M = Mo, 1; W, 4) have been achieved. The selenium-capped trimolybdenum cluster compound [Et₄N]₂[Se₂Mo₃(CO)₁₀] ([Et₄N]₂[1]) can be obtained from the reaction of the trichromium cluster compound [Et₄N]₂[Se₂Cr₃(CO)₁₀] with 4 equiv. of Mo(CO)₆ in refluxing acetone. On the other hand, when [Et₄N]₂[Se₂Cr₃(CO)₁₀] reacted with 4 equiv. of W(CO)₆ in refluxing acetone, the planar cluster compound [Et₄N]₂[Se₂W₄(CO)₁₈] ([Et₄N]₂[3]) was isolated, which could further transform to the tritungsten cluster compound [Et₄N]₂[Se₂W₃(CO)₁₀] ([Et₄N]₂[4]) in good yield. Alternatively, clusters 1 and 4 could be formed from the reactions of the monosubstituted products [Et₄N]₂[Se₂Cr₂M(CO)₁₀] (M = Mo; W, [Et₄N]₂[2]) with 3 equiv. of M(CO)₆ in acetone, respectively. Complexes 1-4 are fully characterized by IR, ⁷⁷Se NMR spectroscopy, and single-crystal X-ray analysis. Clusters 1, 2, and 4 are isostructural and each display a trigonal bipyramidal structure with a homometallic M₃ ring (M = Mo, 1; W, 4) or a heterometallic Cr₂W ring that is further capped above and below by μ₃-Se atoms. Further, the intermediate planar complex 3 exhibits a Se₂W₂ square with each Se atom externally coordinated to one W(CO)₅ group. This paper describes a systematic route to a series of selenium-capped trimetallic carbonyl clusters and the formation and the structural features of the resultant clusters are discussed.     

Tin(IV) complexes obtained by reacting 2-benzoylpyridine-derived thiosemicarbazones with SnCl4 and Ph2SnCl2

Reaction of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH, HL1) and its N(4)-methyl (H2Bz4Me, HL2) and N(4)-phenyl (H2Bz4Ph, HL3) derivatives with SnCl₄ and diphenyltin dichloride (Ph₂SnCl₂) gave [Sn(L1)Cl₃] (1), [Sn(L1)PhCl₂] (2), [Sn(L2)Cl₃] (3), (4) [Sn(L3)PhCl₂] (5) and [Sn(L3)Ph₂Cl] (6). Infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectra of 1-3, 5 and 6 are compatible with the presence of an anionic ligand attached to the metal through the N_py-N-S chelating system and formation of hexacoordinated tin complexes. The crystal structures of 1-3, 5 and 6 show that the geometry around the metal is a distorted octahedron formed by the thiosemicarbazone and either chlorides or chlorides and phenyl groups. The crystal structure of 4 reveals the presence of and trans [Ph₂SnCl₄]²⁻.     

Structural study on the organoantimony(III) NCN - Chelated compounds [2,6-(Me2NCH2)2C6H3]SbX2 - Influence of the polar group X

The reactions of organoantimony chloride LSbCl₂ (1) (L = [2,6-(Me₂NCH₂)₂C₆H₃]⁻) with the silver salts of selected carboxylic acids (1:2 molar ratio) resulted to the corresponding organoantimony carboxylates LSbX₂, where X = CH₃COO for (2); CF₃COO for (3). Similar reactions of 1 with the silver salt of the low nucleophilic anion (1:0.5 and 1:1 molar ratio) gave the ionic compounds [LSb(Cl)--Cl-Sb(Cl)L]⁺[CB₁₁H₁₂]⁻ (4), and [LSbCl]⁺[CB₁₁H₁₂]⁻ (5). All compounds were characterized by the help of the elemental analysis, ESI-MS, ¹H, ¹¹B, ¹³C NMR spectroscopy and IR spectroscopy. The solid state structure investigation using single crystal X-ray diffraction technique (3-5) revealed the presence of the strong Sb-N intramolecular dative connections in all cases and also significant differences in the shapes of the coordination polyhedra around the central antimony atoms was observed, i.e. a tetragonal pyramidal environment in 3 (CF₃COO groups are placed mutually in trans positions), an unusual chlorine bridged dinuclear cation consisting of one apex (Cl atom) sharing square pyramids in 4, and finally a vacant ψ-trigonal bipyramid around the central antimony atom in 5. Even more, crystallization of 5 from THF provided the single crystals of a THF aduct of 5 [LSbCl(THF)]⁺[CB₁₁H₁₂]⁻5a, where the central antimony atom is located in a tetragonal pyramidal environment. The solid state structures of 3-5 are retained in solution. Solution structure of the compound 2 was determined by the help of VT-¹H NMR spectroscopy and IR spectroscopy showing, that both carboxylates (CH₃COO) are unidentate and are placed mutually in cis positions in the coordination polyhedron around the central antimony atom. The whole coordination polyhedron in 2 might be best described as a biccaped - trigonal pyramid, due to the additional Sb-N intramolecular interactions.     

Synthesis and ethylene polymerization behavior of {MeB(3-Ph-pyrazolyl)3}TiCl3

The new methyl-tris(pyrazolyl)borate reagents Li[MeTp^Ph] (1) [MeTp^Ph]⁻ = MeB(3-Ph-pyrazolyl)₃⁻) and Tl[MeTp^Ph] (2) react with TiCl₄ to afford (MeTp^Ph)TiCl₃ (3) in 77% and 81% yield respectively. 2 reacts with ZrCl₄ and HfCl₄ to yield mixtures of products. The reaction of 1 with TiCl₃(THF)₃ proceeds with B-N bond cleavage to afford TiCl₃(3-Ph-pyrazole)(THF)₂ as the major product (30%). The reaction of 3 with MeLi (3 equiv) yields 1 (60%) and reduced Ti species, via apparent displacement of [MeTp^Ph]⁻ and generation of unstable TiCl₄Me_4−x species. Under MAO activation conditions (MAO = methylalumoxane), 3 polymerizes ethylene to linear polyethylene. 3/MAO is significantly more active in ethylene polymerization than the hydrido-tris(pyrazolyl)borate analogue {HB(3-Ph-pyrazolyl)₃}TiCl₃/MAO.     

Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

Modeling the platinum-catalyzed intermolecular hydroamination of ethylene: The nucleophilic addition of HNEt2 to coordinated ethylene in trans-PtBr2(C2H4)(HNEt2)

Compound trans-PtBr₂(C₂H₄)(NHEt₂) (1) has been synthesized by Et₂NH addition to K[PtBr₃(C₂H₄)] and structurally characterized. Its isomer cis-PtBr₂(C₂H₄)(NHEt₂) (3) has been obtained from 1 by photolytic dissociation of ethylene, generating the dinuclear trans-[PtBr₂(NHEt₂)]₂ intermediate (2), followed by thermal re-addition of C₂H₄, but only in low yields. The addition of further Et₂NH to 1 in either dichloromethane or acetone yields the zwitterionic complex trans-Pt⁽⁻⁾Br₂(NHEt₂)(CH₂CH₂N⁽⁺⁾HEt₂) (4) within the time of mixing in an equilibrated process, which shifts toward the product at lower temperatures (ΔH° = −6.8 ± 0.5 kcal/mol, ΔS° = 14.0 ± 2.0 e.u., from a variable temperature IR study). ¹H NMR shows that free Et₂NH exchanges rapidly with H-bonded amine in a 4·NHEt₂ adduct, slowly with the coordinated Et₂NH in 1, and not at all (on the NMR time scale) with Pt-NHEt₂ or -CH₂CH₂N⁽⁺⁾HEt₂ in 4. No evidence was obtained for deprotonation of 4 to yield an aminoethyl derivative trans-[PtBr₂(NHEt₂)(CH₂CH₂NEt₂)]⁻ (5), except as an intermediate in the averaging of the diasteretopic methylene protons of the CH₂CH₂N⁽⁺⁾HEt₂ ligand of 4 in the higher polarity acetone solvent. Computational work by DFT attributes this phenomenon to more facile ion pair dissociation of 5·Et₂NH₂⁺, obtained from 4·Et₂NH, facilitating inversion at the N atom. Complex 4 is the sole observable product initially but slow decomposition occurs in both solvents, though in different ways, without observable generation of NEt₃. Addition of TfOH to equilibrated solutions of 4, 1 and excess Et₂NH leads to partial protonolysis to yield NEt₃ but also regenerates 1 through a shift of the equilibrium via protonation of free Et₂NH. The DFT calculations reveal also a more favourable coordination (stronger Pt-N bond) of Et₂NH relative to PhNH₂ to the Pt^II center, but the barriers of the nucleophilic additions of Et₂NH to the C₂H₄ ligand in 1 and of PhNH₂ to trans-PtBr₂(C₂H₄)(PhNH₂) (1a) are predicted to be essentially identical for the two systems.     

Synthesis, characterization, protonation studies and X-ray crystal structure of ReH5(PPh3)2(PTA) (PTA = 1,3,5-triaza-7-phosphaadamantane)

The novel rhenium pentahydride complex [ReH₅(PPh₃)₂(PTA)] (2) was synthesized by dihydrogen replacement from the reaction of [ReH₇(PPh₃)₂] with PTA in refluxing THF. Variable temperature NMR studies indicate that 2 is a classic polyhydride (T_1(min) = 133 ms). This result agrees with the structure of 2, determined by X-ray crystallography at low temperature. The compound shows high conformational rigidity which allows for the investigation of the various hydride-exchanging processes by NMR methods. Reactions of 2 with equimolecular amounts of either HFIP or HBF₄ · Et₂O at 183 K afford [ReH₅(PPh₃)₂{PTA(H)}]⁺ (3) via protonation of one of the nitrogen atoms on the PTA ligand. When 5 equivalents of HBF₄ · Et₂O are used, additional protonation of one hydride ligand takes place to generate the thermally unstable dication [ReH₄(η²-H₂)(PPh₃)₂{PTA(H)}]²⁺ (4), as confirmed by ¹H NMR and T₁ analysis. IR monitoring of the reaction between 2 and CF₃COOD at low temperature shows the formation of the hydrogen bonded complex [ReH₅(PPh₃)₂{PTA?DOC(O)CF₃}] (5) and of the ionic pair [ReH₅(PPh₃)₂{PTA(D)?OC(O)CF₃}] (6) preceding the proton transfer step leading to 3.     

Synthesis and structure of halogen derivatives of 9-dimethylsulfonium-7,8-dicarba-nido-undecaborane [9-Me2S-7,8-C2B9H11]

Halogenation of 9-dimethylsulfonium-7,8-dicarba-nido-undecaborane [9-SMe₂-7,8-C₂B₉H₁₁] with N-chlorosuccinimide, bromine and iodine gave the expected corresponding halogen derivatives [9-SMe₂-11-X-7,8-C₂B₉H₁₀], where X = Cl (1), Br (2), I (3). In the bromination reaction, [9-SMe₂-6-Br-7,8-C₂B₉H₁₀] (4) was isolated as a minor product being the first example of substitution at a “lower” belt of the 7,8-dicarba-nido-undecaborate cage. The use of excess of bromine resulted in dibromo derivative [9-SMe₂-6,11-Br₂-7,8-C₂B₉H₉] (5). Structures of the compounds prepared were determined using ¹¹B-¹¹B COSY NMR spectroscopy (for all halogen derivatives) and single crystal X-ray diffraction (for compounds 2, 3, and 5).     

Synthesis and structure of new aryltellurenyl halides derived from (dmpTe)2 (dmp = 2,6-dimethoxyphenyl)

[RTeTeR] (R = dmp = 2,6-dimethoxyphenyl) (1) reacts with bromine to give [RTeTe(Br)₂R] (2) and [RTeBr₃] (3), and with SOCl₂ to yield [RTeTe(Cl)₂R] (5) and [RTeCl₃] (6). The recrystallization of compound 3 in acetone produces [RTeBr₂(CH₂-C(O)-CH₃)] (4). The hydrolysis of 2 in aqueous ammonia and methanol containing media affords the methoxy/oxo-derivative [RTe(μ-O)(OCH₃)]₂ (7). All the title compounds were obtained with good yields, and strong Te?O_(methoxy), as well as Te?X (X = Br, Cl) secondary interactions, support the distorted octahedral configurations shown mostly in the polymeric compounds 3, 4, 5 and 6. Complexes 2 and 5 close the series of compounds with the structure [RTeTe(X)₂R] (X = Cl, Br, I), started earlier with [RTeTe(I)₂R].     

Trifluoroacetylacetonate rhodium(III) methyl complexes, cis-[Rh(TFA)(PPh3)2(CH3)(L)][BPh4] and cis-[Rh(TFA)(PPh3)2(CH3)(I)] (L = CH3CN, NH3, pyridine), in comparison with their acetylacetonate analogs

The oxidative addition of CH₃I to planar rhodium(I) complex [Rh(TFA)(PPh₃)₂] in acetonitrile (TFA is trifluoroacetylacetonate) leads to the formation of cationic, cis-[Rh(TFA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1), or neutral, cis-[Rh(TFA)(PPh₃)₂(CH₃)(I)] (4), rhodium(III) methyl complexes depending on the reaction conditions. 1 reacts readily with NH₃ and pyridine to form cationic complexes, cis-[Rh(TFA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (2) and cis-[Rh(TFA)(PPh₃)₂(CH₃)(Py)][BPh₄] (3), respectively. Acetylacetonate methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(I)] (5), was obtained by the action of NaI on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] in acetone at −15 °C. Complexes 1-5 were characterized by elemental analysis, ³¹P{¹H}, ¹H and ¹⁹F NMR. For complexes 2, 3, 4 conductivity data in acetone solutions are reported. The crystal structures of 2 and 3 were determined. NMR parameters of 1-5 and related complexes are discussed from the viewpoint of their isomerism.