Reactions of Organic Azides with Half‐sandwich Complexes of Iridium: Preparation of Mono‐ and Bis(imine) Derivatives

Imine complexes [IrCl(η⁵‐C₅Me₅){κ¹‐NH=C(H)Ar}{P(OR)₃}]BPh₄ ( 1 , 2 ) (Ar = C₆H₅, 4‐CH₃C₆H₄; R = Me, Et) were prepared by allowing chloro complexes [IrCl₂(η⁵‐C₅Me₅){P(OR)₃}] to react with benzyl azides ArCH₂N₃. Bis(imine) complexes [Ir(η⁵‐C₅Me₅){κ¹‐NH=C(H)Ar}₂{P(OR)₃}](BPh₄)₂ ( 3 , 4 ) were also prepared by reacting [IrCl₂(η⁵‐C₅Me₅){P(OR)₃}] first with AgOTf and then with benzyl azide. Depending on the experimental conditions, treatment of the dinuclear complex [IrCl₂(η⁵‐C₅Me₅)]₂ with benzyl azide yielded mono‐ [IrCl₂(η⁵‐C₅Me₅){κ¹‐NH=C(H)Ar}] ( 5 ) and bis‐[IrCl(η⁵‐C₅Me₅){κ¹‐NH=C(H)Ar}₂]BPh₄ ( 6 ) imine derivatives. In contrast, treatment of chloro complexes [IrCl₂(η⁵‐C₅Me₅){P(OR)₃}] with phenyl azide C₆H₅N₃ gave amine derivatives [IrCl(η⁵‐C₅Me₅)(C₆H₅NH₂){P(OR)₃}]BPh₄ ( 7 , 8 ). The complexes were characterized spectroscopically (IR, NMR) and by X‐ray crystal structure determination of [IrCl(η⁵‐C₅Me₅){κ¹‐NH=C(H)C₆H₄‐4‐CH₃}{P(OEt)₃}]BPh₄ ( 2b ).     

Metallorganische Verbindungen der Lanthanoide. 113. [(tert-Butylcyclopentadienyl)(cyclopentadienyl)dimethylsilan]-Komplexe ausgewählter Lanthanoide

Organometallic Compounds of the Lanthanides. 113. [(tert-Butylcyclopentadienyl)(cyclopentadienyl)dimethylsilane] Complexes of selected Lanthanides The reaction of [Me₂Si(C₅H₄)(tBuC₅H₃)]Li₂ with LnCl₃ (Ln = Y, Nd, Sm, Lu) in THF results in the formation of the chiral, dimeric complexes [Me₂Si(C₅H₄)(tBuC₅H₃)]Ln(μ-Cl)₂Li(THF)(Et₂O) [Ln = Y ( 1 ), Nd ( 2 ), Sm ( 3 ), Lu ( 4 )]. The ¹H-, ¹³C-NMR- and the mass spectra of the new compounds as well as the X-ray crystal structures of 2 a and 3 a were discussed.     

Synthese und Charakterisierung von Aquapentachloroplatinaten(IV) – Struktur von [K(18-Krone-6)][PtCl5(H2O)]

Synthesis and Characterization of Aquapentachloroplatinates(IV) – Structure of [K(18-crown-6)][PtCl₅(H₂O)] The crown ether complex of the aquapentachloroplatinic acid of the composition [H₁₃O₆][PtCl₅(H₄O₂)] · 2(18-cr-6) ( 2 ) reacts with K₂CO₃ and [NⁿBu₄]OH in aqueous solution to give [K(18-cr-6)][PtCl₅(H₂O)] ( 5 a ) and [NⁿBu₄][PtCl₅(H₂O)] · ¹/₂ (18-cr-6) · H₂O ( 5 b ), respectively. Both compounds were characterized by microanalysis, vibrational (IR, Raman) and NMR (¹H, ¹³C, ¹⁹⁵Pt) spectroscopy. The X-ray structure analysis of 5 a (orthorhombic, pnma; a = 16,550(4), b = 18,044(3), c = 7,415(1) Å; Z = 4; R1 = 0,0183; wR2 = 0,0414) reveals that the crystal is threaded by chains built up of [PtCl₅(H₂O)]^? and [K(18-cr-6)]⁺ units. There are tight K …? Cl contacts (d(K? Cl1)) = 3,0881(9) Å and O_W? H? O_cr hydrogen bridges (d(O1 …? O2) = 2,806(3) Å) between these units. The coordination polyhedron [PtCl₅O] has approximately C_4v symmetry.     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Zur Struktur und Konstitution von Dichloro(tetraalkylcyclobutadien)platin(II)-Komplexen

Structure and Constitution of Dichloro(tetraalkylcyclobutadiene)platinum(II) Complexes Hexachloroplatinic acid reacts in n-butanol with alkylsubstituted acetylenes RC≡CR (R = Me, Et) to give [PtCl₂(C₄R₄)] (R = Me ( 1 ), R = Et ( 2 )). The X-ray structure analysis of 1 (C2/m; a = 1 370.3(2), b = 1 128.3(1), c = 691.21(7) pm, β = 96.10(1)α; Z = 4) shows that 1 is monomeric and not dimeric as was described in the literature. Furthermore, 1 and 2 were extensively studied by i.r., Raman, and n.m.r. spectroscopical investigations.     

Synthese und Charakterisierung von Trimethyl(sulfato)platin(IV)Komplexen

Syntheses and Characterization of Trimethyl(sufato)platinum(IV) Complexes [(PtMe₃I)₄] ( 1 ) reacts in benzene/acetone (1 : 1) with excess of freshly precipitated silver sulfate (Pt : Ag = 1 : 2) to give [{[PtMe₃(H₂O)]₂SO₄}_∞] ( 2 ) at working up from acetone (not dried) and water to [{PtMe₃(H₂O)₂}₂SO₄] ( 3 ), respectively. [(PtMe₃I)₄] ( 1 ) reacts with AgBF₄ in the corresponding solvent L to give complexes of the type [PtMe₃L₃]BF₄ (L = Me₂CO 4 , MeOH 5 , MeCN 6 , THF 7 ). The triaqua complex 8 (L = H₂O) has been obtained by reaction of 4 with water. All complexes are characterized by microanalysis and NMR spectroscopy (¹H, ¹³C, ¹⁹⁵Pt). X-ray diffraction analysis of 2 (monoclinic, P2₁) exhibits dinuclear units [Me₃Pt(μ-H₂O)PtMe₃(H₂O)]²⁺ at which oxo ligands of sulfate ions are coordinated in such a way that the crystal is threaded by double chains. The Pt–O bonds to μ-aqua ligand are considerably longer than that to terminal aqua ligand (2.322(9)/2.363(8) vs. 2.234(9) Å). The structural characterization of 3 (triclinic, P 1) reveals [PtMe₃(H₂O)₂]⁺ cations that are bridged by a sulfate ion yielding a dinuclear entity [(H₂O)₂Me₃Pt(μ-SO₄)PtMe₃ · (H₂O)₂]. These entities are linked in the crystal by a network of hydrogen bridges.     

Palladium(II)‐ und Platin(II)‐Komplexe mit dem Antimalariamittel Mefloquin als Liganden

Metal Complexes of Biologically Important Ligands. CXXVI. Palladium(II) and Platinum(II) Complexes with the Antimalarial Drug Mefloquine as Ligand The coordination sites of the antimalarial drug mefloquine (L) were studied. Reactions of the chloro bridged complexes (allyl)Pd(μ‐Cl)₂Pd(allyl) and (R₃P)(Cl)M(μ‐Cl)₂M(Cl)(PR₃) (M = Pd, Pt) with racemic mefloquine give the compounds (allyl)(Cl)Pd(L) ( 1 ), Cl₂(Et₃P)Pt(L) ( 2 ) and Cl₂(Et₃P)Pd(L) ( 3 ) with coordination of the piperidine N atom of mefloquine. In the presence of NaOMe the N,O‐chelate complexes Cl(Et₃P)Pt(L–H⁺) ( 4 ) and Cl(R₃P)Pd(L–H⁺) ( 5 , 6 , R = Et, nBu) were obtained. Protection of the piperidine N atom of mefloquine by protonation allows the synthesis of the complexes Cl₂(Et₃P)Pt(L + H⁺) ( 7 ) in which mefloquine is coordinated via the quinoline N atom. The structures of 2 , 3 and 4 were determined by X‐ray diffraction analysis. In the crystal of 4 pairs of enantiomers are found which are linked by two hydrogen bridges between the amine group and the chloro ligand.     

N,N-Dimethylglycinatokomplexe von Platin(IV)

N,N -Dimethylglycinato Complexes of Platinum(IV) The aquapentachloroplatinic acid (H₃O)-[PtCl₅(H₂O)] · 2(18-cr-6) · 6 H₂O ( 1 ) reacts with N,N-dimethylglycine (Me₂glyH) to give cis-[PtCl₂(N,O-Me₂gly)₂] · (18-cr-6) ( 6 ) and (Me₂glyH₂)[PtCl₄(N,O-Me₂gly)] ( 7 ). Complexes 6 and 7 are characterized by microanalysis, ¹H-NMR and IR spectroscopy as well as by X-ray structure analysis. In both complexes the N,N-dimethylglycinato ligands are N,O-coordinated. In 6 , the amino groups are mutually trans and the carboxylato groups are cis (configuration index: OC-6–22). In the crystal, there are only weak C–H…O interactions between the N-methyl groups of the [PtCl₂(N,O-Me₂gly)₂] complex and the oxygen atoms of the crown ether (shortest C…O contacts: 3.10(2) Å and 3.21(2) Å). In the solid state, 7 exhibits strong cation-anion interactions: The carboxyl group of the cation (Me₂glyH₂)⁺ forms a strong O–H…O bridge to the exocyclic oxygen atom of the carboxylate group of the glycinato ligand (O…O 2.61(1) Å).     

Trichloro(Dinitrogen)Platinate(II)

Zeise's salt, [PtCl₃(H₂C=CH₂)]⁻_, is the oldest known organometallic complex, featuring ethylene strongly bound to a platinum salt. Many derivatives are known, but none involving dinitrogen, and indeed dinitrogen complexes are unknown for both platinum and palladium. Electrospray ionization mass spectrometry of K₂[PtCl₄] solutions generate strong ions corresponding to [PtCl₃(N₂)]⁻, the identity of which was confirmed through ion-mobility spectrometry and MS/MS experiments that proved it to be distinct from its isobaric counterparts [PtCl₃(C₂H₄)]⁻ and [PtCl₃(CO)]⁻. Computational analysis established a gas-phase platinum–dinitrogen bond strength of 116 kJ mol⁻¹, substantially weaker than the ethylene and carbon monoxide analogues but stronger than for polar solvents such as water, methanol and dimethylformamide, and strong enough that the calculated N−N bond length of 1.119 Å represents weakening to a degree typical of isolated dinitrogen complexes.     

Direct Evidence for a [4+2] Cycloaddition Mechanism of Alkynes to Tantallacyclopentadiene on Dinuclear Tantalum Complexes as a Model of Alkyne Cyclotrimerization

A dinuclear tantalum complex, [Ta₂Cl₆(μ‐C₄Et₄)] ( 2 ), bearing a tantallacyclopentadiene moiety, was synthesized by treating [(η²‐EtC?CEt)TaCl₃(DME)] ( 1 ) with AlCl₃. Complex 2 and its Lewis base adducts, [Ta₂Cl₆(μ‐C₄Et₄)L] (L=THF ( 3 a ), pyridine ( 3 b ), THT ( 3 c )), served as more active catalysts for cyclotrimerization of internal alkynes than 1 . During the reaction of 3 a with 3‐hexyne, we isolated [Ta₂Cl₄(μ‐η⁴:η⁴‐C₆Et₆)(μ‐η²:η²‐EtC?CEt)] ( 4 ), sandwiched by a two‐electron reduced μ‐η⁴:η⁴‐hexaethylbenzene and a μ‐η²:η²‐3‐hexyne ligand, as a product of an intermolecular cyclization between the metallacyclopentadiene moiety and 3‐hexyne. The formation of arene complexes [Ta₂Cl₄(μ‐η⁴:η⁴‐C₆Et₄Me₂)(μ‐η²:η²‐Me₃SiC?CSiMe₃)] ( 7 b ) and [Ta₂Cl₄(μ‐η⁴:η⁴‐C₆Et₄RH)(μ‐η²:η²‐Me₃SiC?CSiMe₃)] (R=nBu ( 8 a ), p‐tolyl ( 8 b )) by treating [Ta₂Cl₄(μ‐C₄Et₄)(μ‐η²:η²‐Me₃SiC?CSiMe₃)] ( 6 ) with 2‐butyne, 1‐hexyne, and p‐tolylacetylene without any isomers, at room temperature or low temperature were key for clarifying the [4+2] cycloaddition mechanism because of the restricted rotation behavior of the two‐electron reduced arene ligands without dissociation from the dinuclear tantalum center.     

Gemischtligand-Komplexe des Rheniums. IV. Die Reaktion von [ReNCl2(Me2PhP)3] mit Dithiocarbamaten. Kristallstrukturen von trans-Chloro-dimethyldithiocarbamato-bis(dimethylphenylphosphan) nitridorhenium(V), [ReN(Cl)(Me2PhP)2(Me2dtc)], und Bis(diethyldithiocarbamato)(dimethylphenylphosphan)nitridorhenium(V), [ReN(Me2PhP)(Et2dtc)2]

Mixed-Ligand Complexes of Rhenium IV. The Reaction of [ReNCl₂(Me₂PhP)₃] with Dithiocarbamates. X-Ray Crystal Structures of trans-Chloro-dimethyldithiocarbamato-bis(dimethylphenylphosphine) nitridorhenium(V), [ReN(Cl)(Me₂PhP)₂(Me₂dtc)], and Bis(diethyldithiocarbamato)(dimethylphenylphosphine)nitridorhenium(V), [ReN(Cl)(Me₂PhP)(Et₂dtc)₂] [ReNCl₂(Me₂PhP)₃] reacts with dialkyldithiocarbamates, R₂dtc^?, under a stepwise ligand exchange. Final products of these reactions are the well-known [ReN(R₂dtc)₂] bischelates. Intermediatelly, however, complexes of the general formulae [ReN(Cl)(Me₂PhP)₂(R₂dtc)] and [ReN(Me₂PhP)(R₂dtc)₂] can be isolated. Representatives have been structurally characterized. [ReN(Cl)(Me₂PhP)₂(Me₂dtc)] crystallizes monoclinic in the space group P2₁/c, Z = 4. The dimensions of the unit cell are a = 13.071(3); b = 11.622(1); c = 15.667(3) Å; β = 97.09(1)°. The rhenium atom has a distorted octahedral environment; the Re≡N bond length is 1.71(1) Å. The Re? Cl bond distance is markedly lengthened (2.665(2) Å) as a consequence of the strong trans labilizing influence of the coordinated nitrido ligand. [ReN(Me₂PhP)(Et₂dtc)₂] crystallizes monoclinic in the space group P2₁/c, Z = 4, a = 17.262(3); b = 14.915(2); c = 9.888(2); β = 76.35(8)°. The equatorial coordination sphere is occupied by one phosphorus atom and three sulphur atoms. One of the dithiocarbamate ligands is coordinated bidentately; the second one with two distinct Re? S bond lengths. The Re? S(4) distance is 2.7983(2) Å which can be discussed as a weak interaction with the metal.     

Methylene-bridged bis(8-arylimino)-5,6,7-trihydro-quinolylinickel precatalysts for ethylene polymerization

A series of binuclear nickel complexes bearing N-(5,6,7-trihydroquinolin-8-ylidene)amino CH(C₆H₄-4-R²){4-C₆H₂-2,6-R¹₂N-(C₅H₃NC₄H₆)}₂ [R¹ = Me, R² = OH L1 , R¹ = Et, R² = OH L2 , R¹ = Me, R² = H L3 , R¹ = Me, R² = OCH₃ L4 ] has been synthesized and characterized. In the presence of either methylaluminoxane (MAO) or Et₂AlCl, all nickel complexes exhibited high activities up to 3.33 × 10⁶ g (PE)·mol⁻¹(Ni)·hr⁻¹ toward ethylene polymerization, producing high branched polyethylenes (PEs). The aluminum cocatalysts have significantly affected the properties of resultant PE; with MAO as the cocatalyst, the resultant PE shows higher molecular weight and possesses only one T_m value, meanwhile Et₂AlCl as the cocatalyst, the obtained PE indicates lower molecular weight and two melting points. The microstructures of those PEs determined by their ¹³C NMR spectra illustrate the similar densities but different types of branches, in which the PE obtained with Et₂AlCl shows high methyl branch selectivity (>80%), and the PE produced by MAO has 50% methyl and another half of longer branches. The branched PEs are consistent to the chain migration happened in the ethylene polymerization.     

Synthese,Struktur und Photochemie von Olefiniridium(I)‐Komplexen mit Acetylacetonatoliganden

Synthesis, Structure, and Photochemical Behavior of Olefine Iridium(I) Complexes with Acetylacetonato Ligands The bis(ethene) complex [Ir(κ²‐acac)(C₂H₄)₂] ( 1 ) reacts with tertiary phosphanes to give the monosubstitution products [Ir(κ²‐acac)(C₂H₄)(PR₃)] ( 2 – 5 ). While 2 (R = iPr) is inert toward PiPr₃, the reaction of 2 with diphenylacetylene affords the π‐alkyne complex [Ir(κ²‐acac)(C₂Ph₂)(PiPr₃)] ( 6 ). Treatment of [IrCl(C₂H₄)₄] with C‐functionalized acetylacetonates yields the compounds [Ir(κ²‐acacR^1,2)(C₂H₄)₂] ( 8 , 9 ), which react with PiPr₃ to give [Ir(κ²‐acacR^1,2)(C₂H₄)(PiPr₃)] ( 10 , 11 ) by displacement of one ethene ligand. UV irradiation of 5 (PR₃ = iPr₂PCH₂CO₂Me) and 11 (R² = (CH₂)₃CO₂Me) leads, after addition of PiPr₃, to the formation of the hydrido(vinyl)iridium(III) complexes 7 and 12 . The reaction of 2 with the ethene derivatives CH₂=CHR (R = CN, OC(O)Me, C(O)Me) affords the compounds [Ir(κ²‐acac)(CH₂=CHR)(PiPr₃)] ( 13 – 15 ), which on photolysis in the presence of PiPr₃ also undergo an intramolecular C–H activation. In contrast, the analogous complexes [Ir(κ²‐acac)(olefin)(PiPr₃)] (olefin = (E)‐C₂H₂(CO₂Me)₂ 16 , (Z)‐C₂H₂(CO₂Me)₂ 17 ) are photochemically inert.     

Reactions of Distibanes with [Fe2(CO)9]: Synthesis,Structure and DFT Calculations of [(Et2Sb)4Fe4(CO)14], [(nPr2Sb)4Fe3(CO)10], [{(Me3SiCH2)2Sb}4Fe2(CO)6], and [2‐(Me2NCH2)C6H4SbFe2(CO)8]

The iron complexes [(Et₂Sb)₄Fe₄(CO)₁₄] ( 1 ), [(nPr₂Sb)₄Fe₃(CO)₁₀] ( 2 ), [{(Me₃SiCH₂)₂Sb}₄Fe₂(CO)₆] ( 3 ), and [2‐(Me₂NCH₂)C₆H₄SbFe₂(CO)₈] ( 4 ) were prepared by reactions of distibanes with Fe₂(CO)₉. Compounds 1 – 4 were characterized by X‐ray diffraction, ¹H NMR and IR spectroscopy as well as mass spectrometry; complex 1 was additionally characterized by density functional calculations.     

Comparative Study of Phosphine and N‐Heterocyclic Carbene Stabilized Group 13 Adducts [L(EH3)] and [L2(E2Hn)]

Quantum chemical calculations using density functional theory at the BP86/TZ2P level have been carried out to determine the geometries and stabilities of Group 13 adducts [(PMe₃)(EH₃)] and [(PMe₃)₂(E₂H_n)] (E=B–In; n=4, 2, 0). The optimized geometries exhibit, in most cases, similar features to those of related adducts [(NHC^Me)(EH₃)] and [(NHC^Me)₂(E₂H_n)] with a few exceptions that can be explained by the different donor strengths of the ligands. The calculations show that the carbene ligand L=NHC^Me (:C(NMeCH)₂) is a significantly stronger donor than L=PMe₃. The equilibrium geometries of [L(EH₃)] possess, in all cases, a pyramidal structure, whereas the complexes [L₂(E₂H₄)] always have an antiperiplanar arrangement of the ligands L. The phosphine ligands in [(PMe₃)₂(B₂H₂)], which has C_s symmetry, are in the same plane as the B₂H₂ moiety, whereas the heavier homologues [(PMe₃)₂(E₂H₂)] (E=Al, Ga, In) have C_i symmetry in which the ligands bind side‐on to the E₂H₂ acceptor. This is in contrast to the [(NHC^Me)₂(E₂H₂)] adducts for which the NHC^Me donor always binds in the same plane as E₂H₂ except for the indium complex [(NHC^Me)₂(In₂H₂)], which exhibits side‐on bonding. The boron complexes [L₂(B₂)] (L=PMe₃ and NHC^Me) possess a linear arrangement of the LBBL moiety, which has a B?B triple bond. The heavier homologues [L₂(E₂)] have antiperiplanar arrangements of the LEEL moieties, except for [(PMe₃)₂(In₂)], which has a twisted structure in which the PInInP torsion angle is 123.0°. The structural features of the complexes [L(EH₃)] and [L₂(E₂H_n)] can be explained in terms of donor–acceptor interactions between the donors L and the acceptors EH₃ and E₂H_n, which have been analyzed quantitatively by using the energy decomposition analysis (EDA) method. The calculations predict that the hydrogenation reaction of the dimeric magnesium(I) compound L′MgMgL′ with the complexes [L(EH₃)] is energetically more favorable for L=PMe₃ than for NHC^Me.     

LIGAND EXCHANGE AND LIGAND TRADING IN TRANS-[PtX2(OLEFIN) (PYRIDINE)] COMPLEXES

Abstract

The ¹H nmr spectra of freshly prepared CDCl₃ solutions of the complexes trans-[PtCl₂(olefin)(L)], where L is pyridine or a substituted pyridine, show no coupling between ^{1 9 5}Pt and the α protons of pyridine (³J_pt–NCH) owing to rapid exchange of complexed L with free L. On standing, the adventitious free L is gradually consumed by formation of trans-[PtCl₂(L)₂] and the spectra of the aged solutions show the coupling. When CDCl, solutions of [PtBr₂(Ol_b)(L_b)] and [PtCl₂(Ol_a)(L_a)], where Ol_a =C₂H₄, are mixed, a total of 6 ethylene complexes can be identified in solution. Accordingly halogen trading, Ol trading or/and L trading occurs and the solution probably contains a total of 12 complexes.     

Chemical Transformations of (2,3,9,10-Tetramethyl-1,4,5,7,8,11,12,14-Octa-Azacyclotetradeca-1,3,8,10-Tetraenato)Cobalt(II)Perchlorate

The monomeric octa-aza bis-α-diimine macrocyclic complex [Co^II(C₁₀H₂₀N₈)(H²O)](ClO₄)₂ I, undergoes various reactions on the macrocyclic ligand. Reaction of complex I with triethylamine in double molar proportions, followed by slow aerial oxidation, produces a molecular dimeric complex [Co^II(C₁₀H₁₄N₈)]₂, III, and a novel Co(I) complex [Co^I(C₁₀H₁₉N₈)], IV. Complex III is a staggered cofacial dimer with a cobalt-cobalt bond length 2.86(1) Å. The macrocyclic ligand of the complex contains an a-diimine function in each five-membered chelate ring, and a three-atom N-C-N^? delocalized system in each six-membered chelate ring. Complex IV has the 5-5-6-6 chelate arrangement because one α-diimine moiety is rearranged to a syn-anti configuration. In the structure, the two fused six-membered chelate rings are fully conjugated and the two fused five-membered rings are saturated. However, when complex I reacts with excess triethylamine under the similar conditions, a dimeric complex of another type, [Co^II(C₁₀H_l6N₈)]₂, II, was generated, in which one N-N bond of the macrocyclic ligand is broken. Complex IV can be isolated also from the reaction of complex I with excess hydrazine, followed by slow aerial oxidation. When hydrazine in double molar proportions was used, complex [Co^I(C₁₀H₁₇N₈)(NHNH)] V, which contains a coordinated diazene ligand, was obtained. Only one six-membered chelate ring of complex V is deprotonated and oxidized to form a three-atom N-C-N^? delocalized system. The structures of octa-aza complexes I-V are determined by X-ray crystallography: I, orthorhombic, C mca, a = 11.646(4), b = 17.049(3), c = 10.706(3) Å, Z = 4, R = 0.045, R_w = 0.047, based on 1024 reflections with I > 2σ(I); II, monoclinic, P 2₁/c, a = 9.814(3), b = 22.583(6). c = 14.632(9) Å, β = 98.90(5)°, Z = 4, R = 0.085, R_w = 0.101, based on 2033 reflections with I > 2σ(I); III, tetragonal, P 4/nmm, a = 15.614(3), c = 6.498(2) Å, Z = 4, R = 0.081, R_w = 0.115, based on 340 reflections with I > 2σ(I); IV, orthorhombic, P bca, a = 8.484(1), b = 16.662(3), c = 18.760(2) Å, Z = 8, R = 0.029, R_w = 0.024, based on 1441 reflections with I > 2σ(I); V, monoclinic, P 2₁/m, a = 7.892(3), b = 11.713(6), c = 9.326(4) Å, β = 108.03(3), Z = 2, R = 0.047, R_w = 0.056, based on 948 reflections with I > 2σ(I).     

The Influence of Substituents at C2 Carbon Atom of Thiosemicarbazones {R(H)C2=N3‐N2(H)‐C1(=S)‐N1H2} on their Dentacy in PtII/PdII Complexes: Synthesis,Spectroscopy, and Crystal Structures

The coordination chemistry of platinum(II) with a series of thiosemicarbazones {R(H)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂, R = 2‐hydroxyphenyl, H₂stsc; pyrrole, H₂ptsc; phenyl, Hbtsc} is described. Reactions of trans‐PtCl₂(PPh₃)₂ precursor with H₂stsc (or H₂ptsc) in 1 : 1 molar ratio in the presence of Et₃N base yielded complexes, [Pt(η³‐ O, N³, S‐stsc)(PPh₃)] ( 1 ) and [Pt(η³‐ N⁴, N³, S‐ptsc)(PPh₃)] ( 2 ), respectively. Further, trans‐PtCl₂(PPh₃)₂ and Hbtsc in 1 : 2 (M : L) molar ratio yielded a different compound, [Pt(η²‐ N³, S‐btsc)(η¹‐S‐btsc)(PPh₃)] ( 3 ). Complex 1 involved deprotonation of hydrazinic (‐N²H‐) and hydroxyl (‐OH) groups, and stsc^2? is coordinating via O, N³, S donor atoms, while complex 2 involved deprotonation of hydrazinic (‐N²H‐) and ‐N⁴H groups and ptsc^2? is probably coordinating via N⁴, N³, S donor atoms. Reaction of PdCl₂(PPh₃)₂ with Hbtsc‐Me {C₆H₅(CH₃)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂} yielded a cyclometallated complex [Pd(η³‐C, N³, S‐btsc‐Me)(PPh₃)] ( 4 ). These complexes have been characterized with the help of analytical data, spectroscopic techniques {IR, NMR (¹H, ³¹P), U.V} and single crystal X‐ray crystallography ( 1 , 3 and 4 ). The effects of substituents at C² carbon of thiosemicarbazones on their dentacy and cyclometallation are emphasized.     

Seven-coordinate complexes of molybdenum(II) and tungsten(II) containing pyrazole as a ligand

Summary Equimolar quantities of [MI₂(CO)₃(NCMe)₂] (M = Mo or W) and C₃H₄N² (pyrazole) react in CH₂C1₂ at room temperature to give the iodo-bridged dimers [M(μ-I) (CO)₃(C₃H₄N²)]₂ (1) and (2). Two equivalents of C₃H₄N² react with [MI₂(CO)₃(NCMe)₂] (M = Mo or W) to give the bis(pyrazole) complexes [MI₂(CO)₃(C₃H₄N²)₂] (3) and (4) in good yield. Three and four equivalents of pyrazole react with [MoI₂(CO)₃(NCMe)₂] to give the cationic complexes [MoI(CO)₃(C₃H₄N²)₃]I (5) and [MoI(CO)₂(C₃H₄N²)₄]I (6), respectively. The mixed ligand complexes [MI₂(CO)₃(C₃H₄N²)L] (M = Mo or W; L = PPh₃, AsPh₃ or SbPh₃) (7)-(12) are prepared by reacting equimolar amounts of [MI₂(CO)₃(NCMe)₂] and L in CH₂C1₂ at room temperature, followed by an in situ reaction with one equivalent of C₃H₄N². The MoSnCl₃ complex [MoCl(SnCl₃)(CO)₃(C₃H₄N²)₂] (13) is prepared in an analogous manner using acetone as the solvent, whilst the mixed ligand compound [MoCl(SnQ₃)(CO) ₃(C₃H₄N²)(PPh₃)] (14) was prepared by treating the dimeric complex [Mo(μ-Cl)(SnCl₃)(CO)₃(PPh₃)]₂ with two equivalents of C₃H₄N². All the new complexes were characterised by elemental analysis (carbon, hydrogen and nitrogen), i.r. and ¹H n.m.r. spectroscopy.     

Zur Reaktivität von Titanocenkomplexen [Ti(Cp′)2(η2‐Me3SiC≡CSiMe3)] (Cp′ = Cp,Cp*) gegenüber Benzoldicarbonsäuren

On the Reactivity of Titanocene Complexes [Ti(Cp′)₂(η²‐Me₃SiC≡CSiMe₃)] (Cp′ = Cp, Cp*) towards Benzenedicarboxylic Acids Titanocene complexes [Ti(Cp′)₂(BTMSA)] ( 1a , Cp′ = Cp = η⁵‐C₅H₅; 1b , Cp′ = Cp* = η⁵‐C₅Me₅; BTMSA = Me₃SiC≡CSiMe₃) were found to react with iodine and methyl iodide yielding [Ti(Cp′)₂(μ‐I)₂] ( 2a / b ; a refers to Cp′ = Cp and b to Cp′ = Cp*), [Ti(Cp′)₂I₂] ( 3a / b ) and [Ti(Cp′)₂(Me)I] ( 4a / b ), respectively. In contrast to 2a , complex 2b proved to be highly moisture sensitive yielding with cleavage of HCp* [{Ti(Cp*)I}₂(μ‐O)] ( 7 ). The corresponding reactions of 1a / b with p‐cresol and thiophenol resulted in the formation of [Ti(Cp′)₂{O(p‐Tol)}₂] ( 5a / b ) and [Ti(Cp′)₂(SPh)₂] ( 6a / b ), respectively. Reactions of 1a and 1b with 1,n‐benzenedicarboxylic acids (n = 2–4) resulted in the formation of dinuclear titanium(III) complexes of the type [{Ti(Cp′)₂}₂{μ‐1,n‐(O₂C)₂C₆H₄}] (n = 2, 8a / b ; n = 3, 9a / b ; n = 4, 10a / b ). All complexes were fully characterized analytically and spectroscopically. Furthermore, complexes 7 , 8b , 9a ·THF, 10a / b were also be characterized by single‐crystal X‐ray diffraction analyses.