Reactions of transition metal σ-acetylide complexes: IX. Preparation and properties of some cycloheptatrienylvinylidene complexes

Addition of [C₇H₇][PF₆] to iron, ruthenium or osmium alkynyl complexes has given eight cationic cycloheptatrienylvinylidene derivatives [M{C C(C₇H₇)R}(L)₂ (η-C₅H₅)][PF₆] (M = Fe, Ru or Os; R = Me, Pr, Ph or C₆F₅; L = PPh₃, L₂ = dppm or dppe; but not all combinations). With Fe(C₂Ph)(CO)₂(η-C₅H₅), only [Fe(CO)₂(thf)(η-C₅H₅)][PF₆] was obtained. Reactions of the new complexes are characterised by loss of the C₇H₇ group. The NMR spectra and FAB mass spectra are described in detail.     

Reactions of nucleophilic addition of primary amines to the nitrilium derivative of the <Emphasis Type="Italic">closo</Emphasis>-decaborate anion [2-B<Subscript>10</Subscript>H<Subscript>9</Subscript>(N≡CCH<Subscript>3</Subscript>)]<Superscript>−</Superscript>

Compounds (Bu₄N)[2-B₁₀H₉{NH=C(NHR)CH₃}]⁻ are obtained by reactions of the tetrabutylammonium salt of the [2-B₁₀H₉(N≡CCH₃)]⁻ anion with aliphatic and aromatic primary amines RNH₂ (R = n-C₃H₇, n-C₄H₉, cyclo-C₅H₉, C₆H₅, cyclo-C₆H₁₁, n-C₆H₁₃, C₇H₇, C₈H₈NH₂, C₆H₄NO₂, and C₁₈H₃₇) and identified by IR, ESI/MS, and NMR (¹H, ¹¹B, and ¹³C) spectroscopy. The structures of the amidine-type derivatives [2-B₁₀H₉{Z-NH=C(NH-cyclo-C₅H₉)CH₃}]⁻ and [2-B₁₀H₉{Z-NH=C(NH-C₇H₇)CH₃}]⁻ are determined by X-ray diffraction.     

Synthesis, Structure and Electrochemical Properties of Triarylamine Bridged Dicobaltdicarbon Tetrahedrane Clusters

The reaction of [Co₂(CO)₆(dppm)] (1) with the ethynyl substituted triarylamines [N(C₆H₄-4-C??CSiMe₃)(C₆H₄Me-4)₂] (2) or [N(C₆H₄-4-C??CSiMe₃)₂(C₆H₄Me-4)] (3) affords [{Co₂(CO)₄(dppm)}{??-(Me₃SiC₂-4-C₆H₄)N(C₆H₄Me-4)₂}] (4) or a mixture of [Co₂{??-Me₃SiC₂-4-C₆H₄N(C₆H₄-4-C??CSiMe₃)(C₆H₄Me-4)}(CO)₄(dppm)] (5) and [{Co₂(CO)₄(dppm)}₂{??-(Me₃SiC₂-4-C₆H₄)₂N(C₆H₄Me-4)}] (6), respectively. A combination of electrochemical measurements in different electrolytes, and IR and NIR spectroscopic studies of these compounds, which feature both organometallic and organic redox active groups, indicates that the cluster centres are oxidised at significantly less positive potentials than the triarylamine moieties. Reaction of 6 with one or two equivalents of [Fe(??-C₅H₄COMe)Cp]PF₆ gives [6][PF₆] _n (n?=?1, 2), which are best described in terms of cluster-localised oxidation processes. Despite the presence of the substantial differences in the first and second cluster based oxidations in 6 (up to 220?mV in CH₂Cl₂/0.1?M [NBu₄][BAr ₄ ^F ]), there is little ground state delocalisation between the cluster centres through the triarylamine bridge. The stabilisation of [6]⁺ with respect to disproportionation can be attributed to electrostatic effects.     

Use of the Cationic Fragments [Ru(η5-C5H5) (MeCN)3]+ and [M(η6-C6H5R)(MeCN)3]+ (M=Os, Ru; R=H, Me) as Ionic Coupling Reagents in the Synthesis of the Clusters [Os4M2(CO)12(η6-C6H5R)], [Os4M(CO)12(η6-C6H6)(Au2dppm)] and [Os5Ru(CO)15(η5-C5H5)(AuPPh3)]*

The clusters [H₂Os₄M(CO)₁₂eta⁶-C₆H₆)] (M=Os, Ru) may be deprotonated to generate anions [Os₄M(CO)₁₂eta⁶-C₆H₆)]^2- which react with [M′eta⁶-C₆H₅R) (MeCN)₃]²⁺(M^′=Os, Ru; R=H, Me) to give the bicapped tetrahedral clusters [Os₄(CO)₁₂MM′eta⁶-C₆H₅R)₂]. Whereas [Os₄(CO)₁₂M₂eta⁶-C₆H₆)₂] (M=Os, Ru) have one Meta⁶-C₆H₆) unit in a site connected to three other metals, {3}, and one in a site connected to four other metals, {4}, [Os₄(CO)₁₂OsRueta⁶-C₆H₆)₂] has the Rueta⁶-C₆H₆) unit in the {3} site irrespective of whether the Os or Ru anion is capped. Coupling of these anions with Au₂dppm yields [Os₄M(CO)₁₂eta⁶-C₆H₆)(Au₂dppm)] (M=Os, Ru), which have the arene ligand in the axial site of a trigonal bipyramid and the digold unit capping two faces. Reduction of [H₂Os₅(CO)₁₅] with K/Ph₂CO and coupling with [Rueta⁵-C₅H₅)(MeCN)₃]²⁺yields the monoanion [Os₅(CO)₁₅Rueta⁵-C₅H₅)]^? which reacts with [AuPPh₃]⁺ generating [Os₅(CO)₁₅Rueta⁵-C₅H₅)(AuPPh₃)] with the “Ru(C₅H₅)” unit in the terminal {3} site.     

Ring Expansions of Nonpolar Polyphosphorus Rings

The reaction of the phosphinidene complex [Cp*P{W(CO)₅}₂] ( 1 a ) (Cp*=C₅Me₅) with the anionic cyclo-P_n ligand complex [(η³-P₃)Nb(ODipp)₃]⁻ ( 2 , Dipp=2,6-diisopropylphenyl) resulted in the formation of [{W(CO)₅}₂{μ₃,η^3:1:1-P₄Cp*}Nb(ODipp)₃]⁻ ( 3 ), which represents an unprecedented example of a ring expansion of a polyphosphorus-ligand complex initiated by a phosphinidene complex. Furthermore, the reaction of the pnictinidene complexes [Cp*E{W(CO)₅}₂] (E=P: 1 a , As: 1 b ) with the neutral complex [Cp′′′Co(η⁴-P₄)] (Cp′′′=1,2,4-tBu₃C₅H₂) led to a cyclo-P₄E ring (E=P, As) through the insertion of the pentel atom into the cyclo-P₄ ligand. Starting from 1 a , the two isomers [Cp′′′Co(μ₃,η^4:1:1-P₅Cp*){W(CO)₅}₂] ( 5 a , b ), and from 1 b , the three isomers [Cp′′′Co(μ₃,η^4:1:1-AsP₄Cp*){W(CO)₅}₂] ( 6 a – c ) with unprecedented cyclo-P₄E ligands (E=P, As) were isolated. The complexes 6 a – c represent unique examples of ring expansions which lead to new mixed five-membered cyclo-P₄As ligands. The possible reaction pathways for the formation of 5 a , b and 6 a – c were investigated by a combination of temperature-dependent ³¹P{¹H} NMR studies and DFT calculations.     

Reactions of Ethyne with Some Ruthenium Cluster Complexes Containing dppm

Reactions of ethyne with [Ru₃(μ‐dppm)(CO)₁₀] have given isomeric complexes [Ru₃(μ₃‐C₆H₆)(CO)₆(dppm)], one of which, 2 , contains the dppm chelating an Ru‐atom, together with a hexatrienetriyl ligand attached to the Ru₃ cluster to form a methylideneruthenacyclohexadiene system. The second isomer 3 contains the dppm bridging an Ru−Ru bond, with the C₆H₆ ligand forming a vinylruthenacyclopentadiene system. Also isolated was the open‐chain Ru₃ complex 4 containing a ruthenacyclopentadiene attached to the central Ru‐atom; the other Ru−Ru vector is bridged by a PPh₂CHPPh₂C₄H₅ ligand, formed by a novel insertion of two ethyne molecules into an Ru−P bond. The reaction of ethyne with [Ru₃(μ‐H)(μ₃‐C₂H₂)(CO)₉] proceeded by attack at the coordinated alkyne and at the cluster to give a cluster‐bonded PPh₂CH₂PPh₂CCH system in 7 . Thermolysis of [Ru₃(μ‐H)(μ₃‐C₂SiMe₃)(μ‐dppm)(CO)₇] ( 8 ; refluxing MeOH) in the presence of KF gave [Ru₆(μ‐CCH₂)₂(μ‐dppm)₂(CO)₁₂] ( 9 ; 80%); similar reactions carried out with [RuClCp(PPh₃)₂] also present gave 9 (67%) together with [Ru₃(μ‐H)(μ₃‐C₂H)(μ‐dppm)(CO)₆(PPh₃)] ( 11 ; 23%). The molecular structures of 2 , 3 , 4 , 7 , 9 , and 11 , some as differently solvated forms, have been determined by single‐crystal X‐ray studies.     

Heterobimetallische phosphanido-verbrückte Zweikern-Komplexe - Synthese von cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6−iPr3C6H2)}2M(CO)4] (RMe,MCr,Mo; RH,MMo)

Heterobimetallic Phosphanido-bridged Dinuclear Complexes - Syntheses of cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] (R?Me, M?Cr, Mo; R?H, M?Mo) The zirconocene bisphosphanido complexes [(η-C₅H₄R)₂Zr{PH(2,4,6-ⁱPr₃C₆H₂)}₂] (R?Me, H) react with [(NBD)M(CO)₄] (NBD?norbornadiene, M?Cr, Mo) to give only one diastereomer of the phosphanido-bridged heterobimetallic dinuclear complexes cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] [R?Me, M?Cr ( 1 ), Mo ( 2 ); R?H, M?Mo ( 3 )]. However, no reaction was observed between [(η-C₅H₅)₂Zr{PH(2,4,6-^tBu₃ C₆H₂)}₂] and [Pt(PPh₃)₄]. 1—3 were characterised spectroscopically. For 1—3 , the presence of the racemic isomer was shown by NMR spectroscopy. No reaction was observed at room temperature for 3 and CS₂, (NO)BF₄, Me₃NO or PH(2,4,6-Me₃C₆H₂)₂. With Et₂AlH or PhC?CH decomposition of 3 was observed.     

Mass spectra of new heterocycles: X. Fragmentation of the molecular ions of 1-alkyl(cycloalkyl,aryl)-3-alkoxy(aryl)-2-methylsulfanyl-1<Emphasis Type="Italic">H</Emphasis>-pyrroles

The mass spectra of previously unknown 1-alkyl(cycloalkyl, aryl)-3-alkoxy(aryl)-2-methylsulfanyl-1H-pyrroles were studied. Fragmentation of all 3-alkoxy-substituted pyrroles under electron impact (70 eV) follow both ether and sulfide decomposition paths; In particular, 1-R-substituted 3-methoxy-2-methylsulfanyl-1H-pyrroles (R = Me, Et, i-Pr, s-Bu, cyclo-C₅H₉, cyclo-C₆H₁₁, Ph) lose methyl radical group from both methoxy and methylsulfanyl groups. The mass spectra of 1-sec-butyl- and 1-cycloalkylpyrroles also contained a strong peak (10–49%) from odd-electron [M — C _n H_2n ]^+· ion formed via cleavage of the N-R bond with synchronous hydrogen transfer. Cleavage of the O-Alk bond in the fragmentation of 3-alkoxy-1-isopropyl-2-methylsulfanyl-1H-pyrroles (Alk = Et, i-Pr, t-Bu) was accompanied by rearrangement process leading to the corresponding alkene and odd-electron 1-isopropyl-2-methylsulfanyl-1H-pyrrol-3-ol ion. The main fragmentation path of 1-alkyl-2-methylsulfanyl-3-phenyl-1H-pyrroles (Alk = Me, i-Pr) under electron impact involves dissociation of the S-Me bond with formation of rearrangement 1H-[1]benzothieno[2,3-b]pyrrol-8-ium ion.     

Studies of lambert's reaction: The formation of [Mn2(CO)8(μ-AsR2)2] complexes from tertiary arsines and [Mn2(CO)10] at high temperatures

Although very bulky ligands e.g.(o-MeC₆H₄)₃E or (μ-C₁₀H₇)₃E (E = P or As) are inert, the normal photochemical or thermal reaction of tertiary phosphines or arsines, L, with [Mn₂(CO)₁₀] is CO substitution with the formation of [Mn₂(CO)₈(L)₂] derivatives (I). At elevated temperatures some triarylarsines, R₃As, undergo Lambert's reaction with ligand fragmentation to give [Mn₂(CO)₈(μ-AsR₂)₂] complexes (II) (R = Ph, p-MeOC₆H₄, p-FC₆H₄, or p-CIC₆H₄) even though, in the absence of [Mn₂(CO)₁₀] R₃As are stable under the same conditions. Exceptional behaviour is exhibited by (p-Me₂NC₆H₄)_3- As which forms a product of type I; by some HN(C₆H₄)₂AsR which give a product of type II as a result of loss of the non-aryl groups R = PhCH₂, cyclo-C₆H₁₁, or MeO; and by Ph(α-C₁₀H₇₂P which is the only phosphine to form a product of type II, albeit in trace amounts only. The thermal decomposition of a n-butanol solution of [Mn₂(CO)₈(AsPh₃)₂] in a sealed tube gives C₆H₆ and [Mn₂(CO)₈(α-AsPh₂)₂], whilst in an open system in the presence of various tertiary phosphines, L, [Mn(H)(CO)₃(L)₂] are obtained. It is suggested that Lambert's reaction is a thermal fragmentation of [Mn(CO)₄(AsR₃]^* radicals, the first to be recognised. They lose the radical R^* which abstracts hydrogen from the solvent. The resulting [Mn(CO)₄(AsR₂)] moiety dimerises to [Mn₂(CO)_8-(α-AsR₂)₂]. the reaction is facilitated by the stability of the departing radical (e.g. PhCH₂ or MeO) and, as the crowding about As is relieved, by its size (e.g. Ph, cyclo-C₆H₁₁, o-MeC₆H₄, or α-C₁₀H₇). In general, phosphine-substituted radicals [Mn(CO)₄(PR)₃]^* do not undergo this decomposition, probably because the PC bonds are much stronger than AsC.     

Photochemistry of methyl- and n1-benzyl-n5-cyclopentadienyltricarbonyltungstein(II)

Irradiation of solutions of n⁵-C₅H₅W(CO)₃R (R  CH₃n1-CH₂C₆H₅) in cyclohexane at ca. 310490 nm leads to the formation of [n⁵-C₅H₅W(CO)₃]₂ and methane and of n⁵-C₅H₅W₅(CO)₂(n³-CH₂C₆H₅) and some [n⁵-C₅H₅W(CO)₃]₂, respectively. When the irradiation is carried out in the presence of excess P(C₆H₅)₃, the photoproducts are n⁵-C₅H₅W(CO)₂[P(C₆H₅)₃]CH₃ (R  CH₃) and n⁵-C₅H₅W(CO)₂(n₃-CH₂C₆H₅) and trace [n⁵-C₅H₅W(CO)₃]₂ (R  n¹-CH₂C₆H₅). Photolysis of the n⁵-C₅H₅W(CO)₃R in the presence of benzyl chloride affords n⁵-C₅H₅W(CO)₃Cl (R  CH₃) and both n⁵-C₅H₅W(CO)₂(n³-CH₂C₂H₅) and n⁵-C₅H₅W(CO)₃Cl (R  n¹-CH₂C₆H₅), the relative amounts of the latter products depending on the quantity of added C₆H₅CH₂Cl. Irradiation of n⁵-C₅H₅W(CO)₃-CH₃ in the presence of both P(C₆h₅)₃ and C₆H₅CH₂Cl affords n⁵-C₅H₅W(CO)₂-[P(C₆H₅)₃]CH₃, but no n⁵-C₅H₅W(CO)₃Cl. It is proposed that the primary photo-reaction in these transformations is dissociation of a CO group from n⁵-C₅H₅W-(CO)₃R to generate n⁵-C₅H₅W(CO)₂R, which can either combine with L to form a stable 18 electron complex, n⁵-C₅H₅W(CO)₂(L)R (L  CO, P(C₅H₅)₃; LR  n³-CH₂C₆H₅), or lose the group R in a competing, apparently slower step. This proposal receives support from the observation that, light intensifies being equal, n⁵-C₅H₅W(CO)₃CH₃ undergoes a considerably faster photoconversion to [n⁵-C₅H₅W(CO)₃]₂ under argon than under carbon monoxide.     

Photochemical substitution of benzene in the iron cyclohexadienyl complex [(η<Superscript>5</Superscript>-C<Subscript>6</Subscript>H<Subscript>7</Subscript>)Fe(η-C<Subscript>6</Subscript>H<Subscript>6</Subscript>)]<Superscript>+</Superscript>

The visible light irradiation of the [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ cation (1) in acetonitrile resulted in the substitution of the benzene ligand to form the labile acetonitrile species [(η⁵-C₆H₇)Fe(MeCN)₃]⁺ (2). The reaction of 1 with Bu^tNC in MeCN produced the stable isonitrile complex [(η⁵-C₆H₇)Fe(Bu^tNC)₃]⁺ (3). The photochemical reaction of cation 1 with pentaphosphaferrocene Cp*Fe(η-cyclo-P₅) afforded the triple-decker cation with the bridging pentaphospholyl ligand, [(η⁵-C₆H₇)Fe(μ-η:η-cyclo-P₅)FeCp*]⁺ (4). The latter complex was also synthesized by the reaction of cation 2 with Cp*Fe(η-cyclo-P₅). The structure of the complex [3]PF₆ was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 2007.     

Pyridazines. LXXXIV. Studies on borohydride reduction of pyridazine compounds

Imidazo[1,2-b]pyridazine, s-triazolo[4,3-b]pyridazine and tetrazolo[1,5-b]pyridazine and some derivatives thereof were reduced with sodium borohydride to give the corresponding 5,6,7,8-tetrahydro derivatives. A mechanism for these reductions is proposed and reduction at the C₇-C₈ bond occurs before the reduction of the C₆? N₅ bond. Substituents at position 7 and/or 8 cause a significant decrease in the extent of reduction or lead to a 5,6-dihydro derivative by competitive attack at the 6 position.     

Cobalt Carbonyls Stabilized by N,P-Ligands: Synthesis,Structure, and Catalytic Property for Ethylene Oxide Hydroalkoxycarbonylation

Reactions of N,P-Ligands as Ph₂P(o-NMe₂C₆H₄) (¹L), 2,6-iPr₂C₆H₃NHC(Ph)=NC₆H₄(o-PPh₂) (²L), and Ph₂PN(R)PPh₂ (R=iPr (³L), cyclo-C₆H₁₁ (⁴L), tBu (⁵L), CH₂C₄H₇O (⁶L)) each with dicobalt octacarbonyl produced complexes [¹LCo(CO)₃]₂ ( 1 ), [²LCo(CO)(μ-CO)₂Co(CO)₃] ( 2 ), [³LCo(CO)₃]⁺[Co(CO)₄]⁻ ( 3 ), [³LCo(CO)₂]₂ ( 4 ), [⁴LCo(CO)₂]₂ ( 5 ), [⁵LCo(CO)₂]⁺[Co(CO)₄]⁻ ( 6 ), and [⁶LCo(CO)₂]⁺[Co(CO)₄]⁻ ( 7 ). Complexes 1–7 have all been structurally characterized by X-ray crystallography, IR and NMR spectroscopies, and elemental analysis. Catalytic tests on transformation of ethylene oxide (EO), CO and MeOH into methyl 3-hydroxypropionate (3-HMP) indicate that complexes 1 – 7 are active, where ion-pair complexes 3 and 6 – 7 behave more excellently (by achieving 88.4–93.6% 3-HMP yields) than the neutral species 1 – 2 and 4 – 5 (35.0–46.5% 3-HMP yields) when the reactions are all operated at 2 MPa CO pressure and 50 °C in MeOH solvent. Density functional theory (DFT) study by selecting 3 as a model suggests a cooperative catalytic reaction mechanism by [Co(CO)₄]⁻ and its counter cation [³LCo(CO)₃]⁺. The cobalt-homonuclear ion-pair catalyzed hydroalkoxycarbonylation of EO is present herein.     

The coordinative properties of the ligands Ph2ECH2EPh2 (E = P,As, Sb) in carbonylvanadium complexes,and the molecular structure of η5-C5H5V(CO)3As2Ph4

Photo-reaction between the ligands Ph₂ECH₂EPh₂ (E = P: dppm, E = As: dpam, E = Sb: dpsm), L, and the vanadium complexes η⁵-C₅H₅V(CO)₄ and [Et₄N][V(CO)₆] yields monosubstituted mononuclear (dpsm) and dinuclear, ligand-bridged complexes (dpam, dpsm). With dppm, the final products are disubstituted chelate complexes, but monosubstituted mono- and dinuclear species are formed as intermediates.The shielding of the ⁵¹V nucleus decreases in the series dpsm > dppm > dpam and {M(CO)_n} > {M(CO)_n?1} L > {M(CO)_n?1}₂μ-L > {M(CO)_n?2}dppm ({M(CO)_n}[V(CO)₆]^?, η⁵-C₅H₅V(CO)₄). The half-widths of the NMR signals are greater for dinuclear than for mononuclear complexes.The crystal and molecular structures of η⁵-C₅H₅V(CO)₃As₂Ph₄ have been determined. The compound crystallizes in the space group P2₁/c with a = 1347.8, b = 1020.0, c = 2085.2 pm and β = 82.3°. Due to steric crowding, the ⁵¹V shielding is low composed to that of {η⁵-C₅H₅V(CO)₃}₂μ-dpam.     

Ethylcycloarsoxan, (C2H5AsO)n,ein Ionophor mit anpassungsfähiger Ringgröße in den Alkalimetallkomplexen [Na{cyclo-(C2H5AsO)4}2]SCN und [K{cyclo-(C2H5AsO)5}2]SCN

Ethylcycloarsoxane, (C₂H₅AsO)_n, an Ionophore with Adaptable Ring-Size in the Alkali Metal Complexes [Na{cyclo-(C₂H₅AsO)₄}₂]SCN and [K{cyclo-(C₂H₅AsO)₅}₂]SCN Ethylcycloarsoxane, (C₂H₅AsO)_n, is an ionophore for alkali metal cations with adaptable ring-size, [Na{cyclo-(C₂H₅AsO)₄}₂]SCN ( 1 ) and [K{cyclo-(C₂H₅AsO)₅}₂]SCN ( 2 ) have been prepared by the reaction of (C₂H₅AsO)_n with MSCN (M = Na, K) in acetonitrile and characterised by X-ray structural analysis. The sodium atom in 1 is coordinated in an approximately quadratic-antiprismatic fashion by 8 oxygen atoms and displays Na? O distances in the range 2.516(5) and 2.662(5) Å. A virtually undistorted pentagonal-antiprismatic coordination geometry with K? O distances between 2.90(1) and 3.06(1) Å is observed for the potassium atom in 2 . As a result of the smaller diameter of the arsoxane rings the antiprisms in 1 and 2 are significantly stretched along their main axis in comparison to analogous crown ether complexes.     

The Regioselective Methylation of Polycyclic Aromatic Hydrocarbons through Tricarbonylchromium Coordination

Deprotonation, methylation, and air oxidation of polycyclic arenes coordinated to chromium(0), (η⁶-arene)Cr(CO)₃, produced ring-methylated products with high selectivity and in good yield. This procedure gave 3-methylbenz[a]anthracene from (η⁶-benz[a]anthracene)Cr(CO)₃, 3-methylphenanthrene from (η⁶-phenanthrene)Cr(CO)₃, 2-acetyl-6-methylphenanthrene from (η^6?2-acetylphenanthrene)Cr(CO)₃, and 3,7,12-trimethylbenz[a]anthracene from (η^6?7,12-dimethylbenz[a]anthracene)Cr(CO)₃.     

Reaktionen eines Dibismutans und von Cyclobismutanen mit Metallcarbonylen ‐ Synthesen von Komplexen mit R2Bi‐, RBi‐, Bi2‐ und Bin‐Liganden (R = Me3CCH2, Me3SiCH2)

Reactions of a Dibismuthane and of Cyclobismuthanes with Metal Carbonyls ‐ Syntheses of Complexes with R₂Bi‐, RBi‐, Bi₂‐ and Bi_n‐ligands (R = Me₃CCH₂, Me₃SiCH₂) Reactions of [Fe₂(CO)₉] with [(Me₃CCH₂)₄Bi]₂ or cyclo‐(Me₃SiCH₂Bi)_n (n = 3 ‐ 5) lead to the complexes [(R₂Bi)₂Fe(CO)₄], [RBiFe(CO)₄]₂[R = Me₃CCH₂, Me₃SiCH₂] and [Bi₂Fe₃(CO)₉]. [Bi₂{Mn(CO)₂C₅H₄CH₃}₃] forms in a photochemical reaction of [Mn(CO)₃C₅H₄CH₃] with cyclo‐(Me₃SiCH₂Bi)_n.     

Reactions of metal carbonyl derivatives : XIV. Bridged phosphido derivatives of iron and ruthenium

The tertiary phosphines P(C₆H₅)₂R [RM π-C₅H₅)(CO)₂ M(π-C₅H₅(CO)₂ (M = Fe or Ru)] readily effect the displacement of the chloro group in [M′(φ-C₅H₅)(CO)₂Cl] (M′ = Fe or Ru) to give bridged cationic species of the type [MM′(φ-C₅H₅)₂(CO)₄P(C₆H₅)]⁺. Treatment of [Fe₂(CO)₉] with P(C₆H₅)₂R [RRu(φ-C₅H₅)(CO)₂] leads to the formation of the neutral mixed-metal derivatives [FeRu(φ-C₅H₅)(CO)₆P(C₆H₅)₂] and [FeRu(φ-C₅H₅)(CO)₅P(C₆H₅)₂].     

Synthesis and reactions of cycloheptadienyl and cyclooctadienyl tungsten complexes: X-ray crystal structure of [W(CO)2(PPh3)2(η-C7H9)][BF4]

Protonation of the cycloheptatriene complex [W(CO)₃(η⁶-C₇H₈)] with H[BF₄] · Et₂O in CH₂Cl₂ affords the cycloheptadienyl system [W(CO)₃(η⁵-C₇H₉)][BF₄] (1). Complex 1 reacts with NaI to yield [WI(CO)₃(η⁵-C₇H₉)], which is a precursor to [W(CO)₂(NCMe)₃(η³-C₇H₉)][BF₄], albeit in very low yield. The dicarbonyl derivatives [W(CO)₂L₂(η⁵-C₇H₉)]⁺ (L₂=2PPh₃, 4, or dppm, 5) were obtained, respectively, by H[BF₄] · Et₂O protonation of [W(CO)₂(PPh₃)(η⁶-C₇H₈)] in the presence of PPh₃ and reaction of 1 with dppm. The X-ray crystal structure of 4 (as a 1/2 CH₂Cl₂ solvate) reveals that the two PPh₃ ligands are mutually trans and are located beneath the central dienyl carbon and the centre of the edge bridge. The first examples of cyclooctadienyl tungsten complexes [WBr(CO)₂(NCMe)₂(1-3-η:5,6-C₈H₁₁)] (6) and [WBr(CO)₂(NCMe)₂(1-3-η:4,5-C₈H₁₁)] (7) were synthesised by reaction of [W(CO)₃(NCR)₃] (R=Me or Prⁿ) with 3-Br-1,5-cod/6-Br-1,4-cod or 5-Br-1,3-cod/3-Br-1,4-cod (cod=cyclooctadiene), respectively. Complexes 6 and 7 are precursors to the pentahapto-bonded cyclooctadienyl tungsten species [W(CO)₂(dppm)(1-3:5,6-η-C₈H₁₁)][BF₄] and [W(CO)₂(dppe)(1-5-η-C₈H₁₁)][BF₄] · CH₂Cl₂.     

Stable and Persistent Acyclic Diaminocarbenes with Cycloalkyl Substituents and Their Transformation to β-Lactams by Uncatalysed Carbonylation with CO

Four new acyclic diaminocarbenes (ADACs), viz. [(cyclo-C_nH_2n−1)₂N]₂C (n=5–7) and iPr₂N-C-N(cyclo-C₆H₁₁)₂, were synthesised by reacting the corresponding formamidinium hexafluorophosphates with NaN(SiMe₃)₂. Their nucleophilicities and electrophilicities were respectively judged from the ¹J_CH values determined for the N₂CH unit of the corresponding formamidinium cations and from the ⁷⁷Se NMR chemical shifts of the selenourea derivatives obtained from the reaction of elemental selenium with the corresponding ADACs. An ambiphilic profile essentially identical to that of the “Alder carbene” (iPr₂N)₂C was found in each case. Similar to the latter carbene, the new ADACs undergo a well-defined thermal decomposition by β-fragmentation, affording an alkene and a formamidine. The stabilities of [(cyclo-C_nH_2n−1)₂N]₂C depend strongly on the value of n, following the order 6>5>7, with the latter congener being too unstable for isolation. [(cyclo-C₆H₁₁)₂N]₂C shows no thermal decomposition at room temperature in solution and is thus significantly more stable than (iPr₂N)₂C. The stability of iPr₂N-C-N(cyclo-C₆H₁₁)₂ is intermediate between that of (iPr₂N)₂C and [(cyclo-C₆H₁₁)₂N]₂C, its β-fragmentation selectively affording propene and iPrN=CH-N(cyclo-C₆H₁₁)₂. [(cyclo-C_nH_2n−1)₂N]₂C (n=5–7) react readily with CO under mild conditions, selectively affording trisubstituted spirocyclic β-lactam derivatives with an antimicrobial activity spectrum similar to that of penicillin G.