Electrochemical and spectral study of intramolecular charge transfer in dinuclear and polynuclear ladder complexes

The potentials of electrochemical oxidation and reduction of the polynuclear ladder complexes Cp(CO)LM-η ¹, η⁵-C₅H₄Mn(CO)₂L (M = Fe or W(CO); L = PPh₃ or CO), μ-(C≡ C)[C₅H₄(CO)₂Fe-η¹, η⁵-C₅H₄Mn(CO)₃]₂, and MeSi[C₅H₄(CO)₂Fe-η¹, η⁵-C₅H₄Mn(CO)₃]₃ were measured, and the mechanism of these processes is proposed. The change in the electron density at the atom of one metal (Fe or W) is transferred along the σ-and σ-bond chain in the cyclopentadienyl bridge to the atom of another metal (Mn) and, on the contrary, the perturbing effect of the substituent is somewhat weakened. Published In Russian In Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, Pp. 761–765, May, 2006.     

η3-Propargyl complexes of molybdenum, tungsten, and rhenium

The reactions of the Me _n C₆H_6−n M(CO)₃ (M=Cr, Mo, W;n=3, 5, 6) and C₅R₅M(CO)₃ (M=Mn, Re; R=H, Me) complexes with propargyl alcohol in acidic media under UV irradiation were studied. Novel Me _n C₆H_6−n M(CO)₂(η³-C₃H₃)BF₄ (M=Mo, W;n=3, 5, 6) and C₅R₅Re(CO)₂(η³-C₃H₃)CF₃SO₃ complexes with the 3ē-propargyl ligand were synthesized, and their properties compared with those of similar η³-allyl derivatives. The structure and dynamic propeties of the compounds obtained are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1796–1803, September, 1999.     

Investigation of Novel Organometallics by Thermal Spectroscopic Methods

The photolysis of W(CO)₆in CH₂Cl₂ produces (CO)₅WCH₂Cl₂. The high reactivity of (CO)₅WCH₂Cl₂ (1) was exploited to synthesize a vinylidene complexes via the acetylene-vinylidene rearrangement. The addition of a terminal acetylene (H-C≡C-COOCH₃) to a solution of (1) produced the η²-acetylene-pentacarbonyltungsten complex (CO)₅W(η²-HC≡C-COOCH₃) in good yield. The production of the vinylidene complex (CO)₅W=C=CH-COOCH₃in equilibrium with the acetylene complex in the reaction medium was verified experimentally by reaction with excess imine. The heterocyclic organometallic compound of tungsten obtained was separated and purified and its structure was studied by IR, ¹H NMR, ¹³C NMR and mass spectrometry in comparison with the thermal analysis and elemental analysis data. The final aim of this investigation is the development of a new alternative route to a β-lactame with antibacterial activity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrochemical synthesis and properties of δ-fluoroacyl and δ-perfluoroalkyl transition metal complexes

The electrochemical synthesis of δ-fluoroacyl complexes [M]-δ-COR_f(M=C₅H₅(CO)₃W or (CO)₅Mn; R_f=CF₃ or C₄F₉) was performed according to two procedures: (1) the preliminary electrochemical synthesis of [M]⁻ from [M]₂ followed by reaction with a fluorine-containing compound and (2) the electrochemical synthesis of [M]⁻ in the presence of a fluorine-containing compound. Trifluoroacetic anhydride was demonstrated to be the best acylating agent in these reactions. The electrochemical properties of the resulting complexes were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 373–375, February, 2000.     

Electrochemical reductive carbon-to-carbon coupling of σ-ethynyl complexes of transition metals

The electrochemical properties of σ-ethynyl complexes of chromium subgroup metals were studied by cyclic voltammetry and preparative-scale electrolysis. The redox cycle of C₅H₅(CO)₃CrC=CPh was shown to give the bis-carbyne complex (η⁵-C₅H₅)(CO)₂Cr≡C-C(Ph)=C(Ph)-C-Cr(CO)₂(η⁵-C₅H₅) formedvia the reductive C_β−C_β coupling of ethynyl moieties. The influence of the nature of the metal atom and the ligand environment on the course of this reaction was considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1955–1958, October, 1998.     

Synthese,Struktur und Reaktivität von η3‐1,2‐Diphosphaallylkomplexen sowie von [{(η5‐C5H5)(CO)2W–Co(CO)3}{μ‐AsCH(SiMe3)2}(μ‐CO)]

Syntheses, Structure and Reactivity of η³‐1,2‐Diphosphaallyl Complexes and [{(η⁵‐C₅H₅)(CO)₂W–Co(CO)₃}{μ‐AsCH(SiMe₃)₂}(μ‐CO)] Reaction of ClP=C(SiMe₂iPr)₂ ( 3 ) with Na[Mo(CO)₃(η⁵‐C₅H₅)] afforded the phosphavinylidene complex [(η⁵‐C₅H₅)(CO)₂Mo=P=C(SiMe₂iPr)₂] ( 4 ) which in situ was converted into the η¹‐1,2‐diphosphaallyl complex [η⁵‐(C₅H₅)(CO)₂Mo{η³‐tBuPPC(SiMe₂iPr)₂] ( 6 ) by treatment with the phosphaalkene tBuP=C(NMe₂)₂. The chloroarsanyl complexes [(η⁵‐C₅H₅)(CO)₃M–As(Cl)CH(SiMe₃)₂] [where M = Mo ( 9 ); M = W ( 10 )] resulted from the reaction of Na[M(CO)₃(η⁵‐C₅H₅)] (M = Mo, W) with Cl₂AsCH(SiMe₃)₂. The tungsten derivative 10 and Na[Co(CO)₄] underwent reaction to give the dinuclear μ‐arsinidene complex [(η⁵‐C₅H₅)(CO)₂W–Co(CO)₃{μ‐AsCH(SiMe₃)₂}(μ‐CO)] ( 11 ). Treatment of [(η⁵‐C₅H₅)(CO)₂Mo{η³‐tBuPPC(SiMe₃)₂}] ( 1 ) with an equimolar amount of ethereal HBF₄ gave rise to a 85/15 mixture of the saline complexes [(η⁵‐C₅H₅)(CO)₂Mo{η²‐tBu(H)P–P(F)CH(SiMe₃)₂}]BF₄ ( 18 ) and [Cp(CO)₂Mo{F₂PCH(SiMe₃)₂}(tBuPH₂)]BF₄ ( 19 ) by HF‐addition to the PC bond of the η³‐diphosphaallyl ligand and subsequent protonation ( 18 ) and/or scission of the PP bond by the acid ( 19 ). Consistently 19 was the sole product when 1 was allowed to react with an excess of ethereal HBF₄. The products 6 , 9 , 10 , 11 , 18 and 19 were characterized by means of spectroscopy (IR, ¹H‐, ¹³C{¹H}‐, ³¹P{¹H}‐NMR, MS). Moreover, the molecular structures of 6 , 11 and 18 were determined by X‐ray diffraction analysis.     

Zwitterionic adducts from addition of imines to the α-carbon atom of pentacarbonyl(vinylidene)chromium and -tungsten complexes

Imines, Im, such as MeN=C(Ph)H (5), 2-methyl 4,5-dihydrothiazole (8a), 2-methyl 4,5-dihydrooxazole (8b) and MeN=C(OMe)Me (13) add to the α-carbon atom of the vinylidene ligand in [(CO)₅Cr=C=CMe₂] (4) to give isolable zwitterionic adducts, [(CO)₅Cr⁻–C(=CMe₂)(Im⁺)]. The reaction of [(CO)₅W=C=CPh₂] (12) with 13 also yields an adduct, [(CO)₅W⁻–C(=CPh₂){NMe=C(OMe)Me}⁺] (15), whereas from the corresponding reaction of 4 with xanthylideneimine, H–N=C(C₆H₄)₂O (16), a carbene complex, [(CO)₅Cr=C(i-Pr)–N=C(C₆H₄)₂O] (17), is obtained. Complex 17 presumably is formed by initial addition of 16 to 4 and subsequently rapid rearrangement. In solution, the adduct [(CO)₅Cr⁻–C(=CMe₂)(NMe=C(Ph)H)⁺] (6) slowly cyclizes to form the 2-azetidin-1-ylidene complex [(CO)₅Cr= Me₂] (7). In contrast, when solution of those zwitterions are heated that are formed by addition of 4,5-dihydrothiazole or 4,5-dihydrooxazole to 4, no cyclization is observed but rather the formation of 4,5-dihydrothiazole and 4,5-dihydrooxazole complexes, respectively. The structures of two adducts, [(CO)₅Cr⁻–C(=CMe₂)(Im⁺)] (Im=MeN=C(Ph)H, 2-methyl 4,5-dihydrothiazole) and of the substitution product [(CO)₅W(2-methyl 4,5-dihydrothiazole)] have been established by X-ray structural analyses.     

The Shortened Transition Metal–Tellurium Bonds in Organometallic Clusters

The shortening of partly multiple M–Te (M = Mn, Fe, Co, Cr or W) bonds is observed for two classes of organometallic compounds: (1) formally electron-deficient species with additional donor–acceptor interaction between Te lone pairs and half-occupied d-orbitals of M; (2) formally electron-saturated species having additional dative interaction between M lone pairs and LUMO of Te. These compounds could be prepared by two main methods: (a) interaction of [CpMn(CO)₂PhC(O)⁻]Li⁺ with Te proceeds via formation of intermediate {[CpMn(CO)₂]₂Te}²⁻ which is further transformed into binuclear complex [CpMn(CO)₂]₂Te(CH₂Ph)₂ or into trinuclear ditelluride cluster [CpMn(CO)₂]₃Te₂ on one hand or to mixed-metal monotelluride clusters [CpMn(CO)₂]₂TeM(CO)₅ on another hand. (b) treatment of Fe(CO)₅, CpMn(CO)₂(THF) or Me₄C₄Co(CO)₂I with [PhTeI]₄, PhTeI₃ or PhTeI₂HC = CPhI results in different PhTeI-containing complexes of Fe, Mn or Co. The molecular structures of all new compounds were studied by means of X-ray diffraction analyses and the mechanism of M–Te bond shortening is discussed. Proceeding of the international workshop on transition metal clusters, 3–5 July 2008, Université de Rennes 1, Campus de Beaulieu, Rennes, France.     

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.     

Synthesis of neutral tri- and tetranuclear organometallic clusters of group VIII transition metals

A number of earlier unknown tri- and tetranuclear organometallic clusters of group VIII transition metals was synthesized by the addition of coordinatively unsaturated species to a single metal-metal bond. A number of novel heteronuclear clusters, CpCp ₂ ^′ Rhm₂(μ−CO)₃(μ₃−CO), (Cp′=Cp, Cp^*; M₂=Ru₂, Fe₂; RuFe); Cp₂Cp ₂ ^* Rh₂M₂(μ₃−CO)₃ (M = Ru, Fe); , Cp₃Cp^*Rh₃M(μ₃−CO)₂(μ₃−d) (M = Ru, Fe); Cp₂Cp ₂ ^*> Rh₂Co₂(μ₃−CO)₂,etc., was obtained. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 579–586, March, 1997.     

N-Heterocyclic Silylenes as Ligands in Transition Metal Carbonyl Chemistry: Nature of Their Bonding and Supposed Innocence

A study on the reactivity of the N-heterocyclic silylene Dipp₂NHSi (1,3-bis(diisopropylphenyl)-1,3-diaza-2-silacyclopent-4-en-2-yliden) with the transition metal complexes [Ni(CO)₄], [M(CO)₆] (M=Cr, Mo, W), [Mn(CO)₅(Br)] and [(η⁵-C₅H₅)Fe(CO)₂(I)] is reported. We demonstrate that N-heterocyclic silylenes, the higher homologues of the now ubiquitous NHC ligands, show a remarkably different behavior in coordination chemistry compared to NHC ligands. Calculations on the electronic features of these ligands revealed significant differences in the frontier orbital region which lead to some peculiarities of the coordination chemistry of silylenes, as demonstrated by the synthesis of the dinuclear, NHSi-bridged complex [{Ni(CO)₂(μ-Dipp₂NHSi)}₂] ( 2 ), complexes [M(CO)₅(Dipp₂NHSi)] (M=Cr 3 , Mo 4 , W 5 ), [Mn(CO)₃(Dipp₂NHSi)₂(Br)] ( 9 ) and [(η⁵-C₅H₅)Fe(CO)₂(Dipp₂NHSi-I)] ( 10 ). DFT calculations on several model systems [Ni(L)], [Ni(CO)₃(L)], and [W(CO)₅(L)] (L=NHC, NHSi) reveal that carbenes are typically the much better donor ligands with a larger intrinsic strength of the metal–ligand bond. The decrease going from the carbene to the silylene ligand is mainly caused by favorable electrostatic contributions for the NHC ligand to the total bond strength, whereas the orbital interactions were often found to be higher for the silylene complexes. Furthermore, we have demonstrated that the contribution of σ- and π-interaction depends significantly on the system under investigation. The σ-interaction is often much weaker for the NHSi ligand compared to NHC but, interestingly, the π-interaction prevails for many NHSi complexes. For the carbonyl complexes, the NHSi ligand is the better σ-donor ligand, and contributions of π-symmetry play only a minor role for the NHC and NHSi co-ligands.     

Tungsten‐183 NMR study of cis‐[W(CO)4(PPh3)(4‐RC5H4N)]; effect of varying the σ donor strength of the pyridine

Tungsten‐183 NMR data are reported for the complexes cis‐[W(CO)₄(PPh₃)(4‐RC₅H₄N)] (R = H, Me, Ph, COMe, COPh, OMe, NMe₂, Cl, NO₂). The ¹⁸³W chemical shift (obtained by indirect detection using ³¹P) is found to correlate with the Hammett σ function for the group R, with ¹⁸³W shielding increasing approximately linearly with the donor strength of the pyridine over a range of 93 ppm. The X‐ray structures of cis‐[W(CO)₄(PPh₃)(4‐MeOC₅H₄N)] and cis‐[W(CO)₄(PPh₃)(4‐PhCOC₅H₄N)] are also reported. Copyright © 2013 John Wiley & Sons, Ltd.     

Modern aspects on tri- and tetranuclear cluster complexes supported by phosphido bridges

This report on small cluster complexes with metal-metal bonds in the field of coordination chemistry documents results in the following scientific areas. (1) Systematic synthetic routes via ditransition metal carbonyl derivative of manganese and rhenium (group 7) to functionalizedtriangulo- andtetrahedro-clusters including structural characterization, (2) Dynamic properties of mono- and diauration isomers like M₂(μ-AuPR₃)(μ-PCyH)(CO)₈/M₂(μ-H)(μ₃-PCy(AuPR₃))(CO)₈ (isomerization) and M₂(μ-AuPR₃)₂(μ₄-PCy)(CO)₈/M₂(μ-AuPR₃)(μ₃-PCy(AuPR₃))(CO)₈ (M = Mn, Re; R = organic residue) (rearrangement and valence isomerization) and MM’(μ-H)(μ-PCy₂)(μ₄-PCy(AuPR₃))(CO)₆ (M = M’, M ≠ M’) (topomerization) going from one to the other homologue and the kinetic study of isomerization in the framework Re₂(AuPCy₃)₂(μ-PMeN₂(μ-C(Bu)O)(CO)₆, (3) Correlations of chirality transfer in diastereomerictetrahedro-clusters Re₂(M¹PR₃)₂(μ-PCy₂)(CO)₇(η¹-L*) (M¹ = coin metals, L* = chiral ligand as (+) or (-) prolinate, for example) from CD data. These selected contributions will be discussed to answer the question “Do small cluster complexes remain as a future challenge in cluster chemistry?”     

Kinetics and mechanism of the reactions of hexaaqua rhodium (III) with sulphur (IV) in aqueous medium

An O-bonded sulphito complex, Rh(OH₂)₅(OSO₂H)²⁺, is reversibly formed in the stoppedflow time scale when Rh(OH₂) ₆ ³⁺ and SO₂/HSO ₃ ⁻ buffer (1 <pH< 3) are allowed to react. For Rh(OH₂)₅OH₂₊+ SO₂ □ Rh(OH₂)₅(OSO₂H)²⁺ (k₁/k_-1), k₁ = (2.2 ±0.2) × 10³ dm³ mol⁻¹ s⁻¹, k₋1 = 0.58 ±0.16 s⁻¹ (25°C,I = 0.5 mol dm⁻³). The protonated O-sulphito complex is a moderate acid (K _d = 3 × 10⁻⁴ mol dm⁻³, 25°C, I= 0.5 mol dm⁻³). This complex undergoes (O, O) chelation by the bound bisulphite withk= 1.4 × 10⁻³ s⁻¹ (31°C) to Rh(OH₂)₄(O₂SO)⁺ and the chelated sulphito complex takes up another HSO ₃ ⁻ in a fast equilibrium step to yield Rh(OH₂)₃(O₂SO)(OSO₂H) which further undergoes intramolecular ligand isomerisation to the S-bonded sulphito complex: Rh(OH₂)₃(O₂SO)(OSO₂)^- → Rh(OH₂)₃(O₂SO)(SO₃)⁻ (k _iso = 3 × 10⁻⁴ s⁻¹, 31°C). A dinuclear (μ-O, O) sulphite-bridged complex, Na₄[Rh₂(μ-OH)₂(OH)₂(μ-OS(O)O)(O₂SO)(SO₃) (OH₂)]5H₂O with (O, O) chelated and S-bonded sulphites has been isolated and characterized. This complex is sparingly soluble in water and most organic solvents and very stable to acid-catalysed decomposition     

The synthesis and characterization of metal-containing vinylic monomers of iron and tungsten

A series of metal-containing vinylic monomers of the type L_nM(COC₆H₄CH=CH₂) and L_nM (COCH=CHC₆H₅) [L_nM = (η⁵-C₅H₅)Fe(CO)₂, (η⁵-C₅Me₅)Fe(CO)₂ and (η⁵-C₅H₅)W(CO)₃] were prepared by the reaction of the appropriate metal anion with either 4-vinylbenzoyl chloride or cinnamoyl chloride. (η⁵-C₅H₅)(CO)₂FeCOCH=CH₂ was prepared by the reaction of Na[(η⁵-C₅H₅)Fe(CO)₂] and acryloyl chloride, whereas the compound (η⁵-C₅H₅)(CO)₂Fe(C₆H₄CH=CH₂) was prepared via a transmetallation reaction using a palladium catalyst. All compounds were fully characterized using FTIR, ¹H and ¹³C NMR spectroscopy and mass spectrometry. Copyright © 1998 John Wiley & Sons, Ltd.     

Reactions of carbonylmetallate anions with 1-haloalkynes

The main regularities of the reactions of 1-haloalkynes RC≡CX with carbonylmetallate anions [(η⁵-C₅R′₅)(CO)₃M]⁻ (R′ = H (1–3),, M=Cr (1), M=Mo (2), or M=W (3); R′ =Me (4–6), M=Cr (4), M=Mo (5), or M=W (6) were revealed. It was established that the first stage of the reactions of anions1–6 with bromo- or iodoalkynes RC≡CX (X=Br or I) involved the transfer of the halogen atom from the sp-hybridized carbon atom to the transition metal atom to form carbonyl halides [(η⁵-C₅R′₅)(CO)₃MX. To the contrary, the reactions of anions1–6 with chloroalkynes RC≡CCl proceeded selectively as a nucleophilic substitution at the unsaturated carbon atom, the reaction rate being governed by the nucleophilicity of the carbonylmetallate anions and the electron-withdrawing ability of the R group. These reaction paths are consistent with the structures of the lowest unoccupied molecular orbitals (LUMO) in the PhC≡CX molecules (X=Cl, Br, or I) calculated by the MNDO/PM3 method. In the case of the reactions of 1-chloroheptyne-1 C1C≡CC₅H₁₁ ⁿ, anions1–3 appeared to be insufficiently nucleophilic, but these reactions can be performed as cross-coupling of the carbonylmetallate anions with chloroalkynes catalyzed by palladium complexes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1176–1184, June, 1999.     

A General Pathway to Heterobimetallic Triple-Decker Complexes

A systematic study on the reactivity of the triple-decker complex [(Cp’’’Co)₂(μ,η⁴:η⁴-C₇H₈)] ( A ) (Cp’’’=1,2,4-tritertbutyl-cyclopentadienyl) towards sandwich complexes containing cyclo-P₃, cyclo-P₄, and cyclo-P₅ ligands under mild conditions is presented. The heterobimetallic triple-decker sandwich complexes [(Cp*Fe)(Cp’’’Co)(μ,η⁵:η⁴-P₅)] ( 1 ) and [(Cp’’’Co)(Cp’’’Ni)(μ,η³:η³-P₃)] ( 3 ) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) were synthesized and fully characterized. In solution, these complexes exhibit a unique fluxional behavior, which was investigated by variable temperature NMR spectroscopy. The dynamic processes can be blocked by coordination to {W(CO)₅} fragments, leading to the complexes [(Cp*Fe)(Cp’’’Co)(μ₃,η⁵:η⁴:η¹-P₅){W(CO)₅}] ( 2 a ), [(Cp*Fe)(Cp’’’Co)(μ₄,η⁵:η⁴:η¹:η¹-P₅){(W(CO)₅)₂}] ( 2 b ), and [(Cp’’’Co)(Cp’’’Ni)(μ₃,η³:η²:η¹-P₃){W(CO)₅}] ( 4 ), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp’’’Ni)₂(μ,η²:η²-P₂)] ( 5 ). All compounds were fully characterized using single-crystal X-ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis.     

Synthesis and molecular structures of heterometallic complexes [RC5H4Fe(CO)2]2 Sn(TePh)2 and their adducts with chromium and tungsten carbonyls or with trimethylplatinum iodide

Complexes [RC₅H₄Fe(CO)₂]₂Sn(TePh)₂ (R=H, Me) containing stable heterometallic Fe−Sn−Fe fragments with two phenyltellurium groups at the tin atom were synthesized from [RC₅H₄Fe(CO)₂]₂SnCl₂ (R=H, Me) and sodium phenyltelluride and their structures were established by X-ray analysis. Their chelates with tungsten tetracarbonyl, [RC₅H₄Fe(CO)₂]₂Sn(TePh)₂[W(CO)₄] (R=Me, H), and complexes with two Cr(CO)₅ fragments or dimeric trimethylplatinum iodide were synthesized and studied by X-ray analysis. Thermal decomposition of [RC₅H₄Fe(CO)₂]₂Sn(TePh)₂ complexes and their adducts with ML fragments (ML=W(CO)₄, 2 Cr(CO)₅, (Me₃PtI)₂) into inorganic tellurides of a preset mixed-metal—chalcogenide composition was studied by differential scanning calorimetry. The temperature of complete elimination of organic fragments from methylcyclopentadienyl complexes is about 100°C lower than in the case of cyclopentadienyl analogs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1766–1772, September, 1999.     

Kinetic and thermochemical characteristics of the dissociation of Mo(CO)6 and W(CO)6

The thermal dissociation of gaseous Mo(CO)₆ and W(CO)₆ in an argon carrier gas, Mo(CO)₆ → Mo(CO)₅ + CO (1) and W(CO)₆ → W(CO)₅ + CO (2), is studied over temperature ranges of ∼585–685 K for (1) and ∼690−810 K for (2) at a total gas concentrations of 4 × 10⁻⁶ and 4 × 10⁻⁵ mol/cm³ by using the shock tube technique in conjunction with absorption spectrophotometry. The measured rate constants are extrapolated to the high-pressure limit by means of a newly developed procedure, with the resultant expressions for the indicated temperature ranges reading as k_d1,∞(T),[s⁻¹] = 10^{16.12 ± 0.68}exp[(−148.8 ± 8.1 kJ/mol)/RT] and k_d2,∞(T),[s⁻¹] = 10^{15.93 ± 0.63}exp[(−171.7 ± 8.9 kJ/mol)/RT]. Comparison of the high-pressure dissociation rate constants with the published data revealed a considerable discrepancy, a tentative explanation of which is given. Based on the obtained high-pressure dissociation rate constants and the available data on the high-pressure room-temperature rate constants for the reverse reaction of recombination, the first bond dissociation energies for these molecules are evaluated and compared with previous determinations, both theoretical and experimental. The enthalpies of formation of Mo(CO)₅ and W(CO)₅ are determined: Δ_fH°(Mo(CO)₅, g, 298.15 K) = −644.1 ± 5.6 kJ/mol and Δ_fH°(W(CO)₅, g, 298.15 K) = −581.9 ± 6.6 kJ/mol. Based on the enthalpies of formation of Mo(CO)₅, W(CO)₅, Mo(CO)₆, and W(CO)₆, and the published molecular parameters of these four species, their thermochemical functions are calculated and presented in the form of NASA seven-term polynomials.     

13C and19F NMR study of α,β-difluorostyryl derivatives of transition metal carbonylates. A method of signal assignment based on the carbon—fluorine spin-spin coupling constants

The¹³C and¹⁹F NMR spectra ofZ- andE-isomers of β-X-substituted α,β-difluorostyrenes (X=F, Cl, CpFe(CO)₂, Re(CO)₅, Re₂(CO)₉Na) were studied. Direct and long-range (across 1–5 bonds) spin-spin coupling constants and the (¹³C−¹²C) isotope shifts in the¹⁹F NMR spectra were determined. The study of the¹³C satellites in the¹⁹F NMR spectra of substituted difluorostyrenes permitted assignment of the¹³C NMR signals of the vinylic carbon atoms. Similarly, the signals in¹⁹F NMR spectra were assigned based on coupling constants of fluorine withipso-carbon. These assignments were found to be in good agreement with the data available from the literature (X=F, Cl). The developed approach was applied to the elucidation of the structure ofZ−PhCF=CClFe(CO)₂Cp. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya. No. 8, pp. 1575–1579, August, 1998.