Synthesis,spectral properties and reactions of the novel dinuclear alkyne complexes [M(μ-I)I(CO)(NCMe)(η2-PhC2R)]2 (M = Mo or W,R = Ph or Me)

[MI₂(CO)₃(NCMe)₂] (M = Mo or W) and PhC₂R (R = Ph or Me) react in CH₂Cl₂ to initially afford the “four-electron” alkyne complexes [MI₂(CO)(NCMe)₂(η²-PhC₂R)], which subsequently dimerize to the novel iodide-bridged compounds [M(μ-I)I(CO)(NCMe)(η²-PhC₂R)]₂, with loss of acetonitrile. These complexes react via symmetrical cleavage of the iodide bridges.     

Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(C=CHR)(dppe)(η-C₇H₇)](+) and [W(C≡CR)(dppe)(η-C₇H₇](n+) (n = 0 or 1)

The first examples of vinylidene complexes of the cycloheptatrienyl tungsten system [W(C=CHR)(dppe)(η-C?H?)](+) (dppe = Ph?PCH?CH?PPh?; R = H, 3; Ph, 4; C?H?-4-Me, 5) have been synthesised by reaction of [WBr(dppe)(η-C?H?)], 1, with terminal alkynes HC≡CR; a one-pot synthesis of 1 from [WBr(CO)?(η-C?H?)] facilitates its use as a precursor. The X-ray structure of 4[PF?] reveals that the vinylidene ligand substituents lie in the pseudo mirror plane of the W(dppe)(η-C?H?) auxiliary (vertical orientation) with the phenyl group located syn to the cycloheptatrienyl ring. Variable temperature 1H NMR investigations on [W(C=CH?)(dppe)(η-C?H?)][PF?], 3, estimate the energy barrier to rotation about the W=C(α) bond as 62.5 ± 2 kJ mol?1; approximately 10 kJ mol?1 greater than for the molybdenum analogue. Deprotonation of 4 and 5 with KOBu(t) yields the alkynyls [W(C≡CR)(dppe)(η-C?H?)] (R = Ph, 6; C?H?-4-Me, 7) which undergo a reversible one-electron oxidation at a glassy carbon electrode in CH?Cl? with E(?) values approximately 0.12 V negative of Mo analogues. The 17-electron radicals [6](+) and [7](+) have been investigated by spectroelectrochemical IR, UV-visible and EPR methods. The electronic structures of representative vinylidene (3) and alkynyl (6) complexes have been investigated at the B3LYP/Def2-SVP level. In both cases, electronic structure is characterised by a frontier orbital with significant metal d(z2)character and this dominates the structural and spectroscopic properties of the system.     

Synthesis and characterization of stable osmafuran starting from HC≡CCH(OH)C≡CH and OsHCl(CO)(PPh3)3

This paper presents a new convenient route to prepare osmafuran starting from readily accessible HC≡CCH(OH)C≡CH and OsHCl(CO)(PPh₃)₃. Treatment of a solution of OsHCl(CO)(PPh₃)₃ in dichloromethane with HC≡CCH(OH)C≡CH, followed by the addition of acetic acid, produced osmafuran [Os(CHC(PPh₃)CO(CH₂CH₃))Cl(CO)(PPh₃)₂]Cl (2). 2 has been isolated in good yield and fully characterized. ¹H and ¹³C NMR spectra show the characteristic downfield chemical shifts of the ring hydrogen and carbon atoms. NMR and X-ray diffraction data provide strong evidence for the aromatic nature of 2. Probably due to the effect of the phosphonium substituent, 2 exhibits remarkable thermal stability, air stability and lower reactivity.

     

Reactivity of [trans-R2MoO(NNPhR′)(o-phen)] toward R′PhNNH2 and R′PhNNH3+Cl−, R=Me,Ph and R′=Me,Ph. X-ray structure of [trans-MeClMoO(NNPh2)(o-phen)]

The reactivities of [trans-R₂MoO(NNPhR′)(o-phen)], R=R′=Me (1); R=Me, R′=Ph (2); R=Ph, R′=Me (3); R=R′=Ph (4), toward (i) neutral 1,1-disubstituted hydrazines, R′PhNNH₂ and (ii) 1,1-disubstituted hydrazine hydrochlorides, R′PhNNH₂·HCl, R′=Me, Ph, were studied in acetonitrile. In the first case, no condensation reaction of the free oxo group was observed under different experimental conditions. In the second case, using a 1:1 precursor/hydrazine hydrochloride molar ratio, the oxo group was also unreactive, instead one methyl or phenyl group bonded to molybdenum was displaced as methane or benzene and was subsequently substituted by one chloride ligand affording complexes formulated as [trans-RClMoO(NNPhR′)(o-phen)], R=R′=Me (5); R=Me, R′=Ph (6); R=Ph, R′=Me, (7)·MeCN; R=R′=Ph, (8)·MeCN. Finally, when a 1:2 precursor/hydrazine hydrochloride molar ratio was used, both methyl and phenyl groups were substituted affording complexes formulated as [trans-Cl₂MoO(NNPhR′)(o-phen)], R′=Me (9), R=Ph (10). The new organometallic compounds were characterised by IR, UV–Vis and ¹H NMR spectroscopy while the crystal and molecular structure of 6 was determined by X-ray diffraction analysis.     

Structure,synthesis, and thermal properties of trans-[Ru(NO)(NH3)4(SO4)]NO3·H2O

In treatment of trans-[Ru(NO)(NH₃)₄(OH)]Cl₂ with concentrated sulfuric acid on heating trans-[Ru(NO)(NH₃)₄(SO₄)](HSO₄)·H₂O (I) is obtained with a yield close to quantitative. In the interaction of the saturated solution of I with a saturated NaNO₃ solution a trans-[Ru(NO)(NH₃)₄(SO₄)]NO₃·H₂O (II) precipitate forms whose structure is determined by single crystal XRD: space group P2₁2₁2₁, a = 6.8406(3) Å, b = 12.6581(5) Å, c = 13.3291(5) Å. A monodentately coordinated sulfate ion is in the trans-position to the nitroso group. Compound II is characterized by IR spectroscopy, powder XRD, and diffuse reflectance spectroscopy. The process of its thermolysis is studied; by differential scanning calorimetry the thermal effect of the dehydration reaction occurring on heating to 120°C (ΔH = 58.9 ± 1.5 kJ/mol) is estimated. The final product of the thermolysis of II is a mixture of Ru and RuO₂.     

The complexation of cadmium acetate and propionate by phenanthroline. Structure and properties of [Cd(CH3COO)2(C12H8N2)(H2O)] · H2O and [Cd(CH3CH2COO)2(C12H8N2)]2 · 2CH3CH2COOH

The coordination compounds [Cd(CH₃COO-κO ¹,O ²)₂(phenanthroline-kN ¹ N ²)(H₂O)] · H₂O (1) and [Cd{μ-(CH₃CH₂COO-κO ¹,O ²)}₂(phenanthroline-κN ¹,N ²)]₂ · 2CH₃CH₂COOH (2) were synthesized and characterized by elemental and thermal analysis and IR spectroscopy. Crystal and molecular structures of both compounds were determined. The complexes are air stable and fairly soluble in water. In both compounds the cadmium is seven-coordinate and contains chelating phenanthroline and two chelating carboxylate groups in the inner coordination sphere. The seventh coordinating oxygen belongs to water in 1 and to bridging carboxylate in 2. All carboxylate groups are bonded unsymmetrically to the central atom. The coordination polyhedra can be described as distorted pentagonal bipyramid (compound 1) and distorted capped tetragonal bipyramid (compound 2). In the structure of 1 intermolecular O(water)–H ··· O (water/carboxylate) hydrogen bonds create a two-dimensional net along the crystallographic a0c plane. Each molecule of 2 is connected to two propionic acid molecules via hydrogen bonds. In both compounds exist π-stacking interactions.     

The synthesis and spectral properties of the novel monodentate(s) coordinated thiosemicarbazide and thiosemicarbazone complexes [Fe(CO)2L(η5-C5H5)][PF6] (L = H2NNHCSNH2, cy-C5H10CNNHCSNH2 or R′R″CNNHCSNH2, R′ = R″ = Me; R′= H,R″ = Ph; R′= H,R″ = p-NO2Ph,R′= Me,R″ = p-MePh)

The acetone complex [Fe(CO)₂(Me₂CO)(η⁵-C₅H₅)][PF₆] reacts with L (L = H₂NNHCSNH₂, cy-C₅H₁₀CNNHCSNH₂, or R′R″CNNHCSNH₂ where R′ = R″ = Me; R′ = H, R″ = Ph; R′ = H, R″ = p-NO₂Ph; R′ = p-MePh) in refluxing trichloromethane to give the new complexes [Fe(CO)₂L(η⁵-C₅H₅)][PF₆]. The complexes are clearly coordinated through the sulphur atom since the thiosemicarbazide complex reacts with benzaldehyde to afford the corresponding thiosemicarbazone compound.     

Synthesis,thermal and spectroscopic properties,and crystal structures of [Co(bba)2(H2O)(phen)] and [Ni(bba)2(H2O)(butOH)(phen)] (bba = 2-benzoylbenzoate,phen = 1,10-phenanthroline,butOH = butanol)

Aquabis(2-benzoylbenzoato)(1,10-phenanthroline)cobalt(II) and aquabis(2-benzoylbenzoato)(butanol)(1,10-phenanthroline)nickel(II) have been prepared and characterized by elemental analyses, IR and electronic spectroscopy, magnetic measurements, and single-crystal X-ray diffraction. [Co(bba)₂(H₂O)(phen)] (1) and [Ni(bba)₂(H₂O)(butOH)(phen)] (2) consist of neutral monomeric units and crystallize in the monoclinic (P2(1)) and triclinic (P 1) crystal systems, respectively. The cobalt(II) and nickel(II) sit on inversion centres and exhibit distorted octahedral coordination. Phen is bidentate chelating. In 1, bba is both monodentate and bidentate, whereas in 2 bba is only monodentate. bba ligands are coordinated to metal(II) with carboxylates and IR spectra of both complexes display characteristic absorptions of carboxylate anions {ν(OCO)_asym and ν(OCO)_sym} of bba. Thermal analysis shows that mass losses of 1 from 105°C to 456°C correspond to decomposition of phen and bba, while for 2 these occur at 271–529°C.     

Reactions of cationic vinylidene complexes [Fe{=C=C(R1)R2}(η-C5H5)(dppm)]+[dppm = bis(diphenylphosphino)methane] with nucleophiles: stereoselective synthesis and crystal structure of the alkenyl complex (E)-[Fe{C(H)=C(Me)Ph}(η-C5H5)(dppm)]

The reactivity of the cationic vinylidene complexes [Fe{CC(R¹)R²}(η-C₅H₅(dppm)]⁺ toward different nucleophiles has been investigated. Whereas the disubstituted complexes (R¹ = Me; R² = Ph or ^tBu) are unreactive with water and methanol, the addition of the anion hydride proceeds stereoselectively to give the alkenyl E isomers. The structure of (E)-[Fe{C(H)C(Me)Ph}(η-C₅H₅(dppm)] has been determined by an X-ray diffraction study. Nucleophilic additions to the unsubstituted complex (R¹ = R² = H) have also been examined.     

Synthesis,crystal structure and magnetic properties of a 1D coordination polymer[Ni(phth)(phen)(H2O)] n · n H2O

A new one-dimensional coordination polymer [Ni(phth)(phen)(H₂O)] _n ?·?nH₂O was synthesized. The structure was determined by X-ray crystallography revealing that each nickel atom is five-coordinate bridged via phthalate ion to form a zigzag chain. The chains are further linked together via hydrogen-bonding interactions to construct a three dimensional supramolecular network. The magnetic properties of the complex show that there are weak antiferromagnetic interactions between Ni(II) centers.     

Tantalocene complexes as bidentate métalloligands: (C5Me5)(C5H4X)Ta(H2)(PPh2) (C5Me5) (C5H4X)Ta(CO) (PPh2) (X = PPh2, CH2CH2NMe2)

The synthesis of new bidentate métalloligands derived from tantalocene(C₅Me₅)(C₅H₄X)Ta(H₂)(PPh₂) (X = PPh₂, 2P; X = CH₂CH₂NMe₂2N) and (C₅Me₅)(C₅H₄X)Ta(CO)(PPh₂) 4(P,N) is described. When opposed to chromium unsaturated fragments the phosphino functionalised complexes 2P and 4P act as chelating bidentate ligands affording Ta(V) (C₅Me₅)(C₅H₄PPh₂)Ta(CH₂) (μ-PPh₂)Cr(CO)₄ or Ta(III) (C₅Me₅)(C₅H₄PPh₂)Ta(CO)(μ-PPh₂)Cr(CO)₄ bimetallic complexes. The same reaction carried out starting from 2N gives rise to a μ-phosphido, μ-hydrido dibridged complex Cp*(C₅H₄CH₂CH₂NMe₂)TaH(μ-H)(μ-PPh₂)Cr(CO)₄.     

Experimental observation of spin delocalisation onto the aryl-alkynyl ligand in the complexes [Mo(C≡CAr)(Ph2PCH2CH2PPh2)(η-C7H7)]+ (Ar = C6H5, C6H4-4-F; C7H7 = cycloheptatrienyl): an EPR and ENDOR investigation

The paramagnetic aryl-alkynyl complexes [Mo(C≡CAr)(dppe)(η-C(7)H(7))](+) (dppe = Ph(2)PCH(2)CH(2)PPh(2); Ar = C(6)H(5), [1](+); C(6)D(5), [2](+); C(6)H(4)-4-F, [3](+); C(6)H(4)-4-Me, [5](+)) and [Mo(C≡CBu(t))(dppe)(η-C(7)H(7))](+) [4](+), have been investigated in a combined EPR and ENDOR study. Direct experimental evidence for the delocalisation of unpaired spin density over the framework of an aryl-alkynyl ligand has been obtained. The X-band solution EPR spectrum of the 4-fluoro derivative, [3](+), exhibits resolved hyperfine coupling to the remote para position of the aryl group [a(iso)((19)F) = 4.5 MHz, (1.6 G)] in addition to couplings attributable to (95/97)Mo, (31)P and (1)H of the C(7)H(7) ring. A full analysis of the (1)H ENDOR spectra is restricted by the low g anisotropy of the system which prevents the use of orientation selection. However, inter-comparison of the (1)H cw-ENDOR frozen solution spectra of [1](+), [2](+), [4](+) and [5](+), combined with spectral simulation informed by calculated values derived from DFT investigations, has facilitated estimation of the experimental a(iso)((1)H) hyperfine couplings of [1](+) including the ortho, ±3.7 MHz (±1.3 G) and para, ±3.9 MHz (±1.4 G) positions of the C(6)H(5) substituent of the aryl-alkynyl ligand.     

New cyclometalated palladium(II) complexes with iminophosphines: Crystal structures of [Pd(C^N)(o-Ph2PC6H4–CH=NR)][PF6] (C^N=azobenzene,R=Et; C^N=2-phenylpyridine,R=Me)

The synthesis of new cyclometalated compounds of palladium(II) with the mixed-donor bidentate ligands o-Ph₂PC₆H₄–CH=NR is described. Two series of complexes [Pd(C^N)(o-Ph₂PC₆H₄–CH=NR)][PF₆] have been prepared using either azobenzene or 2-phenylpyridine as cyclometalated ligands [C^N=azobenzene (azb); R=Me (1a), Et (2a), ⁿPr (3a), ⁱPr (4a), ^tBu (5a), Ph (6a), NH–Me (7a); C^N=2-phenylpyridine (phpy); R=Me (1b), Et (2b), ⁿPr (3b), ⁱPr (4b), ^tBu (5b), Ph (6b), NH–Me (7b)]. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, FAB, ¹H and ³¹P NMR). The molecular structures of compounds 2a (monoclinic, P 2₁/n) and 1b (monoclinic, C 2/c) have been determined by a single-crystal diffraction study. In both cases this technique revealed the relative trans configuration between the phosphorus atom and the nitrogen atom of the ortho-metalated ligand.     

Synthesis and Characterization of Nitrato-Triamine-Metal(II) Complexes. Conglomerate Crystallization Part 55. Crystal Structure of [Ni(dien)(O2NO)(ONO2)] (I), {[Cu(dien)-(μ-ONO2)]NO3}∞ (II), [Zn(dien)(O2NO)(ONO2)] (III), [Ni(Medpt)(O2NO)(ONO2)] (IV) and [Cu(Medpt)(ONO2)2] (V)

In absolute ethanol and in the presence of triethylorthoformate, reactions of metal(II) nitrates with linear tridentate amines afforded metal complexes of the formula M(NNN)(NO₃)₂, where M = Ni²⁺, Cu²⁺ and Zn²⁺, and NNN = dien and Medpt. The compounds fall into three categories in accordance with their stereochemistry and mode of binding of the nitrato ligands. Compounds I, [Ni(dien)(O₂NO)(ONO₂)] and III, [Zn(dien)(O₂NO)(ONO₂)] are isomorphous and isostructural. They crystallize in the monoclinic space group P2₁/n with nearly identical cell constants. The stereochemistry of these two compounds is such that the terdentate dien ligand forms a fac MN₃ moiety with the two oxygens of the bidentate nitrato ligand trans to the terminal NH₂. These ligands form the base of the octahedral arrangement in which the sixth position, trans to the secondary nitrogen of the dien, is an oxygen of the monodentate nitrato ligand. Compound IV, [Ni(Medpt)(O₂NO)(ONO₂)] falls into the same category as I and III despite the fact that the two rings in the Ni-Medpt moiety are six-membered rings, unlike those in compounds I and III which are five-membered rings. Nevertheless, the nickel-amine arrangement is fac. The bidentate nitrato-oxygens are trans to the terminal NH₂ of the amine ligand, and the oxygen of the monodentate nitrato ligand is trans to the tertiary amine-nitrogen. Such stereochemistry is prevalent for nickel and zinc compounds. Interestingly, compound IV crystallizes as a conglomerate (space group P2₁2₁2₁). Compound II, {[Cu(dien)(μ-ONO₂)]NO₃}_∞ belongs to the second category and has a polymeric structure. The repeating fragment in the polymeric chain is a Cu(dien)-O fragment with the monodentate nitrato ligand occupying an equatorial position of the base. A second oxygen of the equatorial nitrate becomes an axial ligand for an adjacent Cu-N₃O fragment. In this way the substance propagates into an infinite chain. The repeating unit has an effective square pyramidal, five-coordinate, configuration. Finally, the compound crystallizes as a racemate. The second nitrate necessary for charge compensation of this copper(II) compound is ionic and its function is to hold the infinite chains of the lattice. The third category represented by compound V, [Cu(Medpt)(ONO₂)₂] contains two molecules in the asymmetric unit of the racemic lattice (monoclinic, space group P2₁/a). The structure of Cu-Medpt is unlike that of IV in that both species present in the asymmetric unit have the amine ligand in a mer configuration which together with a monodentate oxygen of a nitrato ligand form a base plane of a square pyramid. The fifth ligand of both Cu²⁺ ions is a second monodentate nitrato ligand. The stereochemical differences between the two Cu²⁺ ions are insignificant for the Cu-Medpt fragment, which share the same conformation and configuration. The major difference between the two species is the torsional angles defined by the Cu-O-N-O angles. The difference arises from variation in the hydrogens of the primary amine moieties selected by nitrato-oxygens to form intramolecular hydrogen bonds. Finally, there is a little variation in the equatorial Cu-ONO₂ stereochemistry because of steric hindrance, imposed by the Medpt, preventing large torsional angles by these nitrato ligands. This is evident by comparing the two copper species shown in Finally, nitrate-to-Br ligand exchange was found to take place when KBr pellets are prepared for IR spectral measurements.     

Kinetics of Intramolecular Hydrogen Atom Transfer in the Radicals >Si(O·)(R) (R = H,D, CH3, CD3, and C2H5)

Methods are developed for obtaining oxy radicals by the photodecomposition and thermal decomposition of precursors (Si–O)₂Si(N=N–O^·)(R) and (Si–O)₂Si(O–C^·=O)(R). The mechanism of these processes is established. Kinetic data are obtained for the reaction of hydrogen atom transfer in oxy radicals (Si–O)₂Si(O^·)(R) (R = H, D, CH₃, CD₃, and C₂H₅). The activation energies of hydrogen atom transfer are found for three-, four-, and five-membered transition states: 13.5 ± 1, 18 ± 1, and <10 kcal/mol, respectively. For the reaction of H(D) atom transfer in the (Si–O)₂Si(O^·)(H(D)) radical, the kinetic isotope effect is found. Quantum-chemical calculations were used to determine the structures of transition states in the studied processes. Experimental studies were carried out using ESR spectroscopy.     

Synthesis,crystal and molecular structure of the “slipped” sandwich complex [Ni(η5-P3C2R2)(η3-P2C3R3)] (R = But)

The synthesis of the novel “slipped” sandwich compound [Ni(η⁵-P₃C₂R₂)(η³-P₂C₃R₃)] (R = Bu^t) is described. The mode of attachment of the P₃C₂R₂ and P₂C₃R₃ rings has been determined by NMR spectroscopy and a single crystal X-ray diffraction study.     

Assembly of triorganotin chloride with selenite ligands to macrocyclic,zigzag, helical,and linear structures: syntheses,characterizations, and crystal structures of [R3Sn(O2SeC6H4-4-Et)] n and [R3Sn(O2SeC6H4-2-Et)] n (R = Me,C6H5) complexes

Four new triorganotin(IV) complexes, [R₃Sn(O₂SeC₆H₄-4-Et)]₄ (R = Me 1), [R₃Sn(O₂SeC₆H₄-4-Et)] _n (R = Ph 2), [R₃Sn(O₂SeC₆H₄-2-Et)] _n (R = Me 3; Ph 4) have been synthesized by the treatment of 4-ethylbenzeneseleninic acid, 2-ethylbenzeneseleninic acid, and the corresponding triorganotin(IV) chloride with sodium ethoxide in methanol. All of the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy, TGA, and X-ray crystallography. Crystal structures show that all of the complexes are generated by the bidentate oxygen atoms and the five-coordinated tin centers with trigonal bipyramid geometry. The structural analyses reveal that complex 1 has a centrosymmetric tetranuclear triorganotin selenite with 16-membered macrocycle, which is formed by trimethyltin and ligand alternate linking. A series of C–H···O and π–π stacking interactions in complex 1 play an important function in the supramolecular aggregation. Complex 3 has two 1D spring-like chiral helical chains and crystallizes in the monoclinic space group P2₁, which is chiral. Complex 2 and 4 are both 1D infinite neutral chain polymers and complex 2 forms a 2D supramolecular framework through intermolecular C–H···O interactions.     

Acetylene-allene rearrangement of propargyl systems X—CH2—C≡CH (X = H,Me, NMe2, OMe,F, SMe): an ab initio study

Acetylene—allene rearrangement in propargyl systems XCH₂CHCH (X = H, Me, NMe₂, OMe, F, and SMe) was studied using the ab initio approach. The relative stabilities of the starting and final propyne structures and the corresponding allenes as well as the structure of intermediate carbanions were considered. n--Conjugation was shown to dominate in allene stabilization while the inductive effect of heteroatomic substituents makes at least comparable contribution to stabilization (or destabilization) of the propynyl structure. In particular, relative instability of 1-methoxypropyne can be rationalized by high electronegativity of O atom, which leads to dramatic decrease in the total electron density in the region of the neighboring CC triple bond. The influence of substituents on the mobility of the migrating proton was considered for the gas phase and with solvation effects included. Calculations involving electron correlation at the MP2 level of theory were shown to be insufficient for correct reproduction of the energy differences between the corresponding propynes and allene structures. The results of MP4 calculations with inclusion of ZPE correction are in good agreement with the available experimental data.