The CO and CS bond cleavage in carbon dioxide and tolyl isothiocyanate by reactions with the Mo(0) tetraphosphine complex [Mo{meso-o-C6H4(PPhCH2CH2PPh2)2}(Ph2PCH2CH2PPh2)]

A Mo(0) complex containing a new tetraphosphine ligand [Mo(P₄)(dppe)] (1; P₄ = meso-o-C₆H₄(PPhCH₂CH₂PPh₂)₂, dppe = Ph₂PCH₂CH₂PPh₂) reacted with CO₂ (1 atm) at 60 °C in benzene to give a Mo(0) carbonyl complex fac-[Mo(CO)(η³-P₄O)(dppe)] (2), where the O abstraction from CO₂ by one terminal P atom in P₄ takes place to give the dangling P(O)Ph₂ moiety together with the coordinated CO. On the other hand, reaction of 1 with TolNCS (Tol = m-MeC₆H₄) in benzene at 60 °C resulted in the incorporation of three TolNCS molecules to the Mo center, forming a Mo(0) isocyanide-isothiocyanate complex trans,mer-[Mo(TolNC)₂(η²-TolNCS)(η³-P₄S)] (4), where the S abstraction occurs from two TolNCS molecules by P₄ and dppe to give the η³-P₄S ligand and free dppeS, respectively, together with two coordinated TolNC molecules. The remaining site of the Mo center is occupied by the third TolNCS ligating at the CS bond in an η²-manner. The X-ray analysis has been undertaken to determine the detailed structures for 2 and 4.     

The synthesis and single-crystal X-ray structures of palladium(II) and platinum(II) complexes of the difluorovinyl and 1-chloro-2-fluorovinyl-substituted phosphines, PPh2(Z-CFCFH) and PPh2(E-CClCFH)

The coordination chemistry of the fluorovinyl substituted phosphines PPh₂(Z-CFCFH) and PPh₂(E-CClCFH) with K₂MX₄ (M = Pd, Pt; X = Cl, Br, and I) salts has been investigated resulting in the first reported palladium(II) and platinum(II) complexes of phosphines containing partially fluorinated vinyl groups. The complexes have been characterised by a combination of multinuclear [¹H, ¹³C{¹H}, ¹⁹F, ³¹P{¹H}] NMR spectroscopy, and IR/Raman spectroscopy. The single-crystal X-ray structures of trans-[PdX₂{PPh₂(CFCFH)}₂], X = Cl (1), Br (2), I (3), trans-[PdCl₂{PPh₂(CClCFH)}₂] (4), cis-[PtX₂{PPh₂(CFCFH)}₂], X = Cl (5), Br (6), trans-[PtI₂{PPh₂(CFCFH)}₂] (7), and both cis- and trans-[PtCl₂{PPh₂(CClCFH)}₂] (8), have been determined. Results obtained from spectroscopic and crystallographic data suggest that replacement of a β-fluorine by hydrogen, whilst reducing the steric demand of the ligand, has little effect on the electronic character of the ligand. The presence of a proton in the vinyl group results in short proton-halide secondary interactions in the solid state (d(H?X) = 2.72(3) for 1, and 2.92(5) Å for 2) forming an infinite chain ribbon motif.     

Formation of multifunctional ligands by nucleophilic addition of alcohols and thiols to the alkyne groups in compound C5H5FeC5H4CCSCCH: Reactivity studies

The multifunctional ligands [(Z)-FcCCSC(H)C(H)XR] [X = O, R = Me (2a); X = O, R = Et (2b); X = S, R = Ph (3); X = S, R = C₆F₅ (5)] and [(Z,Z)-Fc(SR)CC(H)SC(H)C(H)SR] [R = Ph (4), C₆F₅ (6)] have been prepared through hydroalkoxylation and hydrothiolation processes of the alkyne groups in the compound FcCCSCCH 1. Reactions between compound 3 and the carbonyl metals Co₂(CO)₈, Os₃(CO)₁₀(NCMe)₂ and Fe₂(CO)₉ have allowed the synthesis of the polynuclear compounds [(Z)-{Co₂(CO)₆}(μ-η²-FcCCSC(H)C(H)SPh)] 9, [(Z)-Os₃(CO)₉(μ-CO){μ₃-η²-FcCCSC(H)C(H)(SPh)}] 10 and [(Z)-{Fe₃(CO)₉}[μ₃,η³-(CCS)-FcCCSC(H)C(H)(SPh)] 11. All the compounds have been characterized by elemental analysis, ¹H and ¹³C{¹H} NMR spectroscopy, mass spectrometry and the crystal structure of compounds [(Z)-FcCCSC(H)C(H)OMe] 2a and [{Co₂(CO)₆}₂(μ-η²:η²-FcCCSCCSiMe₃)] 7 have been solved by X ray diffraction analysis.     

Synthesis and structures of bimetallic silicon-containing imido alkylidene complexes of tungsten (R′O)2(ArN)WCH-SiR2-CHW(NAr)(OR′)2 (R = Me, Ph) and (R′O)2(ArN)WCH-SiMe2SiMe2-CHW(NAr)(OR′)2

Bimetallic alkylidene complexes of tungsten (R′O)₂(ArN)WCH-SiR₂-CHW(NAr)(OR′)₂ (R = Me (1), Ph (2)) and (R′O)₂(ArN)WCH-SiMe₂SiMe₂-CHW(NAr)(OR′)₂ (3) (Ar = ; R′ = CMe₂CF₃) have been prepared by the reactions of divinyl silicon reagents R₂Si(CHCH₂)₂ with known alkylidene compounds R′′-CHMo(NAr)(OR′)₂. (R′′ = Bu^t, PhMe₂C) Complexes 1-3 were structurally characterized. Ring opening metathesis polymerization (ROMP) of cyclooctene using compounds 1-3 as initiators led to the formation of high molecular weight polyoctenamers with predominant trans-units content in the case of 1 and 3 and predominant cis-units content in the case of 2.     

Silicon version of enamines: Amino-substituted disilenes by the reactions of the disilyne RSiSiR (R = SiPr[CH(SiMe3)2]2) with amines

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with secondary or primary amines produced amino-substituted disilenes R(R₂′N)SiSiHR 2a-d (R = SiⁱPr[CH(SiMe₃)₂]₂, R₂′NEt₂N (2a), (CH₂CH₂)₂N (2b), ^tBu(H)N (2c), and Ph₂N (2d)). Spectroscopic and X-ray crystallographic analyses of 2 showed that 2a-c have a nearly coplanar arrangement of the SiSi double bond and the amino group, giving π-conjugation between the SiSi double bond and the lone pair on the nitrogen atom, whereas 2d has a nearly perpendicular arrangement precluding such conjugation. Theoretical calculations indicate that π-conjugation between the π-orbital of the SiSi double bond and the lone pair on the nitrogen atom is markedly influenced by the torsional angle between the SiSi double-bond plane and the amino-group plane.     

Intermolecular hydrogen bonding in the binary mixture [(C2H5)2CO + CH3OH] probed by polarized Raman measurements and DFT calculations

The Raman spectra of neat (C₂H₅)₂CO (pentanone) and its binary mixtures with hydrogen donor solvent (CH₃OH), [(C₂H₅)₂CO + CH₃OH] having different mole fractions of the reference system, (C₂H₅)₂CO in the range 0.1-0.9 at a regular interval of 0.1 were recorded in the CO stretching region. In neat liquid, the Raman peak appears asymmetric. The asymmetric nature of the peak has been attributed to the CO stretching mode of the two conformers of (C₂H₅)₂CO having C₂ and C_2v point groups and the corresponding bands at ∼1711 and ∼1718 cm⁻¹, respectively. A careful analysis of the I_iso (isotropic component of the Raman scattered intensity) at different concentrations reveals that upon dilution with methanol, at mole fraction C = 0.6, an additional peak in the CO stretching region is observed at ∼1703 cm⁻¹ which is attributed to the hydrogen bonding with methanol. A peculiar feature in this study is that upon dilution, the peak at ∼1718 cm⁻¹ shows a minimum at C = 0.6, but on further dilution it shows a blue shift. However, the other peak at ∼1711 cm⁻¹ shows a continuous red shift with dilution as well as a maximum at C = 0.7 in the linewidth vs. concentration plot, which is essentially due to competition between motional narrowing and diffusion phenomena. A significant amount of narrowing in the Raman band at ∼1718 cm⁻¹ can be understood in terms of caging effect of the reference molecule by the solvent molecules at high dilution. A density functional theoretic (DFT) calculation on optimized geometries and vibrational frequencies of two conformers of neat (C₂H₅)₂CO in C₂ ad C_2v forms and the complexes with one and two CH₃OH molecules with both the conformers was performed. The experimental results and theoretical calculations together indicate a co-existence of two conformers as well as hydrogen bonded complex with methanol in the binary mixture, [(C₂H₅)₂CO + CH₃OH] at intermediate concentrations.     

Triosmium compounds containing the oxametallacycle [Os(CO)3{C(R)CHC(O)CHC(H)C5H4FeC5H5}] moiety. Synthesis and electrochemical studies

The compounds [Os₃(CO)₁₀{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe (C₅H₅)}] (2), [Os₃(CO)₉{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}] (3) and [Os₃(CO)₈{μ₃,η²-{CCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}(SCH₂CH₂S)}] (4) have been obtained by rupture of S-C bonds in the ketene dithioacetal [C₅H₅FeC₅H₄CHCHC(O)CHC(SCH₂CH₂S)], in their reaction with the activated cluster [Os₃(CO)₁₀(NCMe)₂]. The presence of an oxametallacycle in these derivatives has been confirmed by an X-ray diffraction analysis. The electrochemical study has indicated the ability of these compounds to modify the electrode surfaces.     

Effect of ketimide ligand for ethylene polymerization and ethylene/norbornene copolymerization catalyzed by (cyclopentadienyl)(ketimide)titanium complexes-MAO catalyst systems: Structural analysis for CpTiCl2(NCPh2)

Ligand effects on the catalytic activity [and norbornene (NBE) incorporation] for both ethylene polymerization and ethylene/NBE copolymerization using half-titanocenes (titanium half-sandwich complexes) containing ketimide ligand of type Cp′TiCl₂[NC(R¹)R²] [Cp′ = Cp (1), C⁵Me⁵ (Cp^∗, 2); R¹,R² = ^tBu,^tBu (a), ^tBu,Ph (b), Ph,Ph (c)]-methylaluminoxane (MAO) catalyst systems have been investigated. CpTiCl₂[NC(^tBu)Ph] (1b) CpTiCl₂(NCPh₂) (1c), and Cp^∗TiCl₂(NCPh₂) (2c) were prepared and identified; the structure of Cp^∗TiCl₂(NCPh₂) (2c) was determined by X-ray crystallography. The catalytic activity for ethylene polymerization increased in the order: 1a > 1b > 1c, suggesting that an electronic nature of the ketimide ligand affects the activity. However, molecular weight distributions for resultant (co)polymers prepared by 1b,c and by 2c-MAO catalyst systems were bi- or multi-modal, suggesting that the ketimide substituent plays a key role in order for these (co)polymerizations to proceed with single catalytically-active species. CpTiCl₂(NC^tBu₂) (1a) exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization.     

Study of ferrocenyl-substituted Co2(CO)6-bispropargylic alcohol complexes as substrates for the formation of chains and macrocycles

Treatment of [Fc-1-R¹-1′-R²] (R¹ = H, R² = CH(O); R¹ = H, R² = CMe(O); R¹ = R² = CMe(O)) with LiCCCH₂OLi (prepared in situ from HCCCH₂OH and n-BuLi) affords the ferrocenyl-substituted but-2-yne-1,4-diol compounds of general formula [Fc-1-R¹-1′-{CR(OH)CCCH₂OH}] (R¹ = R = H (1a); R¹ = H, R = Me (1b); R¹ = CMe(O), R = Me (1c)) in low to high yields, respectively (where Fc = Fe(η⁵-C₅H₄)₂). In the case of the reactions of [Fc-1-R¹-1′-R²] (R¹ = H, R² = CH(O); R¹ = R² = CMe(O)), the by-products [Fc-1-R¹-1′-{CR(OH)(CH₂)₃CH₃}] (R¹ = R = H (2a); R¹ = CMe(O), R = Me (2c)) along with minor quantities of [Fc-1,1′-{CMe(OH)(CH₂)₃CH₃}₂] (3) are also isolated; a hydrazide derivative of dehydrated 2c, [1-(CMeCHCH₂CH₂CH₃)-1′-(CMeNNH-2,4-(NO₂)₂C₆H₃)] (2c′), has been crystallographically characterised. Interaction of 1 with Co₂(CO)₈ smoothly generates the alkyne-bridged complexes [Fc-1-R¹-1′-{Co₂(CO)₆-μ-η²-CR(OH)CCCH₂OH}] (R¹ = R = H (4a); R¹ = H, R = Me(4b); R¹ = CMe(O), R = Me (4c)) in good yield. Reaction of 4a with PhSH, in the presence of catalytic quantities of HBF₄ · OEt₂, gives the mono- [Fc-1-H-1′-{Co₂(CO)₆-μ-η²-CH(SPh)CCCH₂OH}] (5) and bis-substituted [Fc-1-H-1′-{Co₂(CO)₆-μ-η²-CH(SPh)CCCH₂SPh}] (6) straight chain species, while with HS(CH₂)_nSH (n = 2,3) the eight- and nine-membered dithiomacrocylic complexes [Fc-1-H-1′-{cyclo-Co₂(CO)₆-μ-η²-CH(S(CH₂)_n-)CCCH₂S-}] [n = 2 (7a), n = 3 (7b)] are afforded. By contrast, during attempted macrocyclic formation using 4b and HSCH₂CH₂OCH₂CH₂SH dehydration occurs to give [Fc-1-H-1′-{Co₂(CO)₆-μ-η²-C(CH₂)CCCH₂OH}] (8). Single crystal X-ray diffraction studies have been reported on 2c′, 4b, 4c, 7b and 8.     

Hydroxy- and boronic-acid-functionalized carbosilanes: Synthesis and solid state structure of Si(C6H4-4-SiMe2((CH2)3OH))4

Consecutive synthesis methodologies for the preparation of carbosilanes (Ph)(Me)Si((CH₂)₃B(OH)₂)₂ (2), Si(C₆H₄-4-SiMe₂((CH₂)₃B(OH)₂))₄ (5), (Ph)(Me)Si((CH₂)₃OH)₂ (3), and Si(C₆H₄-4-SiMe_3−n((CH₂)₃OH)_n)₄ (6a, n = 1; 6b, n = 2; 6c, n = 3) are reported. Boronic acids 2 and 5 are accessible by treatment of (Ph)(Me)Si(CH₂CHCH₂)₂ (1) or Si(C₆H₄-4-SiMe₂(CH₂CHCH₂))₄ (4a) with HBBr₂·SMe₂ followed by addition of water, while 3 and 6 are available by the hydroboration of 1 or Si(C₆H₄-4-SiMe_3−n(CH₂CHCH₂)_n)₄ (4a, n = 1; 4b, n = 2; 4c, n = 3) with H₃B·SMe₂ and subsequent oxidation with H₂O₂.The single molecular structure of 6a in the solid state is reported. Representative is that 6a crystallized in the chiral non-centrosymmetric space group P2₁2₁2₁ forming 2D layers due to intermolecular hydrogen bond formation of the HO functionalities along the crystallographic a and c axes.     

A new mechanism of nucleophilic vinylic substitution and unexpected products in the reaction of chlorotrifluoroethylene with [Re(CO)5]Na and [CpFe(CO)2]K

The mechanism of chloride substitution in CF₂CFCl with [Re(CO)₅]⁻ and [CpFe(CO)₂]⁻ anions is investigated experimentally and theoretically. The substitution reaction begins with the nucleophile addition to CF₂CFCl producing the carbenoid anion [MCF₂CFCl]⁻ (A) (M = Re(CO)₅, CpFe(CO)₂). This is shown by trapping the intermediate A with electrophiles - proton donor (t-BuOH) to give MCF₂CFClH or with CF₂CFRe(CO)₅ to give acylmetallate III, and by the formation of the substitution products CF₂CFM from the anion A, generated by the deprotonation of MCF₂CFClH with t-BuOK. 1,2-Shift of metal carbonyl group concerted with the α-elimination of chloride anion is proposed as the transformation pathway of carbenoid A into CF₂CFM. A competing process of carbene insertion into Fe-CO bond is proposed to explain the formation of (XI). The feasibility of these two pathways is confirmed by DFT (B3LYP/SDD and 6-31G^∗) calculations of the carbenes [MCF₂CF:] and carbenoid anions [MCF₂CFCl]⁻. Transition states (TS) for 1,2-shift (+3.2 kcal/mol) and for nucleophilic addition at CO ligand (+5.4 kcal/mol) are located for [(CO)₅ReCF₂CFCl]⁻, but only one TS corresponding to carbene insertion into Fe-CO bond (+2.1 kcal/mol) is located for [(CO)₂CpFeCF₂CFCl]⁻. The formation of other newly observed products, F(CO)CHFRe(CO)₅ (V) and Cp(CO)₂FeCCFeCp(CO)₂ (VIII) is also discussed.     

Synthesis, characterization, and substituent effects of mononuclear ruthenium complexes [RuCl(CO)(PMe3)3(CHCH-C6H4-R-p)] (R = H, CH3, OCH3, NO2, NH2, NMe2)

A series of mononuclear ruthenium complexes [RuCl(CO)(PMe₃)₃(CHCH-C₆H₄-R-p)] (R = H (2a), CH₃ (2b), OCH₃ (2c), NO₂ (2d), NH₂ (2e), NMe₂ (2f)) has been prepared. The respective products have been characterized by elemental analyses, NMR spectrometry, and UV-Vis spectrophotometry. The structures of complexes 2c and 2d have been established by X-ray crystallography. Electrochemical studies have revealed that electron-releasing substituents facilitate monometallic ruthenium complex oxidation, and the substituent parameter values (σ) show a strong linear correlation with the anodic half-wave or oxidation peak potentials of the complexes.     

Oxime-substituted NCN-pincer palladium and platinum halide polymers through non-covalent hydrogen bonding (NCN = [C6H2(CH2NMe2)2-2,6])

The oxime-substituted NCN-pincer molecules HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 (2a) and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (2b) were accessible by treatment of the benzaldehydes H(O)C-4-C₆H₃(CH₂NMe₂)₂-3,5 (1a) and H(O)C-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (1b) with an excess of hydroxylamine. In the solid state both compounds are forming polymers with intermolecular O-H?N connectivities between the Me₂NCH₂ substituents and the oxime entity of further molecules of 2a and 2b, respectively. Characteristic for 2a and 2b is a helically arrangement involving a crystallographic 2₁ screw axis of the HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 building blocks.The reaction of 2b with equimolar amounts of [Pd₂(dba)₃ · CHCl₃] (3) (dba = dibenzylidene acetone) or [Pt(tol)₂(SEt₂)]₂ (4) (tol = 4-tolyl) gave by an oxidative addition of the C-Br unit to M coordination polymers with a [(HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6)MBr] repeating unit (5: M = Pd, 6: M = Pt). Complexes 5 and 6 are in the solid state linear hydrogen-bridged polymers with O-H?Br contacts between the oxime entities and the metal-bonded bromide.     

Tertiary phosphine abstraction from a platinum(II) coordination complex with SeCN: Crystal and molecular structures of SePTA and [SePTA-Me]I · CH3OH

Reacting [PtCl(PTA)₃]Cl(PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1^3,7]decane) with KSeCN in aqueous or MeOH medium results in the abstraction of the PTA ligands to yield SePTA. The reaction also proceeds quantitatively by direct reaction of PTA and KSeCN in water or methanol. The methylated PTA ligand, [PTA-Me]I (1-methyl-1-azonia-3,5-diaza-7-phosphatricyclo[3.3.1.1^3,7]decane iodide), reacts accordingly with KSeCN, albeit significantly slower. The crystal structure of SePTA, 1, and [SePTA-Me]I · CH₃OH, 2, revealed PSe bond distances of 2.0991(19) and 2.100(2) Å, respectively. The first order phosphorous selenium coupling constants, ¹J_P-Se (D₂O), of 722 and 788 Hz for SePTA and [SePTA-Me]I, respectively, indicates the latter is significantly less electron rich.     

Reaction of multifunctional molecule (Ph2P(o-C6H4)CHNCH2CH2)3N with triosmium carbonyl clusters

Reaction of (Ph₂P(o-C₆H₄)CHNCH₂CH₂)₃N with 3 equiv. of Os₃(CO)₁₀(NCMe)₂ at ambient temperature affords the triple cluster [Os₃(CO)₁₀Ph₂P(o-C₆H₄)CHNCH₂CH₂]₃N (1) through coordination of the phosphine and imine groups. Thermolysis of 1 in benzene leads to decarbonylation and C-H/C-N bond activation of the ligand to generate (μ-H)Os₃(CO)₈(μ₃-Ph₂P(o-C₆H₄)CHNCCH₂) (2). The molecular structure of 2 has been determined by an X-ray diffraction study.