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A rhodium(I) dicarbonyl on HY zeolite prepared from [Rh(CH 3 COCHCOCH 3 )(CO) 2 ] were charaterised by Attenuated Total Reflectance Fourier Transformed Infrared (ATR FTIR) and X-ray Photoelectron Spectroscopy (XPS). The ATR FTIR spectra of the anchored rhodium complex showed that [Rh(CH 3 COCHCOCH 3 )(CO) 2 ] reacted with the HY zeolite by loosing the [CH 3 COCHCOCH 3 ] − ligand to form Rh(CO) 2 /HY zeolite and [CH 3 COCHCOCH 3 ]/HY zeolite. The sharpness of the v (CO) bands measured by the ATR FTIR showed that the rhodium(I) dicarbonyl complex are distributed fairly uniform over the zeolite support. This heterogeneous catalyst was monitored for the oxidative addition of methyl iodide in the liquid phase, followed by reductive elimination of acetyl iodide upon treatment with CO gas. These reactions were monitored by following the carbonyl stretching frequencies from ATR FTIR measurements and the change in binding energy of the Rh 3d 5/2 photoelectron line as measured by XPS, observed rate constants determined were mutually consistent with each other. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of a series of rhodium(I) complexes of the type [Rh(CH 3 COCHCOCH 3 )CO(Ph 2 POPh- p -R)], where R = H ( 1 ), CH 3 ( 2 ), t Bu( 3 ) and Cl( 4 )] revealed an irreversible oxidation of Rh(I) to Rh(III), an irreversible oxidation of the phosphorus atom followed by the decomposition of the phosphinite ligand. An unexpected reaction occurred between the electrochemical internal standard, free ferrocene, in its ferricinium ion form and the radical cation of the oxidised diphenyl phosphinite, leading to uncharacteristic electrochemical behaviour. Electronic communication between different molecular fragment was confirmed by the linear relationships obtained between the Gordy group electronegativities of the R-groups on the phosphinites ( χ R ) and the E pa of Rh and the phosphorus atoms as well as the binding energy (eV) (measured by XPS) of the Rh 3d and P 2p peak positions. V-shape correlations were found between the Hammett constants of the R-groups on the phosphinites ( χ R ) and the oxidation potentials and binding energies. This shows the difference in stabilisation either resonance or inductive between the electrondonating and electronwithdrawing substituents. [ABSTRACT FROM AUTHOR]

[Display omitted] Three different classes of ferrocenyl-containing β-keto compounds Fc-CO-CH 2 -CO-R were synthesised to obtain two β-diketones with R = CH 3, 3 , and R = Fc (ferrocenyl = FeII(C 5 H 5)(C 5 H 4)), 4 , a β-ketoester, 5 , with R = OEt and a β-ketoamide, 6 , with R = NH 2. The β-diketones exhibited keto ⇌ enol tautomerization with the enol form Fc-CO-CH=C(OH)-R as the dominant isomer. Both the β-ketoester and β-ketoamide primarily existed in the keto form. FTIR and 1H NMR measurements could distinguish between keto and enol isomers. Dilute CHCl 3 solutions of 3 and 4 exhibited FTIR ѵ C=O keto vibrations between 1627 and 1712 cm−1 and ѵ C=O enol vibrations between 1590 and 1660 cm−1. X-ray photoelectron spectroscopic (XPS) measurements showed keto isomer Fe 2p 3/2 photoelectron lines at smaller binding energies than enol isomers. Significantly lower calculated molecular energies of the keto form of the β-ketoester 5 and β-ketoamide 6 utilising the Gaussian09 suite of programs at the B3LYP (uB3LYP for open-shell species), confirmed that 5 and 6 almost exclusively exists in the keto conformation. Cyclic voltammetry also distinguished between keto and enol isomers, and it was found that the electrochemical reversible ferrocenyl formal oxidation potential, E °ꞌ, of keto isomers of compounds can be estimated with the equation E °ꞌ keto = 170.99χ R –57.57 where χ R is the group electronegativities of R in FcCOCH 2 COR. This result complements earlier research that enables calculation of the ferrocenyl formal oxidation potentials of enol isomers of β-diketones. Computational studies further showed that the HOMO orbitals of 3 – 6 is exclusively on the Fe centre and computed Mulliken spin densities on the d xy orbital of the oxidised iron species approached 1 e−. [ABSTRACT FROM AUTHOR]

The electrochemical analysis, theoretical examination, as well as the first X-ray photoelectron spectroscopic (XPS) study on molybdenum(0) Fischer carbene complexes are presented. The intramolecular communication between the carbene ligand, molybdenum metal centre, and the ancillary ligands is illustrated by linear relationships and trends obtained between experimentally measured redox and XPS binding energy values and theoretically calculated energies and charges. The ease of oxidation of the three series of Mo(0) Fischer carbene complexes presented, namely four pentacarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 5 MoC(OEt)(Ar)], with Ar = 2-thienyl ( 1 ), 2-furyl ( 2 ), 2-(N-methyl)pyrrolyl ( 3 ), 2,2'-bithienyl ( 4 ), four triphenylphosphine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 4 (PPh 3 )MoC(OEt)(Ar)], with Ar = 2-thienyl ( 5 ), 2-furyl ( 6 ), 2-(N-methyl)pyrrolyl ( 7 ), 2,2'-bithienyl ( 8 ), and four triphenylarsine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 4 (AsPh 3 )MoC(OEt)(Ar)], with Ar = 2-thienyl ( 9 ), 2-furyl ( 10 ), 2-(N-methyl)pyrrolyl ( 11 ), 2,2'-bithienyl ( 12 ), all showed the same trend, namely (most difficult to oxidize at a higher potential): 2-thienyl ≈ 2,2'-bithienyl > 2-furyl > 2-(N-methyl)pyrrolyl. The pentacarbonyl complexes [(CO) 5 MoC(OEt)(Ar)] have the highest oxidation potentials, followed by the oxidation potential of [(CO) 4 (PPh 3 )MoC(OEt)(Ar)], while [(CO) 4 (AsPh 3 )MoC(OEt)(Ar)] oxidized at a potential 0.12 − 0.15 V lower than the PPh 3 substituted complexes [(CO) 4 (PPh 3 )MoC(OEt)(Ar)]. Substitution of carbonyl ligand(s) in the pentacarbonyl complexes 1 – 4 , by one (complexes 5 – 12 ) or two ([(dppe)(CO) 3 MoC(OEt)(2-furyl)] complex ( 13 ), dppe = 1,2-bis(diphenylphosphino)ethane) weaker π-acceptor ligands (phosphines/arsines) in Fischer carbene complexes leads to a decrease in the binding energy of the Mo 3d 5/2 photoelectron lines of the X-ray photoelectron spectra of the Fischer carbene complexes and an increase in the binding energy of the carbene carbon C 1 s photoelectron lines. [ABSTRACT FROM AUTHOR]

Abstract: A comparative investigation of seven ferrocene-containing chalcones (Fc–CO–CH;C6H4R, with R=OCH3, CH3, Ph, t Bu, H, Br and CF3) has been performed based on their electrochemical and spectroscopical behavior as well as with DFT calculations. These compounds were prepared by Claisen-Schmidt condensation of acetylferrocene and the appropriate benzaldehyde derivative. All compounds exhibited reversible chemical and electrochemical behavior, as confirmed by ΔE =83−93mV and i pc/i pa =0.93−1.00. The formal reduction potential E°′ for the compounds ranged between 231.0 and 261.5mV versus FcH/FcH+ as an internal standard. The UV–Vis spectra of all ferrocene-containing chalcones showed the characteristic peaks for aromatic systems at ±380nm and a peak in the visible region at ±490nm, which is attributed to the ferrocene moiety. FTIR of all the ferrocene-containing chalcones showed a characteristic CO stretching peak at ±1650cm−1. DFT calculated HOMO energies and ionization potentials correlate well with experimentally measured E°′ values. [Copyright &y& Elsevier]

In methanol solutions, [Rh(FcCOCHCOR)(CO)(PPh 3)] and [Rh(FcCOCHCOR)(CO) 2 ] complexes do not undergo substitution or oxidative addition by MeOH. In contrast, when the same compounds are spin-coated on (OH)-capped silicon wafers, XPS measurements showed that, in the solid state, both ligand substitution and oxidative addition by Si-OH functionalities occur. Rh XPS binding energies are linearly related to RhI oxidation potentials and group electronegativities of the R-groups (CF 3 , CH 3 , phenyl and ferrocenyl). [Display omitted] A series of rhodium β-diketonato complexes [Rh(FcCOCHCOR)(CO) 2 ] and [Rh(FcCOCHCOR)(CO)(PPh 3)] with R = CF 3 , CH 3 , Ph = C 6 H 5 and Fc (ferrocenyl = FeII(C 5 H 5)(C 5 H 4)) were spin-coated on two-dimensional silanol-functionalised silicon wafers. Chemical reactions were observed that do not occur in ethanol solutions. Si-OH fragments on the wafers substituted ligands and oxidatively added to the Rh(I) centres. A multitude of different surface species could be identified with X-ray photoelectron spectroscopy (XPS). These included the parent spin-coated rhodium(I) complexes and rhodium(I) species that resulted from β-diketonato displacement from parent rhodium complexes by surface silanol OH's to generate [wafer-(O) 2 -Rh-(CO) 2 ]⊝ and [wafer-(O) 2 -Rh-(CO)(PPh 3)]⊝ units. Several RhIII surface species that inter alia resulted from oxidative addition of surface Si-OH groups to surface-coordinated RhI core atoms were also identified. Efficacy of β-diketonato ligand substitution by the silanol surfaces is a kinetically driven process and can be related to the rate of solution-phase β-diketonato substitution by 1,10-phenanthroline from parent [Rh(FcCOCHCOR)(CO) 2 ] and [Rh(FcCOCHCOR)(CO)(PPh 3)] complexes. The binding energies of the RhI and RhIII 3 d 5/2 photoelectron lines were found to be functions of Gordy scale R-group electronegativities and they are also linearly related to electrochemically determined RhI oxidation potentials. [ABSTRACT FROM AUTHOR]

Graphical abstract The electrochemical behavior of the Fc/Fc+ of ferrocenyl-terpyridine coordination metal complexes is related to the charge transfer and binding energy of the Fe 2p photoelectron lines as measured by XPS, giving insight into the electronic properties of the complexes. Highlights • Preparation of coordinated ferrocenyl-terpyridine complexes. • Electrochemical study of the coordinated ferrocenyl-terpyridine complexes. • X-ray photoelectron spectroscopy of ferrocenyl-terpyridine coordination complexes. • The intensity of satellite structures in XPS indicated the amount of charge transferred. • Single crystal structure of [Rh(Fctpy) 2 ][PF 6 ] 3. Abstract A series of 4′-ferrocenyl-2,2′:6′,2′'-terpyridine coordination metal complexes, [M(Fctpy) 2 ][PF 6 ] x with M = Co (2), Fe (3), and Rh (4) and x = 2 (for 2 and 3) or 3 (for 4), was subjected to an electrochemical and X-ray photoelectron spectroscopic study. The formal reduction potential of the Fc/Fc+ couple of the ferrocenyl-moiety (FeII) is related to the Allred Rochow electronegativities of the different coordinated metals, as well as with binding energies of the Fe 2p 3/2 photoelectron lines (as measured by XPS). The binding energy position of the main Fe 2p 3/2 photoelectron line, spin–orbit splitting between the main and satellite structure (charge transfer band) of the Fe 2p 3/2 photoelectron line as well as the intensity ratio between the of the main and satellite structure of the Fe 2p 3/2 photoelectron line (I ratio , this gives the relative amount of charge being transferred) gave insight in the electronic structure of these ferrocenyl-terpyridine coordination metal complexes, 2 – 4. A single crystal X-ray structure determination of 4 highlighted the disorder of the PF 6 counter anions as well as double occupancy of the central metal atom of Rh (in 4) with Fe, the Fe:Rh ratio is 0.14:0.85. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of the first triphenylstibine-containing Fischer carbene complexes of Mo(0) with general formula [(SbPh 3 )(CO) 4 MoC(OEt)(Ar)] with Ar = 2-thienyl ( 1 ), 2-furyl ( 2 ), 2-(N-methyl)pyrrolyl ( 3 ), and 2,2′-bithienyl ( 4 ) are reported. The solid state crystal structures of these complexes show a syn conformation of the 2-thienyl and 2,2′-bithienyl groups relative to the ethoxy group, and an anti conformation of the 2-furyl group relative to the ethoxy group. Density functional theory calculations using natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations gave insight into the electronic structure and preferred conformations of these novel complexes. X-ray photoelectron spectroscopy measurements show that the binding energy of the Mo 3d 5/2 photoelectron line for the 2-(N-methyl)pyrrolyl-containing Fischer carbene complex, 3 , is the smallest; followed by 2 and then 1 . This implies that the Mo metal centre is more electron rich in 3 , relative to the 2-furyl or 2-thienyl containing Fischer carbene complexes, 2 and 1 , respectively. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of triphenylstibine-containing Fischer carbene complexes of Mo(0) of the type [(SbPh 3 )(CO) 4 MoC(OEt)(Ar)] with Ar = 2-thienyl ( 1 ), 2-furyl ( 2 ), 2-(N-methyl)pyrrolyl ( 3 ) or 2,2'-bithienyl ( 4 ) is reported. Results are compared to the related complexes [(L,L')(CO) 3 MoC(OEt)(Ar)] where L,L' = CO,CO; PPh 3 ,CO; AsPh 3 ,CO; or dppe (1,2-bis(diphenylphosphino)ethane). Linear trends and relationships obtained between HOMO/LUMO energies, oxidation/reduction potentials, ionization energies/electron affinities and X-ray photoelectron spectroscopic binding energies of the Mo 3d 5/2 photoelectron lines, show that the electronic influences of the heteroaryl carbene substituent and pnictogen ligands in Mo(0) Fischer ethoxycarbene complexes are transmitted well through the bonds to the Mo metal centre. [ABSTRACT FROM AUTHOR]

It is illustrated that the electrochemical redox potentials of chromium(0) Fischer carbene complexes containing a heteroaromatic substituent can be determined to a high degree of accuracy from the gas phase density functional theory (DFT) optimized frontier orbital energies, with a mean average error of the calculated redox potentials of 0.047 V for the chromium-based oxidation potential and 0.057 V for the carbene ligand based reduction potential. For the first time it was possible to distinguish between the Cr 0/I oxidation peaks of the E and the Z -isomer of a cyclohexylamino pentacarbonyl chromium Fischer carbene complex, namely [(CO) 5 CrC(NHCy)(2-thienyl)]. The linear relationship obtained between the oxidation potential and the DFT calculated highest molecular orbital energies, made it possible to assign the oxidation peak at the lower less positive oxidation potential to the oxidation of the E isomer, and the peak at the slightly higher (more positive) oxidation potential to the oxidation of the Z isomer of [(CO) 5 CrC(NHCy)(2-thienyl)]. [ABSTRACT FROM AUTHOR]

Surface-hydroxylated silicon wafers, 8, were reacted with 3-aminopropyltrimethoxysilane, 9, to create wafers with amine-functionalized surfaces, 10. The metallocenylaldehydes FcCHO, 1 (Fc = ferrocenyl = FeII(C5H5)(C5H4)), RcCHO, 2 (Rc = ruthenocenyl = RuII(C5H5)(C5H4)), and OcCHO, 3 (Oc = osmocenyl = OsII(C5H5)(C5H4)) as well as the carboxylic acids FcCOOH, 4, RcCOOH, 5, OcCOOH, 6, and Cc+COOH·PF6 −, 7 (Cc+ = cationic cobaltocenium = [CoIII(C5H5)(C5H4)]+), were reacted with 10 to covalently anchor the metallocenes on the wafers either via an imine (–CH N–) or amide (–NHCO–) bond. The aldehydes were anchored more effectively than the carboxylic acids. Binding energies of all important atoms in all seven systems were determined by XPS measurements. Metal binding energies of the amide-bonded metallocenes were consistently larger (up to 0.6 eV) than those of the imine-anchored systems. AFM and SEM measurements showed that the covalently anchored metallocenes aggregate into nano-islets of diameter between 40 and 100 nm depending on the metallocene and type of anchoring bond. Up to seven additional layers of unreacted metallocenylaldehyde or -acid further stacked on top of the main layer of metallocene to form each islet. These additional layers of metallocene of each islet are stabilized by a large network of secondary and/or tertiary bonding forces. The main film surfaces have average thicknesses ranging between 2 and 6 nm, while film roughness, which is mostly associated with the islets, was with one exception (that of the Oc–CONH– surface 14) between 17% and 68% of the film thickness. The crystal structures for OcCHO, 3, and Cc+COOH·PF6 −, 7, was determined and the observed tertiary and secondary intermolecular interactions between independent molecules explains the formation of the nano-islets of each metallocene when anchored onto the aminated silicon wafers. [ABSTRACT FROM AUTHOR]