Reactions of Fischer alkoxycarbene complexes[W(CO) 5 {C(OEt)Ar}], Ar = thienyl (1) or furyl (2), with ethylene diamine lead to the formation of two different reaction products: an aminolysis product (5 or 6) where the ethoxy substituent of the carbene ligand is replaced by the ethylene diamine moiety, as well as a chelated product where aminolysis and substitution of one carbonyl ligand had taken place, yielding 7 or 8. Aminolysis of 1 and 2 with cyclohexyl amine (CHA) produced the aminocarbene complexes 3 (Ar = thienyl) and 4 (Ar = furyl). Complexes 1-8 are electrochemically investigated by means of cyclic voltammetry. The relative shifts in the oxidation and reduction potentials are discussed and related to density functional theory (DFT) calculated energies. DFT calculations further show that the oxidation center is located on the metal and the carbonyl groups, while the reduction center is localized on the carbene moiety and is strongly influenced by the electronic properties of its substituents. Crystal structures of 1-4, 6 and 8 are reported.

Abstract:A series of ferrocenyl-functionalized β-diketonato manganese(III) complexes, [Mn(FcCOCHCOR) 3 ] with R = CF 3 , CH 3 , Ph (phenyl) and Fc (ferrocenyl) was subjected to a systematic XPS study of the Mn 2p 3/2 and Fe 2p 3/2 core-level photoelectron lines and their satellite structures. A charge-transfer process from the β-diketonato ligand to the Mn(III) metal center is responsible for the prominent shake-up satellite peaks of the Mn 2p photoelectron lines and the shake-down satellite peaks of the Fe 2p photoelectron lines. Multiplet splitting simulations of the photoelectron lines of the Mn(III) center of [Mn(FcCOCHCOR) 3 ] resemble the calculated Mn 2p 3/2 envelope of Mn 3+ ions well, indicating the Mn(III) centers are in the high spin state. XPS spectra of complexes with unsymmetrical β-diketonato ligands (i.e., R not Fc) were described with two sets of multiplet splitting peaks representing fac and the more stable mer isomers respectively. Stronger electron-donating ligands stabilize fac more than mer isomers. The sum of group electronegativities, Σχ R , of the β-diketonato pendant side groups influences the binding energies of the multiplet splitting and charge transfer peaks in both Mn and Fe 2p 3/2 photoelectron lines, the ratio of satellite to main peak intensities, and the degree of covalence of the Mn-O bond.

and 2d with 1. A single crystal X-ray structure determination of 3b (Z=2, triclinic, space group P-1) highlighted a weak axial elongating Jahn-Teller effect and a high degree of bond conjugation.An X-ray photoelectron spectroscopic study, by virtue of linear relationships between group electronegativities of ligand R groups, χ R , or χ R , and binding energies of both the Fe 2p 3/2 and Mn 2p 3/2 photoelectron lines, confirmed communication between molecular fragments of 2a-2d as well as 3a-3d. This unprecedented observation allows prediction of binding energies from known β-diketonato side group χ R values.Keywords: Manganese, ferrocene, betadiketonato complexes, substituent effects, electronic spectra, X-ray photoelectron spectroscopy, binding energy predictions. IntroductionThe first row transition metal, manganese, exhibits a wide variety of oxidation states in compounds ranging from Mn(I), e. we then highlight intramolecular communication between molecular fragments of 3a-3d from results of an X-ray photoelectron spectroscopic (XPS) study. Results and discussion Synthesis and characterizationThe ferrocene-containing manganese ( IR spectra of 3a-3d and 4 displayed the characteristic strong ν CO vibrations found between 1498-1572 cm -1 (Experimental Part) which is typical for chelate-bonded β-diketonato ligands in transition metal chemistry. 22 A shift to lower wave numbers is observed for 3a-3d and 4 compared to the free β-diketones 2a-2d (1620 -1710 cm -1 ) 23 which allows the monitoring of the reaction progress. Prominent CH-stretching bands are also observed at ca. 3100 cm -1 .Peak maxima of the UV-Vis spectra of complexes 3a-3d and 4 ( Figure 1) are summarized in Table 1. Dichloromethane solutions of the highly soluble complexes 3a-3c and 4 all showed relatively high extinction coefficients. All complexes followed the Beer-Lambert law, A = εCl, which implies a linear relationship between absorbance and concentration. Van der Zeiden 24 reported a similar lower energy band in tungsten(0) -diketonato complexes and assigned it to a MLCT band with destabilized t 2g level after appropriate calculations. Single Crystal X-ray structure of 3bTo understand the trends observed in XPS-obtained binding energies for Fe(II) (and also Mn(III)) of complexes 3a -3d described in the next section, an evaluation of the structural characteristics of 3b is useful. The fac isomer of complex 3b crystallized from toluene in the triclinic space group P-1 having ca. 1 disordered solvent molecule for every two molecules of 3b. The refinement parameters and crystal data are summarized in Table 2 and the molecular structure of 3b, highlighting atom labeling, are shown in Figure 2. Selected bond distances and bond angles are summarized in the caption of Figure 2, but the full set of bond lengths and angles is available in Supplementary Information.

The series of zirconium(IV) and hafnium(IV) phthalocyanine complexes [PcM(FcCOCHCOR)2] (Pc = phthalocyaninato; M = Zr; R = CF3 (1), CH3 (2), C6H5 (3), Fc ((C5H5)Fe(C5H4), 4), as well as M = Hf ; R = CF3 (5), CH3 (6), C6H5 (7), and Fc (8)) were synthesized. A single-crystal X-ray diffraction analysis of the structure of [PcHf(FcCOCHCOC6H5)2], 7 (Z = 2, space group P1), showed the two axial β-diketonato ligands were orientated in such a way that the ferrocenyl groups were positioned diagonally opposite each other. From the structural determination of 7 it was clear that these complexes have a distorted D4h symmetry at the coordination site of the metal centers, which explains a splitting of the UV-vis Q band into Qx and Qy components with 3 ≤ Δλ(max,Q) ≤ 10 nm. Cyclic and square wave voltammetric studies in CH2Cl2/[N((n)Bu)4][B(C6F5)4] allowed observation of at least three phthalocyaninato macrocycle-based redox couples as well as all (i.e., two or four) well-resolved ferrocenyl couples in 1-8. For M = Zr and R = Fc, formal reduction potentials of the four ferrocenyl groups were found to be E°' = 296, 386, 538, and 687 mV versus free ferrocene. Spectroelectrochemical evidence, UV-vis Q-band maximum wavelengths, and HOMO-LUMO energy gaps as expressed by ΔE°'I-III = ΔE°'wave I - ΔE°'wave III were mutually consistent, indicating that the first phthalocyaninato ring-based oxidation occurs before ferrocenyl oxidations take place. The potential for each redox process was found to be dependent on the sum of β-diketonato R-group group electronegativities, ΣχR. Mathematical relationships for the dependency of E°' on ΣχR for all four observed ring-based redox processes as well as for the ferrocenyl-based redox processes were determined. This allowed prediction of potentials for redox processes that fall outside the workable potential window of the solvent. No significant differences were found between the corresponding redox potentials of zirconium and hafnium analogues bearing the same axial ligands.

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