Hauke Reddmann

Zur Elektronenstruktur metallorganischer verbindungen der f-Elemente: XXXIV. Ist der N,N′-bis(trimethylsilyl)benzamidinato-Ligand im Falle von Lanthanoid-Zentralionen ein elektronisches Äquivalent zum η5-Cyclopentadienyl-Liganden?☆

Abstract Magnetic data and the results of low temperature absorption, luminescence and magnetic circular dichroism spectra of 4-methoxy-substituted lanthanide ( III )tris[ N , N ′-bis(trimethylsily)benzamidinates [(MeOBA) 3 Ln; Ln  Eu ( 1 ), Pr ( 2 )], and of adducts derived from tris(η 5 -cyclopentadienyl)-europium( III ) [CP 3 EuX; X  CNC 6 H 11 ( 3 ), THF ( 4 )] are reported. In case of 1 , 3 and 4 the 151 Eu Mossbauer spectra also were recorded. On the basis of the optical measurements the truncated crystal field (CF) splitting patterns of 1 and 2 were derived. The parameters of an empirical Hamiltonian were fitted to the experimentally derived splitting patterns. The parameters obtained suggest that the BA ligand may be considered to a certain extent as an electronic equivalent to the Cp ligand in case of Ln central ions with small electron affinity. In case of central ions with higher oxidation power such as Eu 3+ , the BA ligand behaves in a conventional manner. The Cp ligand, however, causes unusual physical properties which cannot be explained on the basis of an Eu 3+ , central ion which is surrounded by three Cp ligands.

Zur elektronenstruktur metallorganischer komplexe der f-elemente: XXX. Kristall- und molekülstrukturen ungewöhnlich gut kristallisierender addukte des grundkörpers tris(η5-cyclopentadienyl)-lanthanoid(III)

Abstract The crystallizing properties of approximately 150 adducts derived from tris(η5-cyclopentadienyl) lanthanide(III) (Cp3Ln) and Cp′ 3Ln (Cp′  C5H5R; R  methyl, ethyl, t-butyl, benzyl, phenyl, trimethylsilyl) have been examined. Transparent single crystals which crystallize in the shape of distorted hexagonal plates of cross sections up to 200 mm2 could be grown for the n-butylacetate (BA) adduct of the early members of the Cp3Ln series and for the acetonitrile adducts for Cp3Gd and Cp3Tb. The crystal and molecular structures of Cp3Pr·BA(1) and Cp3Tb·NCCH3 (2) were determined. 1 crystallizes in the molecular space group P21 /n with four molecules in the unit cell, and 2 in the triclinic space group P1(Z = 2). The monoclinic angle β = 91.58° of 1 is close to the right angle of the rhombic system and the pseudo threefold axes of the individual molecules make angles of |14.97°| and |1 75.03°|, respectively, with the monoclinic b axis. For practical purposes 1 may be considered as being rhombic with the molecules aligned along the b axis. Thus, the individual molecules may be easily oriented with respect to a static magnetic field or the electric field vector of linearly polarized radiation. The α absorption spectrum of the spin allowed transitions of 1 is presented and some peculiarities are discussed.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente. XXXV: Absorptions- und lumineszenzspektroskopische Charakterisierung von optisch verdünntem Cp3Sm(NCCH3)2

Abstract Cp3Sm(NCCH3)2, hitherto unknown in neat form, has been chemically stabilized by doping a Cp3La(NCCH3)2 matrix with Cp3Sm(NCCH3)2.The absorption spectra of Cp3La0.8Sm0.2(NCCH3)2 (1), Cp3La(NCCH3)2 (2) and Cp3SmNCCH3 (3) have been measured using liquid He, and the luminescence spectra of 1 and 3 using liquid N2 as coolants. From these data the truncated crystal field (CF) splitting patterns of 1 and 3 were derived. The parameters of an empirical Hamiltonian were fitted to the energies of 42 and 57 levels respectively, to give r.m.s. deviations of 20 cm−1 and 31 cm−1 for 1 and 3.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente: XXIX. Optische und magnetochemische untersuchungen an Mono- und Bis-Acetonitriladdukten des Grundkörpers Tris(η5-cyclopentadienyl)praseodym(III)

Abstract The results of absorption, emission and magnetochemical measurements for mono and bisacetonitrile adducts derived from tris(η5-cyclopentadienyl)praseodmium(III) are reported. On the basis of these measurements the truncated crystal field splitting pattern of Cp3Pr·NCCH3 could be derived. The absorption and luminescence spectra of Cp3Pr(NCCH3)2 however, lead to two different splitting patterns. The parameters of an empirical Hamiltonian were fitted to the experimentally derived splitting patterns. In order to favour one of the two alternative parameter sets for Cp3Pr(NCCH3)2;, model calculations adopting the angular overlap model have been performed. Additionally, from the eigenvectors and eigenvalues obtained from the alternative fits, the temperature dependence of the paramagnetic susceptibility was calculated and compared with experimental data.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente: XXVII. Interpreation der optischen, magnetochemischen, ESR-und NMR-spektroskopischen Eigenschaften ausgewählter Neutralbasenaddukte, die sich vom Grundkörper Tris (n5-cyclopentadienyl)-neodym(III) ableiten

Abstract The absorption spectrum of (Cp- d 5 ) 3 Nd·THF- d 8 in hydrocarbon glasses and run as pellets was measured at room and low temperatures. The bands were assigned based on calculations assuming the crystal field parameters of the Nd complex were the same as for the previously analyzed Cp 3 Pr·MeTHF. The parameters of an empirical Hamiltonian wee fitted to the energies of 96 levels to give an r.m.s. deviation of 26 cm −1 . On the basis of the wave functions of the crystal field ground state obtained from these calculations, the observed EPR spectrum of Cp 3 Nd 0.06 La 0.94 ·THF could be explained. Making use of the calculated wave functions and eigenvalues the experimentally determined temperature dependence of μ 2 eff of powdered Cp 3 Nd·THF and of an oriented single crystal of Cp 3 Nd·Ncch 3 could be simulated. Assuming that the methyl protons of the γ-picoline ligand of Cp 3 Nd·γ-pic and (MeCp) 3 Nd· γ-pic, respectively, experience only an NMR shift of dipolar type, the paramagnetic anisotropy χ ∥ -χ ⊥ was estimated.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente ☆: LI. Synthese, Kristall-, Molekül- und Elektronenstruktur von Cp3Nd(NCCH3)2

Cp 3 Nd(NCCH 3 ) 2 ( 1 ) crystallizes in the orthorhombic space group Pbcn with a =13.961(2) A, b =8.484(2) A, c =14.840(2) A, Z =4, R =0.0359, R w =0.0408 for 1191 data and I >3 σ ( I ). Like in the case of the La, Ce and Pr derivatives the Nd 3+ central ion of compound 1 is pseudo trigonal bipyramidally coordinated by three η 5 -bonded Cp rings in the equatorial plane (Nd–ring centre distances 2.561 A, 2.554 A) and two acetonitrile groups in the axial positions (Nd–N=2.764(5) A). The absorption spectra of extremely sensitive 1 (pellets), the much more stable optically diluted Cp 3 La 0.8 Nd 0.2 (NCCH 3 ) 2 ( 2 ) (Single crystals), Cp 3 La(NCCH 3 ) 2 ( 3 ) (Single crystals) and Cp 3 Nd·NCCH 3 ( 4 ) (pellets) were recorded at room and low temperatures. From the spectra obtained, truncated crystal field splitting patterns of complexes 2 and 4 were derived, and simulated by fitting the parameters of an empirical Hamiltonian. For 56 and 55 assignments, respectively, reduced r.m.s. deviations of 32.3 cm −1 and 20.9 cm −1 are achieved for 2 and 4 . From the parameters used the experimentally based non-relativistic and relativistic molecular orbital schemes in the f range are set up for 2 and 4 . On the basis of the calculated wavefunctions and eigenvalues obtained from the fits, the spectroscopic splitting factors (extracted from the EPR spectrum) of 2 and the temperature dependence of μ eff 2 of 1 and 4 can be explained. The existence of Cp 3 La(NCCH 3 ) 2 :Tb 3+ ( 5 ) is proved by the luminescence spectrum of this complex.

Parametric Analysis of the Crystal Field Splitting Pattern of Sm(η5-C5Me5)3 Derived on the Basis of Absorption Spectra of Pellets or Solutions and Electronic Raman Spectra of Oriented Single Crystals†

By comparing the absorption spectrum of pseudo trigonal planar Sm(eta(5)-C(5)Me(5))(3) (1) (KBr pellet, methylcyclohexane solution) with the previously assigned one of Sm(eta(5)-C(5)Me(4)H)(3) (2) a truncated experimental crystal field (CF) splitting pattern of the former compound could be derived in the NIR range. Because of its dark brown color, fluorescence is not observed from complex 1, and thus the CF splitting pattern in the low energy range could not be determined on the basis of luminescence measurements. However, comparing the FIR and MIR spectra (pellets) as well as the Raman spectra of oriented single crystals of 1 with those of La(eta(5)-C(5)Me(5))(3) (3) at least two additional CF levels could be detected. The free parameters of a phenomenological Hamiltonian were fitted to the thus extended CF splitting pattern of 1, leading to a reduced rms deviation of 15.0 cm(-1) for 21 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Sm(3+) central ion was estimated, and seems to be the third largest one ever encountered in Sm(III) chemistry. The obtained Slater parameter F(2) and the spin-orbit coupling parameter zeta(4f) allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of Sm(III) compounds. With its low F(2) value, complex 1 is the most covalent Sm(III) compound (considering only f electrons) found to date. The experimentally based non-relativistic molecular orbital scheme (in the f range) of complex 1 was set up and compared with the results of a previous Xalpha-SW calculation on the pseudo trigonal planar model compound Sm(eta(5)-C(5)H(5))(3). In the frame of the search for f-f and electronic Raman transitions, the vibrational spectra (FIR/MIR of pellets, Raman spectra of oriented single crystals) of compound 1 were recorded too, and partly assigned on the basis of the observed coincidences and polarizations.

Electronic Structures of Highly Symmetrical Compounds of f Elements. 34 [1] Synthesis and Spectroscopic Characterization of Biscyclohexylisocyanide Adducts derived from the Tris(bis(trimethylsilyl)amido)lanthanide(III) Moiety as well as Crystal, Molecular, and Electronic Structure of the Corresponding Neodymium Compound

The reaction of tris(bis(trimethylsilyl)amido)lanthanide(III) (Ln(btmsa)3) with two equiv. of cyclohexylisocyanide gives good yields of complexes of composition Ln(btmsa)3(CNC6H11)2 (Ln = Y(1), La(2), Ce(3), Pr(4), Nd(5), Sm(6), Eu(7), Tb(8), Dy(9), Ho(10), Tm(11) and Yb(12)). Complex 5 crystallizes in the monoclinic space group C2/c with a = 25.689(8) A, b = 12.165(2) A, c = 17.895(15) A, β = 122.47 (2)°, V = 4718.07 A3, Z = 4 and R = 0.0342. The structure of compound 5 shows the five-coordinate Nd3+ ion in a nearly exact trigonal bipyramidal environment with two CNC6H11 molecules in the axial and the three btmsa ligands in the equatorial positions. The linear dichroism spectrum of a single crystal of complex 5 was measured at room temperature, and the absorption spectrum of powdered material at low temperatures. From the spectra obtained a truncated crystal field (CF) splitting pattern is derived, and simulated by fitting the parameters of a phenomenological Hamiltonian. For 80 assignments a reduced r.m.s. deviation of 20.7 cm—1 is achieved. Making use of the calculated wavefunctions and eigenvalues the experimentally determined temperature dependence of μ2eff could be reproduced by adopting an orbital reduction factor k = 0.991, and on the basis of the CF parameters used the experimentally oriented non-relativistic molecular orbital scheme of compound 5 is set up. Zur Elektronenstruktur hochsymmetrischer Verbindungen der f-Elemente. 34 Synthese und spektroskopische Charakterisierung von Biscyclohexylisonitril-Addukten des Grundkorpers Tris(bis(trimethylsilyl)amido)lanthanid(III) sowie Kristall-, Molekul-und Elektronenstruktur der entsprechenden Neodym-Verbindung Die Reaktion von Tris(bis(trimethylsilyl)amido)lanthanid(III) (Ln(Btmsa)3) mit zwei Aquivalenten Cyclohexylisonitril ergibt in guter Ausbeute Komplexe der Zusammensetzung Ln(Btmsa)3(CNC6H11)2 (Ln = Y(1), La(2), Ce(3), Pr(4), Nd(5), Sm(6), Eu(7), Tb(8), Dy(9), Ho(10), Tm(11) und Yb(12)). Komplex 5 kristallisiert in der monoklinen Raumgruppe C2/c mit a = 25.689(8) A, b = 12.165(2) A, c = 17.895(15) A, β = 122.47 (2)°, V = 4718.07 A3, Z = 4 und R = 0.0342. In Verbindung 5 ist das Nd3+-Zentralion funffach in Form einer nahezu exakten trigonalen Bipyramide koordiniert, wobei die beiden CNC6H11-Molekule die axialen, und drei Btmsa-Liganden die aquatorialen Positionen besetzen Das lineare Dichroismus-Spektrum eines Einkristalls von Komplex 5 wurde bei Raumtemperatur und das Absorptionsspektrum von gepulvertem Material bei tiefer Temperatur vermessen. Den erhaltenen Spektren wurde ein nicht vollstandiges Kristallfeld(KF)-Aufspaltungsmuster entnommen und dieses durch Anpassung der offenen Parameter eines phanomenologischen Hamilton-Operators simuliert. Bei 80 Zuordnungen wurde eine reduzierte r.m.s.-Abweichung von 20.7 cm—1 erzielt. Unter Verwendung der berechneten Wellenfunktionen und Eigenwerte sowie eines Orbitalreduktionsfaktors k = 0.991 konnte die experimentell bestimmte Temperaturabhangigkeit von μ2eff reproduziert werden, und auf der Grundlage der erhaltenen KF-Parameter wurde das experimentell orientierte nicht-relativistische Molekulorbital-Schema der Verbindung 5 aufgestellt.

Zur Elektronenstruktur metallorganischer komplexe der f- Elemente Teil 37. die elektronenstruktur von Pr3+bei ψ- trigonal-bipyramidaler organischer koordination

Zusammenfassung Durch Dotierung einer Cp 3 La(NCCH 3 ) 2 -Matrix mit unterschiedlichen Mengen von Pr 3+ konnten relativ stabile Cp 3 La 1 − x Pr x (NCCH 3 ) 2 ( 1 ) ( x = 0,6; 0,3; 0,1)-Einkristalle gezuchtet werden. Auf der Grundlage absorptions- und lumineszenzspektroskopischer Untersuchungen sowie teilweise von Messungen des magnetischen Zirkulardichroismus wurden die Kristallfeld (KF)-Aufspaltungsmuster von 1 und (CH 3 OCH 2 CH 2 C 5 H 4 ) 3 Pr ( 2 ) abgeleitet. Die Parameter eines empirischen Hamilton-Operators wurden den KF-Aufspaltungsmustern von 1 und 2 angepaβt, wobei r.m.s.-Abweichungen von 27 cm −1 bzw. 24 cm −1 bei 25 bzw. 24 Zuordnungen erzielt wurden. Bei Verwendung der berechneten Wellenfunktionen und Eigenwerte konnte die Temperaturabhangigkeit der mittleren paramagnetischen Suszeptibilitat von Cp 3 Pr(NCCH 3 ) 2 sowie von 2 in ausgezeichneter Weise reproduziert werden.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente. XXXII: Absorptionsspektroskopische Charakterisierung von Cp3Nd(NCCH3)2

Abstract The absorption spectrum of a CP 3 Nd(NCCH 3 ) 2 single crystal has been measured using liquid N 2 as coolant. From these data a truncated crystal field splitting pattern could be derived. The parameters of an empirical Hamiltonian were fitted to the energies of 41 levels to give an r.m.s. deviation of 26 cm –1 .