R. Dieter Fischer

Preparation and characterization of the first triscyclopentadienyl lanthanoid complexes containing two aliphatic nitrile ligands: Crystal and molecular structures of the isomorphous compounds Trans-bis(acetonitrile)tris(η5cyclopentadienyl)lanthanoid(III) (Ln = La, Ce, Pr). A successful confirmation of the solid ‘solid angle sum rule’

Abstract Systematic studies to arrive at some first examples of the sterically congested complex type Cp3Ln(NCR)2 (Cp = η5-C5H5, Ln = lanthanoid element) resulted in the preparation and detailed spectroscopic characterization of analytically pure representatives of this type with Ln = La, Ce and Pr, but not with Nd (R = CH3, and C2H5 for Ln = La only). The crystal and molecular structures of representatives of the isomorphous series Cp3Ln(NCCH3)2, (Ln = La, Ce, Pr) were determined from three-dimensional X-ray diffraction data. The compounds crystallize in the orthorhombic space group Pnca (standard group Pbcn) with: a = 14.940(3), b = 14.074(3), c = 8.596(2)A, Z = 4, R = 0.070, Rw = 0.079 for 1633 intensity data (La derivative, I); a = 14.906(3), b = 13.974(3), c = 8.502(2)A, R = 0.041, Rw = 0.047 for 1378 intensity data (Ce derivative, VII); a = 14.936(3), b = 13.986(3), c = 8.498(2)A, R = 0.031 for 1372 intensity data (Pr derivative, IX). According to the X-ray crystallographic results, the novel complexes are trigonal bipyramidally coordinated with three η5-bonded Cp rings in the equatorial plane (Ln—ring centre distances 2.62, 2.64 for La, 2.58, 2.59Afor Ce and 2.57, 2.57Afor Pr and two acetonitrile groups in the axial positions (Ln N 2.785 for La, 2.749 for Ce, 2.752 for Pr). The range of the distances in the three derivatives is in agreement with the trend in the crystal radii along the lanthanoid series. Pure 1:2 adducts involving any alkyl group larger than R = C2H5 could not be isolated. The relative stabilities of the novel Cp3Ln(NCR)2 systems, with respect to the decreasing ionic radius (i.e. from La to Nd) and to the variable space demanded by the group R, are in excellent accord with independent expectations based on the recently developed cone packing model (‘SAS-rule’) for f-element organometallics.

The “solid angle sum rule”: A new ligand cone packing model of optimal applicability in organolanthanoid chemistry, part I

Abstract As a result of the systematic evaluation of about forty published molecular structures of organolanthanoid(III) complexes, the so-called “solid-angle-sum (SAS) rule” suggests that optimal coordinative saturation is verified for the comparatively small SAS value of 0.73. Here, 4π·SAS is the sum of the individual solid angles of all ligands surrounding one central metal ion (Ln3+). On the basis of empirical standard values of the “solid angle factors”, SAF = SA 4π , of various frequently occurring ligands, the SAS-rule allows reasonable predictions to be made of the relative stabilities of distinct members of numerous complex families, particularly as a function of the ionic radius of the respective central metal ion (including also La3+, Y3+ and Sc3+).

Koordinationsverhältnisse in basenfreien tricyclopentadienyl-lanthanoid(III)-komplexen: I. Röntgenstrukturanalyse von tricyclopentadienyl-praseodym(III)

Abstract A single crystal X-ray analysis of sublimated Cp 3 Pr III confirms a singular polymeric chain structure involving η 5 -coordination of each Pr III ion with three close-lying Cp ligands and η 2 -coordination with a fourth, bridging Cp ligand (formal coordination number: 11, space group: P 2 1 , lattice parameters: a 831.4; b 971.4, c 837.2 pm; β 116.06°). The crystal structure of Cp 3 Pr differs markedly from that reported in 1969 for the similar polymeric samarium complex; on the other hand, some interesting features (concerning the crystallographic parameters, the MC distances and the formal coordination number) in accordance with the recently published structure of polymeric (C 5 H 4 CH 3 ) 2 Yb II . (OC 4 H 8 ) are apparent.

Experimental access to the molecular and electronic structures of organo-f-element complexes by NMR spectroscopy

Abstract The main objective of this survey is to demonstrate that by extensive assessment of variable temperature 1H NMR data obtained on paramagnetic f-element complexes in solution, not only valuable information on details of the molecular structure, but also on the electronic structure may be deduced. One of the most informative quantities to arrive at is the paramagnetic anisotropy term, χ∥ - χ⊥, of axially symmetric molecules from which, if the bulk susceptibility χ is also known, the crystal-field sensitive parameters χ∥ and χ⊥ can be derived. The majority of the examples considered belong to the widely studied type [Cp3fMLn]q (Cp = η5C5H4R); fM = Pr(III), Nd(III), Yb(III) and U(IV); n = 0, 1 and 2; q = 0 or −1) and to the uranocene family. The survey also includes the two sub-classes of novel anionic complexes [Cp3LnL]− and [(Cp3Ln)2(μ-L)]−, respectively, and different isomers of the general composition [Cp3UXY]q (L = lanthanoid).

Koordinationsverhältnisse in basenfreien tricyclopentadienyl-lanthanoid(III)-komplexen: IV. Die röntgenstrukturen von tricyclopentadienyl-erbium(III) und -thulium(III)☆

Abstract The single crystal X-ray analyses of sublimated (C5H5)3Er (6) and (C5H5)3Tm (7) confirm, for the first time, the existence of coordinatively well-saturated molecules containing just three η5-C5H5 ligands per metal ion (formal coordination number: 9, space group: Pna21, lattice parameters: a 1972.1(3), b 1389.4(1), c 862.4(3) pm for 6, and a 1999.1(3), b 1379.8(4), c 1379.8(4), c 857.8(3) pm for 7; R = 0.076 and 0.047, respectively). Individual molecules align themselves into chains by Van der Waals interactions. The structures of 6 and 7 show a marked contrast to those of their La und Pr homologues on the one hand, and with the structure of (C5H5)3Lu on the other.

Facile insertion of carbon monoxide into the UC and UN bonds of some tris(cyclopentadienyl)uranium(IV)-alkyl and -dialkylamide derivatives

Abstract In contrast to some earlier indications, various organo-uranium(IV) complexes of the general type Cp 3 UX (Cp = η 5 -C 5 H 5 ; X = CH 3 , C 2 H 5 , i-C 3 H 7 , n-C 4 H 9 , t-C 4 H 9 , N(C 2 H 5 ) 2 , and even P(C 6 H 5 ) 2 and NCBH 3 , but not BH 4 or NCS) react in solution with CO under mild conditions, (viz. room temperature and atmospheric pressure of CO). The (IR, 1 H NMR and NIR/VIS) spectroscopic properties of the (1:1) insertion products in case of X = alkyl or dialkylamide are in full accord with their formulation as dihapto-acyl and dihapto-carbamoyl complexes, respectively. While the carbenoid η 2 -OCX ligands are reluctant to undergo consecutive reactions typical of other oxy-carbene systems, reversible equilibria between monomers and dimers in solution (for R = CH 3 and C 2 H 5 ) cannot be ruled out. On the other hand, the dihapto-acyl complexes show a clean reversibility of the CO-uptake at temperatures above 60°C.

Umlagerung von tetrahydrofuran im lanthanoid-Organyl: Die kristallund molekülstrukturen von bis(cyclopentadienyl)ytterbium(III) (μ-n-buten-2-olat) und bis(methylclopentadienyl)ytterbium(III) (μ-η2 : η1-tetrahydrofuran-2-olat)

Abstract The two new complexes [(C5H5)2YbIII{C5H5(NtBu)2}]n (1) and [(C5H4CH3)2YbIIIOC 10H19]n (3), respectively (n ≧ 1; (C10H19O− = (−)-mentholate), react with tetrahydrofuran to give the modified alkoxide systems [(C5H5)2YbIII (μ-OCH2CHCHCH3)]2 (2) and [(C5H4CH3)2YbIII(μ-Otsqb|CH (CH2)3O)]2 (4). Both 2 and 4 have been subjected to single-crystal X-ray analyses. 2: Triclinic, P 1 ; a 807.8(2), b 846.7(2), c 1086.1(4) pm; α 111.9(2), β 91.03(2), γ 113.15(2)° ; R = 0.090 (Rw = 0.091. 4: Monoclinic, P21/n; a 1016.9(4), b 1256.6(5), c 1201.9(4) pm; β 90.52(31)°; R = 0.044 (Rw = 0.041).

Metal-bridging versus chelating Me2Si(C5H4)2-ligands in binuclear complexes: II. The crystal structures of [Me2Si(C5H4)2Yb(μ-Br)]2 and non-sublimed [(C5H5)2Yb(μ-Cl)]2

Abstract YbBr 3 reacts with Na 2 [Me 2 Si(C 5 H 4 ) 2 ] (1:1) to afford the new dimer, Si,Si,Si′,Si′-tetramethyl-disila[1.1]ytterbocenophane dibromide, [Me 2 Si(C 5 H 4 ) 2 Yb(III)(μ-Br)] 2 ( 4 ), the structure of which was determined by a low-temperature crystallographic X-ray study. Complex 4 is isostructural with its analogue that contains Cl instead of Br. Simple model calculations have led to some predictions about the relative stabilities (depending on the nature of M and X) of the two [Me 2 Si(η 5 -C 5 H 4 ) 2 M(μ-X)] 2 isomers with metal-bridging and chelating Me 2 Si(C 5 H 4 ) 2 ligands, respecctively. The calculations indicate that the structurally undistorted {Me 2 Si(C 5 H 4 ) 2 } 2− anion is very poorly suited for metal coordination in either isomer. From solutions of [(C 5 H 5 ) 2 Yb(μ-Cl)] 2 ( 1a ), crystals of the so far unreported modification 1a′ of this dimer were obtained, and its [(C 5 H 5 ) 2 Sc(μ-Cl)] 2 -like crystal structure was determined.

[(Me3SnIV)4FeII(CN)6·4H2O]: Ein zinnorganisches “Berlinerblau-Analogon” mit strukturbestimmenden O-H⋯N-Wasserstoffbrückenbindungen☆

Abstract The lattice of the new organometallic coordination polymer: [(Me 3 Sn) 4 Fe(CN) 6 ·4H 2 O]∞ is built up of nonlinear and chains (O⋯O: 2.628(11) A) which are interlinked by the coordinated and “zeolitic” H 2 O molecules, respectively, via six (comparatively weak) OH⋯N-hydrogen bonds (O⋯N: 2.972(8) and 3.052(8) A). Orthorhombic single-crystal, space group Cmca , a 17.064(2), b 18.534(2), c 11.586(1) A; R = 0.054 ( R w =0.059.

Zur reaktion von tricyclopentadienyl-lanthanoid-komplexen mit 1-alkinen

Abstract Contrary to the prediction based on published p K 3 -data (for cyclopentadiene and phenylethyne), Cp 3 Ln III -complexes react readily with various 1-alkynes, HCCR, by liberating cyclopentadiene. While for Ln = Yb and R = n-alkyl the formation of the novel metallacycles [Cp 2 YbCCR] 3 involving bridges and quite exceptional 1 H NMR spectroscopic features is preferred, the “lighter” Ln-element Nd apparently avoids the formation of corresponding {Cp 2 NdCCR} moieties with still intact μ-(CCR) ligands in favour of a partial regeneration of Cp 3 Nd.