Manfred L. Ziegler

Vinylidene transition-metal complexes: I. Novel rhodium(I) and rhodium(III) complexes containing alkynes, alkynyls, and vinylidenes as ligands.Crystal structure of IC5H5Rh(CCHPh)(PPri3)

Abstract The syntheses of the novel cyclopentadienylphosphinevinylidenerhodium complexes C 5 H 5 Rh(CCHR)(PPr i 3 ) (R = Ph, Me, H) and, for R = Ph, of the isomeric alkynyl hydrido compound C 5 H 5 RhH(C 2 Ph)(PPr i 3 ) are reported. The square-planar complexes trans -[RhCl(RC 2 H)(PPr i 3 ) 2 ] (IIa, IIb), which in solution are in equi-librium with the five-coordinated pyridine to give the octahedral compounds RhHCl(C 2 R)(PRr i 3 ) 2 (py) (VIa, VIb). Treatment of Via, VIb with NaC 5 H 5 gives the vinylidene complexes IVa, IVb in good yield. C 5 H 5 Rh(CCH 2 )(PPr i 3 ) (IVc) is directly obtained from trans -[RhCl(C 2 H 2 )(PPr i 3 ) 2 ] (IIc) and NaC 5 H 5 . Mechanistic studies confirm that the reaction of VIa, VIb with the cyclopentadienide anion primarily gives, by elimination of HCl, the rhodium(I) compounds trans -[Rh(C 2 R)(py)(PPr i 3 ) 2 ] (VIIIa, VIIIb), which react with cyclopentadiene, possibly via trans -[Rh(C 2 R)(η 2 -C 5 H 6 )(PPr i 3 ) 2 ](X) as an intermediate, to give C 5 VIIIa with cyclopentadiene in presence of water gives the complex C 5 H 5 RhH(C 2 Ph)(PPr i 3 ), which isomerizes only slowly to form IVa and, therefore, is not an intermediate in the reaction of VIIIa and C 5 H 6 to give IVa. The crystal structure of IVa has been determined. The RhCC arrangement is almost linear. The RhC distance is significantly shorter than in carbenerhodium complexes, which, in agreement with 13 C NMR data and MO calculations, indicates a high degree of multiple bonding.

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: VII. Oxidative decarbonylierungsprozessein der photochemie von tricarbonyl(η5-pentamethylcyclopentadienyl)rhenium: Neue oxo—rhenium-komplexe

Short-wavelength photolysis of tricarbonyl(η5-pentamethylcyclopentadienyl)rhenium (1) (λ < 300 nm, quartz-glass) in tetrahydrofuran yields under partial or complete decarbonylation three novel organorhenium compounds, with the relative yields depending upon the irradiation time. Formed by exhaustive oxidative decarbonylation, the complex trioxo(η5-pentamethylcyclopentadienyl)rhenium(VII) (5) represents the first example of the new class of oxo half-sandwich complexes. The derivatives (μ-O)[(η5-C5Me5)Re(CO)2]2 (2; Me = CH3) and (η5-C5Me5)2Re2(CO)2O2 (3; Me = CH3) containing both oxo and carbonyl ligands are formed from 1 at shorter irradiation times. Both compounds are isolable intermediates along the mechanistically not yet fully established sequence 1 → → 5 as they are degraded to 5 under CO2 elimination in the presence of air and/or light. The mixed oxo carbonyl complex 2 has been characterized by means of single-crystal X-ray diffraction techniques (triclinic, space group P1-Ci1; a 907.4(2), b 1040.2(3), c 1414.3(4) pm; α 79.99(2), β 88.42(2), γ 66.18(2)°; Riso = 0.068, Raniso = 0.037, Rw = 0.031). The molecular structure centres around an isosceles Re2O triangle whose metal centres exhibit a strongly distorted square-pyramidal geometry; the metal-metal distance recorded at 281.7(1) pm is in agreement with a single bond by the EAN rule. The centrically coordinated, planar five-membered ring ligands are parallel to each other (interplanar angle 2°) and occupy trans-positions with respect to the central Re2O geometry.

Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen. XV: Reduktive Aggregation des Halbsandwich-Komplexes Trioxo(η5-pentamethylcyclopentadienyl)rhenium

Abstract The trioxo complex (η 5 -C 5 Me 5 )ReO 3 ( 1 ) undergoes partial deoxygenation in the presence of the Lewis base triphenylphosphane. When this reaction is conducted in tetrahydrofuran solution with rigorous exclusion of air, the dinuclear, very oxygen-sensitive d 2 -Re V derivative 2 of composition (η 5 -C 5 Me 5 ) 2 Re 2 O 4 is cleanly formed. In the presence of trace amounts of oxygen, however, a second reaction pathway is opened up, which leads to the tetranuclear Re V /Re VII complex 3 in 30–60% yield. This compound is structurally derived from the dinuclear species 2 , in that one of the two terminal oxo groups is replaced by two O -coordinated perrhenate ligands; in keeping with the requirements of the EAN rule and supported by the bond length of 265.1(1) pm, the doubly oxygen-bridged Re V -Re V interaction is best interpreted in terms of a metal—metal double bond (single-crystal X-ray diffraction study). Finally, upon treatment of 1 with triphenylphosphane in air-saturated solutions of tetrahydrofuran, the ionic cluster compound 4 of net composition (C 5 Me 5 ) 3 Re 5 O 14 is surprisingly formed in 70–90% yield. This latter complex exhibits the C 3 -symmetrical cation [(η 5 -C 5 Me 5 ) 3 Re 3 (μ-O) 6 ] 2+ , with the two counter-ions being isolated perrhenate groups. The metal—metal distances within the cyclic cation are crystallographically identical and amount to 274.7(2) pm (single-crystal X-ray diffraction study).

A superphane of cyclobutadiene capped by cyclopentadienylcobalt.

Abstract The reaction of cyclodeca-1,6-diyne ( 4 ) with the cyclopentadienylcobalt derivatives (C5H5)Co(CO)2 and (C5H5)Co(1,5-C8H12) yields the [34](1.2.3.4)cyclobutadienophane complexed with two (C5H5)Co-units ( 7 ) in one step.

Metallorganische Chemie des Technetiums: VIII. Technetium(I)-carbonyl-Komplexe mit Polypyrazol-1-yl-borato-Liganden im Vergleich mit seinen Mn- und Re-Homologen

Abstract The compounds HB(C3H3N2)3Tc(CO)3 and HB(3,5-Me2C3HN2)3Tc(CO)3 have been synthesized for the first time, and their molecular and crystal structure as well as the structures of the known analogous compounds of manganese and rhenium determined by single-crystal X-ray diffraction. The IR-, 1H-NMR-, 13C-NMR-, UV- and EI-MS-spectroscopic data are discussed in correlation to the electric dipole moment and the charge distribution within the molecule.

Ethylen(hydrido)-metallkomplexe aus M(CH2)CH3-vorstufen: modellreaktionen für einen elementarschritt der fischer-tropsch-synthese

Abstract The compounds C 6 Me 6 Ru(Ch 3 ) 2 , C 6 H 6 Os(CH 3 ) 2 PMe 3 and C 5 H 5 Ir(CH 3 ) 2 -Ppr i 3 react with [CPh 3 ]PF 6 in Ch 2 Cl 2 to give the ethylene(hydrido)metal complexes [C 6 Me 6 RuH(C 2 H 4 )PR 3 ]PF 6 , [C 6 H 6 OsH(C 2 H 4 )PMe 3 ]PF 6 and [C 5 H 5 IrH(C 2 H 4 )PPr i 3 ]PF 6 , respectively. Treatment of C 6 Me 6 RuCH 3 (C1)PMe 3 with [CPh 3 ]PF 6 leads to cleavage of the RuCH 6 bond instead of hydride elimination; in the presence of PMe 2 Ph the compound [C 6 Me 6 RuCl(PMe 2 Ph)PMe 3 ]PF 6 is obtained. The reaction of C 5 H 5 RhCH 2 OMe(PMe 3 )CH 3 with HBF 4 gives [C 5 H 5 RhH(C 2 H 4 )PMe 3 ]BF 4 and methanol. It is assumed that the formation of the ethylene(hydrido)metal complexes always occur via a M(CH 2 )CH 3 intermediate, radical intermediates not being observed. The crystal structure of [C 6 Me 6 RuH(C 2 H 4 )PPh 3 ]PF 6 has been determined. The cation of 1.50 A. The CC distance in the ethylene ligand is 1.41(1) A and thus is significantly longer than in the free olefin.

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: IX. Tellur-brücken in organometall-komplexen: Aufbau, protonierung und molekülgeometrie☆

Abstract Ligand-free tellurium acts as a bridging element in the novel chromium, molybdenum, and tungsten complexes of composition (μ-Te)[(η 5 -C 5 R 5 )M(CO) 3 ] 2 ( 2a–2e ; R = H, CH 3 ; M = Cr, Mo, W) which are accessible in 32–72% isolated yield on treatment of the ionic precursor species Na + (K + ) [(η 5 -C 5 R 5 )M(CO) 3 ] − ( 1a–1e ) with potassium tellurite in the presence of hydrochloric acid. The new compounds have been structurally characterized (X-ray diffraction, compound 2a ) and exhibit bent metal-tellurium-metal frameworks (e.g. Cr,Te,Cr 117.2(0)°). The comparably long chromium-tellurium distances recorded in the case of 2a (279.9(1), 281.4(1) pm) are interpreted as single bonds, thus being in agreement with the electronic requirements of the chromium centres. The tellurium bridge is considered to act as a two-electron ligand which stabilizes two (η-C 5 H 5 )Cr(CO) 3 fragments. Neither under thermal conditions nor upon photolysis do complexes 2a–2e undergo partial decarbonylation. Hence, they do not represent suitable precursors of the hitherto unknown derivatives of composition (μ-Te)[(η 5 -C 5 R 5 )M(CO) 2 ] 2 ; these latter compounds should contain linear multiple-bonded structures like those established for the stoichiometrically analogous sulfur and selenium derivatives. Protonation of 2a with ethereal tetrafluoroboric acid quantitatively yields the Bronsted-acidic ionic complex 3a of formula [(μ-TeH){(η-C 5 H 5 )Cr(CO) 3 } 2 ][BF 4 ]. which can be deprotonated by diethylamine in reverse to its formation.

Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen. X: Aufbau einer tetraedrischen TeMnFe2-Clusterverbindung nach dem Isolobal-Prinzip

Abstract Treatment of the tellurium complex (μ-Te)[(η 5 -C 5 Me 5 )Mn(CO) 2 ] 2 ( 1 ; Me = CH 3 ) with enneacarbonyldiiron yields the tetranuclear cluster compound 2 of composition (η 5 -C 5 Me 5 )MnFe 2 Te(CO) 8 . From a structural point of view, this compound is considered to be a metallatetrahedral-type molecule, according to a single-crystal X-ray diffraction study, thus following the concept of isolobal connectivity (monoclinic, space group P 2 1 / n ; a 982.4(2), b 1483.6(3), c 1535.5(5) pm, β 97.22(2)°; R (iso) = 0.13, R (aniso) = 0.036, R w = 0.033).

Neuartige Phosphor/Schwefel-Liganden in aus Cp★2 Mo2(CO) 4 (Cp★ = η5-C5Me5) und P4S3 erzeugten Cp★2Mo2PxSy- Komplexen (× = 2, 4; y = 5 - ×)

Abstract The reaction of Cp★ 2 Mo 2 (CO) 4 ( Mo  Mo ) (Cp★ = η 5 -C 5 Me 5 ) with P 4 S 3 in boiling toluene gives the complexes Cp★(CO) 2 MoP 3 (I), Cp★ 2 (CO) 4 Mo 2 P 2 (II), Cp★ 2 Mo 2 P 2 S 3 (III), and Cp★ 2 Mo 2 P 4 S (IV). The structures of III and IV follow from their 31 P NMR spectra as well as from an X-ray diffraction analysis of their corresponding Cr(CO) 5 monoadducts (VII and VIII). Characteristic features of the structure of VII are an η 2 -PS and an η 3 -P 3 ligand in a plane perpendicular to the MoMo axis, which is bisecting. A similar geometry is found for VIII, which, however, contains an η 2 -S 2 and an η 3 -P 2 S ligand. Coordination of the Cr(CO) 5 fragment to the P 2 S ligand in III may either occur at an S atom, which then acts as a μ 5 -bridge (VIII) or at a P atom as manifested by the presence of a PW coupling in the W(CO) 5 adduct (VI).

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: XVIII. Heterometallische selenido-komplexe☆

Abstract The selenium bridge present in the iron complex (μ-Se)[(η5-C5H5)Fe(CO)2]2 (1) exhibits nucleophilic character and is thus prone to addition reactions with electrophilic reagents. Treatment of 1 with the coordinatively unsaturated fragment (η5-C5H5)Mn(CO)2 results in formation of the heteronuclear complex (η5- C5H5)3Fe2MnSe(CO)6 (2) which contains a flattened pyramidal Fe2MnSe core, with the selenium atom occupying the top of position of this framework. No FeMn and FeFe bonds are present in this molecule (single crystal X-ray diffraction study). Compound 2 is very light-sensitive in solution, thus giving the derivative (η5-C5H5)3Fe2MnSe(CO)5(3). According to a crystal structure determination, this latter compound once again exhibits a pyramidal Fe2MnSe core but with the iron atoms directly connected with each other via a single bond (266.7(1) pm).