Jürgen Dr. Rohrmann

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: XIII. Aufbau, strukturchemie und reaktivität von schwefel- und selen-brücken in zweikernigen organochrom-komplexen

Novel dinuclear organochromium complexes exhibiting bare sulfur and selenium bridging ligands are accessible by treating trithiazyl trichloride, diselenium dichloride, or sodium selenite/hydrochloric acid, respectively, with the ionic complex species M+ [(η5-C5R5)Cr(CO)3]− (1: M = K, R = CH3 6a: M = Na, R = H). The monoselenido and diselenido complexes (μ-Se)[(η5-C5H5)Cr(CO)2]2 (7) and (μ-Se2)[η5-C5H5)Cr(CO)2]2 (8) are also obtained by treatment of [(η5-C5H5)Cr(CO)3]2 with equimolar or excess amounts of black selenium, respectively (yield 98%). The thio- and selenoformaldehyde complexes (μ, η2-XCH2[η5-C5R5)Cr(CO)3]2 (5: X = S, R = CH3; 9a: X = Se, R = H) are formed when diazomethane is added to the reactive precursor compounds (μ, η1: η2-S2)[(η5-C5Me5)2Cr2(CO)5] (2) and (μ-Se2)[η5-C5H5Cr(CO)2]2 (8), respectively; this synthetic methodology yields the selenoacetone complex (μ, η2-SeCMe2)[(η5-C5H5)Cr(CO)2]2 (9b), with compound 7 and 2-diazopropane acting as starting compounds in this case. The same products are obtained in a much better way if the respective diazoalkanes are treated with the monoselenido complex (μ-Se)[(η5-C5H5)Cr(CO)2]2 (7) having chromium—selenium triple bonds; in contrast, the μ-sulfido complex 3, structurally analogous to 7, is unreactive in the presence of diazoalkanes. The μ, η2: η2-disulfido complex 4 exhibits a symmetrical four-membered Cr2S2 core which, according to a single-crystal X-ray structure determination, is folded by 120° along the very short sulfur—sulfur bond (199.5(2) pm), thus describing a butterfly-type geometry; bonding interaction between the two metal atoms is not present (d(Cr ⋯ Cr) 377 pm). In agreement with the EAN rule, the μ-selenido complex 7 displays a linear coordinated selenium bridge (X-ray structure) bonded to both organochromium fragments via cumulated triple bonds (d(CiSe) 220.6(1), 221.1(1) pm). The relative orientations of the (η5-C5H5)Cr(CO)2 structures in the crystal yield an anticlinal conformation of the molecule.

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: XVII. Selen- und tellur-brücken in organometallkomplexen: AUFBAU, protonierung und methylierung

Abstract Selenium acts as a bridging ligand between two iron atoms in the novel complex (μ-Se)(η 5 -C 5 H 5 )Fe(CO) 2 ] 2 ( 1 ), obtained in 60% yield from Na + [(η 5 -C 5 H 5 )Fe(CO) 2 ] and Se 2 Cl 2 . 1 displays nucleophilic reactivity towards protic acids (e.g., HBF 4 ·OEt 2 ) and methyl triflate, CF 3 SO 3 CH 3 , thus giving the protonated and methylated ionic species [(μ-SeR)(η 5 -C 5 H 5 )Fe(CO) 2 2 ] + (R = H: 2a , BF 4 salt; R = CH 3 : 2b , PF 6 salt) in quantitative yields. Rapid deprotonation of 2a occurs in the presence of bases such as diethylamine. Analogous protonation and methylation reactions have been observed with the tellurium complex (μ-Te)[(η 5 -C 5 H 5 )Cr(CO) 3 ] 2 ( 3 ); the ionic compounds [(μ-TeH)(η 5 -C 5 H 5 )Cr(CO) 3 2 ]BF 4 ( 4a ) and [(μ-TeCH 3 ) (η 5 -C 5 H 5 )Cr(CO) 3 2 ]PF 6 ( 4a ), respectively, are obtained. In contrast, the electron-deficient tellurium ligand of the manganese complex (μ 3 -Te)[(η 5 -C 5 H 5 )Mn(CO) 2 ] 3 ( 5 ) is neither attacked by Bronsted acids nor by electrophilic methylating agents (e.g., CF 3 SO 3 CH 3 ) but is rather methylated by methyllithium to give the anionic species [(μ 3 -TeCH 3 )η 5 -C 5 H 5 )Mn(CO) 2 3 ] − that can be isolated pure as the PPN + salt 6 .

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: IV. Chrom-schwefel- und chrom-selen-bindungen: Knüpfung, umwandlungsreaktionen und alkylidenaddition

Abstract New dinuclear chromium—sulfur complexes containing one or two sulfur atoms are formed upon reaction of the ionic complex K[(η 5 -C 5 Me 5 )Cr(CO) 3 ] (Me = CH 3 ; 1) with trithiazyl trichloride at temperatures below ambient. The μ(η 1 :η 2 )-disulfur complex 2a of composition (η 5 -C 5 Me 5 ) 2 Cr 2 (CO) 5 S 2 undergoes concomitant CO-elimination and desulfurization on heating or in the presence of triphenylphosphine; the CrSCr-complex (η 5 -C 5 Me 5 ) 2 Cr 2 (CO) 4 S ( 2c ) is formed in these cases. When diazomethane is treated with 2a , a novel μ,η 2 -thio- formaldehyde complex ( 2d ) results, again following CO- and S-extrusion. While the triple-bonded CrSCr-skeleton present in 2c does not allow alkylidene additions, such reactions, which proceed cleanly, are observed with the corresponding μ 5 -seleno derivative (η 5 -C 5 H 5 ) 2 Cr 2 (CO) 4 Se ( 4 ) synthesized from Na[(η 5 -C 5 H 5 )Cr(CO) 3 ] and sodium selenite in the presence of hydrochloric acid.

Metallorganische Lewis-Säuren, XXXV. Bildung und Struktur chalkogenverbrückter Metallkomplexe: [{(μ5-C5H5)(OC)2Fe}2SeSe{Fe(CO)2(μ5-C5H5)}]+BF4- und [(μ5-C5H5)(OC)2FeS(R)Re(CO)5]+BF4- (R = Me, Ph) / Organometallic Lewis Acids, XXXV. Formation and Stucture of Chalcogen Bridged Metal Complexes: [{(μ5-C5H5)(OC)2Fe}2SeSe{Fe(CO)2(μ5-C5H5)}]+BF4- and [(μ5-C5H5)(OC)2FeS(R)Re(CO)5]+BF4- (R = Me, Ph)

The cationic diselenium bridged title compound 2 and [{(μ5-C5H5)(CO)2Fe}3Se]+BF4- have been isolated from the reaction of (OC)5ReFBF3 with (μ2-Sen)[(μ5-C5H5)(CO)2Fe]2 (n = 1, 2). The heterometallic μ-thiolato title complex has been prepared from (OC)5ReFBF3 and (μ5-C5H5)(OC)2FeSR (R = Me. Ph; 4). The structures of 2 and 4a have been determined by X-ray diffraction analyses.