Ricardo Serrano

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).

Metallcarbonyl-synthesen: XIII. Eine mangan—mangan-dreifachbindung☆

Abstract Photolysis of the manganese half-sandwich complex (η 5 -C 5 Me 5 )Mn(CO) 3 ( 1 ) in tetrahydrofuran (THF) yields cleanly the solvent complex (η 5 -C 5 Me 5 )(Mn(CO) 2 THF ( 2 ). Compound 2 undergoes spontaneous elimination of carbon monoxide to give at ambient temperature in approx. 20 h, or upon removal of solvent in vacuo, the novel dinuclear derivative (η 5 -C 5 Me 5 ) 2 Mn 2 (μ-CO) 3 ( 3 ). Elemental analyses and infrared and mass as wel as the 1 H and 13 C NMR spectra unequivocally demonstrate this compound to adopt a triply carbonyl-bridged structure containing the first example of a manganeseue5f8manganese multiple bond.

übergangsmetall—methylen-komplexe LII. Synthesekonzepte zum aufbau heterodinuclearer metall—metall-mehrfachbindungen☆

Abstract Novel heterodinuclear metalue5f8metal multiple bonds are accessible by simple high-yield metalue5f8metal coupling reactions: the cobalt—iridum complex (η 5 -C 5 H 5 )Co(μ-CO) 2 Ir(η 5 -C 5 Me 5 ) (Me = CH 3 ;3) is formed as the main product from the reaction of (η 5 -C 5 Me 5 )Ir(CO) 2 ( 1 ) with (η 5 -C 5 H 5 )-Co(π-C 2 H 4 ) 2 ( 2 ), showing that the ethylene ligands of 2 are removed under very mild conditions in the presence of 1 . Further treatment of 3 with precursor 2 gives the heterotrinuclear complex (η 5 -C 5 H 5 ) 2 Co 2 (μ-CO) 3 Ir(η 5 -C 5 Me 5 ) ( 4 ). similar heterodinuclear complexes e.g. (η 5 -C 5 Me 5 )Co(μ-CO) 2 Ir(η 5 -C 5 Me 5 ) can be synthesized in the same way. In contrast, the formation of triple-bonded organometallic compounds from the respective metal carbonyls requires photochemical conditions.