Photochemische Substitutionen an Metallcarbonylen und deren Derivaten

Abstract

Durch die vor einigen Jahren gefundene photochemische Reaktion von n‐ und π‐Donatoren mit Metallcarbonylen oder deren Derivaten kann man ein breites Spektrum neuer Metallcarbonyl‐Derivate herstellen, welche thermisch nicht oder nur mit schlechten Ausbeuten zu erhalten sind. — Präparative Verfahren werden beschrieben. An ausgewählten Beispielen wurde der Reaktionsmechanismus dieser photochemisch induzierten Substitutionsreaktionen aufgeklärt und versucht, einen Einblick in die Polarität der Metall‐Liganden‐Bindung zu erhalten. — Dieser Beitrag soll einen Überblick über die in letzter Zeit auf diesem Gebiet erschienenen Arbeiten geben.

A stable carbonyl–pyrazine–metal(0) complex: Synthesis and characterization of cis-tetracarbonylpyrazinetrimethylphosphitetungsten(0)

“…W(CO) 5 [P(OCH 3 ) 3 ] [9], cis-W(CO) 4 (piperidine) 2 [10], W(CO) 4 (g 2:2 -norbornadiene) [11] and W(CO) 4 (g 2:2 -1,5-cyclooctadiene) [12] were prepared according to the literature procedures. (0), W(CO) 5 (pyz), (1), and l-pyrazine-bis(pentacarbonyltungsten(0)), (CO) 5 W(pyz)W(CO) 5 , (2) Following the procedure [2] pyrazine (pyz, 0.454 g, 5.68 mmol) was added to a solution of W(CO) 5 (thf) photogenerated [13] from W(CO) 6 (1.0 g, 2.84 mmol) in 250 mL tetrahydrofuran (thf) at 10°C. After mixing for 2 h, the volatiles were removed under vacuum.…”

Zur Struktur und Komplexchemie von Phosphinoderivaten des 5-Methoxy-2(5H)-furanons / Structure and Coordination Chemistry of Phosphino Derivatives of 5-Methoxy-2(5H)-furanon

“…Tetrahydrofuran (THF) mit UV-Licht bestrahlt. Die gebildete Lösung von Mo(CO)5 • THF setzt man dann mit 3,32 g 2 (10 mmol) um [15]. Aus Diethylether/Chloroform, ockerfarbene Kristalle.…”

Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)₄X₂]₂ (M = Mo, W; X = Cl, Br)

“…Previously, molybdenum aminecarbonyls have been prepared using molybdenum hexacarbonyl as the starting material following a variety of methods among them the following (i) UVirradiation of an amine/hexacarbonyl mixture [1,2], refluxing a carbonyl/amine mixture in a suitable solvent [3] and an indirect method whereby some of the CO groups are substituted with hydrocarbon ligands such as cyclohexatriene, norbornadiene or mesitylene and the products thus obtained are reacted with an amine [4,5]. In a previous study, it was shown that the halocarbonyls, [Mo(CO) 4 X 2 ] 2 (X = Cl, Br), react with primary amines either neat or in an alcohol such as ethanol or methanol as a solvent at ordinary conditions of temperature and pressure to form aminecarbonyls of the type, Mo(CO) 3 L 3 (L = propylamine, butylamine, cyclohexylamine) which could not be obtained by refluxing an amine/hexacarbonyl mixture [6].…”

“…In a previous study, it was shown that the halocarbonyls, [Mo(CO) 4 X 2 ] 2 (X = Cl, Br), react with primary amines either neat or in an alcohol such as ethanol or methanol as a solvent at ordinary conditions of temperature and pressure to form aminecarbonyls of the type, Mo(CO) 3 L 3 (L = propylamine, butylamine, cyclohexylamine) which could not be obtained by refluxing an amine/hexacarbonyl mixture [6]. Piperidine, however, reacts with these halocarbonyl to give Mo(CO) 4 (piperidine) 2 even when the halocarbonyl is refluxed with the neat base [7,8]. During these studies, piperididine was, however, the only base that gave an identifiable organic oxidation product.…”

“…In comparing the similarities and differences in the way the halocarbonyls, [M(CO) 4 X 2 ] 2 (M = Mo,W; X = Cl, Br) react with amines, the reaction of piperidine with W(CO) 4 Br 2 was also attempted to find out what type of product would be formed. As noted earlier, this base reacts with the molybdenum halocarbonyls, [Mo(CO) 4 X 2 ] 2 (X = Cl, Br) to form the complex, Mo(CO) 4 (piperidine) 2 , yet the other amines formed complexes of the type Mo(CO) 3 (amine) 3 [7,8].…”