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

Abstract

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 + [(η 5-C 5R 5)Cr(CO) 3] − ( 1: M = K, R = CH 3 6a: M = Na, R = H). The monoselenido and diselenido complexes (μ-Se)[(η 5-C 5H 5)Cr(CO) 2] 2 (7) and (μ-Se 2)[η 5-C 5H 5)Cr(CO) 2] 2 ( 8) are also obtained by treatment of [(η 5-C 5H 5)Cr(CO) 3] 2 with equimolar or excess amounts of black selenium, respectively (yield 98%). The thio- and selenoformaldehyde complexes (μ, η 2-XCH 2[η 5-C 5R 5)Cr(CO) 3] 2 ( 5: X = S, R = CH 3; 9a: X = Se, R = H) are formed when diazomethane is added to the reactive precursor compounds (μ, η 1: η 2-S 2)[(η 5-C 5Me 5) 2Cr 2(CO) 5] ( 2) and (μ-Se 2)[η 5-C 5H 5Cr(CO) 2] 2 ( 8), respectively; this synthetic methodology yields the selenoacetone complex (μ, η 2-SeCMe 2)[(η 5-C 5H 5)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)[(η 5-C 5H 5)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, η 2: η 2-disulfido complex 4 exhibits a symmetrical four-membered Cr 2S 2 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 (η 5-C 5H 5)Cr(CO) 2 structures in the crystal yield an anticlinal conformation of the molecule.