PHOTOLYSIS OF ALKOXY-SUBSTITUTED DISILANYLIRON COMPLEXES - PREPARATION OF DONOR-STABILIZED BIS(SILYLENE)IRON COMPLEXES AND THE CRYSTAL-STRUCTURE OF (ME2SI)=[(ETA-5-C5ME5)FE(CO)]=[SIME(OME)]-OME

Photolysis of Cp'Fe(CO)2SiMe2SiMe(OMe)2(2b) (Cp' = η5-C5Me5) afforded the novel donor-stabilized bis(silylene)iron complexes (Me2Si)⩵[Cp'Fe(CO)]⩵[SiMe(OMe)]--OMe, 3b and 3b', as a pair of geometrical isomers in ca. 2:1 ratio. The X-ray crystal structure of 3b shows very short Fe-Si bonds (2.21 and 2.22 Å), fairly long Si-O(trivalent) bonds (1.79 and 1.80 Å), and an almost planar configuration of the iron atom and terminal methoxy or methyl groups at each silicon. The sp2character of the silicon atoms is further supported by the remarkable low-field chemical shifts of the 29Si NMR signals of 3b and 3b' (δ 127.4, 121.1, 98.9, and 93.9 ppm). These structural and spectroscopic data indicate that the Fe-Si bonds take on partial double-bond character [“bis(silylene)iron” structure], while the Si-O(trivalent) bonds contain covalent and dative contributions. Photolysis of several other alkoxy-substituted disilanyliron complexes also afforded bis(silylene)iron complexes. © 1990, American Chemical Society. All rights reserved.