Synthesis and Structural Characterization of Base-Stabilized Oligomeric Heterovinylidenes

Metalation of the (iminophosphoranyl)phosphine PPh2CH2(PPh2=NSiMe3) (1) with an equimolar amount of n-BuLi afforded the monolithium salt [Li{CH(PPh2)(PPh2=NSiMe3)}(THF)(2)] (2). The reaction of 2 with GeCl2 center dot 1,4-dioxane has led to the formation of a germavinylene moiety, which trimerized to form a new heterocyclic cage compound, [{(PPh2=NSiMe3)(PPh2)C=Ge:}{(PPh2= NSiMe3)(PPh2)C}(2)Ge -> Ge:] (3). A similar reaction of the lithium methanide complex 2 with SnCl2 afforded the stannavinylidene moiety, which underwent a head-to-tail cycloaddition to form a stable 1,3-clistannacyclobutane, 4. A trapping reaction of 4 with diiron nonacarbonyl gave the novel iron stannavinylidene complex S. The solid-state structure analysis of 5 reveals that it contains two stannavinylidene moieties bonded in a Sn-P head-to-tail fashion, with one of the tin(II) centers coordinating to a Fe(CO)(4) moiety. The X-ray structures of 2-5 have been determined by X-ray crystallography. In addition, the dynamic behavior of 5 has been studied by means of variable-temperature P-31 and Sn-119 NMR spectroscopy.