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 GeCl2·1,4-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}2Ge→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-distannacyclobutane, 4. A trapping reaction of 4 with diiron nonacarbonyl gave the novel iron stannavinylidene complex 5. 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 31P and 119Sn NMR spectroscopy.