Syntheses and Structures of Group 14 1,3-Dimetallacyclobutanes

Metalation of 2,6-lutidine-functionalized bis(phosphoranimines) (Me3SiNPPri2CH2)2C5H3N-2,6 (2) using MgBu2 in THF yielded the magnesium compound [Mg{(Me3SiNPPri2CH)2C5H3N-2,6}THF] (3). Further reaction of 3 with 1 equiv of SnCl2 afforded the tin(II)
compound [{2-{Sn{C(Pri2PNSiMe3)}}-6-{Sn{CH(Pri2PNSiMe3)}Cl}}C5H3N]2 (4). Treatment of 2 with 2 equiv of Pb{N(SiMe3)2}2 afforded the lead(II) compound [{2-{Pb{C(Pri2PNSiMe3)}}-6-{Pb{CH(Pri2PNSiMe3)}N(SiMe3)2}}C5H3N]2 (5). X-ray structural analysis
revealed that 4 and 5 consist of a 1,3-dimetallacyclobutane and two metal(II) alkyl moieties.
Similar reaction of 3 with 1 equiv of GeCl2(dioxane), however, yielded the germanium(II)
compound (6) without forming a similar 1,3-digermacyclobutane ring.