Zwitterionic base-stabilized digermadistannacyclobutadiene and tetragermacyclobutadiene.

The syntheses of a zwitterionic base-stabilized digermadistannacyclobutadiene and tetragermacyclobutadiene supported by amidinates and low-valent germanium amidinate substituents are described. The reaction of the amidinate Ge(I) dimer, [LGe:]2 (1, L=PhC(NtBu)2 ), with two equivalents of the amidinate tin(II) chloride, [LSnCl] (2), and KC8 in tetrahydrofuran (THF) at room temperature afforded a mixture of the zwitterionic base-stabilized digermadistannacyclobutadiene, [L2 Ge2 Sn2 L'2 ] (3; L'=LGe:), and the bis(amidinate) tin(II) compound, [L2 Sn:] (4). Compound 3 can also be prepared by the reaction of 1 with [L(Ar) SnCl] (5, L(Ar) =tBuC(NAr)2 , Ar=2,6-iPr2 C6 H3 ) in THF at room temperature. Moreover, the reaction of 1 with the "onio-substituent transfer" reagent [4-NMe2 -C5 H4 NSiMe3 ]OTf (8) in THF and 4-(N,N-dimethylamino)pyridine (DMAP) at room temperature afforded a mixture of the zwitterionic base-stabilized tetragermacyclobutadiene, [L4 Ge6 ] (9), the amidinium triflate, [PhC(NHtBu)2 ]OTf (10), and Me3 SiSiMe3 (11). X-ray structural data and theoretical studies show conclusively that compounds 3 and 9 have a planar and rhombic charge-separated structure. They are also nonaromatic.