Zwitterionic Base-Stabilized Digermadistannacyclobutadiene and Tetragermacyclobutadiene

摘要

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=Ph(NtBu)_2), with two equivalents of the amidinate tin(II) chloride, [LSnCl] (2), and KC_8 in tetrahydrofuran (THF) at room temperature afforded a mixture of the zwitterionic basestabilized digermadistannacyclobutadiene, [L_2Ge_2Sn_2L'_2] (3; L'=LGe:), and the bis(amidinate) tin(II) compound, [L_2Sn:] (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-iPr_2C_6H_3) in THF at room temperature. Moreover, the reaction of 1 with the “onio-substituent transfer” reagent [4-NMe_2-C_5H_4NSiMe_3]OTf (8) in THF and 4-(N,N-dimethylamino)pyridine (DMAP) at room temperature afforded a mixture of the zwitterionic base-stabilized tetragermacyclobutadiene, [L_4Ge_6] (9), the amidinium triflate, [PhC(NHtBu)_2]OTf (10), and Me_3SiSiMe_3 (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.