Tetr asupersilyldiindium(In - In) and Tetrasupersilyldithallium( Tl- Tl): (tBu_3Si)_2M-M(SitBu_3)_2 (M = In, Tl)

摘要

Donor-free, uncharged molecular compounds (RM)_n and (R_2M_)2 with clusters formed from the boron homologues M = Al, Ga, In, Tl have--unlike such compounds with boron clusters--only been known for about ten years. In fact, the compounds of the boron homologues have a tendency to disproportionate (6 RM --> 3 R_2M +3 M --> 2 R_3M + 4 M); however, this process can be stopped at the (RM)_n stage (very bulky groups) or at the (R_2M_)2 stage (medium-sized bulky groups) by employing bulky substituents R such as C_5Me_5 (Cp*), C_5(CH_2Ph)_5 (Cp**), CH(SiMe_3)_2 (Disyl), C(SiMe_3)_3 (Trisyl), 2,4,6-iPr_3C_6H_2 (Trip). 2,4,6-(CF_3)_3C_6H_2 (R~F). Si(SiMe_3)_3 (Hypersilyl), and SitBu, (Supersilyl). Known examples of R_4M_2 and (RM)_n compounds with normal covalent M-M bonds are [(Me_3Si)_2CH]_4M_2 (M = Al, Ga, In), (2.4,6-iPr_3C_6H_2)_4M_2 (M = Al, Ga), [2,4,6-(CF_3)_3C_6H_2]_4M_2 (M = Ga, In), or [(Me_3Si)_3Si]_4Tl_2, and (RA1)_4 (R = SitBu_3, Cp*), (RGa)_4 (R = C(SiMe_3)_3, Si(SiMe_3)_3) or [(Me_3Si)_3CIn]_4, respectively. Only very weak M-M interactions are present in the compounds (Cp*In)_6 and (Cp**M)_2 (M = In, Tl).