Synthesis and characterization of silicon-based group 14 dendrimers Si{(CH2)2Sn[(CH2)4MPh3]3}4 (M = Ge, Sn)

The catalytic hydrogermylation of Si(CHCH2)(4) with Ph3GeH yielded Si(CH2CH2GePh3)(4) (1). In contrast, Sn(CHCH2)(4) and Sn(CH2CHCH2)(4) reacted with Ph3GeH under the same conditions, forming Ph3Ge(CH2)(2)GePh3 (2) and Ph3Ge(CH2)(3)GePh3 (3), respectively, whereas the reaction of Sn(CH2CH2CHCH2)(4) and Ph3GeH afforded the expected tin-based metallodendrimer Sn[(CH2)(4)GePh3](4) (4). The reactions of Si[(CH2)(2)SnBr3](4) with the Grignard reagents RMgBr (R = CHCH2, CH2CHCH2, (CH2)(2)CHCH2)) produced Si[(CH2)(2)Sn(CHCH2)(3)](4) (5), Si[(CH2)(2)Sn(CH2CHCH2)(3)](4) (6), and Si[(CH2)(2)Sn(CH2CH2CHCH2)(3)](4) (7). While hydrogermylation of 5 and 6 with Ph3GeH resulted in the formation of 2 and 3, respectively, compound 7 reacted with Ph3GeH, providing the expected second-generation Si/Ge/Sn heterometallodendrimer Si{(CH2)(2)Sn[(CH2)(4)GePh3](3)}(4) (8). Correspondingly, hydrostannylation of 7 with Ph3SnH yielded Si{(CH2)(2)Sn[(CH2)(4)SnPh3](3)}(4) (9). All compounds were characterized by multinuclear NMR studies (H-1, C-13, Sn-119), mass spectrometry (MALDI-TOF, EI), and elemental analyses.