While the 29 Si NMR spectra of 2 and 3 show apparent doublets, that of 4 is more complex, consistent with an AA'X spin system with virtual coupling. This spectrum was well simulated with parameters of 1 JSiP = 50.6 Hz, JSiP' = 0.0 Hz, 2 JPP' = 19.0 Hz (Figure ). This 2 JPP' coupling of 19.0 Hz was also used to successfully simulate the 13 C{ 1 H} NMR signals of 4 (see Supporting Information Figures and), further supporting this value for 2 JPP'.