Sterically Tuned P ‐Phosphanylamino Phosphaalkenes (Me 3 Si) 2 C=PN( R )PPh 2 and ( i PrMe 2 Si) 2 C=PN( R )PPh 2

Deprotonation of the aminophosphanes Ph 2 PN(H) R 1a – 1h [ R = t Bu ( 1a ), 1‐adamantyl ( 1b ), i Pr ( 1c ), CPh 3 ( 1d ), Ph ( 1e ), 2,4,6‐Me 3 C 6 H 2 (Mes) ( 1f ), 2,4,6‐ t Bu 3 C 6 H 2 (Mes*) ( 1g ), 2,6‐ i Pr 2 C 6 H 3 (DIPP) ( 1h )], followed by reactions of the phosphanylamide salts Li[Ph 2 PN R ] 2a , 2b , 2g , and 2h with the P ‐chlorophosphaalkene (Me 3 Si) 2 C=PCl, and of 2a – 2g with ( i PrMe 2 Si) 2 C=PCl, gave the isolable P ‐phosphanylamino phosphaalkenes (Me 3 Si) 2 C=PN( R )PPh 2 3a , 3b , 3g , and ( i PrMe 2 Si) 2 C=PN( R )PPh 2 4a – 4g . 31 P NMR spectra, supported by X‐ray structure determinations, reveal that in compounds 2a , 2b , 3a , and 3b , with bulky N‐alkyl groups the Si 2 C=P–N–P skeleton is non‐planar (orthogonal conformation), whereas 3g , 3h , and 4g with bulky N‐aryl groups exhibit planar conformations of the Si 2 C=P–N–P skeleton. Solid 3g and 4g exhibit cisoid orientation of the planar C=P–N–C units (planar I) but in solid 3h the transoid rotamer is present (planar II). From 3g , 4d , and 4g mixtures of rotamers were detected in solution by pairs of 31 P NMR patterns ( 3h : line broadening).