Pyrrole‐based pincer ligands containing iminophosphorane moieties and their coordination chemistry with group 1 metals and magnesium

The Staudinger reaction of 2,5‐bis((di‐ tert ‐butylphosphaneyl)methyl)‐1 H ‐pyrrole ( t Bu PNP)H; t Bu PNP=C 4 H 2 N‐2,5‐CH 2 P t Bu 2 ) with 2 equiv. of Me 3 SiN 3 cleanly furnishes 1,1′‐((1 H ‐pyrrole‐2,5‐diyl)bis(methylene))bis(1,1‐di‐ tert ‐butyl‐ N ‐(trimethylsilyl)‐λ 5 ‐phosphanimine) ( 1 ; (NPNPN)H, NPNPN=C 4 H 2 N‐2,5‐CH 2 P t Bu 2 NSiMe 3 ) in excellent yield. Pyrrole 1 is easily deprotonated by alkali metal amides, [MN(SiMe 3 ) 2 ] (M=Li, Na, K, Cs) to yield the corresponding alkali metal pyrrolides, 1‐M . Compound 1‐Li is features a κ‐ N , N , N coordination whereby both iminophosphorane side‐arms are coordinated to the lithium cation (with additional short Li⋅⋅⋅H contacts, whereas the heavier congeners form dimeric structures. This results in κ‐N,N coordination within one [(NPNPN)M] (M=Na, Cs) unit, and the dimeric structure is then completed by additional η 5 ‐coordination of the pyrrolyl ligand to the neighbouring alkali metal. Furthermore, heteroleptic magnesium alkyl complexes, 1‐MgR , are isolated from the reaction of [MgR 2 ] (R= CH 2 SiMe 3 , CH 2 CMe 3 , CH 2 CMe 2 Ph) with (PNP*)H (1 equiv).