Phosphorus–Boron‐Based Polymers Obtained by Dehydrocoupling of Ferrocenylphosphine–Borane Adducts

Dehydrocoupling of the ferrocenylphosphine–borane adducts [FcPH 2 (BH 3 )] ( 1 ) [Fc = Fe(C 5 H 5 )(C 5 H 4 )] and [FcCH 2 PH 2 (BH 3 )] ( 2 ) with [{Rh(μ‐Cl)(cod)} 2 ] (cod = 1,5‐cyclooctadiene) as catalyst gave the corresponding phosphorus–boron‐based polymers [FcPH(BH 2 )] n ( 3 ) and [FcCH 2 PH(BH 2 )] n ( 4 ) as low‐ (heating in toluene, 3 low and 4 low ) or high‐molecular‐weight (heating without solvent, 3 high or 4 high ) poly(ferrocenylphosphinoborane)s depending on the reaction conditions. Dehydrocoupling of a racemic mixture of [2‐ N , N ‐dimethyl( N ‐borane)aminomethyl‐1‐ferrocenyl]phosphine–borane ( 6 ) resulted in several products, as both BH 3 moieties are apparently involved in polymer formation. Quaternization of the amino group in planar‐chiral [Fe(C 5 H 5 ){C 5 H 3 (CH 2 NMe 2 )PH 2 }] ( 5 ) with MeI and treatment of the corresponding ammonium salt [Fe(C 5 H 5 ){C 5 H 3 (CH 2 NMe 3 )PH 2 }]I ( 8 ) with BH 3 (THF) gave [Fe(C 5 H 5 ){C 5 H 3 (CH 2 NMe 3 )PH 2 (BH 3 )}]I ( 9 ), which proved to be a suitable precursor for selective dehydrocoupling to yield an ionic polymer, namely, {[Fe(C 5 H 5 ){C 5 H 3 (CH 2 NMe 3 )PH(BH 2 )}]I} n . The ferrocenylphosphine–borane adducts 1 , 2 , and 6 were characterized by 31 P, 11 B, 1 H, and 13 C NMR spectroscopy, and the polymers were characterized by multinuclear NMR and IR spectroscopy, gel permeation chromatography (GPC), and thermal analysis [differential thermal analysis (DTA)/thermogravimetry (TG)]. The ionic precursor 9 and the resulting polymer are highly insoluble and were characterized by solid‐state 31 P NMR spectroscopy, IR spectroscopy, and thermal analysis. Molecular structures of 1 , 6 , 8 , and 9 were determined by X‐ray crystallography.