000K utf8 1100 $c2025 1500 eng 2050 urn:nbn:de:gbv:8:3-2025-00266-8 2051 10.1039/d4py01362j 3000 Wiebe, Matthew A. 3010 Killeen, Charles 3010 Manners, Ian 3010 McIndoe, J. Scott 3010 Staubitz, Anne Christina 3010 Watson, Jade E. T. 4000 $hRoyal Society of Chemistry (RSC) [Wiebe, Matthew A.] 4000 BH3·SMe2 addition enables molar mass control via chain stabilization in phosphine–borane dehydropolymerization$hRoyal Society of Chemistry (RSC) [Wiebe, Matthew A.] 4030 $nRoyal Society of Chemistry (RSC) 4209 We report the synthesis of high molar mass polyphosphinoboranes using commercially available reagents through thermal dehydropolymerization in the presence of Lewis acids and bases. These dehydropolymerizations produce materials of higher molecular weight compared to the state-of-the-art catalyst, Cp(CO)2FeOTf ([PhPH-BH2]n (2), 5 mol% LiOTf, 2 M in 2-MeTHF, 100 °C, 24 h; Mn = 80 000 g mol−1, Đ = 1.64 cf. 5 mol% Cp(CO)2FeOTf, 2 M in toluene, 100 °C, 24 h, Mn = 40 000 g mol−1, Đ = 1.64). We propose a mechanism for the thermal dehydropolymerization of PhPH2·BH3 (1) with additives. Initially, the phosphine–borane adduct dissociates, yielding borane in situ, which acts as a (pre)catalyst for the dehydrogenation of 1. Subsequent addition polymerization occurs as described previously, but the addition of Lewis acids and Lewis bases allows for reversible complexation of both termini. Competition between temporary chain capping and termination events results in fewer termination events over time, leading to high molar mass materials. With this mechanism in mind, we were able to show that added BH3·SMe2 allows for control over the molar mass of the resulting materials. These results show that transition-metal catalysts are not needed in the thermal dehydropolymerization of PhPH2·BH3, and offer a new mechanistic insight that may unlock greater control over the dehydropolymerization of main-group substrates. 4950 https://doi.org/10.1039/d4py01362j$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:gbv:8:3-2025-00266-8$xR$3Volltext$534 4961 https://macau.uni-kiel.de/receive/macau_mods_00005791 5051 540 5550 BH 3 ·SMe 2 5550 molar mass control 5550 polymerisation