Substituent Effects on the Structures of Alkali Metal Phosphido‐Borane Complexes

Metalation of tBu2PH(BH3) (1H), iPr2PH(BH3) (2H), iPrPhPH(BH3) (3H), Ph2PH(BH3) (4H) or (Mes)2PH(BH3) (5H) with one equivalent of nBuLi in either diethyl ether or THF gave the corresponding phosphido‐borane complexes, which were obtained as single crystals of the solvates [{tBu2P(BH3)}Li(OEt2)]∞ (1Li), [{iPr2P(BH3)}Li(THF)2]∞ (2Li), [{iPrPhP(BH3)}Li(OEt2)2]∞ (3Li), [{Ph2P(BH3)}Li(OEt2)2]∞ (4Li), and [{(Mes)2P(BH3)}Li(THF)2]2 (5Li) after crystallization from diethyl ether; the alternative adduct [{Ph2P(BH3)}Li(TMEDA)]∞ (4Li(TMEDA)) was isolated from the reaction of 4Li with TMEDA. Similar metalation reactions between 1H, 2H or 4H and PhCH2Na gave the complexes [{tBu2P(BH3)}Na(THF)]∞ (1Na) and [{iPr2P(BH3)}Na(THF)]∞ (2Na), and [{Ph2P(BH3)}Na(TMEDA)(THF)]∞ (4Na(TMEDA)). Compounds 1Li, 2Li, 3Li, 4Li and 4Li(TMEDA) crystallize as zig‐zag polymers, while 5Li crystallizes as a centrosymmetric dimer; compounds 1Na and 2Na crystallize as ribbon polymers, although these differ significantly in structure, while 4Na(TMEDA) crystallizes as a zig‐zag polymer. A series of lithium and sodium phosphido‐borane complexes is reported. These compounds largely adopt polymeric structures in the solid state, irrespective of the nature of the substituents at phosphorus.