Lithium (S)-1-[2‘-(Methoxymethyl)pyrrolidin-1‘-yl]-3,5-dimethylborata- benzene. An Enantiopure Lithium Salt Possessing a Novel Polymeric Structure¹

Reaction of (S)-2-(methoxymethyl)pyrrolidine (SMPH) with the 1-chloro-3,5-dimethyldihydroborinines 3a,b in the presence of NEt3 afforded the SMP-substituted dihydroborinine isomers 4a−c (95% yield). Metalation of 4a−c with LiN(SiMe3)2 produced the salt lithium (S)-1-[2‘-(methoxymethyl)pyrrolidin-1‘-yl]-3,5-dimethylboratabenzene [Li(1)] (92%). Treatment of Li(1) with [(C5Me5)Fe(NCMe)3]PF6 gave the enantiopure ferrocene analogue (C5Me5)Fe(1) (98%). Crystallization of Li(1) from THP afforded colorless rods of [Li(1)(THP)0.5]∞ (≡2). In the crystal structure, 2 consists of infinite chains with alternating bis(boratabenzene)lithiate sandwich units and tetrahedral LiN2O2 centers. Whereas the B-exocyclic amino and the pendant ether functionalities from the SMP moieties act as donating coordination sites to the metal, the THP serves solely as a space-filling molecule.