6533b81ffe1ef96bd1277f1e

RESEARCH PRODUCT

Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)3(NR‘)]•2-

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The reaction of Cl3PNSiMe3 with 3 equiv of LiHNR (R = iPr, Cy, tBu, Ad) in diethyl ether produces the corresponding tris(amino)(imino)phosphoranes (RNH)3PNSiMe3 (1a, R = iPr; 1b, R = Cy; 1c, R = tBu; 1d, R = Ad); subsequent reactions of 1b−d with nBuLi yield the trilithiated tetraimidophosphates {Li3[P(NR)3(NSiMe3)]} (2a, R = Cy; 2b, R = tBu; 2c, R = Ad). The reaction of [(tBuNH)4P]Cl with 1 equiv of nBuLi results in the isolation of (tBuNH)3PNtBu (1e); treatment of 1e with additional nBuLi generates the symmetrical tetraimidophosphate {Li3[P(NtBu)4]} (2d). Compounds 1 and 2 have been characterized by multinuclear (1H, 13C, and 31P) NMR spectroscopy; X-ray structures of 1b,c were also obtained. Oxidations of 2a−c with iodine, bromine, or sulfuryl chloride produces transient radicals in the case of 2a or stable radicals of the formula {Li2[P(NR)3(NSiMe3)]LiX·3THF}• (X = Cl, Br, I; R = tBu, Ad). The stable radicals exhibit C3 symmetry and are thought to exist in a cubic arrangement, with the monomeric LiX unit bonded to the neutral radical {Li2[P(NR)3(NSiMe3)]}• to complete the Li3N3PX cube. Reactions of solvent-separated ion pair {[Li(THF)4]{Li(THF)2[(μ-NtBu)2P(μ-NtBu)2]Li(THF)2} (6) with I2 or SO2Cl2 produce the persistent spirocyclic radical {(THF)2Li(μ-NtBu)2P(μ-NtBu)Li(THF)2}• (10a); all radicals have been characterized by a combination of variable concentration EPR experiments and DFT calculations. peerReviewed