Synthesis and Characterization of Free and Coordinated 1,2,3-Tripnictolide Anions

We have investigated the chemical reactivity of heptaatomic anionic clusters of the group 15 elements ([E7]3–/[HE7]2–, E = P, As) toward the symmetric and asymmetrically substituted alkynes diphenylacetylene and phenylacetylene. The results reported herein, alongside a previous report on the reactivity of such clusters toward acetylene, describe a versatile route by which to access otherwise elusive 1,2,3-tripnictolide anions of the general formula [E3C2RR′]− (R = R′ = H, E = P (1), As (2); R = R′ = C6H5, E = P (3) As (4); R = H, R′ = C6H5, E = P (5), As (6)). These species can be isolated as [K­(18-crown-6)]+ or [K­(2,2,2-crypt)]+ salts. All anions were characterized by multielement NMR spectroscopy and electrospray mass spectrometry. In addition, single-crystal X-ray diffraction structures of the novel species [K­(18-crown-6)­(THF)2]­[3], [K­(2,2,2-crypt)]­[4]·xTHF (x = 0, 0.5), and [K­(18-crown-6)­THF]­[6] were also obtained. The chemical reactivity of these group 15 cyclopentadienyl analogues has been explored in a series of ligand displacement reactions with Mo­(CO)3(L)3 (L = CO, CH3CN) to yield the complex anions [(η5-E3C2H2)­Mo­(CO)3]− (E = P (7), As (8)), [{η5-E3C2(C6H5)2}­Mo­(CO)3]− (E = P (9), As (10)), and [{η5-E3C2H­(C6H5)}­Mo­(CO)3]− (E = P (11), As (12)).