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Toward Supramolecular Assembly of 10-Vertex {closo-2,1,10-FeC2B7} Clusters: Intramolecular Imidate Formation and Polymetallic, Polycluster Species

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posted on 2010-05-24, 00:00 authored by Andreas Franken, Thomas D. McGrath, F. Gordon A. Stone
Addition of Me3NO to CH2Cl2 solutions of [1-OH-2,2,2-(CO)3-closo-2,1,10-FeC2B7H8] (1a) affords [2,2-(CO)2-1,2-μ-{OCH2NMe2}-closo-2,1,10-FeC2B7H8] (2), which contains a five-membered FeNCOC unit. The same reaction in MeCN as solvent gives [2,2-(CO)2-1,2-μ-{OC(R)NH}-closo-2,1,10-FeC2B7H8] (3a, R = Me). Analogous derivatives [R = CHC(H)Me (3c), p-C6H4NO2 (3d), p-C6H4Br (3f), p-C6H4C(H)O (3g), p-C6H4CCH (3h), p-C5H4N (3i), or NH2 (3j)] are obtained from treatment of CH2Cl2 solutions of 1a with other cyano-containing substrates and Me3NO. The μ-imidate species 3 undergo a variety of subsequent reactions. Thus, oxidative coupling of compound 3h in CH2Cl2, in the presence of CuCl−TMEDA (TMEDA = Me2NCH2CH2NMe2), affords dimeric [2,2-(CO)2-closo-2,1,10-FeC2B7H8-1,2-μ-{OC(NFeH)-p-C6H4-CC}]2 (4), which reacts with [Co2(CO)8] in CH2Cl2 to give the tetracluster species [2,2-(CO)2-closo-2,1,10-FeC2B7H8-1,2-μ-{OC(NFeH)-p-C6H4-{(μ-η22-CC)Co2(CO)6}}]2 (5). Conversely, 3f forms a bis(cluster) species, [2,2′-dppb-{2-CO-1,2-μ-{OC(C6H4Br)NH}-closo-2,1,10-FeC2B7H8}2] (6), upon reaction with dppb (0.5 mol equiv) in refluxing THF (dppb = Ph2P(CH2)4PPh2; THF = tetrahydrofuran). Compound 3a in CH2Cl2 with PHPh2 and Me3NO yields [2-CO-2-PHPh2-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC2B7H8] (7), which, upon reaction with wet NEt3 in CH2Cl2, gives [NHEt3][2-CO-2-{P(O)Ph2}-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC2B7H8] (8). When a mixture of C6H6−CH2I2 was used in the latter reaction, the product was [2-CO-2-PIPh2-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC2B7H8] (9), which itself reacts with AgO2CMe, forming [2-CO-2-{P(O2CMe)Ph2}-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC2B7H8] (10). Compound 3a reacts with excess [NBun4]CN in CH2Cl2 to form the anionic complex [1-OH-2,2-(CO)2-2-CN-closo-2,1,10-FeC2B7H8], isolated as its [N(PPh3)2]+ salt (11), in which the intramolecular imidate portion of the precursor has been lost. The anion of 11 readily coordinates via the cyano group to the cationic {Ir(CO)(PPh3)2}+ fragment (formed from [IrCl(CO)(PPh3)2] and TlPF6), affording [2-{(μ-CN)Ir(CO)(PPh3)2}-1-OH-2,2-(CO)2-closo-2,1,10-FeC2B7H8] (12). Oxidative addition of MeI to the Ir(I) center in 12 gives the corresponding Ir(III) species [2-{(μ-CN)Ir(I)(Me)(CO)(PPh3)2}-1-OH-2,2-(CO)2-closo-2,1,10-FeC2B7H8] (13). The novel structural features of these compoundsincluding hydrogen-bonding interactionswere confirmed by single-crystal X-ray diffraction studies.