Toward supramolecular assembly of 10-vertex { closo -2,1,10-FeC _2B_7} clusters: Intramolecular Imidate Formation and Polymetallic, Polycluster Species

摘要

Addition of Me_3NO to CH_2Cl_2 solutions of [1-OH-2,2,2-(CO)_3-closo-2,1,10-FeC_2B_7H _8] (1a) affords [2,2-(CO)_2-1,2-μ-{OCH _2NMe_2}-closo-2,1,10-FeC_2B_7H _8] (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- FeC_2B_7H_8] (3a, R = Me). Analogous derivatives [R = CH - C(H)Me (3c), p-C_6H_4NO_2 (3d), p-C _6H_4Br (3f), p-C_6H_4C(H)O (3g), p-C_6H_4C - CH (3h), p-C_5H_4N (3i), or NH_2 (3j)] are obtained from treatment of CH_2Cl_2 solutions of 1a with other cyano-containing substrates and Me_3NO. The μ-imidate species 3 undergo a variety of subsequent reactions. Thus, oxidative coupling of compound 3h in CH_2Cl_2, in the presence of CuCl-TMEDA (TMEDA = Me_2NCH_2CH _2NMe_2), affords dimeric [2,2-(CO)_2-closo-2,1, 10-FeC_2B_7H_8-1,2-μ-{OC(N~(Fe)H)-p- C_6H_4-C - C}]2 (4), which reacts with [Co _2(CO)_8] in CH_2Cl_2 to give the tetracluster species [2,2-(CO)_2-closo-2,1,10-FeC_2B _7H_8-1,2-μ-{OC(N~(Fe)H)-p-C_6H _4-{(μ--~2:-~2-C - C)Co_2(CO) _6}}]_2 (5). Conversely, 3f forms a bis(cluster) species, [2,2′-dppb-{2-CO-1,2-μ-{OC(C_6H_4Br)NH}-closo-2,1, 10-FeC_2B_7H_8}_2] (6), upon reaction with dppb (0.5 mol equiv) in refluxing THF (dppb = Ph_2P(CH _2)_4PPh_2; THF = tetrahydrofuran). Compound 3a in CH_2Cl_2 with PHPh_2 and Me_3NO yields [2-CO-2-PHPh_2-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC_2B _7H_8] (7), which, upon reaction with wet NEt3 in CH_2Cl_2, gives [NHEt_3][2-CO-2-{P(O)Ph _2}-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC_2B _7H_8] (8). When a mixture of C_6H _6-CH_2I_2 was used in the latter reaction, the product was [2-CO-2-PIPh_2-1,2-μ-{OC(Me)NH}-closo-2,1,10-FeC _2B_7H_8] (9), which itself reacts with AgO _2CMe, forming [2-CO-2-{P(O_2CMe)Ph_2}-1,2-μ- {OC(Me)NH}-closo-2,1,10-FeC_2B_7H_8] (10). Compound 3a reacts with excess [NBu~n_4]CN in CH _2Cl_2 to form the anionic complex [1-OH-2,2-(CO) _2-2-CN-closo-2,1,10-FeC_2B_7H_8] -, isolated as its [N(PPh_3)_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)(PPh_3)_2}~+ fragment (formed from [IrCl(CO)(PPh_3)_2] and TlPF_6), affording [2-{(μ-CN)Ir(CO)(PPh_3)_2}-1-OH-2,2-(CO) _2-closo-2,1,10-FeC_2B_7H_8] (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)(PPh_3)_2}-1-OH-2, 2-(CO)_2-closo-2,1,10-FeC_2B_7H_8] (13). The novel structural features of these compounds - including hydrogen-bonding interactions - were confirmed by single-crystal X-ray diffraction studies.