Syntheses of Amino‐Substituted Iridabenzofurans and Subsequent Selective N‐Functionalisation

Abstract

The first examples of amino-substituted fused-ring metallabenzenes, the cationic iridabenzofuran [Ir(C H O{NH -2}{OMe-7})(CO)(PPh ) ][O SCF ] (5) and neutral analogue Ir(C H {NH -2}{OMe-7})Cl(PPh ) (6), can be prepared by reduction of the corresponding nitro-substituted iridabenzofurans with zinc and concentrated hydrochloric acid. N-functionalised derivatives of 5 and 6 are formed through alkylation, sulfonylation or acylation. Thus, consecutive treatments with methyl triflate and base gives the corresponding trimethylammonium-substituted iridabenzofurans while sulfonamide derivatives are formed with p-toluenesulfonyl chloride. N-Acylation of 5 or 6 with acid chlorides, however, selectively form either amide or imide products depending on the charge on the metal and the steric size of the acid chloride. Cationic 5 gives amide substituted products regardless of the conditions whereas neutral 6 rapidly undergoes di-N-acylation with excess benzoyl chloride under mild conditions to give the imide-substituted product Ir(C H O{N[C(O)Ph] -2}{OMe-7})Cl(PPh ) (13). Selective mono-acylation of 6 can be achieved with one equivalent of benzoyl chloride or with excess of the sterically congested pivaloyl chloride.

Rhodapentalenes: Pincer Complexes with Internal Aromaticity

“…More interestingly, dearomatization/aromatization reactions can also be realized in rhodapentalene system. In this context, previous reported metallapentalynes (Zhu et al., 2013, Zhu and Xia, 2018, Zhuo et al., 2018), metallapentalenes (Zhu et al., 2014), and other bridge-headed fused metalla-aromatic compounds (Frogley et al., 2018, Frogley and Wright, 2014, Frogley and Wright, 2017, Wang et al., 2012, Wang et al., 2013) could also be regarded as pincer complexes with internal aromaticity. We believe that these conceptually new pincer complexes, which combine the structural features of both aromatic compounds and rigid pincer complexes would provide new opportunities for pincer chemistry.…”

Synthesis and Characterization of Photothermal Osmium Carbolong Complexes

“…The most interesting feature is the presence of a nitro group on the phenyl group attached at C12 of the metallacycle, supporting the incorporation of an organic functional group. The nitro group of metallaaromatics has been used to prepare amino‐containing metallaaromatics …”

Direct amidation of metallaaromatics: access to N-functionalized osmapentalynes via a 1,5-bromoamidated intermediate

“…27 The Os1-Br1 bond length (2.7241(5) A) was slightly shorter than that of the reported metallabromirenium (2.8254(12) A), demonstrating the stronger interaction between the bromide atom and the metal center. The other metal-carbon bonds, Os1-C4 (2.146(5) A) and Os1-C7 (2.023(5) A) and the C-C bond lengths 5), Os1-C4: 2.146( 5), Os1-C7: 2.023( 5), Os1-Br1: 2.7241( 5), C1-Br1: 1.896( 5), C1-C2: 1.366( 7), C2-C3: 1.425( 7), C3-C4: 1.377( 7), C4-C5: 1.414( 7), C5-C6: 1.393( 7), C6-C7: 1.389( 7), C5-N1: 1.379( 7), C4-Os1-C1: 68.38( 19), C7-Os1-C4: 74.12( 19), Os1-C1-Br1: 90.2( 2), Br-Os1-C1: 44.10( 13), Os1-Br1-C1: 45.67 (15). (1.366-1.425 A) are within the range observed for 2a and other osmapentalenes, 19a suggesting the rearomatization of 4a.…”

“…4 X-ray crystal structure of the cation of 4a (thermal ellipsoids are set at the 50% probability level and the phenyl groups in the PPh 3 moieties are omitted for clarity). Selected bond lengths [ A] and angles [ ]: Os1-C1: 1.949(5), Os1-C4: 2.146(5), Os1-C7: 2.023(5), Os1-Br1: 2.7241(5), C1-Br1: 1.896(5), C1-C2: 1.366(7), C2-C3: 1.425(7), C3-C4: 1.377(7), C4-C5: 1.414(7), C5-C6: 1.393(7), C6-C7: 1.389(7), C5-N1: 1.379(7), C4-Os1-C1: 68.38(19), C7-Os1-C4: 74.12(19), Os1-C1-Br1: 90.2(2), Br-Os1-C1: 44.10(13), Os1-Br1-C1: 45.67(15).…”