Reported herein is the synthesis and characterization of a series of monoand bis-alkynyl Co III (TIM) complexes, where TIM is 2,3,9,10-tetramethyl-1,4,8,11tetraazacyclotetradeca-1,3,8,10-tetraene. The trans-[Co(TIM)(C 2 Ar)Cl] + type complexes (Ar = phenyl (Ph, 1a), naphthalene (Np, 1b), and -C 6 F 5 (1c)) were prepared by the addition of HC 2 Ar to trans-[Co(TIM)Cl 2 ]PF 6 in the presence of Et 3 N. Treatment of the mono-alkynyl complexes with AgOTf in MeCN resulted in the trans-[Co(TIM)(C 2 Ar)-(NCMe)](OTf) 2 complexes (Ar = Ph (2a), Np (2b), and -C 6 F 5 (2c)). Complexes 2a and 2b react with the respective HC 2 Ar ligand in the presence of Et 3 N to afford the symmetrical bis-alkynyl complexes trans-[Co(TIM)(C 2 Ar) 2 ] + (Ar = Ph (3a) and Np (3b)). trans-[Co(TIM)(C 2 C 6 F 5 ) 2 ] + (3c) was obtained directly from the prolonged reaction of trans-[Co(TIM)Cl 2 ]PF 6 with HC 2 C 6 F 5 . Furthermore, the addition of HC 2 Ph to 2c in the presence of a weak base yielded the unsymmetrical bis-alkynyl complex trans-[Co(TIM)(C 2 C 6 F 5 )(C 2 Ph)]OTf (4). Molecular structures of complexes 1a/b, 2a/b, [3a]PF 6 , 3b, and 4 were established through single crystal X-ray diffraction. The absorption spectra for 1−4 display d−d bands between 380 and 470 nm. Complexes 1b−3b exhibited Np-based fluorescence. Electrochemical studies revealed that all complexes display an irreversible reduction characteristic of the Co III center, as well as up to two irreversible reduction(s) localized on the TIM macrocycle.

Reported herein is the formation of products containing a 1-aza-2-cobaltcyclobutene unit from the reaction between [Co III (TIM)Cl 2 ] + (TIM = 2,3,9,10tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) and electron-rich terminal alkynes (HC 2 Y). The trans-[Co(TIM′)((HCC)Y)Cl] + type complexes (Y = 4-N,Ndimethylaniline (DMAP; 1), ferrocene (Fc, 2a), and N,N-bis(4-methoxyphenyl)aniline (TPA; 3a) and TIM′ is the resultant derivative of TIM) were successfully prepared by the addition of HC 2 Y to trans-[Co(TIM)Cl 2 ]PF 6 in the presence of KOH. The occurrence of the 1-aza-2-cobalt-cyclobutene was confirmed through X-ray diffraction and 1 H NMR and IR spectroscopic characterizations, and its formation is enabled via a formal two-electron donation by TIM′ through the deprotonation of one of the TIM methyl groups.

The reaction between [CoIII(TIM)Cl2]PF6 (TIM is 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) and electron-rich terminal alkynes (HC2Y, Y = 4-N,N-bis(4-methoxyphenyl)aniline (TPA) or Fc) yielded a pair of constitutional isomers: 1-aza-2-cobalt-cyclobutene-containing trans-[Co(TIM′)((HCC)Y)Cl]+ (1a (TPA) and 2a (Fc); TIM′ is the resultant derivative of TIM) and σ-coordinated trans-[Co(TIM)(C2Y)Cl]+ (1b (TPA) and 2b (Fc)). Additionally, the reactivity of the 1-aza-2-cobalt-cyclobutene species was explored based on trans-[Co(TIM′)((HCC)Fc)Cl]PF6 (2a) because of its good synthetic yield. The reaction of 2a with AgOTf in MeCN resulted in trans-[Co(TIM′)((HCC)Fc)(NCMe)](PF6)(OTf) (3), and the reaction with KCN in MeOH yielded trans-[Co(TIM′)((HCC)Fc)CN]PF6 (4). Similarly, trans-[Co(TIM)(C2Ph)(CN)]PF6 (5) was prepared from the reaction between KCN and trans-[Co(TIM)(C2Ph)Cl]PF6. Molecular structures of 1b and 3–5 were established through single crystal X-ray diffraction. Electrochemical studies of 2–4 revealed that these complexes display an irreversible CoIII reduction as well as a reversible one electron ferrocenyl oxidation between 0.11 and 0.18 V (vs Fc+1/0). UV–vis spectroelectrochemical studies revealed a CoIII to Fc+ charge-transfer upon the one electron oxidation of 2a and 2b.

A new series of mono-and bis-alkynyl Co III (TIM) complexes (TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) is reported herein. The trans-[Co(TIM)(C 2 R)Cl] + complexes were prepared from the reaction between trans-[Co(TIM)Cl 2 ]PF 6 and HC 2 R (R = tri(isopropyl)silyl or TIPS (1), -C 6 H 4 -4-t Bu (2), -C 6 H 4 -4-NO 2 (3 a), and N-mesityl-1,8-naphthalimide or NAP Mes (4 a)) in the presence of Et 3 N. The intermediate complexes of the type trans-[Co(TIM)(C 2 R)(NCMe)](PF 6 )(OTf), 3 b and 4 b, were obtained by treating 3 a and 4 a, respectively, with AgOTf in CH 3 CN. Furthermore, bis-alkynyl trans-[Co-(TIM)(C 2 R) 2 ]PF 6 complexes, 3 c and 4 c, were generated following a second dehydrohalogenation reaction between 3 b and 4 b, respectively, and the appropriate HC 2 R in the presence of Et 3 N. These new complexes have been characterized using X-ray diffraction (2, 3 a, 4 a, and 4 c), IR, 1 H NMR, UV/Vis spectroscopy, fluorescent spectroscopy (4 c), and cyclic voltammetry.

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