New Synthetic Route for Cobalt(III) Dissymmetric Bisalkynyl Complexes Based on Cobalt(III)(cyclam)(C₂NAP^Mes)

Abstract

The synthesis and characterization of dissymmetric Co III -bis-alkynyl complexes supported by cyclam (1,4,8,11-tetraazacyclotetradecane) are reported. A series of trans-[Co(cyclam)-(C 2 NAP R )Cl]Cl were prepared from the reaction between [Co-(cyclam)Cl 2 ]Cl and HC 2 NAP R in the presence of Et 3 N, where NAP R is N-R-1,8-naphthalimide with R as mesityl (Mes, 1a), methyl (Me, 1b), 1-ethylpropyl (Pen, 1c), 2-ethylhexyl (2-ethhex, 1d), or noctyl (Oct, 1e). Treating compounds 1a and 1b with AgOTf in [a] Dr. 4766Scheme 3. i.) 3 equiv. H 2 NR, ethanol/2-propanol, reflux, 18-84 h; ii.) 2-3 equiv. HC 2 SiMe 3 , iPr 2 NH, 2 mol-% CuI, 2 mol-% Pd(PPh 3 ) 2 Cl 2 , 20 min-2 h; iii.) excess K 2 CO 3 , MeOH, 30 min.

Co(cyclam) Complexes of Triarylamine-acetylide: Structural and Spectroscopic Properties and DFT Analysis

“…19−21 Recent efforts led to the preparation of [Co(cyclam)-(C 2 NAP R )Cl]Cl (NAP R = N-R-1,8-naphthalimide with R as isopropyl, NAP iPr , and mesityl, NAP Mes ) with a focus on the NAP R moiety as an emissive electron acceptor. 22,23 Explored in this study are the [Co(cyclam)(C 2 TPA)Cl] + and [Co-(cyclam)(C 2 TPA) 2 ] + type compounds with HC 2 TPA as 4ethynyl-N,N-bis(4-methoxyphenyl)aniline. Triarylamines (Ar 3 N) are excellent electron donors and exhibit a reversible one-electron oxidation that is accompanied by drastic changes in electronic absorption spectra, the latter of which has been frequently exploited in probing both organic 24−26 and organometallic mixed valency through spectroelectrochemical investigation.…”

Further Studies of CoIII(TIM) Mono‐Alkynyl and Bis‐Alkynyl Complexes

“…While 4 a was produced via a similar procedure, the yield was extremely low. Factors contributing to the poor yield include the formation of a byproduct [Et 3 NC 2 H 2 NAP Mes ]PF 6 via hydroamination of HC 2 NAP Mes by Et 3 N [13] and the solubility issues of HC 2 NAP Mes (insoluble in CH 3 OH) and [Co(TIM)Cl 2 ]PF 6 (insoluble in THF). Further compounding the issue is the closeness in R f values of 4 a and [Et 3 NC 2 H 2 NAP Mes ]PF 6 on silica, which foils bulk purifica-tion.…”

“…Consistent with previous studies, [12] the averaged Co−N bond lengths in complexes 3 a , 4 a , and 4 c are slightly contracted with a range of 1.915–1.921 Å relative to their respective cyclam‐based analogues, [Co(cyclam)(C 2 C 6 H 4 ‐4‐NO 2 )Cl] + , [15] [Co(cyclam)(C 2 NAP Mes )Cl] + , and [Co(cyclam)(C 2 NAP Mes ) 2 ] + , [13] which exhibit an averaged Co−N bond length range of 1.977–1.978 Å. This shortening of around ∼0.06 Å can be attributed to the σ‐donor strength and π‐accepting capabilities of the α‐diimine units.…”

“…Additionally, these antibonding interactions are further alleviated by the strong interactions between the π*(imine) orbitals and the Co dπ orbitals as indicated by the ca. 0.07 Å shortening of the Co−C(≡C) bond in 4 c when compared to the cyclam‐based analogue [13] …”

“…Synthesis of complexes 1-4; i) HC 2 R; Et 3 N, MeOH; reflux under N 2 ; ii) AgOTf, CH 3 CN; iii) HC 2 R, Et 3 N, CH 3 CN, under N 2 . respective cyclam-based analogues, [Co(cyclam)(C 2 C 6 H 4 -4-NO 2 )Cl] + , [15] [Co(cyclam)(C 2 NAP Mes )Cl] + , and [Co-(cyclam)(C 2 NAP Mes ) 2 ] + , [13] which exhibit an averaged CoÀ N bond length range of 1.977-1.978 Å. This shortening of around ~0.06 Å can be attributed to the σ-donor strength and πaccepting capabilities of the α-diimine units.…”