Synthesis, Molecular Structure and Properties of a Ferrocene‐Based Difluoropyrrolo‐Oxaborole Derivative

Abstract

Reaction of 1,1′‐ferrocenedicarbonyl chloride with 3‐ethyl‐2,4‐dimethylpyrrole in DCM produced the half‐way product, namely, the ferrocene bis(2‐ketopyrrole) derivative 2 and not the expected bis(dipyrromethene) compound. The 2‐ketopyrrole compound readily reacted with BF3·Et2O to produce the bis(difluoropyrrolo)‐oxaborole compound, FBF, as a red/brown solid which was characterised by X‐ray crystallography. 57Fe Mössbauer spectra for 2 and FBF were consistent with low‐spin iron(II) (d6) ferrocene derivatives. A cyclic voltammogram for 2 in acetonitrile revealed a reversible wave at +0.31 V vs. Fc+/Fc (ferrocene‐based) and an irreversible wave at –2.38 V vs. Fc+/Fc (ketopyrrole‐based). The electrochemical behaviour is severely perturbed by the chelation of the BF2 groups. Alterations to the electronic properties of 2 by formation of FBF are also evident in the absorption profiles. DFT calculations [B3PW91, 6‐31G(3df)] support the observed changes in the electrochemistry findings and the Mössbauer spectroscopic data.

Synthesis and Characterization of Ferrocenyl Chlorins, 1,1′-Ferrocene-Linked Chlorin Dimers, and their BODIPY Analogues

“…Two alternatives were explored, and the protocol avoiding formylation of the Fcsubstituted dipyrromethane again proved superior. Briefly, monoformylation of both dipyrromethane units in 8 40 (available from 7) to 9 proceeded in 22% yield. The mass balance is accounted for by decomposed starting material and small amounts of overformylated products.…”

“…High-resolution mass spectral analyses (HRMS) were performed at the Organisch Chemisches Institut WWU Münster. Compounds 2 , 5 , 5 CHO , and 8 were prepared according to literature procedures. The X-ray crystal structure was solved using direct methods in the monoclinic space group P 2 1 / n (No.…”

Benchmarking DFT Calculations of 1H and 13C Chemical Shifts in Monosubstituted Ferrocenes

“…The experimental chemical shifts were obtained from the literature: ferrocene ( a ), [ 98–99 ] methylferrocene ( b ), [ 100 ] ethylferrocene ( c ), [ 101 ] phenylferrocene ( d ), [ 102–103 ] 4‐iodophenylferrocene ( e ), [ 104 ] ethynylferrocene ( f ), [ 105 ] ferrocenylmethanol ( g ), [ 106 ] 1‐ferrocenylethanol ( h ), [ 107 ] N , N ‐dimethylaminomethylferrocene ( i ), [ 108 ] formylferrocene ( j ), [ 108 ] ferrocenecarboxylic acid ( k ), [ 109 ] acetylferrocene ( l ), [ 108 ] N , N ‐dimethylferroceneamide ( m ), [ 106 ] fluoroferrocene ( n ), [ 110–111 ] chloroferrocene ( o ), [ 112 ] bromoferrocene ( p ), [ 112 ] trimethylferrocenylphosphonium hexafluorophosphate ( q ), [ 113 ] iodoferrocene ( r ), [ 112 ] cyanoferrocene ( s ), [ 114 ] ferroceneboronic acid ( t ), [ 115 ] 1,1′‐dimethylferrocene, [ 116–117 ] 1,1′‐diphenylferrocene, [ 118 ] 1,1′‐ferrocenediboronic acid, [ 118 ] 1,1′‐ferrocenedicarboxylic acid, [ 119–120 ] 1,1′‐diacetylferrocene, [ 120–121 ] 1′‐trimethylsilylethynyl‐1‐ethynylferrocene, [ 122 ] 1′‐bromo‐1‐ferrocenylcarboxylic acid, [ 123 ] and decamethylferrocene. [ 124 ] The extracted data are given in Tables S10 and S14.…”