Synthesis and Reactivity of Sterically Encumbered Diazaferrocenes

Abstract

Bulky pyrrolyl ligands have been used for the synthesis of diazaferrocenes, which have been characterized by various spectroscopic techniques, including X-ray diffraction for rac-[{η5-2,3,5-(Me3C)3C4HN}2Fe]. Chemical oxidation of diazaferrocenes to the corresponding diazaferrocenium cations has been accomplished with AgSbF6. In addition, EPR and Mössbauer spectroscopic, electrochemical, and density function theory (DFT) studies have provided a more detailed understanding of the electronic structures of these complexes.

Reactivity studies on [Cp′Fe(μ-I)]2: nitrido-, sulfido- and diselenide iron complexes derived from pseudohalide activation

“… 8 For comparison, the Cp′ cent –Fe distances in [Cp′ 2 Fe] ( S = 0) and [Cp′ 2 Fe][SbF 6 ] ( S = 1/2) are significantly shorter at 1.72 Å ( ref. 5 ) and 1.77 Å, 10 respectively. The spin state assignment in 2 is further substantiated by solid-state magnetic susceptibility data, which indicate antiferromagnetic coupling between the two Fe( ii ) ( S = 2) centers at low temperature ( Fig.…”

Coordination chemistry of sterically encumbered pyrrolyl ligands to chromium(ii): mono(pyrrolyl)chromium and diazachromocene formation

“…For Cr(II), η 5 -coordination of pyrrolyl ligands is rarely observed and requires the functionalization of the N-lone pair, e.g., by methylation 24 or coordination by Lewis-acids such as AlMe 3 . 25 However, based on our previous investigations on azatrozircenes 22 and diazaferrocenes 23 we anticipated that the sterically encumbered pyrrolyl ligands 1-3 would behave similarly to their cyclopentadienyl analogues. Indeed, the reaction of pyrrolides 1-Na, 2-K and 3-K with CrCl 2 in a 2 : 1 ratio in THF yields the corresponding red bis( pyrrolyl)chromium(II) complexes 1-Cr, 2-Cr and 3-Cr, respectively (Scheme 1).…”

“…6,7,19,20 Recently, we have initiated a research program on sterically encumbered pyrrolyl systems with an emphasis on comparing them with their cyclopentadienyl analogues, with respect to their ability to stabilize halfsandwich complexes. [21][22][23] Herein, we report our observations on the coordination chemistry of bulky pyrrolyls (Chart 1) with Cr(II) and briefly discuss the reactivity of pyrrolyl chromium(II) half-sandwich complexes in the polymerization/oligomerization of ethylene.…”

Phosphine-substituted sterically encumbered pyrrolyl ligands – synthesis and reactivity studies

“…s, 1H, NH), 7.63-7.58 (m, 4H, ortho-CH-Ph), 6.82-6.77 (m, 4H, meta-CH-Ph), 6.74-6.71 (m, 2H, para-CH-Ph), 6.59 (dd, 4 J HH = 3.0 Hz, 3 J PH = 7.1 Hz, 1H, CH-Pyr, 1.18 (s, 9H, C-5-C(CH 3 ) 3 , 0.91 (s, 9H, C-2-C(CH 3 ) 3 ,) ppm. 13 (53,46), 603.1 (40,38), 597 (36,34), 596.1 (17,17), 604.1 (12,15), 605.1 (1,1). IR (ATR; cm −1 ): 3481 (m, NH), 2066 (m, CO), 1927 (sh, CO), 1907 (vs.br, CO).…”

“…34 In our previous contributions we reported on the synthesis of several sterically encumbered pyrrolyls and the subsequent synthesis of several azatrozircenes [(η 7 -C 7 H 7 )Zr(η 5 -Pyr′)] 36,37 and more recently of diazaferrocenes. 38 Herein, we detail the synthesis of phosphinesubstituted pyrroles (Fig. 1), their electronic properties and coordination chemistry with molybdenum and manganese.…”