Stable N‐Heterocyclic Germylenes of the Type [Fe{(η⁵‐C₅H₄)NR}₂Ge] and Their Oxidation Reactions with Sulfur, Selenium, and Diphenyl Diselenide

Abstract

Three new N-heterocyclic germylenes of the type [Fe{(η 5 -C 5 H 4 )NR} 2 Ge] (1RGe) containing particularly bulky alkyl [R = 2-adamantyl (Ad), 1,1,2,2-tetramethylpropyl (Pr*)] or aryl substituents [R = 2,6-diisopropylphenyl (Dipp)] were prepared and structurally characterized, in two cases (R = Ad, Dipp), by singlecrystal X-ray diffraction. Together with the previously described homologues with R = trimethylsilyl (TMS), tert-butyl (tBu), and mesityl (Mes) their oxidative addition reactions with S 8 and Se 8 were studied, which afforded compounds of the type [1RGe(μ-E)] 2 (E = S, Se). The low solubility of most of these products severely hampered * Prof. Dr. U. Siemeling

Oxidation Reactions of the N‐Heterocyclic Stannylenes [o‐C6H4(NSitBuMe2)2]Sn and [{Fe(η5‐C5H4‐NSitBuMe2)2}Sn] with Sulfur, Selenium, and Diphenyl Diselenide

“…The product was obtained in 96 % yield as a crystalline solid, which was structurally characterized by X‐ray diffraction (vide infra). The 119 Sn NMR spectrum exhibits a signal at δ = 550 ppm in C 6 D 6 , which is close to the chemical shift values reported by us for the tert ‐butyl and trimethylsilyl homologues ( δ = 544 and 589 ppm for [{Fe(η 5 ‐C 5 H 4 ‐N t Bu) 2 }Sn] and [{Fe(η 5 ‐C 5 H 4 ‐NSiMe 3 ) 2 }Sn], respectively)[11b], [11c] and lies in the region typical for N‐heterocyclic stannylenes with strictly two‐coordinate Sn II according to X‐ray diffraction results . For comparison, δ ( 119 Sn) = 456 ppm has been reported for [ o ‐C 6 H 4 (NSi t BuMe 2 ) 2 ]Sn ( 2 ) .…”

“…Interestingly, short intramolecular CH ··· Se contacts similar to that of ( 1 Se) 2 , together with unexpected structural distortions, were recently found by us in the analogous germanium compounds [{Fe(η 5 ‐C 5 H 4 ‐N R ) 2 }Ge(μ‐Se)] 2 ( R = C t BuMe 2 , 2‐adamantyl). [11a] The different Sn– E bond lengths determined for E = S (average value 2.42 Å) and Se (average value 2.54 Å) are in accord with the difference of the single bond covalent radii of 0.13 Å reported for these elements and compare well with corresponding data published for closely related compounds. [14a], [14b], [14e], [14f],…”

“…[29b], [29c] In contrast, the neopentyl homologue of 2 is aggregated as a head‐to‐tail dimer in the solid state . The ferrocene‐based compounds in Table exhibit rather small cyclopentadienyl ring tilt and N–C ipso –C ipso –N torsion angles, pointing to essentially unstrained and nearly eclipsed 1,3,2‐diazastanna[3]ferrocenophane structures, as has been observed before by us for [{Fe(η 5 ‐C 5 H 4 ‐N R ) 2 }Sn] ( R = SiMe 3 , t Bu)[11b], [11c] and by Wrackmeyer et al for the tin(IV) compounds [{Fe(η 5 ‐C 5 H 4 ‐NSiMe 3 ) 2 } 2 Sn] and [{Fe(η 5 ‐C 5 H 4 ‐NSiMe 3 ) 2 }SnCl 2 ] …”

“…As a final point, we note that the short intramolecular CH ··· Se contact compatible with a hydrogen bond, which we observed for ( 1 Se) 2 is consistent with our recent findings concerning the occurrence of such contacts in selenium derivatives of ferrocene‐based N‐heterocyclic germylenes. [11a]…”

“…In continuation of our work on stable ferrocene‐based NHCs, we have established heavier analogues of the type [{Fe(η 5 ‐C 5 H 4 ‐N R ) 2 } E ] (E = Si, Ge, Sn,[11b], [11c] Pb),which constitute the first N‐heterocyclic tetrylenes bearing redox‐active substituents . We recently reported on the reactivity of several germylenes of this family in oxidation reactions with elemental sulfur, selenium, and diphenyl diselenide,[11a] and have started to extend this work in a systematic study to corresponding stannylenes and plumbylenes. We chose the hitherto unknown compound [{Fe(η 5 ‐C 5 H 4 ‐NSi t BuMe 2 ) 2 }Sn] ( 1 ) as starting point for our investigation of oxidation reactions of ferrocene‐based stannylenes with sulfur, selenium, and diphenyl diselenide.…”