Unexpected Dimerization of a Bis(fluorenyl)-bis(trimethylsilyl)-diallene to a Dihydroquatercyclopentadiene, an Octacyclic C₃₆ Fragment Corresponding to 60% of C₆₀: Reaction of the Diallene with Fe₂(CO)₉

Abstract

The propargylallene 3,3′-biphenylene-1-trimethylsilyl-1-(9-trimethylsilylethynyl)-9H-fluorenylallene, 12, undergoes thermal rearrangement in refluxing THF to the corresponding s-trans-bis(fluorenylidene)bis(trimethylsilyl)diallene, 13. In contrast, when thermolyzed in refluxing toluene, 12 cyclizes to form a cyclopentenylidene carbene that dimerizes to furnish the tetrabenzodihydroquatercyclopentadiene 15. Moreover, treatment of 13 with NaF yields C60H36, 17 (the “parent” analogue of 15), whose C36 backbone can be mapped onto C60 and which represents 60% of the fullerene framework. The ligands 12 and 13 both react with di-iron nonacarbonyl to produce the novel complex 21, in which an (η5-fluorenyl)Fe(CO)2 moiety is linked both directly and via a bridging carbonyl to a cyclopentadiene ring bearing two trimethylsilyl substituents and a spiro-bonded fluorenyl fragment. The proposed mechanism involves rearrangement of a coordinated trimethylsilylalkyne unit into a vinylidene complex prior to formation of the cyclopentadiene ring. However, the complex 21 is relatively unstable and undergoes oxidative decomposition with loss of iron and formation of a bicyclic lactone, 27, possessing two spiro-bonded fluorenyl groups. The X-ray crystal structures of 13, 15, 17, 21, and 27, as well as that of 1,4-bis(fluorenylidene)-2-butyne, 20, are reported.

A Synthetic and X‐ray Crystallographic Study of Zinc and Platinum Complexes of 4,5‐Diazafluoren‐9‐one (Dafone) and Dicobalt Hexacarbonyl Derivatives of 9‐Phenylethynyl‐4,5‐Diazafluoren‐9‐ol: Chelation versus Monocoordination

“…The asymmetry of the M-N bond lengths is clearly apparent in both cis-and trans-(dafone) 2 MX 2 complexes, and is particularly evident in d 9 Cu II systems in which geometric distortions are amplified by Jahn-Teller effects. [16] However, with larger metal ions in high oxidation states, such as Pt IV , dafone can function as a symmetrically bonded chelating ligand.…”

“…[8] Subsequent thermolysis of the allenes yields tetracenes 5. This general procedure has since been extended to include allene dimers containing halogens, and also silyl, [8,9] phosphane [10] and ferrocenyl [11] substituents.…”

From allenes to tetracenes: Syntheses, structures, and reactivity of the intermediates

“…However, attempted electrocyclization to the 3,4-bis(fluorenylidene)cyclobutene, 23, led instead to the novel dihydrotetrabenzo-quatercyclopentadiene, 24 [20]. In terms of a mechanistic hypothesis, one can visualize rotation about the central bond of the diallene, 22, and cyclization to form a cyclopentenylidene ring, 25, whereby the carbene is initially sterically protected by its very bulky trimethylsilyl and spiro-bonded fluorenyl neighbors.…”

The chemistry of bisallenes

“…The fully substituted bisallene with two internal trimethylsilyl substituents 86 was prepared by McGlinchey et al by a (2 × C 3 )-coupling route from the bromoallene 84 (Scheme 19) [68]. When 84 was heated with n -butyllithium in THF it dimerized to the unusual propargylallene derivative 85 , which, on slight heating (65 °C), isomerized to the bisallene 86 , which exists in the shown transoid conformation.…”

“…A most interesting electrocyclization/dimerization process has been discovered by McGlinchey and co-workers for the disilylated hydrocarbon 86 (Scheme 37; see also Scheme 19, Section 1.2) [68]. Heating the highly hindered conjugated bisallene 86 in toluene does not lead to the expected bismethylenecyclobutene 146 ; instead the isomerization takes a completely different course.…”