Releasing Antiaromaticity in Metal-Bridgehead Naphthalene

Abstract

As a fundamental chemical property, aromaticity guides the synthesis of novel structures and materials. Replacing the carbon moieties of aromatic hydrocarbons with transition metal fragments is a promising strategy to synthesize intriguing organometallic counterparts with a similar aromaticity to their organic parents. However, since antiaromaticity will endow compound instability, it is a great challenge to obtain an antiaromatic organometallic counterpart based on such transition metal replacement in aromatic hydrocarbons. Here, we report an efficient aromaticity transformation on aromatic naphthalene through the bridgehead replacement of an osmium fragment, leading to the unprecedented synthesis of metal-bridgehead naphthalene featuring a highly twisted structure as confirmed by X-ray crystallography characterization. Such a twisted conformation works together with its phosphonium substituents to release the antiaromaticity in the planar conformation of the metal-bridgehead naphthalene. Our findings prove the bridgehead involvement of transition metals in unexpected aromaticity modifications and open an avenue for novel metal-bridgehead complexes.

Dissimilarity in the Chemical Behavior of Osmaoxazolium Salts and Osmaoxazoles: Two Different Aromatic Metalladiheterocycles

“…This class of metallaaromatic compounds should add organometallic reactivity to the reactions of the starting aromatic organic molecules. Since the prediction of the metallabenzenes by Thorn and Hoffmann in 1979 and the preparation of the first osmabenzene by Roper and co-workers in 1982, the chemistry of these types of compounds has experienced a tremendous development, mainly from a conceptual point of view . Most of the effort has been centered on the metal counterparts of hydrocarbons: i.e., metallabenzenes, metallabenzynes, metallanaphthalenes, metallaanthracenes, metalloles, and some condensed species bearing the metal bonded to four carbons such as carbolongs and spiro metalloles .…”

One‐Pot Synthesis of High‐Strained Metal Vinylidene and Metal Carbyne

“…[13,16,17,20] In the pursuit of efficient methods to synthesize metallacycles, we recently developed a strategy which utilizes various multiynes as a carbon ligand platform to prepare a wide variety of metallacycles. [36][37][38][39][40][41][42][43] From extensive experimentation with various multiynes, we identified an optimal combination of alkynyl and phenyl components for construction of the desired metal vinylidene motif within a fused ring system. Reaction of 1 with OsCl 2 (PPh 3 ) 3 under an oxygen atmosphere at room temperature (RT) in 3 h quantitatively spectroscopic yield affords a metal vinylidene complex 2, which could be isolated in 85 % yield as a brown powder (Scheme 2a).…”

“…Isomerization of π‐alkyne complexes derived from terminal alkynes to generate a number of metal vinylidene complexes has been studied extensively [13,16,17,20] . In the pursuit of efficient methods to synthesize metallacycles, we recently developed a strategy which utilizes various multiynes as a carbon ligand platform to prepare a wide variety of metallacycles [36–43] . From extensive experimentation with various multiynes, we identified an optimal combination of alkynyl and phenyl components for construction of the desired metal vinylidene motif within a fused ring system.…”

A One‐Pot Strategy for the Synthesis of β‐Substituted Rhoda‐ and Irida‐Carbolong Complexes

“…Four classes of carbolong complexes, namely osma‐, ruthena‐, rhoda‐ and irida‐carbolong complexes, are now available, according to their different metal centers. [ 51 ] Compared to the rich and well‐studied chemistry of group 8 metal‐based carbolong complexes, [ 51‐62 ] the research on those based on group 9 metals is far less. [ 63‐67 ]…”