Synthesis and Characterization of Stable Ruthenabenzenes

Abstract

Transition-metal-containing metallabenzenes [1][2][3] are an interesting class of compounds because they exhibit chemical properties of both organometallic compounds [1] and aromatic organic compounds. [1,4] The first stable transition-metal-containing metallabenzenes were reported in 1982 by Roper et al. [5] Since then a number of stable metallabenzenes have been successfully isolated and characterized. Most of the wellcharacterized stable metallabenzenes are those with a transition metal atom from the third transition series, especially osmium, [4][5][6][7] iridium, [2a-d, g-h, 8] and platinum. [2e, 9] In contrast, well-characterized metallabenzenes with a metal atom from the first or the second transition series are still very rare, although such species was predicted theoretically as early as 1979.[10] Although coordinated metallabenzenes with metal atoms from the first [11] and the second [12,13] transition series and 1,3-dimetallabenzenes [14] of Nb and Ta were isolated and well characterized, free metallabenzenes with a metal atom from the first or the second transition series have been isolated rarely. The ruthenabenzene [CpRu{C(Ph)CHCHC-(Ph)C(OEt)}(CO)] (Cp = cyclopentadienyl), and related ruthenaphenoxide and ruthenaphenanthrene oxide reported by Jones and co-workers represent rare examples (and the only reported examples, to the best our knowledge) of spectroscopically characterized metallabenzenes with a metal from the second transition series.[15a] However, these species are thermally unstable at ambient temperature. Other metallabenzenes such as ferrobenzene, [16a] ruthenaphenanthrene, [15a] ruthenaphenol, [15b] and chromobenzene [16b] have been proposed as reactive intermediates, but no direct observation of such species have been made. Herein we report the isolation and characterization of thermally stable ruthenabenzenes.We recently reported a convenient method for the preparation of osmabenzenes starting from the reactions of [OsCl 2 (PPh 3 ) 3 ] with HC CCH(OH)C CH. [7] We found that the method can also be used to prepare ruthenabenzenes. Treatment of [RuCl 2 (PPh 3 ) 3 ] (1) [17] with HC CCH(OH)C CH, PPh 3 , and Bu 4 NCl in THF produced cationic ruthenabenzene 2, which was isolated as a green solid in 55 % yield (Scheme 1). Interestingly, 2 can even be obtained from the one-pot reaction of RuCl 3 , PPh 3 , and HCCCH(OH)CCH in CHCl 3 , although the yield is lower.Complex 2 was characterized by solution NMR spectroscopy and elemental analysis. The 31 P{ 1 H} NMR spectrum in CDCl 3 showed two singlets at d = 18.2 and 8.1 ppm (CPPh 3 and RuPPh 3 , respectively). The presence of the metallacycle is clearly indicated by the 1 H and 13 C NMR data. In particular, the 1 H NMR spectrum in CDCl 3 showed the characteristic signal for RuCH at d = 17.5 ppm and for g-CH at d = 8.2 ppm. The 1 H NMR chemical shift for RuCH (d = 17.5 ppm) is significantly downfield relative to that for the vinyl complex [Ru{CH = CH(C 6 H 4 -p-OMe)}Cl(CO)(PPh 3 ) 2 ] (d = 8.13 ppm), [18] but is close to those for ruthenium...

Synthesis, Characterization and Electrochemical Properties of Stable Osmabenzenes Containing PPh3 Substituents

“…The lack of significant alternations in the CC bond lengths suggests that 14 still has a delocalized structure. Similar delocalized metallabenzene structure without a planar metallacycle occurred in our previously reported ruthenabenzene with a 2,2′‐dipyridyl ligand 11b,c. Although not common, a few nonplanar metallabenzenes are known 3d.…”

Synthesis and Characterization of a Rhenabenzyne Complex

“…In particular metallabenzenes, which are organometallic compounds derived by the formal replacement of a C À H group in benzene with an isolobal transition metal fragment, have attracted considerable attention. [1] Previous studies have led to the isolation and characterization of an impressive number of stable metallabenzenes, especially those of osmium, [2][3][4] iridium, [5][6][7][8] platinum, [9] ruthenium, [10,11] and rhenium. [12] Metallabenzynes, [13] which are organometallic compounds derived from formal replacement of a carbon atom or a CÀH group in benzyne with an isolobal transition metal fragment, are closely related to metallabenzenes.…”

A Metallanaphthalyne Complex from Zinc Reduction of a Vinylcarbyne Complex

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Transition metal containing metallaaromatics are a fascinating class of compounds because they can show properties of both organometallic compounds and aromatic organic compounds. [5] Other interesting metallaaromatics and related compounds isolated in recent years include metallanaphthalene, [6] metallapyrylium, [7] metallathiabenzene, [8] metallapyridine, [9] metallabenzyne, [10] isometallabenzene, [11] and metallabenzvalene. [5] Other interesting metallaaromatics and related compounds isolated in recent years include metallanaphthalene, [6] metallapyrylium, [7] metallathiabenzene, [8] metallapyridine, [9] metallabenzyne, [10] isometallabenzene, [11] and metallabenzvalene.

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