Organometallic .pi. complexes. XXII. Chemistry of .pi.-cyclopentadienyltetraphenylcyclobutadienecobalt and related compounds

Abstract

The reaction of -cyclopentadienyldicarbonylcobalt and diphenylacetylene in refluxing xylene products ircyclopentadienyltetraphenylcyclobutadienecobalt (1) and ?r-cyclopentadienyltetraphenylcycIopentadienonecobalt (2) in yields of 50 and 10%, respectively. This method has also been extended to the direct synthesis of the corresponding trimethylsilyl (3, 5) and phenyl (4, 6) derivatives, starting with trimethylsilylor phenylcyclopentadiene. The 7r-cyclopentadienyl ring in 1, as in ferrocene, undergoes a number of electrophilic ring substitution reactions. Acetoxymercuration with a perchloric acid catalyst, followed by treatment with lithium chloride, produces a chloromercuri derivative 7 in 65% yield, together with a l,2-bis(chloromercuri) derivative 8. Complex 7 is readily converted into its iodo analog 9. The transmetalation of 7 with n-butyllithium gives a lithium intermediate 10 which on treatment with acetyl chloride affords the acetyl derivative 11. When 9 is heated with copper-bronze or with cuprous cyanide in A-methyl-2-pyrrolidone, the Ullmann product 12 and the cyano derivative 13 are obtained. Similar reactions with cupric acetate and cupric phthalimide produce acetate 14 and phthalimido IS derivatives, respectively, which on hydrolysis give phenol 16 and amine 17. The relative acidity and basicity of these products have been determined. Aminomethylation and Vilsmeier formylation give dimethylaminomethyl (18) and formyl (20) derivatives in yields of 74 and 8%, respectively. The conclusion is drawn that•, while 1 participates in a variety of electrophilic substitution reactions, if is in general less reactive than is ferrocene.Although the concept of aromaticity is still not well defined, ferrocene and related organometallic compounds are generally considered "aromatic" in that they resist ring-addition reactions and undergo ring-substitution reactions. Thus, ferrocene is known to undergo various electrophilic substitution reactions such as Friedel-Crafts acylation,2 alkylation,3•4 formylation,6-7 sulfonation,8-10 acetoxymercuration,11•12 and aminomethylation.13 Following these initial studies on ferrocene, various other organotransition metal compounds containing a -cy clopentadieny 1 ring were found to exhibit similar chemical reactivities. Thus, ruthenocene,14 osmocene,14 cymantreñe,15-18 and its technitium19 and rhenium19•20 analogs, -cyclopentadienyltetracarbonylvanadium,21•22 and -cyclopenta-(1) Alexander von Humboldt Research Fellow, 1969-1970

Replacement of One CO Unit in Dicarbonyl(η5-cyclopentadienyl)cobalt Derivatives by Bis(tert-butylsulfonyl)acetylene

“…So far, substitution reactions at dicarbonyl(η 5 -cyclopentadienyl)cobalt [CpCo(CO) 2 ] (1) [1] [2] [3] with alkynes could not be stopped at the monosubstitution stages, although such complexes have been postulated as intermediates. [4] In the reported cases follow-up reactions led to cyclobutadiene complexes, cyclopentadienone complexes or benzene derivatives.…”

“…In this paper we report experiments with 1 [3] and the substituted congeners dicarbonyl(η 5 -methylcyclopentadienyl)-(2) [14] , dicarbonyl(η 5 -trimethylsilylcyclopentadienyl)- (3) [15] [16] , dicarbonyl(η 5 -methoxycarbonylcyclopentadienyl)-(4) [17] , dicarbonyl-(η 5 Ϫ1-ethyl-2,3,4,5-tetramethylcyclopentadienyl)-(5) [18] [19] , and dicarbonyl(η 5 -pentaallylcyclopentadienyl)cobalt (6) [20] .…”

Reactions of n-C5H5Co(CO)2 and n-Me3SiC5H4Co(CO)2 with (XCN)2 and X(CN)2 (X = S or Se)

“…The cyclopentadienyls Me3SiC5H5 [22], r?-C5H5Co(CO)2 [23], 7?-Me3SiC5H4Co(CO)2 [10], and the pseudohalogens (SeCN)2 [24], (SCN)2 [25], Se(CN)2 [26] and S(CN)2 [27] were prepared by published procedures. The microanalyses were performed by the Centro Nacional de Quimica Organica (Madrid, Spain).…”

Oxidative Addition Reactions of P(CN)3, P(NCO)3 and P(NCS)3 to (η5-C5Me5)Co(CO)2

“…The pentam ethylcyclopentadiene [14], [15] and the reactants P(CN ) 3 [9], P (N C O ) 3 [10], P(NCS) 3 [11] were prepared by the published procedures. The cobalt was determ ined by titration of the Co-E D T A complex in presence of NET as indicator.…”