Cyclohexadienyl complexes

With OH and SH, the nucleophilic substitution of Cl has been reported. Thus, with NaOH, there is a report of successful nucleophilic substitution in 50% aq. acetone at room temperature to give the phenol complex in 36% yield. The latter is then spontaneously deprotonated to give the cyclohexadienyl complex (Eq. (24)). An identical reaction was carried out using NaSH in MeCN (50% yield) to give the thiophenol complex which was deprotonated [72] Eq. (25). These reactions would be especially valuable because direct synthesis of the phenol or thiophenol complexes from ferrocene is not possible due to the strong interaction between the heteroatom and A1C13 [11, 19]. Recent improvement and use of this reaction were achieved [88],... 

Recently, it was shown that the attack of CN on [FeCp(C6H5Cl)]+ PFortho-position. In the intermediate cyclohexadienyl complex, the CN group migrates to the ipso-carbon, whereas Cl is displaced. The monosubstituted benzonitrile complex is subjected to a second ortho-CN- attack but hydride is not removed spontaneously to give back an arene complex (Scheme XIX). Removal of the hydride is achieved by oxidation using DDQ (2,3-dichloro-... 

However, the hydride reduction of FeCp(arene)+ salts [124, 125] gives [FeCp(r 5-cyclohexadienyl)] complexes [125, 126] (via an ET mechanism [127] for the directing effect of substituents see Refs. [126, 128-130]. The electrochemical reduction of the carboxylic substituents at an Hg cathode in water leads to the primary alcohol [131-133] Eq. (39) ... 

Reduction of low-spin Fe(m) imide 165 with hydrogen (1 atm, 20 °C) proceeds stepwise leading first to anilido complex 168 and then to 77-cyclohexadienyl complex 169 via hydrogenolysis of the Fe=NR linkage (Scheme 64). It should be mentioned that the similar low-spin cobalt complex [PhB(CH2PPh2)3]Co N-/>-Tol is stable to hydrogen pressure (1-3 atm) up to 70 °C <2004JA4538>. 

Examples of reductive cluster-opening and oxidative cluster-closing reactions are common in the chemistry of metal-hydrocarbon tt complexes. For example, bases convert nido- (hexa-hapto)arene-manganese tricarbonyl complexes into aracAno(pentahapto)-7T-cyclohexadienyl complexes 129,130, 217) ... 

Triphenylmethyl fluoroborate will also abstract a hydride ion from tri-carbonyleyclohexa-l,3-dieneiron to give the cyclohexadienyl complex [Fe(CO)3(C H7)] BF4 (5,9, 76), analogous to the cycloheptadienyl complex [Fe(CO)3(C7H9)l BF4 described above. 

Reactions of the HNiL3CN complex with 1,3-cyclopentadiene, 1,3-cyclo-hexadiene, and 1,3-cyclooctadiene gave intermediates with decreasing stabilities in that order the 1,3-cyclooctadiene intermediate was not spectroscopically observable. The cyclohexadiene adduct was shown to be the cyclohexadienyl complex 12 by its proton spectra, with resonances of H , Hb, and —(CH2)3— at 14.53, 6.06, and 8.47, respectively these values are close to the chemical shifts found earlier (51) for 13 14.52,5.86, and 8.48. The reaction of DNi[P(OMe)3]X with cyclopentadiene gives 13-d, with addition of D and Ni to the same side of the ring (52). Backvall and Andell (55) have shown, using Ni[P(OPh)3]4 and deuterium cyanide (DCN), that addition of D and CN to cyclohexadiene is stereospecifically cis, as expected for jt-allyl intermediate 12. 

The first arene-transition metal complexes were prepared in the 1950s1314 and it was immediately recognized that the added polarizibility or electron deficiency would promote addition of nucleophiles to the arene ligand. A number of cyclohexadienyl complexes were characterized following nucleophilic addition, but the question of inducing the ipso hydrogen to depart was not answered (equation 1). 

A range of enolate nucleophiles have been added to trimethylsilyl-substituted cyclohexadienyl complexes (49 Scheme 18) and (51 equation 49) and related compounds. Again, high yields are obtained and stereodirection by the Fe(CO)3 group is very powerful.13... 

The addition reactions of hydride and several kinds of carbon nucleophiles to 125 provide an easy synthetic route to some new silatranyl j4-cyclohexadienyl complexes,... 

Cyclohexadiene-iron carbonyl complexes, [4+4]-cycloadditions, 10, 619 Cyclohexadienyl complexes... 

Arenes are inert to nucleophilic attack and normally undergo electrophilic substitution. However, arenes coordinate to Cr(CO)6 to form the i/fi-arenechromium tricarbonyl complex 79, and facile nucleophilic attack on the arene generates the anionic jy5-cyclohexadienyl complex 80, from which substituted arene 81, or cyclohexadiene is obtained by oxidative decomplexation. In this reaction, strongly... 

The reaction of halide anions with substituted carbonyl cations docs not appear to have been studied, but the reactions with cyanide (47) and hydride (245, 246) have been reported. Thus [Mn(CO)3C6H6]+ gives the cyclohexadienyl complex in which the hydride is in the endo position of the methylene group, (viz., Ha). 

Synthetically useful reactions of (arene)Mn(CO)3+ complexes with such nucleophiles as methoxide, benzenethiolate, azide, various amines, and anilines are also noteworthy. These complexes have also been extensively studied with regard to nucleophilic addition reactions resulting in thermally stable cyclohexadienyl complexes [2]. 

The synthesis of the zero-valent, 1,3-cyclohexadiene benzene ruthenium complex 196a has been mentioned as a coproduct of the cyclohexadienyl complex 236a in the reduction of the benzene ruthenium dication 235 with lithium aluminum hydride. Reduction of 235 with sodium borohydride in THF, however, gives only the air-sensitive, yellow-green ruthenium(O) complex 196a (118). This reaction has been generalized to... 

The more stable position for a electron-withdrawing group, such as carbomethoxy, is at C-3 of the starting cyclohexadienyl complexes, and terminal addition is again observed. Even the weak nncleophile, allylsilane, reacts at room temperature at the less-hindered terminal position (equation 86). 

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