Group VII metal complexes

The Ti -coordinated Mn(CO)3 cationic complexes of thiophenes follow mainly from the direct interaction of a heterocyclic ligand with Mn(CO)5X (81HCA1288). The first successful synthesis of 79 (R = = H = Me, R = R = 

Complexes 79 show several types of chemical reactions (87CCR229). Nucleophilic addition may proceed at the C2 and S atoms. In excess potassium cyanide, 79 (R = R = R = R = H) forms mainly the allyl sulfide complex 82 (R = H, Nu = CN) (84JA2901). The reaction of sodium methylate, phenyl-, and 2-thienyllithium with 79 (R = R = r = R = H) follows the same route. The fragment consisting of three coplanar carbon atoms is described as the allyl system over which the Tr-electron density is delocalized. The sulfur atom may participate in delocalization to some extent. Complex 82 (R = H, Nu = CN) may be proto-nated by hydrochloric acid to yield the product where the 2-cyanothiophene has been converted into 2,3-dihydro-2-cyanothiophene. The initial thiophene complex 79 (R = R = r = R = H) reacts reversibly with tri-n-butylphosphine followed by the formation of 82 [R = H, Nu = P(n-Bu)3]. Less basic phosphines, such as methyldiphenylphosphine, add with much greater difficulty. The reaction of 79 (r2 = r3 = r4 = r5 = h) with the hydride anion [BH4, HFe(CO)4, HW(CO)J] followed by the formation of 82 (R = Nu, H) has also been studied in detail. When the hydride anion originates from HFe(CO)4, the process is complicated by the formation of side products 83 and 84. The 2-methylthiophene complex 79 

Organometallic nucleophilic reagents change the reaction pattern drastically. 

Passage of gaseous hydrogen chloride through a solution of 79 (R = R = r = R = H) causes formation of the reduced forms for which structures 89 and 90 

When acetylthiophenes are subjected to orthomanganation, formation of the 2,3-, 103, and 3,4-, 104, metallocycles is observed [88JOM(349)197]. Complex 103 contains two coplanar live-membered heterocycles with octahedral manganese. Complex 104 is also planar. In both cases, substantial delocalization of the TT-electron density follows from the structural parameters. 

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An important reaction of the carbonyl cations of Group VII metals is their base attack by alkoxides (135, 167, 168, 175), which has already been mentioned. The product is an alkoxycarbonyl complex. 

The possible intermediacy of the formate ion (eqs. 6 and 18) in the WGSR has been considered (2,6,10), but its involvement has not been clearly demonstrated. The Group VI metal carbonyl complexes are effective in the decomposition of formic acid (as sodium formate), as shown in Table VII. Some heterogeneity is observed in those reactions carried out under nitrogen pressure, but in no case was CO detected. The similarity in rates for WGSR... 

Hydrogenation Catalysts Based on Groups V-VII Transition-Metal Complexes 137... 

Table 6.19 Hydrogenation catalysts based on Group V-VII transition-metal complexes activated with AI / B u 3.

Osmium(iv).—Group VII Donors. Simple syntheses of hexafluoro-complexes of some noble metals have been reported, e.g. 

Platinum(iv).—Group VII Donors. Simple syntheses of hexafluoro-complexes of some noble metals have been reported, including K2[PtF ]. The method involved the melt reaction between KHFj and K2[PtXg] (X = Cl, Br, or I), which has the advantage of not requiring corrosive reagents such as fluorine or BF3- The stepwise stability constants K have been measured for the bromoaquo-complexes [PtBr , (H20)-7 ] "" (n = 4, 5, or 6) formed in... 

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