Complexes mixed-ring sandwich

The metal-vapor technique was applied to cobalt atoms and r-BuC = P (01JOM(635)212). The mixture of products that resulted includes the mixed-ligand sandwiches 170 and 171. Further interaction of complex 170 with [W(C0)5(THF)] leads to the coordination of the W(CO)5-group via the phosphorus heteroatom of the four-membered ring to yield 172. 

The synthesis of the mixed-ring uranium(m) complex (COT)Cp U(THF) has been achieved by reaction of Cp UI2(THF)3 with K2(COT) in THF. Further treatment of (COT)Cp U(THF) with 4,4 -dimethyl-2,2 -bipyridine (Me2bipy) in toluene yielded the formally 10-coordinate complex (COT)Cp LJ(Me2bipy), which was structurally characterized by an X-ray analysis.152 The mixed-sandwich uranium(m) complex (COT)Cp U(HMPA) was isolated from the reaction of the uranium cation complex [(COT)U(HMPA)3][BPh4] with KCp (70% yield). The analogous tmp derivative (COT)LJ(tmp)(HMPA)2 was obtained upon reduction of the cationic uranium(iv) complex [(COT)U(tmp)(HMPA)2][BPh4] with sodium amalgam.153... 

Arsenin will form bis-sandwich complexes 22, 23, and 14 when it is condensed with vapors of the metals Cr, V, and Ti, respectively (Equation 6). When Cr is condensed with arsenin and a 25-fold excess of benzene, it forms 22, the mixed arsenin/benzene sandwich 24, and bis(benzene)chromium in the ratio of 6 3 1 (Equation 7) <19990M1495>. Clearly arsenin complex formation is favored over the benzene complexes even when the benzene is in large excess. Another example of the preference for it-complexation of an arsenin ring versus a benzocyclic ring is shown in Equation (8). The reaction of 18 with (Py)3Mo(CO)3 gives exclusively 15. No product with metal complexation to the benzocyclic ring was detected <20010M2109>. 

The mixed cyclopentadienyl-cycloheptatrienyl ( 5-7 ) titanium complex Cp( -C7H7)Ti has been prepared in 33 -40% yield by the reduction of CpTiCb with isopropylmag-nesium bromide or Mg in the presence of cycloheptatriene. Reduction of Cp TiCb in THF with Mg in the presence of cycloheptatriene gives Cp ( -C7H7)Ti in 68% yield. Titanium 5-7 complexes exhibit sandwich structures see Sandwich Compound) with the five-membered and seven-membered rings nearly parallel to each other. 

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