Alkyl/aryl complexes

Closely related are the -acyl complexes of iron (115). These have been prepared by three methods. Loss of N2 from (112) in the presence of an alkyl halide gives oxidative addition see Oxidative Addition) to yield ) -acyl complexes for some phosphine ligands. Sodium amalgam reduction of Fe halide complexes (116), and exposme of the resulting (117) to an alkyl halide, gives similar complexes (equation 24). Finally, placement of iron alkyl (aryl) complexes (118) under a CO atmosphere results in insertion to afford complexes (119) (equation 25). ... 

Cp 2Zr(H)(CH3CN)+ which is rapidly and irreversibly trapped by insertion. This is confirmed by the reaction ofCp 2Zr(H)(THF) with CH3CN, which proceeds by rapid ligand substitution and insertion (64). For the ethyl complex Cp 2Zr(CH2CH3)(CH3CN), the insertion pathway dominates the fi- elimination pathway (product ratio 85/15). As above, alkyl or aryl substituents on the) carbon accelerate the ji-H elimination, and for Cp jZrfCH 2CH 2 R)(CH jCN (R = alkyl, aryl) complexes only (i-H elim-... 

Some of the most widely used methods for preparing alkyl(aryl) complexes are listed below. 

The osmium(VI) complexes 0s02X2(PR3)2 are not generally obtainable with the smaller alkyl and alkyl(aryl)phosphines, which tend to be good... 

Alkene complexes Ammine complexes Aqueous chemistry Arsine complexes Binary compounds Bipyridyl complexes Bond lengths acetylacetonate alkene complexes alkyl and aryl complexes ammine complexes aqua ion... 

Colona and coworkers oxidized a variety of alkyl aryl and heterocyclic sulfides to the sulfoxides using t-butyl hydroperoxide and a catalytic amount of a complex (97) derived from a transition metal and the imines of L-amino acids. Of the metals (M = TiO, Mo02, VO, Cu, Co, Fe), titanium gave the highest e.e. (21%), but molybdenum was the most efficient catalyst. The sulfoxides were accompanied by considerable sulfone125. 

Fischer-type carbene complexes, generally characterized by the formula (CO)5M=C(X)R (M=Cr, Mo, W X=7r-donor substitutent, R=alkyl, aryl or unsaturated alkenyl and alkynyl), have been known now for about 40 years. They have been widely used in synthetic reactions [37,51-58] and show a very good reactivity especially in cycloaddition reactions [59-64]. As described above, Fischer-type carbene complexes are characterized by a formal metal-carbon double bond to a low-valent transition metal which is usually stabilized by 7r-acceptor substituents such as CO, PPh3 or Cp. The electronic structure of the metal-carbene bond is of great interest because it determines the reactivity of the complex [65-68]. Several theoretical studies have addressed this problem by means of semiempirical [69-73], Hartree-Fock (HF) [74-79] and post-HF [80-83] calculations and lately also by density functional theory (DFT) calculations [67, 84-94]. Often these studies also compared Fischer-type and... 

Fig 1 Heteroatom-stabilised (X=OR, NR2) and non-heteroatom-stabilised (X=alkyl, aryl) alkyl- (1), alkenyl- (2), aryl- (3) and alkynylcarbene (4) complexes of group 6 metals... 

The ability of Fischer carbene complexes to transfer their carbene ligand to an electron-deficient olefin was discovered by Fischer and Dotz in 1970 [5]. Further studies have demonstrated the generality of this thermal process, which occurs between (alkyl)-, (aryl)-, and (alkenyl)(alkoxy)carbene complexes and different electron-withdrawing substituted alkenes [6] (Scheme 1). For certain substrates, a common side reaction in these processes is the insertion of the carbene ligand into an olefinic C-H bond [6, 7]. In addition, it has been ob-... 

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