Carbonyl substituted metal complexes

Two commonly used synthetic methodologies for the synthesis of transition metal complexes with substituted cyclopentadienyl ligands are important. One is based on the functionalization at the ring periphery of Cp or Cp metal complexes and the other consists of the classical reaction of a suitable substituted cyclopentadienyl anion equivalent and a transition metal halide or carbonyl complex. However, a third strategy of creating a specifically substituted cyclopentadienyl ligand from smaller carbon units such as alkylidynes and alkynes within the coordination sphere is emerging and will probably find wider application [22]. 

Kinetic studies on substitution reactions of carbonyl metal complexes. H. Werner, Angew. Chem., Int. Ed. Engl., 1968, 7,930-941 (106). 

The reactions of nucleophilic reagents with cationic and uncharged metal carbonyl complexes have received much attention in the past, and it is not surprising that these studies have now been extended to isocyanide metal complexes. Different products in these reactions can arise by three general routes these include ligand substitution, reactions involving attack at a ligand, and reduction of the metal complex. All have been observed in reactions with metal isocyanide complexes. 

Several papers have appeared recently comparing various properties of carbonyl metal complexes substituted by various phosphines or phosphite ligands or isocyanides. Angelici and Ingemanson (4) studied the equilibrium... 

The earliest NLO studies involving metal pyridyl complexes were reported by Frazier et al. in 1986 who investigated the SHG properties of various group 6 metal pyridyl carbonyls.63 Although most of the complexes tested show little or no activity, (6) and (7) have respective SHG efficiencies of 0.2 and 1.0 times ADP using a 1,064 nm laser.63 Shortly after, Calabrese and Tam reported SHG from the Re1 complex (8).64 Subsequent studies by Eaton and Tam et al.65,66 describe the preparation of inclusion compounds of various metal complexes with thiourea or tris-ort/ o-thymotide. Unfortunately, none of the complexes [W(CO)5L] (L = pyridine, py, or a 4-substituted py) produce SHG-active materials.65,66... 

The product distribution observed in the dimerization of polyene-substituted ketyl radicals is also remarkable in that only products involving dimerization at the carbonyl carbon atom are observed (equation 23)82,83. This finding is quite independent of the reducing agent, since ketyl radicals formed by reduction with low-valent transition metal complexes behave analogously84-86. 

Transition metal complexes which react with diazoalkanes to yield carbene complexes can be catalysts for diazodecomposition (see Section 4.1). In addition to the requirements mentioned above (free coordination site, electrophi-licity), transition metal complexes can catalyze the decomposition of diazoalkanes if the corresponding carbene complexes are capable of transferring the carbene fragment to a substrate with simultaneous regeneration of the original complex. Metal carbonyls of chromium, iron, cobalt, nickel, molybdenum, and tungsten all catalyze the decomposition of diazomethane [493]. Other related catalysts are (CO)5W=C(OMe)Ph [509], [Cp(CO)2Fe(THF)][BF4] [510,511], and (CO)5Cr(COD) [52,512]. These compounds are sufficiently electrophilic to catalyze the decomposition of weakly nucleophilic, acceptor-substituted diazoalkanes. 

There are few examples of metal complexes reacting with 1,2,3-thiadiazoles to form stable products one case involves the formation of the 2-substituted derivative (23) with tungsten penta-carbonyl (Equation (9)) <83CB230>. Reaction of simple 1,2,3-thiadiazoles with peracid occurs preferentially at N3 to give an A-oxide <84CHEC-I(6)447>. 

TRI- AND TETRANUCLEAR CARBONYL-RUTHENIUM CLUSTER COMPLEXES CONTAINING ISOCYANIDE, TERTIARY PHOSPHINE, AND PHOSPHITE LIGANDS. RADICAL ION-INITIATED SUBSTITUTION OF METAL CLUSTER CARBONYL COMPLEXES UNDER MILD CONDITIONS... 

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