Carbonyls, Phosphines, and Substitution

Owing to their particular electronic properties, NHCs are well known to substitute for various ligands bound to TM complexes. Since they are generally easy to synthesize, to handle and commercially available, carbonyl, phosphines, and... 

Hydroxyall l Hydroperoxyall l Peroxides. There is evidence that hydroxyalkyl hydroperoxyalkyl peroxides (2, X = OH, Y = OOH) exist in equihbrium with their corresponding carbonyl compounds and other a-oxygen-substituted peroxides. For example, reaction with acyl haUdes yields diperoxyesters. Dilute acid hydrolysis yields the corresponding ketone (44). Reduction with phosphines yields di(hydroxyalkyl) peroxides and dehydration results in formation of cycHc diperoxides (4). 

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 DECOMPOSITION OF COBALT OCTACARBONYL AND SUBSTITUTED BINUCLEAR COBALT CARBONYL DERIVATIVES IN THE PRESENCE OF TRIPHENYL PHOSPHINE... 

Rhenium(0) compounds are rare and frequently lie in the realm of the organometallic chemistry. A simple example is decacarbonyldirhenium(0) in which two staggered, square-pyramidal Re(CO)5 fragments are held together by a single rhenium-rhenium bond. Substitution of carbonyl ligands is possible by tertiary phosphines and arsines, silanes and isocyanides, and binuclear Re-Re, Mn-Re, and Co-Re complexes have been studied. " Successive replacement of CO ligands can readily be observed by vibrational spectroscopy. This has been demonstrated... 

Contrary to early reports,16 pentacarbonylhydridorhenium is air stable.6 The neat liquid, however, is moderately sensitive to light, turning yellow with formation of Re3H(CO)14.9 Pentacarbonylhydridorhenium is stable up to 100 °C, whereupon it decomposes to form Re2(CO)10 and H2.1 Substitution of carbonyl groups in ReH(CO)5 by tertiary phosphines and other Lewis bases is well known and apparently occurs by a radical chain pathway.6 More detailed surveys of the reactivity of ReH(CO)5 have been summarized elsewhere.10,11... 

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... 

Further crystallographic evidence for metal-carbonyl ir bonding is found in phosphine and phosphite derivatives of hexacarfconylchromium- Substitution of R3P for CO in Cr(CO)ft creates a complex of C4 symmetry in which one CO group lies trans to the phosphorus ligand (Fig. 11.29). The two trans ligands will compete for the same ir orbital, but carbon monoxide is a better v acid (ir acceptor) than the phosphine (Fig. 11.30). As a result, the Cr—CO r bond should be shorter relative to Cr—CO and to Cr—CO in CrtCO). The data in Table 11.12 show that these predictions are borne out. in keeping with the substantial ir character in the metal-carbonyl bond. 

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