95348-70-2Relevant articles and documents
Electrophilic attack at metal carbonyls. Kinetics of reactions of halogens with some substituted dimetal carbonyls
Kramer, Gary,Patterson, John,Po?, Anthony,Ng, Lily
, p. 1161 - 1169 (2008/10/08)
The kinetics have been studied of reactions (in cyclohexane or decalin) of iodine with a number of dimetal carbonyls M3(CO)10-xLx (for x = 1, M = Re, L = PPh3; for x = 2, M2 = Mn2, MnRe, and Re2, L = PPh3; for x = 2, M = Mn L = P(OPh)3, P(OMe)3, PPh3, P(p-MeOC6H4)3, PPh2Et, PPhEt2, PEt3, P(n-Bu)3, and P(C6H11)3). The reactions are first order in the concentration of the reacting complex. The predominant term in most of the rate equations is k3[I2]2 but a term as high as k5[I2]4 is observed in one case, and for Mn2(CO)8{P(OPh)3}2 the rate equation is kobsd = {k3[I2]2 + k4[I2]3}/{1 + β1[I2] + β2[I2]2 + β3[I2]3}. Some reactions were also followed in CCl4, CH2Cl2, MeOH, EtOAc, and n-Bu2O. The reactions are concluded to involve rapid preformation of a series of adducts, complex·nI2, where n can be as high as 4. This is followed by electron transfer and fission of the metal-metal bond with formation of mononuclear iodo complexes. The effects of the nature of L on the rate constants for reactions with I2 or Br2 can best be interpreted in terms of initial electrophilic attack at the O atoms of the CO ligands, the surface of the complex providing an extended area of suitably high electron density which can bind several halogen molecules. The electronic effect appears to operate mainly through the σ-donor ability of the substituents and not their π-acid character. Some comparisons are drawn with reactions of halogens with other metal-carbonyl complexes and with some aryl-Sn compounds.
