19212-22-7Relevant academic research and scientific papers
Conformational studies of EPh3M(CO)5 complexes (E = P, As or Sb; M = Cr, Mo or W)
Davies, M. S.,Allen, G. W.,Aroney, M. J.,Hambley, T. W.,Pierens, R. K.
, p. 81 - 92 (1994)
Studies are reported of the electro-optical Kerr effect, electric dipole moments and IR carbonyl stretching frequencies of the nine EPh3(CO)5 complexes (E = P, As or Sb and M = Cr, Mo or W).The experimental results are applied in conjuction with molecular
Crystal Structures of , and (M = Mo or W): A Comparative Study of Structure and Bonding in Complexes (E = P, As or Sb; M = Cr, Mo or W)
Aroney, Manuel J.,Buys, Irmi E.,Davies, Murray S.,Hambley, Trevor W.
, p. 2827 - 2834 (2007/10/02)
Crystal structures have been determined for , and (M = Mo or W) as part of a systematic study of a series of nine complexes (M = Cr, Mo or W; E = P, As or Sb).Trends in bond lengths and angles are rationalised in terms of streric and electronic interactions between the bonded M(CO)5 and EPh3 fragments.Comparison is made between the solid-state geometry of the free and co-ordinated EPh3.Torsion angles defining the disposition of the EPh3 groups in relation to M(CO)5 show little variation within the series.For all nine complexes the EPh3 groups have propeller geometry with small deviations from symmetric C3 structures.The studies were extended to include other related complexes.Trends in the strutural parameters of 29 such compounds are related to the steric behaviour and ?-acceptor capacity of the ligands L.It is shown that M-P bond dimensions are not adequately explained by hybridisation changes of the phosphorus atom in the ligand L.
Mechanism of the Low-Energy Photochemical Disproportionation Reactions of (η5-C5H5)2Mo2(CO)6
Stiegman, Albert E.,Stieglitz, Marc,Tyler, David R.
, p. 6032 - 6037 (2007/10/02)
The photochemical disproportionation reactions of the (RCp)2Mo2(CO)6 (R = H or CH3; Cp = η5-C5H4) complexes were investigated.The general disproportionation reaction can be written (RCp)2Mo2(CO)6 + 2L (RCp)Mo(CO)3- + (RCp)Mo(CO)2L2+ + CO.Control experiments showed that the previously reported analogous thermal disproportionation reactions are actually photochemical reactions.The properties of the ligand L are important in determining whether or nor the (RCp)2Mo2(CO)6 complex will disproportionate; the ligands cannot be sterically bulky and they must be good electron-donating ligands if disproportionation is to occur.If either of these criteria is not met, the irradiation of the (RCp)2Mo2CO)6 complex in the presence of the ligand leads only to substitution products of the type (RCp)2Mo2(CO)5L and/or (RCp)2Mo2(CO)4L2.The disproportionation reaction is wavelength dependent.For example, PPh3 will disproportionate the (RCp)2Mo2(CO)6 complex upon 290-nm irradiation but not upon 405-nm irradiation.Smaller ligands will disproportionate the dimer with 405-nm irradiation.The mechanism of lower energy pathway was investigated in detail, and it is proposed to be a radical chain pathway: (1) (RCp)2Mo2(CO)6->2(RCp)Mo(CO)3, (2) (RCp)Mo(CO)3+L->(RCp)Mo(CO)2L+CO, (3) (RCp)Mo(CO)2L+L->(RCp)Mo(CO)2L2, (4) (RCp)Mo(CO)2L2+(RCp)2Mo2(CO)6->(RCp)Mo(CO)2L2++(RCp)2Mo2(CO)6-, (5) (RCp)2Mo2(CO)6-->(RCp)2Mo2(CO)3-+(RCp)Mo(CO)3.The quantum yield data support this chain pathway; the quantum yields are greater than 1 and they are not reproducible from trial to trial.The key intermediate (CH3Cp)2Mo2(CO)6- was generated by reacting (CH3Cp)2Mo2(CO)6 with Na; in the presence of appropriate L the disproportionation resulted.The key to the mechanism is the formation of the 19-electron intermediate (RCp)Mo(CO)2L2.Electron transfer from this electron rich species is the driving force for the reaction.Evidence is presented for the formation of this intermediate.
