184486-18-8Relevant academic research and scientific papers
Dihydride complexes of the cobalt and iron group metals: An investigation of structure and dynamic behavior
Heinekey,Van Roon, Mirjam
, p. 12134 - 12140 (1996)
The previously reported cationic dihydride complexes (PP3)MH2+ (M = Co, Rh and Ir; PP3 = P(CH2-CH2PPh2)3) have been prepared using improved synthetic methods. Variable-temperature 1H and 31P NMR spectra of these complexes reveal complex dynamic behavior. The hydride region 1H NMR spectra have been accurately simulated at all temperatures using a simple site permutation model after taking into consideration the opposite signs of the cis and trans H-P coupling constants. Partial deuteration of the hydride ligands in the rhodium and cobalt complexes is achieved by exposure to D2. In the partially deuterated samples, no evidence is found for a bound dihydrogen ligand, but the involvement of a dihydrogen species in the dynamic process which interchanges the two hydride positions remains a mechanistic possibility, as indicated by a kinetic isotope effect k(H)/k(D) = 1.3(1). The partially deuterated samples exhibit large and temperature-dependent isotope effects on the 1H NMR chemical shifts observed for the hydride resonances, which are attributed to isotopic perturbation of resonance. This arises from non-statistical occupation of the two different hydride sites and also leads to perturbation of the averaged H-P coupling constants. Similar observations have been made for the neutral iron complex (PP3)FeH2.
