Conformations and Dynamic Behaviour of Rhodium Complexes with 1,4-Bis(diphenylphosphanyl)butane, DIOP and Its HO Analogue
✍ Scribed by Renat Kadyrov; Armin Börner; Rüdiger Selke
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 312 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
The temperature dependence of NMR spectra of TC 7 } and close to B 3 . The symmetrical doublet in the 31 P-NMR spectra is assigned to the fast equilibrium {TC 7 -C 4 } v [(L)Rh(cod)]BF 4 complexes with L = dppb (1), (R,R)-diop ( ) and (R,R)-HO-diop (3) has been examined. Molecular TC 1 v {C 5 -TC 2 }. The resonances of the other species are consistent with B 3 = B 6 geometry. A fused dioxolane ring mechanics and ab initio calculations on the [{1,4bis(dimethylphosphanyl)butane}Rh + (diolefin)] complex forces the chelate in diop complexes to adopt the B 4 = B 5 conformation. For both types of ligand the chair-like predict local energy minima for all twist-chair (TC 1 , TC 2 = TC 7 , TC 3 = TC 6 , TC 4 = TC 5 ) and two boat (B 3 = B 6 and TB 1 ) conformation is enthalpically preferred at low temperatures (∆H°= 0.45-0.46 kcal mol -1 ), whereas the boat-shaped conformations. Furthermore, ab initio calculations at the B3LYP/6-31G(d)/LANL2DZ level show that two minima are structure predominates at temperatures above 200 K (∆S°= 0.9-1.3 cal K -1 mol -1 ). Line-shape analysis provides a boat located in the wide-open region between the TC 7 and C 4 conformations. Relative B3LYP/6-31G(d) energies of the B 3 , pseudorotation barrier for complex 1 of ∆G ϶ = 5.9 kcal mol -1 and for 2 ∆G ϶ = 5.3 kcal mol -1 at 184 K. The free energy of TC 1 and {C 4 -TC 7 } conformations are 0.0, 0.71 and 0.97-1.08 kcal mol -1 , respectively. Analysis of crystallographic data activation at this temperature for the boat-chair interconversion is ∆G ϶ = 8.6 kcal mol -1 for complex 1 and contained in the Cambridge Structural Database shows that the majority of structures are concentrated in the region {C 4 -∆G ϶ = 8.0 kcal mol -1 for complex 2. graphic data show that these chelates may adopt some non- [a]