An investigation of ethylene rotational barriers for 5-coordinate d(8) metal bis-ethylene complexes

作者：Adams Jeramie J; Arulsamy Navamoney; Roddick Dean M^*

来源：Polyhedron, 2014, 84: 209-215.

DOI：10.1016/j.poly.2014.08.058

• Iridium organometallics
• Pincer complex
• Ethylene complex
• Phosphine coordination
• DFT analysis

The successful isolation and structural characterization of ((PCP)-P-CF3)Ir(C2H4)(2) is reported, which confirms a rare example of axial and equatorial ethylene coordination in a TBP coordination environment. OFT studies indicate a moderate barrier to ethylene rotation for the equatorial C2H4 group (Delta G(double dagger) = 19.0 kcal mol(-1)), and a negligible rotational barrier for the axial C2H4 (Delta G(double dagger) = 1.2 kcal mol(-1)). DFT analyses of ethylene rotational barriers for a series of known symmetrical (equatorial/equatorial) and asymmetric (equatorial/axial) bis ethylene Ir(l) complexes are consistent with previously reported experimental rotational barriers. In the case of the asymmetric systems ([9]aneS(3))Ir(C2H4)(2)(+) and (Tp)Ir(C2H4)(2), a separate equatorial C2H4 rotational barrier is not observed due to facile conformational exchange of axial and equatorial ethylene coordination sites. Conformational exchange is not observed for ((PCP)-P-CF3)Ir(C2H4)(2).

• 出版日期2014-12-14