159026-75-2Relevant academic research and scientific papers
η5 η3 Hapticity Interconversion in Cycloheptadienyl Molybdenum Complexes
Beddoes, Roy L.,Hinchliffe, Jonathan R.,Souza, Ana-Lucia A. B. de,Whiteley, Mark W.
, p. 2303 - 2312 (1994)
A series of reactions of the general type 2(η5-C7H9)>(1+) + L' -> 2(η3-C7H9)>(1+), involving η5 -> η3 hapticity conversion at a molybdenum co-ordinated cycloheptadienyl ring, have been examined.The specific examples investigated comprise reactions of 5-C7H9)>(1+) 2 = 2,2'-bipyridyl (bipy) 1, Ph2PCH2PPh2 (dppm) 6, Ph2PCH2CH2PPh2 (dppe) 7; L = CNtBu 17 or PPh3 18> with NCMe or CNtBu.Complex 1 reacts reversibly with NCMe to give 3-C7H9)>(1+) 2 and, in NCMe, 7 exists as an equilibrium mixture with 3-C7H9)>(1+) 8.The complexes 6, 17 and 18 do not react with NCMe at ambient temperature.Treatment of 1, 6 and 7 with CNtBu affords 2(η3-C7H9)>(1+) (L2 = bipy 4, dppm 9 or dppe 11) although 4 is better prepared by reaction of 3-C7H9)>(1+) 5 with bipy.Complex 4 is resistant to carbonyl elimination but 9 and 11 undergo facile loss of CO to give 2(η5-C7H9)>(1+) (L2 = dppm 10 or dppe 12 so establishing examples of associative ligand-substitution processes which proceed with η5 -> η3 -> η5 hapticity interconversion at the C7H9 dienyl ligand.The reaction between 17 and CNtBu affords 5-C7H9)>(1+) 19 with no observable η3-C7H9 intermediate but 19 reacts with further CNtBu to yield 3-C7H9)>(1+) 20.The crystal structures of complexes 1 and 4 have been determined.Complex 1 adopts an asymmetric ligand arrangement similar to that previously described for 6.Complex 4 has a pseudo-octahedral molecular geometry in which CNtBu is located trans to the η3-bonded C7H9 ligand.
