η5↔η3Hapticity interconversion in cycloheptadienyl molybdenum complexes
- 1 January 1994
- journal article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 15,p. 2303-2312
- https://doi.org/10.1039/dt9940002303
Abstract
A series of reactions of the general type [Mo(CO)2L2(η5-C7H9)]++ L′→[Mo(CO)2(L′)L2(η3-C7H9)]+, involving η5→η3 hapticity conversion at a molybdenum co-ordinated Cycloheptadienyl ring, have been examined. The specific examples investigated comprise reactions of [Mo(CO)2L2(η5-C7H9)]+[L2= 2,2′-bipyridyl (bipy)1, Ph2PCH2PPh2(dppm)6, Ph2PCH2CH2PPh2(dppe)7; L = CNBut17 or PPh318] with NCMe or CNBut. Complex 1 reacts reversibly with NCMe to give [Mo(CO)2(NCMe)(bipy)(η3-C7H9)]+2 and, in NCMe, 7 exists as an equilibrium mixture with [Mo(CO)2(NCMe)(dppe)(η3-C7H9)]+8. The complexes 6, 17 and 18 do not react with NCMe at ambient temperature. Treatment of 1, 6 and 7 with CNBut affords [Mo(CO)2(CNBut)L2(η3-C7H9)]+(L2= bipy 4, dppm 9 or dppe 11) although 4 is better prepared by reaction of [Mo(CO)2(CNBut)(NCMe)2(η3-C7H9)]+5 with bipy. Complex 4 is resistant to carbonyl elimination but 9 and 11 undergo facile loss of CO to give [Mo(CO)(CNBut)L2(η5-C7H9)]+(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 CNBut affords [Mo(CO)(CNBut)3(η5-C7H9)]+19 with no observable η3-C7H9 intermediate but 19 reacts with further CNBut to yield [Mo(CO)(CNBut)4(η3-C7H9)]+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 CNBut is located trans to the η3-bonded C7H9 ligand.Keywords
This publication has 14 references indexed in Scilit:
- Synthesis, structure and reactivity of tri- and penta-hapto-bonded cycloheptadienyl complexes of molybdenumJ. Chem. Soc., Dalton Trans., 1993
- The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: ligand substitution via a ring slipped intermediate in cationic carbonylisonitrile derivativesPolyhedron, 1991
- The interconversion of η5 and η3 hapticities in cycloheptadienyl complexes of molybdenum and tungstenJournal of Organometallic Chemistry, 1991
- Synthesis, characterization, and reaction chemistry of complexes of the molybdenum-pentadienyl-nitrogen ligand system. Molecular structure and reactivity of 16-electron syn-.eta.3-pentadienyl complexesOrganometallics, 1990
- Preparation and properties of molybdenum-pentadienyl complexes: a facile .eta.5 .dblarw. .eta.3 reversible interconversion for a pentadienyl ligandOrganometallics, 1989
- The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: synthesis and substitution chemistry of some new carbonylacetonitrile derivativesJournal of Organometallic Chemistry, 1988
- Structural and reactivity patterns in transition-metal-pentadienyl chemistryChemical Reviews, 1988
- Ring-slippage chemistry of transition metal cyclopentadienyl and indenyl complexesChemical Reviews, 1987
- Diene and dienyl complexes of transition elements. 8. Addition and substitution reactions of pentadienyltricarbonylmanganese with phosphines, phosphites and carbon monoxideOrganometallics, 1984
- The crystal structure of some dicarbonyl allyl derivatives of substituted carbonyls of molybdenum : III. The crystal structure of dicarbonyl-2,2'-bipyridine-pyridine-π-allylmolybdenum tetrafluoroborate, [(CO)2(C10H8N2)(C5H5N)(π-C3H5)Mo]+[BF4]−Journal of Organometallic Chemistry, 1972