116224-27-2Relevant academic research and scientific papers
Reactions of Co-ordinated Ligands. Part 42. The Synthesis and Reactions of Cationic η4-Tetraphenylcyclobutadieneruthenium Complexes: X-Ray Crystal Structures of 4-C5H5)> and 5-CH(Ph)C(Ph)C(Ph)C(Ph)O>(η-C5H5)>
Crocker, Mark,Froom, Simon F.T.,Green, Michael,Nagle, Katharine R.,Orpen, A. Guy,Thomas, Dianne M.
, p. 2803 - 2814 (1987)
Addition of Ag to a solution of and PhC2Ph in CH2Cl2 results in the formation of the η4-cyclobutadiene complex 4-C4Ph4)(η-C5H5)> (1).U.v. irradiation of a solution of (1) in MeCN gives 4-C4Ph4)(η0C5H5)> (2), structurally identified by X-ray crystallography.The η4-tetraphenylcyclobutadiene ligand is not co-ordinated symmetrically to the ruthenium as is indicated by Ru-C distances of 2.192(2), 2.208(3), 2.177(2), and 2.175(2) A, a distortion which is related to the frontier orbitals presented by the d6Ru(η-C5H5)-L(1+) fragment (L+MeCN).The mechanism of formation of (1) is discussed.Tetramethylammonium bromide and chloride also react with (1) on u.v. irradiation in CH2Cl2 to form 4-C4Ph4)(η-C5H5)> .These complexes are also formed when (2) is reacted thermally with the corresponding halide anions.A related reaction occurs between (2) and the thiolate anion of Na forming 4-C4Ph4)(η-C5H5)>, however, the presence of water in this latter reaction leads to an unusual ring-opening reaction and the formation of 5-CH(Ph)C(Ph)C(Ph)C(Ph)O>(η-C5H5) (7) whose structure was elucidated by X-ray crystallography.A η5(5e)-bonded butadienolato ligand has been generated by nucleophilic attack of hydroxide ion on the η4-C4Ph4 ligand leading to ring-opening of an η3-cyclobutenyl complex.Protonation of (7) affords 6-C6H5(CH2CPh=CPhCOPh)>(η-C5H5)> (8).Mixed C5-C6 sandwich cations are also formed on u.v. irradiation of (1) in the presence of alkynes RC2R, and this way 6-C6Ph6)(η-C5H5)> (9), 6-C6Ph5Me)(η-C5H5)> (10), 6-C6Ph4Me2)(η-C5H5)> (11), and 6-C6Ph4(CO2Me)2>(η-C5H5)> (12) are obtained in good to moderate yield.Complex (9) is also formed on reaction of (5) with PhC2Ph and Ag, providing insight into this novel ring-expansion reaction.The related cationic complex 6-C6Ph6)(η-C5H5) (13) is formed in low yield on reaction of EtC2Et with and Ag.The low-temperature 100.6-MHz 13C- n.m.r. spectrum of (13) is discussed in terms of rotational movement of the ethyl groups.Treatment of (9) and (11) with K leads to a selective attack on the η-cyclopentadienyl ring and the formation of 4-C5H6)(η-C6Ph6)> (14) and 4-C5H6)(η6-C6Ph4Me2)> (15).This reduction of (9) with Na-Hg in thf gives (14) and 5-exo-C6Ph6H)(η-C5H5)>.
