INTRAMOLECULAR C-C BOND FORMATION FROM b-KETO PHOSPHINE AND ALLENYLIDENE LIGANDS IN RELATED RUTHENIUM(II) CYCLOPENTADIENYL AND INDENYL COMPLEXES. X-RAY CRYSTAL STRUCTURE STUDY
J. Borge & S. García-Granda
Departamento de Química Física y Analítica. Facultad de Química. Universidad de Oviedo. C/ Julián Clavería, 8. 33006 Oviedo. Spain. Email: jjba@sauron.quimica.uniovi.es
The reaction of b-ketophosphines Ph2PCH(R')C(=O)R
[a: R = But, R' = H; b: R = Ph, R' = H; c:
R = But, R' = Me] with [RuCl(h5-CnHm)(PPh3)2]
complexes [1, CnHm =
cyclopentadienyl; 1', CnHm =
indenyl] affords neutral [RuCl(h5-CnHm)(PPh3){h1-(P)-ketophosphine}],
2a,b and 2'a. Cationic derivatives. [Ru(h5-CnHm)(PPh3){h2-(P,O)-ketophosphine}][PF6],
3a,b and 3'a-c, are obtained by the
reactions of complexes 1 and 1' with the
ketophosphines in the presence of NH4PF6.
Complex 3'c is diastereoselectively obtained as the SRuRC/RRuSC
enantiomeric pair as shown by an X-ray crystal structure
analysis. Owing to the hemilabile ability of the ketophosphine
ligand complexes 3a and 3'a easily react with
1,1-diphenyl-2-propyn-1-ol to yield the allenylidene complexes
[Ru(=C=C=CPh2)(h5-CnHm)(PPh3){h1-(P)-Ph2PCH2C(=O)
But}][PF6], 5a and 5'a, respectively.
Treatment of complexes 3a and 3'a with K2CO3
in methanol leads to the deprotonation of the coordinated
ketophosphine to give the neutral phosphino-enolate derivatives
[Ru(h5-CnHm)(PPh3){h2-(P,O)-Ph2PCH=C
(But)O}], 6a and 6'a, respectively . In
contrast allenylidene complexes 5a and 5'a react
with K2CO3 or KOH in methanol to afford the
alkynyl complexes [Ru{C=CC(OMe)Ph2}(h5-CnHm)(PPh3){h1-(P)-Ph2PCH2C(=O)But}]
7a and 7'a which are formed through the
nucleophilic addition of the methoxy group to the Cg atom of the
allenylidene chain. Similarly, the ethoxy-alkynyl derivative 8a
is obtained by the reaction of 5a with KOH in ethanol.
Under mild basic conditions (K2CO3/THF)
complexes 5a and 5'a are deprotonated to be
converted into the neutral derivatives [Ru{h2-(C,P)-C(=C=CPh2)CH[C(=O)But]PPh2}(h5-CnHm)(PPh3)],
9a and 9'a respectively through the generation of a
novel phosphametallacyclobutane ring and according to a
diastereoselective process. The molecular structure of 9'a
determined by an X-ray crystal structure analysis discloses a SRuRC/RRuSC
configuration and shows a nearly planar Ru-P(2)-C(2B)-C(1) ring
bearing an almost linear h1-(C)-coordinated allenyl group
[C(1)-C(2A)-C(3A)= 169.6(8)º]. The formation of the
four-membered ring probably takes place in a putative
intermediate arising from the deprotonation of the h1-(P)-ketophosphine
ligand in 5a and 5'a. The subsequent intramolecular
carbon-carbon bond formation between the allenylidene group and
the nucleophilic h1-(P)-phosphino-enolate ligands is
geometrically constrained to occur at the electrophilic Ca site of the
allenylidene ligand and the ruthenium fragment efficiently
directs the configuration of the new stereogenic carbon atom in
the resulting metallacycle ring.
Crochet, P., Demerseman, B., Vallejo, M. I., Gamasa, M. P., Gimeno, J., Borge, J. & García-Granda, S. (1997). Organometallics 16, 5406-5415.