The migration of a phenyl group from phosphorus to the coordinated
ruthenium center in
complexes
(η6-arene)[η2-Ph2PC(R)C(R‘)O]RuCl,
2 [arene =
1,3,5-Me3C6H3 or
C6Me6; R =
H or Me; R‘ = But], occurs in methanol at reflux.
The reaction is favored by the addition of
KOAc and affords selectively the stable phosphinito enolato derivatives
(η6-arene)[η2-Ph(MeO)PC(R)C(R‘)O]RuPh.
In contrast, the reaction of complexes 2 with methanol
and
K2CO3 preserves the functional ligand and
affords selectively the hydride derivatives
(η6-arene)[η2-Ph2PC(R)C(R‘)O]RuH.
The cleavage of the ruthenium−chlorine bond in complexes 2 is also the preliminary step involved in the
coupling process of functional phosphino
enolato ligands with 1-alkynes HC⋮CR‘‘. The reaction results in
the formation of complexes
{(η6-arene)Ru[η3-CHC(R‘‘)C(R)(PPh2)C(R‘)O]}(PF6)
[R = H or Me, R‘ = But or Ph, R‘‘ =
H, Me, Ph, p-MeC6H4, or
SiMe3], the isomerization of which into complexes
{(η6-arene)Ru[η3-CH(PPh2)C(R‘‘)C(R)C(R‘)O]}(PF6),
[R‘ = But, R‘‘ = H, Me, Ph, or
p-MeC6H4] occurs
only when R = H. The isomerization consists of an intramolecular
[1,3]-migration of a
phosphorus−carbon bond and is catalyzed by the fluoride anion.
When R‘‘ = H, a subsequent
cleavage of the ruthenium−carbon bond foreshadows the formation of
(η6-C6Me6)[η1-Ph2PCH2CHCHC(O)But]RuCl2,
11. Thus, starting from the precursor
(η6-C6Me6)[η1-Ph2PCH2C(O)But]RuCl2,
the process achieves formally an insertion of ethyne into the
starting
functionalized phosphorus−carbon bond. The scarcely isolable
complexes {(η6-arene)Ru[η3-C(CH2)C(R)(PPh2)C(R‘)O]Ru}(PF6)
[R = H or Me, R‘ = But or Ph] reveal an
easy
cleavage of the functionalized phosphorus−carbon bond. This
cleavage is the preliminary
step involved in the formation of metallafuran complexes
{(η6-arene)(Ph2PX)Ru[η2-C(CH3)CRC(R‘)O]}(PF6) [X =
Cl or F, R = H or Me, R‘ = But or Ph], which implies
also
the capture of a halide anion by phosphorus in a transient
intermediate.
