Novel chemistry of rhodium induced by a new type of ligand, a
phosphino-N-benzoylhydrazone: crystal structure of
[![[upper bond 1 start]](https://www.rsc.org/images/entities/char_e010.gif)
Rh
(CO){C(CO2Me)![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CHCO2
Me}{P![[upper bond 1 end]](https://www.rsc.org/images/entities/char_e011.gif)
PPh2CH[C(CO
2Me)C(CO2
Me)]C -(But)N –N
C(Ph)O }]
Abstract
Treatment of the phosphino-N,N-dimethylhydrazone
Z-PPh
2
CH
2
C(Bu
t
)NNMe
2
with benzohydrazide in the presence of acetic acid gave the
phosphino-N-benzoylhydrazone
PPh
2
CH
2
C(Bu
t
)NNHC(O)Ph
I. Treatment of the phosphine I with 0.5 equivalent of
[{RhCl(CO)
2
}
2
] gave the
rhodium(I) complex
[Rh(CO){P![[upper bond 2 start]](https://www.rsc.org/images/entities/char_e014.gif)
Ph
2
CH
2
C(Bu
t
)N![[upper bond 2 end]](https://www.rsc.org/images/entities/char_e015.gif)
–NC(Ph)O}] 1
containing two fused five-membered chelate rings. Complex 1 readily
reacted with Br
2
to give the dibromorhodium(III)
complex
[RhBr
2
(CO){PPh
2
CH
2
C(Bu
t
)N–NC(Ph)
O }] 2. Similarly, it underwent
oxidative-addition reactions with MeI or HC![[triple bond, length as m-dash]](https://www.rsc.org/images/entities/char_e002.gif)
CCH
2
Cl to
give rhodium(III) complexes of type
[RhX(R)(CO){ PPh
2
CH
2
C(Bu
t
) N–NC(Ph)
O }] (R = Me, X = I 3;
R = CHCCH
2
,
X = Cl 4). In contrast, treatment of 1 with allyl bromide
caused loss of the carbon monoxide ligand to give the
η
3
-allylrhodium(III) complex
[RhBr(η-3-C
3
H
5
){
PPh
2
CH
2
C(Bu
t
)
N–NC(Ph)O }] 5.
Treatment of 1 with MeO
2
CCCCO
2
Me gave the
cyclometallated alkenylrhodium(III) complex
[Rh(CO){C(CO
2
Me)CHCO
2
Me
}{ PPh
2
CH[C(CO
2
Me) C(CO
2
Me)]C(Bu
t
)
N–NC(Ph)O
}] 6, in which the phosphine ligand is tetradentate through
P, N, O and C; in the formation of 6
one alkyne has attacked the methylene carbon of the phosphine ligand and
the second has added to Rh–H to give
RhC(CO
2
Me)CH(CO
2
Me). On the prolonged
heating 6 isomerised to give the rhodium(III) complex 7; in
this isomer the C(CO
2
Me)CH(CO
2
Me) ligand
is trans to phosphorus whereas in 6 it is cis. The
crystal structure of 6 has been determined.
NNMe
2
with benzohydrazide in the presence of acetic acid gave the
phosphino-N-benzoylhydrazone
PPh
2
CH
2
C(Bu
t
)NNHC(O)Ph
I. Treatment of the phosphine I with 0.5 equivalent of
[{RhCl(CO)
2
}
2
] gave the
rhodium(I) complex
[Rh(CO){PPh
2
CH
2
C(Bu
t
)N–NC(Ph)O}] 1
containing two fused five-membered chelate rings. Complex 1 readily
reacted with Br
2
to give the dibromorhodium(III)
complex
[RhBr
2
(CO){PPh
2
CH
2
C(Bu
t
)N–NC(Ph)
O }] 2. Similarly, it underwent
oxidative-addition reactions with MeI or HCCCH
2
Cl to
give rhodium(III) complexes of type
[RhX(R)(CO){ PPh
2
CH
2
C(Bu
t
) N–NC(Ph)
O }] (R = Me, X = I 3;
R = CHCCH
2
,
X = Cl 4). In contrast, treatment of 1 with allyl bromide
caused loss of the carbon monoxide ligand to give the
η
3
-allylrhodium(III) complex
[RhBr(η-3-C
3
H
5
){
PPh
2
CH
2
C(Bu
t
)
N–NC(Ph)O }] 5.
Treatment of 1 with MeO
2
CCCCO
2
Me gave the
cyclometallated alkenylrhodium(III) complex
[Rh(CO){C(CO
2
Me)CHCO
2
Me
}{ PPh
2
CH[C(CO
2
Me) C(CO
2
Me)]C(Bu
t
)
N–NC(Ph)O
}] 6, in which the phosphine ligand is tetradentate through
P, N, O and C; in the formation of 6
one alkyne has attacked the methylene carbon of the phosphine ligand and
the second has added to Rh–H to give
RhC(CO
2
Me)CH(CO
2
Me). On the prolonged
heating 6 isomerised to give the rhodium(III) complex 7; in
this isomer the C(CO
2
Me)CH(CO
2
Me) ligand
is trans to phosphorus whereas in 6 it is cis. The
crystal structure of 6 has been determined.
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![[upper bond 1 start]](https://www.rsc.org/images/entities/h2_char_e010.gif)
Rh
(CO){C(CO2Me)![[double bond, length as m-dash]](https://www.rsc.org/images/entities/h2_char_e001.gif)
CHCO2
Me}{P![[upper bond 1 end]](https://www.rsc.org/images/entities/h2_char_e011.gif)