Platinum(II) phosphine complexes of dicarboxylates and ammonia: crystal structures of [{Pt(PPh3)2}2{µ -1,3-(O2C)2C6H4} 2], [{Pt(PPh3)2(NH3)}2 {µ-1,4-(O2C)2C6H4 }][PF6]2 and cis-[Pt(PPh3)2(NH3) 2][NO3]2
Abstract
The reaction of [Pt(PPh
3
)
2
(CO
3
)]
with a rigid dicarboxylic acid H
2
L gave rise to dimeric
compounds
[{Pt(PPh
3
)
2
}
2
(µ-L)
2
] 1
[H
2
L = C
6
H
4
(CO
2
H)
2
-1,4 (terephthalic acid) a,
C
6
H
4
(CO
2
H)
2
-1,3 (isophthalic
acid) b,
trans,trans-HO
2
CCH![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CHCH
CHCO
2
H (muconic acid) c or
4,4′-HO
2
CC
6
H
4
C
6
H
4
CO
2
H (biphenyldicarboxylic acid) d], which
have been characterised spectroscopically and, in the case of
1b, crystallographically. When the reaction was carried out in
the presence of NH
4
PF
6
the
NH
4
+
competed with the carboxylic acid and the
major product from the reaction was
[{Pt(PPh
3
)
2
(NH
3
)}
2
(µ-L)][PF
6
]
2
2, which has been
characterised crystallographically for L = terephthalate.
This suggests that NH
4
+
is acidic enough to react
with [Pt(PPh
3
)
2
(CO
3
)], which has been
confirmed by the synthesis of
cis-[PtL
2
(NH
3
)
2
]X
2
[L = PPh
3
, X = PF
6
3a or NO
3
3b;
L = PEt
3
, X = PF
6
4a or NO
3
4b;
L
2
= Ph
2
PCH
2
CH
2
PPh
2
(dppe), X = PF
6
5a] from [PtL
2
(CO
3
)]. The complex
cis-[Pt(PPh
3
)
2
(
15
NH
3
)
2
][NO
3
]
2
was synthesized from
15
NH
4
NO
3
and characterised by a
combination of
31
P-{
1
H},
15
N-{
1
H},
195
Pt and
1
H NMR spectroscopy. The crystal structure of
cis-[Pt(PPh
3
)
2
(NH
3
)
2
][NO
3
]
2
3b has been determined and
shows strong hydrogen bonding between the co-ordinated ammonia and the
nitrate counter ions. The compound PhC
2
CO
2
H also
reacted with [PtL
2
(CO
3
)], though the products were
not the expected bifunctional carboxylates
cis-[PtL
2
(O
2
CC
2
Ph)
2
] but the bis(phenylalkynyl) compounds
cis-[PtL
2
(C
2
Ph)
2
]
(L = PPh
3
6,
L
2
= dppe 7).
CHCH
CHCO
2
H (muconic acid) c or
4,4′-HO
2
CC
6
H
4
C
6
H
4
CO
2
H (biphenyldicarboxylic acid) d], which
have been characterised spectroscopically and, in the case of
1b, crystallographically. When the reaction was carried out in
the presence of NH
4
PF
6
the
NH
4
+
competed with the carboxylic acid and the
major product from the reaction was
[{Pt(PPh
3
)
2
(NH
3
)}
2
(µ-L)][PF
6
]
2
2, which has been
characterised crystallographically for L = terephthalate.
This suggests that NH
4
+
is acidic enough to react
with [Pt(PPh
3
)
2
(CO
3
)], which has been
confirmed by the synthesis of
cis-[PtL
2
(NH
3
)
2
]X
2
[L = PPh
3
, X = PF
6
3a or NO
3
3b;
L = PEt
3
, X = PF
6
4a or NO
3
4b;
L
2
= Ph
2
PCH
2
CH
2
PPh
2
(dppe), X = PF
6
5a] from [PtL
2
(CO
3
)]. The complex
cis-[Pt(PPh
3
)
2
(
15
NH
3
)
2
][NO
3
]
2
was synthesized from
15
NH
4
NO
3
and characterised by a
combination of
31
P-{
1
H},
15
N-{
1
H},
195
Pt and
1
H NMR spectroscopy. The crystal structure of
cis-[Pt(PPh
3
)
2
(NH
3
)
2
][NO
3
]
2
3b has been determined and
shows strong hydrogen bonding between the co-ordinated ammonia and the
nitrate counter ions. The compound PhC
2
CO
2
H also
reacted with [PtL
2
(CO
3
)], though the products were
not the expected bifunctional carboxylates
cis-[PtL
2
(O
2
CC
2
Ph)
2
] but the bis(phenylalkynyl) compounds
cis-[PtL
2
(C
2
Ph)
2
]
(L = PPh
3
6,
L
2
= dppe 7).
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