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Novel Monobridged Dinuclear Platinum Species.

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Hydroxylation reactions of organic substrates which are
induced by ascorbic acid in aqueous media are well known.
Most likely, they involve free radicals and formation of hydrogen peroxide as an intermediatec61. In fact, ( I ) can be transformed into ( 4 ) , although in lower yield, by treatment with
H z 0 2 .The regioselective formation of ( 4 ) is interesting from
a mechanistic point of view. Probably, the closure of a fivemembered lactone ring from the acetic ester chain at C-7
is the rate-determining step of the reaction.
Received: April 27. 1977 [Z 725 IE]
German version: Angew. Chem. 89. 486 (1977)
CAS Registry numbers
( I ), 36522-80-2; ( 4 ) , 62905-92-4; ascorbic acid, 50-81-7
J . M . Pratt Inorganic Chemistry of Vitamin B I Z .Academic Press, London 1972, chapter 15; W Frirdrich: Vitamin B I Z und verwandte Corrinoide. Thieme, Stuttgart 1975, p. 87.
Synthesized from cyanocobalamin (E. Merck, Darmstadt) according lo
the procedure given by L. Werthemann, Ph. D. Thesis, ETH Zurich
1968.
From methanol/ether, ( 4 ) crystallizes orthorhombically (space group:
P 212121), with a = l9.054(2). b = 31.416(2), c=9.540( 1 ) A ; Z = 4 ,
= 1.33 g.cm--'. The structure was solved by Patterson and difference
syntheses and refined with the program SHELX-76 to the present values:
R =0.098 and R , =0.103 (Co anisotropic)for 4499 independent reflections
( F 2 3.00 (F), 2208 Friedel pairs). The absolute configuration assigned
to cobyrinic acid [4] [see ( I ) ] was thereby confirmed.
K . Vmkntesan, D. Dale, D. Crowfoot Hodgkin, C . E . Nockolds, F . H .
Moore, B. H . O'Connor, Proc. Roy. Soc. London A 323, 455 (1971).
For assignments of the "C-NMR signals of ( I ) see: A. I. Scott. C .
A. Toownsend, K . Okada, M . Kajiwara, R. J . Cushley, P. J . Whiiman,
J. Am.Chem. Soc. 96,8069(1974);A. R. Baitersby, M . Ihara, E . McDonald,
J . R. Re&ern, B. 7: Golding, J. Chem. SOC.Perkin Trans. I , 1977, 158.
J . H . Green, 8.J . Ralph, P. J . Schofield, Nature 198, 754 (1963).
'
'
Ibi
Fig. 1. a) Structure of ( 4 ) with numbering of the atoms; b) bond lengths
(A)in the chromophore of ( 4 ) . Standard deviations are: 0.01 A for Co-N,
and 0.02A for other bond lengths.
(e.g . 1.46 in cobyrinic acidr4]).On the other hand, the (N-21
(C-4) bond remains as an isolated double bond. Compound
( 4 ) crystallizes together with one molecule of methanol, which
is hydrogen-bonded to the CN ligand situated above the
plane of the molecule (O-H...N=2.67A) and with 0 - 5
(O...H-0=2.66A),
as well as with one molecule of water
which is linked by an C+H...N bridge of 2.82A to the
C N ligand situated below the plane of the molecule.
In the 'H-NMR spectrum, the transformation of ( I ) into
( 4 ) is demonstrated in particular by the shift of the (C-SFCH3
signal from 6=2.13 (or 2.08) to 6 = 1.85 and by the appearance
of a singlet for the OH group. The 13C-NMR spectra display
the following characteristic difference^[^]: (i) C-4 is deshielded
both by interruption of the conjugation at C-5 and the presence
of a O H group at this position. Thus, C-4 whose resonance
frequency in ( 1 ) lies in the range 6=171-176, gives rise
to an isolated peak at 6=191.8 in ( 4 ) ; (ii) a diminution
of the number of signals in the characteristic range for C-5
and C-15 (6= 100-105) from two to one; (iii) a displacement
of the C-6 signal from 6 = 164 to 6 = 112.2 ppm. The lactone
ring in ( 4 ) is readily recognizable in the 'H- and 13C-NMR
spectra by the absence of one methoxy signal, as well as
in the IR spectrum, by the presence of a characteristic absorption band at Fm,,=1785cm-'.
The transformation of (1) into ( 4 ) may be rationalized
as follows: Addition of a hydroxy free radical at C-5 and
concomitant reduction of the complex bonded cobalt ion
lead to .the formation of a cobalt(r1) complex (2) which is
readily re-oxidized to the corresponding cobalt(lr1) intermediate (3). Stabilization of the latter takes place by intramolecular attack of the acetic ester residue at C-7 with closure of
the lactone ring.
482
Novel Monobridged Dinuclear Platinum Species
By E. A . 1.: Ebsworth, Hugh M . Ferrier, Bernard J . L. Henner,
David W H . Rankin, Francis J . S. Reed, Heather E. Robertson,
and John D. Whitelock[*]
In most of the dinuclear platinum complexes known the
platinum atoms are linked by two bridging ligands. Two
ligands capable of forming singly linked complexes are
dimethyl sulfide and dimethyl telluride[''. Recently Manzer
and P arshalP'1 described the cyanide-linked dinuclear cation
in which the lone pairs of electrons on carbon and nitrogen
each act as nucleophiles. This is, however, an example of
a different type of bridging in which three, rather than two,
bonds separate the metal atoms. As far as we are aware
no examples of monobridged bis-platinurn(rv) species have
been reported as yet.
We report here the formation of several monobridged bisplatinum(1r) species and one monobridged bis-platinum(1v)
cation; we have characterized them by NMR spectroscopy,
and in one case, by IR spectroscopy and analysis (see Table
1).
[*] Prof. E. A. V. Ebsworth ['I, H. M. Ferrier, Dr. B. J. L. Henner, Dr.
D. W. H. Rankin, Dr. F. J. S. Reed, Dr. H. E. Robertson, J. D. Whitelock
Department of Chemistry, Edinburgh University
West Mains Road, Edinburgh EH9 355 (Scotland)
['I To whom correspondence should be addressed.
Angew. Chem. Int. Ed. Engl. 16 ( 1 9 7 7 ) No. 7
Table 1. Some NMR parameters of monobridged dinuclear platinum species
(I)=P
(4)=P
P
P
(5)=P
P
P
(6)=P
P
P
(3) = P
(7)=P
H
H
H
H
H
H
H
H
H
H
F
( 8 )= s
Se
I
2
2
2
2
2
2
2
2
2
2
1
2
H
H
H
PEt3
H-Pt-P'H2-Pt-H
11
/H
PEt,
PEt3
PEt,
PEt3
CI
Br
I
C1
Br
I
PEt,
PEts
PAt
PEt,
PEt,
PEt,
PEt,
PEt,
PEt,
PEt3
PEt,
PEt,
PEt,
,
c1
PEt3
PEt,
H
CI
Br
I
C1
Br
I
CI
Br
I
H
CI
H
H
PEt,
PEt,
PEt,
PEt,
PEt3
PEt,
PEt,
PEt,
PEt,
PEt,
PEt3
PEt,
PEt,
PEt3
PEt,
PEt,
- 169.7
-1520
- 147.8
- 148.7
- 117.1
-121.8
- 136.6
- 120.9
- 124.9
- 138.7
- 155.8
f211.0
1202
2804
2788
2631
3054, 18x7
3090, 1830
3048, 1745
2630, 1880
2680, 1XSO
2630, 1758
463
4519, 4453
6QH
'J(PtP) [Hz]
1
- 0.4
1
- 3.3
12.4
10.9
I
I
1
1
1
1
1
0
0
0
0
0
PEi,
I
/H
H-Pt-P'H2-Pt-H
";E
' t3
I t 3
H
H
1
1
PEt3
I
H
CI
Br
I
PEt,
PEt,
PEt3
CI
Br
I
H
C1
lAl
"'kEt3
(Bl
6PJ
- 188.4
1275
8 30
- 224.0
-
79 1
Treatment of two equivalents of tran~-[PtClH(PEt~)~]
with
one equivalent of trimethylsilylphosphane, Me3SiPHz,affords
the compound ( 1 )
rran~-[PtH(PEt~)~]2PH;Cl- f 1 )
and Me3SiC1.This follows the identification of the same cation
as one of the products of the reaction between trans[PtCIH(PEt3)2] and H3SiPH2I31.Compound ( 1 ) has been
isolated as yellow crystals which give a conducting solution
in dichloromethane. Its NMR parameters, as well as its IR
data and C,H elemental analyses, confirm its identity.
-+
r
P E t3
H---Pt
c1/
1
1
PE t3
c1'
I
/H
I
PEt?
PEt3
I
PEtB
PEt3
I
H-Pt-PH-Pt-H
I
PEt3
1
1
I
I
PEt3
I
The PHz bridged cation ( 1 ) undergoes reactions typical of
both a platinum(1i)hydride and a phosphonium ion. Thus with
HCI either the completely oxidized species (2) is obtained
or the partially oxidized complex, containing one four-coordinate and one six-coordinate Pt atom (see ( A ) in Table
l), depending on the proportion of HC1 used. Treatment with
potassium tert-butoxide, on the other hand, brings about proton abstraction from the bridging group to give the neutral
compound (3).
The reaction between SiMe3PH2 and PtC12(PEt3)z also
yields products containing PHz bridges. If [runs[PtC12(PEt3)2]is used, cation ( 4 ) is identified as the initial
I
C 1-Pt-PH2-Pt-C
C1
16)
PEt,
13)
Anqew Chem. Inr. Ed Engl. 16 (1977) N o . 7
141
PEt3
PEt3
/H
-PH2-Pt-H
product which then partly rearranges to give the &,trans
isomer ( 5 ) . When cis-[PtClz(PEt3),] is used as the starting
material again both isomers of the PH2 bridged cation are
observed. In addition, in each reaction mixture resonances
are found which are assigned to the neutral complex (6).
Analogous products are obtained using trans[PtBrZ(PEt3),] and trans-[Pt12(PEt3),] ; the symmetrical PHz
bridged diodide is the least stable with regard to isomerization.
PEt3
PEt3
I
I
Cl-Pt-PF2-Pt-Cl
I
I
C1
PEt3
17)
The monobridged dinuclear complex (7) with a PF2 bridge
was found to be a product of the reaction between PF2C1
and either rrans-[PtCIH(PEt3)2] or a mixture of trans[PtCl(Me3Si)(PEt3)2]and frans-[PtClz(PEt3),].
483
An attempt to prepare a dinuclear species with an SH
bridge by the action of SiMe3SH on trans-[PtClH(PEt&]
was unsuccessful but this complex was obtained by the
treatment of a mixture of tran~-[PtClH(PEt~)~]
and AgBF4
with rr~ns-[PtH(SH)(PEt~)~1[~!
This reaction, similar to that
used[’] to synthesise t r ~ n s - [ P t H ( P E t ~ ) ~ 1 ~ Cyielded
N + , the
complex (8) and AgCI. The selenium analog was prepared
similarly.
~ ~ U ~ ~ - [ P ~ H ( P E ~ ~ ) ~( ]8 ~) S H + B F ~
Received: May 5, 1977 [Z 730 IE]
German version: Angew. Chem. 89,495 (1977)
CAS Registry numbers:
(l).CI, 62906-17-6; (Z), 62906-16-5; ( 3 ) , 62906-15-4; ( 4 ) . A=CI, D=C1,
62960-63-8; ( 4 ) . A=Br, D = B r , 62960-62.1; ( 4 ) , A = I , D=I, 62960-61-6;
( 5 J. C = CI, D = C1, 62906-07-4; ( S ) , C = Br, D = Br. 62906-06-3;
( 5 ) . C=I, D = I , 62906-05-2; ( 6 ) . A=CI, C=CI, D = C I , 62906-04-1;
( 6 ), A = Br, C = Br, D = Br, 62906-03-0; (61, A = I, C = I, D = I, 62906-02-9;
( 7 ) . 62906-01-8; (8J.BF,,
Q = S , 62906-00-7; (8).BF,,
Q=Se,
62905-98-0; ( A J, 62990-74-3; rran~-[PtClH(PEt,)~], 16842-17-4; rrans[PtCl~(PEt3)2]. 13965-02-1; ~is-[PtC1~(PEt,)~], 15692-07-6; trans[ P ~ B T ~ ( P E ~ , ) ~13985-90-5;
],
t r a n ~ - [ P t l ~ ( P E t ~ ) ~15636-79-0;
].
rrans[PtCI(Me,Si)(PEt,),], 15559-62-3; Me,SiPHz, 17446-52-5; PFzCI, 14335-40-1;
Me,SiSH, 18338-27-7
P. L. Goggin, R. J . Goodfellow, F . J . S. Reed, J. Chem. Soc. Dalton
Trans. 1974. 576; P. L. Coggin, R. J. Goodfellow, S. R. Haddock, Chem.
Commun. 1975, 176.
[2] L. E . Manzrr, G. W Parshall, Inorg. Chem. 1 5 , 3114 (1976).
[3] J. M. Edward, Ph. D. Thesis, Edinburgh (1975).
[4] I. M . Blacklaws, E. A . !l Ebsworrh, D . W H. Rankin, H. E . Robertson,
unpublished work.
[I]
diffractometer, Stoe Stadi 21. The structure was solved by Patterson syntheses with least squares refinement (cf. Fig. 1);
R =7.32% for 7.59 of 759 possible reflections.
Primary structure: Half of the Zn atoms are in a tetrahedral
environment of 0 and the other half in a trigonal-planar
environment [dnteratomic distances: 2.01 A (4 x ), and 1.84,
1.92, and 1.97A, respectively].
Secondary structure: Surprisingly, “isolated tetranuclear
chains are present [ O Z n 0 , Z n 0 2 Z n O ~ Z n 0 ]which are almost
linear with respect to Zn. This is the first oligooxozincate.
Tertiary sfructure: The linear groups are oriented parallel
to one another along (120), being slightly inclined (ca. lo”)
towards (010).
Each [Zn408] group is surrounded by a total of 14 Rb
atoms which link them to 12 other such groups. The coordination number of Rb towards 02-is 4 (Rb-1, Rb-2, Rb-3) or
4 + 1 (Rb-4).
K2Zn607, which is likewise very sensitive to hydrolysis,
was obtained in studies on the ZnO rich side of the
K 2 Z n 0 2 / Z n 0 phase diagram in the form of coarse, slightly
yellow tinted single crystals [K:Zn = 2.2:3, closed Ni cylinders
(under argon), 7OO0C, 200dl; it forms tetragonal crystals with
a= 10.91,, ~ = 3 . 3 2 ~ A
c/a=0.30.5,
,
Z = 2 in P4, nm.
The I, data of 354 symmetry-independent reflections were
recorded (four-cycle diffractometer, Philips PW Z la),
and the
structure solved by direct methods (cf. Fig. 2); at the present
state of refinement R=8.52% for 297 of 354 possible reflections.
Coordination Number 3 in Oxozincates:
Rb8[OZn02Zn02Zn02Zn0] and K2[Zn6O7][’]
By Karl-Rainer Wambach and Rudolf Hopper*]
Although the amphoteric nature of Zn(OH)2has long been
known the only hydroxozincate to have been characterized in
detail is Na[Zn(OH)3] having the coordinate number .5[’]. A11
the oxozincates studied so far exhibit the coordination number
4, whether they are framework (BaZnOz[31, Na2Znz03’41),
layer (SrZn0,[51), chain (KzZn0,[61), or “soro” zincates
(Na6ZnO4f7I).We have now found a case of coordination
number 3 while searching for anions of unusual structure[’!
Rb2ZnO2,obtained from intimate mixtures of Rb00.48and
activeZnO [Rb:Zn=2.3:1,closed Nicylinders,60O0C, 50d) as
colorless, transparent, coarse single crystals of almost spherical
habit, proves to be extremely sensitive to hydrolysis and,
according to rotating crystal, Weissenberg, and precession
photographs, is monoclinic with a= 9.558, b= 6.335,
c=15.91 A,p=118.57, 2 = 8 in P2&.
For purposes of structure elucidation 759 symmetry-independent reflections hOLh41 were recorded [Mo-K,, two-cycle
- 2
0 Rbl
Fig. 2: Unit cell of K Z Z n 6 0 7 ,projection along [OOl]; heights in fractions
of c.
Primary structure: Two thirds of the Zn atoms are surrounded “tetrahedrally” by four 0 atoms, and the other third
in “trigonal-planar” fashion by threeso atoms [interatomic
distances: 1.88, 1.96, 2.04, and 2.07A, and 1.85, 1.93, and
2.08 respectively].
Secondary structure: The Z n 0 4 tetrahedra (with Zn-I) form
rings made up of tetrahedra parallel to (001) according to
A,
[ (0,,~(Zn03,~)12{02,~(ZnO~,2)}*{
Oli2(Zn03,2))z{02,~(Zn02,,,)21
Rb2
0
Rb3
@
Rb<
0
Zn 1
0
zn2
8
-
0 ‘
@ OZ
@ O3
(3 O L
Fig. 1. Unit cell of RbZZnOz, projection along [OIO]; heights in fractions
of b.
~~
[*] Prof. Dr. R. Hoppe, Dip].-Chem. K.-R. Wambach
lnstitut fur Anorganische und Analytische Chemie der Universitat
Heinrich-BUN-Ring 58, D-6300 Lahn-Giessen (Germany)
484
the atoms participating in ring formation being enclosed in
parentheses when they belong to a tetrahedron; different tetrahedra are indicated by curly brackets. Each ring contains
eight Zn atoms. Zn-0-Zn
groups (with Zn-2) are incorporated between opposite (Ol,2(Zn03,,)}, units of the rings in
such a way that the rings are subdivided by two trigonal
planar ZnO312 units.
Tertiary structure: The 0 atoms not participating in ring
formation are responsible for two-dimensional bridging parallel to (OOI), while along [Ool] the 0 atoms involved in ring
formation supplement these linkages to form a three-dimensional skeleton.
Angew. Chem. I n t . Ed. Engl. 16 ( 1 9 7 7 )
No. 7
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