Oxidative addition of α-bromoglycine to palladium(0) and platinum(0) complexes: α-metallated amino acids as models for intermediates in the metal-catalyzed hydrogenation of dehydroamino acids

Article abstract of DOI:10.1002/(SICI)1099-0682(199803)1998:3<375::AID-EJIC375>3.0.CO;2-9

Oxidative addition of methyl N-benzoyl-2-bromoglycinate to bis(dibenzylideneacetone)palladium, in the presence of 2,2′-bipyridyl, and to (Ph₃P)₂Pt(η²-C₂H₄) gives the α-metallated glycine esters 1a and 2a. Abstraction of bromide from 1a, 2a, using AgSbF₆ or AgBF₄, affords the cationic C,O-chelate complexes [(bpy)Pd-CH(CO₂Me)NHC(Ph)O]⁴ (1b,c) and [(Ph₃P)₂Pt-CH(CO₂Me)NHC(Ph)O]⁺ (2b), respectively, featuring coordination of the amide O atom. The complexes 1b and 2b have been characterized by X-ray diffraction.

Full text of DOI:10.1002/(SICI)1099-0682(199803)1998:3<375::AID-EJIC375>3.0.CO;2-9

FULL PAPER
Metal Complexes of Biologically Important Ligands, 101[᭛]
Oxidative Addition of α-Bromoglycine to Palladium(0) and Platinum(0)
Complexes: α-Metallated Amino Acids as Models for Intermediates in the
Metal-Catalyzed Hydrogenation of Dehydroamino AcidsȠ
Bernd Kayser, Christopher Missling, Jörg Knizek[2], Heinrich Nöth[2], Wolfgang Beck*
Institut für Anorganische Chemie der Ludwig-Maximilians-Universität,
Meiserstraße 1, D-80333 München, Germany
Received September 22, 1997
Keywords: α-Metallated amino acids / Palladium / Platinum / Oxidative addition / α-Bromoglycinate
Oxidative addition of methyl N-benzoyl-2-bromoglycinate to
bis(dibenzylideneacetone)palladium, in the presence of 2,2Ј-
bipyridyl, and to (Ph3P)2Pt(η2-C2H4) gives the α-metallated
complexes [(bpy)PdϪCH(CO2Me)NHC(Ph)O]+ (1b,c) and
[(Ph3P)2PtϪCH(CO2Me)NHC(Ph)O]+ (2b), respectively, fea-
turing coordination of the amide O atom. The complexes 1b
glycine esters 1a and 2a. Abstraction of bromide from 1a, 2a, and 2b have been characterized by X-ray diffraction.
using AgSbF6 or AgBF4, affords the cationic C,O-chelate
α-Haloglycine esters are valuable synthons for the synthesis (Ph3P)2Pt(η2-C2H4) yielded the α-metallated complexes 1a
of modified α-amino acids[3]. Recently, we used these com- and 2a, respectively, in good yields. The compounds were
pounds for the introduction of α-amino acid residues into found to be light-sensitive and relatively unstable in air and
organometallic systems[4], giving products that may find ap- towards organic solvents. Abstraction of bromide from 1a,
plication in the labelling of amino acids and peptides, a 2a, using AgSbF6 or AgBF4, led to coordination of the am-
growing field in bioinorganic chemistry[5]. α-Metallated ide group, thereby affording the stable C,O-chelate com-
amino acids are intermediates in the asymmetric hydrogen- plexes 1b,c and 2b.
ation of dehydroamino acids and have been detected as such
The IR spectra of 1a and 2a show typical ester and amide
by Halpern et al.[6] and Brown et al.[7] by means of NMR
absorptions at 1715 and 1640 cmϪ1. The shift of the car-
spectroscopy.
bonyl ester band to lower wavenumbers (ν˜ ഠ 30 cmϪ1) com-
pared with the corresponding band in α-amino acid esters
Structures of α-metallated amino acids have been re-
ported by Vahrenkamp et al.[8] and by ourselves[4b]. Re-
has been observed previously[4b]. The lower wavenumber of
cently, Bergens et al.[9] characterized a C,O-bound inter-
the amide absorption in 1b,c and 2b (1600 cmϪ1) is charac-
mediate in the hydrogenation of methyl α-acetamidocinna-
1
teristic of a coordinated amide group. The H-NMR spec-
mate, derived from a (BINAP)(H)RuII catalyst.
trum of 1a exhibits a doublet due to the CH proton, as
The easy access to α-metallated amino acids by oxidative
expected, while that of complex 1c features a broad singlet.
addition of methyl N-benzoyl-2-bromoglycinate to
The signal of the PtϪCH proton in 2a appears as a
Me2Pt(bpy) (bpy ϭ 2,2Ј-bipyridyl)[4b] prompted us to
pseudo-quadruplet with satellites due to 195PtϪCϪH coup-
search for square-planar complexes with the halide and the
1
ling. In the H-NMR spectrum of 2b, a doublet of triplets
C-bound α-amino acid in a cis configuration. Abstraction
of halide from these should yield simple models for inter-
mediates in the hydrogenation of dehydroamino acids, with
is observed for the α-CH proton due to cis and trans
31PϪPtϪCϪH coupling.
The 13C-NMR spectra of 1c and 2b show the expected
coordination of the amide O atom.
resonances. Two 31P-NMR signals for the two non-equiva-
The oxidative addition of organic halides to zerovalent
lent P atoms are observed for 2b. Their 1J(PtϪP) values
differ significantly because of the different trans influence
of the strong C and weak O donors, similar to the situation
palladium and platinum complexes[10], e.g. to (Ph3P)2Pt(η2-
C2H4)[11] or to (dba)2Pd (dba ϭ dibenzylideneacetone)[12]
is a general method for the synthesis of σ-bonded or-
ganometallic complexes.
in (Ph3P)2PtϪC(H)(CO2R)C(O)O[13]
.
Cationic alkyl- or acyl(bpy)PdII complexes readily react
with CO, isonitriles, alkenes or allenes[14]. Surprisingly, 1a
does not undergo insertion of CO, ethylene or allene at at-
mospheric pressure. Treatment with tert-butylisonitrile
leads only to coordination of the isonitrile {ν˜ ϭ 2222 cmϪ1
[ν(CN)]} and no insertion product could be detected.
Results and Discussion
The reactions of methyl N-benzoyl-2-bromoglycinate
with (dba)2Pd in the presence of bpy, and with
[᭛]
Part 100: Ref.[1]
.
Eur. J. Inorg. Chem. 1998, 375Ϫ379
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ1948/98/0303Ϫ0375 $ 17.50ϩ.50/0
375

B. Kayser, C. Missling, J. Knizek, H. Nöth, W. Beck
FULL PAPER
Figure 1. Molecular structure of 1b[a]
[a]
Selected bond lengths [pm] and angles [°]: Pd1ϪN2 205.2(5), Pd1ϪN3 201.9(5), Pd1ϪO1 201.3(4), Pd1ϪC1 203.3(6), O1ϪC3 127.5(7),
C3ϪN1 132.2(8), N1ϪC1 146.0(8); N2ϪPdϪN3 80.0(2), O1ϪPd1ϪC1 82.4(2), Pd1ϪC1ϪN1 104.2(4), Pd1ϪO1ϪC3 113.4(4).
Crystal Structure Determinations of 1b and 2b
The palladium center in 1b has a square-planar environ-
Crystals suitable for structure determination by X-ray ment with PdϪN distances (203Ϫ205 pm) similar to those re-
diffraction were obtained by liquid-liquid diffusion of di- ported for related complexes[12][15]. The PdϪC distance
ethyl ether into an acetone solution of 1b at room tempera- [203.3(6) pm] compares well with values found for other sp3
ture and from a dichloromethane solution of 2b layered carbon atoms trans to an sp2 nitrogen atom[15]. The acyl CO
with n-pentane. The unit cell of 1b was found to contain bond length [127.5(7) pm] is typical for a carbonyl group, al-
the αS and αR enantiomers (at C1), with a parallel arrange- though the CO absorption in the IR spectrum (1602 cmϪ1) is
ment of the molecules and pairs of enantiomers (with a suggestive of more single-bond character. The α-carbon atom
center of symmetry, Pd···Pd 427 pm) in the lattice. As ex- is approximately tetrahedrally coordinated, with the largest
pected on the basis of the spectroscopic data, the amino deviation from ideal geometry being manifested in the
acid is coordinated to the Pd atom through the α-carbon NϪCϪPd angle (104°). The chelate ring is almost planar and
atom and the amide group (Figure 1).
has a (small) OϪCϪNϪC torsion angle of 11.7°.
376
Eur. J. Inorg. Chem. 1998, 375Ϫ379

Metal Complexes of Biologically Important Ligands, 101
Figure 2. Structure of 2b[a]
FULL PAPER
[a]
Selected bond lengths [pm] and angles [°]: Pt1ϪP1 232.8(2), Pt1ϪP2 223.3(2), Pt1ϪO1 208.9(4), Pt1ϪC1 210.0(6), O1ϪC4 128.1(7),
C4ϪN1 130.9(8), N1ϪC1 146.0(8); P1ϪPt1ϪP2 99.91(6), C1ϪPt1ϪO1 80.8(2), Pt1ϪC1ϪN1 104.4(4), Pt1ϪO1ϪC4 112.1(4).
Table 1. Details of the crystal structure determinations[17]
A similar structure is found for 2b. The two P atoms in
2b are seen to deviate from the coordination plane by 18°
and 3.4°, respectively. The PtϪα-C bond length [210.0(6)
pm] is comparable to that found in other platinum(II) com-
1b
2b
Formula
C20H18F6N3O3PdSb C46H40F6NO3P2PtSb
plexes with PtϪα-alkyl bonds[16]
.
Mr
690.52
monoclinic
P2(1)/c
8.422(2)
18.357(4)
14.958(3)
90°
105.643(9)
90°
2227.0(9)
4
1147.57
triclinic
Crystal system
Space group
Interestingly, pairs of enantiomers αS and αR are found
in the crystal (Figure 2), which are linked through two hy-
drogen bonds between the amino and the carbonyl groups
of the methyl ester (NϪH···O 286 pm).
¯
P1
˚
a [A]
11.9029(1)
12.4852(1)
16.3340(1)
94.012(1)
92.620(1)
114.292(1)
2199.64(3)
2
˚
b[A]
c[A]
˚
α [°]
β [°]
γ [°]
Support by the Deutsche Forschungsgemeinschaft and the Fonds
der Chemischen Industrie is gratefully acknowledged. We thank
Professor Dr. W. Steglich, München, for valuable discussions.
V [A3]
˚
Z
ρcalcd. [gcmϪ3
]
2.060
2.099
1.733
3.930
µ [mmϪ1
]
Experimental Section
Crystal size
2θ range [°]
Index range
0.2 ϫ 0.15 ϫ 0.12 0.3 ϫ 0.3 ϫ 0.2
General: All reactions were carried out in dry solvents under
argon. Ϫ NMR: Jeol GSX 270 (1H 270.0; 13C 100.4; 31P 109.3
MHz) with tetramethylsilane as internal standard; H3PO4 (85%) as
external standard. Ϫ IR: 5ZDX FT-IR. Ϫ (dba)2Pd[18], (η2-ethyl-
ene)(Ph3P)2Pt[19] and methyl N-benzoyl-2-bromoglycinate[3b] were
prepared according to literature procedures. AgBF4 and AgSbF6
were purchased from Aldrich and stored in the dark under argon.
3.6Ϫ58.8
±h, ±k, ±l
6146
3.6Ϫ58.8
±h, ±k, ±l
13135
Collected reflns.
Independent reflns.
[Rint (%)]
Max./min.
transmissions
Parameters
4281 [2.45]
7027 [3.21]
0.727/0.606
0.710/0.497
307
596
R1/wR2 [F > 4σ(F)]
GoF
0.0488/0.0914
1.368
0.445/Ϫ0.502
0.0424/0.1039
1.139
1.685/Ϫ2.364
(bpy)[CH(NHCOPh)(CO2Me)]PdBr (1a): To a solution of
173 mg (0.3 mmol) of (dba)2Pd in 10 ml of benzene, 47 mg (0.3
mmol) of 2,2Ј-bipyridyl and 82 mg (0.3 mmol) of methyl N-ben-
zoyl-2-bromoglycinate were added. The mixture was stirred for 1 h
Largest diff. peak
and hole [eAϪ3
]
˚
Eur. J. Inorg. Chem. 1998, 375Ϫ379
377

B. Kayser, C. Missling, J. Knizek, H. Nöth, W. Beck
FULL PAPER
at room temp., during the course of which a yellow-green powder
2243.5 Hz). Ϫ C46H40F6NO3P2PtSb (1147.6): calcd. C 48.14, H
precipitated. The precipitate was separated by centrifugation, 3.51, N 1.22; found C 48.53, H 3.89, N 1.24.
washed with diethyl ether (2 ϫ 10 ml), and dried in vacuo. Yield
Crystal Structure Determinations: A suitable single crystal of 1b
128 mg (80%), yellow-green powder, m.p. 164°C. Ϫ IR (KBr): ν˜ ϭ
or 2b was mounted on a glass fibre with perfluoroether oil. After
cooling to Ϫ80°C, the crystal was optically centered on a Siemens
P4 four-circle diffractometer equipped with a CCD area detector.
The dimensions of the unit cell were determined from the observed
reflections (> 10 σ) in 4 ϫ 15 frames with different ψ and χ orien-
tations. Data collection was performed with 10-s exposures at two
different χ settings with ∆ψ intervals of 0.3° (altogether 1296
frames). Data reduction was performed with the program SAINT
of Siemens Analytical Instruments, and a semiempirical absorption
correction was applied. The structures were solved by the heavy-
atom method and successive Fourier synthesis using the SHELX-
93 program (G.W. Sheldrick, University of Göttingen). All non-
hydrogen atoms were refined anisotropically. H atoms bound to
carbon atoms were placed in calculated positions and refined with
a riding model. N-bonded H atoms were located in the difference
Fourier synthesis and were freely refined with a fixed isotropic N.
Selected crystallographic data and data relating to the structure
solutions and refinement are summarized in Table 1.
3407 cmϪ1 m (NH), 1716 s (CO2), 1633 s (NCO). Ϫ 1H NMR
3
(CDCl3): δ ϭ 3.74 (s, 3 H, CH3), 5.32 (d, J ϭ 9.2 Hz, 1 H, CH),
7.36Ϫ7.49 (m, 4 H, NH, C6H5), 7.57Ϫ7.74 (m, 2 H, bpy),
7.86Ϫ8.21 (m, 6 H, bpy, C6H5), 9.25 (d, 3J ϭ 3.94 Hz, 1 H, o-bpy),
9.35 (d, 3J ϭ 5.4 Hz, 1 H, o-bpy). Ϫ C20H18N3O3BrPd·0.5C6H6
(573.8): calcd. C 48.15, H 3.69, N 7.32; found C 47.97, H 3.71,
N 7.26.
[CH(NHCOPh)(CO2Me)](PPh3)2PtBr (2a): To a solution of
224 mg (0.3 mmol) of (η2-ethylene)(Ph3P)2Pt in 10 ml of benzene,
82 mg (0.3 mmol) of methyl N-benzoyl-2-bromoglycinate was ad-
ded. Gas evolution was observed and the yellow solution was
stirred for 1 h. A white residue was separated by centrifugation,
the volatiles were evaporated from the supernatant solution, and
the residue was washed with pentane (3 ϫ 15 ml). Yield 268 mg
(90%), white powder, m.p. 104°C (decomp.). Ϫ IR (KBr): ν˜ ϭ 3413
1
cmϪ1 m (NH), 1713 s (CO2), 1647 s (NCO), 280 m (PtBr). Ϫ H
3
NMR (C6D6): δ ϭ 3.78 (s, 3 H, CH3), 5.44 (pseudo-q, JPH ϭ 9.7
2
Hz, JPtH ϭ 93.6 Hz, 1 H, CH), 6.94Ϫ8.74 (m, 36 H, NH, C6H5,
1
PPh3). Ϫ 31P NMR (C6D6): δ ϭ 17.90 (d, 2JPP ϭ 16.5 Hz, JPtP
ϭ
Ƞ
Dedicated to Professor Wolfgang Herrmann, as a mark of
2
1
1902.9 Hz), 20.45 (d, JPP ϭ 16.5 Hz, JPtP ϭ 4481.5 Hz). Ϫ
C46H40NO3BrP2Pt (991.8): calcd. C 55.71, H 4.07, N 1.41; found
C 55.51, H 4.76, N 1.75.
friendship and respect, on the occasion of his 50th birthday.
[1]
K. Severin, R. Bergs, W. Beck, Angew. Chem., in press.
[2]
X-ray diffraction measurements.
[3] [3a]
R. Kober, W. Steglich, Liebigs Ann. Chem. 1983, 599Ϫ609.
[3b]
General Procedure for the Abstraction of Bromide from 1a and
2a: To a solution of 160 mg (0.3 mmol) of 1a [or 297 mg (0.3 mmol)
of 2a] in 10 ml of acetone, a solution of 58 mg (0.3 mmol) of AgBF4
or 103 mg (0.3 mmol) of AgSbF6 in 5 ml of acetone was added.
Reaction was indicated by the rapid precipitation of AgBr; the sus-
pension was stirred for 1 h in the dark at room temp. and then the
precipitate was separated by centrifugation. The colorless/yellow
solution was concentrated in vacuo and the residue was washed
with diethyl ether (1b,c) or pentane (2b) (2 ϫ 15 ml) and dried
in vacuo.
Ϫ
R. Kober, K. Papadopoulos, W. Miltz, D. Enders, W.
[3c]
Steglich, Tetrahedron 1985, 41, 1693Ϫ1701. Ϫ
P. Münster,
W. Steglich, Synthesis 1987, 223Ϫ225. Ϫ [3d] G. Apitz, M. Jäger,
S. Jaroch, S. Kratzel, L. Schäffeler, W. Steglich, Tetrahedron
[3e]
1993, 49, 8223Ϫ8232. Ϫ
Th. Bretschneider, W. Miltz, P.
Münster, W. Steglich, Tetrahedron 1988, 44, 5403Ϫ5414. Ϫ
[3f]
V. A. Burgess, C. J. Easton, M. P. Hay, P. J. Steel, Aust. J.
Chem. 1988, 41, 701Ϫ710. Ϫ [3g] S. Jaroch, T. Schwarz, W. Steg-
lich, P. Zistler, Angew. Chem. 1993, 105, 1803Ϫ1805; Angew.
Chem. Int. Ed. Engl. 1993, 32, 1771.
[4] [4a]
B. Kayser, K. Polborn, W. Steglich. W. Beck, Chem. Ber.
[[4b]
1997, 130, 171Ϫ177. Ϫ
B. Kayser, H. Nöth, M. Schmidt,
G. Jaouen, A. Vessieres, I. S. Butler, Acc. Chem. Res. 1993,
W. Steglich, W. Beck, Chem. Ber. 1996, 129, 1617Ϫ1620.
[5] [5a]
Ϫ
[(bpy)PdϪCH(CO2Me)NHC(Ph)O]ϩ BF4 (1c): Yield 154
´
[5b]
26, 361Ϫ369. Ϫ
M. Salmain, M. Gunn, A. Gorfti, S. Top,
mg (95%), colorless powder, m.p. 193°C (decomp.). Ϫ IR (KBr):
[5c]
G. Jaouen, Bioconjugate Chem. 1993, 4, 425Ϫ433. Ϫ
A.
ν˜ ϭ 3410 cmϪ1 m (NH), 1707 s (CO2), 1602 s (NCO), 1083
Gorfti, M. Salmain, G. Jaouen, M. J. McGlinchey, A.
(BF4Ϫ). Ϫ H NMR (CDCl3 ϩ DMSO): δ ϭ 3.33 (s, 3 H, CH3),
1
Bennouna, A. Mousser, Organometallics 1996, 15, 142Ϫ151. Ϫ
[5d]
3
A. J. Gleichmann, J. M. Wolff, W. S. Sheldrick, J. Chem.
4.57 (s, 1 H, CH), 7.14Ϫ7.43 (m, 5 H, Ph, bpy), 7.71 (d, J ϭ 7.6
[5e]
Soc., Dalton Trans. 1995, 1549Ϫ1554. Ϫ
J. M. Wolff, A. J.
3
Hz, 2 H, Ph), 7.92 (pseudo-q, J ϭ 7.7 Hz, 2 H, bpy), 8.01Ϫ8.11
Gleichmann, W. S. Sheldrick, J. Inorg. Biochem. 1995, 59, 219.
3
3
(m, 2 H, bpy), 8.43 (d, J ϭ 5.5 Hz, 1 H, bpy), 8.71 (d, J ϭ 5.2
Hz, 1 H, bpy), 9.77 (s, 1 H, NH). Ϫ 13C NMR (CDCl3 ϩ DMSO):
δ ϭ 50.86, 51.25 (CH, CH3), 122.30, 122.98, 126.64, 126.71, 126.73,
127.77, 128.07, 132.89, 140.07, 140.44, 147.62, 152.66, 152.71,
[5f]
Ϫ
J. M. Wolff, W. S. Sheldrick, Chem. Ber. 1997, 130,
[5g]
981Ϫ988; J. Organomet. Chem. 1997, 531, 141Ϫ149. Ϫ
R.
M. Schweiger, T.
Krämer, Angew. Chem. 1996, 108, 1287Ϫ1289; Angew. Chem.
[5h]
Int. Ed. Engl. 1996, 35, 1197Ϫ1199. Ϫ
Ederer, K. Sünkel, W. Beck, J. Organomet. Chem., in press.
155.72 (bpy, Ph), 173.90, 178.63 (CO2, NCO).
Ϫ
[6] [6a]
A. S. C. Chan, J. J. Pluth, J. Halpern, Inorg. Chim. Acta
[6b]
C20H18BF4N3O3Pd (541.6): calcd. C 44.35, H 3.35, N 7.76; found
C 43.89, H 3.17, N 7.61.
1979, 37, L477ϪL479. Ϫ
A. S. C. Chan, J. Halpern, J. Am.
[6c]
Chem. Soc. 1980, 102, 838Ϫ840. Ϫ
Chem. 1983, 55, 99Ϫ196.
J. Halpern, Pure Appl.
[7a] J. M. Brown, P. A. Chaloner, J. Chem. Soc., Chem. Commun.
[7]
[(Ph3P)2PtϪCH(CO2Me)NHC(Ph)O]ϩ SbF6Ϫ (2b): Yield 309
mg (90%), colorless powder, m.p. 158°C (decomp.). Ϫ IR (KBr):
ν˜ ϭ 3437 cmϪ1 m (NH), 1709 m (CO2), 1607 m (NCO), 1098
(SbF6Ϫ). Ϫ 1H NMR (CDCl3): δ ϭ 3.27 (s, 3 H, CH3), 5.44 (dt,
1980, 344Ϫ346. Ϫ [7b] J. M. Brown, P. J. Maddox, J. Chem. Soc.,
[7c]
Chem. Commun. 1987, 1276Ϫ1278. Ϫ
J. M. Brown, Chem.
Soc. Rev. 1993, 22, 25Ϫ41. Ϫ [7d] J. A. Ramsden, T. D. W. Clar-
idge, J. M. Brown, J. Chem. Soc., Chem. Commun. 1995,
2469Ϫ2471.
3
3
2
3J(PH)trans ϭ 9.9 Hz, J(PH)cis ϭ 2.1 Hz, JHH ϭ 2.1 Hz, JPtH
ϭ
[8] [8a]
D. Mani, H.-T. Schacht, A. Powell, H. Vahrenkamp, Or-
46.8 Hz, 1 H, CH), 7.00Ϫ7.71 (m, 35 H, PPh3, Ph), 8.24 (pd,
[8b]
ganometallics 1987, 6, 1360Ϫ1361. Ϫ
Schacht, A. K. Powell, H. Vahrenkamp, Chem. Ber. 1989, 122,
2245Ϫ2251.
D. Mani, H.-T.
3
4JPH ϭ 6.5 Hz, JHH ϭ 2.1 Hz, 1 H, NH). Ϫ 13C NMR (CDCl3):
2
2
δ ϭ 50.62 (CH3), 62.82 (dd, J(PC)trans ϭ 81.8 Hz, J(PC)cis ϭ 3.6
Hz, CH), 127.57Ϫ134.87 (m, 42 C, PPh3, Ph), 173.64 (d,
[9]
J. A. Wiles, S. H. Bergens, J. Am. Chem. Soc. 1997, 119,
2940Ϫ2941.
A. J. Canty, G. K. Anderson, in Comprehensive Organometallic
Chemistry II (Eds.: E. W. Abel, F. G. A. Stone, G. Wilkinson),
Pergamon Press, 1995, 9, 225, 431.
3J(PC)trans ϭ 4.7 Hz, CO2), 180.78 (dd, J(PC)trans ϭ 10.6 Hz,
3
[10]
3J(PC)cis ϭ 3.4 Hz, NCO). Ϫ 31P NMR (CDCl3): δ ϭ 8.33 (d, 2JPP ϭ
1
2
1
19.8 Hz, JPtP ϭ 4223.1 Hz), 22.87 (d, JPP ϭ 19.8 Hz, JPtP
ϭ
378
Eur. J. Inorg. Chem. 1998, 375Ϫ379

Metal Complexes of Biologically Important Ligands, 101
FULL PAPER
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J. P. Birk, J. Halpern, A. L. Pickard, J. Am. Chem. Soc. 1968,
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90, 4491Ϫ4492; A. R. Siedle, R. A. Newmark, W. B. Gleason,
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B. A. Markies, A. J. Canty, W. de Graaf, J. Boersma, M. D.
[16]
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