Reactions of N-phenyl-o-semiquinonediimine complexes of nickel and platinum with carbonyl-containing low-valence iron and rhenium compounds

Article abstract of DOI:10.1023/A:1009549807222

The reactions of o-semiquinonediimine complexes M[o-(NH)(NPh)C₆H₄]₂ (M = Ni (1) or Pt (2)) with carbonyl-containing iron and rhenium compounds were studied. The reactions of complexes 1 or 2 with Fe(CO)₅ afforde

Full text of DOI:10.1023/A:1009549807222

142
Russian Chemical Bulletin, International Edition, Vol. 50, No. 1, pp. 142—146, January, 2001
Reactions of N-phenyl-o-semiquinonediimine complexes
of nickel and platinum with carbonyl-containing
low-valence iron and rhenium compounds
A. V. Reshetnikov, M. O. Talismanova, A. A. Sidorov, S. E. Nefedov,« I. L. Eremenko, and I. I. Moiseev
N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 117907 Moscow, Russian Federation.
Fax: +7 (095) 954 1279. E-mail: snef@ionchran.rinet.ru
The reactions of o-semiquinonediimine complexes M[o-(NH)(NPh)C6H4]2 (M = Ni (1)
or Pt (2)) with carbonyl-containing iron and rhenium compounds were studied. The reactions
of complexes 1 or 2 with Fe(CO)5 afforded the Fe2(CO)6[µ-(NH)(NPh)C6H4] complex (3)
containing the bridging N-phenyl-o-phenylenediamide ligand in high yield. The reaction of
the Re(CO)2(NO)Cl2(thf) complex with complex 2 gave rise to the unusual mononuclear
rhenium(III) complex, viz., Re(Ph)[σ-η1-o-(NH)(NHPh)C6H4](CO)(NO)Cl2 (4), no changes
in the geometry of N-phenyl-o-phenylenediamine bound to the Re(NO)(CO)2Cl2 fragment
being observed. The reaction of complex 2 with the Re(CO)5Cl complex, which has been
preliminarily treated with silver triflate, afforded the heterometallic complex (CO)Pt[µ-N,N-o-
(N)(NPh)C6H4]2ReCl[(NH)(NPh)C6H4]. The structures of the resulting complexes were
established by X-ray diffraction analysis.
Key words: redox transformations of coordinated ligands, î-semiquinonediimine nickel
and platinum complexes, heterometallic compounds, synthesis, structure.
Scheme 1
One of convenient procedures for the chemical de-
sign of heterometallic complexes and clusters of transi-
tion metals involves the use of metal-containing frag-
ments as ligands with respect to other organometal-
lic molecules. In this regard, the î-semiquinonedi-
imine complexes of nickel(II) and platinum(II), viz.,
M[o-(NH)(NPh)C6H4]2 (M = Ni (1) or Pt (2)), which
we have synthesized previously, may serve as promising
starting blocks for the preparation of heterometallic
complexes. We attempted to introduce these compounds
into the reactions with moieties containing metal atoms
in low oxidation states with the aim of preparing
heterometallic compounds. The formation of the latter
can also be accompanied by conversions of the coordi-
nated semiquinonediimine ligand. In the present work,
we report the reactions of complexes 1 and 2 with
Fe(CO)5, Re(CO)2(NO)Cl2(thf), and Re(CO)5Cl.
Ph
N
H
N
Fe(CO)5
–
–
M
i
••
N
H
N
Ph
1: M = Ni
2: M = Pt
Products
of reduction of M
+
HN
NPh
(OC)3Fe
Fe(CO)3
3
Conditions: i. Benzene, refluxing.
Results and Discussion
We found that refluxing of complexes 1 or 2 in the
presence of Fe(CO)5 in benzene resulted in the transfer
of the N-phenyl-o-semiquinonediimine ligand to the
iron atoms and its reduction, giving rise to the diamag-
netic binuclear complex Fe2(CO)6[µ-(NH)(NPh)C6H4]
(3) (Scheme 1).
According to the X-ray diffraction data, two Fe(CO)3
fragments in complex 3 are held together by the Fe—Fe
bond (2.372(2) Å) supplemented with the amide bridges
formed by the nitrogen atoms of the N-phenyl-o-
phenylenediamide ligand (Fe—N, 1.977(6)—2.022(6) Å).
The reaction was accompanied by oxidation of the iron
atoms and reduction of the coordinated î-semi-
quinonediimine ligand and the nickel(II) (to Ni(CO)4)
or platinum(II) atoms (platinum black was formed). It
should be noted that complex 3 has been isolated previ-
ously1 in the reaction of iron carbonyl with azobenzene.
However, the reaction under study afforded complex 3
in higher yield (40% with respect to the ligand).*
* The crystallographic and geometric parameters of complex 3
correspond to those reported previously.1
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 136—140, January, 2001.
1066-5285/00/5001-0142 $25.00 © 2001 Plenum Publishing Corporation

N-Phenyl-o-semiquinonediimine complexes
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 1, January, 2001
143
More profound conversions of the coordinated N-phe-
nyl-î-semiquinonediimine ligand occurred in the reaction
of complex 2 with the nitrosyl carbonyl chloride rhenium(I)
complex Re(CO)2(NO)Cl2(thf) in boiling toluene con-
taining 2—3% of water to form the diamagnetic complex
Re(Ph)[(σ-η1-o-(NH)(NHPh)C6H4](CO)(NO)Cl2 (4) in
48% yield:
troduced into the direct reaction with the dimeric carbo-
nyl nitrosyl chloride rhenium complex; instead, only the
complex Re[η1-(NH2)(NHPh)C6H4](CO)2(NO)Cl2 (5)
was obtained in high yield (Scheme 2).
Scheme 2
NHPh
O
ON
OC
Cl
Cl
ON
Cl
Cl
NH2
Re
NO
Re
Cl
Cl
i
Re
CO
Re
2
+
OC
OC
CO
CO
ON
OC
Cl
Cl
Cl
Cl
i
OC
Re
NO
L
PhNH
NH
CO
5
ii
NHPh
4
Conditions: i. toluene, 2—3% H2O.
NH2
Re
ON
OC
Cl
Cl
According to the X-ray diffraction data (Fig. 1), the
rhenium atom in complex 4 is coordinated by two
chlorine atoms (Re—Cl, 2.426(5) and 2.431(5) Å), the
nitrosyl group (Re—N, 1.789(17) Å), and the carbonyl
group (Re—C, 1.787(17) Å). The environment about the
rhenium atom is completed to an octahedron with two
atoms occupying axial positions, viz., with the nitrogen
atom (Re—N, 2.184(11) Å) involved in the reduced
N-phenyl-o-phenyleneaminoamide ligand and the car-
bon atom (Re—C, 2.155(11) Å) of the σ-bound phenyl
fragment, which was, apparently, formed as a result of
the cleavage of the N—Ph bond in the initial coordi-
nated î-semiquinonediimine ligand.
NH2
PhHN
6
L = N-phenyl-o-phenylenediamine.
Conditions: i. toluene, 20 °C; ii. toluene, 120 °C.
According to the X-ray diffraction data (Fig. 2), the
rhenium atom in complex 5 is coordinated by two
chlorine atoms (Re—Cl, 2.399(3) and 2.419(3) Å), the
nitrosyl group (Re—N, 1.831(11) Å), two carbonyl groups
(Re—C, 1.912(10) and 2.036(13) Å), and the nitrogen
atom of the amino group of N-phenyl-î-phenylenedi-
It should be noted that no conversions of free
N-phenyl-o-phenylenediamine occurred when it was in-
C(17)
C(16)
C(18)
C(15)
C(19)
C(6)
C(5)
C(7)
C(14)
Cl(1)
C(14)
C(4)
C(13)
C(12)
C(9)
C(8)
C(3)
Re(1)
N(3)
C(10)
C(1)
C(11)
Cl(2)
O(1)
N(1)
N(2)
C(10)
C(12)
C(9)
O(2)
N(2)
N(1)
C(1)
O(2)
Re(1)
O(1)
N(3)
C(7)
C(11)
C(8)
C(13)
C(2)
Cl(1)
Cl(2)
C(3)
C(4)
C(2)
O(3)
C(6)
C(5)
Fig. 1. Structure of complex 4.
Fig. 2. Structure of complex 5.

144
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 1, January, 2001
Reshetnikov et al.
C(5)
occupied by two nitrogen atoms of the amino groups of
two N-phenyl-o-phenylenediamine ligands (Re—N,
2.168(8)—2.188(9) Å).
C(4)
C(3)
C(12)
C(11)
C(6)
C(13)
C(8)
The heterometallic binuclear (OC)Pt[µ-N,N-î-
(N)(NPh)C6H4]2ReCl[(NH)(NPh)C6H4] complex (7)
was formed in the reaction of complex 2 with the
mononuclear rhenium(I) complex, viz., Re(CO)5Cl,
which has been preliminarily treated with silver triflate
upon UV irradiation in m-xylene (80 °C) (Scheme 3).
C(2)
C(7)
N(3)
N(2)
Cl(2)
C(10)
C(9)
N(1)
O(1)
C(1)
O(2)
Cl(1)
Re(1)
N(4)
C(24)
C(25)
C(20)
N(5)
C(19)
Scheme 3
C(14)
C(15)
C(21)
C(22)
C(23)
C(18)
C(17)
C(16)
OC
Fig. 3. Structure of complex 6.
Cl
N
NPh
NH
Re(CO)5Cl, CF3SO3Ag
2
Pt
Re
i
PhN
N
amine (Re—N, 2.204(9) Å). The geometry of the latter
is completely identical to that of the free ligand.2
One would expect that heating of complex 5 in
toluene in air will lead to elimination of the CO group
and to oxidation of the resulting chelate-coordinated
ligand by oxygen giving rise to the î-semiquinonediimine
fragment, analogously to the conversions observed in the
syntheses of complexes 1 and 2.
PhN
7
Conditions: i. hν, m-xylene, 80 °C.
However, it appeared that refluxing of complex 5 in
toluene afforded the disproportionation product of 5,
viz., the Re[η1-(NH2)(NHPh)C6H4]2(CO)(NO)Cl2 com-
plex (6), in low yield.
According to the X-ray diffraction data, the geom-
etry of the Re(NO)(CO)Cl2 fragment in complex 6
(Fig. 3) is virtually identical to that in complex 5
(Re—Cl, 2.431(2)—2.442(3) Å; Re—N, 1.853(8) Å; and
Re—C, 1.850(8) Å). However, the axial positions in the
environment about the rhenium atom in complex 6 are
According to the data of X-ray diffraction study of
complex 7 (Fig. 4), the platinum and rhenium atoms
in the molecule are linked through a direct bond
(3.055(1) Å), which is supplemented with two chelate-
bridging N-phenyl-o-quinoneiminoimide ligands (L). The
imide nitrogen atoms in these ligands are coordinated to
both metal atoms (Pt—N, 2.006(6) and 2.004(6) Å;
Re—N, 2.019(5) and 1.894(5) Å; and N=C, 1.339(10)
and 1.363(11) Å). The chelate coordination of the ligands
to the rhenium and platinum atoms is achieved through
C(21)
C(20)
C(19)
C(22)
Cl
C(17)
O(1)
C(18)
C(23)
N(3)
C(16)
C(12)
C(11)
C(15)
Pt(1)
N(4)
H(6a)
C(14)
C(3)
C(2)
N(6)
Re(1)
N(2)
N(1)
C(13)
C(28)
C(4)
C(8)
N(5)
C(1)
C(24)
C(30)
C(31)
C(7)
C(9)
C(27)
C(5)
C(6)
C(12)
C(22)
C(23)
C(25)
C(21)
C(26)
C(10)
C(11)
C(29)
C(32)
Fig. 4. Structure of complex 7.

N-Phenyl-o-semiquinonediimine complexes
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 1, January, 2001
145
a solution of Pt[î-(NH)(NPh)C6H4]2 (0.21 g, 0.37 mmol) in
toluene (30 mL) containing 2—3% of water and the reaction
mixture was refluxed for 1 h. The resulting green solution was
concentrated to 10 mL at 50 °C (0.1 Torr) and kept at 5 °C for
one day. The crystals that precipitated were separated from the
solution by decantation, washed with hexane, and dried in
vacuo. (N-Phenyl-î-phenyleneaminoamide)nitrosylcarbonyl-
phenyl-cis-dichlororhenium(III) (4) was obtained in a yield
of 0.12 g (48%). Found (%): C, 40.2; H, 3.1; N, 6.9.
C19H16Cl2N3O2Re. Calculated (%): C, 39.66; H, 2.80; N, 7.30.
Reaction of î-(NH2)(NHPh)C6H4 with [Re(NO)(CO)2Cl2]2.
A solution of î-(NH2)(NHPh)C6H4 (0.26 g, 1.40 mmol) in
toluene (10 mL) was added to a solution of [Re(NO)(CO)2Cl2]2
(0.43 g, 0.63 mmol) in toluene (60 mL). The reaction mixture
was stirred at ∼20 °C for 1 h. The resulting dark-brown solution
was concentrated to 10 mL at 50 °C (0.1 Torr) and cooled to
∼20 °C. The crystals that precipitated were separated from the
solution by decantation, washed with hexane, and dried at 20 °C
(0.1 Torr). (N-Phenyl-î-phenylenediamine)nitrosyl-cis-dicar-
bonyl-cis-dichlororhenium(I) (5) was isolated in a yield of 0.33 g
the N atoms of the NPh group (Pt—N, 2.026(8) Å; and
Re—N, 2.076(5) Å). In spite of this mode of coordina-
tion, both bridging L ligands, like the third N-phenyl-o-
quinonediimine ligand, which is coordinated only to the
Re atom (Re—N, 1.997(9) and 2.023(9) Å; N=C,
1.346(11) and 1.359(11) Å; N—H, 0.91(2) Å; the posi-
tion of the hydrogen atom was located from the Fourier
synthesis and refined), have the quinoid structure (N=C
1.336(11) and 1.396(12) Å). As a result, the platinum
atom is formally reduced to platinum(I) by adding the
CO group (Pt—C, 1.884(9) Å; C—O, 1.148(15) Å; and
the Pt—C—O angle is 175.3(11)o), the planar-square
ligand environment being retained, whereas the rhenium
atom bearing the halide ligand (Re—Cl, 2.344(2) Å) is
oxidized to rhenium(II) and has a distorted octahedral
environment.
Therefore, isolation of heterometallic complex 7 sug-
gests that heteronuclear derivatives can be formed as
intermediates in the reactions of î-semiquinonediimine
complexes of nickel and platinum with various metal-
containing fragments.
(50%). Found (%): C, 32.2; H, 2.5; N, 7.5. C14H12Cl2N3O3Re.
–1
Calculated (%): C, 31.89; H, 2.29; N, 7.97. IR (KBr), ν/cm
:
3722 w, 3364 m, 3191 w, 3142 w, 3031 w, 2108 s, 2044 s, 1778 s,
1721 m, 1716 w, 1684 w, 1662 m, 1596 w, 1556 m, 1540 s,
1520 w, 1504 w, 1164 w, 1084 s, 1050 m, 1015 m, 716 m, 744 s,
692 m, 630 w, 500 w.
Experimental
Synthesis of bis(N-phenyl-î-phenylenediami-
ne)nitrosylcarbonyl-cis-dichlororhenium(I), Re[η1-
(NH2)(NHPh)C6H4]2(CO)(NO)Cl2 (6). A solution of complex
5 (0.22 g, 0.42 mmol) in toluene (60 mL) was refluxed for 5 h.
The reaction mixture was concentrated to 20 mL under a stream
of argon and then slowly cooled on an oil bath to ∼20 °C. The
yellow crystals that precipitated were separated from the solu-
tion by decantation, washed with hexane, and dried at 20 °C
(0.1 Torr). Complex 6 was obtained in a yield of 0.13 g (45%).
The complexes were synthesized under an inert atmosphere
(Ar) with the use of anhydrous solvents.3 The starting com-
plexes M[î-(NH)(NPh)C6H4]2 (M = Ni (1) or Pt (2)),
[Re(CO)2(NO)Cl2]2, and Re(CO)2(NO)Cl2(thf) were prepared
according to known procedures.4,5,6 The reagents Fe(CO)5,
Re(CO)5Cl, and AgO3SCF3 were purchased from Fluka. Col-
umn chromatography was carried out with the use of Kiesilgel
60 (Fluka). The IR spectra were recorded on a Specord M80
instrument in KBr pellets.
Found (%): C, 42.2; H, 3.8; N, 9.5. C25H24Cl2N5O2Re. Calcu-
–1
lated (%): C, 43.92; H, 3.54; N, 10.24. IR (KBr), ν/cm
:
Reactions of the M[î-(NH)(NPh)C6H4]2 complexes with
Fe(CO)5 (M = Ni or Pt). A mixture of a solution of
Pt[î-(NH)(NPh)C6H4]2 (2) (0.92 g, 0.164 mmol) in benzene
(30 mL) and Fe(CO)5 (0.2 mL, 1.49 mmol) was irradiated with
UV light (a PRK-4 lamp) for 6 h. The resulting bright-red
solution was filtered from a black precipitate of metallic plati-
num and concentrated to dryness at 20 °C (0.1 Torr). Then
hexane (5 mL) was added to the solid precipitate, the resulting
suspension was applied to a column (5 ½ 25 cm) with SiO2, and
the red zone was eluted with a 1 : 1 benzene—hexane mixture
(50 mL; Rf 0.70). The solution was concentrated to 15 mL at
20 °C (0.1 Torr) and kept at 5 °C for one day. The dark-red
crystals that precipitated were separated from the solution by
decantation, washed with cold hexane, and dried in vacuo.
Complex 3 was obtained in a yield of 0.152 g (40%). Found
(%): C, 46.2; H, 1.9; N, 5.9. C18H10Fe2N2O6. Calculated (%):
C, 46.80; H, 2.18; N, 6.06. IR (KBr), ν/cm–1: 3800 w, 3736 w,
3648 w, 3481 w, 3430 w, 2920 m, 2856 m, 2368 w, 2344 w,
2320 w, 2176 w, 1976 w, 1888 w, 1824 w, 1760 w, 1688 w,
1608 s, 1520 s, 1488 s, 1443 w, 1384 m, 1352 w, 1288 s, 1240 s,
1160 m, 1071 w, 1024 m, 952 w, 912 m, 816 m, 760 m, 720 w,
680 m, 632 s, 608 w, 552 m, 512 m, 472 w, 424 w.
3744 w, 3360 m, 3200 w, 3136 w, 2928 w, 2864 w, 2840 w,
2352 m, 2320 w, 2176 w, 2112 m, 2040 m, 1992 s, 1784 m,
1744 s, 1600 s, 1512 m, 1496 s, 1464 m, 1424 w, 1336 m,
1296 m, 1256 w, 1168 s, 1088 w, 1032 w, 888 w, 744 s,
696 s, 488 m.
Synthesis of bis[µ-N´,N´-η2-(N-phenyl-î-benzoquino-
neiminoimide)]carbonylplatinum(I)-η2-(N-phenyl-î-ben-
zoquinonediimine)chlororhenium(II), (OC)Pt[µ-N,N-î-
(N)(NPh)C6H4]2ReCl[(NH)(NPh)C6H4] (7). A solution of
CF3SO3Ag (0.25 g, 1 mmol) in m-xylene (10 mL) was added to
a solution of Re(CO)5Cl (0.36 g, 1 mmol) in m-xylene (10 mL).
The reaction mixture was stirred for 0.5 h until a precipitate
formed. A solution of complex 2 (0.55 g, 1 mmol) in m-xylene
(10 mL) was added to the resulting suspension and the reaction
mixture was irradiated with UV light at 80 °C for 3 h. The
solution was concentrated to dryness at 70 °C (0.1 Torr),
hexane (5 mL) was added to the residue, and the resulting
suspension was applied to a column (5 ½ 30 cm) with SiO2. The
dark-brown zone was eluted with benzene (50 mL; Rf 0.60).
The solution thus obtained was concentrated to 10 mL at 70 °C
(0.1 Torr) and kept at ∼20 °C for one day. The dark-brown
crystals that precipitated were separated from the solution by
decantation, washed with hexane, and dried in air. Complex 7
was obtained in a yield of 0.28 g (28%). Found (%): C, 45.2;
H, 3.3; N, 8.3. C37H28ClN6OPtRe. Calculated (%): C, 44.91;
H, 2.85; N, 8.49. IR (KBr), ν/cm–1: 3728 w, 3480 m, 3408 m,
2920 s, 2858 m, 2032 w, 1952 w, 1912 w, 1704 w, 1656 w,
1624 w, 1568 w, 1464 m, 1384 w, 1256 s, 1096 s, 1032 s, 872 w,
808 s, 616 w, 464 w.
The reaction with the use of Ni[î-(NH)(NPh)C6H4]2 (1) as
the staring complex performed analogously afforded complex 3
in 20% yield. In the reaction, volatile nickel tetracarbonyl was
detected by IR spectroscopy (ν/cm–1: 2045).
Reaction of the Pt[î-(NH)(NPh)C6H4]2 complex with
Re(CO)2(NO)Cl2(thf). A solution of Re(CO)2(NO)Cl2(thf)
(0.18 g, 0.43 mmol) in anhydrous toluene (10 mL) was added to

146
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 1, January, 2001
Reshetnikov et al.
Table 1. Crystallographic parameters and details of refinement
of complexes 4—7
the structures of 4 and 5, absorption corrections were applied.7
The positions of the hydrogen atoms of the phenyl rings were
calculated geometrically and refined using the riding model.
The hydrogen atoms of the NH and NH2 fragments were
located from difference Fourier syntheses and refined isotro-
pically. All calculations were carried out with the use of the
SHELX97 program package.8 The complete tables of the atomic
coordinates, thermal parameters, bond lengths, and bond angles
were deposited with the Cambridge Structural Database.
Parameter
4
5
6
7
–
–
–
Space group
a/Å
P21/c
8.628(5)
P1
P1
P1
9.582(6)
10.287(2) 11.290(3)
b/Å
30.036(15) 10.262(5) 11.378(2) 12.191(3)
c/Å
9.579(5)
11.648(6) 11.717(2) 14.627(4)
α/deg
β/deg
γ/deg
V/Å3
Z
65.99(4)
77.26(4)
82.71(4)
111.23(3)
91.64(3)
107.59(3)
83.98(2)
73.69(2)
82.67(2)
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 99-03-
33091), the Ministry of Science and Technical Policy
(Grant 9.03.05), and INTAS (Grant 97 30344).
101.69(2)
2431(2)
4
1.786
5.246
2—50
1019.5(9) 1203.8(4) 1911.3(10)
2
2
2
–3
dcalc/g cm
1.839
6.242
1.886
5.304
1.855
6.932
3—52
–1
µ/cm
References
θ-2θ scanning
range/deg
Number of
independent
reflections
Number of
reflections
with I > 2σ
R1
3.9—56.1 3.8—60.1
1. P. E. Baike and O. S. Mills, Inorg. Chim. Acta, 1967, 6, 55.
2. I. L. Eremenko, S. E. Nefedov, A. A. Sidorov, M. O. Ponina,
P. V. Danilov, T. A. Stromnova, I. P. Stolarov, S. B. Katser,
S. T. Orlova, M. N. Vargavtik, I. I. Moiseev, and Yu. A.
Ustynyuk, J. Organomet. Chem., 1998, 551, 171.
3. Preparativnaya organicheskaya khimiya [Preparative Organic
Chemistry], Ed. N. S. Vol'fson, Goskhimizdat, Moscow, 1959,
156—162 (in Russian).
4314
2608
4962
3944
6757
3644
7550
2438
0.053
0.068
0.086
0.207
0.055
0.098
0.031
0.052
wR2
4. A. A. Sidorov, P. V. Danilov, S. E. Nefedov, M. A.
Golubnichaya, I. G. Fomina, O. G. Ellert, V. M. Novotortsev,
and I. L. Eremenko, Zh. Neorg. Khim., 1998, 43, 930 [Russ.
J. Inorg. Chem., 1998, 43 (Engl. Transl.)].
5. H.-U. Hund, U. Ruppli, and H. Berke, Helv. Chim. Acta,
1993, 76, 963.
6. D. Veghini, S. E. Nefedov, H. Schmalle, and H. Berke,
J. Organomet. Chem., 1996, 526, 117.
7. N. Walker and D. Stuart, Acta Crystallogr., 1983, A39, 158.
8. Sheldrick, SHELXS97. Program for the Solution of Crystal
Structures, Göttingen University, Göttingen, Germany, 1997.
X-ray diffraction study. The X-ray diffraction data sets were
collected according to a standard procedure on a four-circle
automated Siemens R3v/m diffractometer (λMo-Kα radiation,
λ = 0.71074 Å, T = 22 °C) for complexes 4, 5, and 7 and on a
Bruker AXS SMART 1000 diffractometer equipped with a CCD
detector (graphite monochromator, T = 110 °C, ω scanning
technique, scan step was 0.3°, frames were exposed for 30 s) for
complex 6. The crystallographic parameters and details of the
refinement of all structures are given in Table 1.
The structures of all complexes were solved by direct meth-
ods and refined by the full-matrix least-squares method with
anisotropic thermal parameters for all nonhydrogen atoms. For
Received October 16, 2000;
in revised form November 10, 2000