Synthesis and structure of inorganic and organometallic N, N′-bis(3, 5-di-tert-butylsalicylidene)ethylenediamine yttrium complexes

Article abstract of DOI:10.1016/S0277-5387(02)01031-8

The utility of the chloride precursor [(salen′)Y(μ-Cl)(THF)]₂, 1 (salen′ = N,N′-bis(3,5-di-tert-butylsalicylidene)ethylenediamine), in preparing amide, aryloxide, and organometallic derivatives of this ancillary ligand system is described. 1 re

Full text of DOI:10.1016/S0277-5387(02)01031-8

Polyhedron 21 (2002) 1683ꢁ1688
/
www.elsevier.com/locate/poly
Synthesis and structure of inorganic and organometallic N,N?-
bis(3, 5-di-tert-butylsalicylidene)ethylenediamine yttrium complexes
William J. Evans, Cy H. Fujimoto, Joseph W. Ziller
Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
Received 9 October 2001; accepted 30 April 2002
Abstract
The utility of the chloride precursor [(salen?)Y(m-Cl)(THF)]2, 1 (salen?ꢀ
in preparing amide, aryloxide, and organometallic derivatives of this ancillary ligand system is described. 1 reacts with KN(SiMe3)2
to form (salen?)Y[N(SiMe3)2](THF), 2, but does not readily form an aryloxide derivative by reaction with LiOAr? (OAr?ꢀ2,6-di-
tert-butylphenoxide). However, (salen?)Y(OAr?), 3, can be obtained by reaction of Y(OAr?)3 with H2salen? and crystallizes from
tolueneꢁTHF as (salen?)Y(OAr?)(THF), 4. 4 can also be prepared by reaction of 2 with HOAr? in THF. The hexafluoroacetyl-
/
N,N?-bis(3,5-di-tert-butylsalicylidene)ethylenediamine),
/
/
acetonate (hfac) complex, (salen?)Y(hfac)(THF)2, 5, and the organometallic derivative, (salen?)Y(C5Me5), 6, can be prepared by
reaction of 1 with Na(hfac) and KC5Me5, respectively. # 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Yttrium; Salen; Amide; Aryloxide; Organometallic
1. Introduction
we explore the synthetic utility of 1 as a precursor to the
several types of derivatives commonly explored when
characterizing any new ancillary ligand system, e.g. an
amide N(SiMe3)2, an aryloxide OC6Ht3Bu2-2,6, and a
cyclopentadienyl derivative. Structural details and che-
mical reactivity of these new complexes are discussed
and compared with the data in the literature on (salen?)-
Y[N(SiMe2H)2](THF) and (salen?)Y(OC6Ht3Bu2-2,6)-
(THF), whose preparation depended critically upon
Y[N(SiMe2H)2]3 [7].
Efforts to diversify the ancillary ligands useful in
lanthanide and yttrium chemistry beyond the commonly
used cyclopentadienyl complexes have led to the ex-
ploration of a variety of polyhapto oxygen and/or
nitrogen donor atom alternatives. Examples include
benzamidinates [1], 4,13-diaza-18-crown-6 (DAC) [2],
porphyrins [3], and calix-pyrroles [4]. Schiff base ligands
are attractive in this regard due their stability and the
ease by which modified variations can be obtained: this
class of ligands is flexible in terms of both size and
2. Results and discussion
charge. To date, however, the number of structural [5ꢁ
/
12] and catalytic [12,13] investigations of lanthanide
Schiff base complexes in the literature is small compared
with that for other ligand systems.
Recently, we reported synthetic and structural infor-
mation on two non-aqueous yttrium Schiff base com-
plexes utilizing N,N?-bis(3,5-di-tert-butylsalicylidene)-
ethylenediamine) (salen?), namely [(salen?)Y(m-Cl)-
(THF)]2, 1, and Y(salen?)2K(THF)2 [14]. In this study,
2.1. Synthesis of (salen?)Y[N(SiMe3)2](THF), 2
Complex 1 was initially examined as a precursor to
the amido complex, (salen?)Y[N(SiMe3)2](THF) since
the analogous (salen?)Y[N(SiMe2H)2](THF) had been
reported in the literature and crystallographically char-
acterized [7]. Reaction of 1 and KN(SiMe3)2 in toluene
produces a dark orange alkane soluble solid in good
1
yield as shown in Scheme 1. Both the H NMR and IR
spectra of
Y[N(SiMe2H)2](THF), including a strong IR peak at
2 were similar to those of (salen?)-
* Corresponding author. Tel.: ꢃ
2210
E-mail address: wevans@uci.edu (W.J. Evans).
/
1-949-824-5174; fax: ꢃ1-949-824-
/
1617 cmꢂ1 appropriate for the imine functionality in
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 3 1 - 8

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W.J. Evans et al. / Polyhedron 21 (2002) 1683ꢁ
/1688
Scheme 1.
salen?. Complexometric analysis was consistent with the
formula (salen?)Y[N(SiMe3)2](THF), 2.
2.2. Synthesis of [(salen?)Y(OC6Ht3Bu2-2,6)], 3, and
[(salen?)Y(OC6Ht3Bu2-2,6)] (THF), 4
The synthesis of an aryloxide complex from 1 was
subsequently attempted since it had been reported
previously that (salen?)Y(OC6Ht3Bu2-2,6)](THF) could
be made [7]. Ionic metathesis of 1 with LiOAr? (OAr?ꢀ
/
1
OC6Ht3Bu2-2,6) did not produce a pure aryloxide by H
1
NMR spectroscopy. Instead, the H NMR spectrum of
the product was complicated and suggested that multi-
ple products had formed.
Fig. 1. Thermal ellipsoid plot of [(salen?)Y(OC6H3But2-2,6)(THF)], 4,
drawn at the 50% probability level with hydrogen atoms omitted for
clarity.
However, reaction of Y(OAr?)3 [15] and H2salen? in
hexanes precipitated a yellow solid that had a simple
NMR spectrum consistent with (salen?)Y(OAr?), 3.
Complex 3 displayed high solubility in coordinating
solvents, such as THF, and was moderately soluble in
benzene and toluene, but had only limited solubility in
alkanes. Attempts to crystallize 3 in a non-coordinating
medium were unsuccessful. However, when 3 is concen-
The yellow product had a 1H NMR spectrum consistent
with the formula (salen?)Y(hfac)(THF)2, 5, and the IR
spectrum contained two strong absorbances at 1660 and
?
1613 cmꢂ1 attributable to [CÄ
/
O]hfac and [CÄ
/
N]salen. X-
ray diffraction confirmed the identity of this product as
(salen?)Y(hfac)(THF)2, 5, Fig. 2.
trated in a 50/50 mixture of tolueneꢁ/THF and cooled to
ꢂ
/
35 8C, yellow crystals are obtained which were
analyzed by X-ray crystallography and determined to
be the THF adduct (salen?)Y(OAr?)(THF), 4 (Scheme 2,
Fig. 1). As expected [7], 2 could be transformed
quantitatively to 4 by reaction with HOAr? in THF,
Scheme 3.
2.4. Synthesis of organoyttrium salen? complexes
In attempt to isolate an organometallic complex of
the salen? yitrium system, the reaction of 1 and KC5Me5
was examined. (salen?)Y(C5Me5), 6 could be isolated in
good yields (Scheme 5) and was fully characterized by
NMR, IR and X-ray diffraction (Fig. 3). In contrast,
2.3. Synthesis of (salen?)Y(hfac)(THF)2, 5
when 1 reacts with simple lithium alkyls, LiR (Rꢀ
/
Me,
Although 3 was not easily synthesized by ionic
metathesis, this synthetic approach did succeed with
the chelating oxygen donor ligand hexafluoroacetylace-
tonate (hfac). 1 reacts with Na(hfac) to form a yellow
solution and a white precipitate according to Scheme 4.
CH2SiMe3, CH(SiMe3)2), in toluene at ꢂ78 8C, a
/
mixture is indicated by the complicated 1H NMR
spectrum. These mixtures could result from attack of
the alkyl on the imine portion of the salen? ligand as has
been reported to occur in Group IV systems [16,17]. The
susceptibility of the imine bonds to nucleophilic attack
could be further enhanced by coordination to the highly
electropositive metal.
2.5. Structural comparison of yttriumꢁsalen? complexes
/
The YÃ
/
O(salen?) distances in 4, 5, and 6 range from
˚
2.141(2) to 2.240(2) A while the YÃ
/
N(salen?) interac-
˚
tions range from 2.392(3) to 2.559(3) A (Table 1). These
Scheme 2.

W.J. Evans et al. / Polyhedron 21 (2002) 1683ꢁ
/1688
1685
Scheme 3.
These comparisons suggest that salen? can provide
coordination equivalent to that of (C5Me5)(OC6Ht3Bu2-
2,6), (hfac)(triglyme), or (C5Me5)Cl(THF).
3. Conclusion
These studies have shown that the readily obtainable
chloride, [(salen?)Y(m-Cl)(THF)]2 and ionic metathesis
reactions are synthetically useful in making yttrium
complexes ligated by salen?. Reactions of 1 with
KN(SiMe3)2, Na(hfac), and KC5Me5 all form the
corresponding products in high yields. Although the
chemistry of salen? as an ancillary ligand is promising, it
contains a reactive imine functional group that is prone
to nucleophilic attack. This can interfere with the
isolation of complexes of reactive alkyl and hydride
groups.
Fig. 2. Thermal ellipsoid plot of (salen?)Y(hfac)(THF)2, 5, drawn at
the 50% probability level with hydrogen atoms omitted for clarity.
distances are consistent with LnÃ
distances in other reported Schiff base complexes when
metal sizes are taken in consideration [20] (LnÃO and
LnÃN): [(salen?)Y(m-Cl)(THF)]2 [14], 2.143(2) and
/
O and LnÃN salen?
/
/
/
˚
2.492(3) A; (salen?)Y[N(SiMe2H)2](THF) [7], 2.16 and
4. Experimental
˚
2.27 A; [(N-(2,4,6-trimethylphenyl)salicylideneimi-
˚
ne)2La(m-Cl)(THF)] [10], 2.295(11) and 2.659(16) A;
The chemistry described below was performed under
nitrogen with rigorous exclusion of air and water by
Schlenk, vacuum line, and glovebox techniques. Sol-
vents were purified by distillation over sodium or
potassium benzophenone ketyl. KN(SiMe3)2 was pur-
chased from Aldrich and used as received. [(salen?)Y(m-
Cl)(THF)]2 [14] and Y[(OC6H3But2-2,6)2]3 [15] were
prepared by literature methods. NMR spectra were
recorded using a Bruker DRX400 or a General Electric
GE500 spectrometer. Infrared spectra were recorded on
a ReactIR1000 system (Applied System Inc.) as thin
films in toluene. X-ray crystallographic data were
obtained on a Bruker CCD platform diffractometer.
Complexometeric analyses were obtained as previously
described [21].
[(trans-(9)-N,N?-bis(salicylidene)-1,2-cyclohexanedia-
mine)Sm(C5H5)]2(m-THF)(THF)2 [9], 2.30(6) and
2.56(5) A.
/
˚
The salen? moieties in complexes 4ꢁ
/
6 adopt bent
geometries about the yitrium metal center as measured
by the dihedral angle between the two phenyl rings. The
aryloxide, 4, which has the largest deviation from
planarity, 60.28, is followed by the pentamethylcyclo-
pentadienyl, complex 6, with a 448 angle, and the hfac
complex, 5, with a 178 angle. These angles show that the
salen? ethylene backbone is flexible and is able to adopt
a preferred orientation with respect to the steric bulk of
the second ligand in the complex, i.e. the alkoxide, hfac,
or cyclopentadienyl group.
˚
The 2.128(2) A YÃ
/
O(OAr?) distance in 4, the 2.383(2)
O(hfac) distances in 5, and the 2.372
A Y-(C5Me5 ring centroid) length in 6 are similar to
˚
and 2.404(2) A YÃ
/
4.1. (Salen?)Y[N(SiMe3)2](THF), 2
˚
analogous bond lengths in other yttrium complexes
˚
In a glovebox KN(SiMe3)2 (52 mg, 0.26 mmol) was
added to a slurry of 1 (180 mg, 0.26 mmol) in 5 ml of
containing these groups: e.g. 2.096(4) A, YÃO(OAr?) in
/
(C5Me5)Y(OC6Ht3Bu2-2,6)2 [18]; 2.283(7) and 2.322(6)
˚
toluene. After stirring for 12 h, the dark orangeꢁ
slurry was centrifuged to remove KCl. The solvent was
removed by rotary evaporation and the dark orangeꢁ
/
red
A, YÃ
/
O(hfac) in [(triglyme)Y(hfac)2]ꢃ [19]; and 2.381
A, Y-(C5Me5 ring centroid) in (C5Me5)2YCl(THF) [20].
˚
/
Scheme 4.

1686
W.J. Evans et al. / Polyhedron 21 (2002) 1683ꢁ1688
/
Scheme 5.
centrifuged to separate a yellow solid and light yellow
solution. The yellow solid was isolated and dried by
rotary evaporation (151 mg, 85%). X-ray quality crystals
were grown from a 50/50 mixture of tolueneꢁ
/
THF at ꢂ
/
35 8C. Anal. Calc. for C50H75N2O4Y: Y, 10.4. Found:
1
Y, 9.9%. H NMR (C6D6): d 7.73 (d, 2H, Jꢀ
7.65 (s, 2H), 7.31 (d, 2H, Jꢀ7.7 Hz), 7.06 (d, 2H, Jꢀ
2.4 Hz), 6.82 (t, 1H, Jꢀ7.7 Hz), 3.73 (q, 2H, Jꢀ6.5
Hz), 2.76 (q, 2H, Jꢀ6.5 Hz), 1.69 (s, 18H), 1.46 (s,
/
2.4 Hz),
/
/
/
/
/
18H), 1.36 (s, 18H). 13C{1H} NMR (C6D6): d 170.9,
164.1, 139.8, 138.0, 137.8, 130.6, 129.6, 129.3, 124.9,
122.7, 116.7, 58.2, 35.7, 34.7, 34.1, 31.7, 30.6, 30.1. IR
2958vs, 2912s, 2873s, 1614vs, 1537s, 1437m, 1321m,
Fig. 3. Thermal ellipsoid plot of (salen?)Y(C5Me5), 6, drawn at the
50% probability level with hydrogen atoms omitted for clarity.
1259a, 1205w, 1166m, 1097w, 1027w, 841w, 803w cmꢂ1
.
Table 1
Selected bond lengths for [(salen?)Y(m-Cl)(THF)]2, 1; (salen?)-
Y(OAr?)(THF), 4; (salen?)Y(hfac)(THF)2, 5; (salen?)Y(C5Me5), 6
4.3. (Salen?)Y(hfac)(THF)2, 5
Complex
YÃO(salen?)
YÃN(salen?)
YÃO(THF)
Na(hfac) (51 mg, 0.22 mmol) was added to a yellow
slurry of 1 (152 mg, 0.22 mmol) in 5 ml of THF. After
stirring for 12 h, the yellow slurry was centrifuged and
the solvent was removed from the yellow solution under
vacuum (169 mg, 82%). X-ray quality crystals were
grown from a toluene solution at room temperature
(r.t.). Anal. Calc. for C45H63N2O6F6Y: Y, 9.6. Found:
1
2.143(2)
2.143(2)
2.165(2)
2.179(2)
2.205(2)
2.240(2)
2.141(2)
2.148(2)
2.492(3)
2.418(3)
2.430(3)
2.483(3)
2.511(3)
2.559(3)
2.392(3)
2.418(3)
2.463(3)
4
5
6
2.457(2)
2.379(2)
2.425(2)
1
Y, 9.4%. H NMR (C6D6): d 7.91 (s, 2H), 7.70 (d, 2H,
Jꢀ
(b, 8H, Dn1/2
(s, 18H), 1.14 (b, 8H, Dn1/2
/
2.6 Hz), 7.11 (d, 2H, Jꢀ
116 Hz), 3.28 (s, 4H), 1.64 (s, 18H), 1.37
124 Hz). 13C{1H} NMR
/
2.6 Hz), 6.48 (s, 1H), 3.40
ꢀ
/
ꢀ
/
red oil was stirred for 15 min in hexanes. Removal of
solvent by rotary evaporation gave a dark orange
powder (155 mg, 72%). Anal. Calc. for C42H72N3O3-
(C6D6): d 168.6, 165.0, 140.5, 135.7, 129.7, 129.1, 120.8,
91.9, 69.4, 63.3, 35.5, 34.0, 31.8, 29.9, 25.2. IR 2957vs,
2914s, 2868s, 1660vs, 1613s, 1552w, 1498m, 1463w,
1440m, 1413m, 1393w, 1363w, 1339m, 1332s, 1254s,
1
Si2Y: Y, 10.9. Found: Y, 11.2%. H NMR (C6D6): d
1200s, 1146s, 1100s, 1023s, 911w, 872w cmꢂ1
.
7.73 (s, 2H), 7.69 (d, 2H, Jꢀ
2.5 Hz), 4.39 (q, 2H, Jꢀ6.0 Hz), 4.10 (b, 4H, Dn1/2
125 Hz), 2.82 (q, 2H, Jꢀ6.0 Hz), 1.63 (s, 18H), 1.50 (b,
120 Hz), 1.36 (s, 18H), 0.26 (s, 18H).
/
2.5 Hz), 7.03 (d, 2H, Jꢀ
/
/
ꢀ
/
/
4.4. (Salen?)Y(C5Me5), 6
4H, Dn1/2
ꢀ
/
13C{1H} NMR: d (C6D6) 170.6, 164.4, 139.2, 136.8,
130.0, 129.7, 122.6, 70.2, 59.0, 35.7, 34.1, 31.7, 30.3,
25.4, 5.3. IR 2957vs, 2907s, 2868s, 1617vs, 1536s, 1463s,
1440s, 1413s, 1390s, 1274w, 1235w, 1200w, 1166s,
KC5Me5 (33 mg, 0.19 mmol) was added to 1 (133 mg,
0.19 mmol) in 5 ml of THF. The reaction was stirred for
12 h, the yellow slurry was centrifuged, and the solvent
was removed from the yellow solution by rotary
evaporation to give a yellow oil. Hexanes were added,
the mixture was stirred, and solvent was removed from
the oil by rotary evaporation to give a yellow solid (103
mg, 75%). X-ray quality crystals were grown from a 50/
1054w, 1027w, 980w, 837m cmꢂ1
.
4.2. (Salen?)Y(OC6H3But2-2,6)(THF)0,1, 3, 4
Addition of H2salen? (111 mg, 0.22 mmol) to a white
slurry of Y(OAr?)3 (159 mg, 0.22 mmol) in 5 ml of
hexanes immediately generated a yellow solution.
Within a few minutes, a yellow precipitate appeared.
The reaction was stirred overnight and the slurry was
50 tolueneꢁ
C46H80N3O4Si2Y: Y, 12.4. Found: Y, 11.6%. H NMR
(C6D6): d 7.71 (d, 2H, Jꢀ2.3 Hz), 7.70 (s, 2H), 7.07 (d,
2H, Jꢀ2.3 Hz), 3.60 (q, 2H, Jꢀ6.5 Hz), 2.68 (q, 2H,
Jꢀ6.5 Hz), 2.00 (s, 15H), 1.75 (s, 18H), 1.36 (s, 18H).
/
hexanes mixture at r.t. Anal. Calc. for
1
/
/
/
/

W.J. Evans et al. / Polyhedron 21 (2002) 1683ꢁ
/1688
1687
13C{1H} NMR (C6D6): d 169.9, 164.9, 140.2, 136.8,
130.0, 129.5, 122.4, 116.7, 58.3, 35.8, 34.1, 31.7, 30.3,
11.1. IR 2957vs, 2907s, 2868s, 1610vs, 1532s, 1463w,
1440m, 1413m, 1390m, 1359w, 1316s, 1274s, 1254s,
1200m, 1166s, 1096w, 1058w, 1027w, 984w, 930w,
4.6. (Salen?)Y(hfac)(THF)2, 5
A yellow crystal of approximate dimensions 0.17ꢄ
/
0.20ꢄ0.33 mm was mounted on a glass fiber and
/
transferred to a Bruker CCD platform diffractometer
(30 s per frame scan time for a hemisphere of diffraction
data). The diffraction symmetry was 2/m and the
systematic absences were consistent with the centrosym-
metric monoclinic space group P21/c which was later
determined to be correct.
911w, 876w, 849m cmꢂ1
.
4.5. X-ray data collection, structure determination, and
refinement for [(salen?)Y(OC6H3But2-2,6)(THF)], 4
Disorder was present in the CF3 group and both THF
molecules. Atoms F(4)Ã
/
F(5), C(38)Ã
/
C(40), C(43) and
A colorless crystal of approximate dimensions 0.16ꢄ
/
C(44) were disordered and included using multiple
components with partial site-occupancy factors. Hydro-
gen atoms were included using a riding model. At
0.19ꢄ0.25 mm was mounted on a glass fiber and
/
transferred to a Bruker CCD platform diffractometer.
The SMART [22] program package was used to determine
the unit-cell parameters and for data collection (30 s per
frame scan time for a sphere of diffraction data). The
raw frame data was processed using SAINT [23] and
SADABS [24] to yield the reflection data file. Subsequent
calculations were carried out using the SHELXTL [25]
program. The diffraction symmetry was 2/m and the
systematic absences were consistent with the centrosym-
metric monoclinic space group P21/n which was later
determined to be correct. Details are in Table 2.
convergence, wR2ꢀ
variables refined against 10 952 data. As a comparison
for refinement on F, R1ꢀ0.0576 for those 8653 data
with I ꢀ2.0s(I).
/
0.1533 and GOFꢀ1.032 for 518
/
/
/
4.7. (Salen?)Y(C5Me5), 6
A yellow crystal of approximate dimensions 0.10ꢄ
/
0.15ꢄ0.25 mm was mounted on a glass fiber and
/
The structure was solved by direct methods and
refined on F2 by full-matrix least-squares techniques.
The analytical scattering factors [26] for neutral atoms
were used throughout the analysis. There were 2.5
molecules of toluene solvent present per formula unit.
The half molecule of solvent was modeled as a disorder
over an inversion center. Hydrogen atoms were included
transferred to a Bruker CCD platform diffractometer
(30 s per frame scan time for a hemisphere of diffraction
data). The diffraction symmetry was mmm and the
systematic absences were consistent with the orthor-
hombic space group P212121 which was later determined
to be correct.
Hydrogen atoms were included using a riding model.
using a riding model. At convergence, wR2ꢀ
GOFꢀ0.0631 for 586 variables refined against 15 186
unique data. As a comparison for refinement on F,
R1ꢀ0.0631 for those 9780 data with I ꢀ2.0s(I).
/
0.1788 and
At convergence, wR2ꢀ
variables refined against 9633 data. As a comparison for
refinement on F, R1ꢀ0.0452 for those 6021 data with
I ꢀ2.0s(I). The absolute structure was assigned by
refinement of the Flack parameter [26].
/
0.0592 and GOFꢀ0.934 for 424
/
/
/
/
/
/
Subsequent complexes were handled as described for 4.
Table 2
X-ray crystallographic data on Y(salen?)(OC6H3Bu2t -2,6)(THF), 4, Y(salen?)hfac(THF)2, 5, (salen?)Y(C5Me5), 6
Compound
4
5
6
FW
C50H73N2O4Y×2.5(C7H8)
C45H63F6N2O6Y
158 (2)
C42H61N2O2Y
158 (2)
orthorhombic
P212121
10.4859(9)
15.7481(13)
24.370(2)
90
Temperature (K)
Crystal system
Space group
178 (2)
monoclinic
P21/n
monoclinic
P21/c
˚
a (A)
16.5331(7)
16.0380(6)
23.5698(9)
90
13.7169(6)
21.1351(10)
16.7430(7)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
V (A )
Z
rcalc (Mg mꢂ3
m (mmꢂ1
92.4660(10)
90
109.0750(10)
90
90
90
3
˚
6243.9(4)
4
1.157
4587.4(4)
4
1.348
4024.2(6)
4
1.180
)
)
0.980
0.0631
0.1788
1.343
0.0576
0.1533
1.484
0.0452
0.0592
Final R1[I ꢀ2s(I)]
Final wR2 (all data)

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W.J. Evans et al. / Polyhedron 21 (2002) 1683ꢁ1688
/
[8] Q. Liu, M. Ding, Y. Lin, Y. Xing, J. Organomet. Chem. 548
(1997) 139.
5. Supplementary material
[9] Q. Liu, M. Ding, Y. Lin, Y. Xing, Polyhedron 17 (1998) 2327.
[10] P. Blech, C. Floriani, A. Chiesi-Villa, C. Guastini, J. Chem. Soc.,
Dalton Trans. (1990) 3557.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Numbers CCDC 172137ꢁ
/
172139
[11] T. Dube, S. Gambarotta, G. Yap, Organometallics 17 (1998)
3967.
for compounds 4ꢁ6, respectively. Copies of this infor-
/
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Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: ꢃ44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http//www.ccdc.cam.ac.uk).
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Chemical Sciences of the Office of Basic Energy Sciences
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