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Triple-Decker Sandwich Complexes of 4d and 5d Metals with cyclo-Triphosphorus as 3-Ligand Structural and Magnetic Properties.

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tion of LiCo(CO), with C O ~ ( C O ) ,The
~ ~ ~molecular
~.
structure of LiCo3(CO),o.i-Pr,0 (1) has been solved by X-ray diffraction methods161. It consists of the ions [ C O ~ ( C O ) , ~and
]Li . The cations are approximately tetrahedrally surrounded
by one ether oxygen (1.9 10( 12l A) and by three carbonyl oxygens [one p 3 - C 0 , 1.859(10) A, and two p-CO, Li -0(2-3)
1.989(10), Li 0(1-3) 2.049(10) A] of three different cluster
units.
The three cobalt atoms form an almost regular triangle,
forming the base of a tetrahedron having the face-bridging
carbon, C( 1-2-3), at a n apex. The interatomic distances and
angles of the Co,C cluster are comparable with those found
in other cluster compounds of the oxymethylidyne type['].
The IR spectrum of (1) as Nujol mull shows strong absorptions around 1800 c m- ', in agreement with the presence of
edge-bridging carbonyl groups as established by the X-ray
structure analysis. This contrasts with the weak carbonyl absorption observed a t 1865 c m - ' in ether solution'']. These
observations can be rationalized in terms of small amounts of
clusters with edge-bridging carbonyl groups in solvent-dependent equilibria with clusters containing terminal carbonyl groups only. Addition of tetrahydrofuran (1-3 vol-%) to a
n-Bu20 solution of ( I ) , before decomposition takes
considerably decreases the intensity of the 1865 c m - ' band
and modifies the spectral pattern associated with the facebridging carbonyl group at about 1580 c m - ' , while the terminal carbonyl stretching region around 2000 cm - ' remains
essentially unchanged: under these conditions the acidity of
Li supposedly is decreased through coordination to the
more basic tetrahydrofuran. In the solid state the acidity of
Li+ is greatly enhanced, thus promoting the structural
change to the form containing the edge-bridging carbonyl
groups.
Our investigations show that dramatic structural changes
can occur in an anionic carbonyl cluster by apparently small
changes of the acid-base properties of the system.
+
+
Experimental
Analytically pure LiCo3(C0),,,-E t 2 0 (1.3 g) was dissolved
in diisopropyl ether (20 ml) and the resulting solution was
concentrated to about 5 mi under reduced pressure. On addition of n-hexane (100 ml) and filtration, the mother liquor
slowly yielded 0.5 g of LiCo3(CO)Io-i-Pr20
as black crystals.
All of the operations must be carried out under purified argon.
Received: October 15. 1979 [Z 462 IE]
German version: Angew. Chem. Y2, 441 (1980)
171 B. Stuue, V. Batre/. R. Boese, G. Schmrd, Chem. Ber. / I / , 1603 (1978); Y
Barrel. Z. Naturforsch. B 31, 342 (1976); V. Batre/, U. Muller. R. Allmunn. 1.
Organomet Chem. 102, 109 (1975). C Schmrd. V. Butrel. B. Srutte. /hid 113.
67 (1976): F Ktanberg. W . B. Asken. L. J . Guggenberger. Inorg. Chem 7.
2265 (1968).
Triple-Decker Sandwich Complexes of 4d and 5d
Metals with cyclo-Triphosphorus as p,q3-Ligand
Structural and Magnetic Properties
By CIaudio Bianchini, Massimo Di Vaira, Andrea Meli,
and Luigi Sacconil"
The recent synthesis of mononuclear and dinuclear 3d metal complexes containing the cyclo-triphosphorus (q3-P3)
group as a ligand"' prompted us to attempt the synthesis of
the corresponding compounds of the 4d and 5d metals. On
reaction of white phosphorus (P4) with [Rh(C,H,),Cl], ( I ) or
Ir(PPh,),(CO)Cl in the presence of 1,1,1-tris(diphenylphosphinomethy1)ethane (triphos) we obtained the mononuclear
complexes [(triphos)M(q3-P3)] with M = Rh (2) and M = Ir
(31, respectively[21.These compounds react with (1) and cobalt(n) or nickel(i1) tetrafluoborates in the presence of triphos (and, where appropriate, of NaBPh,) yielding the dinuclear compounds
[(triph~s)Rh-~-(q~-P,)Co(triphos)](BPh,)~~
2 (CH3),C0 (4)
I(triph~s)Rh-p-(q~-P,)Ni(triphos)](BF~)~
.C4H,0 (5)
[(triph0s)Ir-p-(q~-P3)Co(triphos)](BF,)~~CH~Cl~
(6)
[(triphos)Rh-p-(q'-P,)Rh(triphos)]BPh4. (CH,),CO (7)
whose cations have a triple-decker sandwich structure with
cyclo-triphosphorus acting as central bridge-forming lrihapto
lzgand. The salts (41,(5) and (6) behave as 1 :2 electrolytes,
whereas (7) is a 1:1 electrolyte. They are all air-stable in the
solid state, but rather unstable in solution. Compounds (4)
and (6) are paramagnetic with a magnetic moment corresponding to a doublet ground state. Compound (7) is essentially diamagnetic at room temperature, whereas (S) has a
magnetic moment slightly dependent on the nature of the
counterion and of the solvent in the lattice, decreasing from
values of 1.3-1.6 F~ at room temperature to ca. 0.7 p+ at
100 K. The magnetic behavior of (5) and (7) differs considerably from that of the previously described complexes with 32
valence electrons, which have a magnetic moment corresponding to two unpaired electrons"]. This difference in the
magnetic properties may be traced to structural differences
between the compounds[31:the -q3-P3bridge in {5) is shifted
from the line joining the two metal atoms (cf. Fig. 1) in such
CAS Registry numbers.
( / I . 73612-21-2: LiCo,(CO),,,. 26748-45-3
P
[I[
121
[3J
[4]
151
16)
W F Edge//. J. Lyford. R Barberfa. C. 1. Jose. J . Am. Chem. SOC.93, 6403
(197 1 ); W. f . Edge//,J. Lyford, ibid. 93.64 (1971 ); M. Y. Darensbourg. D. J.
Darensbourg. D. Burns, D. A. Drew, rbid. 98, 3127 (1976).
G fuchinettr. C. Floriani. P f . Zanarzi. A. R. Zanzari. Inorg. Chem. 17. 3002
(lY78): H B Chin, R. Bau, J . Am. Chem. SOC.98, 2434 (1976)
a) J. P. Collman, R. G. frnke, J N . Cawse. J I . Brauman, J. Am. Chem. SOC.
99. 2515 (1977). b) M. Darensbourg. H . Burros, C. Borman. rbid. 99. 1647
(1977).
E. L. Muetterries. T. N Rhodm. E. Band. C. F. Bricker, W. R. Prelzer. Chem.
Rev. 7Y. 91 (1979); P Chin;. 6.Longoni, V. G. Albano. Adv. Organomet.
Chem 14. 98 (1976).
G. fachinetti. J. Chem. Soc Chem. Commun. 1979. 396.
Monoclinic. P2,/c. u = 1 I 322(2). b = 11.943(3). c = 16.557(2)
p=
91 72(1)'. 2 = 4 . P ~ . , ~ &
1.68
= g/cm'. single crystal diffrdctometer CAD 4.
Mo,,, (graphite monochromator); data collection up to 2 8 = 50" (half sphere,
851 1 reflections). merging about equivalent reflections gives 3026 independent observed ones. 15 reflections suppressed because of asymmetric background. program for crystal structure determination: SHELX-76, refinement
to R=0.0758 (R,=0.0487, w=O.O58/[~r'(F)+0002 PI) for the observed reflections.
Angew. Chem. In!. Ed. Engl. 19 (19801 No. 5
A.
Fig. I . Structure of the dicdtion of (5). Bond lengths in the q'-P, ligand of the lriple-decker complex: P7 P8=2.31, P7,8 P9=2.15 A. Each metal site. M. has
50% Rh and 50% Ni (or 50% Co, in compound (41) occupancy.---Bond lengths in
complex
(4): M P,,=221-2.22
( n = 1-6).
2.29 -2.32
( n = 7 - 9);
Pn P,,=2.19-220(n=7.
8; m = 8 . 9)
[*] Prof. Dr. L. Sacconi. Dr C . Bianchini, Dr. M. Di Vaira, Dr. A. Me11
Istituto di Chimica Generale e Inorganica dell'Universita.
Laboratorio CNR.
Via J. Nardi 39, 1.50132 Firenze (Italy)
0 Verlag Chemre, GmbH. 6940 Weinherm. I980 0570-OX33/X~/05OS-405
$ 02.50/0
405
a way that the approximate C, symmetry existing in the
structure of (4) as well as in those of all the analogous complexes previously investigated"' is lost. As a consequence of
this distortion the degeneracy of the highest-occupied 6e orbitall" is lifted and a spin singlet, rather than triplet, ground
state is attained. The residual paramagnetism of compound
(5) may include a temperature independent (TIP) contribution but there may also be a contribution from partial occupation of the higher triplet state.
Procedure
Synthesis of (4): A solution of (2) (410 mg, 0.50 mmol) in
40 ml of CH2C12was added under nitrogen at room temperature to a mixture of C O ( B F , ) ~ . ~ H(170
~ O mg, 0.50 mmol) rn
15 ml of ethanol and of the triphos ligand (320 mg, 0.50
mmol) in 20 ml of CH2C12.A solution of NaBPh, (350 mg, 1
mmol) in 10 ml of ethanol was then added. After concentration of the resulting solution brown crystals were obtained,
which were recrystallized from acetone/ethanol. Yield 80%.
(5): A solution of (2) (410 mg, 0.50 mmol) in 80 ml of T H F
was added under nitrogen at room temperature to a mixture
of Ni(BF4)2.6H20(170 mg, 0.50 mmol) in 30 ml of ethanol
and of the triphos Iigand (320 mg, 0.50 mmol) in 10 mi of
THF. The resulting mixture was concentrated to 40 ml under
vacuum. After standing overnight dark red crystals had separated. Yield 60%.
(6): Prepared by the same procedure as (4) except for substitution of compound (3) (450 mg, 0.50 mmol) for (2). The
reddish brown crystals were recrystallized from dichloromethane/ethanol. Yield 80%.
(7): Prepared by the same procedure as (4) except for substitution of (1) or [Rh(CO),C1I2 (0.30 mmol) for the cobalt
salt; triphos (0.60 mmol), NaBPh, (0.50 mmol) in 30 ml of
ethanol. Orange-red crystals; yield 70%.
Received: November 20. 1979 [Z 463 IE]
German version. Angew. Chem. Y2. 412 (19.30)
The experiments were performed in a thermostated column of 60 cm length and 1.2 cm i.d. packed with 19 g of exchanger resin ("[2,.2.2] polymer", E. Merck). In each run 40
mg of calcium of natural isotopic composition was applied to
the column as CaCI, dissolved in 1 ml of CH30H/CHCl3/
H 2 0 (70:30 v/v + 1.65 vol% H 2 0 ) and eluted at -21, 0,
and 20 " C with this solvent system (ca. 0.5 ml/min). The calcium content of the eluate fractions was determined by flame
atomic absorption spectrometry and the 44Ca/4"Ca and the
4xCa/40Caisotope ratio determined by thermionic mass spectr~metry[~l.
In the case of the isotope exchange reaction between
4XCa2 4 and 40Ca2 +
we find (L = solution; R = resin monomer
unit):
R [2B.2.2,4XCa]'*+ '''Ca:'
s R
[28.2.2,4"Ca]2+
+ 4XCa:+
(1)
The equilibrium constant K , corresponds to the elementary
separation factor u = 1 + F
I
205
5
.-.
8 200
Rg
-.
*
0
cl
u
.,
m
v
11
I
Y
[ l ] M . Di Vurru. S. Midollinr. L. Succonr. J. Am. Chem. Soc. 101. 1757 (1979).
and references therein.
121 C. Biunchini. C. Meulli. A Mrlr. L. Succoni, Inorg. Chim. Acta 37. L543
(1979).
[3] Philips PW 1100 automated diffractometer. Crystallographic data of (4):
u=17.55(1). b=15.90(1).
c=13.Xl(I)
= = I 1 1 S(1).
j3=91.l(l),
y = 1154(1) , triclinic. space group PI. Z = I ; and of l5): u=20.02(1).
h = l 5 7 2 ( l ) . c=16.33(1)
e = 1266(1). j3=91.0(1). y=93.5(1)'. triclinic.
space group Pi. Z= 2. Determination of structures with respectively 3760
and 4440 observed ( / 2 3 n ( / ) ) rtrucrural amplitudes. refined to R values of
0.079 (4) and 0.065 (5) [Rh. Ni. Co. P. F anisotropic. Ph rigid groupsl.
195
R*
A,
A.
190
.Rl
Calcium Isotope Separation on an Exchange Resin
Having Cryptand Anchor Groups[**'
185
I
50
A m l m [XI
By Klaus G. Heumann and Hans-Peter Schieferl'I
The stable heavy calcium isotopes ,'Ca and 4xCaare of interest primarily for labeling purposes in medical research"].
In 1977 a French research team reported the enrichment of
235Uby crown ethersl'l; Jepson and De Witt were able to enrich 44Ca relative to ,'Ca with the aid of dibenzo[l8]crown6c31. Since some of the cryptands are known to form strong
complexes with alkaline earth metalsi41,we have examined
calcium isotope separation on an exchange resin containing
the cryptand [2,.2.2] as anchor group.
['I
I"]
["'I
Prof. Dr K. ci. Heumann. Dr. H -P. Schiefer ['"'I
lnstitut fur Chemie der Universirat
UniversitAtsstrasse 31. D-8400 Regensburg (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft.
Present address: Centre de Recherches sur les Macromolecules. F-670x3
Straabourg (France)
406
0 Verlug Chemie, GmbH, 6440 Wernheirn.
1YXO
0
Fig. I Calcium isotope separation as lunction of the eluted amount of substance
R , = extrapolated isotope ratio
A m / m at 20 C R*=inilial isotopic ratio, R,, and
at A m / m = 0 or I
Figure 1 shows the dependence of the isotopic ratio
R = 4XCa/40Caupon the amount of substance eluted Am/m
at 20 "C. The relationship between R and Am/m is linear at
all the temperatures investigated; unlike comparable isotope
exchange reactions['] the isotope separation increases with
increasing temperature (Table 1).
In the first fractions eluted, R is higher than the initial isotopic ratio R', and lower in the final fractions. We therefore
have an enrichment of the heavier relative to the lighter calcium isotopes in the solution. The direction of this isotopic
enrichment is in accord with that of other cation exchanger/
aqueous solution systems["'.
057CJ-0X~.Z/XO/O.i05-4iJ~ $ O2.50/0
Angew. Chem. Ini. Ed. Engi. 19 (lY80)
No. 5
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