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Mixed-Anion Aggregates of Metalated Organics Preparation and Structure of the Mixed-Anion Tetramer (PhOLi ╖ HMPA)3(3-HMPA ╖ Li)NCS.

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and retained this activity over the next 48 hours. After this
period the conversion gradually decreased indicating slow
catalyst deactivation. The reaction was stopped after 75
hours, while the catalyst was still active, for catalyst characterization. The used catalyst again contained some metallic
platinum. Elemental and water analyses revealed that the
amount of water on the catalyst had increased slightly and
that some BF, had leached from the BF, . H,O phase.["'
These results implied that the BF,/H,O ratio decreased during the reaction, leading to a weaker and less active acid
system. Indeed, when BF, . 1.3H,O was used as a liquid
phase for the hydrogenation of benzene, the catalytic activity
dropped by 30 YO.
The effect of the lower acidity suggests that the reaction is
initiated by the protonation of the arene ring either by
H[BF,OH] or by a cationic platinum species formed by the
reaction of [PtCI,(MeCN),] and BF, . H,O under hydrogen.
In the first case the formed arenium ion is then hydrogenated
by a platinum species able to activate and transfer three
moles of molecular hydrogen. In contrast, in the second
mechanism the initially formed platinum complex activates
and transfers the H, to the already coordinated arene ring.
To gain further insight into how the catalytic system operates, we are currently investigating the hydrogenation of
[D,]benzene at 25°C and a H, pressure of 2.76 MPa." b 3 h 1
Preliminary GC-MS and NMR analysis of samples taken
periodically showed less than 0.5% D/H exchange for
[D,]benzene and the formation of 99.5% pure [D,]cyclohexane.1' 21 While the formation of platinum colloids cannot
be ruled out at present, the results are consistent with a
homogeneous platinum complex system operating in the liquid phase.
Received: February 1. 1991 [Z 44181E.3
German version: Angew. Chem. 103 (1991) 1042
CAS Registry numbers:
[PtCI,(CH,CN),I, 13869-38-0; BF, H,O, 15799-89-0; C,H,,, 110-82-7;
MeC,H,,, 108-87-2; Me,C,H,,, 583-57-3; Me,C,H,, 2234-75-5; benzene, 7143-2; toluene. 108-88-3; o-xylene, 95-47-6; naphthalene, 91-20-3; 1,2,4trimethylbenzene, 95-63-6; cis-decalin, 493-01-6; trans-decalin, 493-02-7.
[l] a) G. W. Parshall: Homogeneous Catalysis, Wiley, New York 1980; b) J. P.
Collman, L. S . Hegedus, J. R. Norton, R. G. Finke: Principles and Applications of' Organometallic Chemistry, University Science Books, Mill Valley, CA. USA 1987.
[2] a) R. Z. Moravec, W. T. Schelling, C. F. Oldershaw, GB-B511556;
b) R. Z. Moravec, W. T. Schelling, C. F. Oldershaw, CA-B396994;
c) G. J. K. Acres, D. C. Bond, B. J. Cooper, J. A. Dawson, J. Catal. 6
(1966) 139; d) P. R. Rony, Chem. Eng. Sci. 23 (1968) 1021; e) P. R. Rony,
J. Caial. 14 (1969) 142; f) P. R. Rony, J. M. Roth, .
I
Mol. Catal. 1(1975/76)
13: g) J. Villadsen, H. Livbjerg, Catal. Rev. Sci. Eng. 17 (1978) 203.
[3] While the letter S in the abbreviation of SLP catalyst can stand either for
supported or stationary liquid phase, the latter is perhaps a more accurate
and precise description for a catalyst of constant performance.
[4] a) G. E. Langlois, J. E. Walkey, Pet. Refiner 31 (1952) 79; b) R. E.
Robinson. U S A 3 190912; c) K. Fujimoto, Y Negami, T. Takahashi, T.
Kunugi, Ind. Eng. Chem. Prod. Res. Dev. 11 (1972) 303; ibid. 13(1972)237;
d) I. S. Shaw, J. S. Dranoff, J. B. Butt, Ind. Eng. Chem. Res. 27(1988)935;
e) J. P. Arhdncet, M. E. Davis, J. S . Merola, B. E. Hanson, Nature (London) 339 (1989) 454; L Caral. 121 (1990) 327; f) 1. T. Horvath, Cotal. Lett.
6 (1990) 43.
[5] a) E. L. Muetterties, F. J. Hirsekorn, J. Am. Chem. Soc. 96 (1974) 4063;
b) E. L. Muetterties, M. C. Rakowski, F. J. Hirsekorn, W. D. Larson, V. J.
Basus, E A. L. Anet ibid. 97 (1975) 751 ; c) M. J. Russell, C. White, P. M.
Maitlis, J. Chem. Soc. Chem. Commun. 1977, 427; d) P. M. Maitlis, Acc.
Chem. Res. 11 (1978) 301; e) E. L. Muetterties, J. R. Bleeke, ibid. f2 (1979)
324; f) M. A. Bennett, CHEMTECH 1980,444; g) R. H. Fish, Ann. N . Y.
Acad. Sci. 415 (1983) 292; h) J. Blum, I. Amer, K. P. C . Vollhardt, H.
Schwartz, G. Hohne, J. Org. Chem. 52 (1987) 2804; i) J. C. Cheng, J.
Maioriello, J. W. Larsen, Energy Fuels 3 (1989) 321 ;j) R. H. Fish, Aspects
Homogeneous Carol. 7 (1990) 65.
[6] a) CPG-240: silica, pore diameter 237 A; pore volume 0.95 m L g-'; surface area 77.5 m2g-'; b) clay (attapulgite): pore volume 0.5 mLg-'; surAngew. Chem. Int. Ed. Engl. 30 (1991) No. 8
0 VCH
[7]
[8]
191
[lo]
[ll]
[12]
face area 110m2g- I ; c) Shell Silica Spheres (S980 G): pore diameter 50 A,
pore volume l.OmLg-', surface area 80m2g-'.
The I9'Pt NMR spectrum of 0.28 g [PtCI,(MeCN),] in 5.6 g D,O shows
two signals at 6 = -2048 and -2070, both in the typcial chemical shift
region for Pt" metal complexes. The identification of this species is in
progress.
The hydrogenation reactions were performed at constant pressures in a
300mL-Hastelloy (H) autoclave equipped with a 7 pm filter attached to
the dip-leg for sample removal. In a typcial procedure the reactor was
charged with the catalyst and 70 g n-heptane as solvent under N, at 25 "C.
The arenes were added at reaction pressure, and the progress of the reactions were followed by GC analysis of samples taken periodically.
Pretreatment of the catalyst with 2.76 MPa (400 psi) H, for 18 and 89
hours decreases the rate of the hydrogenation of benzene by a factor 0.75
and 0.4 respectively.
A solution of 30% benzene in n-heptane was used at 0.25 mLmin-' feed
rate and 75 mLmin-' H, flow rate.
Addition of 0.5% BF,.OEt, to the feed did not stabilize the catalyst,
suggesting a complicated deactivation mechanism.
NMR spectroscopy of the C S , solution of [D,]cyclohexane revealed
the presence of two species in a ratio of 92 to 8. The elucidation of the
stereochemistry of C,H,D, is in progress.
Mixed-Anion Aggregates of Metalated Organics:
Preparation and Structure
of the Mixed-Anion Tetramer
(PhO@Li@HMPA),(p,-HMPA * Lie)NCSe **
By Paul R. Raithby, David Reed, Ronald Snaith,*
and Dominic S . Wright
We report the planned syntheses and structures of two
unusual lithium compounds. The lithium phenoxide complex 1 [HMPA = OP(NMe,),] is moisture-stable, and molecular mass measurements and 'Li, 31P NMR spectroscopy
show it to be a tetramer (n = 4)in arene solutions. Complex
1 has been used as a template in the course of developing a
route to mixed-anion metalated species. Thus, reaction of
phenol and an inorganic-anion source, ammonium thiocyanate (NH,NCS), with butyllithium (3 :1 :4 molar ratios)
in toluene containing HMPA affords 2. The crystal structure
of 2 shows that it also is a cubane-like tetramer; however, the
NCS@anion does not bridge Lie cations in a p, manner (as
the PhO" anions do), but rather one HMPA so bridges and
NCS@is terminal on one Lie.
(PhOeLie . HMPA),
1
(PhOeLie . HMPA),(p,-HMPA. Li@')NCSe
2
Complex 1 aroused our interest in view of our recent
findings that water can be a ligand within lithiated organics
ReLie (Re = alkyl, aryl, alkynyl, amido, enolato,
alkoxy etc.). Such species are notoriously moisture-sensitive,
i.e., equilibrium (a) lies to the right, yet in complexes such
as OxLi . TMEDA . H,O (Oxe = 2-mercaptobenzoxazoy1,
C,H,O(C=S)NO,
TMEDA = Me,N(CH,),NMe,),['al
['I
[**I
Dr. R. Snaith, Dr. P. R. Raithby, Dr. D. S. Wright
University Chemical Laboratory
Lensfield Road, Cambridge CB2 1EW (UK)
Dr. D. Reed
Department of Chemistry
West Mains Road, Edinburgh EH9 353 (UK)
This work was supported by Gonville and Caius College, Cambridge (Research Fellowship for D . S. M) and by the Associated Octel Co. Ltd.
( R . S.). We thank also the Science and Engineering Research Council
(S.E.R.C.) for the provision of high-field NMR facilities.
VerlagsgesellschajimbH. W-6940 Weinheim, 1991
0570-0833/91j0808-l01l $3.50+.25/0
1011
and
(OxLi . HMPA), . H,O,[lbl
ReLiQ
+ H,O F=? RH + LiQOHe
(a)
ReLie
+ H,O
(b)
(OxLi . HMPA . H,O),,
equation (b) is valid.
-
R e L i Q . OH,
also observable in the 31P NMR (145.79 MHz) spectrum
[Fig. 1 (b)]: recorded on the same solution of 1 at - 90°C,
this consists of the expected 1 :I:1:1 quartet (Z of ’Li = 3 / ~ ) ,
’J = 9.5 Hz.
The stability and structure of 1 made it an ideal template
for testing a synthetic strategy towards mixed-anion metalated species. Specifically, the recently described “ammonium
salt route”, which involves reacting solid NH,X salts with a
metal source (metal, hydride, or organometallic) and a Lewis
base (L), has afforded many complexes of type ( M a x b .xL),,
e.g., with M = Li, Na, K,15a-f1Sr, Ba,[sglLa, Eu, Mn;[shl
X = an inorganic anion like Hal, NCS, BF,; and L =
HMPA, TMEDA etc.
Integration of this route with a usual metalation procedure (RH metal source) should assemble mixed-union
complexes (X@ from NH,X, Re from RH), e.g., equation (c).
These aqua complexes are stable because the pK, of OxH
is slightly less than that of H,O, and H,O insertion displaces
m
the Ss- centers of the (NCS)Li chelate ring found in the
anhydrous complexes, resulting in stabilizing Ss- .. . H,O
hydrogen bonding. We reasoned, therefore, that an R@Li@
whose precursor RH is substantially more acidic than H,O,
and which has no displaceable functionality to engage in
hydrogen bonding with inserted H,O, should be moisturestable, i.e., the left-hand side of equilibrium (a) should dominate. Phenol is one obvious candidate. We found that reaction of PhOH with nBuLi (1:l) in toluene yielded an
amorphous white solid, (PhOOLi@),.However, a similar reaction in the presence of HMPA (1 equiv) afforded a solu- NH,X,,, + RH + 2nBuLi XL (LieXe) (ReLiQ). XL + NH, + 2nBuH
toluene
tion, which gave crystals of 1 on refrigeration. As anticipated, these crystals were indefinitely air-stable: the IR and ‘H
NMR spectra of samples exposed to air are identical to those
This idea works. It is easy to substitute just one PhOeLi@
of mulls and solutions made up under dry nitrogen. Indeed,
unit by Li@NCSein 1, n = 4. Thus, addition of nBuLi solu1 was recrystallized, unchanged, from aqueous toluene.
tion (4 equiv) to NH,NCS (1 equiv) suspended in a toluene
The crystal structure of 1 has not been resolved due to
solution of PhOH and HMPA (3 and 4 equiv, respectively)
disorder among HMPA ligands, but it is probably a cubanecaused a vigorous reaction accompanied by gas evolution.
like tetramer (see Fig. 1). Such tetramers are the norm for 1 :I
Chilling of the resulting solution afforded crystals of 2 in
good yield. In contrast to 1 , 2 is air-sensitive. The solid-state
structure of 216] (Fig. 2) is a tetrameric array with four Lie
+
-
-0.2 -0.1 -0.6 -0.8 -1.0
-6
Id
-1.2
21.6
23.8
21.2
-&
Ibl
Fig. 1 . NMR spectra of 1 in C,D,CD, at - 90°C. a) ’Li b) ”P. Inset: proposed tetrameric structure of 1.
Fig. 2. Molecular structure of 2 in the crystal.
complexes of lithiated organics containing monodentate
Lewis bases (L), such as lithium alkyls R,CLi, aryls ArylLi,
alkynyls RCECLi, imides R,C=NLi, and enolates
R( =CH,)COLi.[’I This widespread occurrence has been rationalized using ring-stacking ideas.[2d.31 A tetrameric structure is certainly evident from studies on 1 in solution.
Cryoscopic relative molecular mass measurements give association state (n)values of 3.7 f 0.2 (0.05 M benzene solution,
relative to n = 1) to 4.0 0.1 (0.20 M). The 7Li NMR
(139.96MHz) spectrum of 1 in C,D,CD3 (0.40 M) at
- 90°C consists of a doublet [Fig. 1 (a)] corresponding to
the coupling of each ’Li nucleus to the 31Patom of just one
(i.e., a terminal) HMPA ligand [2X,i3,p= 9.5 Hz]. Such coupling through (O=P) bonds has been seen before, in the 7Li
NMR solution spectrum of (LiBr), . 3 HMPA;l4] three p2HMPA ligands link the LiBr units, giving a 1:3:3:1 quartet
(,J = 3.8 Hz; note the stronger coupling for terminal HMPA
ligation in 1). However, for the first time, such coupling is
1012
Q VCH Verlagsgeseiischaft mbH. W-6940 Weinheim, 1991
ions, three of which bear terminal HMPA ligands (mean
Li-0 distance, 1.88(2) A). The three PhOe anions form p3
bridges across the metal cations (mean Li-0 distance,
1.98(2) A). However, the fourth bridging position is taken up
not by NCSO, which is terminal (Li-N distance, 2.04(2) A),
but by the fourth HMPA molecule (mean Li-0 distance,
2.11(2) A). Such a p3 mode for HMPA has been observed
once before, in the structure of (KNCS), . 5HMPA where
two of the HMPA ligands cap a triangle of K@ions.15e1
Two sets of earlier results are pertinent to our studies on
2. Firstly, IR spectroscopic investigations into the state of
aggregation of LiNCS in ether solvents have shown that the
CN stretching frequency is sensitive to structural changes :
the monomeric ion pair Li@NCSe(so with a terminal anion)
has this band at ca. 2060-2070 ~ m - ~the! (LieNCSe),
~ ~ ~
dimer (a p,-NCSe) at ca. 2030-2040cm-’,[7b1 and the
0570-0833/91j0808-1012$3.50+ ,2510
Angew. Chem. Int. Ed. Engl. 30 (1991) No. 8
(Li@NCSe), cubane tetramer (a p,-NCS@) at ca. 19902000 cm- '.17'l Mixed halide-thiocyanate cubanes, e.g., (LiBr), . LiNCS in Et,O [P(CN), 2003 cm-'1 have also been
detected.[7d1In the Nujol mull IR spectrum of 2 the major
band occurs at 2072 cm- in accord with the presence of
terminal (rather than p3-) NCSe ligands. Secondly, two
mixed organolithium-lithium bromide tetramers have been
isolated: (PhLi . OEt,), . LiBr['"] and [(cyclo-C,H,Li), .
(LiBr),] . 4Et,0.[8b1In both, the anions occupy corners of
the cube, and all the Et,O ligands are terminal (cf, the behavior of HMPA in 2). These complexes were isolated from
reactions of excess Li metal with PhBr and with cycloC,H,Br, respectively (yields: unspecified and ca. 30 %). Presumably in each case the major product is the complexed "pure" organolithium, (PhLi . OEt,),t8a1 and (cycloC,H,Li . OEt,),. Indeed, the major impetus of such work
was the fact that commercially supplied organolithium solutions (e.g., MeLi, PhLi), synthesized from Li RHal (2:1),
are often catalogued as containing lithium halide. The results
imply that specific mixed-anion aggregates are present in
such solutions, which possess different (often enhanced) reactivity from that of the "pure" reagent. However, the isolation of these RLi-LiBr species can be contrasted with the
currently described planned assembly of mixed-anion aggregates as the only product, as exemplified in the synthesis of
2.
We are exploring the implications of the syntheses and
properties of 1 and 2. Complex 1 establishes likely thermodynamic ground rules for preparing moisture-stable metalated
organics. The synthetic strategy leading to 2 promises particularly wide scope. R in RH, X in NH,X, the metal M, and
the donor L of equation (c) could all be varied, as could the
Re :Xo stoichiometry (3 :I PhO' :NCSQ in 2). Most importantly, the metal aggregate need not be a tetramer: even
restricting M to Li, (RLi), aggregates are knownI2] with
n = 2 and 3 (rings), 4 (rings and cubanes), 5 (trigonal bipyramid), 6 (pseudooctahedron), 8 (stacked dimeric rings), and
higher.
',
+
Seebach. Angew. Chem. 100 (1988) 1685; Angew. Chem. I n / . Ed. Engl. 27
(1988) 1624; c)G. Boche, i6id. 101 (1989) 286 and 28 (1989) 277; d) K.
Gregory, P. von R. Schleyer, R. Snaith, Adv. Inorg. Chem., in press.
[3] a) D. Barr, W Clegg, R. E. Mulvey, R. Snaith, K. Wade. J. Chem. Soc.
Chem. Commun. 1986, 295; b) D. R. Armstrong, D. Barr, R. Snaith, W.
Clegg, R. E. Mulvey, K. Wade, D. Reed, J Chem. Sor. Dulton Trans. 1987.
1071; c) D. Barr, R. Snaith, W. Clegg, R. E. Mulvey, K . Wade, ibid. 1987,
2141.
[4] D. Barr, M. J. Doyle, P. R. Raithby, R. Snaith, D. S. Wright, R. E. Mulvey,
D. Reed, J Chem. Soc. Chem. Commun. 1989, 318.
[5] a) D. Barr, R. Snaith, D. S. Wright, R. E. Mulvey, K. Wade, J Am. Chem.
Soc. 109 (1987) 7891 ;b) D. Barr, M. 1. Doyle, R. E. Mulvey, P. R. Raithby,
R. Snaith, D. S. Wright, J Chem. Soe. Chem. Commun. 1988, 145; c) D.
Barr, M. J. Doyle, S. R. Drake, P. R. Raithby, R. Snaith, D. S. Wright, i6id.
1988, 1415; d) Polyhedron 8 (1989) 215; e) Inorg. Chem. 28 (1989) 1767;
f ) D. Barr, M. J. Doyle, P. R. Raithby, R. Snaith, D. S. Wright, R. E. Mulvey, D. Reed, 1 Chem. Soc. Chem. Commun. 1989, 318; g) D. Barr, A. T.
Brooker, M. J. Doyle, S. R. Drake, P. R. Raithby, R. Snaith, D. S. Wright,
i6id. 1989, 893; h) Angew. Chem. 102 (1990) 300: Angew. Chem. Inr. Ed.
Engl. 29 (1990) 285.
monoclinic, P 2 J a (alternative
[6] Crystal data for 2 : C,,H,,N,,O,P,SLi,,
setting P2,/c, No. 14), a = 15.165(2), 6 = 18.189(2), c = 23.314(4) A,
p = 108.27(1)", M = 1322.16, V = 6106(2) A', Z = 4. ecSlcd
=
1.438 gcm-3, F(OO0) = 2320, Mo,,-radiation, i.
= 0.71069 A, p(Mo,J =
1.71 cm-'. The structure was solved by a combination of direct methods
and Fourier difference techniques and refined by blocked-matrix leastsquares. Some of the HMPA ligands show considerable disorder. P. 0, Li.
the NCS ligand, and the ordered N atoms from the HMPA ligands refined
anisotropically. Phenyl and methyl-H atoms on ordered HMPA ligands
placed in idealized positions, allowed to ride on the relevant carbon atoms,
and refined with a common isotropic thermal parameter. One HMPA ligand severely disordered; two sites of disordered N and C atoms refined with
partial occupancies. 8663 reflectionsmeasured ( 5 < 20 < 45"),corrected for
absorption and decay. 4453 unique observed with F > 50(F). R = 0.100,
R , = 0.109. Further details of the crystal structure investigation may be
obtained from the Director of the Cambridge Crystallographic Data
Centre, University Chemical Laboratory, Lensfield Road, Cambridge CB2
IEW (U.K.). Any request should be accompanied by the full literature
citation for this communication.
[7] a) D. Paoli, M. Lucon, M . Chabanel, Specrrochim. Acrcr Purr 34 (1978)
1087; b) ibid. 35 (1979) 593; c) M. Chabanel, M. Luqon, D. Paoli, J Phys.
Chem. 85 (1981) 1058; d) P. Goralski, M. Chabanel, Inorg. Chem. 26 (1987)
2169.
[8] a) H. Hope, P. P. Power, J Am. Chem. SOC.105 (1983) 5320; b) H. Schmidbaur, A. Schier, U. Schubert, Chem. Ber. 116 (1983) 1938, and references
therein.
[9] D. Reed, D. Barr, R. E. Mulvey, R. Snaith, J. Chem. SOC.Dalron Trans.
1986. 557.
Experimental Procedure
1: n-Butyllithium (6.3 mL, 1.60 M solution in hexane, 10 mmol) was added at
20°C to a solution of phenol (0.94 g, 10 mmol) and HMPA (1.79 g, 10 mmol)
in toluene (10 mL). A vigorous exothermic reaction ensued, producing a colorless solution. Refrigeration at 0°C for two days gave an initial crop of colorless
cubic crystals of 1. First batch yield 0.91 g, 33%; further cooling afforded more
of 1; no other product was isolated. M.p. > 260°C (decomp.); correct C, H, Li,
N, P analyses; 'H NMR (C,D,, 250 MHz, 25°C) 6 =7.33 (m,4H, 0-and m-H
of PhO'), 6.79 ( t of t , 1 H,p-H ofPhO'), 2.35 (d, 18H of HMPA, J = 9.3 Hz).
Cryoscopic relative molecular mass measurements on 1 were carried out using
previously described procedures [9].
2 : n-Butyllithium (6.3 mL, 1.60 M solution in hexane, 10 mmol) was added at
20°C to a stirred suspension of NH,NCS (0.19 g, 2.5 mmol) in toluene (10 mL)
containing dissolved PhOH (0.71 g, 7.5 mmol) and HMPA (1.79 g, 10 mmol).
A vigorous exothermic reaction and gas evolution ensued, during which all of
the solid NH,NCS reacted. The resulting solution was cooled to room temperature, giving colorless cubic crystals of 2. First batch yield 1.51 g, 60%; further
cooling afforded more of 2; no other product was isolated. M.p. 240°C (decamp.); correct C, H, N, P analyses; IR: (Nujol mull) B(CN) of NCS' at
2072 cm-' (vs), 2031 cm-' (m); 'H NMR (C,D,, 250 MHz, 20°C) 6 centered
at 7.29 (m. 15H of 3PhOe), 2.38 (d, 72H of 4HMPA, J = 9.1 Hz).
Received: February 28,1991 [Z 4462/4463]
German version: Angew. Chem. 103 (1991) 1040
CAS Registry numbers: 1, 134940-44-6; 2, 134940-45-7
[l] a) D. Barr, P. R. Raithby, P. von R. Schleyer, R. Snaith, D. S. Wright, J.
Chem. Sor. Chem. Commun. 1990,643; b) D. R. Armstrong, D. Barr, P. R.
Raithby, P. von R. Schleyer, R. Snaith, D. S. Wright, Inorg. Chim. Actu, in
press.
[2] For reviews describing the crystal structures of lithiated organics see: a ) W.
Setzer, P. yon R. Schleyer, Adv. Orgunomer. Chem. 24 (1985) 353; b) D.
Angeu,. Chem. I n / . Ed. Engl. 30 (1991) No. 8
0 VCH
Conversion of a Diatropic Bridged Annulene
into a Paratropic Species on Metal Complexation**
By Reginald H . Mitchell* and Pengzu Zhou
Very little is known about metal-complexed large ring annulenes. A recently prepared['] tris-(pacety1ene)dicobalt
complex containing the cyclo-C,, ligand grossly distorts the
acetylenic bond so that comparison with the as yet unknown
ligand will be difficult. Tricarbonylchromium complexes of
two bridged [lO]annulenes, 1,6-methano[IO]annulene,and
2,7-methanoaza[IO]annulene, have been described by
Giinther et aI.['l and Vogel et aLr3I respectively, as having
delocalized Ion-electron systems. The complexation of a
[14]annulene such as 1 interested us since it does not have a
conveniently arranged set of six p orbitals to complex to
chromium in contrast to the [lO]annulenes above. Moreover,
the chemical shift of the internal methyl protons in 1 and its
derivatives is an excellent probe for the delocalization pres[*I Prof. R. H. Mitchell, Dr. P. Zhou
Department of Chemistry, University of Victoria
Box 3055, Victoria, B.C. V8W 3P6 (Canada)
[**I We thank the Natural Sciences and Engineering Research Council of
Canada and the University of Victoria for the support of this work.
Verlagsgesellschaf/ mbH, W-6940 Weinheim. 1991
0570-0833/91/0808-1013 $3.504. .25/0
1013
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preparation, tetramer, structure, organics, ncs, pholi, aggregates, anion, mixed, hmpa, metalated
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