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Assembly of the [CAu6]2 Cluster with a Tailor-made Diphosphane Spanning the Octahedral Edges.

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Assembly of the [CAu,jZ@Cluster with a Tailor-made
Diphosphane Spanning the Octahedral Edges **
By Oliver Steigelmann, Peter Bissinger,
and Hubert Schmidbaur *
Accumulating experimental and theoretical evidence suggesting the existence of hypercoordination at carbon by gold
and related d" elements has led to a systematic search for
compounds featuring carbon and other elements completely
surrounded by gold atoms ("gilded atoms"). The initial series of investigations resulted in the synthesis and characterization of the extremely stable species [RC(AuL),]@,
[C(AuL),]@, and [C(AuL),]'@, containing penta- and even
hexacoordinate carbon atoms in the center of square pyramids, trigonal bipyramids, or octahedra of gold atoms, reThis chemistry has meanwhile been
spectively (A -C).['
extended to include the atoms boron, nitrogen, silicon, and
phosphorus as nucleation centers for gold. Pertinent results
cover not only more classical species like [RN(AuL),]@ and
[RP(AuL),]@,but also the unprecedented di- and trications
[N(AuL)~]'@,[N(AuL)J3@,and [P(AuL),]'@ (D-F).''. 5 - 8 1
In all compounds obtained to date the ligand L is
monodentate triphenylphosphane. The simple question
therefore arose whether the novel element-centered gold
clusters could also be prepared with other auxiliary donors,
especially chelating ligands. Bidentate ligands, for example,
could further stabilize the electron-deficient, hypercoordinate clusters and also impose different symmetry properties
and chirality. We now report the assembly of the [CAu,]'@
core triply chelated by a new diphosphane, (1.2C,H,)(CH,CH,PPh,), , tailor-made to span the edges of the
[CAuJ2@octahedron.
A
B:X=C, n = l
D: X = N, n = 2
F:X=P, n = 2
C: X
=
E: X
=
C, n = 2
N, n = 3
Graphical evaluation of models based on the geometry of
the [C(AuL),]'@ cation13] has shown that a ligand
R,P(CH,),PR, should contain a chain with m = 6 in order
to bridge the vertices of the metal octahedron if the C-Au-P
axes are required to be linear. Molecular modeling suggested
that a ligand such as I should provide the required P . - . P
distance and acceptor orbital orientation at neighboring
gold atoms (Scheme 1).
C
/\
CH,CH,PPh,
CH,CH,PPh,
A I \A,
/
\PPh
Ph p .__............
2 h PJ
1
Scheme 1.
[*] Prof Dr. H Schmidbaur, DipLChem. 0. Steigelmann, P. Bissinger
I"']
Anorganisch-chemisches Institut der Technischen Universitit Munchen
Lichtenbergstrasse 4 , W-8046 Gdrching (FRG)
This work has been supported by the Deutsche Forschungsgemeinschaft
(Leibniz-Programm) and the Fonds der Chemischen Industrie and by
Hoechst AG, Degussa AG, and W C. Heraeus GmbH.
Angew Chrm. In(. Ed. Engl. 29 (1990) N o . 12
8 VCH
1,2-Bis(2-diphenylphosphinoethyl)benzene (I) [m.p.
71 "C, 6(3'P) = - 15.11 was prepared starting from 1,2-bis(cyanomethy1)benzene as shown in Scheme 1. Most of the
conversions, involving standard procedures, gave satisfactory yields. Treatment of the ligand 1 with tetrachloroauric
acid in the presence of a thioether as a reducing and complexing agentCg1
finally afforded the pale-yellow dinucledr complex 2 [m.p. 205 "C (dec.), c ~ ( ~ ' =
P )29.21 in ca. 65 % yield as
the key reagent for assembly of the carbon-centered cluster
(Scheme 2).
CH,CH,PPh,.
R2S
aCH,CHzPPh2.
AuCl
AuCl
2
Scheme 2. Synthesis of 2.
Reaction of the gold complex 2 with tetrakis(dimeth0xyb~ryl)methane[~,
"1
in hexamethylphosphoric triamide
(HMPT) in the presence of cesium fluoride produced an
orange solution. After filtration and precipitation with a
benzene/pentane mixture, yellow crystals of 3 were obtained
in about 10% yield (m.p. 155°C with decomposition)
[Eq. (all.
Compound 3 was identified by elemental analysis and field
desorption mass spectrometry. The parent peak at miz
1350.7 is readily assigned to the dication in 3 (in CH,CI,).
The 31P(1H) NMR spectrum (in CD,CI,) shows a single
resonance at 6 = 24.3. Both the 'H and the I3C NMR spectra exhibit sets of signals indicating not only virtual threefold
symmetry of the dication in solution, but also an internal
twofold symmetry of the ligand (C,) which renders the ligand halves equivalent." 'I The resonance of the central carbon atom could not be observed, but the counterions have
been detected through their "B resonance (6 = - 17.9,
'J(BF) = 17.1 Hz).
The structure of the new cluster cation was determined by
X-ray diffraction.[' Crystals grown from dichloromethane/
benzenelpentane solution (monoclinic, space group C2jc,
Z = 4) contain one molecule of crystal benzene per stoichiometric unit. The dication [CAu6(l),l2@does not obey the
high point-group symmetry (D3d)suggested by the NMR
spectra of the solutions, but exhibits only crystallographic
C, symmetry with the twofold axis passing through the central carbon atom and through the centers of two C-C bonds
on opposite sides of one of the ortho-phenylene rings
(Fig. 1). Each dication is a chiral entity, which is related with
a neighboring enantiomer by a center of symmetry.
The CAu, core can be described as a distorted carbon-centered octahedron of gold atoms with Au . . .Au distances between 2.942(2) and 3.132(2) A and with C-Au distances of
2.09(3), 2.15(3), and 2.13(3) A. The three independent Au-P
distances and C-Au-P angles are equal within the limits set
by the rather large standard deviations for these parameters.
Verlagsgesellschaft mbH, W-6940 Weinheim. 1990
OS70-0833/90//2/2-1399$3.50+2510
1399
CAS Registry numbers:
1. 118636-00-3; 2, 129731-20-0; 3, 129731-22-2; 3 . C,H,, 129756-46-3; 1,2C,H,(CH,CH,CN), , 613-73-0; l,2-C6H,(CH2C0,Et),, 17532-66-0; 1,2C,H,(CH,CH20H),,
17378-99-3; 1,2-C,H,(CH,CH2Br),,
17379-00-9;
CIPPh,, 1079-66-9, HAuCl, 3 H 2 0 . 16961-25-4, C[B(OCH,),J,, 17936-80-0.
'
d
Fig. 1. Structure of the dication o f 3 in the crystal [12] (ORTEP, thermal ellipsoids drawn at 50% probability for Au, P; arbitrary radius for C; H atoms
omitted for clarity). Selected distances [A] and angles ['I: Aul-Aul' 2.979(3),
Aul-Au2 2.947(2), Aul-Au3 2.942(2), Aul-Au3' 2.985(2) Au2-Au3 3.094(2),
Au2-Au3' 2.982(2),AuZ-AU~'
3.132(2), C-Aul 2.15(3), C-Au2 2.09(3). C-Au(3)
2.13(3), PI-Aul 2.266(9), P2-Au2 2.267(9), P3-Au3 2.275(9); C-Aul-PI
177.3(3); C-Au2-P2 175.3(9), C-Au3-P3 175.8(9).
The structure of the dication in 3 is thus very similar to
that of the parent hexakis(tripheny1phosphane) cluster.
Though the yields are not really satisfactory, the successful
synthesis of the triply chelated cluster 3 and its thermal and
chemical stability support the validity of the aurophilicity
concept advanced in an attempt to account for formation
and bonding of this new type of coordination.r'.3.131It is
important to note here that all attempts to prepare clusters
of the types [C(AgL)J"@ and [C(CuL),J2@ have met with
failure, whereas work in progress on other functional or
polychelating organophosphane complexes of the [CAu,J2@
unit continue to show promising results.
Experimental Procedure
1 (Scheme 2): a) 1,2-Bis(cyanomethyl)benzene (40.0 g, 0.256 mol) in ethanol
(95%. 125 mL) was treated with concentrated H,SO, (1OOg) and refluxed for
7 h. Hydrolytic workup afforded the ethyl ester (47.1 g, 73%), b.p. 146-8 "C/l
Torr) [14]. b) This ester (45.0 g, 0.1 8 mol) in diethyl ether (225 mL) was reduced
by LiAIH, (12.8 g, 0.34 mol, in 850 mL of Et,O). Workup in aqueous sulfuric
acid yielded 10.5 g of the diol(35%, m.p. 61 "C (from benzene)) [15]. c) The diol
(5.8 g, 35 mmol) was treated with aqueous HBr (120 mL. 80%) for 5 h at reflux
temperature. Extraction with CH,CI, and distillation gave 7.3 g of the dibromide (72%. b.p. 134 "C/l Torr) [16]. d) A red solution of LiPPh, was prepared
from Li powder (1.52 g, 220 mmol) and CIPPh, (1 1.1 g, 50 mmol) in THF
(100 mL) at reflux temperature (30 min) under nitrogen. This solution was
treated with the dibromide precursor (7.32 g, 25 mmol) in T H F (30 mL) at
0-65 "C. Workup with aqueous HCI (30 mL. 10%) yielded ligand 1 (6.0 g,
48%. m.p. 71 ' C (from ethanol)). I3C('H} NMR (CD,CI,): d = 29.3 (d,
6 = 139.2(d,
J(PC) = 18 Hz), 29.8 (d, J(PC) = 14 Hz; CH,) C,H,:
J(PC) = 14Hz; Cl,C2). 129.4 (C3,C6), 126.6 (C4,CS). C,H,: 6 = 140.6 (d,
J(PC) = 13 Hz; ipsu-C), 133.0 (d, J(PC) = 19 Hz; o-C). 128.9 (d,
J(PC) = 13 Hz; m - C ) , 128.9 (p-C). "P{'H} NMR (CD,Cl,): 6 = - 15.1 [17].
2 and 3: HAuCI, . 3H,O (3.67 g, 9.3 mmol) was dissolved in ethanol (50 mL)
and treated with thiodiglycol(3.41 g, 27.9 mmol) in ethanol (20 mL) at 0 "C [9].
As soon as the yellow color had vanished, ligand 2 (2.34 g, 4.66 mmol) was
added in acetone (50 mL). The pale yellow precipitate of 2 was collected after
12 h ( M g , 62%, dec. at 205°C). '3C('H} NMR (CDCI,. see I for assignments, J(PC) coupling constants in parentheses): 28.2(4), 29.3(36); 137.3(14),
129.3, 127.6; 128.8(60), !33.2(13), 129.5(11), 132.2. "P('H) NMR (CDCI,):
6 = 29.2.
Complex 2 (2.1 g, 2.17 mmol) and CsF (4.32 g, 28.4 mmol) in HMPT (60 mL)
were treated with a solution of C[B(OCH,),], (0.220 g, 0.725 mmol) in the same
solvent (20 mL) for 48 h at 20 "C under N,. The orange solution was filtered
and the product precipitated with pentane/benzene. Repeated extraction with
CH,CI, and reprecipitation with pentane/benzene afforded yellow crystals of 3
(0.20 g, to%, dec. at 155 C ) . For NMR data see [ill.
Received' June 8, 1990 [Z 4000 IE]
German version: Angew. Chem. 102 (1990) 1473
1400
0 VCH Verlagsgesellschaft mbH, W-6940 Weinherm, 1990
[l] H. Schmidbaur, Gold Bull. 23 (1990) 11.
121 F. Scherbaum. B. Huber, G. Miiller, H. Schmidbaur, Angew. Chem. 100
(1988) 1600, Angew. Chem. Inr. Ed. Engl. 27 (1988) 1542.
[31 F. Scherbaum, A. Grohmann, B. Huber, C. Kriiger, H. Schmidbaur,
Angew. Chem. 100 (1988) 1602; Angew. Chem. Inr. Ed. Engl. 27 (1988)
1544.
[41 F. Scherbaum, A. Grohmann, G. Mijller, H. Schmidbaur, Angew. Chem.
101 (1989) 464; Angew. Chem. Int. Ed. Engl. 28 (1989) 453.
IS] A. Grohmann, J. Riede, H. Schmidbaur, Nature (London) 345 (1990) 140.
[6] J. Strihle et al. (Tiibingen), personal communication.
171 G. Weidenhiller, H. Schmidbaur. unpublished.
[XI For theoretical papers: see D. M. P. Mingos, Nature (London) 345 (1990)
113, and references cited therein. See also V. Ramamoorthy, P. R. Sharp,
Inorg. Chem. 29 (1990) 3336.
[9] A. K. Al-Sa'Ady, C. A. McAuliffe, R. V. Parish, J. A. Sandbark, Inorg.
Synth. 23 (1985) 191.
[lo] R. B Castle, D. S. Matteson, J. Am. Chem. Soc. 90 (1968) 2194; J
Organomer. Chem. 20 (1969) 19.
[ I l l 3: 'H NMR (CD,CI,): 6 = 2.57-2.61 (m, 12H). 2.91-2.93 (m, 12H;
CH,), 7.0-7.6 (m, 72H; Aryl). "C('HJ NMR (CD,CI,): C,H,:
d = 127.3 (d, J(PC) = 61.6Hz; rpso-c), 133.2 (m. o-C), 129.8 (m. m-C),
132.5 ( s , p-C), C,H,: 135.2 (d, J(PC) = 12 Hz; Cl,C2), 132.2 ( s , C3,C6),
129.9 ( s , C4,C5), CH,. 6 = 29.3(s), 31.6 (d, J(PC) = 32 Hz). "P('HJ
NMR (CD,CI,): 6 = 24.3(s).
[12] Crystal data and structure solution for 3 . C,H,: C,,,H,,,Au,B,F,P,,
M , = 2873.2; monoclinic, spacegroup C2/c, a = 14.677(3),b = 36.141(4),
c = 20.656(3) A,
= 97.26(2)",
V = 10868.9 A3, 2 = 4,
=
1.805 gcm-',p(Mo,,)
=78.9 cm-', EnrafNoniusCAD4diffractometer.
Mo,, radiation, i.= 0.71069 A, T = 23 "C, 9524 independent reflections,
5239 observed with F, 2 4.Ou(F0); empirical absorption correction
( T = 0.81 -1.00).
Solution by direct methods (SHELXS-86),
R(R,) = 0.075(0.088) for 273 refined parameters (Au, P anisotropic; C
isotropic. BF, calculated in idealized geometry in the region of high residual electron density with Ui,, = 0.25 for B and F), Ae,,,(max/
min) = 4.43/-2.21 e/A3. (The high R values and relatively large standard deviations arise from the poor quality of the crystals.) Further details
of the crystal structure investigation are available on request from Fachinforrnationszentrum Karlsruhe, W-7514 Eggenstein-Leopoldshafen
(FRG), on quoting the depository number CSD-54804, the names of the
authors. and the journal citation.
1131 N. Rosch, A. Gorling, D. E. Ellis, H. Schmidbaur, Angew. Chem. 101
(1989) 1410; Angew. Chem. Inr. Ed. Engl. 28 (1989) 1357.
[14] R. Adams, A. F. Thal: Organic Syntheses CoNecrive Volume I , 2nd ed.
Wiley, New York 1941, p. 270.
1151 J. 0. Halford, B. Weissman, J Org. Chem. 17 (1952) 1646.
[16] C. W Muth, D. 0 . : Steininger, 2. B. Panastassiou,J Org. Chem. 77(1955)
1006.
1171 E. Vincent, L. Verdonck, G. P. van der Kelen, Spectrochim. Acta Part A
36, (1980) 699; B. E. Mann, J. Chem. Soc. Perkin Trans 2. 1972, 30.
+
Amine-Template-Directed Synthesis
of Cyclic Porphyrin Oligomers **
By Harry L. Anderson and Jeremy K. M . Sanders*
The use of guest molecules as templates for directing the
assembly of complementary host structures is a recurrent
theme in many areas of biochemistry. It is aIso an approach
widely used in the synthesis of coronands,['l catenaries,"]
functionalized polyrner~,'~'and biomimetic systems such as models for enzymic catalysis''' and self-replica[*I
Dr. J. K. M. Sanders, H. L. Anderson
Cambridge Centre for Molecular Recognition
University Chemical Laboratory
Lensfield Road, Cambridge CB2 IEW (UK)
[**I This work was supported by the Science and Engineering Research Council (UK).
0570-0833~90/1212-1400$3.50+ 2510
Angeu. Chem. In!. Ed. Engl. 29 (1990) No. 12
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