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Methylene-Bridged Dinuclear Gold(III) Complexes with Terminal and Bridging Ylide Ligands.

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2 [(Et,N),PCH,],
6 (Et,N),P=CH,
4 TiCI,
CAS Registry numbers:
3, 101981-46-8; 4, 101998-21-4; (Et2N),P=CH2, 98297-72-4; T i C L 7550-45-0.
\ /
/ \
\ /
/ \
ci ci
on the ylidic C atom by Ti atoms. Reaction of
(Et2N),P=CH2 with TiCI, in diethyl ether results in immediate formation of a violet solution, from which the
bis(phosphorany1idene)dititanacyclobutane 4 can be isolated in over 70% yield. The formation of the by-product
tris(diethylamino)methylphosphonium hexachlorotitanate
3 (yield 80%) proves the stoichiometry of the transylidation. The structure of the analogous hexachlorozirconate
was recently established by X-ray diffraction analysis.151
The cyclic double ylide 4 is even soluble in solvents of low
polarity. The 3'P('H)-NMR spectrum of 4 in benzene exhibits a singlet at 6=26.22. The 'H- and I3C-NMR spectra
establish the equivalence of all 12 ethyl groups.161The signal of the ylidic C atom could not be located with certainty. Black-violet crystals form from toluene at -78°C; the
X-ray structure analysis gave the centrosymmetric molecular structure shown in Figure l."]
[ I ] H. Schmidbaur, Angew. Chem. 95 (1983) 980: Angew. Chem. Int. Ed.
Engl. 22 (1983) 907; W. C. Kaska, Coord. Chem. Rev. 48 (1983) I ; L.
Weber in F. R. Hartley, S. Patai (Eds.): 7'be Chemistry o f t h e Meral-Curbon Bond. Wiley, Chichester 1982, p. 91.
121 W. Keim, F. H. Kowaldt, R. Goddard, C. Kriiger, Angew. Chem. 90
(1978) 493: Angew. Chem. Inr. Ed. Engl. 1 7 ( 1978) 466; W. Keim, A. Behr,
B. Limaacker, C . Kriiger, ibid. 95 (1983) 505 and 22 (1983) 503; Angew.
Chem. Suppl. 1983, 655; K. A. Ostoja Starzewski, J. Witte, Angew. Chem.
97 (1985) 610; Angew. Chem. I n t . Ed. Engl. 24 (1985) 599.
[3] Ylides with substituents from the main groups of the periodic table: H.
Schmidbaur, Arc. Chem. Res. 8 (1975) 62; Adv. Organomet. Chem. 14
(1976) 205; derivatives of early-transition-metal elements: a) H. Schmidbaur, W. Scharf, H.-J. Fuller, Z. Nuturforsch. 8 3 2 (1977) 858; b) H.
Schmidbaur, R. Pichl, ibid. 40 (1985) 352; c) J. C. Baldwin, N. L. Keder,
C. E. Strouse, W. C. Kaska, ibid. 35 (1980) 1289; d ) K. I. Cell, J.
Schwartz, Inorg. Chem. 79 (1981) 3207; e) G. W. Rice, G. B. Ansell, M. A.
Modrick, S. Zentz, Organometallics 2 (1983) 154; f) G. Erker, P. Crisch.
C. Kriiger, J. M. Wallis, ibid. 4 (1985) 2059; g) R. E. Cramer, R. B. May103 (1981) 3589; 100 (1978) 5562;
nard, J. W. Giije, J. Am. Chem. SOC.
Inorg. Chem. 20 (1981) 2466; 19 (1980) 2564.
[4] See also 13a-O: this is also in agreement with unpublished results (R.
Pichl, Munich 1985).
[5] H. Schmidbaur, R. Pichl, G. Miiller, Z. Naturforsch. 8 4 1 (1986) 395.
161 Experimental procedure: TiCI, (1.33 mL, 2.30 g, 12.1 mmol), dissolved in
2 0 m L of toluene, was added slowly to a solution of (Et2N),P=CHZ
( 5 mL, 4.76 g, 18.2 mmol) in 30 mL of diethyl ether at room temperature.
The reaction mixture immediately turned violet. Upon cooling the reaction mixture to -78"C, 3 precipitated out (yield 3.8 g, 79%) and was filtered off and then washed with toluene. The solvent was removed from
the filtrate and the residue was recrystallized from toluene (1.6 g, 69%).
The product 4 gave a correct elemental analysis, dec. temp. = I 8 0 T . 'H-NMR (CeD,): 6= 1.07 (1, 'J(HCCH)=7.2 Hz; CHJ), 3.04 (dq,
'J(PNCH)= 10.4 Hz; CH,). "C-NMR (C,D,): 6=36.22 (d, 'J(PC)=3.7
Hz; CHI), 62.18 (d, 2J(PC)=2.4 Hz: CHI). "P('HJ-NMR (C6D,):
6=26.22 ( ~ ) . - 3 : 'H-NMR (CDC12): 6= 1.12 (t. 'J(HCCH)=7.4 Hz;
CH,), 2.45 (d, 2J(PCH)= 12.2 HI;CHXP), 3.01 (dq, 'J(PNCH)= 108 Hz;
CH2). "P('H}-NMR (CDCI1): 6=58.89 (s).
I71 Crystal structure data: orthorhombic, space group Pbca* (No. 61),
a=14.827(1), b = 16.399(1), c = 16.223(1)
V=3944.6 A>, Z = 4 ,
1.273 gcm-',p=7.8 c m - ' , F(000)= 1600. 5723 unique reflections,
of which 3388 observed with I 2 2 . 0 u ( f ) . ((0-20)
A o = I . 0 + 0 . 3 5 t a n @ (sinH/A),.,,=0.703, hkl: +20, +23, +22, Mo,,,,
A=0.71069 A, T=22"C, CAD4). Direct methods (MULTAN 82).
R =0.041, R,=0.052, GOF: 1.32 for 181 refined parameters (anisotropic,
H constant, SDP-PLUS), Api,,(max)=0.35 eA -'. Further details of the
crystal structure investigation may be obtained from the Fachinformalionszentrum Energie. Physik, Mathematik GmbH, D-75 14 EggensteinLeopoldshafen 2 (FRG), on quoting the depository number CSD 51 739,
the names of the authors, and the journal citation.
Fig. 1. Crystal structure of 4 (ORTEP, thermal ellipsoids 50%, without H
atoms). Selected bond lengths [A] and angles ["I: Ti-CII 2.278(1), TiCC12
2.280(1), Ti-CI 1.957(2), Ti-CI* 1.957(2), P-CI 1.729(2), P-NI 1.656(2), P-N2
1.665(2), P-N3 1.644(2); CIl-Ti-CI2 110.69(3), C11-Ti-Cl 116.32(7), CII-TiC l f 113.12(7), CI2-Ti-CI 110.76(7), C12-Ti-CI* 117.04(7), CI-Ti-CI*
87.27(9), Ti-CI-Ti* 92.73(9), Ti-CI-P 128.0(1), Ti*-Cl-P 136.9( I)..
The most important detail of this structure, which has a
nearly planar PCTi,CP framework, is the existenceoof four
equal, remarkably short Ti-C distances (1.957(2) A). This
finding can be explained by the delocalization of the negative charge of the ylidic carbon atom into the Ti2Czfourmembered ring. The four C1 atoms are not completely symmetrically arranged with respect to the four-membered
ring; this is revealed in part by the significantly different
Cl-Ti-Cll(2) angles.
The easily accessible complex 4 should prove to be an important starting material for numerous reactions.
Received: January 24, 1986 [Z 1538 IE]
German version: Angew. Chem. 98 (1986) 572
Angew. Chem. Int. Ed. Engl. 25 (1986) No. 6
Methylene-Bridged Dinuclear Gold(II1) Complexes
with Terminal and Bridging Ylide Ligands**
By Hubert Schmidbaur* and Christoph Hartmann
Cyclic Au'-ylide complexes 1['-31
are important model
compounds for the oxidative addition of alkyl halides to
multinuclear metal c o m p l e x e ~ . [Spectroscopic
and structural data indicate the occurrence of an Au- . - A u
interaction in 1, which facilitates both metal atoms assuming the unusual oxidation state + I ] . Both monohaloalkanes as well as geminal di- and trihaloalkanes and even
tetrahalomethanes add to the ring system in such a way
that a genuine transannular metal-metal bond is first
formed (2), which, in the case of polyfunctionalized halo[*] Prof. Dr. H. Schmidbaur, Dipl.-Chem. C. Rartmann
Anorganisch-chemisches lnstitut der Technischen Universitat Munchen
Lichtenbergstrasse 4, D-8046 Garching (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and by Hoechst AG and Degussa
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0570-0833/86/0606-0575 $ 02.50/0
the H-atoms of the *CH, bridge and of the exocyclic C H I
groups are in each case equivalent. Accordingly, the I9'AuMossbauer spectra of 5a, b show in each case a doublet
with almost equal values for the isomeric shift IS and the
quadrupole coupling constants QS (Fig. l), thus also providing proof of the equivalence of the metal atoms and
their oxidation state (+ III).["~
alkanes is readily transformed in a subsequent step into
a methylene bridge (3).[51With suitable substrates these
processes are at least partly reversible: thus, after methylation of the gold atoms in 3, propane can be eliminated
during the thermolysis.[61
We have now tried to replace the substituents X in 3 by
phosphorus ylides in order to obtain cationic complexes,
which, with the exception of the CH,-bridges, contain only
onium-stabilized Au-C bonds. In the thermolysis of mononuclear cationic Au"' complexes the non-ylidic Au-C
bonds proved to be the more labile centers [Eq. (a)].[']
-% [Au(CH2PR3),J@+ Rz
97 001
The reactions of 3a ( R = M e , X = I ) and 3b ( R = P h ,
X = Br) with MePh2P=CH2['] and Me3P=CHl9] smoothly
afforded the products of double substitution 5a and 5b,
respectively, in good yields. With reaction partners in the
stoichiometric ratio 1 : 1, formation of the intermediates 4a
and 4b, respectively, is also observed.["]
99 0°1
98 00'
I \
3a. b
-$ --
v imm/sl-
12 0
Fig. 1. '97Au-Mossbaucr apcctra 01 5a ({up)mid 5b (huiiurii) ill 4 h ( I = rclrltive transmission, u= relative rate). 5a : IS =4.04 mm/s, QS = 7.72 mrn/s. 5b :
IS=4.10 mm/s, QS=7.73 mm/s.
I \
The constitutional isomerism of the complex cations of
Sa, b is recognizable in the field desorption mass spectra.
In the case of 5a, not only the dication (m/z 508) is observable, but also the monocation (m/z 1141) associated with
an iodide ion. Observation of the unexpected cation
[Me3PCH2AuCH2PMe3]@demonstrates the ready formation and stability of these cations, which are also formed
according to equation (a). The mass spectra of 5a, b also
contain the signals of the cations of the heterocycles 1
( R = Me and Ph, respectively). The IR spectra of 5a, b d o
not show any typical bands for Au-X vibrations.
40, b
* CH,
I '
a , R = M e , R' = P h ,
R ,P=CH2
X = l
b , R = P h . R' = M e ,
5a, b are colorless, air stable salts which are soluble in
chloroform and methanol, but insoluble in diethyl ether,
toluene, and pentane. Since the structures of 1-3 were already k n ~ w n , [ ~the
. ~ 'constitution of 5a, b could easily be
deduced from the analytical and spectroscopic data: The
signals of the high resolution 'H-, I3C-, and 3'P-NMR
spectra can be unequivocally assigned to the individual
structural units["1 and are consistent with a C2, symmetry
for the cations in solution (mirror planes through P*CHZP
and Au*CAu). An essentially rigid boat conformation can
be assumed for the eight-membered ring.[4.51This and the
location of the *CH2 bridge on one side of the eight-membered ring give rise to a non-equivalence of the H-atoms
(A2A;B2B;XX' system) and substituents R on the eightmembered ring (A3B3X system when R=CH3). In contrast
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5a. b
6 0 , R = Me, R' = P h
6 b , R = P h , R' = Me
The corresponding ylides 6a, b can be generated from
the salts 5a, b by reaction with strong bases under mild
conditions. In solution the ylides are yellow, have different
3'P-NMR spectra, and can be reconverted into the salts by
treatment with hydrogen haloacids. A rearrangement of
the cation of 5a into that of 5b via an ylidic intermediate,
with the terminal ylide taking up the bridge position and
vice versa, could not be detected.
0570-0833/86/0606-0576 $ 02.50/0
Received: January 24, 1986;
supplemented: March 14, 1986 [Z 1639 IE]
German version: Angew. Chem. 98 (1986) 573
Angew. Chem. In,. Ed. Engl. 25 (1986) No. 6
CAS Registry numbers:
3a, 80387-83-3; 3b, 90742-64-6; 4% 102234.12-8; 4b, 102234-13-9; Sa, 10226073-1 : Sb, 102260-74-2; MePh2P=CH2, 4554-22-7; Me3P=CH2, 14580-91-7.
[I] H. Schmidbaur, Angew. Chem. 95 (1983) 980; Angew. Chem. Int. Ed.
Engl. 22 (1983) 907.
121 H. Schmidbaur in Gmelin Hundbuch der Anorganischen Chemie. Orgunogold Compounds, Springer, Berlin 1980, p. 263.
[3] H. Schmidbaur, lnorg. Synth. 18 (1980) 136.
[4] a) H. Schmidbaur, R. Franke, Inorg. Chim.Acra 13 (1975) 84; b) P. Jandik, U. Schubert, H. Schmidbaur, Angew. Chem. 94 (1982) 74; Angew.
Chem In1 Ed. Engl. 21 (1982) 73; Angew. Chem. Suppl. 1982, 1; c) H.
Schmidbdur, P. Jandik, Inorg. Chim. Acra 74 (1983) 97.
[5] H. H. Murray 111, J. P. Fackler, Jr., D. A. Tocher, J. Chem. SOC.Chem.
Commun. 1985, 1278; H. H. Murray 111, J. P. Fackler, Jr., A. M. Mazany, Orgunometullics 3 (1984) 1310.
[6] H. Schmidbaur, C. Hartmann, J. Riede, B. Huber, G. Miiller, Organometullics, in press.
171 H. Schmidbaur, R. Franke, Inorg. Chim. Acra 13 (1975) 79.
[8] H. Schmidbaur, M. Heimann, Z . Nufurforsch. B2Y (1974) 485.
191 H. Schmidbaur, W. Tronich, Chem. Ber. 101 (1968) 595.
[lo] Procedure: When the reaction is carried out in tetrahydrofuran with the
reactants in the molar ratio 1 :2, the salts Sa, b separate out as colorless
precipitates, which after washing with benzene and drying in vacuo are
analytically pure. The yields are almost quantitative. Sa: m.p. 158162°C (decomp.); Sb: m.p. 187-192°C (decomp.). The intermediates 4
can be characterized "P-NMR spectroscopically (CDC13/CD30D). 4a :
[ I I] 58 (CDC13/CD30D): "P-NMR: 6=37.1, 27.0 (each s ; 1 :I). 'H-NMR:
6 ~ 0 . 6 6 ( N = 13.0 Hz; AuCH2P(ring)), 1.07 (s; *CH2), 1.42 (d,
'J(PH)= 16 Hz; AuCHZPPh2Me),1.25, 1.45 (each d, 2J(PH)= 12.1 and
12.8 Hz: P(CH&), 2.00 (d, 'J(PH)= 13 Hz; PPh,CH3), 7.15-7.50 (m;
C6H5). "C-NMR: 6=9.8 (d, 'J(PC)=33 Hz; CH2PPh,Me), 10.6 (d,
'J(PC)=62.3 Hz; AuCH2P(ring)), 12.9, 18.9 (N=50.4 and 46.7 Hz;
P(CH,)2), 13.6 (d, 'J(PC)=64.2 Hz; PPh2CH,), 38.2 (br. s; *CH2), 126.1,
128.7, 131.5 and 132.6 ( 5 ~ 8 1 . 6 , 11.9, 10.1 and 2.8 Hz; C6Hs).-Sb
(CDCII/CD30D): "P-NMR: 6=41.1, 27.0 (each s ; 1 :I). 'H-NMR:
6=0.66 (d, *J(PH)= 15.4 Hz; CH2PMe3), 1.42 (s; *C:H2), 1.57 (d,
2J(PH)= 13.2 Hz; P(CH3),), 1.78 ( N = 13 Hz; AuCH2P(ring)), 7.0-7.5
(m; C,H,) "C-NMR: 6 = 10.5 (N=48.2 Hz; AuCH,P(ring)), 13.6 (d,
'J(PC)= 55.5 Hz: P(CH3),), 14.3 (d, 'J(PC)=36.0 Hz; CH2PMe3), 38.9
(br. s ; *CH2), 134.9-123.7 (C6H5) (Nzaverage coupling constant).
1121 H. Schmidbaur, J . R. Mandl, F. E. Wagner, D. F. van de Vondel, G . P.
van der Kelen, J. Chem. SOC.Chem. Commun. 1976, 170: see also 161.
Secondary Deuterium Kinetic Isotope Effects
in Enantioselective Hydroborations with
( )-Diisopinocampheylborane** .
By Brian E. Mann, Peter W. Cutts, James McKenna.*
Jean M . McKenna, and Catriona M . Spencer
High degrees of regio- and/or stereo-selectivity in organic reactions are often achieved through the effect of
differential strong non-bonded interactions in competitive
transition states, where the geometrical arrangements of
reacting bonds are controlled by stereoelectronic factors.
The non-bonded interactions typically involve hydrogen
atoms in alkyl or other groups. In such cases highly selective reactions would be expected to exhibit large inverse
secondary hydrogen kinetic isotope effects associated with
isotopic replacement at the compressed hydrogen atoms. A
method for precisely locating the positions of important
compressive interactions is therefore available, and we
have successfully applied this method to investigate the
relevant transition-state characteristics for enantioselective
hydroborations of alkenes using (+ )-diisopinocampheylborane, 1, prepared from (-)-a-pinene.
Dr. J. McKenna, Dr. B. E. Mann, Dr. P. W. Cutts, Dr. J. M. McKenna,
Dr. C. M. Spencer
Chemistry Department, The University
Sheffield S3 7 H F (England)
[**I This work was supported by the Science and Engineering Research
Angew Chem. Int. Ed. Engl. 25 (1986) No. 6
_ _
Various detailed models, qualitative a I (more
quantitative have been suggested"] for this interesting reaction, which gives high enantioselectivity notably with simple acyclic non-terminal (a-alkenes, and which may be regarded as perhaps the most important early example[21of
the range of highly enantioselective reactions of great current interest in preparative organic chemistry. In every
model, strong steric interactions between alkyl or other
groups in the alkene and in the hydroborating reagent are
envisaged, which serve to differentiate the free energies of
competitive diastereoisomeric transition states. We now
wish to report new and significant experimental evidence
with which any satisfactory detailed model must accord.
The deuteriated (2)-alkenes 2 through 5 were synthesized, hydroborated at - 10°C in diglyme with 1 , and subsequently oxidized with aqueous Na202 at 25-40°C. The
resultant reaction mixtures were analyzed by 'H-NMR
spectroscopy in presence of the lanthanoid shift reagent13]
Eu(fodh to estkpate iQ each case the relative proportions
of structurally isomeric secondary alcohols. (Example: 6a
and 6b were formed from 2.) The enantiomeric purity of
the isomers was not measured. The product ratios are
equated to the competitive rate constant ratios, k D / k H ,
where k , and k , are defined as the overall rate constants
for the attachment of the B-atom of 1 to the particular alkene C-atoms indicated by the arrows in the structural formulas. For substrates 2 through 5 we evaluate the kinetic
isotope effects k D / k H as follows: 2, 1.00+0.17; 3,
2.86f0.24; 4, 1.45-tO.16; and 5 , 1.41 +0.35. Precision limits quoted are standard deviations.
Hydroborations of simple acyclic non-terminal ( a - a l kenes with 1 are independently
to be highly (up
to 98%) enantioselective, so our results for 2 and 3, and,
by extrapolation for 4 and 5 , may be interpreted in terms
of the characteristics of transition states leading to the expectedl4I preferred enantiomers. Two important conclu-
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dinuclear, methylene, bridge, bridging, gold, terminal, complexes, ylide, iii, ligand
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