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Coupling of an Iridium Vinylidene Complex with Aluminum Alkyls; Carbon-Carbon Bond Formation via Migratory Insertion of a Vinylidene Unit.

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oxirane, there is strong evidence that the inertial plane ac
of the complex coincides with a vertical symmetry plane (bc)
of oxirane, that the HCI subunit lies in this plane, and that
the geometry of oxirane is not significantly changed on complex formation. Conversely, the other symmetry plane (ab)
of oxirane has not been preserved, for otherwise A , for
the complex would be essentially identical with Bo =
22120.77 MHz for free oxirane. [61 The most likely arrangement of the two subunits consistent with these conclusions is
as illustrated in 1 (X = CI), with HCI forming a hydrogen
bond to 0 in oxirane. Detailed isotopic substitution is necessary to establish this conclusion rigorously and is in progress.
Assuming a linear hydrogen bond 0 . . H-CI, an unchanged r,-geometry of oxiraneL6]and an unchanged r,-distance
in hydrogen chloride, the geometry of 1 (X = CI) is defined
by the angle 4 and the distance r ( 0 . . . Cl). A least squares
fit of A , , B, and Co then leads to 4 = 77.08(2)O and
r ( 0 . CI) = 3.1 12(3) A. We note that 4 is consistent with
some simple rules recently proposed 181 for the rationalization of angular geometries of hydrogen-bonded complexes.
These suggest that at equilibrium the HCl subunit should lie
along the axis of a nonbonding electron pair on the acceptor
atom. Given that the angle between the nonbonding pairs, as
conventionally pictured, on oxygen in dimethyl ether is
2 x 54.5", we expect the corresponding angle in oxirane to
increase as the angle COC decreases. Hence, the rules predict
that 4 should be greater than 54.5", as observed.
A property of 1 (X = CI) of importance in connection with
the mechanism of the gas-phase ring opening reaction is the
position of the H atom in the HCI subunit. Is 1 (X=Cl) a
reactive intermediate in the sense that there is already incipient proton transfer to 0 and a concomitant weakening of
the HCl bond? Qualitatively, a contribution =OH . . . CI to
the valence bond description of 1 can be detected from the
magnitude of the 35CI-nuclearquadrupole coupling constant
along the direction z of the HC1 subunit in the complex. For
this structure, x,, is expected to be similar in magnitude to
the value - 5.643(4) MHz observed"] for the vapor-phase
111 G. Bellucci, G. Berti, R. Bianchini, G. Ingrosso, A. Moroni, J Chem. Soc.
Prrkin Truns. 2 1981, 1336.
[2] G. Alagona, E. Scrocco, J. Tomasi. Theor. Chim. Actu 51 (1979) 11
[3] A. C . Legon, Annu. Rev. Phys. Chem. 34 (1983) 275.
[4] T. D. Klots, T. Emilsson, H. S. Gutowsky, Symp. Mol. Slrucr. Sprctrmc.
Ohio, USA f988, Abstract TF2.
[5] R. G. Azrak, E. B. Wilson, J Chem. Phys. 52 (1970) 5299.
[6] C. Hirose, Bull. Chem. SOC.Jpn 47(1974) 976. 1311.
[7] For H35CI, ro = 1.28387 8, is obtained from B, given by F. C. De Lucia,
P. Helminger, W. Gordy, Phys. Rev. A 3 (1971) 1971.
[8] A. C. Legon, D. J. Millen, Chem. Soc. Rev. 16 (1987) 467.
[9] F. H. de Leeuw, R. van Wachem, A. Dymanus, Symp. Mol. Struct. Spectrosc. Ohio, USA 1969, Abstract RS.
[lo] E. W. Kaiser, J Chem. Phyx 53 (1970) 1686.
[11] A. C. Legon, D. J. Millen. Proc. R. Soc. London A 417 (198X) 21
[I21 A. C. Legon, L. C. Willoughby, Chem. Phi,.\. Lerr. 95 (1983) 449.
Coupling of an Iridium Vinylidene Complex with
Aluminum Alkyls; Carbon-Carbon Bond Formation
via Migratory Insertion of a Vinylidene Unit
By Michael D. Fryzuk,* Neil 7: McManus, Steven J Rettig,
and Graham S . White
Very reactive organic fragments can be stabilized by coordination to metal complexes.['] These include, inter aha, carbenes,"] ben~ynes,'~]cycl~butadienes,[~]
and thiocarb ~ n y l s . [Vinylidenes
(:C = CHR) are tautomers of terminal
acetylenes and have only short lifetimes at normal temperatures; [61however, they can also be stabilized by coordination
to a metal complex. Indeed, much has been reported on the
formation of vinylidene-metal complexes and the reactivity
of the coordinated vinylidene unit.['] Depending on the L,M
fragment the a-C atom can be attacked either nucleophilically or electrophilically (cf. A, B).[*I
ion pair NaCI. In the free CIo ion, x is necessarily zero.
The zero-point average value x,, = - 53.6 MHz is readily
obtained by diagonalization of the complete CI-nuclear
quadrupole coupling tensor in the principal inertial axis
system given in Table 1. Although x,, is greatly reduced in
magnitude from 1, = -67.62 MHz in the free HCI molecule,["] the reduction does not arise from a significant ionic
contribution. The z-component of the electric field gradient
at the C1 nucleus due to the oxirane subunit and the zeropoint oscillation of the HCI subunit both also act to reduce
x,,. In the related, effectively planar complex H,O. . .H35C1,
for which there is no evidence of ionic character," these
,, from -67.62 MHz
two factors decrease the value of I
to - 53.4 MHz."'] If we assume that the two factors have
a broadly similar effect in 1 (X = C1) to that in H,O . . . HCI,
we thus find it unnecessary to invoke an ionic contribution
;OH. . . CI. A larger ionic contribution might be expected
in 1 when X = Br, because of the weaker HBr bond, or when
the oxirane is replaced by the stronger base aziridine. We are
examining both of these systems experimentally.
Received: July 24, 1989,
revised: September 15, 1989 [Z 3461 IE]
German version: Angtw. Chrm. 102 (1990) 76
CAS Registry numbers:
HCI, 7647010; oxirane, 75218
Anxrir. Chrm. In!. Ed. EngI. 29 (1990) N o . I
L,M =C = C
C =C
Herein we document a new mode of reactivity for a vinylidene ligand that involves carbon-carbon bond formation via
coupling with an organoaluminum reagent. The key feature
in this type of reactivity is that the metal center is coordinatively unsaturated and this promotes migratory insertions
with electrophiles.
The red-orange vinylideneiridium complex 3 was prepared
by addition of acetylene to the cyclooctene derivative 11'1 by
way of the transient q'-acetylene adduct 2. Although this
adduct was only spectroscopically characterized, its identity
is unmistakable.['01 The transformation of 2 into the vinylidene complex 3 occurs without observation of any intermediates (by 'H-NMR spectroscopy) over a period of 24 h
in benzene or toluene. Diagnostic of the vinylidene complex is the presence of an upfield triplet at 6 = - 3.53
Prof. Dr. M. D. Fryzuk, Dr. N. T. McManus. Dr. S. J. Rettig.[ '1
Dr. G. S. White
Department of Chemistry, University of British Columbia
2036 Main Mall, Vancouver. B. C., V6T 1Y6 (Canada)
['I X-ray structure analysis, UBC Crystallographic Service.
[**I This work was funded by the NSERC (Canada) in the form of an operating
grant to M.D.F and a Postdoctoral Fellowship to G.S. W. We also thank
Johnson-Matthey for the generous loan of IrCI, - x H,O.
6.3 VCH Verlugsgesrllschuf!mbH, 0-6940 Weinheim, 1990
(4Jp,= 3.5 Hz),"'] in accord with other related vinylideneiridium complexes.[' 21
Addition of trimethyl- o r triethylaluminum to a solution
of 3 in toluene results in the loss of the red color and formation of yellow-orange solutions containing a single product
(3'P { 'H)-NMR spectroscopy); crystallization from toluene/
hexane affords the new complexes 4a, b[j3] in 70-80% yield
(Scheme I ) .
4a R = M e
4 b R-Et
Scheme 1.
The 'H-NMR spectrum of 4a is very straightforward but
structurally ambiguous; resonances are observed that indicate that the AIMe, reagent has transferred a methyl group
to the vinylidene moiety to generate an isopropenyl ligand
and that the AIMe, unit is still bound in some way to the
complex. Similar results were obtained with AIEt,, leading
to 4b." To ascertain the mode of binding of the AlMe, unit
to iridium, we carried out an X-ray crystal structure analysis
of 4a (Figure 1).[l4l
The aluminum-iridium complex 4a has a distored squarepyramidal geometry with the isopropenyl ligand in the equa-
Fig. l . Crystal structure of 4a. Important bond lengths [A] and bond angles [ I :
Ir-Pl, 2.272(2); Ir-P2, 2.294(2); Ir-N, 2.373(5), Ir-Al, 2.41112); Ir-C31,
2.014(6); C31GC33, 1.348(9); C31-32. l.SOS(8); AI-N, 1.970(5); AI-C34,
1.961(7);AI-C35, 1.97918); Ir"'H32.2.68; PI-Ir-P2. 161.86(5); Ir-C31-C32,
115.8(4); Ir-C31-C33. 125.8(5); C32-C31-C33, 118.4(6); lr-Al-N, 64.7(1):
N-Ir- A1 48.6(1); Ir-N-Al. 66.7(1); Sil-N--SiZ, 119 8(3); C31-Ir-N, 168.8(2).
VCH firlagsgesellschqfi mbH, 0-6940 Weinheim, 1990
torial plane and an AIMe, group apical but bent, bridging
over to the nitrogen atom of the iridium amide. The Ir-A1
bond length of 2.41 1(2) A is slightly shorter than the Rh-A1
distance of 2.4581(8) A in [CpRh(PMe,),(AI,Me,Cl,)].~' '1
The distances in the Ir-N-A1 triangle are informative; the
Tr-N bond length is 2.373(5)A and the AI-N distance is
1.970(5)A, indicative of metal-amine['61 iengths typical for
an amide ligand bridging two metals. The nitrogen has a
distorted tetrahedral geometry. Also of interest in the solid
state structure is the presence of an agostic C-H . . . Ir interaction from an ortho hydrogen of one of the phenyl rings to
the open site of the square-based pyramid; the Ir-H(32)
bond length is 2.68 A.
The formation of the complexes 4a, b probably involves
oxidative addition['" of the AIR, monomer to the 16-electron 1r'-complex 3 to generate a transient species 5 having an
AIR, ligand, an alkyl ligand and the vinylidene ligand (cf.
Scheme 1). Migration of the vinylidene ligand to the Me-Ir
bond generates the isopropenyl unit; the proximity of the
amide N-atom to the Al-atom undoubtedly facilitates formation of the amide bridge.
For the most part, the reactivity of the coordinated vinylidene fragment has been investigated on systems that are
coordinatively saturated at the metal center. While this has
allowed a number of new reactivity patterns to be unveiled,
systems having unsaturation at the metal site should allow
new reaction types to be found. An especially good example
of this involves protonation via the metal center to convert
a vinylidene unit into a carbyne ligand.['*]
Our particular tridentate ligand combination has allowed
for the isolation of an iridium-aluminum adduct with carbon-carbon bond formation. Further work is underway in
our laboratory to exploit the migratory insertion capability
of both a vinylidene fragment and a methylidene unit['']
coordinated to an unsaturated metal center.
Received- July 10, 1989 [Z 3428 IE]
German version: Angen. Chem. fU2 (1990) 67
CAS Registry numbers:
1,84074-30-6;2,124462-68-6; 3,124462-69-7,4a, 324462-70-0:4b, 124462.711 ; AlMe,. 75-24-1 ; AlEt,, 97-93-8.
[l] J. P. Collman. L. S. Hegedus, J. R. Norton. R. G . Finke: Principles and
Applicafions of Organofransition Metal Chemisrry, University Science
Books, Mill Valley. CA, 1987, p. 58.
[2] K. H. Dotz, H. Fischer. P. Hofmann, F. R. Kreissl, U. Schubert, K. Weiss,
Tran.rifionMetal Curbene Complexes. Verlag Chemie, Weinheim 1983.
[3] S . L. Buchwald, R. B. Neilsen, Chem. Rev. 88 (1988) 1047; M. A. Bennett,
H.Schwemlein, Angen. Chem. iO(1989) 1349, Angeiv. Chem. Int. Ed. Engl.
28 (1989) 1296.
[4] A Efraty. Ckem. Rev. 77 (1977) 691.
[S] a) 1. M. Butler. Ace. Chem. Res. 10 (1977) 359: b) P. V. Yaneff. Coord.
Chem. Rev. 23 (1977) 183.
[6] R P. Duran, V. T. Amorebieta, A. J. Colussi. J Am Chem. Soc. 109 (1987)
3 154.
[7] a) M. I. Bruce. A. G . Swincer, Adv Organomrr. Chem. 22 (1983) 59; b)
R. S . Iyer, J. P. Selegue, J Am. Chem. Sor. 109 (1987) 910; c) A. Mayr.
K C. Schaefer. E. Y. Huang, ibid. I06 (1984) 1517; d) K. R. Birdwhistell.
T L. Tonker. J. L. Templeton, ibid. 107 (1985) 4474; e) S . J. Landon. P. M.
Shulman. G. L. Geoffroy, ibid 107 (1985) 6739; f) B. E. Boland-Lussier.
M. R. Churchill, R. P. Hughes, A. L. Rheingold, Organomefallicsi(1982)
628; g) G Consiglio. F. Morandini, G . F Ciani, A. Sironi, ihid. 5 (1986)
1977; h) R. G. Beevor, M. J. Freeman. M. Green, C. E. Morton, A. G.
Orpen, J Chrm. Soc. Ckem. Commun. 1985. 68: i) G. Consiglio, R.
Schwab, F. Morandini, ihid. 1988. 25.
181 a ) D. R. Senn. A. Wong, A. T. Patton, M Marsi, C. E. Strouse, J. A.
Gladysz, J Am. Cheni. Soc. 110 (1988) 6096; b) A. Davison, J. P. Selegue.
;bid 102 (1980)2455: c) H. Werner, J. Wolf, R. Zolk, U. Schubert, A n g e w
Chem. 95 (1983) 1022; Angew. Chrm. lnr. Ed. Engl. 22 (1983) 981: d) J.
Wolf. R. Zolk. U. Schubert. H. Werner. J. Orgunomer. Chum. 340 (1988)
191 M. D. Fryzuk, P. A. MacNeil, S. J. Rettig, Organome/ul/irs4 (1986) 2469.
0570-0833!90!0101-0074 S 02.5010
Angels. Chem. Inr.
Ed. Engl. 29 11990j No. I
1101 2 . ' H NMR(300MHz.C6D,):d =0.03(s;SiCH3),1.70(vt,N= 5.4Hz;
PCH,). 2.40 (s: C,H,), 7.08 (m; p/m-H), 7.70 (m; o--H). "P{'H}-NMR
(121.4 MH7,C,Da):6 = 11.9(sj. IR(KBr): f = 1958 cm-' [v(C=C)];see
El. Werner, A. Hohn. J. Organumer Chem. 272 (1984) 105.
1111 3. ' H N M R (300 MHz. C,D,): 6 = - 3.53 (t. 4J(PH) = 3.5 Hz; =CH,).
0.16 (s; SiCH,), 1.90 (vt; N = 5.3 Hz; PCH,), 7.08 (m;p/m-H), 7.94 (m;
0-H). " P / ' H ) - N M R (121.4 MHz, C,D,): 6 = 15.8 (s). " C N M R
(75.4 MHz. C,D,): d = 91.6 ( s ; 0-C), 268.1 (t, 'J(PC) = 7.0 Hz; z-C). IR
(KBr): i;= 1648cm-' (v(C=C)]. Correct C, H. N analysis.
1121 a ) A. Hohn. H Otto, M. Dziallas, H. Werner, J. Chem. Sor Chem. Cumm u n . IYH7. 852: b) F J. Garcia Alonso, A. Hohn, J. Wolf, H. Otto, H.
Werner. Angew. Cltem. 97 (1985) 401. Angen-. Chem. In/. Ed. EngI. 24
(1985) 406; c) H. Werner, J. Wolf, G . Muller, C . Kruger, ihid. 96 (1984) 421
and -73 (1984) 431; d ) J. Orgunumer. Chem. 342 (1988) 381.
[13] 4a. ' H NMR (300 MHz, C,D,): 0.07 (s; StCH,), 0.50 (s; AICH,), 1.91
= 14.3, N = 5.2 Hz) and 2.53 (dvt, N = 5.3 Hz; PCH,), 4.77 and
(dvt. JgZm
6.01 (s; =CH2), 7.20(m;p/m-H). 7.92andX.O3(m;@H). "P('H}-NMR
( 1 I I .4 MHz. C,D,): 6 = 18.0 (s). IR(KBr): v^ = 1590 cm- I [v(C=C)]. 4b:
' H NMR (300 MHz, C,D,): 6 = 0.06 and 0.48 (s, Si(CH,),), 1.88 (dvt.
.JKcn,= 14.4. N = 5.1 Hz) and 2.53 (dvt, N = 5.3 Hz; PCH,), 0.61 (m;
AICII,CH,). 1.46 (t, J = 8.1 Hz), AICH,CH,), 2.19 (4, J = 7.4 Hz;
CH,CH,). 0.98 (t, J = 7.4 Hz; CH,CH,), 4.84 and 5.96 (br.s; =CH,),
7.1X (m: p:fn-H). 7.85 and 7.98 (m; o-H). " P i ' H i - N M R (121.4MHz.
C,,D6): b = 17.7(s). I R ( K B r ) . J = 1586cm-'Iv(C=Cj].CorrectC,H,N
[14] C35H4,AllrNPzSi2, M, = 819.08. monoclinic (from toluene/hexane).
Z = 4,
n = 18.823(6)&
b = 9.701(2)&
space group
< = 21.359(8)A, fi = 111 78(2)-, Y = 3622(2)A3, e,,,, = 1.5Og c m - 3 ,
~ ( M O ~=, 38.73
cm-', F(000) = 1648. 8600 measured reflections
(RigdkuAFC6.MoK,,E.= 0.71069A).T = 21 "C,w -2@scan,maximum
2 8 = 55.1 : 8352 independent reflections, empirical absorption correction,
heavy atom method, Lorentz and polarization corrections, R = 0.034,
K , = 0.040 (w. = l/u*(&)) for 5723 observed reflections ( I > 3.00u(fj)
and 379 parameters, residual electron density (max.) = 1.85 e k ' . Further details of the crystal structure analysis may be obtained from the
Fachinformationszentrum Karlsruhe. Gesellschaft fur wissenschaftlichtechnischr Information mbH, D-7514 Eggenstein-Leopoldshafen 2
(FRC;). by quoting the depository number CSD-54150, the names of the
authors. and the journal citation.
[15] J. M. Mayer. J. C. Calabrese, Organume/u/ics 3 (1984) 1292.
1161 For related iridium-amine bond lengths, see M. D. Fryzuk. P. A. MacNeil. S. J. Rettig. J. Am. Chrrn. Sur. 109 (1987) 2803; for typical aluminum nitrogen bond lengths, see M. J. Zaworotko, J. L. Atwood, Inorg.
( ' h r w i . 19 (1980) 268.
(171 a ) D. L. Thorn, R. L. Harlow, J. Am. Chem. Sot.. 111 (1989) 2575; b) K
Isobc. A. Vazquez de Miguel. A. Nutton, P. M. Maitlis, J Chem. Suit
Dulron Truns. IYN4, 929.
[I81 A . Hiihn. H. Werner, Angen,. Chem. 98(1986) 745; Angew. Chem. Int. Ed
Enfil. 25 (1986) 737.
[19] M. D Fryzuk. P. A . MacNeil, S. 1. Rettig, J. Am. Chem. Sue. 107 (1985)
cycles containing a group 15 (5th main group) element are
rare.14. In the course of our search for organometallic
routes to main group heterocycles, we have discovered that
the bis(cyclopentadieny1)titanacyclobutene 1 reacts rapidly
and cleanly with group 15 aryl dichlorides to yield the corresponding heterocyclobutenes, 2 and 3. Herein, we report the
synthesis, and characterization of 2 the first arsacyclobutene
(1,2-dihydroarsete); comparisons with the P analog 3 will be
The addition of one equivalent of PhAsC1, or PhPCI, to
bis(cyclopentadieny1)titanacyclobutene 1 [61 in hydrocarbon
solvents results in the immediate precipitation of titanocene
dichloride and formation of 2 or 3,[71respectively (essentially
quantitative by NMR spectroscopy).[*]2 and 3 were isolated
in greater than 50% yield as colorless crystals by filtration of
the titanocene dichloride byproduct, removal of solvent, and
recrystallization from cold ( - 20 "C) ether or pentane.
NMRc9]and high resolution mass spectral dataI"1 are consistent with a four-membered ring structure for 2 and 3. The
diastereotopic a-methylene hydrogens appear as doublets
(J = 13.3 Hz) at 6 = 2.75 and 2.35 in the 'H-NMR spectrum
of 2. The lJPcof 33.9 Hz for the ips0 phenyl carbon of 3 (I3C
NMR) is consistent with reported values for phosphetanes.
' J C Hat the a positions of 140-146 Hz (I3C NMR) of 2 and
3 are also indicative of a cyclic structure.["]
The proposed arsacyclobutene structure 2 was confirmed
by X-ray crystallography (Fig. 1)."*1 The four-membered
Application of Titanacycles to Heterocycle
Synthesis: Phospha- and Arsacyclobutenes **
By William Turnas,* Joseph A . Suriano, and
Richurti L. Harlow
Dedicated 10 Dr. George Parshall on the occasion of his
60th hirthdq.
The propensity of early transition metal alkyls to undergo
transmetalation reactions with main group halidesL'] coupled with the wealth of metallacyclic complexes now available['] should provide access to novel heterocycles that heretofore have been difficult to prepare. Except for the widely
studied ph~sphetanes,'~]
examples of four-membered carbo-
Di-. W. Tumas. J. A. Suriano, Dr. R. L. Harlow
Central Research and Development Department
E.I. du Pont de Nemours and Co.
Experimental Station. Wilmington, D E 19880 (USA)
[**I Contribution No. 5275 from the Central Research and Development Department. We thank E Duvidsun for the "C N M R spectra, J. Lazar for
high-resolution mass spectra data, and W. Marsha// for assistance with the
X-ray crystallography.
Fig. I . Structure of 2 in the crystal. For bond lengths and angles see Table 1
ring is essentially planar with only a slight enveloping; the
atoms of the ring deviate from a mean plane by only 0.039,
- 0.052, 0.073, and - 0.059 A, for As, C1, C2, and C3,
respectively. Moreover, the As atom is clearly pyramidal
with C-As-C angles of 69.9, 102.3 and 101.7 '. For the sake
of comparison we also prepared and structurally characterized the isostructural phosphacyclobutene 3.". 31 Pertinent
bond lengths and angles for 2 and 3 as well as two previously
reported metalla~yclobutenes~'~~
are listed in Table 1. The
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alkyl, bond, complex, vinylidene, formation, couplings, insertion, migratoria, aluminum, unit, iridium, carbon, via
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