Directed formation of allene complexes upon reaction of non-heteroatom-substituted manganese alkynyl carbene complexes with nucleophiles

2078

Organometallics 2008, 27, 2078–2091

Directed Formation of Allene Complexes upon Reaction of

Non-heteroatom-Substituted Manganese Alkynyl Carbene

Complexes with Nucleophiles

Stéphane Sentets, Rémi Serres, Yannick Ortin,^†Noël Lugan,* and Guy Lavigne

Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne,

31077 Toulouse Cedex 4, France

ReceiVed January 23, 2008

The non-heteroatom-substituted alkynyl carbene Cp′(CO)₂MndC(Tol)CtCPh (1, Cp′ ≡ (η⁵-MeC₅H₄))

is ﬁrst shown to react at low temperature with lithium diorganophosphide LiPR₂(R ) Ph, Cy) to form

an anionic species. Subsequent treatment with CF₃SO₃H affords the η⁴-vinylketene complex Cp′(CO)₂Mn[η⁴-

{R₂P(Ph)CdCHC(Tol)dCdO}] (2; 2a: R ) Ph (70% yield), 2b: R ) Cy (55% yield)) as the major

compound, along with trace amounts of the η²-allene complex syn-Cp′(CO)₂Mn[η²-{Ph₂P(Tol)-

CdCdC(Ph)H}] (syn-3a) for R ) Ph, or along with the η²-allene complex Cp′(CO)₂Mn[η²-{H(Tol)-

CdCdC(Ph)PCy₂}] (4b, 26% yield, 1:2 mixture of syn/anti isomers) for R ) Cy. On the other hand,

subsequent treatment with NH₄Cl_aqaffords only η²-allene complexes, obtained either as a ca. 1:9 mixture

of syn-3a and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)PPh₂}] (4a) (75% yield) for R ) Ph or as a 1:2

mixture of syn- and anti-4b for R ) Cy (74% yield). Combined NMR and single-crystal X-ray diffraction

studies (for 2a, anti-4b, and syn-4b) revealed that both type 2 and type 4 species result from a nucleophilic

attack of the diorganophosphide onto the remote alkynyl carbon atom in 1 (C_γ), whereas type 3 species

results from a nucleophilic attack of the carbene carbon atom (C_R). Complexes 3a and 4a,b are prone to

undergo a thermal rearrangement to give the η¹-phosphinoallene complexes Cp′(CO)₂Mn[η¹-

{Ph₂P(Tol)CdCdC(Ph)H}] (5a) and Cp′(CO)₂Mn[η¹-{R₂P(Ph)CdCdC(Tol)H}] (6; 6a: R ) Ph, 6b: R

) Cy), respectively. Reaction of 1 with p-toluenethiol in the presence of NEt₃(20%) affords a 1.8:1

mixture of Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC(Ph)H}] (syn-11), resulting from a nucleophilic attack at

C_Rin 1, and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)STol}] (12), resulting from a nucleophilic attack at

C_γ, whereas treatment of 1 with lithium p-toluenethiolate at –80 °C followed by protonation with NH₄Cl_aq

gave the same syn-11 and 12 complexes now in a 1:2.3 ratio. Finally, 1 was found to react with

cyclohexanone lithium enolate to afford, upon protonation, the η²-allene complex Cp′(CO)₂Mn[η²-

{H(Tol)CdCdC(Ph)CH(CH₂)₄C(O)}] (syn-13), resulting from a nucleophilic attack at C_γin 1. The solid-

state structures of syn-11 and syn-13 are also reported.

useful and versatile subclass of carbene complexes having

explicit applications in organic synthesis.³Their reactivity is

dictated by the strong electron-withdrawing properties of the

metal fragment, enabling these species to undergo 1,2-, or 1,4-

nucleophilic addition reactions as well as cycloaddition reac-

tions. By contrast, little is known about the reactivity of their

non-heterotaom-substituted counterpart,⁴though recent ﬁndings

by Iwasawa et al.,⁵Casey et al.,⁶or Barluenga et al.⁷provide

Introduction

Since their discovery more than 40 years ago,¹Fischer-type

carbene complexes have been subject to intensive studies.²In

recent years, heteroatom-substituted alkynyl complexessof

chromium and tungsten in particularshave emerged as a very

* Corresponding author. E-mail: lugan@lcc-toulouse.fr.

^†Present address: NMR Centre, UCD School of Chemistry and Chemical

Biology, University College Dublin, Belﬁeld, Dublin 4, Ireland.

(1) Fischer, E. O.; Maasböl, A. Angew. Chem., Int. Ed. Engl. 1964, 3,

580.

(3) For reviews being more speciﬁc to applications of heteroatom-

substituted alkynyl carbene complexes to organic synthesis see: (a) De

Meijere, A.; Schriemer, H.; Duetsch, M. Angew. Chem., Int. Ed. 2000, 39,

3964. (b) Aumann, R. Eur. J. Org. Chem. 2000, 17. (c) Barluenga, J. Pure

Appl. Chem. 2002, 74, 1317. (d) Barluenga, J.; Fernández-Rodríguez, M. A.;

Aguilar, E. J. Organomet. Chem. 2005, 690, 539.

(2) For reviews on applications of Fischer-type carbene complexes to

organic synthesis see for instance: (a) Aumann, R.; Neinaber, H. AdV.

Organomet. Chem. 1997, 41, 163. (b) Wulff, W. D. ComprehensiVe

Organometallic Chemisry II; Abel, E. W., Stone, F. G. A., Wilkinson G.,

Eds.; Pergamon Press: Oxford, 1995; Vol. 12, Chapter 5.3. (c) Herndon,

J. W. Coord. Chem. ReV. 1999, 181, 177. (d) Zaragoza Dörwald, F. Metal

Carbenes in Organic Synthesis; Wiley-VCH: Weinheim, 1999. (e) Sierra,

M. A. Chem. ReV. 2000, 100, 3591. (f) Barluenga, J.; Frañanás, F. J.

Tetrahedron 2000, 56, 4597. (g) Herndon, J. W. Tetrahedron 2000, 56,

1257. (h) Dötz, K. H.; Minatti, A. Transition Metals for Organic Synthesis,

2nd ed.; 2004; Vol. 1, p 397. (i) Metal Carbenes in Organic Synthesis:

Topics in Organometallic Chemistry; Dötz, K. H., Ed.; Wiley: New York,

2004; Vol. 13. (j) Gómez-Gallego, M.; Mancheo, M. J.; Sierra, M. A. Acc.

Chem. Res. 2005, 38, 44. (k) Wu, Y.-T.; Kurahashi, T.; De Meijere, A. J.

Organomet. Chem. 2005, 690, 5900. (l) Herndon, J. W. Coord. Chem. ReV.

2006, 250, 1889. (m) Sierra, M. A.; Gómez-Gallego, M.; Martínez-Alvarez,

R. Chem.-Eur. J. 2007, 13, 736.

(4) For the synthesis of non-heteroatom-substituted alkynyl carbene

complexes, see for instance: (a) Terry, M. R.; Kelley, C.; Lugan, N.;

Geoffroy, G. L.; Haggerty, B. S.; Rheingold, A. L. Organometallics 1993,

12, 3607. (b) Weng, W.; Arif, J. A.; Gladysz, J. A. J. Am. Chem. Soc.

1993, 115, 3824. (c) Roth, G.; Fischer, H. Organometallics 1996, 15, 5766.

(d) Esteruelas, M. A.; Gomez, A. V.; Lopez, A. M.; Modrego, J.; Onate, E.

Organometallics 1997, 16, 5826. (e) Dovesi, S.; Solari, E.; Scopelliti, R.;

Floriani, C. Angew. Chem., Int. Ed. 1999, 38, 2388. (f) Casey, C. P.; Ktaft,

S.; Powell, D. R. J. Am. Chem. Soc. 2000, 122, 3771. (g) Bassetti, M.;

Marini, S.; Diaz, J.; Gamasa, M. P.; Gimeno, J.; Rodriguez-Alvarez, Y.;

Garcia-Granda, S. Organometallics 2002, 21, 4815.

(5) Iwasawa, N.; Maeyama, K.; Saitou, M. J. Am. Chem. Soc. 1997,

119, 1486.

10.1021/om800060v CCC: $40.75

2008 American Chemical Society

Publication on Web 04/09/2008

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2079

Scheme 1

a hint that research in this area may be equally rewarding in

terms of unique applications to organic synthesis.

We have recently shown that non-heteroatom-substituted

manganese alkynyl carbene complexes of the type Cp′-

(CO)₂MndC(Ar)CtCAr′ (Cp′ ≡ (η⁵-MeC₅H₄); Ar, Ar′ ) Ph

or Tol) are readily accessible upon reaction of simple alkynyl-

lithium reagents, LiCtCAr′, with the stable cationic carbyne

complexes [Cp′(CO)₂MntCAr][BPh₄] readily available on a

large scale from low-cost methylcyclopentadienyl manganese

tricarbonyl (MMT).^8,9Interestingly, subtle reactivity patterns

of these alkynyl carbene complexes were established in studies

of their interaction with various phosphorus probes.¹⁰In the

presence of PPh₃, just like their parent group 6 heteroatom-

substituted alkynyl carbene complexes¹¹or their rhenium

analogues,¹²they act as a Michael acceptors and are subject to

nucleophilic attack at the remote alkynyl carbon atom to afford

σ-allenylphosphonium complexes Cp′(CO)₂MnC(Ar)dCdC-

(PPh₃)Ar′. By contrast, in the presence of PMe₃, a more basic

and more nucleophilic phosphine, they behave as typical Fischer

carbene complexes and experience a nucleophilic attack at the

carbenic carbon to afford σ-propargylphosphonium complexes

Cp′(CO)₂MnC(Ar)(PMe₃)CtCAr′. An even more speciﬁc be-

havior is observed in the presence of secondary phosphines

HPR₂(R ) Ph, Cy). Indeed, as shown in Scheme 1, the alkynyl

carbene complex Cp′(CO)₂MndC(Tol)CtCPh (1)scomplex

taken as referencesreacts via two apparently competing path-

ways to afford mixtures of two regioisomeric η⁴-vinylketene

complexes, Cp′(CO)Mn[η⁴-{R₂P(Ph)CdCHC(Tol)dCdO}] (2)

and Cp′(CO)Mn[η⁴-{R₂P(Tol)CdCHC(Ph)dCdO}] (2′), and

an η²-allene complex, syn-Cp′(CO)₂Mn[η²-{R₂P(Ph)Cd

CdC(Tol)H}] (3).¹⁰The position of the PR₂group with respect

to the Tol/Ph substituents clearly indicates that the ﬁrst complex,

2, results from an initial nucleophilic attack of the secondary

phosphine onto the remote alkynyl carbon atom C_γ, whereas

the later two species, 2′ and 3, result from a nucleophilic attack

at the carbenic carbene center C_R. Parallel experiments carried

out with HPPh₂and HPCy₂suggest that the regioselectivity of

the attack is dictated by steric factors. Indeed, whereas the allene

complex 3a is obtained predominantly in the reaction of 1 with

HPPh₂, the η⁴-vinylketene complex 2b becomes predominant

when 1 is reacted with HPCy₂, thereby indicating that nucleo-

philic attack by the bulkier phosphine takes place preferentially

at the less hindered remote alkynyl carbon atom.

fragment.¹⁴As far as manganese carbene chemistry is concerned,

the observations summarized in Scheme 1 are quite gratifying

for two reasons. First, they reveal that manganese carbene

complexes are prone to develop a pronounced Fischer-type

carbene character provided they are not heteroatom-substituted.¹⁵

Second, it appears that the fate of the intermediate species

resulting from the initial nucleophilic attack differs signiﬁcantly

from what we know from group 6 congeners. Indeed, the

literature shows that group 6 alkynyl[alkoxy] carbene complexes

react with secondary phosphines to yield 2-phosphino alkenyl

carbenes resulting from typical conjugate addition of the P-H

bond across the CtC bond.^11,16The observation of a different

behavior of manganese complexes prompted us to investigate

further the reactivity of complex 1 toward nucleophiles, includ-

ing anionic nucleophiles, with the aim of establishing general

reactivity patterns, eventually offering new possibilities of

controlling the nature of the ﬁnal products. In the present paper,

we report our recent ﬁndings on the reactivity of the alkynyl-

carbene complex 1 toward a series of nucleophiles including

To date, manganese carbene complexes derived from MMT

have found much less applications to organic synthesis¹³than

their group 6 analogues, certainly because of the reduced

electrophilicity of their carbenic carbon atom inherent to the

relatively poor electron-withdrawing ability of the Cp′(CO)₂Mn

(13) For applications of group 7 carbene complexes to organic synthesis

see for instance: (a) Aumann, R.; Heinen, H. Chem. Ber 1988, 121, 1085.

(b) Aumann, R.; Heinen, H. Chem. Ber. 1989, 122, 77. (c) Hoye, T. R.;

Rehberg, G. M. Organometallics 1990, 9, 3014. (d) Balzer, B. L.; Cazanoue,

M.; Sabat, M.; Finn, M. G. Organometallics 1992, 11, 1759. (e) Balzer,

B. L.; Cazanoue, M.; Finn, M. G. J. Am. Chem. Soc. 1992, 114, 8735. (f)

Mongin, C.; Lugan, N.; Mathieu, R. Organometallics 1997, 16, 3873. (g)

Mongin, C.; Ortin, Y.; Lugan, N.; Mathieu, R. Eur. J. Inorg. Chem. 1999,

739. (h) Mongin, C.; Gruet, K.; Lugan, N.; Mathieu, R. Tetrahedron Lett.

2000, 41, 7341. (i) Casey, C. P.; Dzwiniel, T. L.; Kraft, S.; Kozee, M.; A.;

Powell, D. R. Inorg. Chim. Acta 2003, 345, 320. (j) Ortin, Y.; Sournia-

Saquet, A.; Lugan, N.; Mathieu, R. Chem. Commun. 2003, 1060. See also

ref 6.

(6) (a) Casey, C. P.; Dzwiniel, T. L.; Kraft, S.; Guzei, I. A. Organo-

metallics 2003, 22, 3915. (b) Casey, C. P.; Dzwiniel, T. L. Organometallics

2003, 22, 5285.

(7) (a) Barluenga, J.; Bernardo de la Rúa, R.; de Sáa, D.; Ballesteros,

A.; Tomás, M. Angew. Chem., Int. Ed. 2005, 44, 4981. (b) Barluenga, J.;

García-García, P.; de Sáa, D.; Fernández-Rodríguez, M. A.; Bernardo de

la Rúa, R.; Ballesteros, A.; Aguilar, E.; Tomás, M. Angew. Chem., Int. Ed.

2007, 46, 2610.

(8) Ortin, Y.; Coppel, Y.; Lugan, N.; Mathieu, R.; McGlinchey, M. J.

Chem. Commun. 2001, 1690.

(14) Dötz, K. H.; Böttcher, D.; Jendro, M. Inorg. Chim. Acta 1994, 222,

291.

(9) In a parallel work, Casey et al. have shown that the thermally stable,

yet air sensitive, anionic acyl complexes [CpMn(CO)₂C(O)R]Li · Et₂O may

constitute a viable alternative to cationic carbyne complexes as starting

materials for the preparation of non-heteroatom-substituted manganese

alkynyl carbene complexes; see ref 6b.

(15) (a) Manganese ethoxy carbene complexes do not react spontane-

ously with phosphines. Only under photolytic conditions does the substitu-

tion of a carbonyl ligand for the phosphine occur.^15b,c(b) Kelley, C.; Lugan,

N.; Terry, M. R.; Geoffroy, G. L.; Haggerty, B. S.; Rheingold, A. L. J. Am.

Chem. Soc. 1992, 114, 6735. (c) Fischer, H.; Schleu, J. Chem. Ber. 1996,

129, 385.

(10) Ortin, Y.; Lugan, N.; Mathieu, R. Dalton Trans. 2005, 1620.

(11) Aumann, R.; Jasper, B.; Läge, M.; Krebs, B. Chem. Ber. 1994,

127, 2475.

(16) (a) Llebaria, A.; Moretó, J. M.; Ricart, S.; Ros, J.; Viñas, J. M.;

Yáñez, R. J. Organomet. Chem. 1992, 440, 79. (b) Aumann, R.; Jasper,

B.; Fröhlich, R. Organometallics 1995, 14, 231. (c) Aumann, R.; Fröhlich,

R.; Prigge, J.; Meyer, O. Organometallics 1999, 18, 1369.

(12) Casey, C. P.; Kraft, S.; Powell, D. R.; Kavana, M. J. Organomet.

Chem. 2001, 617–618, 723.

2080 Organometallics, Vol. 27, No. 9, 2008

Sentets et al.

Scheme 2

(i) organophosphides, (ii) a thiol and its thiolate derivative, and

(iii) an enolate.

single-crystal X-ray diffraction analysis. An ORTEP drawing

of complex 2a is given in Figure 1. Relevant crystallographic

data are set out in Tables 1 and 3. The vinyl ketene ligand

backbone bound to the Cp (CO)₂Mn unit is comprised of the

O2, C2, and C3 atoms for the ketene part and C4 and C5 carbon

atoms for the vinyl part. The diphenylphosphide and phenyl

fragments are occupying adjacent positions on the carbon atom

C5 of the allene ligand moiety, thus conﬁrming that 2a results

from a nucleophilic attack of the diphenylphosphide at the

remote alkynyl carbon atom. Metrical features within complex

2a are naturally very similar to those of complex Cp′(CO)₂Mn-

[η⁴-{Ph₂P(Ph)CdCHC(Tol)dCdO}] described earlier.¹⁰

Subsequent Protonation with a Strong Acid, the Case

Where R ) Cy. IR monitoring allowed the observation of three

bands at 1975, 1960, and 1925 cm^-1, indicative that at least

two complexes were formed in that case. Chromatographic

workup effectively afforded two fractions, namely, a yellow one

Results and Discussion

PR₂^-/H⁺vs PR₂H: Sequential Treatment of the Alkynyl

Carbene Complex Cp′(CO) MndC(Tol)CtCPh (1) with a

2

Diorganophosphide LiPR₂(R ) Ph, Cy) and an Acid. The

alkynyl carbene complex Cp′(CO)₂MndC(Tol)CtCPh (1)

reacts instantaneously at –80 °C with lithium dicyclohexyl or

lithium diphenylphosphide. IR monitoring showed a strong

bathochromic shift of the ν_CObands of ca. –90 cm^-1(for the

leftmost bands), consistent with the formation of an anionic

complex. Intriguingly, the newly formed species exhibits three

bands in the ν_COregion, at 1873(s), 1798(m), and 1755(m) cm^-1

,

whereas only two are expected for a dicarbonyl Cp′(CO)₂ML

unit. This feature, which was also observed for the so-called

carbene anion [Cp′(CO)₂MndC(OEt)CΗ₂][Li],¹⁷is tentatively

ascribed to an interaction of lithium cations with the oxygen

atoms of the CO ligands.^18,19These intermediates evolve

instantaneously upon protonation at low temperature. Signiﬁ-

cantly, subsequent workup revealed that the nature of the

reaction products dramatically depends on the type of acid used.

Subsequent Protonation with a Strong Acid, the Case

Where R ) Ph. The stepwise treatment of 1 with diphe-

nylphosphide and CF₃SO₃H resulted in the formation of a new

species exhibiting a single ν_COband at 1960 cm^-1. More

precisely, chromatographic workup provided two compounds

readily identiﬁed as the η⁴-vinylketene complex Cp′(CO)₂Mn[η⁴-

{Ph₂P(Ph)CdCHC(Tol)dCdO}] (2a) and the η²-allene com-

plex syn-Cp′(CO)₂Mn[η²-{Ph₂P(Tol)CdCdC(Ph)H}] (syn-3a),

the latter existing as trace amounts only (Scheme 2). Complex

2a, which is accountable for the characteristic ν_COband observed

at 1960 cm^-1in the crude reaction mixture, was isolated in

72% yield. Both these complexes had already been obtained

upon reaction of 1 with HPPh₂, but in the ﬁrst instance, complex

syn-3a was the major reaction product (see Scheme 1).¹⁰In

addition, no trace of the previously identiﬁed regioisomer

Cp′(CO)₂Mn[η⁴-{Ph₂P(Tol)CdCHC(Ph)dCdO}] (2a′, Scheme

1) was detected in the present reaction.

Figure 1. Perspective view of complex Cp′(CO)₂Mn[η⁴-{Ph₂P-

(Ph)CdCHC(Tol)dCdO}] (2a). Thermal ellipsoids are drawn at

the 50% probability level.

Structure of Cp′(CO)₂Mn[η⁴-{Ph₂P(Ph)CdCHC(Tol)d

CdO}] (2a). The structure of 2a, which was hitherto inferred

only from NMR data,¹⁰has now been ﬁrmly established by a

Table 1. Bond Lengths (Å) and Angles (deg) for the Complex 2a

Mn1-C1

1.789(3)

1.927(3)

2.115(3)

2.100(3)

2.298(2)

O1-C1

O2-C2

C2-C3

C3-C4

C4-C5

1.145(4)

1.199(3)

1.453(4)

1.429(4)

1.394(4)

Mn1-C2

Mn1-C3

Mn1-C4

(17) Mongin, C. Thèse de l’Université Paul Sabatier, 1997.

(18) (a) Ulmer, S. W.; Skarstad, P. M.; Burlitch, J. M.; Hughes, R. E.

J. Am. Chem. Soc. 1973, 95, 4470. (b) York Darensbourg, M.; Burns, D.

Inorg. Chem. 1974, 13, 2970. (c) York Darensbourg, M.; Darensbourg, D. J.;

Burns, D.; Drew, D. A. J. Am. Chem. Soc. 1976, 98, 3127.

Mn1-C5

P1-C5

1.858(3)

C1-Mn1-C2

C1-Mn1-C3

C1-Mn1-C4

C2-Mn1-C3

C2-Mn1-C4

C5-P1-C41

C5-P1-C51

C41-P1-C51

Mn1-C1-O1

Mn1-C2-O2

77.30(13)

111.67(12)

114.25(12)

41.82(10)

75.42(10)

104.89(14)

103.47(12)

98.60(13)

173.5(3)

Mn1-C3-C21

C4-C3-C21

Mn1-C4-C3

Mn1-C4-C5

C3-C4-C5

Mn1-C5-P1

P1-C5-C4

130.17(18)

122.2(2)

70.75(14)

79.44(16)

123.3(2)

114.68(13)

123.17(19)

111.19(19)

121.2(2)

(19) (a) We have observed that addition of 1 molar equiv of 12-crown-4

ether, a speciﬁc trap for the lithium cation, causes a very signiﬁcant decrease

of the lower frequency band with concomitant enhancement of the band at

1798 cm^-1. On the other hand, when potassium diphenylphosphide is used

in place of lithium diphenylphosphide, the anionic species exhibits two bands

in the ν_COregion at 1873(s) and 1798(ms) cm^-1, very close in position to

those of the carbene anion [Cp′(CO)₂MndC(OEt)CH₂][K].^19b(b) Rabier,

A.; Lugan, N.; Mathieu, R.; Geoffroy, G. L. Organometallics 1994, 13,

4676.

P1-C5-C31

C4-C5-C31

145.8(2)

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2081

Table 2. Bond Lengths (Å) and Angles (deg) for the Complexes

followed by a brown one. The complex extracted from the

second band was readily identiﬁed as the η⁴-vinylketene

complex Cp′(CO)₂Mn[η⁴-{Cy₂P(Ph)CdCHC(Tol)dCdO}]

(2b) already encountered as the major product of the reaction

of 1 with HPCy₂(Scheme 1).¹⁰It was isolated in 55% yield as

a brown crystalline material. The regioisomeric complex 2b′

depicted in Scheme 1 was not observed under the present

conditions. The IR spectrum of the ﬁrst (yellow) fraction showed

two relatively sharp ν_CObands at 1978 and 1922 cm^-1, very

similar in position to those of type 3 complexes. NMR spectra,

however, clearly indicated that this fraction actually contains a

1:2 mixture of two stereoisomers of a new η²-allene complex,

namely, syn-Cp′(CO)₂Mn[η²-{HC(Tol)dCdC(Ph)PCy₂}] (syn-

4b) and anti-Cp′(CO)₂Mn[η²-{HC(Tol)dCdC(Ph)PCy₂}] (anti-

4b), which were obtained in 26% overall yield (Scheme 2). Both

isomers could be ultimately isolated in a pure form upon

fractional crystallization. They were fully characterized both by

usual spectroscopic techniques and by single-crystal X-ray

diffraction.

At 303 K, the ³¹P{¹H} NMR spectrum of syn-4b shows one

broad singlet at 10.5 ppm (121.5 MHz, toluene-d₈) clearly

indicating that the phosphorus atom is not coordinated to

manganese.²⁰Upon cooling, the singlet splits into two singlets,

revealing the occurrence of a dynamic process in solution.

Examination of the coalescence behavior of the ³¹P resonances

in the 193–303 K range (121.5 MHz, toluene-d₈) leads to

activation barriers of ca. 14.9 kcal mol^-1for the dynamic

processes involved (∆δ_P) 37 Hz; T_c) 298 K).²¹All isomers

of syn-4b, which are in a fast exchange (NMR time scale), could

be fully characterized at low temperature. The ¹³C{¹H] NMR

anti-4b, syn-4b, syn-11, and syn-13

anti-4b

syn-4b

syn-11

syn-13

Mn1-C1

1.783(2)

1.784(2)

2.180(2)

2.011(2)

1.154(3)

1.152(3)

1.781(2)

1.791(2)

2.165(1)

2.018(1)

1.1490(2)

1.148(2)

1.768(2)

1.770(2)

2.122(2)

1.995(2)

1.131(3)

1.143(3)

1.803(2)

1.381(2)

1.472(2)

1.324(2)

1.790(2)

1.772(3)

2.168(2)

2.034(2)

1.149(3)

1.153(3)

Mn1-C2

Mn1-C3

Mn1-C4

C1-O1

C2-O2

C3-S1

C3-C4

1.407(3)

1.479(3)

1.322(3)

1.847(2)

1.493(3)

1.403(2)

1.486(2)

1.329(2)

1.839(1)

1.498(2)

1.391(3)

1.477(3)

1.341(3)

C3-C21

C4-C5

C5-P1

C5-C31

1.451(3)

1.751(2)

1.492(3)

1.517(3)

C5-C41

C41-P1

1.844(2)

1.868(5)

C41-S1

C51-P1

1.846(2)

88.84(9)

101.63(8)

83.14(8)

77.46(8)

111.13(9)

38.98(8)

1.868(6)

88.35(7)

102.85(6)

80.69(6)

109.99(6)

38.98(5)

C1-Mn1-C2

C1-Mn1-C3

C1-Mn1-C4

C2-Mn1-C3

C2-Mn1-C4

C3-Mn1-C4

Mn1-C1-O1

Mn1-C2-O2

Mn1-C3-S1

Mn1-C3-C4

87.15(10)

98.43(9)

82.57(9)

81.31(9)

115.87(10)

39.03(8)

177.94(19) 176.8(3)

178.13(19) 177.8(2)

113.18(9)

65.51(11)

115.98(13) 120.55(16)

114.62(13)

113.94(14)

124.41(16) 123.9(2)

84.85(12)

84.22(11)

111.73(12)

107.42(12)

83.28(11)

38.50(9)

179.23(19) 178.35(13)

178.31(19) 179.32(14)

64.02(11)

64.85(7)

65.53(14)

Mn1-C3-C21 119.00(13) 117.28(9)

S1-C3-C4

S1-C3-C21

C4-C3-C21

Mn1-C4-C3

Mn1-C4-C5

C3-C4-C5

C4-C5-C31

C4-C5-P1

C4-C5-C41

C31-C5-C41

C31-C5-P1

C5-P1-C41

C5-P1-C51

C41-P1-C51

C3-S1-C41

125.78(18) 123.70(12)

77.00(12) 76.17(8)

143.86(16) 142.08(10)

139.11(19) 141.65(13)

125.53(18) 118.34(11)

114.69(15) 119.98(10)

75.46(11)

75.97(14)

146.46(15) 140.02(19)

138.05(18) 144.0(2)

130.96(18) 121.5(2)

spectrum shows two sets of three doublets at δ 188.1 (J_CP

≈

24 Hz), 131.8 (J_CP) 38 Hz), and 27.6 (J_CP) 15 Hz), and δ

186.4 (J_CP) 24 Hz), 130.9 (J_CP) 38 Hz), and 27.7 (J_CP) 15

Hz) ppm, attributable to the C_ꢀ, C_γ, and C_Rcarbon atoms (see

Scheme 2 for labeling scheme) for the coordinated allene ligand

in each isomer, respectively. The ¹H spectrum shows one singlet

for each isomer at δ 3.84 and 3.44 ppm attributable to the proton

attached to C_R. The chemical shift of that proton actually

constitutes the spectroscopic signature of allene complexes 4

as compared with their isomer 3, considering that in the later

species the proton attached to the allene ligand possesses a

vinylic character and thus appears at much lower ﬁeld, in the

8.2–8.7 ppm range.¹⁰Accordingly, we interpret the dynamic

process observed for syn-4b in terms of a fast (NMR time scale)

propeller rotation of the coordinated allene around the axis

joining the Mn atom and the centroid of the coordinated CdC

bond. This excludes the occurrence of a fast 1,2-shift of the

allene ligand, of the type previously observed, for instance, in

cationic [Fp(η²-allene)]⁺complexes.²²On the other hand, the

activation barrier estimated here ﬁts well with those previously

reported by Lentz et al. for the propeller rotation of the allene

in a series of parent (η⁵-R₅C₅)(CO)₂Mn[η²-{allene}] complexes

(9–15 kcal mol^-1).²³

121.0(2)

117.50(19)

119.66(14) 121.10(9)

102.43(9)

101.55(9)

105.30(9)

98.0(3)

104.1(2)

104.8(4)

101.35(10)

Examination of the ³¹P NMR spectra of anti-4b as a function

of temperature also revealed that this complex also experiences

a ﬂuxional process in solution, with an estimated activation

barrier of 12.8 kcal mol^-1(anti-4b: ∆δ_P) 163 Hz; T_c) 273

K (toluene-d₈)).²¹Considering the magnitude of the activation

barrier, the ﬂuxional process is attributed to the propeller rotation

of the allene ligand, although for that complex a proper

combination of solvent, temperature, and instrument allowing

unambiguous characterization of each rotamer (only averaged

¹H and ¹³C{¹H} spectra are given in the Experimental Part)

could not be determined.

Structure of anti-Cp′(CO)₂Mn[η²-{HC(Tol)dCdC(Ph)-

PCy₂}] (anti-4b). Relevant crystallographic data for anti-4b are

shown in Tables 2 and 3. An ORTEP drawing of the molecule

appears in Figure 2. The complex consists of an allene ligand,

HC(Tol)dCdC(Ph)PCy₂, bound to a Cp′(CO)₂Mn fragment in

an η²-C,C mode through the carbon atoms C3 and C4, C3

bearing a tolyl group (which labels the carbene carbon atom in

the antecedent species 1), and a hydrogen atom. The noncoor-

dinated carbon atom C5 bears a phenyl group and a dicyclo-

hexylphosphido group. This clearly shows that the complex anti-

4b results from a nucleophilic attack of the lithium dicyclo-

hexylphosphide at the remote alkynyl carbene atom. Finally,

the dicyclohexylphosphido group is found in a transoid position

relative to the MeCp(CO)₂Mn fragment on the C4-C5 double

bond, thus conferring an anti conﬁguration to the complex. The

(20) Chemical shifts for the phosphorus nuclei in complexes of the type

Cp(CO)_2-nL_nMnPR₃are typically in the 80–120 ppm range: Ginzburg,

A. G.; Fedorov, L. A.; Petrovskii, P. V.; Fedin, E. I.; Setkina, V. N.;

Kursanov, D. N. J. Organomet. Chem. 1974, 73, 77., see also ref 15b.

(21) The activation energy barrier was estimated using the approximation

of the Eyring equation: ∆G^q) RT_c(22.96 + ln T_c/δν)η, where T_c(K) is the

coalescence temperature of two signals separated by δν (Hz).

(22) (a) Ben-Shoshan, R.; Pettit, R. J. Am. Chem. Soc. 1967, 89, 2231.

(b) Foxman, B.; Marten, D.; Rosan, A.; Raghu, S.; Rosenblum, M. J. Am.

Chem. Soc. 1977, 99, 2160.

(23) (a) Lentz, D.; Willemsen, S. Organometallics 1999, 18, 3962. (b)

Lentz, D.; Nickelt, N.; Willemsen, S. Chem.-Eur. J. 2002, 8, 1205.

2082 Organometallics, Vol. 27, No. 9, 2008

Sentets et al.

Table 3. Crystal Data and Structure Reﬁnements for Complexes 2a, anti-4b, syn-4b, syn-11, and syn-13

2a

anti-4b

syn-4b

syn-11

syn-13

empirical formula

M_r

T/K

C₃₇H₃₂Cl₂MnO₂P

665.44

180

C₃₆H₄₂MnO₂P

592.61

100

C₃₆H₄₂MnO₂P

592.61

120

C₃₁H₂₇MnO₂S

518.56

160

C₃₀H₂₉MnO₃

492.47

180

λ/Å

0.71069

monoclinic

P2₁/n (# 14)

9.2247(9)

11.1454(10)

30.466(3)

97.174(11)

3107.8(5)

4

cryst syst

space group (no.)

a/Å

monoclinic

C2/c (#15)

24.054(4)

14.1761(14)

19.2790(18)

95.194(15)

6547.0(13)

8

monoclinic

P2₁/n (# 14)

8.8673(4)

29.3918(12)

12.0901(5)

107.574(4)

3003.9(2)

4

monoclinic

P2₁/n (# 14)

9.923(3)

21.7612(17)

12.017(5)

104.77(5)

2509.1(14)

4

monoclinic

P2₁/n (# 14)

13.88542(8)

10.8128(6)

17.1782(5)

108.37(4)

2442.2(6)

4

b/Å

c/Å

ꢀ/deg

V/Å³

Z

D_c/g cm^-3

µ/mm^-1

F(000)

1.350

0.647

2752

1.310

0.524

1256

1.267

0.507

1256

1.373

0.636

1080

1.339

0.572

1032

θ

_max/deg

completeness to θ_max(%)

25.98

0.98

-29 e h e29

-17 e k e 17

-23 e l e 23

31 480

6315

6315/0/408

1.08

32.09

0.94

-13 e h e 12

-42 e k e 42

-16 e l e 18

31 224

9853

9853/0/363

1.03

33.38

0.90

-14 e h e 14

-17 e k e 17

-42 e l e 44

10 897

5628

5628/0/473

0.84

32.5

0.94

-14 e h e1 4

-32 e k e 32

-17 e l e 17

27 553

8530

8530/0/319

1.07

30.3

0.99

index range, hkl

-20 e h e 19

-12 e k e 15

-24 e l e 24

11 2126

7320

no. of reﬂns collected

no. of indep reﬂns

no. of data/restraints/params

GOF

7320/0/309

1.03

R [I > 2σ(I)]

0.0536

0.1339

0.0669

0.0560

0.1088

0.0942,

0.0402

0.0688

0.0763

0.0424

0.1048

0.0781

0.0597

0.1565

0.1474

R_w[I > 2σ(I)]

R (all data)

R_w(all data)

0.1417

-0.44/0.63

0.1184

-0.56/0.73

0.1072

-0.26/0.43

0.1269

-0.32/0.58

0.1789

-0.75/1.18

∆F_max/min/e Å^-3

phosphorus atom is clearly away from the manganese atom, as

indicated by the nonbonding distance Mn1 · · · P1 of 4.693(1) Å.

Trends in the metrical features are similar to those found in

other manganese allene complexes.^23,24In particular, the

manganese-to-central carbon atom distance (Mn-C4 ) 2.011(2)

Å) is signiﬁcantly shorter than the manganese-to-terminal carbon

atom (Mn-C3 ) 2.180(2) Å). The noncoordinated CdC double

bond (C4-C5 ) 1.322(3) Å) compares reasonably well with

those of the free allene molecules (1.307 Å),²⁵in contrast to

the coordinated one, which is signiﬁcantly elongated (1.407(3)

Å). As a consequence of its coordination to the metal, the allene

is strongly bent (C3-C4-C5 ) 143.86(16)°). As we can already

see in Table 3, these features appear to be quite constant for all

the Mn-[{η²-allene}] complexes we shall encounter in the

present report.

Structure of syn-Cp′(CO)₂Mn[η⁴-{HC(Tol)dCdC(Ph)-

PCy₂}] (syn-4b). As shown in Figure 3, complex syn-4b equally

consists of a TolC(H)dCdC(Ph)PCy₂allene ligand bound to

the Cp′(CO)₂Mn fragment in an η²-C,C fashion through the

carbon atoms C3 and C4. As for anti-4b, C3 bears a hydrogen

atom and a tolyl group, whereas the noncoordinated carbon atom

C5 bears a dicyclohexylphosphine and a phenyl group, showing

that the present complex also results from a nucleophilic attack

of the phosphide at the remote alkynyl carbon atom. The later

group now occupies a cisoid position relative to the metal

fragment on the C5-C5 double bond, thus conferring a syn

conﬁguration to the complex. Even in that position, the

phosphorus atom is clearly at a nonbonding distance of the

manganese center (3.859(1) Å). As shown in Table 2, bonding

distances and angles in both syn-4b and anti-4b complexes are

otherwise similar within the experimental errors.

Figure 2. Perspective view of the complex anti-Cp′(CO)₂Mn[η²-

{HC(Tol)dCdC(Ph)PCy₂}] (anti-4b). Thermal ellipsoids are drawn

at the 50% probability level.

protonation with a saturated solution of NH₄Cl gave no traces

of type- 2 complexes, whereas IR monitoring revealed the

formation of allene complexes only. For R ) Ph, the ³¹P NMR

analysis revealed the formation of an inseparable mixture of

three different complexes (Scheme 3). The ﬁrst one (14%

spectroscopic yield based on the integration of ³¹P signals) was

readilycharacterizedastheη²-allenecomplexsyn-Cp′(CO)₂Mn[η²-

{Ph₂P(Tol)CdCdC(Ph)H}] (syn-3a). The structure of the

second complex, namely, Cp′(CO)₂Mn[η²-{HC(Tol)dCdC-

(Ph)Ph₂P}] (4a, 86% spectroscopic yield), was inferred from

the spectroscopic data. Indeed, complex 4a gives two singlets

in the ³¹P NMR spectra at 8.5 and 6.0 ppm (1:4 ratio, 121.5

MHz, 298 K), and, just like 4b, it experiences a ﬂuxional

phenomenon. Examination of the coalescence behavior of the

two ³¹P signals led us to evaluate an energy barrier of 16.2

Subsequent Protonation with a Weak Acid. Treatment of

1 with the diorganophosphide LiPR₂(R ) Ph, Cy) followed by

(24) Franck-Neumann, M.; Neff, D.; Nouali, H.; Martina, D.; de Cian,

A. Synlett. 1994, 657.

(25) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,

A. G.; Taylor, R. J. J. Chem. Soc., Perkin Trans. 2 1987, S1.

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2083

metalate species B (Scheme 4).²⁷On one hand, protonation of

A with a strong organic acid CF₃SO₃H takes place at the less

hindered basic site, namely, the P atom, thus affording the

zwitterionic η¹-allenyl species C. This intermediate species is

identical to the one invoked by us in the course of the addition

of secondary phosphines to 1 and, likewise, a fast rearrangement

by 1,3-hydrogen migration followed by a CO insertion into the

MndC bond en route to 2. In the case where R ) Cy, the P

atom is more protected by steric hindrance. Thus, protonation

may competively take place at the Mn center to produce the

hydrido species D. Then, a reductive elimination from the

incipient η¹-allenyl affords 4, eventually as a mixture of anti

and syn isomers. A similar mechanism was previously proposed

by Casey et al. to account for the formation of the parent allene

complex [(η⁵-C₅H₅)(CO)₂Re[η²-{TolC(H)dCdC(Ph)PPh₂Me}]-

[OTf] upon protonation of the zwiterionic η¹-allyl complex [(η⁵-

C₅H₅)(CO)₂Re[η¹-{TolCdCdC(Ph)PPh₂Me}].¹²On the other

hand, protonation with a weak acid, such as aqueous NH₄Cl,

takes place only at the Mn center to afford D, as the unique (R

) Cy) or largely major (R ) Ph) intermediate species, ultimately

producing 4 upon reductive elimination. Complex 3, which was

observed in trace amounts for R ) Ph only and whatever the

protonation source is, likely arises from protonation of the η¹-

propargyl species B under such conditions. Such a protonation

type has been shown in some instances to be highly anti-

selective.²⁸

Figure 3. Perspective view of the complex anti-Cp′(CO)₂Mn[η²-

{HC(Tol)dCdC(Ph)PCy₂}] (syn-4b). Thermal ellipsoids are drawn

at the 50% probability level.

kcal mol^-1(∆δ_P) 132 Hz; T_c) 338 K, toluene-d₈)²¹for the

process attributed, as for 4b, to the propeller rotation of the

allene ligand.²³In the ¹³C NMR spectrum, each rotamer exhibits

a characteristic set of three doublets at δ 191.10 (J_CP≈ 53 Hz),

132.6 (J_CP≈ 20 Hz), and 28.4 (J_CP≈ 15 Hz) ppm, and δ 189.74

(J_CP≈ 53 Hz), 132.3 (J_CP≈ 20 Hz), and 30.9 (J_CP≈ 15 Hz)

ppm, respectively, for the C_ꢀ, C_γ, and C_Rcarbon atoms (see

Scheme 3 for labeling scheme), whereas in the ¹H NMR

spectrum, the protons attached to C_Rprovide two characteristic

singlets at δ 4.05 and 3.96 ppm. ROESY experiments aimed at

determining whether this complex was the syn or anti isomer

remained, however, inconclusive. Finally, the ³¹P spectrum also

showed a set of singlets at 20.1 and 22.2 ppm (1:1 ratio, 121.5

MHz, 298 K) corresponding to a third complex present in trace

amounts only (ca. 1% spectroscopic yield). These two signals

were found to coalesce at 369 K due to a dynamic process, the

Digression into the Thermal Rearrangement of the

Phosphinoallene Complexes 3a and 4a,b. During the course

of ³¹P NMR experiments aimed at determining the rotation

barrier of the allene ligands in 3 and 4, we were led to observe

that such complexes are easily transformed under thermal

activation. A shift of the ³¹P NMR signal from the 5–20 ppm

range in 3 and 4 to the 96–98 ppm range, as well as a shift of

IR ν_CObands from 1977, 1922 cm^-1in 3 and 4 to 1934, 1872

cm^-1, were clearly indicative that coordination of the pendant

phosphorus atom had taken place. The rearrangements of

complexes 3a and 4a (always containing ca. 10% of 3a, Vide

supra) and 4b were found to be complete over 3 h in reﬂuxing

THF, thus giving Cp′(CO)₂Mn[η¹-{Ph₂P(Tol)CdCdC(Ph)H}]

(5a), Cp′(CO)₂Mn[η¹-{Ph₂P(Ph)CdCdC(Tol)H}] (6a, con-

taminated by ca. 10% of 5a), or (η⁵-MeC₅H₅)(CO)₂Mn[η¹-

{Cy₂P(Ph)CdCdC(Tol)H}] (6b), respectively, in good yields

(Schemes 5 and 6). Complexes 5a and 6a,b were characterized

by the usual spectroscopic techniques. In addition to the ³¹P

NMR and IR characteristics just mentioned, the spectroscopic

signature of complexes 5a and 6a,b consists of a doublet at

209.4, 209.7, or 207.7 ppm, respectively, in the ¹³C NMR

spectra for the central carbon of the pendant allene moiety (J_CP

) 3 Hz) and a doublet at 6.23, 6.23, or 6.45 ppm, respectively,

barrier of which is about 17.2 kcal mol^{-1 21}

. Although the latter

complex could not be more precisely characterized, we presume

it may correspond to the second isomer: syn or anti-4a.

For R ) Cy, ³¹P NMR analysis of the crude reaction mixture

(after ﬁltration on an alumina plug) showed that the reaction

affords exclusiVely complex 4b. The latter was isolated in 74%

yield as a 1:2 mixture of syn and anti isomers.

Mechanistic Considerations. As noted in the Introduction,

the use of neutral phosphorus probes demonstrated that man-

ganese alkynyl carbene complexes are prone to undergo

nucleophilic attack at the remote carbon atom, a reaction

pathway that, for bulky incoming substrates, is strongly favored

over nucleophilic attack at the carbenic carbon center.¹⁰Here,

the lithium diorganophosphides must be considered as bulky

substrates due to their known ability to form aggregates in THF

solution,²⁶and they do appear even bulkier than their neutral

secondary phosphine antecedents.^26cThus, nucleophilic attack

of the organylphosphide at the remote alkynyl carbon atom to

form the anionic η¹-allenyl metalate species A is likely to be

strongly favored over the formation of anionic η¹-propargyl

1

in the H NMR spectra for the allenic H atom (J_HP) 5 Hz).

Although a detailed investigation of the mechanism of these

transformations was beyond the present objective, we were

intrigued by the fact that monitoring the transformation of 3a

by ³¹P NMR spectroscopy revealed the presence of two transient

(27) The IR monitoring clearly reveals the anionic nature of the

intermediate species, but neither supports nor contradicts the formation of

an allenyl and/or a propargyl species. Indeed, one would expect a weak

band at ca. 1840–1860 cm^-1ascribable to the ν_CdCdCvibration,¹⁰which is

not clearly observed, possibly due to an overlap with the leftmost ν_COband

(1873 cm^-1). On the other hand, the propargylic species, which should

display a weak IR band at ca. 2180 cm^-1for the ν_CtCvibration,¹⁰may not

be observable due to an extremely low concentration under these reaction

conditions.

(26) (a) Bartlett, R. A.; Olmstead, M. M.; Power, P. P. Inorg. Chem.

1986, 25, 1243. (b) Reich, H. J.; Dykstra, R. R. Organometallics 1994, 13,

4578. (c) Fernández, I.; Martínez-Viviente, E.; Pregosin, P. S. Inorg. Chem.

2004, 15, 4555.

(28) (a) Lichtenberg, D. W.; Wojcicki, A. J. Am. Chem. Soc. 1972, 94,

8271. (b) Lichtenberg, D. W.; Wojcicki, A. J. Organomet. Chem. 1975,

94, 311. (c) Raghu, S.; Rosenblum, M. J. Am. Chem. Soc. 1973, 95, 3060.

2084 Organometallics, Vol. 27, No. 9, 2008

Sentets et al.

Scheme 3

Scheme 4

Scheme 5

surprisingly enough, coordination of a Cp′(CO)₂Mn unit to the

pendant phosphorus atom of 3a induces a slippage of the allene

moiety, which otherwise does not occur spontaneously.

Scheme 6

species (Figure 4), which could eventually be intercepted by

quenching the reaction at room temperature after 30 min.

The ﬁrst species, 7a, was identiﬁed as the free diphenyl(1-

tolyl-3-phenyl-1,2-propadienyl) phosphine. Interestingly, 7a

could be alternatively obtained in a nearly quantitative yield

upon photolysis of 3a in dichloromethane solution (Scheme 7).

The second transient species detected at intermediate stage

appeared to be a bimetallic complex of the diphenyl(1-tolyl-3-

phenyl-1,2-propadienyl) phosphino-allene ligand, namely,

[Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Ph)CdCdC(Tol)H}] (8a), in which

the phosphino-allene ligand is bound to a ﬁrst Cp′(CO)₂Mn unit

through the phosphorus atom and to a second Cp′(CO)₂Mn unit

via coordination of the CdC(H)Ph bond of the allene moiety.

Noticeably, the same complex could also be prepared in good

yields upon reaction of Cp′(CO)₂Mn(THF) with either 5a (66%

yield) or 3a (56% yield). The second route shows that,

Figure 4. Monitoring by ³¹P{¹H} NMR of the thermal rearrange-

ment of 3a to give 5a (70 °C, toluene-d₈).

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2085

Scheme 7

Scheme 8

by photolysis of syn/anti-4b, could be detected. Noticeably,

when the rearrangement was performed starting from pure syn-

4b, an accumulation of anti-4b was observed in the early stages

of the reaction. This syn f anti isomerization may result from

competitive recombination of transient Cp′(CO)₂Mn fragments

with 9b, in the direction of the less hindered anti isomer.

Extension to Representative S- and C-Nucleophiles. Re-

activity of the Alkynyl Carbene Cp′(CO)₂MndC(Tol)-

CtCPh (1) toward p-Toluenethiol and toward Lithium

p-Toluenethiolate Followed by Protonation. Although pre-

liminary experiments indicated that the alkynyl carbene complex

Cp′(CO)₂MndC(Tol)CtCPh (1) does not spontaneously react

with p-toluenethiol, we were led to observe that a reaction takes

place in the presence of a substoichiometric amount of triethy-

lamine (20%). IR monitoring showed the appearance of two

ν_CObands at 1920 and 1972 cm^-1, compatible with the

formation of an allene species Cp′(CO)₂Mn[{η²-allene}]. Al-

though chromatographic workup afforded a single yellow band,

subsequent NMR analyses revealed that the reaction product

consists of a 1.8:1 mixture of two inseparatable isomeric allene

complexes, formulated as Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC-

(Ph)H}] (11) and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)STol}]

(12) (Scheme 10, route A).

On the other hand, stepwise sequential treatment of the

alkynyl carbene complex Cp′(CO)₂MndC(Tol)CtCPh (1) with

lithium p-toluenethiolate and NH₄Cl_aqled eventually to a mixture

of the same complexes, 11 and 12, via the intermediacy of an

anionic species (IR (ν_CO, THF): 1879(s), 1802(m), 1760(m)

cm^-1). Signiﬁcantly, under such conditions, complex 12 appears

to be the major reaction product (Scheme 10, route B).

Scheme 9

Butler et al.²⁹and Angelici et al.³⁰have shown that the

substitution of η¹-(thio)ethers or η²-alkene attached to a

Cp(CO)₂Mn fragment for a phosphine proceeds through a

dissociative S_N1 mechanism. On this basis, one could envisage

that the rearrangement 3a f 5a proceeds through a similar

dissociative pathway, where recapture of the liberated phos-

phinoallene ligand by an unsaturated Cp′(CO)₂Mn fragment

would take place irreversibly via the phosphorus atomspossibly

within the solvent cagesultimately leading to the ﬁnal product

5a (Scheme 8).

Complexes Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC(Ph)H}] (11)

and [Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)STol}] (12) were

characterized by usual spectroscopic techniques complemented

for 11 by an X-ray structure analysis revealing the syn

conﬁguration of the complex. The room-temperature ¹³C{¹H}

NMR spectrum of the syn-11/12 mixture shows in particular

two sets of three signals at δ 170.9 (br), 125.5 (br), and 38.5

(br) ppm and at δ 180.2 (br), 123.2 (br), and 33.3 (br) ppm,

attributable to the C_ꢀ, C_γ, and C_Rcarbon atoms for the

coordinated allenic chain within syn-11 and 12, respectively (see

Scheme 10 for labeling). Each isomer gives very distinct and

characteristic signals for the proton attached to the allenic chain

at δ 8.20 (s br) ppm for syn-11 and at δ 4.1 (s br) ppm for 12.

Upon cooling the samples in the NMR probe, all isolated signals

are clearly seen to split, thereby revealing that both complexes

actually experience a ﬂuxional process in solution. Examination

of the coalescence behavior of the two pairs of signals

attributable to C_ꢀwithin complexes syn-11 and 12 led to the

The accumulation of the bimetallic species 8a at intermediate

stage could arise from competitive capture of Cp′(CO)₂Mn

fragments either by the starting complex 3a acting as an

excellent σ-donor ligand or by the ﬁnal complex, 5a, acting as

a potential π-donor ligand, or 7a acting as a bidentate σ/π-

donor ligand. On the other hand, no matter the source of 8a,

competitive dissociation of the allene-bound metal fragment

“Cp′(CO)₂Mn” from 8a would also lead to 5a.

Monitoring the thermal rearrangement of 4a led to a similar

observation, namely, an accumulation of the diphenyl(1-phenyl-

3-tolyl-1,2-propadienyl) phosphine (9a) and the bimetallic

species [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Ph)CdCdC(H)Tol}] (10a)

in the early stages of the reaction (Scheme 9), followed by total

conversion into 6a.

Finally, a monitoring of the thermal rearrangement of syn-

and anti-4b shows very little accumulation of the transient

species. Only traces of dicyclohexyl(1-phenyl-3-tolyl-1,2-pro-

padienyl) phosphine (9b), which could otherwise be prepared

evaluation of activation barriers of ca. 13.0 and 14.0 kcal mol^-1

respectively (syn-11: ∆δ_Cꢀ) 688 Hz; T_c) 293 K; 12: ∆δ_Cꢀ

545 Hz; T_c) 313 K)²¹for the ﬂuxional processes attributed,

,

)

(29) Angelici, R.; Loewen, W. Inorg. Chem. 1967, 6, 682.

(30) Butler, I. S.; Sawai, T. Inorg. Chem. 1975, 14, 2103.

2086 Organometallics, Vol. 27, No. 9, 2008

Sentets et al.

Scheme 10

Scheme 11

as for 4, to the propeller rotation of the allene ligands.²³

Apparently, each complex exists as a single stereoisomer

(without taking rotamers into account). However, the structure

of 12 has not been established in full since all attempts to

determine by NMR the position of the p-toluenethiolate group

relative to the Tol/Ph groups and the position of the p-

toluenethiolate relative to the metal fragment remained incon-

clusive. The proposed structure for 12 appearing in Scheme 10

rests on the parallel that can be drawn from the reactivity of 1

toward diorganophosphide, the allene isomer bearing a hydrogen

R to Mn resulting in a nucleophilic attack on the remote alkynyl

carbon atom. On the other hand, single crystals of syn-11 could

be grown, allowing full structural characterization of the

complex.

The later mechanism would be the only operating one in the

formation of syn-11 and 12 through route B shown in Scheme

10. Just like lithium diorganophosphides, lithium thiolates are

known to form bulky aggregates in THF.³²Accordingly, lithium

p-toluenethiolate is expected to attack at the less hindered remote

alkynyl carton atom, which may account for the predominance

of complex 12 over complex syn-11 in that case.

Structure of syn-Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC-

(Ph)H}] (syn-11). Relevant crystallographic data for syn-11 are

shown in Tables 2 and 3, along with those for complex 4b. An

ORTEP drawing of the molecule appears in Figure 5. As

expected, complex syn-11 consists of the allene complex

Cp′(CO)₂Mn[{η²-allene}]. The allene ligand is bound to the

Cp′(CO)₂Mn fragment through both the central atom C4 and

the neighboring atom C3 bearing a tolyl group and a p-

toluenethiolate group. Clearly, the complex syn-11 results from

a nucleophilic attack of the thiolsor thiolatesat the carbenic

carbon center of the antecedent species 1. The noncoordinated

carbon atom C5 bears both a phenyl group and a hydrogen atom,

in such a way that the phenyl ring is in cisoid position relative

to the Cp′(CO)₂Mn fragment, thus conferring a syn conﬁguration

to the complex. Metrical features within syn-11 and syn- or anti-

4b are otherwise very similar.

Prior to this work, Moretó et al.^16aand de Meijere et al.³¹

reported that group 6 alkynyl[alkoxy] carbene complexes react

with simple thiolssincluding p-toluenethiol^16asto form 2-thio

alkenyl complexes resulting formally from an addition of the

S-H bond across the CtC triple bond. In the present work,

no complex of that sort was ever observed. A mechanism that

may account for the formation of the isomeric allene complexes

is shown in Scheme 11. Competitive nucleophilic attack of the

thiol on either the carbenic carbon atom or the remote alkynyl

carbon atom would result in the formation of both zwitterionic

species A and B. Closely related species have been previously

identiﬁed in the reaction of 1¹⁰or rhenium analogues¹²with

tertiary phosphines. Triethylamine, which appears to be neces-

sary for a reaction to occur, is likely to assist the hydrogen

Reactivity of the Alkynyl Carbene Complex Cp′(CO)₂-

MndC(Tol)CtCPh (1) toward Cyclohexanone Lithium

Enolate, Followed by Protonation. The alkynyl carbene

complex Cp′(CO)₂MndC(Tol)CtCPh (1) was found to react

with cyclohexanone lithium enolate to form an anionic species

(IR (ν_CO, THF): 1875(s), 1805(m), 1770(m) cm^-1). Subsequent

protonation with NH₄Cl_aqgave a neutral species exhibiting two

ν_CObands at 1972 and 1920 cm^-1(THF). Chromatographic

workup afforded a single new complex, which was subsequently

identiﬁed as the η²-allene complex syn-Cp′(CO)₂Mn[η²-

{H(Tol)CdCdC(Ph)CH(CH₂)₄C(O)}] (syn-13) (Scheme 12).

28

transfer from sulfur to C_γor to C_R, respectively, possibly

through the intermediacy of the hydrido species C in the second

case, to afford complexes syn-11 and 12, respectively. The

formation of syn-11 and 12 could also result from direct

nucleophilic attack of 1 by p-TolS^-sgenerated in equilibrium

concentration upon reaction of NEt₃and p-TolSHsfollowing

a route that would exactly match the reaction of Ph₂P^-with 1

(Scheme 4).

The ¹³C{¹H} NMR spectrum of syn-13 shows the now

familiar set of three signals at δ 167.81, 126.72, and 30.28 ppm

(31) (a) Duetsch, M.; Stein, F.; Lackmann, R.; Pohl, E.; Herbst-Irmer,

R.; de Meijere, A. Chem. Ber. 1993, 12, 2556. (b) de Meijere, A.; Schirmer,

H.; Stein, F.; Funke, F.; Duetsch, M.; Wu, Y.-T.; Noltemeyer, M.; Belgardt,

T.; Knieriem, B. Chem.-Eur. J. 2005, 11, 4132.

(32) (a) Sigel, G. A.; Power, P. P. Inorg. Chem. 1987, 26, 2819. (b)

Ellison, J. J.; Power, P. P. Inorg. Chem. 1994, 33, 4231. (c) Ruhlandt-

Senge, K.; Power, P. P. Bull. Soc. Chim. Fr. 1992, 129, 594.

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2087

Figure 6. Perspective view of the complex syn-Cp′(CO)₂Mn[η²-

H(Ph)CdCdC(Ph)CH(CH₂)₄C(O)) (syn-13). Thermal ellipsoids are

shown at the 50% probability level.

Figure 5. Perspective view of the complex syn-Cp′(CO)₂Mn[η²-

{TolS(Tol)CdCdC(H)Ph}] (syn-11). Thermal ellipsoids are drawn

at the 50% probability level.

alkynyl carbon in the antecedent species 1. Clearly, the X-ray

structure revealed that complex syn-13 effectively results from

a nucleophilic attack of the enolate on this carbon atom, as

shown in Scheme 12. Again, the bulkiness of lithium 2-cyclo-

hexanone enolate³³may account for a selective nucleophilic

attack on that carbon atom. In addition, the phenyl ring attached

to C5 is directed away from the Cp′(CO)₂Mn metal fragment,

thus conferring a syn conﬁguration to the complex. The carbon

atom C41 shown in Figure 6 exhibits an R conﬁguration,

whereas the allene would have, if free, an R axial conﬁguration

(naturally, since complex syn-13 crystallize in the P2₁/n space

group, the other enantiomer is present in the crystal). Metrical

features within complex syn-13, syn-11, and 4b are otherwise

similar.

Scheme 12

attributable to the C_ꢀ, C_γ, and C_Rcarbon atoms of the allene

chain (see Scheme 12 for labeling). The occurrence of a

C-alkylation of the enolate is inferred from the spectroscopic

data, clearly indicating the presence of a 2-oxocyclohexyl ring

(IR ν_CO1708(w) cm^-1; NMR ¹³C{¹H} δ 211.52 (CdO), 61.06

(CH); NMR ¹H δ 4.62 (CH)). The ¹H NMR spectrum shows a

characteristic signal at 3.85 ppm indicative that the allene moiety

is bound to the Cp′(CO)₂Mn fragment via the carbon-carbon

double bond H(Tol)CdC. No signal could ever be detected in

the 8–9 ppm region, denoting the absence of any isomer in

which the metal fragment would be bound to a carbon-carbon

double bond like that of CdC(Ph)CH(CH₂)₄C(O). Although the

C-alkylation of the enolate generates an additional stereogenic

center within the coordinated allene ligand, all RT ¹³C{¹H}

NMR signals of isolated syn-13 remain sharp, suggesting that

not only one (syn) isomer is formed, but also that the C-C

bond formation is diastereoselective. However, we cannot

ascertain that the reaction is indeed totally diastereoselective

since all attempts to obtain workable NMR data on the crude

reaction material failed due to the presence of paramagnetic

impurities.

Conclusion

We have shown that the non-heteroatom-substituted alkynyl

carbene complex Cp′(CO)₂MndC(Tol)CtCPh (1) is prone to

give η²-allene complexes in good yields upon reaction of anionic

P-, S-, or C-nucleophiles, followed by protonation. The fairly

high regioselectivity observed here is understood in terms of a

major mechanistic pathway involving conjugate addition of the

nucleophile at the remote alkynyl carbon atom to give a transient

η¹-allenylmetalate complex, which undergoes subsequent pro-

tonation at the metal followed by reductive elimination of the

Mn-H bond to afford the ﬁnal η²-allene complex. Although

group 6 allene complexes remain elusive, a similar mechanistic

pathway may account for the observation of free allenes in

certain reactions of [group 6 alkylalkoxy] alkynyl carbenes with

nucleophiles.¹¹The principal outgrowth of the present report is

to provide the ﬁrst explicit evidence for the formation of allene

complexes through such a route, thereby adding a new facet to

the reactivity of alkynyl carbene complexes. Although the

stability of Cp⁽′⁾(CO)₂Mn(η²-allene) complexes might have been

a priori regarded as a drawback for synthetic purposes, this is

not the case, given that they are reactive enough to allow

modiﬁcations of the coordinated allene ligand,^24,34whereas the

Finally, single crystals of syn-13 could be ultimately grown,

allowing full structural characterization of the isolated complex.

Structure of syn-Cp′(CO) Mn[η²-{H(Ph)CdCdC(Ph)-

2

CHC(O)(CH₂)₄}] (syn-13). Relevant crystallographic data for

syn-13 are shown in Tables 2 and 3, along with those for

complexes 4b and syn-11. An ORTEP drawing of syn-13

appears in Figure 6. As expected, the metal fragment

Cp′(CO)₂Mn is coordinated to the H(Ph)CdC carbon-carbon

double bond of the allene ligand, thus corroborating the

information provided by ¹H NMR. The 2-oxocyclohexyl group

attached to the noncoordinated carbon atom C5 of the allene

ligand is adjacent to the phenyl ring that labels the remote

(33) (a) Arnett, E. M.; Moe, K. D. J. Am. Chem. Soc. 1991, 113, 7288.

(b) Streitwieser, A.; Wang, D. Z.-R. J. Am. Chem. Soc. 1999, 121, 6213.

(c) Streitwieser, A. J. Mol. Model. 2006, 12, 673.

(34) (a) Franck-Neuman, M.; Brion, F. Angew. Chem., Int. Ed. Engl.

1979, 18, 688. (b) Franck-Neuman, M.; Martina, D.; Neff, D. Tetrahedron:

Asymmetry 1998, 9, 697.

2088 Organometallics, Vol. 27, No. 9, 2008

Sentets et al.

1

free allene may be released either by oxidation³⁴or, as shown

in the present work, upon photolysis, thus giving new hopes

for future development.

(C_η), 103.0, 95.4, 92.3, 89.9, 82.1 (MeC₅H₄), 35.3 (d, C_R, J_CP

)

24 Hz), 21.6 (MeC₆H₄), 13.7 (MeC₅H₄); ³¹P{¹H} NMR (121.5

MHz, C₆D₆) δ 21.5; MS (EI) m/z 580 [M]^+•, 524 [M - 2(CO)]^+•

,

390 [M - Cp′(CO)₂Mn]⁺; IR (CH₂Cl₂): 1977, 1922 (ν_CO).

Formation of Cp′(CO)₂Mn[η⁴-{Ph₂P(Ph)CdCHC(Tol)dCd

O}] (2b) and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)PCy₂}] (4b)

upon Reaction of 1 with LiPCy₂Followed by Protonation with

CF₃SO₃H. In a typical experiment, a THF solution of lithium

dicyclohexylphosphidesgenerated in situ by addition of ⁿBuLi (0.70

mL of a 1.6 M solution in hexane, 1.1 mmol) to a solution of HPCy₂

(0.240 mL, 1.1 mmol) in THF (3 mL) at 0 °Cswas added dropwise

to a solution of complex Cp′(CO)₂MndC(Tol)CCPh (1, 0.099 g,

0.25 mmol) in THF (20 mL) at –80 °C. The solution turned orange.

A slight excess of CF₃SO₃H (0.030 mL, 0.34 mmol) was then

added. After stirring the solution for 2 min, the cold bath was

removed and the solvent was removed under high vacuum to give

an oily residue, which was subject to treatment by column

chromatography on alumina. An initial elution with a 1:10 diethyl

ether/pentane mixture gave a yellow band containing complex

Cp′(CO)₂Mn[η²-{Tol(H)CdCdC(Ph)PCy₂}] (4b) as a ca. 1:2 mix-

ture of syn/anti isomers, which were isolated as a yellow foam upon

removal of the solvents (0.039 g, 0.065 mmol, 26% yield). A second

elution with a 1:1 diethyl ether/pentane mixture afforded a brown

band containing Cp′(CO)₂Mn[η⁴-{Cy₂P(Ph)CdCHC(Tol)dCd

O}] (2b), which was subsequently isolated as a brown microcrys-

talline solid (0.083 g, 0.14 mmol, 55% yield). Analytically pure

syn-4b and anti-4b were obtained by fractional crystallization from

a solution in a 1:1 ether/hexane mixture. Some of the crystals

obtained were suitable for X-ray diffraction analyses.

Experimental Part

General Procedures. Tetrahydrofuran and diethyl ether used

for the syntheses were distilled under nitrogen from sodium

benzophenone ketyl just before use. Other solvents were puriﬁed

following standard procedure and stored under nitrogen. The reagent

grade chemicals ⁿBuLi (1.6 M solution in hexane), HPPh₂, HPCy₂H,

TolSH, and trimethylsilyloxycyclohexene were obtained from

Aldrich and used without further puriﬁcation. Cp′(CO)₂MndC-

(Tol)CtCPh (1) was prepared following literature procedures.¹⁰

All synthetic manipulations were carried out using standard Schlenk

techniques under an atmosphere of dry nitrogen. A liquid N₂/2-

propanol slush bath was used to maintain samples at the desired

low temperature. Chromatographic separation of the complexes was

performed on alumina (neutral, activity III (Aldrich)). Solution IR

spectra were recorded on a Perkin-Elmer 983G spectrophotometer

with 0.1 mm cells equipped with CaF₂windows. ¹H, ¹³C, and ³¹

P

NMR spectra were obtained on Bruker AC200, WM250, DPX300,

AMX400, or AMX500 spectrometers and were referenced to the

residual signals of the deuterated solvent. NMR spectra were

recorded at room temperature unless otherwise speciﬁed. Mass

spectra were recorded on AEI-MS9 or Nermag R10-10 mass

spectrometers (EI). Microanalyses of C and H elements were

performed on a Perkin-Elmer 2400 CHN analyzer.

Formation of Cp′(CO)₂Mn[η⁴-{Ph₂P(Ph)CdCHC(Tol)dCd

O}] (2a) and Cp′(CO)₂Mn[η²-{Ph₂P(Tol)CdCdC(Ph)H}] (syn-

3a) upon Reaction of 1 with LiPPh₂Followed by Protonation

with CF₃SO₃H. A THF solution of lithium diphenylphosphides

generated in situ by addition of ⁿBuLi (0.470 mL of a 1.6 M solution

in hexane, 0.67 mmol) to a solution of HPPh₂(0.100 mL, 0.57

mmol) in THF (3 mL) at 0 °Cswas added dropwise to a solution

of complex Cp′(CO)₂MndC(Tol)CCPh (1, 0.197 g, 0.50 mmol) in

THF (10 mL) at –80 °C. The solution turned orange. A slight excess

of CF₃SO₃H (0.050 mL, 0.57 mmol) was added, inducing a

darkening of the solution. After stirring the solution for 2 min, the

cold bath was removed and the solvent was removed under high

vacuum to give an oily brown residue, which was subject to

treatment by column chromatography on alumina. An initial elution

with a 1:4 diethyl ether/pentane mixture gave a yellow band

containing trace amount of Cp′(CO)₂Mn[η²-{Ph₂P(Tol)Cd

CdC(Ph)H}] (syn-3a, ca. 0.005 g, ca. 2%). A second elution with

a 1:1 diethyl ether/pentane mixture afforded a brown band contain-

ing Cp′(CO)₂Mn[η⁴-{Ph₂P(Ph)CdCHC(Tol)dCdO}] (2a), which

was subsequently isolated as a brown microcrystalline solid (0.203

g, 0.36 mmol, 72% yield). Crystals of 2a suitable for an X-ray

diffraction analysis were grown from a dichloromethane/hexane

mixture in the cold.

2b: ¹H NMR (400.1 MHz, 233 K, CD₂Cl₂) δ 7.8–6.2 (m, C₆H₅

3

and MeC₆H₄), 5.92 (d, 1H, H_ꢀ, J_HP) 13 Hz), 5.0–4.2 (m, 4H,

η⁵-MeC₅H₄), 2.9–0.8 (C₁₁H₂₂), 2.40 (s, MeC₆H₄), 1.74 (s, MeC₅H₄);

¹³C{¹H} NMR (100.6 MHz, 213 K, CD₂Cl₂) δ 237.2–232.8 (CO),

144.4–125.1 (C₆H₅and MeC₆H₄), 102.5, 88.6, 88.4 (³J_CP) 5 Hz),

86.5 (³J_CP) 6 Hz), 86.1 (MeC₅H₄), 89.7 (C_ꢀ, ²J_CP) 43 Hz), 71.9

(C_γ, ¹J_CP) 41 Hz,), 31.8 (C_R, ³J_CP) 15 Hz), 38.0–26.9 (C₁₁H₂₂),

21.7 (MeC₆H₄), 13.3 (MeC₅H₄); ³¹P{¹H} NMR (202.6 MHz, 213

K, CD₂Cl₂) δ 36.2; MS (CI) m/z 593 [MH]⁺, 564 [MH - CO]⁺,

536 [MH - 2CO]⁺; IR (THF) 1960, 1745 (η_CO). Anal. Calcd for

C₃₆H₄₂MnO₂P: C, 72.94; H, 7.15. Found: C, 72.87; H, 7.08.

1

syn-4b: H NMR (500.3 MHz, 213 K, CD₂Cl₂) δ 7.2–6.8 (m,

MeC₆H₄and C₆H₅), 4.95, 4.77, 4.75, 4.56 (m, MeC₅H₄, major

rotamer), 4.93, 4.89, 3.90, 3.36 (m, MeC₅H₄, minor rotamer), 3.84

(s, H_R, major), 3.44 (s, H_R, minor), 2.17 (s, MeC₆H₄), 1.95 (s,

MeC₅H₄, major), 1.84 (s, MeC₅H₄, minor), 2.3–0.9 (m, C₆H₁₁);

¹³C{¹H} NMR (125.8 MHz, 213 K, CD₂Cl₂) δ 235.7, 230.5 (CO,

2

minor), 233.1, 231.0 (CO, major), 188.1 (d, C_ꢀ, J_CP) 24 Hz,

major), 186.4 (d, C_ꢀ, ²J_CP) 24 Hz, minor), 144.5–127.4 (MeC₆H₄

1

and C₆H₅), 131.8 (d, C_γ, J_CP) 38 Hz, major), 130.9 (d, C_γ, J_CP

) 38 Hz, minor), 102.8, 89.9, 88.5, 85.3, 84.9 (MeC₅H₄, major),

102.6, 91.5, 91.4, 89.3, 83.5 (MeC₅H₄, minor), 36.2–26.4 (C₆H₁₁),

2a: ¹H NMR (400.1 MHz, 233 K, CD₂Cl₂) δ 8.00–6.28 (m, C₆H₅

3

27.7 (d, C_R, J_CP) 15 Hz, minor), 27.6 (d, C_R, J_CP) 15 Hz,

major), 21.1 (MeC₆H₄, major), 21.0 (MeC₆H₄, minor), 13.4

(MeC₅H₄, minor), 13.0 (MeC₅H₄, major); ³¹P{¹H} NMR (121.5

MHz, 298 K, toluene-d₈) δ 10.5 (br s); ³¹P{¹H} NMR (121.5 MHz,

263 K, toluene-d₈) δ 9.5, 9.3; IR (THF): 1978, 1922 (ν_CO); MS

(EI) m/z 592 [M]⁺, 536 [M - 2CO]⁺, 402 [M - Cp′(CO)₂Mn]⁺.

Anal. Calcd for C₃₆H₄₂MnO₂P: C, 72.96; H, 7.14. Found: C, 73.01;

H, 7.51.

and MeC₆H₄), 6.24 (d, 1H, H_ꢀ, J_HP) 9 Hz), 4.40–3.64 (m, 4H,

MeC₆H₄), 2.41 (s, 3H, MeC₆H₄), 1.88 (s, 3H, MeC₅H₄); ¹³C{¹H}

NMR (100.6 MHz, 233 K, CD₂Cl₂) δ 237.4, 232.0 (CO),

3

142.9–124.8 (C₆H₅and MeC₆H₄), 101.3, 89.7, 88.5 (d, J_CP) 2

Hz), 86.4 (d, ³J_CP) 2 Hz), 86.1 (d, ³J_CP) 2 Hz) (MeC₅H₄), 83.3

(d, C_ꢀ, ²J_CP) 33 Hz), 73.9 (d, C_η, ¹J_CP) 32 Hz), 29.1 (d, C_R, ³J_CP

) 8 Hz), 21.4 (MeC₆H₄), 13.6 (MeC₅H₄); ³¹P{¹H} NMR (121.5

MHz, 233 K, CD₂Cl₂) δ 18.4; MS (EI) m/z 580 [M]⁺, 552 [M -

CO]^+., 524 [M - 2CO]⁺; IR (CH₂Cl₂): 1961, 1724 (η_CO). Anal.

Calcd for C₃₆H₃₀MnO₂P: C, 74.47; H, 5.21. Found: C, 74.35; H,

5.23.

1

anti-4b: H NMR (500.3 MHz, 223 K, CD₂Cl₂) δ 7.8–6.5 (m,

MeC₆H₄and C₆H₅), 4.53, 4.43, 4.28, 3.89 (m, 4H, MeC₅H₄), 3.61

(s, 1H, H_R), 2.29 (s, 3H, MeC₆H₄), 1.61 (s, MeC₅H₄), 2.0–0.9

(C₁₁H₂₂); ¹³C{¹H} NMR (125.8 MHz, 213 K, CD₂Cl₂) δ 233.4,

syn-3a: ¹H NMR (400.1 MHz, CD₂Cl₂) δ 8.72 (s, 1H, H_η),

8.8–6.9 (m, C₆H₅and MeC₆H₄), 4.52, 4.46, 3.96, 3.17 (m, 4H,

MeC₅H₄), 2.45 (s, 3H, MeC₆H₄), 1.96 (s, 3H, MeC₅H₄); ¹³C{¹H}

NMR (100.6 MHz, CD₂Cl₂) δ 236.5 (d, ³J_PC) 16 Hz), 228.9 (CO),

165.1 (d, C_ꢀ, ²J_CP) 7 Hz), 147.0–124.5 (C₆H₅and MeC₆H₄), 126.2

2

230.1 (CO), 182.5 (d, C_ꢀ, J_CP) 28 Hz), 143.1–125.2 (MeC₆H₄

1

and C₆H₅), 131.4 (d, C_γ, J_CP) 34 Hz), 101.5, 86.8, 86.7, 85.3,

3

84.7, (MeC₅H₄), 35.4–26.4 (C₁₁H₂₂), 27.4 (d, C_R, J_CP) 13 Hz),

21.1 (s, MeC₆H₄), 12.8 (s, η⁵-MeC₅H₄); ³¹P{¹H} NMR (121 MHz,

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2089

298 K, toluene-d₈) δ 33.2; ³¹P{¹H} NMR (121.5 MHz, 213 K,

toluene-d₈) δ 31.8, 30.4; IR (THF) 1978, 1922 (ν_CO); MS (EI) m/z

592 [M]⁺, 536 [M - 2CO]⁺, 402 [M - Cp′(CO)₂Mn]⁺. Anal.

Calcd for C₃₆H₄₂MnO₂P: C, 72.96; H, 7.14. Found: C, 72.98; H,

7.00.

Synthesis of Complexes Cp′(CO)₂Mn[η¹-{Ph₂P(Tol)CdCd

C(Ph)H} (5a), Cp′(CO)₂Mn[η¹-{Ph₂P(Ph)CdCdC(Tol)H}] (6a),

and (η⁵-MeC₅H₅)(CO)₂Mn[η²-Cy₂P(Ph)CdCdC(Tol)H}] (6b). In

a

typical experiment, a

solution of syn-Cp′(CO)₂Mn[η²-

{Ph₂P(Tol)CdCdC(Ph)H}] (syn-3a, 0.580 g, 1 mmol) in THF (10

mL) was heated under reﬂux for 2 h, the time after which an IR

monitoring showed total disappearance of syn-3a and the formation

of a new complex. Heating was stopped, the solvent was removed

under vacuum, and the yellow residue was treated by column

chromatography on alumina. Elution with a 5:100 ether/pentane

mixture afforded a pale yellow band containing Cp′(CO)₂Mn[η¹-

{Ph₂P(Tol)CdCdC(Ph)H}] (5a), which was subsequently isolated

as a pale yellow powder after removal of the solvents under high

vacuum (0.480 g, 0.82 mmol, 82%).

Formation of Cp′(CO)₂Mn[η²-{Ph₂P(Tol)CdCdC(Ph)H}]

(syn-3a) and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)PPh₂}] (4a)

upon Reaction of 1 with LiPPh₂Followed by Protonation

withNH₄Cl_aq. ATHFsolutionoflithiumdiphenylphosphidesgenerated

in situ by addition of ⁿBuLi (0.850 mL of a 1.6 M solution in

hexane, 1.36 mmol) to a solution of HPPh₂(0.190 mL, 1.1 mmol)

in THF (3 mL) at 0 °Cswas added dropwise to a solution of

complex Cp′(CO)₂MndC(Tol)CtCPh (1, 0.394 g, 1 mmol) in THF

(20 mL) at –80 °C. The solution turned orange. A saturated solution

of NH₄Cl (ca. 0.2 mL) in water was then added. After stirring the

solution for 2 min, the cold bath was removed, 10 mL of diethyl

ether was added, and the organic phase was transferred into another

Schlenk ﬂask by mean of a canula. The solvents were removed

under high vacuum, and the oily yellow residue was puriﬁed by

chromatography on alumina. An initial elution with a 1:4 diethyl

ether/pentane mixture gave a yellow band. Removal of the solvents

under high vacuum left a yellow foam (0.435 g, 0.75 mmol, 75%

yield). NMR analysis showed the foam to contain 86% of

Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)PPh₂}] (4a), 12% of isomer

Cp′(CO)₂Mn[η²-{Ph₂P(Tol)CdCdC(Ph)H} (syn-3a), and ca. 2%

of an impurity that may correspond to a second isomer of 4a.

A similar experiment carried out from 0.580 g (1 mmol) of a

ca. 9:1 mixture of 4a and syn-3a (Vide supra) afforded a ca. 9:1

mixture of complexes Cp′(CO)₂Mn[η¹-{H(Tol)CdCdC(Ph)PPh₂}]

(6a) and Cp′(CO)₂Mn[η¹-{H(Tol)CdCdC(Ph)PPh₂}] (5a) (0.419

mg, 0.72 mmol, 72% yield).

Similar treatment of complex 4b (as a 1:2 mixture of syn/anti

isomer) afforded complex Cp′(CO)₂Mn[η¹-{H(Tol)CdCdC-

(Ph)PCy₂}] (6b) in 86% yield.

5a: ¹H NMR (500.3 MHz, 298 K, CD₂Cl₂) δ 7.7–7.2 (MeC₆H₄

and C₆H₅), 6.23 (d, 1H, dC(Ph)H, J_PH) 5 Hz), 4.11, 4.06 (m,

4H, MeC₅H₄), 2.33 (s, 3H, MeC₆H₄), 1.89 (s, 3H, MeC₅H₄);

¹³C{¹H} NMR (125.8 MHz, 298 K, CD₂Cl₂) δ 232.8, 232.7 (CO),

209.4 (d, C_ꢀ, ²J_CP) 3 Hz), 138.5–127.1 (C₆H₅and MeC₆H₄), 108.1

(d, C_R, ¹J_CP) 29 Hz), 99.3, 83.6, 83.4, 81.5, 81.4 (MeC₅H₄), 96.5

(d, C_γ, ³J_CP) 9 Hz), 20.9 (MeC₆H₄), 13.5 (MeC₅H₄); ³¹P{¹H} NMR

(202.6 MHz, 298 K, CD₂Cl₂) δ 96.7; IR (THF) 1934, 1872 (ν_CO);

MS (CI) m/z 581 [MH]⁺, 391 [MH - Cp′(CO)₂Mn]⁺. Anal. Calcd

for C₃₆H₃₀MnO₂P: C, 74.48; H, 5.21. Found: C, 74.45; H, 5.06.

4a (from a 4a:syn-3a mixture): ¹H NMR (300.1 MHz, CD₂Cl₂,

303 K) δ 7.6–7.1 (m, MeC₆H₄and C₆H₅), 5.0–4.7 (m, MeC₅H₄),

4.00 (s, H_R), 2.35 (s, MeC₆H₄), 2.05 (s, MeC₅H₄); ¹³C{¹H} NMR

(75.5 MHz, CD₂Cl₂) δ 232.1, 230.2 (CO), 189.2 (d, ²J_CP) 53 Hz,

1

C_ꢀ), 143.3–129.4 (MeC₆H₄and C₆H₄), 132.6 (d, J_CP) 45 Hz,

3

C_η), 103.3, 90.4, 89.3, 87.2, 86.1 (MeC₅H₄), 29.1 (d, J_CP) 15

1

6a (from a ca. 9:1 mixture of 6a and 5a): ¹H NMR (500.3 MHz,

298 K, CD₂Cl₂) δ 7.7–7.2 (MeC₆H₄and C₆H₅), 6.23 (d, 1H,

dC(Ph)H, J_PH) 5 Hz), 4.07 (m, MeC₅H₄), 2.39 (s, 3H, MeC₆H₄),

1.90 (s, MeC₅H₄); ¹³C{¹H} NMR (125.8 MHz, 298 K, CD₂Cl₂) δ

232.8, 232.6 (CO), 209.7 (d, C_ꢀ, ²J_CP) 3 Hz), 137.1–126.4 (C₆H₅

and MeC₆H₄), 108.2 (d, C_γ, ¹J_CP) 30 Hz), 99.3, 83.5, 83.3, 81.56,

Hz, C_R), 21.0 (MeC₆H₄), 13.3 (MeC₅H₄); H NMR (500.3 MHz,

CD₂Cl₂, 253 K) δ 7.9–6.9 (m, C₆H₅and MeC₆H₄), 5.02, 4.97, 4.88,

4.78 (m, MeC₅H₄, major rotamer), 4.95, 4.67, 4.03, 3.61 (m,

MeC₅H₄, minor rotamer), 4.05 (s, H_R, major), 3.96 (s, H_R, minor),

2.31 (s, MeC₆H₄, minor), 2.29 (s, MeC₆H₄, major), 2.00 (s,

MeC₅H₄); ¹³C{¹H} NMR (125.8 MHz, CD₂Cl₂, 253 K) δ 232.1,

230.2 (CO, minor), 235.3, 229.9 (CO, major), 191.1 (d, C_ꢀ, ²J_CP

)

3

81.3 (MeC₅H₄), 96.5 (d, C_R, J_CP) 9 Hz), 20.9 (MeC₆H₄), 13.5

2

(MeC₅H₄); ³¹P{¹H} NMR (202.6 MHz, 298 K, CD₂Cl₂) δ 97.0;

IR (THF) 1934, 1871 (ν_CO); HRMS calcd for [C₃₆H₃₁MnO₂P]⁺m/z

581.1442, found m/z 581.1444.

53 Hz, major), 189.7 (d, C_ꢀ, J_CP) 53 Hz, minor), 143.5–125.5

(C₆H₅and MeC₆H₄), 132.6 (d, C_γ, ¹J_CP) 20 Hz, major), 132.3 (d,

1

C_γ, J_CP) 20 Hz, minor), 103.3, 90.4–87.2 (MeC₅H₄), 30.9 (d,

C_R, ³J_CP) 15 Hz, minor). 28.4 (d, C_R, ³J_CP) 15 Hz, major), 21.0

(MeC₆H₄), 13.3 (MeC₅H₄); ³¹P{¹H} NMR (121.5 MHz, toluene-

d₈, 303 K) δ 8.5 (minor), 6.0 (major); IR (THF) 1975, 1925 (ν_CO);

MS (CI) m/z 581 [MH]⁺, 525 [MH - 2CO]⁺, 391 [MH -

Cp′(CO)₂Mn]⁺. Anal. Calcd for C₃₆H₃₀MnO₂P: C, 74.47; H, 5.21.

Found: C, 74.62; H, 5.03.

6b: ¹H NMR (300.1 MHz, 298 K, CD₂Cl₂) δ 7.6–7.2 (MeC₆H₄

and C₆H₅), 6.45 (d, 1H, dC(Ph)H, J_PH) 6 Hz), 4.2–4.0 (m, 4H,

MeC₅H₄), 2.37 (s, 3H, MeC₆H₄), 1.89 (s, MeC₅H₄), 2.1–0.9 (m,

C₆H₁₁); ¹³C{¹H} NMR (75.5 MHz, 298 K, CD₂Cl₂) δ 234.4, 234.1

(CO), 207.7 (d, C_ꢀ, ²J_CP) 3 Hz), 137.5–126.9 (C₆H₅and MeC₆H₄),

105.9 (d, C_γ, ¹J_CP) 25 Hz), 98.1, 82.3, 82.2, 80.7, 80.7 (MeC₅H₄),

94.6 (d, C_R, ³J_CP) 7 Hz), 20.9 (MeC₆H₄), 13.5 (MeC₅H₄); ³¹P{¹H}

NMR (121.5 MHz, 298 K, CD₂Cl₂) δ 99.6; IR (THF) 1918, 1856

(ν_CO); MS (CI) m/z 593 [MH]⁺, 403 [ΜΗ⁺- Cp′Mn(CO)₂]⁺.

Anal. Calcd for C₃₆H₄₂MnO₂P: C, 72.96; H, 7.15. Found: C, 73.16;

H, 7.24.

Synthesis of Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)PCy₂}] (4b)

upon Reaction of 1 with LiPPh₂Followed by Protonation with

NH₄Cl_aq. A THF solution of lithium dicyclohexylphosphides

generated in situ by addition of ⁿBuLi (0.690 mL of a 1.6 M solution

in hexane, 1.1 mmol) to a solution of HPCy₂(0.220 mL, 1.1 mmol)

in THF (3 mL) at 0 °Cswas added dropwise to a solution of complex

Cp′(CO)₂MndC(Tol)CtCPh (1, 0.394 g, 1 mmol) in THF (20 mL)

at –80 °C. The solution turned orange. A saturated solution of NH₄Cl

(ca. 0.2 mL) in water was then added. After stirring the solution for 2

min, the cold bath was removed, 10 mL of diethyl ether was added,

and the organic phase was transferred into another Schlenk ﬂask by

mean of a canula. The solvents were removed under high vacuum,

and the oily yellow residue was puriﬁed by chromatography on

alumina. Elution with a 1:10 diethyl ether/pentane mixture gave a

yellow band. Removal of the solvents under high vacuum left 4b as

a yellow foam (0.480 g, 0.81 mmol, 81% yield). NMR analysis showed

the foam to contain pure Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)-

PCy₂}] (4b) as a 1:2 mixture of syn and anti isomers.

SynthesisofPh₂P(Tol)CdCdC(Ph)H(7a),Ph₂P(Ph)CdCdC-

(Tol)H (9a), and Cy₂P(Ph)CdCdC(Tol)H (9b). In a typical

experiment, complex syn-Cp′(CO)₂Mn[η²-{Ph₂P(Ph)CdCdC-

(H)Tol}] (syn-3a) (0.348 g, 0.6 mmol) was dissolved in dichlo-

romethane (90 mL) and introduced into a Pyrex photolysis reactor

equipped with a medium-pressure Hereaus TQ150 Hg lamp. The

solution was irradiated for 45 min. From golden yellow, the solution

turned colorless and showed a white suspension. After removal of

the dichloromethane under vacuum, the residue was extracted with

diethyl ether (10 mL) and ﬁltered through a short column of alumina

(10 × 2.5 cm) eluting with pure diethyl ether. After removal of

the solvent, the phosphine Ph₂P(Ph)CdCdC(H)Tol (7a) was

obtained as a pale yellow oil (0.170 g, 91% yield).

2090 Organometallics, Vol. 27, No. 9, 2008

Sentets et al.

A similar experiment carried out with 0.435 mg (0.75 mmol) of

a ca. 9:1 mixture of 4a and syn-3a (Vide supra) afforded a ca. 9:1

mixture of Ph₂P(Ph)CdCdC(Tol)H (9a) and Ph₂P(Tol)CdCdC-

(Ph)H (7a) (268 mg, 91% yield).

diethyl ether/pentane mixture afforded a pale yellow band containing

complex [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Ph)CdCdC(Tol)H}] (10a),

which was subsequently isolated as a pale yellow powder (275 mg

; 48% yield). Considering the sample we have used contained traces

of 5a, 10a should logically be contaminated by traces of 8a, which,

however, could not be clearly identiﬁed.

10a: ¹H NMR (500.3 MHz, CD₂Cl₂, 263 K) δ 7.6–6.2 (MeC₆H₄

and C₆H₅), 4.6–3.4 (m, 4H, MeC₅H₄), 2.93 (s(br), 1H, C_γ), 2.21 (s,

3H, MeC₅H₄), 1.81 (s, 3H, MeC₅H₄), 1.77 (s, 3H, MeC₅H₄);

¹³C{¹H} NMR (125.8 MHz, CD₂Cl₂, 273 K) δ 234.8, 233.9, 231.9,

231.0 (CO), 180.1 (C_ꢀ), 143.1–126.1 (C₆H₅and MeC₆H₄), 98.7–80.9

(MeC₅H₄), 30.4 (C_R), 20.8 (MeC₆H₄), 13.6 (MeC₅H₄), 13.1

(MeC₅H₄); ³¹P{¹H} NMR (202.6 MHz, CD₂Cl₂, 273 K) δ 105.1;

IR (THF) 1975(m), 1922(s), 1857(m) (ν_CO); MS (CI) m/z 771

[MH]⁺, 581 [MH - Cp′Mn(CO)₂]⁺. Anal. Calcd for C₄₄H₃₇Mn₂-

O₄P: C, 68.56; H, 4.84. Found: C, 68.50; H, 4.75.

Synthesis of [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Ph)CdCdC(Tol)H}]

(10a) from 4a. A solution of a ca. 9:1 mixture of 4a and syn-3a

(0.290 g, 0.5 mmol) in solution in THF (10 mL) was added

dropwise to a solution of Cp′Mn(CO)₂(THF)sgenerated extem-

poraneously by UV irradiation of Cp′Mn(CO)₂(0.436 g, 2 mmol)

in THF (100 mL)sin THF. After stirring for 1 h, the solvent was

removed under vacuum, and the solid residue was treated by column

chromatography on alumina as above. Complex [Cp′(CO)₂Mn]₂[µ-

η³-{Ph₂P(Ph)CdCdC(Tol)H}] (10a) was subsequently isolated as

a pale yellow powder (0.220 g, 57% yield). Considering the sample

we have used contained traces of syn-2a, 10a should logically be

contaminated by trace amounts of 8a, which, however, could not

be clearly identiﬁed.

Formation of syn-Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC(Ph)H}]

(syn-11) and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)STol}] (12)

upon Reaction of 1 with p-Toluenethiol. Triethylamine (0.030 mL,

0.20 mmol) was added to a solution containing complex

Cp′(CO)₂MndC(Tol)CCPh (1, 0.394 mg, 1 mmol) and p-tolu-

enethiol (0.136 mg, 1.1 mmol) cooled at –80 °C. After 45 min of

reaction, the solution turned light brown. The cooling bath was

removed and stirred an additional 30 min. The solvent was removed

under high vacuum, and the solid residue was treated by column

chromatography. Elution with a 4:96 mixture of diethyl ether/hexane

mixture afforded a yellow band. Removal of the solvents under

high vacuum left a yellow foam. NMR analysis showed the foam

to consist of a 1.8:1 mixture of Cp′(CO)₂Mn[η²-{TolS(Tol)Cd

CdC(Ph)H}] (syn-11) and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)-

STol}] (12) (0.336 g, 0.65 mmol, 65% yield). Complex syn-11 was

eventually obtained in a pure form upon crystallization from a

diethyl ether/hexane mixture in the cold; some crystals were suitable

for an X-ray structure determination.

Similar treatment of complex 4b (as 1:2 mixture of syn/anti

isomer) afforded Cy₂P(Ph)CdCdC(Tol)H (9b) in 83% yield.

7a: ¹H NMR (300.1 MHz, CD₂Cl₂) δ 7.6–7.1 (MeC₆H₄and

C₆H₅), 6.50 (s, 1H, H_γ), 2.35 (s, 3H, MeC₅H₄); ¹³C{¹H} NMR (75.5

MHz, C₆D₆) δ 209.1 (C_ꢀ), 137.5–126.5 (MeC₆H₄and C₆H₅), 106.30

(d, C_R, ¹J_CP) 20 Hz), 96.37 (d, C_γ, ³J_CP) 2 Hz), 20.83 (MeC₆H₄);

³¹P{¹H} NMR (121.5 MHz, CD₂Cl₂) δ –10.8; HRMS calcd for

[C₂₈H₂₄P]⁺m/z 391.1616, found m/z 391.1697.

9a: ¹H NMR (300.1 MHz, CD₂Cl₂) δ 7.7–7.0 (MeC₆H₄and

C₆H₅), 6.18 (s, 1H, H_R), 2.42 (s, 3H, MeC₅H₄); ¹³C{¹H} NMR (75.5

MHz, CD₂Cl₂) δ 209.9 (C_ꢀ), 137.0–126.4 (MeC₆H₄and C₆H₅),

1

3

106.3 (d, C_γ, J_CP) 20 Hz), 94.7 (d, C_R, J_CP) 3 Hz), 20.9

(MeC₆H₄); ³¹P{¹H} NMR (121.5 MHz, C₆D₆) δ –10.6; HRMS

Calcd for [C₂₈H₂₄P]⁺m/z 391.1616, found m/z 391.1632.

9b: ¹H NMR (300.1 MHz, CD₂Cl₂) δ 7.4–7.2 (MeC₆H₄and

C₆H₅), 6.51 (s, 1H, H_R), 2.42 (s, 3H, MeC₅H₄), 2.2–1.2 (m, C₆H₁₁);

¹³C{¹H} NMR (75.5 MHz, CD₂Cl₂) δ 209.5 (C_ꢀ), 139.0–125.3

1

(MeC₆H₄and C₆H₅), 102.7 (d, C_γ, J_CP) 29 Hz), 94.7 (C_γ),

34.0–26.5 (C₆H₁₁), 21.0 (MeC₆H₄); ³¹P{¹H} NMR (121.5 MHz,

CD₂Cl₂) δ –5.1; HRMS calcd for [C₂₈H₃₆P]⁺m/z 403.2555, found

403.2549.

Synthesis of [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Tol)CdCdC(Ph)H}]

(8a) from 5a. A solution of 5a (0.290 mg, 0.5 mmol) in solution in

THF (10 mL) was added dropwise to a solution of (η⁵-

MeC₅H₅)Mn(CO)₂(THF)sgenerated extemporaneously by UV ir-

radiation of (η⁵-MeC₅H₅)Mn(CO)₂(0.436 g, 2 mmol) in THF (100

mL)sin THF. After stirring for 1 h, the solvent was removed under

vacuum, and the solid residue was treated by column chromatog-

raphy on alumina. Elution with pure pentane afforded (η⁵-

MeC₅H₅)Mn(CO)₃, which was discarded. A second elution with a

1:10 diethyl ether/pentane mixture afforded a pale yellow band

containing complex [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Tol)CdCdC-

(Ph)H}] (8a), which was subsequently isolated as a pale yellow

powder (0.250 g, 66% yield).

8a: ¹H NMR (500.3 MHz, CD₂Cl₂, 273 K) δ 7.7–6.5 (MeC₆H₄

and C₆H₅), 4.7–3.4 (m, 4H, MeC₅H₄), 2.87 (s(br), 1H, C_γ), 2.48 (s,

3H, MeC₅H₄), 1.81 (s, 3H, MeC₅H₄), 1.77 (s, 3H, MeC₅H₄);

¹³C{¹H} NMR (125.8 MHz, CD₂Cl₂, 273 K) δ 234.9, 233.8, 232.0,

230.6 (CO), 179.4 (C_ꢀ), 144.5–124.7 (C₆H₅and MeC₆H₄), 134.0

(C_γ), 101.2–80.9 (MeC₅H₄), 30.2 (C_R), 21.1 (MeC₆H₄), 13.6

(MeC₅H₄), 13.1 (MeC₅H₄); ³¹P{¹H} NMR (202.6 MHz, CD₂Cl₂,

273 K) δ 105.5; IR (THF) 1975(m), 1922(s), 1857(m) (ν_CO); MS

(CI) m/z 771 [MH]⁺, 581 [MH⁺- Cp′Mn(CO)₂]⁺. Anal. Calcd

for C₄₄H₃₇Mn₂O₄P: C, 68.56; H, 4.84. Found: C, 68.91; H, 4.65.

Synthesis of [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Tol)CdCdC(Ph)H}]

(8a) from syn-3a. A solution of syn-3a (357 mg, 0.62 mmol) in

solution in THF (10 mL) was added dropwise to a solution of

Cp′Mn(CO)₂(THF)sgenerated extemporaneously by UV irradiation

of Cp′Mn(CO)₂(0.436 g, 2 mmol) in THF (100 mL)sin THF. After

stirring for 1 h, the solvent was removed under vacuum, and the

solid residue was treated by column chromatography on alumina,

as above. Complex [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Tol)CdCdC-

(Ph)H}] (8a) was subsequently isolated as a pale yellow powder

(0.265 g, 56% yield).

Synthesis of [Cp′(CO)₂Mn]₂[µ-η³-{Ph₂P(Ph)CdCdC(Tol)H}]

(10a) from 6a. A solution of a ca. 9:1 mixture of mixture 6a and

5a (0.406 g, 0.70 mmol) in solution in THF (10 mL) was added

dropwise to a solution of Cp′Mn(CO)₂(THF)sgenerated extem-

poraneously by UV irradiation of Cp′Mn(CO)₂(0.436 g, 2 mmol)

in THF (100 mL)sin THF. After stirring for 1 h, the solvent was

removed under vacuum, and the solid residue was treated by column

chromatography on alumina. Elution with pure pentane afforded

Cp′Mn(CO)₃, which was discarded. A second elution with a 1:10

1

syn-11: H NMR (500.3 MHz, 253 K, CD₂Cl₂) δ 8.21, 7.74 (s,

dC(Ph)H), 7.9–7.0 (m, MeC₆H₄and C₆H₅), 4.9–4.0 (m, MeC₅H₄),

2.27, 2.15, 2.09, 1.86 (MeC₆H₄and MeC₅H₄); ¹³C{¹H} NMR (125.8

MHz, 253 K, CD₂Cl₂) δ 234.2, 233.1, 228.1 (CO), 172.4, 167.4

(C_ꢀ), 143.4–126.6 (C₆H₅,and MeC₆H₄), 125.5, 125.0 (C_γ), 104.3,

103.2, 95.5–81.3 (MeC₅H₄), 39.4, 39.1 (C_R), 30.9, 20.9 (MeC₆H₄),

13.5, 13.0 (MeC₅H₄); IR (CH₂Cl₂) 1920, 1972 (ν_CO); MS (CI) m/z

536.3 [MNH₄]⁺, 519.3 [MH]⁺, 463.3 [MH - 2CO]⁺, 329.3 [MH

- 2CO - Cp′(CO)₂Mn]⁺. Anal. Calcd for MnC₃₁H₂₇O₂S: C, 71.80;

H, 5.24. Found: C, 72.03; H, 5.08.

1

12 (from a 12:syn-11 mixture): H NMR (500.3 MHz, 293 K,

CD₂Cl₂) δ 8.36, 7.84 (s, dC(Ph)H), 7.8–6.7 (m, MeC₆H₄and C₆H₅),

4.7–4.6 (m, MeC₅H₄), 2.29, 1.97 (MeC₆H₄and MeC₅H₄); ¹³C{¹H}

NMR (125.8 MHz, 213 K, CD₂Cl₂) δ 234.3–228.3 (CO), 172.5,

167.4 (C_ꢀ), 139.1–125.4 (MeC₆H₄and C₆H₅), 123.9, 123.3 (C_γ),

97.2–80.8 (MeC₅H₄), 33.4, 32.1 (C_R), 21.3, 21.0 (MeC₆H₄and

MeC₆H₄), 13.8, 13.2 (MeC₅H₄); IR (CH₂Cl₂) 1920, 1972 (ν_CO).

Directed Formation of Allene Complexes

Organometallics, Vol. 27, No. 9, 2008 2091

Formation of syn-Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC(Ph)H}]

(syn-11) and Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)STol}] (12)

upon Reaction of 1 with p-Toluenethiolate followed by Proto-

nation. A THF solution of lithium p-toluenethiolatesgenerated in

situ by addition of ⁿBuLi (0.690 mL of a 1.6 M solution in hexane,

1.1 mmol) to a solution of TolSH (0.136 g, 1.1 mmol) in THF (3

mL) at 0 °Cswas added dropwise to a solution of complex Cp′(CO)₂-

MndC(Tol)CtCPh (1, 0.394 mg, 1 mmol) in THF (20 mL) at

–80 °C. The solution turned orange (IR (ν_CO): 1883(s), 1806(m);

1765(m) cm^-1). A saturated solution of NH₄Cl (ca. 0.2 mL) in

water was then added. After stirring the solution for 2 min, the

cold bath was removed, 10 mL of diethyl ether was added, and the

organic phase was transferred into another Schlenk ﬂask by means

of a canula. The solvent was removed under high vacuum and the

solid residue was treated by column chromatography. Elution with

a 4:96 of diethyl ether/hexane mixture afforded a yellow band.

Removal of the solvents under high vacuum left a yellow foam.

NMR analysis showed the foam to consist of a 1:2.3 mixture of

Cp′(CO)₂Mn[η²-{TolS(Tol)CdCdC(Ph)H}](syn-11)andCp′(CO)₂Mn[η²-

{H(Tol)CdCdC(Ph)STol}] (12) (0.386 g, 0.72 mmol, 72% yield).

211.5 (CdO), 167.8 (C_ꢀ), 143.5–125.4 (C₆H₅and MeC₆H₄), 126.7

(C_γ), 102.7, 87.9–84.0 (MeC₅H₄), 61.1 (CH(CH₂)₄C(O)), 42.2, 32.7,

26.0, 25.4 (CH₂), 30.3 (C_R), 20.8 (MeC₆H₄), 12.6 (MeC₅H₄); IR

(THF) 1975(s), 1913(s), 1708(w) (ν_CO); MS (CI) m/z 510 [MNH₄]⁺,

468 [MH]⁺, 320, [MNH₄- Cp′(CO)₂Mn]⁺. Anal. Calcd for

C₃₀H₂₉MnO₃: C, 73.16; H, 5.93. Found: C, 72.98; H, 6.20.

X-ray Diffraction Studies. Crystals of 2a, syn-4b, anti-4b, syn-

11, and syn-13 suitable for X-ray diffraction were obtained through

recrystallization from dichloromethane/hexane (3a) or diethyl ether/

hexane (syn-4b, anti-4b, syn-11, and syn-13) solutions in the cold.

Data were collected on a Stoe IPDS (2a), Oxford Diffraction

Xcalibur (syn-4b, anti-4b, syn-11), or Bruker Kappa (syn-13)

diffractometer. All calculations were performed on a PC-compatible

computer using the WinGX system.³⁵Full crystallographic data

are given in Table 1. The structures were solved by using the SIR92

program,³⁶which revealed in each instance the position of most

of the non-hydrogen atoms. All remaining non-hydrogen atoms were

located by the usual combination of full matrix least-squares

reﬁnement and difference electron density syntheses by using the

SHELXL97 program.³⁷Atomic scattering factors were taken from

the usual tabulations. Anomalous dispersion terms for Mn and P

atoms were included in F_c. All non-hydrogen atoms were allowed

to vibrate anisotropically. All the hydrogen atoms were set in

idealized position (R₃CH, C-H ) 0.96 Å; R₂CH₂, C-H ) 0.97

Å; RCH₃, C-H ) 0.98 Å; C(sp²)-H ) 0.93 Å; U_iso1.2 or 1.5

time greater than the U_eqof the carbon atom to which the hydrogen

atom is attached), and their positions were reﬁned as “riding” atoms.

The cyclohexyl rings in the structure of complex syn-4b were found

to be disordered; each set of rings were reﬁned with structure factor

occupancy of 0.5.

Synthesis of syn-Cp′(CO)₂Mn[η²-{H(Tol)CdCdC(Ph)CH-

(CH₂)₄C(O)}] (syn-13). A THF solution of lithium 2-cyclohexanone

enolatesgenerated extemporaneously by addition of ⁿBuLi (0.690

mL of a 1.6 M solution in hexane, 1.1 mmol) to a solution of

trimethylsilyloxycyclohexene (0.220 mL, 1.1 mmol) in THF (5 mL)

at

0 °Cswas added dropwise to a solution of complex

Cp′(CO)₂MndC(Tol)CtCPh (1, 0.394 mg, 1 mmol) in THF (20

mL) at –80 °C. The cooling bath was removed and the solution

left for 2 h under stirring. The solution turned yellow-greenish (IR

(ν_CO) 1875(s), 1805(m), 1770(m) cm^-1). A saturated solution of

NH₄Cl (ca. 0.2 mL) in water was then added. After the solution

stirred for 2 min, 10 mL of diethyl ether was added, and the organic

phase was transferred into another Schlenk ﬂask by means of a

canula. The solvent was removed under high vacuum and the solid

residue was treated by column chromatography. A ﬁrst elution with

a 5:100 mixture of diethyl ether/hexane afforded a pale yellow band

containing traces of Cp′(CO)₂Mn, which was discarded. A second

elution with a 10:100 mixture of diethyl ether/hexane afforded an

orange band. Removal of the solvents under high vacuum left complex

syn-Cp′(CO)₂Mn[η²-{Tol(H)CdCdC(Ph)CH(CH₂)₄C(O)}] (syn-13)

as an orange foam (0.304 g, 0.61 mmol, 61% yield).

Acknowledgment. We thank the Ministère de l’Education

Nationale for a fellowship to S.S. and Ethyl Corporation

(USA) for a generous gift of Cp′Mn(CO)₃.

Supporting Information Available: This material is available

free of charge via the Internet at http://pubs.acs.org.

OM800060V

(35) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.

(36) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J. Appl.

Crystallogr. 1993, 26, 343.

(37) Sheldrick, G. M. SHELX97 [Includes SHELXS97, SHELXL97,

CIFTAB], Programs for Crystal Structure Analysis (Release 97-2); Institüt

für Anorganische Chemie der Universität: Göttingen, Germany, 1998.

1

syn-13: H NMR (300.1 MHz, 293 K, CD₂Cl₂) δ 7.3–6.8 (m,

C₆H₅and MeC₆H₄), 4.8–4.5 (MeC₅H₄and CH(CH₂)₄C(O)), 3.85

(s(br), 1H H_R), 2.6–1.8 (CH₂), 2.26 (MeC₆H₄), 1.94 (MeC₅H₄);

¹³C{¹H} NMR (75.5 MHz, 293 K, CD₂Cl₂) δ 232.09, 231.02 (CO),

Article Doi

Directed formation of allene complexes upon reaction of non-heteroatom-substituted manganese alkynyl carbene complexes with nucleophiles

DOI: 10.1021/om800060v

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