Reactivity patterns of carbyne hydride complexes of tungsten

Organometallics 2000, 19, 3605-3619

3605

Rea ctivity P a tter n s of Ca r byn e Hyd r id e Com p lexes of

Tu n gsten

Ewald Bannwart, Heiko J acobsen, Franck Furno, and Heinz Berke*

Anorganisch-chemisches Institut der Universita¨t Zu¨rich, Winterthurerstrasse 190,

CH-8057 Zu¨rich, Switzerland

Received February 11, 2000

Tungsten carbyne chlorides of the type W(CMes)(CO)(Cl)L₂L′ (L ) P(OMe)₃, L′ ) CO (2a );

L ) PMe₃, L′ ) CO (2b); L ) P(OⁱPr)₃, L′ ) pyridine (py) (2c); L dPPh₃, L′ ) CO (2d ); 2L

) Ph₂PCH₂CH₂PPh₂, L′ ) CO (2e)), W(CMes)(CO)(Cl)L₃(L ) P(OMe)₃(3a ); L ) PMe₃(3b);

3L ) Ph₂PCH₂CH₂)₂PPh (3d )), and W(CMes)(Cl)L₄(L ) P(OMe)₃(4a )) have been prepared

by starting from W(CMes)(CO)₂(Cl)(py)₂(1). Treatment of the chloride complexes with NaBH₄

in THF furnished the borohydride adducts W(η²-H₂BH₂)(CMes)(CO)L₂(L ) P(OMe)₃(5a ); L

) PMe₃(5b); L ) P(OⁱPr)₃(5c); L dPPh₃(5d )) and W(η²-H₂BH₂)(CMes)L₃(L ) P(OMe)₃

(6a )), which served as precursors for new tungsten carbyne hydrides. The compounds

W(CMes)(CO)(H)L₃(L ) P(OMe)₃(7a ); L ) PMe₃(7b); 3L ) (Ph₂PCH₂CH₂)₂PPh (7d )) and

W(CMes)(H)L₄(L ) P(OMe)₃(8a )) were obtained from the reaction of the borate complexes

5a ,b,d and 6a with quinuclidine in THF at -20 °C in the presence of excess phosphorus

donor ligands. The hydrides can be kept and characterized at low temperatures but

decompose when warmed to room temperature. The reactivity of this novel class of compounds

has been investigated for 7a , which reacts even at low temperatures with phenol, carbon

dioxide, and unsaturated organic compounds. In the presence of excess phosphorus donor

ligands or CO, 7a rearranges into the carbene complexes W(CHMes)(CO)(L)(L′)(P(OMe)₃)₂

(L ) L′ ) P(OMe)₃(15a ); L ) L′ ) PMe₃(15b); L ) P(OMe)₃, L′ ) CO (16)) via intramolecular

hydride migration. A similar reaction could not be observed for 7d or 8a . Density functional

calculations support the notion that this transformation is initiated by ligand dissociation

and that formyl species are not likely to occur as reaction intermediates. Reaction of 3a

with HCl provides access to another carbene complex, W(CHMes)(Cl)₂(CO)(P(OMe)₃)₂(17).

It was concluded from NMR spectroscopy that the carbene ligand in the d⁴complex 17 pivots

in place to establish an η²-type coordination with an agostic interaction.

In tr od u ction

additional enhancement of the a priori hydridic polar-

ization of the L_nM-H bond. Qualitative MO consider-

ations provide a clear explanation for this effect. The

interaction diagram for the formation of the M-H bond

is presented in Chart 1. As a result of second-order

In recent years our group has studied the chemistry

of activated transition-metal hydrides. In this context,

systematic investigations were carried out on how

ancillary ligands might activate the transition-metal-

hydrogen bond. It could be shown that the nitrosyl

ligand plays an outstanding role in the electronic

activation of hydride units,¹especially those disposed

trans to NO. Among other effects, the NO group displays

a strong trans influence, causing a concomitant weaken-

ing of the metal-ligand bond. Although the H ligand

too behaves as a trans influence moiety, the multiply

bonded NO group always prevails in the electronic

competition for σ-type d-orbital overlap. Thus, H^t-NO

ligands are less strongly bound and display an overall

high reactivity with a great potential for insertion

reactions.^2,3As further consequence of the aforemen-

tioned reduced L_nM-H overlap, one would also expect

Ch a r t 1

perturbation theory,⁴the energetic stabilization ∆E is

proportional to the square of the overlap S²between the

interacting fragment orbitals but inverse proportional

to the absolute difference of their unperturbed energies.

Diminishing S leads to a smaller value for ∆E, which

in turn increases the H contribution to the L_nM-H

bonding orbital and consequently leads to an enhanced

hydricity.

(1) Berke, H.; Burger, P. Comments Inorg. Chem. 1994, 16, 279.

(2) (a) Kundel, P.; Berke, H. J . Organomet. Chem. 1987, 335, 353.

(b) van der Zeijden, A. A. H.; Sontag, C.; Bosch, H. W.; Shklover, V.;

Berke, H.; Nanz, D.; von Philipsborn, W. Helv. Chim. Acta 1991, 74,

1194. (c) van der Zeijden, A. A. H.; Bosch, H. W.; Berke, H. Organo-

metallics 1992, 11, 2051. (d) van der Zeijden, A. A. H.; Berke, H. Helv.

Chim. Acta 1992, 75, 513. (e) Nietlispach, D.; Bosch, H. W.; Berke, H.

Chem. Ber. 1994, 127, 2403.

(3) (a) Ba¨th, F. Ph.D. Thesis, Universita¨t Zu¨rich, 1998. (b) Ho¨ck,

J .; Fox, T.; Schmalle, H.; Berke, H. Chimia 1999, 53, 350. (c) Liang,

F.; J acobsen, H.; Schmalle, H.; Artus, G.; Berke, H. Organometallics,

in press.

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tion in Chemistry; Wiley: New York, 1985; Chapter 3.

Publication on Web 08/03/2000

3606 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

Sch em e 1

To further explore the possibilities of tuning the metal

hydrogen bond, we replaced the activating NO group

with a carbyne CR. This ligand is also known to display

a strong trans influence.⁵It is classified as a three-

electron donor and, thus, acts as an isoelectronic stand-

in for NO. In comparison to the nitrosyl ligand, the

carbyne moiety displays altered π bonding properties

and might provide a different electronic environment

for H^t-CR. Therefore, it is of interest to compare the

reactivity patterns of W(tCR)(CO)_nL_4-nH complexes

with those of the related NO-substituted species

W(NO)(CO)_nL_4-nH.

The only previously reported trans carbyne hydride

complex with H^t-CRis a W(C^tBu)(dmpe)₂H species,⁶

which was obtained from the reaction of a (neopentyl)-

(neopentylidene)(neopentylidyne)(dmpe)tungsten com-

plex with dmpe (dmpe ) (Me)₂PCH₂CH₂P(Me)₂). How-

ever, the preparation of this compound as described in

the literature seems to be a very special case and is not

suitable as a general standard procedure. For this

reason we attempted the development of new routes to

carbyne hydride tungsten species W(tCR)(CO)_nL_4-nH.

Our CR residue of choice is the sterically quite crowded

mesitylcarbyne ligand, for which the nondesirable at-

tack on the carbyne moiety was estimated to be less

feasible.⁷For L we used a variety of phosphine ligands

with different σ-donor strengths, including P(Ph)₃,

P(OⁱPr)₃, P(OMe)₃, and PMe₃, as well as the chelating

ligands dppe (dppe ) Ph₂PCH₂CH₂PPh₂) and (Ph₂PCH₂-

CH₂)₂PPh.

data are the two intense ν˜(CO) bands at 1976 and 1889

cm^-1(KBr) in the IR spectrum and resonances at 266.9

and 221.9 ppm for the C_carbyneand the C_COatoms in the

¹³C{¹H} NMR spectrum. It was further identified by a

correct elemental analysis and its mass spectrum.

Chloro(mesitylcarbyne)tetracarbonyltungsten (1) served

as a starting material for further ligand substitutions

(Scheme 2). Its reaction with phosphorus donors pro-

duced in a first step disubstituted complexes. For

P(OMe)₃, PMe₃, and the bidentate dppe, a displacement

of both pyridine ligands resulted in formation of 2a ,b,e,

respectively. In these complexes, the two carbonyl

ligands are arranged in cis positions. In the case of

substitution of 1 with triphenylphosphine, a similar cis

complex could only be observed as an intermediate in

the substitution reaction. IR and ³¹P NMR spectroscopy

indicate that in a first step a monosubstituted product

is formed, which is followed by a disubstituted cis

complex. This compound constitutes a second interme-

diate at low steady-state concentration, which gradually

vanishes on being transformed into the thermodynami-

cally stable trans compound 2d . Also, the reaction of 1

with P(OⁱPr)₃resulted in the trans complex 2c, presum-

ably for steric reasons, which too are responsible for the

trans arrangement in 2d . The poor electron donor

P(OⁱPr)₃does not supply enough electron density at the

metal center to support an electronically unfavorable

trans arrangement of two strong π acceptors, so that in

this case one carbonyl and one pyridine ligand are

substituted for two phosphorus donors.

Resu lts a n d Discu ssion

Syn th esis of tr a n s-W(CMes)(CO)_n(Cl)L_4-nCom -

p lexes. Preparative access to W(CMes)(CO)_nClL_4-n

complexes was accomplished by a Fischer type carbyne

route⁸via a chloro(mesitylcarbyne)tetracarbonyltung-

sten intermediate, which was obtained by the reaction

of the appropriate acylate complex with oxalic acid

dichloride. According to the modification of Mayr,⁹an

initial and unstable tetracarbonyl species was trapped

by substitution of two CO groups with pyridine (py) to

yield the chlorodicarbonyl(mesitylcarbyne)bis(pyridine)-

tungsten system 1 (Scheme 1). Chloro(mesitylcarbyne)-

tetracarbonyltungsten could, however, be traced by IR

spectroscopy in methylene chloride solution.¹⁰Three ν˜-

(CO) bands are observed at 2123 (m), 2034 (s, br), and

1954 (m) cm^-1

.

Compound 1 was obtained as orange crystals in

almost quantitative yield. Characteristic spectroscopic

In the presence of an excess of the appropriate

monodentate ligand or the tridentate phosphorus donor

(Ph₂PCH₂CH₂)₂PPh, the trisubstituted species 3a ,b,d

were obtained, whereby successive substitution of both

pyridine ligands and one CO ligand occurred. Subse-

quent transformations of 3a with P(OMe)₃in neat

P(OMe)₃at 120 °C gave 4a in good yield. Although it

was not possible to obtain a satisfying elemental analy-

sis, the isolated material was sufficiently pure to be used

in further conversions.

The structures of the pseudo-octahedral species 2a -

e, 3a ,b,d , and 4a were assigned on the basis of IR and

NMR spectroscopy, as well as mass spectrometry. 2b-e

and 3a ,b,d were additionally confirmed by their ele-

mental analyses. The disubstituted cis complexes 2a ,b,e

(5) (a) Lee, F. W.; Chan, M. C. W.; Cheung, K. K.; Che, C. M. J .

Organomet. Chem. 1998, 563, 191. (b) Zhang, L.; Gamasa, M. P.;

Gimeno, J .; Carbajo, R. J .; Lopez Ortis, F.; Lanfranchi, M.; Tiripicchio,

A. Organometallics 1996, 15, 4274.

(6) (a) Clark, D. N.; Schrock, R. R. J . Am. Chem. Soc. 1978, 100,

6774. (b) Holmes, S. J .; Clark, D. N.; Turner, H. W.; Schrock, R. R. J .

Am. Chem. Soc. 1982, 104, 6322.

(7) (a) Fischer, H.; Hofmann, P.; Kreissl, F. R.; Schrock, R. R.;

Schubert, U.; Weiss, K. Carbyne Complexes, VCH: Weinheim, Ger-

many, 1988. (b) Mayr, A.; Hoffmeister, H. Adv. Organomet. Chem.

1991, 32, 227.

(8) Fischer, E. O.; Maasbo¨l, A. Chem. Ber. 1967, 100, 2445.

(9) (a) Mayr, A.; Asarao, M. F.; Kjelsberg, M. A.; Lee, K. S.; Van

Engen, D. Organometallics 1987, 6, 432. (b) McDermott, G. A.; Dorries,

A. M.; Mayr, A. Organometallics 1987, 6, 925. (c) Steil, P.; Mayr, A. Z.

Naturforsch., B 1992, 47, 656. (d) Yu, M. P. Y.; Mayr, A.; Cheung, K.-

K. J . Chem. Soc., Dalton Trans. 1998, 475. (e) Yu, M. P. Y.; Cheung,

K.-K.; Mayr, A. J . Chem. Soc., Dalton Trans. 1998, 2723.

(10) Fischer, E. O.; Kreis, G. Chem. Ber. 1976, 109, 1673.

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3607

Sch em e 2

show two ν˜(CO) bands in agreement with the bent

arrangement of the two CO groups. The positions of

these bands follow the expected order 2a (2021, 1960)

> 2e (1997, 1913) > 2b (1989, 1913 cm^-1), reflecting

the increasing donating abilities of the phosphorus

donors in this row. A less clear dependency of the ν˜-

(CO) bands is given in the trisubstituted series of 3a

(1946) > 3b (1891) > 3d (1882 cm^-1), where the

significant structural differences of the inner coordina-

tion sphere may play a role and account for the devia-

tion from the purely electronic order expected from the

donating properties of the phosphorus donor moieties.

Compound 2c, with two phosphorus donors and one

nitrogen donor, exhibits an even lower ν˜(CO) band at

1870 cm^-1. For these molecules and 4a , further spec-

troscopic characteristics with some structural implica-

tions are the ¹³C NMR signals of the C_carbyneatoms,

which appear between 260 and 280 ppm.

sodium borohydride in THF, the corresponding η²-BH₄

compounds 5a -d and 6a were formed. All complexes

could be isolated as red solids (5b,d ) or red oils (5a ,c,

6a ) in yields over 80% (Scheme 3).

Sch em e 3

Syn th esis of W(CMes)(η²-H₂BH₂)(CO)_nL_3-nCom -

p lexes. Approaching the preparation of carbyne hydride

complexes, we first aimed at the synthesis of respective

borohydride compounds, since their existence and po-

tential use as synthetic intermediates was inferred from

the supposedly analogous nitrosyl hydride chemistry.¹¹

When complexes 2c,d , 3a ,b, and 4a were reacted with

The structures of 5a -d and 6a were assigned on the

basis of their spectroscopic data. In the solution IR

spectra (benzene or hexane), two bands at around 2400

cm^-1(∆ν˜ between 28 and 42 cm^-1) were attributed to

ν˜(BH) for the terminal hydrogens. This splitting is

(11) (a) Gusev, D. G.; Llamazares, A.; Artus, G.; J acobsen, H.; Berke,

H. Organometallics 1999, 18, 75. (b) J acobsen, H.; Heinze, K.;

Llamazares, A.; Schmalle, H. W.; Artus, G.; Berke, H. J . Chem. Soc.,

Dalton Trans. 1999, 1717.

-

characteristic for a BH₄ligand bound in bidentate

fashion.¹²Stretching frequencies for the bridging hy-

3608 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

Sch em e 4

drogen atoms,¹²which might appear in the range of

1650-2150 cm^-1, could not be assigned. For the unique

CO groups of 5a -d , ν˜(CO) bands were identified at

relatively low wavenumbers, indicating strong charge

transfer from the apparently electron-rich metal center.

¹³C NMR resonances of the C_carbyneatoms are shifted

by about 20 ppm to lower field and are now detected

between 280 and 300 ppm. For 5a -d , both the bands

of C_carbyneas well as C_carbonylappear as triplets, which

indicates that both the CR and the CO group are in cis

positions with respect to the two phosphorus donors. In

contrast to related W(CO)₂(η²-H₂BH₂)L₂(NO) mol-

ecules,¹³the carbyne complexes are relatively stable and

can be stored at -20 °C, whereas the nitrosyl complexes

decompose with elimination of H₃B‚PR₃.¹⁴

but required higher temperatures around 0 °C and

longer reaction times. Under these conditions, the

decomposition of the final product already takes place,

so that the spectroscopic yield amounts only to 35%.

If the reaction of 5b with quinuclidine and PMe₃is

-

carried out at -20 °C, the monodentate BH₄adduct

W(CMes)(η¹-HBH₃)(CO)(PMe₃)₃(9b ) can be detected

in the NMR spectrum. A similar species, 9a , can also

be generated from the reaction of 5a with P(OMe)₃

(Scheme 5). In this case, however, it is necessary to

Sch em e 5

Syn t h esis of tr a n s-W(CMes)(CO)_nH L_4-nCom -

p lexes. Two steps are necessary in order to transform

the tetrahydroborate adducts into the desired carbyne

hydride complexes. A Lewis base is needed in order to

abstract borane, and an additional donor ligand is

required to obtain a coordinatively saturated 18-electron

species. The Lewis base of choice for the abstraction

reaction is quinuclidine. The resulting adducts are very

stable compounds, and in the presence of phosphorus

donors in the reaction mixture, no H₃B‚PR₃adducts

could be detected by NMR spectroscopy. Furthermore,

quinuclidine as a ligand does not compete with the

phosphorus donors for coordination to the metal center

but selectively binds liberated BH₃. The role of the

additional donor ligand is best taken by the correspond-

ing phosphine.

The tetrahydroborate adducts 5a ,b,d are reacted with

1 equiv of quinuclidine and 1 equiv of PR₃in THF at

-20 °C to afford the tungsten carbyne hydrides 7a ,b,d

(Scheme 4). For the preparation of trans-W(CMes)H-

(P(OMe)₃)₄(8a ), a slight excess of the amine and the

phosphorus donor is required.

Complex 7a was obtained after a reaction time of 2 h

in a spectroscopic yield of 80%. No more of the starting

material 5a could be detected in the NMR spectrum.

The reaction mixture might be kept for several days at

-20 °C, and it is also possible to isolate the hydride at

low temperatures and to store it at -20 °C. Warming

to room temperature, however, leads to decomposition

within 1 h. The formation of 7b did not occur at -20 °C

lower the temperature to -60 °C, since otherwise loss

of BH₃to form the tungsten hydride 7a occurs, as well

as back-reaction to regenerate the bidentate adduct

5a .

This observation might give a first indication of the

metal-hydride bond strength in complexes with P(OMe)₃

and PMe₃ligands. A stronger W-H bond facilitates the

B-H bond cleavage and, thus, the BH₃abstraction. The

higher thermal stability of 9b compared to that of 9a

leads to the conclusion that the W-H linkage is weaker

in the first case. Since the hydride ligand has also to

compete with the phosphorus ligands for σ donation to

the metal center, it should bind more strongly when the

donor ability of the PR₃ligand is poorer, as is the case

for 9a compared to 9b. We were also able to identify

the major byproducts in the formation of 7a and 7b. In

both cases, a complex of the type W(CO)(PR₃)₅could be

spectroscopically detected.

An alternative synthetic route to 7b is the reaction

of the PPh₃-substituted complex 5d with excess tri-

methylphosphine and quinuclidine at low temperature.

The poor donor ligand triphenylphosphine is easily

exchanged with the more basic PMe₃group, and instant

formation of 9b is observed. This procedure, however,

did not enhance the yield of the product.

(12) Marks, T. J .; Kolb, J . R. Chem. Rev. 1977, 77, 263.

(13) van der Zeijden, A. A. H.; Shklover, V.; Berke, H. Inorg. Chem.

1991, 30, 4393.

(14) van der Zeijden, A. A. H.; Berke, H. Helv. Chim. Acta 1992,

75, 513.

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3609

Sch em e 6

To increase the thermal stability of the carbyne

hydride complex, a tridentate chelating ligand was

introduced. 7d is accessible from 5d at -20 °C. How-

ever, warming to room temperature again causes de-

composition of the tungsten hydride. We finally syn-

thesized a carbyne hydride complex with four phosphorus

donors in the coordination sphere, 8a . Although this

compound too cannot be handled at room temperature

without decomposition, experiments indicate that 8a is

indeed more stable than 7a . We will return to this fact

at a later point of our discussion.

tion of H₂can also be traced in the proton NMR

spectrum. The formation of the phenolate complex 10

thus indicates substantial hydridic character of the

W-H functionality in 7a .

We further investigated the reduction potential of the

prototype 7a toward carbon dioxide and unsaturated

organic compounds, such as acetylenes, aldehydes, and

ketones. The reaction with CO₂proceeds smoothly, and

after a reaction time of 1 h, complex 11 is formed in

good yield. Two isomers can possibly result as insertion

products,namelya hydroxycarbonylcomplex,[M]-COOH,

or a formate complex, [M]-OCHO. In the literature,

formate complexes are reported almost exclusively,¹⁵

and 11 is yet another representative of this class of

compounds. This is concluded from the IR spectra,¹⁶as

The structures of the four tungsten hydride complexes

7a ,b,d and 8a were assigned by NMR spectroscopy. The

chemical shifts for the hydride ligands are in the range

from -4.6 to -6.2 ppm. For 7a ,d , the signals appear as

3

t-CO

t-P

a quartet, since the small difference in J _HPand J _HP

well as from the small value of the J _PCcoupling

could not be resolved in the experiments. For 7b, the

expected splitting into a doublet of a triplet is observed,

and for 8a , the four phosphorus donors split the hydride

signal into a quintet. ³¹P{¹H} NMR spectroscopy un-

equivocally establishes the coordination geometry of the

phosphorus donors.

Rea ctivity stu d ies of tr a n s-W(CMes)(CO)H(P -

(OMe)₃)₃. The reaction patterns of the new class of

carbyne hydride complexes have been investigated for

trans-W(CMes)(CO)H(P(OMe)₃)₃(7a ). Selected trans-

formations are collected in Scheme 6.

To establish experimentally the hydridic polarization

of the tungsten-hydrogen bond, 7a was reacted with a

weak acid. When a solution of W(CMes)(CO)H(P(OMe)₃

and excess phenol is kept for 4 days at -20 °C, the

complete consumption of 7a is observed, and compound

10 is detected with a spectroscopic yield of 60%. This

complex results from protonation of the transition-metal

complex and subsequent loss of dihydrogen. The evolu-

constant of the formate ligand. Two ν(CO) bands in the

infrared spectrum are assigned to the carbonyl group

(1946 cm^-1) and to the formate ligand (1633 cm^-1). In

the ¹³C{¹H} NMR spectrum, the resonance at 167.1 ppm

is assigned to the C formate nucleus. Coupling with the

P atoms splits this signal into a doublet of a triplet, with

3

values for J _PCof 6.2 and 1.5 Hz. The relatively large

difference in the coupling constants is indicative of a

strong distortion from an octahedral coordination ge-

ometry around the tungsten center. In contrast, ²J _PCof

the metal bonded carbon atom of a hydroxycarbonyl

ligand can be expected at much higher values.

When a solution of 7a in THF is reacted with the

symmetrically substituted acetylene MeOOCCtCCOOMe

(15) (a) Darensbourg, D. J .; Kudaroski, R. A. Adv. Organomet. Chem.

1983, 22, 129. (b) Sneeden, R. P. A. In Comprehensive Organometallic

Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Perga-

mon: Oxford, U.K., 1982; Vol. 8, Chapter 50.4.

(16) Hillhouse, G. L.; Haymore, B. L. Inorg. Chem. 1987, 26, 1876.

3610 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

for 24 h at -20 °C, the trans insertion product 12 is

obtained in a clean reaction. Its structure has been

determined by NMR and IR spectroscopy and is con-

firmed by mass spectrometry. In the ³¹P{¹H} spectrum,

the chemically equivalent P atoms are detected at 160.9

ppm. This signal shows tungsten satellites with a value

1

for J _PWof 433 Hz, characteristic for P(OMe)₃ligands

in trans positions.¹⁷The spectroscopic data of the

organic ligand are similar to those published for the

analogous product of the reaction between the isoelec-

tronic nitrosyl compound¹⁸trans-W(CO)₂H(NO)(PMe₃)₂

and MeOOCCtCCOOMe. 12 does not directly result

from the insertion of the acetylene into the W-H bond

but is formed via subsequent isomerization of the

primary insertion product 12a .

In the ³¹P{¹H} spectrum a characteristic system of

doublet and a triplet resonance are seen at 158.5 and

2

154.4 ppm, respectively. For the triplet resonance, a J _PP

coupling constant of 46.7 Hz is measured.

The reaction of 2-benzoylpyridine with 7a requires

reaction temperatures around 0 °C and a reaction time

of 48 h to afford the insertion product 14. Since at this

temperature decomposition of 7a occurs as a side

reaction, 14 is obtained in a yield of only 35%. This

complex decomposes at room temperature. However, the

compound could be identified by NMR spectroscopy, and

the characteristic resonances show the same features

as those measured for 13. In contrast to 13, no primary

insertion product could be observed during the forma-

tion of 14. A similar observation was made for the

reaction of trans-W(CO)₂H(NO)(PMe₃)₂with the acti-

vated ketone 2-benzoylpyridine.¹⁸

The insertion reactions, which have been presented

here, do indeed indicate an enhanced reactivity of the

tungsten-hydrogen bond. Reactions with CO₂, acet-

ylenes, and activated carbonyl functionalities already

take place at temperatures around -20 °C, whereas

related nitrosyl complexes react only at elevated tem-

peratures and generally require longer reaction times.¹⁸

On the other hand, the thermal instability of the

hydride complexes, which requires the low reaction

temperature, might prevent reactions with more inert

carbonyl functions and limits the scope of possible

applications. The lability of the coordination sphere of

7a might be one reason for the instability of this

complex. In the next section, we present a series of

experiments, which further support this hypothesis.

Hyd r id e Migr a tion a n d Ca r ben e F or m a tion for

W(CMes)(CO)H(P (OMe)₃)₃. When 7a is treated with

the phosphorus donors P(OMe)₃or PMe₃at -50 °C, no

exchange of carbon monoxide with phosphine ligands

could be observed. Instead, new compounds appeared,

which were identified as the carbene complexes W(CH-

Mes)(CO)(P(OMe)₃)₄(15a ) and W(CHMes)(CO)(PMe₃)₂-

(P(OMe)₃)₂(15b), respectively. Similarly, the reaction

between carbon monoxide and 7a did not result in an

insertion of CO into the metal-hydride bond but

produced the carbene complex 16 (Scheme 7).

If the reaction between 7a and the acetylene is carried

out at -60 °C, 12a can be detected by NMR spectros-

copy. When the reaction mixture is warmed to -20 °C,

complex 12 is formed within 1 day. A similar situation

was observed for the aforementioned nitrosyl hydride

compound. In this case, however, the isomerization

reaction is much slower, and both isomers could by

characterized by X-ray structure determination.¹⁸

It was argued that the driving force for the isomer-

ization reaction might be the fact that the π-donating

oxygen substituent favors a coordination trans to the

strongest π-accepting ligand.¹⁸If this argument holds

true, the CR moiety indeed has to be looked at as a

strong π-acceptor, which can even compete with CO.

The reduction of benzaldehyde with 7a could not be

achieved at the required reaction temperature of -20

°C, and even at 0 °C only decomposition could be

observed. The reaction with more activated aldehydes

was, however, successful. 7a reacts with pyridine-2-

carbaldehyde in THF at -20 °C within 24 h to form the

insertion product 13 in 80% yield. 13 decomposes at

room temperature; therefore, this complex was charac-

terized by NMR spectroscopy. The two chemically

equivalent P atoms appear in the ³¹P{¹H} spectrum as

a singlet at 148.8 ppm, with tungsten satellites, which

1

exhibit a J _WPcoupling constant of 437 MHz. This value

again is characteristic for two P(OMe)₃ligands in trans

positions.¹⁷The ortho H of the pyridine ring is detected

as a doublet at 9.14 ppm. In comparison to the signal

for the free ligand, this signal is shifted to lower field

by 0.34 ppm, which is a consequence of the coordination

of the pyridine nitrogen to the metal center. When the

insertion is followed by NMR spectroscopy, the primary

insertion product 13a can be detected in the initial state

of the reaction.

The reaction between 7a and 1-3 equiv of P(OMe)₃

at -20 to -80 °C led to an equilibrium between 15a

and 7a , which was investigated by NMR spectroscopy.

At low temperatures and large excess of the phosphorus

donor, product formation was favored. On the other

hand, at higher temperatures or smaller amounts of

excess P(OMe)₃, the equilibrium lies on the side of the

hydride complex 15a , which clearly manifests itself in

(17) Verkade, J . G.; Quin, L. D. Phosphorus-31 NMR Spectroscopy

in Stereochemical Analysis; VCH: Weinheim, Germany, 1987; Vol. 8.

(18) van der Zeijden, A. A. H.; Bosch, H. W.; Berke, H. Organome-

tallics 1992, 11, 563.

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3611

Sch em e 7

the resonances at -38.3 and -38.9 ppm appear as trip-

lets of a doublet. This indicates that in 15b two P(OMe)₃

and two PMe₃ligands are present. The two equivalent

phosphite groups are trans to each other, whereas the

two trimethylphosphine ligands are trans to the two

π-accepting moieties. In contrast to 15a , complex 15b

is not in equilibrium with the carbyne hydride 7a .

In a similar fashion, treatment of a solution of 7a in

THF with CO gas at -50 °C results in the new

compound 16. It can be stored in solution at -20 °C but

decomposes within minutes at room temperature. As

was the case for 15b, this complex is not in equilibrium

with 7a .

the NMR and IR spectra. Three characteristic signals

are observed in the ³¹P{¹H} spectrum. The resonance

at 165.3 ppm, which belongs to P^t-CO, exhibits an

Two ν˜(CO) stretching frequencies at 2001 and 1877

cm^-1are observed in the IR spectrum, pointing to two

carbonyl ligands in a cis arrangement. The ³¹P{¹H}

spectrum reveals that three P(OMe)₃ligands coordinate

1

unusually small J _PWcoupling constant of 235 Hz. The

expected value for a P^t-COligand in an octahedral

coordination environment lies in the range between 340

1

and 380 Hz.¹⁷The small J _PWvalue indicates a signifi-

1

in a meridional fashion. The small J _PWcoupling

cant deviation of the angle (P^t-CO-W-C^t-P) from the

constant of 230 Hz for the ligand trans to the carbonyl

group again indicates a significant distortion from an

idealized octahedral geometry. The carbene proton

ideal value of 180°. We have observed a similar effect

1

before and were able to correlate the small J _PWvalue

3

with geometric data obtained from an X-ray structure

appears as a quartet at 16.36 ppm with identical J _HP

1

analysis.¹⁹The carbene proton appears in the H NMR

coupling constants of 4.3 Hz for all three P nuclei.

Therefore, the carbene group is cis to all three phosphite

ligands, and consequently the two carbonyl groups must

be located trans to the carbene moiety and to one

P(OMe)₃ligand, respectively. When the reaction be-

tween 7a and carbon monoxide is carried out with ¹³CO,

after a short time a signal at 207.8 ppm appears in the

¹³C{¹H} NMR spectrum. This doublet of a triplet

spectrum as a multiplet at 16.92 ppm. The characteristic

value of 30.2 Hz for P^t-CHcan already be seen in this

2

3

complex signal. Precise values for the J _HPcoupling

constants have been determined by selective decoupling

from the phosphorus nuclei.

To further establish the equilibrium between 7a and

15a , a 1D-SEXSY spectrum with NOE difference pulse

sequence was recorded. Irradiating at the hydride

resonance of 7a indicated an exchange with the carbene

proton of 15a . Similarly, when irradiation was carried

out at the carbene proton resonance, an inverted signal

for the hydride ligand was detected. This experiment

establishes that both H resonances are in exchange

equilibrium and that on the NMR time scale a transition

between 7a and 15a takes place.

2

resonance shows small J _CPcoupling constants of 7.8

and 11.3 Hz, which allows one to conclude that the

incoming ¹³CO selectively coordinates trans to the

carbene ligand.

In the proton NMR spectrum of 16, an additional

weak signal is found in the region for a carbene ligand.

It appears as a doublet at 17.05 ppm with a coupling

3

constant J _HPof 34.6 Hz. This value is indicative of a P

In the ¹³C{¹H} spectrum two signals at 287.2 and

219.5 ppm are observed. In a DEPT-135 experiment a

positive signal at 287.2 ppm was obtained, whereas no

resonance was seen at 219.5 ppm. Thus, the latter

resonance stems from the carbonyl ligand, whereas the

former signal belongs to the carbene moiety of 15a .

The equilibrium reaction was also investigated by IR

spectroscopy at -30 °C. In the ν˜(CO) region, two bands

appear at 1937 and 1803 cm^-1, belonging to 7a and 15a ,

respectively. A subsequent increase in P(OMe)₃concen-

tration led to an increase in intensity for the band at

1803 cm^-1, whereas the absorption at 1937 cm^-1de-

creased. The opposite effect could be seen when the

temperature in the IR cell was raised to 0 °C. This

experiment establishes a migration of the hydride onto

the carbyne ligand. Alternative reduction of the carbonyl

group would result in a formyl ligand. This, however,

is expected to cause a ν˜(CHO) stretching frequency at

wavenumbers much lower than those observed.

ligand trans to the proton. The low intensity of this

resonance, however, prohibits a more detailed analysis

of this signal.

We should further mention the fact that neither for

7d nor for 8a , in the presence of excess P(OMe)₃, could

the formation of a carbene complex be spectroscopically

detected. Also, both hydrides do not show any reactivity

toward carbon monoxide, as was detected for compound

7a .

From all the observations described above, we might

draw the picture for hydride migration and carbene

formation shown in Scheme 8.

The reaction sequence is initialized by dissociation of

one P(OMe)₃ligand to form a five-coordinated interme-

diate. Several experimental facts support this assump-

tion. In any solution of 7a , free P(OMe)₃can always be

detected in the NMR spectra. This indicates the lability

of one of the phosphorus donors toward dissociation. The

fact that no carbene formation is observed when 7d is

treated with CO or excess P(OMe)₃at -10 °C provides

further support for our assumption. The tridentate dppe

ligand substantially stabilizes the P coordination sphere

in 7b, and ligand dissociation is not a facile process any

more. The five-coordinate carbyne intermediate pos-

sesses a free coordination site, but not a hydride ligand,

trans to the carbyne group. Coordination of excess phos-

_

The reaction between 7a and PMe₃at 40 °C leads to

the formation of the carbene complex 15b. Both the

carbonyl and the carbene ligand are identified by ³¹C-

{¹H} spectroscopy. In the ³¹P{¹H} spectrum, the signal

at 150.9 ppm is split into a doublet of a doublet, whereas

(19) Baur, J .; J acobsen, H.; Burger, P.; Artus, G.; Berke, H. Eur. J .

Inorg. Chem. 2000, 1411.

3612 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

Sch em e 8

step, hydride migration onto the carbyne moiety takes

place, leading to a five-coordinated carbene fragment.

Coordination of another ligand molecule then completes

the formation of the complexes 15a ,b and 16. Since 15a

is in equilibrium with 7a , all steps in the reaction

sequence leading to 15a must be at equilibrium as well.

In contrast, during the formation of 15b or 16, at least

one of the steps discussed in Scheme 8 must be ir-

reversible or represent a chemical equilibrium, which

lies almost exclusively on the product side.

Although the mechanism presented in Scheme 8 is

consistent with the experimental observations and

explains the stereochemistry observed for the reaction

products, the considerations regarding the geometry of

the five-coordinated intermediates are hypothetical and

are not supported by experimental facts. In connection

with this problem, for the formation of 16, we cannot

tell at which point in the reaction sequence carbon

monoxide is coordinating to the transition-metal frag-

ment, although we know that in the final product the

incoming CO is found trans to the CR group. The

carbene formation step via direct migration of H^-onto

the CR group requires a cis arrangement of these two

ligands. However, alternative migration routes, which

do not require an isomerization of the carbyne complex

and might involve formyl intermediates, cannot defi-

nitely be excluded. To obtain further information on the

carbene formation process, we have performed a com-

putational study on the model complexes W(CH)(CO)H-

(PH₃)₃(I) and W(CH)H(PH₃)₄(XV), which will be

discussed in the next section.

phorus donor or CO leads to an octahedral complex with

H

^-and CR in cis positions. If two different phosphorus

Th eor etica l In vestiga tion of th e Ca r ben e F or -

m a tion Rea ction . In Figure 1, the energetic profiles

of various possible pathways for the formation of the

donors are present, for example P(OMe)₃and PMe₃, we

can assume that the stronger σ-donor will preferentially

coordinate to the transition-metal fragment. In the next

F igu r e 1. Possible reaction pathways for the formation of the carbene complexes VI and XIII from W(CH)(CO)H(PH₃)₃

(I), as obtained from density functional calculations.

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3613

carbene species W(CH₂)(CO)(PH₃)₄(VI) and W(CH₂)-

(CO)₂(PH₃)₃(XIII) are displayed.

The carbene ligand pivots in place so that one small

and one large W-C-H angle with values of 88 and 164°

are seen. One of the C-H bond lengths is, at 1.16 Å,

substantially elongated. The same H atom comes close

to the metal center, and the short distance d(W-H) of

2.20 Å indicates some additional bonding interaction.

Thus, one might describe the carbene ligand in IV as

η²-CR₂. The distorted η²-coordination mode has first

been observed for alkylidene complexes of electron-

deficient transition metals.²⁰A molecular orbital analy-

sis²¹of these molecules traces the deformation to an

intramolecular electrophilic interaction of acceptor or-

bitals of the metal with the carbene lone pair. A

secondary interaction weakens the C-H bond and

attracts the H atom to the metal center. Similar orbital

interactions are at work in the present case. We will

return to η²-carbene coordination once more in the last

section of our discussion.

The migration step III f IV is energetically favorable

by 15 kJ /mol. The open form V, however, is virtually

isoenergetic with IV and possesses a free coordination

opposite to the carbene ligand. Uptake of another PH₃

then leads to the final product W(CH₂)(CO)(PH₃)₄(VI).

An alternative reaction route toward VI might involve

migration of the hydride onto the carbonyl group,

leading to the formation of the tungsten formyl VIII.

In this complex, the CHO group is bonded side-on in η²

fashion, with the H atom being cis to the carbyne group.

The formation of VIII requires an activation energy of

128 kJ /mol. In the transition state VII^q, an η¹-formyl

group is located in the plane of the three P donor

ligands. The five-coordinated formyl species is 42 kJ /

mol higher in energy than the reference system and

might rearrange to the more stable compound III.

Alternatively, coordination of a PH₃group leads to the

formyl compound IX, from which the final product VI

can be reached by H transfer from the formyl onto the

carbyne moiety. IX is 20 kJ /mol higher in energy than

I, and the very long d(W-P) separation of 2.72 Å

indicates that the P ligand trans to CH is only weakly

bonded. The high activation barrier for the formation

of the η²intermediate, as well as the unfavorable

relative energies of the CHO complexes VIII and IX,

suggests that formyl complexes do not occur in the

course of the carbene formation.

All reaction routes originate from the model complex

I, which, together with the free ligands that dissociate

or coordinate during the course of the reaction, is taken

as the reference system at zero energy. Although not

explicitly indicated, all energy differences are taken for

systems containing the same number of atoms, includ-

ing coordinated as well as free ligands.

The dissociative pathway is initiated by loss of the

phosphine ligand trans to the carbonyl group, leading

to the five-coordinated species W(CH)(CO)H(PH₃)₂(II).

In the most stable isomer, the remaining two PH₃

ligands are located trans to each other, while the cis

geometry IIa is calculated to be 9 kJ /mol higher in

energy. The trans arrangement of the P ligands will be

maintained during the whole course of the calculated

reaction. System II is 65 kJ /mol higher in energy than

the reference system I. To judge whether the dissocia-

tion step is facile or not, we have to keep in mind that

our calculated results correspond to differences in total

bonding energies. Approximating entropy changes from

translational and rotational contributions as 50 kJ /mol

at -25 °C, and taking the correction to the internal

energy as 4 kJ /mol, obtained from an approximate value

of 400 cm^-1for ν˜(WP), we can estimate a ∆G value of

about 11 kJ /mol for the ligand dissociation step. Thus,

the generation of the five-coordinated intermediate II

is not a critical step in the carbene formation. This

conclusion is in accord with the experimental observa-

tion that, in any solution of 7a , free phosphine ligand

is present. The loss of a carbonyl group results in the

complex IIb, which is 142 kJ /mol higher in energy, and

does not represent a feasible entry into the reaction

sequence.

Recoordination of the phosphine ligand might lead to

back-reaction to I or result in the formation of complex

III, in which now the carbyne and the hydride ligand

are cis. This compound is 8 kJ /mol more stable than I.

The P ligand trans to the CH group displays an

unusually long d(W-P) bond length of 2.65 Å, about 0.2

Å longer than for the other two phosphines. At the same

time, the distance d(W-CH) gets shorter in the isomer-

ization process I f III. This indicates an increase in

metal-carbyne bond strength, which might provide a

driving force for the iomerization reaction.

When both carbon monoxide and phosphorus donors

are present in the reaction mixture, the intermediate

II coordinates CO to form cis-W(CH)(CO)₂H(PH₃)₂(XI).

This complex is 23 kJ /mol more stable than III, which

suggests that in the formation of XIII, CO coordination

preferably occurs before PH₃coordination. The incoming

CO group is situated trans to the carbyne ligand. The

coordination of the CH group in X is not linear but

shows a W-C-H angle of 163°, anticipating the coor-

dination mode of a η²-carbene unit. The formation of a

complex XI containing such a ligand is energetically

favorable by 69 kJ /mol. The symmetric coordination

geometry XII is 8 kJ /mol higher in energy. When a P

donor attacks XI such that cleavage of the agostic inter-

Hydride migration onto the CH group leads to the

carbene species IV, which possesses an interesting

coordination geometry.

(20) (a) Churchill, M. R.; Youngs, W. J . J . Chem. Soc., Chem.

Commun. 1978, 1048. (b) Shultz, A. J .; Williams, J . M.; Schrock, R.

R.; Rupprecht, G. A.; Fellmann, J . D. J . Am. Chem. Soc. 1979, 101,

1593.

(21) Goddard, R. J .; Hoffmann, R.; J emmis, E. D.. J . Am. Chem.

Soc. 1980, 102, 7667.

3614 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

tively electron rich, and the carbyne ligand is the only

π-accepting group present in the molecule. Carbene

formation reduces the π-accepting power of the C-based

ligand and is therefore energetically not a favorable

process.

Our model calculations indicate that formation of

complex 15a is likely to proceed via a dissociative mech-

anism and does not involve formyl complexes. In the

formation of 16a , coordination of the CO group precedes

coordination of a phosphorus donor. This leads to a

complex with the incoming CO trans to the carbene and

the two carbonyl groups in a cis arrangement. The

hydride migration is facilitated by the presence of a CO

group in the coordination sphere of the complex. Com-

pound 8a does not isomerize into to a carbene complex,

since formation of the η²-CHR intermediate is energeti-

cally disfavored.

F igu r e 2. Calculated energy profile for ligand isomeriza-

tion and carbene formation for W(CH)H(PH₃)₄(XV).

Ca r ben e F or m a tion via P r oton a tion Rea ction s.

We conclude our discussion by briefly commenting on

an alternative transformation of carbyne complexes into

carbene compounds. Treatment of the carbyne chlorides

trans-W(CR)(Cl)L₄with HCl results in carbene com-

plexes of the type W(CHR)(Cl)₂L₃. These reactions were

first described by Schrock²²and Mayr.^9aX-ray structure

determinations^9a,23of the tungsten carbenes revealed

the presence of an η²-CHR group, as discussed in the

previous section. In a recent neutron diffraction study²⁴

of W(CHMe)Cl₂(CO)(PMe₃), the precise coordination

geometry of the carbene moiety could be determined.

The bond distances d(W-H) and d(C-H) amount to

1.922(6) and 1.185(7) Å, and the W-C-H angle is 74.7-

(3)°. The structural deformation for the d⁴complexes

can again be explained by enhanced orbital interaction

of the carbene lone pair with the metal center.²¹In

addition, the C-H σ orbital acts as a σ donor toward

the metal center. Because of this agostic interaction,

Mayr describes the bond between the alkylidene group

and metal center even as a triple bond.²⁴

action and formation of the new W-P bond occur in a

concerted fashion, the product XIII is formed in a way

that the new CO ligand ends up trans to the carbene

group, in accordance with the experimental observa-

tions.

Complex XIII is not the most stable W(CH₂)(CO)₂-

(PH₃)₃isomer. Compound XIV, having the CO as well

as the PH₃groups trans to each other, is more stable

by 18 kJ /mol. Although the trans arrangement of the

carbonyl ligands seems energetically unfavorable, this

coordination modes ensures that the strongest π accep-

tor in the system, namely the CH₂ligand, does not have

to share electron density from an occupied metal-based

d orbital with a CO group. A shortening in the d(W-

CH₂) bond distance by 0.02 Å in the process XIII f XIV

indicates an increase in the carbene bond strength.

Thus, XIII is the kinetic product of the carbene forma-

tion reaction, whereas XIV represents the thermody-

1

namic product. The additional signals in the H NMR

spectrum of 16 might belong to such a species, which

also possesses a phosphorus donor trans to the carbene

ligand. Alternative routes to complex XIV might involve

the regular carbene intermediate XII, or system V, if

PH₃coordination precedes CO coordination.

In an analogous fashion, the reaction of 3a with HCl

at room temperature furnishes the carbene complex 17,

which can be isolated as a red, crystalline material

(Scheme 9).

We now turn to complex W(CH)H(PH₃)₄(XV), a model

system for compound 8a . We recall that for 8a , the

formation of a carbene complex could not be observed.

The computed energy profile for carbene formation

via ligand dissociation for XV is displayed in Figure 2.

The calculations indicate that both the trans and the

cis isomers of W(CH)H(PH₃)₄should be of equal energy.

Here, we have to keep in mind that the real P(OMe)₃

ligands possess greater steric requirements than the

small model ligand PH₃. In the isomerization reaction

I f III the steric influence of the P donors is only of

secondary importance, since the main coordination

geometry of the P framework is maintained. Steric

effects will be of importance for the reaction XV f XVI,

since now a rearrangement of the phosphine ligands

takes place. It is reasonable to assume that XVI is

energetically disfavored on steric grounds.

Sch em e 9

Although 17 could not be characterized in the solid

state, NMR spectroscopy clearly reveals the η²-coordina-

tion of the CHMes group. The carbene proton appears

at -0.38 ppm as a triplet with a coupling constant J _HP

of 4.8 Hz. In addition, tungsten satellites are observed

3

1

with a J _HWcoupling of 28.7 Hz. This indicates that the

The changes in energy associated with hydride mi-

gration are crucial for the carbene formation process.

Establishing the η²-carbene complex XVIII requires an

energy of 26 kJ /mol; the symmetric CH₂compound

XVIIIa is even 35 kJ /mol higher in energy. The four

phosphorus donors in XVI render the metal center rela-

(22) Wengrovius, J . H.; Schrock, R. R.; Churchill, M. R.; Wasser-

mann, H. J . J . Am. Chem. Soc. 1982, 104, 1739.

(23) Churchill, M. R.; Wassermann, H. J . Inorg. Chem. 1983, 22,

1574.

(24) Bastos, C. M.; Lee, K. S.; Kjelsberg, M. A.; Mayr, A.; Vaan

Engen, D.; Koch, S. A.; Franolic, J . D.; Klooster, W. T.; Koetzle, T. F.

Inorg. Chim. Acta 1998, 279, 7.

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3615

shifts are referred to TMS and referenced through the residual

proton or ¹³C resonances of the deuterated solvent; ³¹P chemi-

cal shifts were externally referenced to 85% H₃PO₄); Bio-Rad

FTS-45 IR spectrometer; Finnigan/MAT 8320 mass spectrom-

eter; LECO CHNS-932 for elemental analyses.

interaction between the carbene proton and the metal

center is present not only in the crystal but also in

solution. Weakening of the C-H bond results in a very

small ¹J _HCcoupling constant of 75.2 Hz, which provides

further evidence for the agostic interaction.

tr a n s-W(CMes)Cl(CO)₂(p y)₂(1). [W(C(O)Mes)(CO)₅]-

[N(CH₃)₄] (6.83 g, 12.5 mmol) was dissolved in CH₂Cl₂(150

mL) and cooled to -100 °C. Oxalyl chloride, C₂O₂Cl₂(1.3 mL,

15 mmol), in CH₂Cl₂(20 mL) was precooled and added. The

reaction mixture immediately turned black and was stirred

for 30 min at -80 °C. A vivid gas evolution could be observed.

The yellow suspension was further stirred at 0 °C for another

30 min, during which time the gas evolution came to an end.

The suspension was cooled to -40 °C, and pyridine (8.0 mL,

100 mmol) was added. The mixture was warmed to room

temperature and stirred overnight. Filtration through Celite

and evaporation of the reaction mixture afforded the dark

orange crude product, which was washed with hexane (2 ×

20 mL). Recrystallization from CH₂Cl₂/hexane yielded 1 as an

orange powder (6.76 g, 12.0 mmol, 95%). IR (KBr, cm^-1): 1976

Con clu sion

In this work, we have introduced a new class of

activated transition-metal hydride complexes, namely

tungsten carbyne hydrides of the type trans-W(CMes)-

(CO)_nHL_4-n.We have developed a synthetic route which

provides access to a wide variety of hydride complexes.

In this context we also described the synthesis of the

chloride complexes trans-W(CMes)(CO)_n(Cl)L_4-nand

borate adducts W(CMes)(η²-H₂BH₂)(CO)_nL_3-n. Proto-

typical reactivity studies revealed both the great po-

tential and the drawbacks of these new compounds.

Complex 7a already reacts at low temperatures with

unsaturated organic compounds and displays an en-

hanced reactivity compared to the related nitrosyl

derivative trans-W(CO)₂H(NO)(PMe₃)₂. On the other

hand, low temperatures are required in order to prevent

decomposition of the hydride complex, thus limiting the

scope of its potential application as a hydrogenation

reagent. Only activated aldehydes such as pyridine-2-

carbaldehyde undergo a reaction with 7a before decom-

position sets in. One reason for the thermal instability

of the hydride complexes is the labile coordination

sphere of the phosphorus donors, which leads to hydride

migration and carbene formation as one of the decom-

position pathways for 7a . Our studies have shown that

strategies to increase the stability of the phosphorus

framework include the use of chelating ligands, as well

as the replacement of carbonyl ligands by additional

phosphorus donors. Stronger σ-donating P-ligands should

further stabilize the complexes and, at the same time,

lead to an even more reactive W-H functionality. This

could be concluded from the reactivity patterns of the

borate adducts 5a ,b. Following these considerations,

and utilizing the synthetic methodology that we have

developed in this work, we have already designed a

rational synthesis for the compound trans-W(CMes)-

(dmpe)₂H.²⁵This complex is indeed stable at room

temperature and could be characterized by an X-ray

structure analysis. Preliminary reactivity studies re-

vealed its high activity in hydrogen transfer reactions.^25a

Further studies on this promising complex as well as

on related nitrosyl derivatives are currently under way

in our laboratories.

1

(s), 1889 (s). H NMR (200 MHz, CDCl₃, ppm): 9.09 (“d”, 4H,

o-py), 7.78 (“t”, 2H, p-py), 7.29 (“t”, 4H, m-py), 6.75 (s, 2H, Mes),

2.43 (s, 6H, CH₃-Mes), 2.20 (s, 3H, CH₃-Mes). ¹³C{¹H} NMR

(50.3 MHz, CDCl₃, ppm): 266.9 (s, CMes), 221.9 (s, CO), 153.2

(s, o-py), 144.1 (s, ipso-Mes), 140.8 (s, o-Mes), 138.2 (s, p-py),

137.6 (s, p-Mes), 128.1 (s, m-Mes), 124.9 (s, m-py), 21.3 (s, CH₃-

Mes), 20.5 (s, 2CH₃-Mes). MS (FAB-Neg, LM ) CH₂Cl₂, M )

NBOH, m/z, %): 564 (M⁺, 20), 538 (M⁺- CO, 30), 508 (M⁺

-

2 CO, 50), 487 (M⁺- py, 50), 457 (M⁺- py - CO, 60), 429

(M⁺- py - 2 CO, 80). A satisfactory elemental analysis could

not be obtained.

tr a n s-W(CMes)Cl(CO)₂(P (OMe)₃)₂(2a ). According to the

procedure described for 1, a solution of W(CMes)Cl(CO)₄(2.45

mmol) in CH₂Cl₂was prepared. At -40 °C, P(OMe)₃(0.63 mL,

5.37 mmol) was added. The mixture was warmed to room

temperature, and CO evolution was observed. The solution was

stirred overnight, and the solvent removed in vacuo. The dark

yellow crude product was recrystallized from hexane. This

afforded 2a (1.40 g, 2.13 mmol, 87%), as a yellow oil at room

1

temperature. IR (hexane, cm^-1): 2021 (s), 1960 (s). H NMR

(300 MHz, C₆D₆, ppm): 6.57 (s, 2H, Mes), 3.51-3.47 (m, 18H,

P(OMe)₃), 2.67 (s, 6H, CH₃-Mes), 1.96 (s, 3H, CH₃-Mes). ¹³C-

2

{¹H} NMR (75.4 MHz, C₆D₆, ppm): 265.8 (t, J _CP) 15.0 Hz,

2

CMes), 209.8 (dd, J _CP) 87.0 × 30.5 Hz, CO), 144.7 (s, ipso-

Mes), 141.7 (t br, o-Mes), 138.1 (s, p-Mes), 128.3 (s, m-Mes),

52.1 (“t”, P(OMe)₃), 21.3 (s, CH₃-Mes), 20.8 (s, 2CH₃-Mes). ³¹P-

{¹H} NMR (121.5 MHz, C₆D₆, ppm): 142.4 (s, ¹J _PW) 390 Hz).

A satisfactory elemental analysis could not be obtained.

tr a n s-W(CMes)Cl(CO)₂(P Me₃)₂(2b). A mixture of 1 (1.3

g, 2.13 mmol) and PMe₃(0.51 mL, 4.70 mmol) in THF (150

mL) was stirred for 2 h at room temperature. The color

changed from orange to yellow. After filtration through Celite,

the dark yellow filtrate was evaporated in vacuo, and the crude

product was washed with a small amount of hexane. Recrys-

tallization from CH₂Cl₂/hexane yielded 2b (1.09 g, 1.96 mmol,

92%) as a yellow powder. Analytically pure 2b was obtained

by recrystallization from Et₂O at -30 °C. IR (KBr, cm^-1): 1989

Exp er im en ta l Section

All manipulations were performed under a nitrogen atmo-

sphere using standard Schlenk techniques. Solvents were dried

according to standard procedures and distilled under N₂prior

1

(s), 1913 (s). H NMR (300 MHz, d₈-THF, ppm): 6.70 (s, 2H,

Mes), 2.52 (s, 6H, CH₃-Mes), 2.12 (s, 3H, CH₃-Mes), 1.63 (m,

18H, PMe₃). ¹³C{¹H} NMR (75.4 MHz, d₈-THF, ppm): 267.5

to use. PMe₃and [W(C(O)Mes)(CO)₅][N(CH₃)₄]⁸were syn-

26

2

thesized following slightly modified²⁷literature procedures,

whereas all other reagents were purchased and used without

further purification. The following instruments were used for

spectroscopic and physical characterization: Varian Gemini

200 and Gemini 300 NMR spectrometers (¹H and ¹³C chemical

(t, J _CP) 9.7 Hz, CMes), 215.7 (dd, J _CP) 37.4 × 18.7 Hz,

CO), 145.7 (s, ipso-Mes), 140.3 (s, o-Mes), 137.6 (s, p-Mes),

128.8 (s, m-Mes), 21.6 (s, 2CH₃-Mes), 21.4 (s, CH₃-Mes), 19.2

(m, PMe₃). ³¹P{¹H} NMR (121.5 MHz, d₈-THF, ppm): -28.5

(s, ¹J _PW) 238 Hz). MS (FAB-Neg, LM ) CH₂Cl₂, M ) NBOH,

m/z, %): 558 (M⁺, 2), 530 (M⁺- CO, 28), 524 (M⁺- Cl, 20),

502 (M⁺- 2 CO, 100). Anal. Calcd for C₁₈H₂₉ClO₂P₂W

(558.68): C, 38.70; H, 5.23. Found: C, 38.77; H, 5.24.

(25) (a) Furno, F.; Bannwart, E.; Berke, H. Chimia 1999, 53, 350.

(b) Furno, F.; Fox, T.; Schmalle, H. W.; Berke, H. Organometallics

2000, 19, 3620.

(26) Wolfsberger, W.; Schmidbaur, H. Synth. React. Inorg. Met.-Org.

Chem. 1974, 4, 149.

tr a n s-W(CMes)Cl(CO)(p y)(P (OⁱP r )₃)₂(2c). A solution of

1 (0.82 g, 1.45 mmol) and P(OiPr)₃(3.3 mL, 14.5 mmol) in THF

(80 mL) was refluxed for 16 h. The yellow-green solution was

(27) Bannwart, E. Ph.D. Thesis, Universita¨t Zu¨rich, 1998.

3616 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

cooled and filtered through Celite, and the clear red filtrate

was evaporated in vacuo. Recrystallization from hexane

yielded 2c (1.14 g, 1.30 mmol, 90%) as a red powder. IR (KBr,

cm^-1): 1870 (s). ¹H NMR (300 MHz, C₆D₆, ppm): 9.52 (“d”,

2H, o-py), 6.87 (“t”, 1H, p-py), 6.74 (s, 2H, Mes), 6.58 (“t”, 2H,

m-py), 5.11 (m, 6H, PCH(CH₃)₂), 2.79 (s, 6H, CH₃-Mes), 2.06

(s, 3H, CH₃-Mes), 1.19 (m, 36H, PCH(CH₃)₂). ¹³C{¹H} NMR

mL) was refluxed for 16 h. The yellow-green solution was

cooled and filtered through Celite, and the clear, red filtrate

was evaporated in vacuo. After washing with hexane, and

recrystallization from Et₂O at -80 °C, 3a (3.80 g, 5.1 mmol,

95%) was obtained as a yellow powder. IR (KBr, cm^-1): 1946

1

(s). H NMR (200 MHz, C₆D₆, ppm): 6.67 (s, 2H, Mes), 3.64-

3.57 (m, 27H, P(OMe)₃), 2.81 (s, 6H, CH₃-Mes), 2.01 (s, 3H,

2

1

(75.4 MHz, CD₂Cl₂, ppm): 262.6 (t, J _CP) 17.0 Hz, J _CW

)

CH₃-Mes). ¹³C{¹H} NMR (50.3 MHz, CD₂Cl₂, ppm): 262.0 (q,

2

1

2

197.4 Hz, CMes), 240.1 (t, J _CP) 8.1 Hz, J _CW) 168.8 Hz,

CO), 155.7 (s, o-py), 145.7 (s, ipso-Mes), 141.0 (s, o-Mes), 137.0

(s, p-py), 135.4 (s, p-Mes), 127.8 (s, m-Mes), 123.3 (s, m-py),

68.8 (s, PCH(CH₃)₂), 24.3 (s, PCH(CH₃)₂), 21.5 (s, CH₃-Mes),

21.3 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm):

²J _CP) 15.7 Hz, CMes), 221.2 (dt, J _CP) 63.7 × 10.4 Hz, CO),

145.8 (s, ipso-Mes), 140.7 (s br, o-Mes), 136.3 (s, p-Mes), 128.2

(s, m-Mes), 52.7, 52.5, 52.2 (s, P(OMe)₃), 21.3 (s, CH₃-Mes),

20.8 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm):

148.7 (d, 2P, ²J _PP) 39.5 Hz, ¹J _PW) 425 Hz), 143.5 (t, 1P, ²J _PP

) 39.5 Hz, ¹J _PW) 366 Hz). MS (FAB-Neg, LM ) CH₂Cl₂, M )

1

145.1 (s, J _PW) 438 Hz). MS (FAB-Neg, LM ) CH₂Cl₂, M )

NBOH, m/z, %): 795 (M⁺- py, 10), 768 (M⁺- CO - py, 22),

731 (M⁺-CO - Cl - py, 3), 667 (M⁺- P(OiPr)₃, 25). Anal.

Calcd for C₃₄H₅₈NClO₇P₂W (874.09): C, 46.72; H, 6.69; N, 1.60.

Found: C, 46.22; H, 6.51; N, 1.47.

NBOH, m/z, %): 750 (M⁺, 1), 715 (M⁺- Cl, 17), 625 (M⁺

-

P(OMe)₃, 10), 598 (M⁺- CO - P(OMe)₃, 25), 566 (M⁺- 2 CO

- P(OMe)₃, 5). Anal. Calcd for C₂₀H₃₈ClO₁₀P₃W (750.74): C,

32.00; H, 5.10. Found: C, 31.95; H, 4.54.

tr a n s-W(CMes)Cl(CO)₂(P P h ₃)₂(2d ). According to the

procedure described for 1, a solution of W(CMes)Cl(CO)₄(6.66

mmol) in CH₂Cl₂(250 mL) was prepared. At 0 °C, a solution

of PPh₃(3.67 g, 13.99 mmol) in CH₂Cl₂(30 mL) was added. It

was stirred for 1 h at 40 °C and for 3 days at room tempera-

ture. The resulting brown solution was filtered through Celite,

and the filtrate was evaporated in vacuo. The brown solid was

washed several times with hexane (total 100 mL) and recrys-

tallized from CH₂Cl₂/hexane. A first fraction afforded traces

of the cis product (IR (cm^-1): 1981 (s), 1889 (s)) as yellow-

orange crystals. Adding more hexane afforded 2d (5.06 g, 5.43

mmol, 81%) as a yellow powder. Analytically pure material is

obtained after recrystallization from Et₂O. After drying for

several days in vacuo, 0.7 equiv of Et₂O could still be detected

tr a n s-W(CMes)Cl(CO)(P Me₃)₃(3b). 2b (120 mg, 0.21

mmol) was stirred in PMe₃(2.5 mL) for 5 days at room

temperature. After 3 days, the initial suspension has turned

into a clear, orange solution. Evaporation in vacuo and

recrystallization from Et₂O afforded 3b (115 mg, 0.19 mmol,

88%) as an orange powder. IR (KBr, cm^-1): 1891 (s). ¹H NMR

(300 MHz, C₆D₆, ppm): 6.67 (s, 2H, Mes), 2.58 (s, 6H, CH₃-

Mes), 2.03 (s, 3H, CH₃-Mes), 1.44 (m, 18H, PMe₃), 1.28 (m,

9H, PMe₃). ¹³C{¹H} NMR (50.3 MHz, d₈-THF, ppm): 261.9 (q,

2

²J _CP) 10.2 Hz, CMes), 233.1 (dt, J _CP) 43.4 × 7.0 Hz, CO),

147.5 (s, br, ipso-Mes), 137.9 (s br, o-Mes), 134.0 (“q” br, p-Mes),

127.2 (“q” br, m-Mes), 23.9 (s, CH₃-Mes), 22.5 (m, PMe₃), 21.4

(s, 2CH₃-Mes), 20.1 (m, PMe₃). ³¹P{¹H} NMR (121.5 MHz, C₆D₆,

2

1

ppm): -25.4 (d, 2P, J _PP) 19.8 Hz, J _PW) 272 Hz), -30.8 (t,

1P, ²J _PP) 19.8 Hz, ¹J _PW) 213 Hz). MS (FAB-Neg, LM ) CH₂-

Cl₂, M ) NBOH, m/z, %): 607 (M⁺, 1), 530 (M⁺- PMe₃, 48),

502 (M⁺- CO - PMe, 100). Anal. Calcd for C₂₀H₃₈ClOP₃W

(606.74): C, 39.59; H, 6.31. Found: C, 39.71; H, 6.14.

1

in the NMR spectrum. IR (KBr, cm^-1): 2024 (w), 1945 (s). H

NMR (300 MHz, C₆D₆, ppm): 7.91-7.88 (m, 12H, Ph), 6.97-

6.89 (m, 18H, Ph), 6.32 (s, 2H, Mes), 2.00 (s, 3H, CH₃-Mes),

1.87 (s, 6H, 2CH₃-Mes). ¹³C{¹H} NMR (75.4 MHz, CD₂Cl₂,

2

ppm): 277.3 (t, J _CP) 9.8 Hz, CMes), 213.4 (t, J _CP) 6.6 Hz,

tr a n s-W(CMes)Cl(CO)({P h ₂P CH₂CH₂}₂P P h ) (3d ). A so-

lution of 3a (1.50 g, 2.00 mmol) and (Ph₂PCH₂CH₂)₂PPh (1.12

g, 2.1 mmol) in toluene (50 mL) was refluxed for 6 h. The

orange-green solution was cooled and filtered through Celite,

and the clear, orange filtrate was evaporated in vacuo. After

washing with hexane, and recrystallization from toluene/

hexane, 3d (1.59 g, 1.74 mmol, 87%) was obtained as an orange

3

4

CO), 144.2 (t, J _CP) 1.6 Hz, ipso-Mes), 139.4 (t, J _CP) 6.6

Hz, o-Mes), 136.4 (s, p-Mes), 136.3 (“t”, ipso-Ph), 134.2 (“t”,

m-Ph), 129.9 (s, p-Ph), 128.2 (“t”, o-Ph), 127.9 (s, m-Mes), 21.4

(s, CH₃-Mes), 20.9 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz,

1

C₆D₆, ppm): 22.5 (s, J _PW) 275 Hz). MS (FAB-Neg, LM )

CH₂Cl₂, M ) NBOH, m/z, %): 875 (M⁺- 2 CO, 20), 870 (M⁺

- C₅H₅, 100), 868 (M⁺- CO - Cl, 40), 840 (M⁺- 2 CO - Cl,

4), 641 (M⁺- CO - PPh₃, 15), 612 (M⁺- 2 CO - PPh₃, 95).

Anal. Calcd for C₄₈H₄₁ClO₂P₂W‚0.7(CH₃CH₂)₂O (931.11): C,

61.86; H, 4.89. Found: C, 61.81; H, 5.05.

1

powder. IR (KBr, cm^-1): 1882 (s). H NMR (300 MHz, C₆D₆,

ppm): 7.95-7.72 (m, 10H, Ph), 7.18-6.82 (m, 15H, Ph), 6.57

(s, 2H, Mes), 3.55-3.20 (m, 4H, PCH₂), 2.25-1.85 (m, 4H,

PCH₂), 2.10 (s, 3H, CH₃-Mes), 2.02 (s, 6H, CH₃-Mes). ¹³C{¹H}

NMR (53.7 MHz, CD₂Cl₂, ppm): 268.9 (m, CMes), 235.0 (m,

CO), 147.2 (s, ipso-Mes), 145.6 (s, o-Mes), 135.4 (s, p-Mes),

125.6 (s, m-Mes), 134.1-127.9 (Ph), 33.6 (m, (Ph₂PCH₂CH₂)₂-

PPh), 26.0 (m, (Ph₂PCH₂CH₂)₂PPh), 21.5 (s, CH₃-Mes), 20.8

(s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm): 81.8

tr a n s-W(CMes)Cl(CO)₂(d p p e) (2e). dppe (1.48 g, 3.70

mmol, 1.05 equiv) was added to a solution of 1 (2.0 g, 3.54

mmol) in CH₂Cl₂(100 mL), and the reaction mixture was

stirred for 3 h at room temperature. A change in color from

orange to yellow was observed. Evaporation in vacuo, washing

with hexane (2 × 10 mL), and recrystallization from CH₂Cl₂/

hexane afforded 2e (2.64 g, 3.27 mmol, 92%) as a yellow

powder. IR (KBr, cm^-1): 1997 (s), 1913 (s). ¹H NMR (200 MHz,

CDCl₃, ppm): 7.82-7.76 (m, 4H, Ph), 7.74-7.70 (m, 4H, Ph),

7.42-7.26 (m, 8H, Ph), 7.24-7.18 (m, 4H, Ph), 6.51 (s, 2H,

Mes), 3.15-2.85 (m, 2H, PCH₂), 2.70-2.40 (m, 2H, PCH₂), 2.11

(s, 6H, CH₃-Mes), 1.79 (s, 3H, CH₃-Mes). ¹³C{¹H} NMR (50.3

MHz, CDCl₃, ppm): 271.4 (t, ²J _CP) 9.2 Hz, CMes), 215.0 (dd,

²J _CP) 43.3 × 7.0 Hz, CO), 145.8 (s, ipso-Mes), 140.7 (s, o-Mes),

137.5 (s, p-Mes), 127.8 (s, m-Mes), 143.5, 140.5, 135.1, 134.4,

133.2, 133.0, 132.2, 130.4, 129.7, 128.6, 128.4, 128.2 (C₆H₅),

2

1

2

(t, 1P, J _PP) 8.5 Hz, J _PW) 202 Hz), 47.0 (d, 2P, J _PP) 8.5

1

Hz, J _PW) 294 Hz). MS (FAB-Neg, LM ) THF, M ) NBOH,

m/z, %): 913 (M⁺, 1), 884 (M⁺- CO, 30). Anal. Calcd for

C₄₅H₄₄ClOP₃W (913.07): C, 59.19; H, 4.86. Found: C, 58.73;

H, 5.26.

tr a n s-W(CMes)Cl(P (OMe)₃)₄(4a ). 3a (200 mg, 0.27 mmol)

was dissolved in P(OMe)₃(10 mL), and the resulting mixture

was transferred into a steel autoclave and then heated to 120

°C for 3 days. The solvent was then removed in vacuo and the

residue washed with hexane to afford complex 4a (178 mg,

0.21 mmol, 77%) as a brown powder. This compound seems to

be unstable and decomposes after 1 h at room temperature

(visible by ³¹P NMR). A satisfactory elemental analysis of 4a

1

2

26.0 (dd, J _CP) 26.4 Hz, J _CP) 12.3 Hz, PCH₂), 21.3 (s, CH₃-

Mes), 20.0 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, CDCl₃,

1

ppm): 40.3 (s, J _PW) 229 Hz). MS (FAB-Neg, LM ) CH₂Cl₂,

could not be obtained. H NMR (300 MHz, C₆D₆, ppm): 6.70

M ) NBOH, m/z, %): 805 (M⁺, 2), 771 (M⁺- Cl, 20), 748 (M⁺

- 2 CO, 100). Anal. Calcd for C₃₈H₃₅O₂P₂ClW (804.94): C,

56.70; H, 4.38. Found: C, 56.13; H, 4.40.

(s, 2H, Mes), 3.75-3.52 (m, 36H, (P(OMe)₃)₃), 2.65 (s, 6H,

2CH₃-Mes), 1.98 (s, 3H, CH₃-Mes). ¹³C{¹H} NMR (50.3 MHz,

C₆D₆, ppm): 266 (m, CMes), 148.71 (s, ipso-Mes), 140.80 (s,

2

tr a n s-W(CMes)Cl(CO)(P (OMe)₃)₃(3a ). A solution of 1

(3.0 g, 5.3 mmol) and P(OMe)₃(6.2 mL, 53 mmol) in THF (180

o-Mes), 135.56 (s, p-Mes), 128.25 (s, m-Mes), 51.01 (d, J _CP

)

6.11 Hz, (P(OMe)₃)₄), 21.30 (s, 2CH₃-Mes), 20.70 (s, CH₃-Mes).

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3617

1

³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm): 148.60 (s, J _PW) 430

which was dried in vacuo, leaving 6a (79 mg, 0.11 mmol, 79%)

Hz).

as an oil. IR (hexane, cm^-1): 2447 (m, BH_t), 2413 (s, BH_t), 1839

1

W(CMes)(CO)(η²-H₂BH₂)(P (OMe)₃)₂(5a ). NaBH₄(71.8

mg, 0.90 mmol) was added to a solution of 3a (0.46 g, 0.61

mmol) in THF (20 mL). It was stirred for 2 h at room

temperature. A change in color from yellow to red was

observed. Evaporation in vacuo yielded a dark red solid, which

was suspended in hexane (30 mL) and filtered through Celite.

The clear, red solution was concentrated in vacuo until a few

millieters of solvent was left. Keeping the solution at -80 °C

overnight afforded a red, crystalline product. The solution was

decanted at low temperature. The crystals, which melt at room

temperature, were dried in vacuo, leaving 5a (0.31 g, 0.51

mmol, 83%) as a red oil. IR (hexane, cm^-1): 2458 (w, BH_t),

2417 (m, BH_t), 1925 (s). ¹H NMR (300 MHz, d₈-toluene, ppm):

6.49 (s, 2H, Mes), 3.39 (m, 18H, P(OMe)₃), 2.53 (s, 6H, CH₃-

Mes), 1.89 (s, 3H, CH₃-Mes). ¹H{¹¹B} NMR (300 MHz, d₈-

toluene, ppm): -2.0 (s, br, 1H, WHB), -4.1 (s, br, 1H, WHB).

(s, BH_b). H NMR (300 MHz, C₆D₆, ppm): 6.72 (s, 2H, Mes),

3.63-3.44 (m, 27H, P(OMe)₃), 2.72 (s, 6H, CH₃-Mes), 1.99 (s,

3H, CH₃-Mes), -3.5 (br, WHB). ¹³C{¹H} NMR (75.4 MHz, d₈-

2

THF, ppm): 284.5 (q, J _CP) 16.8 Hz, CMes), 148.4 (s, ipso-

Mes), 138.9 (s, o-Mes), 135.7 (s, p-Mes), 128.6 (s, m-Mes), 52.3

(d, P(OMe)₃), 52.1 (s, P(OMe)₃), 21.6 (s, 2CH₃-Mes), 21.4 (s,

2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm): 184.7 (t,

1

2

1

²J _PP) 19.7 Hz, J _PW) 615 Hz), 167.0 (d, J _PP) 19.7 Hz, J _PW

) 434 Hz). Anal. Calcd for C₁₉H₄₂BP₃O₉W (702.12): C, 32.50;

H, 6.03. Found: C, 33.28; H, 5.48.

tr a n s-W(CMes)(CO)H(P (OMe)₃)₃(7a ). A solution of 5a

(250 mg, 0.41 mmol), P(OMe)₃(49 µL, 0.42 mmol), and

quinuclidine (46 mg, 0.41 mmol) in THF (20 mL) was stirred

for 2 h at -20 °C. The solution turned from red to orange.

Warming to room temperature led to decomposition of the

product. 7a was spectroscopically characterized in the reaction

mixture. In NMR experiments, an NMR tube was charged with

5a , P(OMe)₃(1 equiv), quinuclidine (1 equiv), and d₈-THF (0.5

mL). The tube was stored at -20 °C, and after 2 h, 7a could

be detected in a yield of 80%, as determined by ³¹P{¹H} NMR

spectroscopy. IR (THF, -30 °C, cm^-1): 1935 (s). ¹H NMR (300

MHz, d₈-THF, -20 °C, ppm): 6.41 (s, 2P, Mes), 3.34-3.27 (m,

27H, P(OMe)₃), 2.25 (s, 6H, CH₃-Mes), 1.86 (s, 3H, CH₃-Mes),

2

¹³C{¹H} NMR (75.4 MHz, C₆D₆, ppm): 294.5 (t, J _CP) 15.0

Hz, CMes), 235.4 (t, ²J _CP) 8.0 Hz, CO), 146.4 (s br, ipso-Mes),

138.7 (s br, o-Mes), 137.4 (s, p-Mes), 128.5 (s, m-Mes), 52.0 (s,

P(OMe)₃), 21.4 (s, CH₃-Mes), 21.0 (s, 2CH₃-Mes). ³¹P{¹H} NMR

1

(121.5 MHz, d₈-toluene, ppm): 165.2 (s, J _PW) 430 Hz). A

satisfactory elemental analysis could not be obtained.

W(CMes)(η²-H₂BH₂)(CO)(P Me₃)₂(5b). According to the

procedure described for 5a , NaBH₄(96 mg, 2.60 mmol) was

reacted with 3b (470 mg (0.84 mmol), yielding after workup

5b (356 mg (0.70 mmol, 83%) as a red, hygroscopic powder. A

satisfactory elemental analysis of 5b could not be obtained.

IR (C₆H₆, cm^-1): 2420 (w, BH_t), 2392 (m, BH_t), 1878 (s). ¹H

NMR (300 MHz, d₈-THF, ppm): 6.67 (s, 2H, Mes), 2.31 (s, 6H,

CH₃-Mes), 2.11 (s, 3H, CH₃-Mes), 1.56 (m, 18H, PMe₃). ¹³C-

2

1

-4.66 (q, 1H, J _HP) 33.6 Hz, J _HW) 24.1 Hz). ¹³C{¹H} NMR

2

(75.4 MHz, d₈-THF, -20 °C, ppm): 273.5 (q, J _CP) 12.1 Hz,

2

CMes), 224.8 (dt, J _CP) 37.7 × 10.8 Hz, CO), 148.0 (s, ipso-

Mes), 139.6 (s br, o-Mes), 135.4 (s, p-Mes), 128.7 (s, m-Mes),

52.1, 51.8, 51.7, 51.4 (P(OMe)₃), 21.6 (s, CH₃-Mes), 21.5 (s,

2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, d₈-THF, -20 °C,

2

1

ppm): 168.0 (d, 2P, J _PP) 39.4 Hz, J _PW) 423 Hz), 160.2 (t,

1P, J _PP) 39.4 Hz, J _PW) 377 Hz).

2

1

{¹H} NMR (75.4 MHz, d₈-THF, ppm): 294.1 (t, J _CP) 10.6

Hz, CMes), 248.3 (t, J _CP) 4.3 Hz, CO), 147.2 (s, ipso-Mes),

2

tr a n s-W(CMes)(CO)H(P Me₃)₃(7b). An NMR tube was

charged with 5b (40 mg, 0.08 mol), PMe₃(8 µL, 0.08 mol),

quinuclidine (9 mg, 0.08 mol), and d₈-THF. The solution

immediately turned orange. After 48 h at 0 °C, 7b was

obtained in 40% yield, determined by ³¹P{¹H} NMR spectros-

copy. 7b is not stable at room temperature and was spectro-

scopically characterized in the reaction mixture. ¹H NMR (300

MHz, d₈-THF, 0 °C, ppm): 6.59 (s, 2H, Mes), 2.42 (s, 6H, CH₃-

Mes), 2.08 (s, 3H, CH₃-Mes), 1.62-1.50 (m, 27H, PMe₃), -2.65

(dt, ²J _HP) 32.2 × 24.4 Hz, ¹J _HW) 25 Hz, WH). ³¹P NMR (121.5

136.3 (s, o-Mes), 135.6 (s, p-Mes), 128.7 (s, m-Mes), 21.5 (s,

2CH₃-Mes), 21.4 (s, CH₃-Mes), 20.3 (“t”, J _CP) 14.2 Hz, PMe₃).

³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm): -4.0 (s, ¹J _PW) 275 Hz).

W(CMes)(η²-H₂BH₂)(CO)(P (OⁱP r )₃)₂(5c). From the reac-

tion of 2c (822 mg, 0.94 mmol) with NaBH₄(105 mg, 2.83

mmol), according to the procedure described for 5a , 5c (619

mg, 0.80 mmol) could be isolated as a red oil. A satisfactory

elemental analysis of 5c could not be obtained. IR (hexane,

cm^-1): 2450 (w, BH_t), 2408 (m, BH_t), 1913 (s). H NMR (300

MHz, C₆D₆, ppm): 6.61 (s, 2H, Mes), 4.92 (m, 6H, POCH(CH₃)₂),

2.71 (s, 6H, CH₃-Mes), 1.95 (s, 3H, CH₃-Mes), 1.22 (m, 36H,

POCH(CH₃)₂). ¹³C{¹H} NMR (75.4 MHz, C₆D₆, ppm): 295.4

(t, J _CP) 14.1 Hz, CMes), 238.2 (t, J _CP) 8.0 Hz, CO), 146.5

(s, ipso-Mes), 138.4 (s, o-Mes), 136.7 (s, p-Mes), 128.5 (s,

m-Mes), 69.4 (s, POCH(CH₃)₂), 23.9 (s, POCH(CH₃)₂), 21.5 (s,

CH₃-Mes), 21.3 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, C₆D₆,

1

2

1

MHz, d₈-THF, 0 °C, ppm): -28.7 (d, 2P, J _PP) 23.6 Hz, J _PW

2

1

) 264 Hz), -32.3 (t, 1P, J _PP) 23.6 Hz, J _PW) 224 Hz).

tr a n s-W(CMes)(CO)H ({P h ₂P CH ₂CH ₂}₂P P h ) (7d ). An

NMR tube was charged with 5d (41 mg, 0.046 mmol), (Ph₂-

PCH₂CH₂)₂PPh (24.8 mg, 0.046 mmol), quinuclidine (5.16 mg,

0.046 mmol), and d₈-THF (0.5 mL) and kept at -20 °C for 2

h. The solution turned orange, and 7d could be detected in

70% yield, determined by ³¹P{¹H} NMR spectroscopy. Warming

to room temperature led to decomposition of 7d , which was

spectroscopically characterized in the reaction mixture. ¹H

NMR (300 MHz, d₈-THF, -20 °C, ppm): 6.58 (s, 2H, Mes),

2.20-1.08 (m, br, CH₂P), 2.03 (s, 3H, CH₃-Mes), 1.84 (s, 6H,

2

1

ppm): 159.8 (s, J _PW) 426 Hz).

W(CMes)(η²-H₂BH₂)(CO)(P P h ₃)₂(5d ). As described for 5a ,

2c (478 mg, 0.51 mmol) was reacted with NaBH₄(58.5 mg,

1.58 mmol) for 4 h. 5d (384 mg, 0.43 mmol, 85%) is obtained

as a red solid. IR (C₆H, cm^-1): 2442 (w, BH_t), 2401 (m, BH_t),

1893 (s). H NMR (300 MHz, C₆D₆, ppm): 7.84 (m, 12H, Ph),

7.65-7.58 (m, 6H, Ph), 7.05-6.90 (m, 27H, Ph), 6.47 (s, 2H,

Mes), 2.11 (s, 6H, CH₃-Mes), 1.94 (s, 3H, CH₃-Mes). ¹³C{¹H}

NMR (75.4 MHz, C₆D₆, ppm): 299.1 (t, ²J _CP) 10.5 Hz, CMes),

2

CH₃-Mes), -6.2 (q, J _HP) 37.5 Hz, WH). ¹³C{¹H} NMR (53.7

MHz, d₈-THF, -50 °C, ppm): 206.3 (m, CO), 147.2 (s, ipso-

Mes), 145.6 (s, o-Mes), 135.4 (s, p-Mes), 125.6 (s, m-Mes),

134.6-129.0 (Ph), 33.6 (m, PPh(CH₂)₂), 26.0 (m, PPh₂CH₂),

22.0 (s, CH₃-Mes), 21.4 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5

2

243.2 (t, J _CP) 4.6 Hz, CO), 147.0 (s, ipso-Mes), 138.1 (s,

2

1

MHz, d₈-THF, -20 °C, ppm): 88.6 (t, 1P, J _PP) 7.3 Hz, J _PW

o-Mes), 137.2 (s, p-Mes), 128.6 (s, m-Mes), 137.7, 135.2, 135.1,

135.0, 134.1, 134.0, 132.0, 130.2, 129.6, 129.4, 128.8, 128.7 (s,

Ph), 21.5 (s, CH₃-Mes), 20.9 (s, 2CH₃-Mes). ³¹P{¹H} NMR

2

1

) 200 Hz), 56.7 (d, 2P, J _PP) 7.3 Hz, J _PW) 292 Hz).

tr a n s-W(CMes)H)(P (OMe)₃)₄(8a ). In an NMR tube, 6a

(34 mg, 0.048 mmol) was dissolved in d₈-THF (0.8 mL). At -20

°C, quinuclidine (6.5 mg, 0.058 mmol) and P(OMe)₃(10 µL,

0.059 mmol) were added. After the reaction mixture was kept

at -20 °C overnight, 8a could be detected in over 95% yield,

determined by ³¹P{¹H} NMR spectroscopy. At room tempera-

ture, 8a decomposes within a few hours. It was therefore

characterized by NMR spectroscopy of the reaction mixture.

¹H NMR (300 MHz, d₈-THF, ppm, -20 °C): 6.53 (s, 2H, Mes),

1

(121.5 MHz, C₆D₆, ppm): 45.2 (s, J _PW) 282 Hz). MS (FAB-

Neg, LM ) CH₂Cl₂, M ) NBOH, m/z, %): 886 (M⁺, 30), 865

(M⁺- CO, 38). A satisfactory elemental analysis could not be

obtained.

W(CMes)(η²-H₂BH₂)(P (OMe)₃)₃(6a ). 4a (120 mg, 0.14

mmol) was reacted with NaBH₄(16 mg, 0.42 mmol) in THF

(5 mL) at room temperature for 4 h. Workup of the reaction

mixture as described for 5a resulted in a red-brown solid,

3618 Organometallics, Vol. 19, No. 18, 2000

Bannwart et al.

3.70-3.42 (m, 36H, P(OMe)₃), 2.49 (s, 6H, CH₃-Mes), 2.02 (s,

3H, CH₃-Mes), -5.58 (quint., ²J _HP) 35.7 Hz, ¹J _HW) 20.4 Hz,

WH). ¹³C{¹H} NMR (75.4 MHz, d₈-THF, -20 °C, ppm): 265.0

W(CMe s){η²-(Z)-C(CO₂Me )dCH [C(O)OMe ]}(CO)(P -

(OMe)₃)₂(12). 12 is prepared according to the procedure

described for 11. 7a is generated in situ from 5a (250 mg, 0.41

mmol), P(OMe)₃(48.6 µL, 0.40 mmol), and quinuclidine (46

mg, 0.41 mmol) in THF (30 mL) and reacted with MeOOCCt

CCOOMe (51 µL, 0.42 mmol). 12 (265 mg, 0.36 mmol, 88%)

was isolated as a red oil. IR (CH₂Cl₂, cm^-1): 1905 (s), 1699

(m), 1590 (m). ¹H NMR (300 MHz, C₆D₆, ppm): 6.91 (t, 2H,

⁴J _HP) 3.5 Hz, H-vinyl), 6.69 (s, 2H, Mes), 3.51 (“t”, 18H,

P(OMe)₃), 3.60 (s, 3H, OCH₃), 3.24 (s, 3H, OCH₃), 2.84 (s, 6H,

CH₃-Mes), 2.02 (s, 3H, CH₃-Mes). ¹³C{¹H} NMR (53.7 MHz,

2

3

(quint., J _CP) 13.1 Hz, CMes), 151.2 (quint., J _CP) 1.8 Hz,

ipso-Mes), 140.1 (quint., ⁴J _CP) 2.0 Hz, o-Mes), 133.7 (s, p-Mes),

2

128.5 (s, m-Mes), 48.9 (d, J _CP) 9.9 Hz, P(OMe)₃), 21.6 (s,

2CH₃-Mes), 21.5 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, d₈-

1

THF, ppm, -20 °C): 168.3 (s, J _PW) 432 Hz).

tr a n s-W(CMes)(η¹-HBH₃)(CO)(P (OMe)₃)₃(9a ). An NMR

tube is charged with 5a (55 mg, 0.09 mmol) and d₈-THF (0.5

mL). At -60 °C, P(OMe)₃(12 µL, 0.09 mmol) is added. The

color immediately changes from red to orange. The yield was

determined as 90% by ³¹P{¹H} NMR spectroscopy. ¹H NMR

(300 MHz, d₈-THF, -60 °C, ppm): 6.66 (s, 2H, Mes), 3.65-

3.58 (m, 27H, P(OMe)₃), 2.51 (s, 6H, CH₃-Mes), 2.10 (s, 3H,

CH₃-Mes), -1.95 (br, WHB). ³¹P NMR (121.5 MHz, d₈-THF,

2

d₈-THF, ppm): 280.9 (t, J _CP) 15.6 Hz, CMes), 237.1 (t, J _CP

2

) 9.3 Hz, CO), 235.4 (t, J _CP) 12.4 Hz, R-C(vinyl)), 183.6 (s,

COOMe), 179.5 (s, COOMe), 147.6 (s, ipso-Mes), 140.0 (s br,

3

o-Mes), 136.0 (s, p-Mes), 128.4 (s, m-Mes), 119.5 (t, J _CP) 3.9

Hz, â-C(vinyl)), 54.2, 51.9 (s, P(OMe)₃), 21.5 (s, CH₃-Mes), 21.1

(s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz, C₆D₆, ppm): 160.7

2

1

-60 °C, ppm): 154.5 (d, 2P, J _PP) 40.9 Hz, J _PW) 425 Hz),

1

2

1

(s, J _PW) 433 Hz). MS (FAB-Neg, LM ) THF, M ) NBOH,

150.4 (t, 1P, J _PP) 40.9 Hz, J _PW) 362 Hz).

m/z, %): 706 (M⁺- CO, 7), 610 (M⁺- P(OMe)₃, 7), 582 (M⁺

-

W(CMes)(η¹-HBH ₃)(CO)(P Me₃)₃(9b). 5d (54 mg, 0.061

mmol) and PMe₃(25 µL, 0.243 mmol) are reacted in d₈-THF

(0.5 mL) at -60 °C in an NMR tube. During the spectroscopic

investigation, the temperature is kept below -20 °C. The

spectroscopic yield amounts to 95%. ¹H NMR (300 MHz, d₈-

THF, -30 °C, ppm): 6.65 (s, 2H, Mes), 2.45 (s, 6H, CH₃-Mes),

2.09 (s, 3H, CH₃-Mes), 1.67-1.63 (m, 27H, PMe₃), -2.1 (br,

WHB). ¹³C{¹H} NMR (75.4 MHz, d₈-THF, -20 °C, ppm): 274.8

P(OMe)₃- CO, 6). A satisfactory elemental analysis could not

be obtained.

W(CMes)(CO)(η²-NC₅H₄{2-CH₂O})(P (OMe)₃)₂(13). An

NMR tube was charged with 5a (21 mg, 34.6 mmol) and d₈-

THF (0.5 mL). At -50 °C, P(OMe)₃(4 µL, 33.9 mmol) and

quinuclidine (3.8 mg, 34.2 mmol) were added, and the tube

was kept for 2 h at -20 °C to form 7a . Then, pyridine-2-

carbaldehyde (4.7 µL, 49.2 mmol) was added. After 22 h the

consumption of 7a is complete. 13 is obtained in a yield of 80%,

as determined by ³¹P{¹H} NMR spectroscopy. Warming to

2

(q, J _CP) 10.2 Hz, CMes), 233.7 (dt, J _CP) 32.9 × 7.4 Hz,

CO), 147.2 (s, ipso-Mes), 139.4 (s, o-Mes), 135.0 (s, p-Mes),

128.7 (s, m-Mes), 22.6 (s, 2CH₃-Mes), 22.1 (m, PMe₃), 21.4 (s,

CH₃-Mes). ³¹P NMR (121.5 MHz, d₈-THF, -30 °C, ppm): -24.9

1

room temperature leads to decomposition within 15 min. H

2

1

2

NMR (300 MHz, d₈-THF, -20 °C, ppm): 9.12 (“d”, 1H, J )

5.6 Hz, H-C(6′)), 7.67 (“t”, 1H, J ) 7.5 Hz, H-C(4′)), 7.21 (“d”,

1H, J ) 7.9 Hz, H-C(3′)), 7.11 (“t”, 1H, J ) 6.4 Hz, H-C(5′)),

(d, 2P, J _PP) 20.1 Hz, J _PW) 271 Hz), -30.1 (t, 1P, J _PP

)

1

20.1 Hz, J _PW) 213 Hz).

W(CMes)(CO)(OP h )(P (OMe)₃)₃(10). A solution of 7a (0.05

mmol) in d₈-THF (0.5 mL) was mixed with phenol (5 mg, 0.05

mmol) at -40 °C in an NMR tube. Within 24 h at 0 °C the

formation of 10 and the evolution of H₂was observed in the

NMR spectra. The yield of product formation was 60%,

determined by ³¹P{¹H} NMR-spectroscopy. 10 was too unstable

to be isolated from the reaction mixture. IR (CH₂Cl₂, cm^-1):

1958 (s). ¹H NMR (300 MHz, d₈-THF, 0 °C, ppm): 6.66 (“t”,

2H, m-Ph), 6.38 (s, 2H, Mes), 6.27 (“d”, 2P, o-Ph), 6.05 (“t”,

1P, p-Ph), 3.55-3.42 (m, 27H, P(OMe)₃), 2.54 (s, 6H, CH₃-Mes),

2.20 (s, 3H, CH₃-Mes). ³¹P NMR (121.5 MHz, d₈-THF, 0 °C,

4

6.63 (s, 2H, Mes), 5.11 (t, 2H, J _HP) 4.3 Hz, CH₂O), 3.52-

3.41 (m, 18H, P(OMe)₃), 2.59 (s, 6H, CH₃-Mes), 2.13 (s, 3H,

CH₃-Mes). ³¹P NMR (121.5 MHz, d₈-THF, -20 °C, ppm): 148.8

1

(s, J _PW) 437 Hz).

W(CMes)(CO)(η²-NC₅H₄{2-CH(P h )O})(P (OMe)₃)₂(14).

As described for 13, 7a is reacted with 1.0 equiv of benzoylpy-

ridine. After 48 h all of 7a has reacted. 14 is detected in a

yield of 25%, by ³¹P{¹H} NMR spectroscopy. ¹H NMR (300

MHz, d₈-THF, -20 °C, ppm): 9.20 (“d”, 1H, H-C(6′)), 8.05-

7.95 (m, 2H, Ph), 7.62 (“t”, 1H, H-C(4′)), 7.60-7.40 (m, 3H,

Ph), 7.17 (“d”, 1H, H-C(3′)), 7.13 (“t”, 1H, H-C(5′)), 6.77 (s,

2H, Mes), 5.67 (t, 1H, ⁴J _HP) 5.7 Hz, CHO), 3.63-3.45 (m, 18H,

2

1

ppm): 150.3 (d, 2P, J _PP) 39.4 Hz, J _PW) 429 Hz), 142.0 (t,

2

1

1P, J _PP) 39.4 Hz, J _PW) 375 Hz).

P(OMe)₃), 2.62 (s, 6H, CH₃-Mes), 2.28 (s, 3H, CH₃-Mes). ³¹P

W(CMes)(CO)(η¹-OC(O)H)(P (OMe)₃)₃(11). To a solution

of 5a (200 mg, 0.33 mmol) in THF (30 mL) were added P(OMe)₃

(38.9 µL, 0.32 mmol) and quinuclidine (37 mg, 0.32 mmol) at

-40 °C, After 2 h at -25 °C, the reaction vessel is flooded with

CO₂under vigorous stirring. Within a few minutes a color

change from dark orange to orange was observed. After 30 min,

the solution was slowly warmed to room temperature. After

another 30 min, the solvent was evaporated in vacuo. The

crude product was washed with hexane, suspended in Et₂O,

and filtered through Celite. The filtrate was concentrated and

kept at -80 °C. At this temperature, 11 (181 mg, 0.24 mmol,

72%) precipitated as an orange oil. IR (CH₂Cl₂, cm^-1): 1942

2

NMR (121.5 MHz, d₈-THF, -20 °C, ppm): 149.7 (d, J _PP

)

1

183.3 Hz, J _PW) 437 Hz).

W(CHMes)(CO)(P (OMe)₃)₄(15a ). A solution of 7a in d₈-

THF (0.5 mL) is treated with a varying excess of P(OMe)₃(1.0-

3.0 equiv). At -30 °C and below, complex 15a was detected to

be in equilibrium with 7a by IR and NMR spectroscopy. IR

1

(THF, -30 °C, cm^-1): 1803 (s). H NMR (300 MHz, d₈-THF,

-50 °C, ppm): 16.92 (m br, CHMes), 6.71 (s, 2P, Mes), 3.81-

3.48 (m, 36H, P(OMe)₃), 2.62 (s, 3H, CH₃-Mes), 2.55 (s, 6H,

CH₃-Mes). ¹H{³¹P_selective} NMR (300 MHz, d₈-THF, -50 °C,

ppm): 16.92 (ddt, ³J _HP) 30.2 × 10.9 × 14.8 Hz, CHMes). ¹³C-

{¹H} NMR (75.4 MHz, d₈-THF, -45 °C, ppm): 287.7 (s br,

1

4

(s), 1623 (s). H NMR (300 MHz, d₈-THF, ppm): 7.97 (q, J _HP

) 1.1 Hz, 1H, OC(O)H), 6.62 (s, 2H, Mes), 3.74-3.61 (m, 27H,

P(OMe)₃), 2.57 (s, 6H, CH₃-Mes), 2.12 (s, 3H, CH₃-Mes). ¹³C-

2

CHMes), 219.1 (ddt, J _CP) 58.8 × 7.5 × 11.1 Hz, CO), 149.2

(s, ipso-Mes), 139.5 (s br, o-Mes), 129.4 (s, m-Mes). ³¹P{¹H}

2

{¹H} NMR (75.4 MHz, d₈-THF, ppm): 271.0 (q, J _CP) 14.8

2

NMR (121.5 MHz, d₈-THF, -50 °C, ppm): 165.3 (dt, 1P, J _PP

1

2

) 51.7 × 22.4 Hz, J _PW) 235 Hz), 154.2 (dd, 2P, J _PP) 51.7

Hz, CMes), 221.1 (dt, J _CP) 64.3 × 10.9 Hz, CO), 167.1 (dt,

1

2

³J _CP) 6.2 × 1.5 Hz, OC(O)H), 147.2 (s, ipso-Mes), 140.9 (s br,

o-Mes), 136.1 (s, p-Mes), 128.5 (s, m-Mes), 54.2, 52.2, 52.0 (s,

P(OMe)₃), 21.4 (s, CH₃-Mes), 21.1 (s, 2CH₃-Mes). ³¹P{¹H} NMR

(121.5 MHz, d₈-THF, ppm): 154.6 (d, 2P, ²J _PP) 40.3 Hz, ¹J _PW

× 36.4 Hz, J _PW) 420 Hz), 130.0 (dt, 1P, J _PP) 36.4 × 22.4

1

Hz, J _PW) 328 Hz).

W(CHMes)(CO)(P Me₃)₂(P (OMe)₃)₂(15b). A solution of 7a

(0.13 mmol) in d₈-THF (0.5 mL) is treated with PMe₃(39 µL,

0.39 mmol) at -50 °C. The solution turned dark orange, and

15 was obtained in 80% yield, determined by ³¹P{¹H} NMR

spectroscopy. At 0 °C, decomposition took place within a few

minutes. ¹H NMR (300 MHz, d₈-THF, -20 °C, ppm): 16.32

(m, 1H, CHMes), 6.59 (s, 2P, Mes), 3.69-3.42 (m, 18H,

2

1

) 430 Hz), 147.5 (t, 1P, J _PP) 40.3 Hz, J _PW) 380 Hz). MS

(FAB-Neg, LM ) THF, M ) NBOH, m/z, %): 732 (M⁺- CO,

5), 715 (M⁺- COOH, 70), 608 (M⁺- P(OMe)₃- CO, 12), 591

(M⁺- P(OMe)₃- COOH, 14). A satisfactory elemental

analysis could not be obtained.

Carbyne Hydride Complexes of Tungsten

Organometallics, Vol. 19, No. 18, 2000 3619

P(OMe)₃), 2.21 (s, 3H, CH₃-Mes), 2.08 (s, 6H, CH₃-Mes), 0.95

(m, 18H, PMe₃). ¹³C{¹H} NMR (75.4 MHz, d₈-THF, -20 °C,

ppm): 274.9 (m, CHMes), 223.3 (m, CO), 143.5 (s, ipso-Mes),

134.7 (s br, o-Mes), 131.9 (s, p-Mes), 131.3 (s, m-Mes), 51.4

(P(OMe)₃), 25.7 (m, PMe₃), 22.0 (s, 2CH₃-Mes), 21.5 (s, CH₃-

Mes). ³¹P{¹H} NMR (121.5 MHz, d₈-THF, -20 °C, ppm): 150.9

evaluated with an accuracy of at least four significant digits.

The self-consistent DF calculations were based on the local

exchange-correlation potential of Vosko, Wilk, and Nussair,³⁰

with self-consistent gradient corrections due to Becke³¹and

Perdew³²(BP86). Relativistic effects were included using a

quasi-relativistic approach.³³

2

1

(dd, 2P(OMe)₃, J _PP) 41.8 × 29.0 Hz, J _PW) 425 Hz), -38.3

Geom etr y Op tim iza tion . Default procedures³⁴were ap-

plied in geometry optimizations and transition state (TS)

searches. Final gradients were better than 0.003 hartree/Å or

hartree/radian, respectively. The start geometries for the TS

optimizations were obtained in a linear transit run along the

respective internal mode. The TS were identified by one

negative eigenvalue of the approximate Hessian.

Ch em ica l Mod el. Modeling POMe₃by PH₃will influence

the energetics of those reaction sequences, which involve

dissociation or association of a phosphorus ligand, in the sense

that the phosphite forms stronger M-L bonds.³⁵Reactions in

which the framework of the P ligands does not significantly

change are less affected by this simplification. On the other

hand, solvent effects can be expected to lower the free enthalpy

for M-L bond dissociation. Thus, the model reactions studied

in this work should provide an approximate but reasonable

description of the hydride migration as well as carbene

formation processes as observed in the experiment.

2

1

(td, 1PMe₃, J _PP) 29.0 × 5.9 Hz, J _PW) 189 Hz), -38.9 (td,

2

1

1PMe₃, J _PP) 41.8 × 5.9 Hz, J _PW) 123 Hz).

W(CHMes)(CO)₂(P (OMe)₃)₃(16). An NMR tube, contain-

ing a solution of 7a in d₈-THF, was flooded with CO gas at

-50 °C. A color change from orange to yellowish black was

observed, and 16 was obtained in a spectroscopic yield of 75%.

Warming to 0 °C led to decomposition within a few minutes.

IR (THF, -30 °C, cm^-1): 2001 (m), 1877 (s). ¹H NMR (300

3

MHz, d₈-THF, -30 °C, ppm): 16.36 (q, 1H, J _HP) 4.3 Hz,

CHMes), 6.67 (s, 2H, Mes), 3.66-3.39 (m, 27H, P(OMe)₃), 2.31

(s, 6H, CH₃-Mes), 2.10 (s, 3H, CH₃-Mes). ¹³C NMR (75.4 MHz,

d₈-THF, -30 °C, ppm): 283 (s, br, CHMes), 208 (s, br, CO).

³¹P NMR (121.5 MHz, d₈-THF, -30 °C, ppm): 158.5 (t, 1P,

1

2

²J _PP) 48.0 Hz, J _PW) 232 Hz), 154.7 (d, 2P, J _PP) 48.0 Hz,

¹J _PW) 414 Hz).

W(CHMes)Cl₂(CO)(P (OMe)₃)₂(17). A solution of 3a (262

mg, 0.35 mmol) in THF (50 mL) was cooled to -25 °C, and a

1.0 M solution of HCl in Et₂O (0.4 mL, 0.40 mmol) was added.

After 5 min, the reaction mixture was warmed to room

temperature, and the dark orange solution was stirred for 1

h. The solvent was evaporated in vacuo, and the resulting

brown oil was recrystallized from hexane. 17 (160 mg, 0.25

mmol, 70%) was isolated as a temperature-sensitive, red

Ackn owledgm en t. Financial support from the Swiss

National Science Foundation (SNSF) is gratefully ac-

knowledged.

Su p p or tin g In for m a tion Ava ila ble: Figures giving se-

lected ¹H NMR spectra for 15a , 16, and 17 and tables giving

Cartesian coordinates and final bonding energies for the

optimized geometries I-XVIII.

1

crystalline material. IR (KBr, cm^-1): 1960 (s). H NMR (300

MHz, C₆D₆, ppm): 6.51 (s, 2H, Mes), 3.61 (m, 18H, P(OMe)₃),

2.67 (s, 6H, CH₃-Mes), 1.96 (s, 3H, CH₃-Mes), -0.38 (t, 1H,

1

³J _HP) 4.8 Hz, J _HW) 28.7 Hz, J _HC) 75.2 Hz, CHMes). ¹³C-

OM000129H

{¹H} NMR (53.7 MHz, C₆D₆, ppm): 228.0 (t, J _CP) 8.6 Hz,

2

CHMes), 217.9 (t, ²J _CP) 16.0 Hz, CO), 52.9 (s, P(OMe)₃), 21.1

(29) (a) Baerends, E. J .; Be´rces, A.; Bo, C.; Boerrigter, P. M.; Cavallo,

L.; Deng, L.; Dickson, R. M.; Ellis, D. E.; Fan, L.; Fischer, T. H.; Fonseca

Guerra, C.; van Gisbergen, S. J . A.; Groeneveld, J . A.; Gritsenko, O.

V.; Harris, F. E.; van den Hoek, P.; J acobsen, H.; van Kessel, G.;

Kootstra, F.; van Lenthe, E.; Osinga, V. P.; Philipsen, P. H. T.; Post,

D.; Pye, C. C.; Ravenek, W.; Ros, P.; Schipper, P. R. T.; Schreckenbach,

G.; Snijders, J . G.; Sola, M.; Swerhone, D.; te Velde, G.; Vernooijs, P.;

Versluis, L.; Visser, O.; van Wezenbeek, E.; Wiesenekker, G.; Wolff,

S. K.; Woo, T. K.; Ziegler, T. ADF Release 1999.02, SCM, Amsterdam,

1999. (b) Baerends, E. J .; Ellis, D. E.; Ros, P. E. Chem. Phys. 1973, 2,

41. (c) te Velde, G.; Baerends, E. J . J . Comput. Phys. 1992, 99, 84. (d)

Fonseca Guerra, C.; Snijders, J . G.; te Velde, G.; Baerends, E. J . Theor.

Chem. Acta 1998, 99, 391.

(s, 1CH₃-Mes), 20.8 (s, 2CH₃-Mes). ³¹P{¹H} NMR (121.5 MHz,

1

C₆D₆, ppm): 127.7 (s, J _PW) 415 Hz). MS (FAB-Neg, LM )

CH₂Cl₂, M ) NBOH, m/z, %): 664 (M⁺, 1), 626 (M⁺- Cl, 15),

600 (M⁺- CO - Cl, 28), 567 (M⁺- CO - 2 Cl, 10).

Com p u ta tion a l P r oced u r es. Gen er a l Con sid er a tion s.

The density functional²⁸(DF) calculations utilized the ADF²⁹

program package, release 1999.01/02 and 2.0.1. For the ns,

np, nd, and (n + 1)s shells on W, a triple-ú-STO basis

augmented by one (n + 1)p function was employed (ADF

database IV). The valence shell of main-group elements was

described by a double-ú-STO basis and one STO polarization

function (ADF database III). The numerical integration grid

(30) Vosko, S. J .; Wilk, M.; Nussair, M. Can. J . Phys. 1980, 58, 1200.

(31) Becke, A. Phys. Rev. 1988, A38, 3098.

(32) Perdew, J . P. Phys. Rev. 1986, B33, 8822.

(33) Ziegler, T.; Tschinke, V.; Baerends, E. J .; Snijders, J . G.;

Ravenek, W. J . Phys. Chem. 1989, 93, 3050.

was chosen in

a way that significant test integrals are

(34) te Velde, G. ADF User’s Guide, Vrije Universiteit Amsterdam:

Amsterdam, 1999.

(35) Bannwart, E.; J acobsen, H.; Hu¨bener, R.; Schmalle, H. W.;

Berke, H. Submitted for publication.

(28) (a) Kohn, W.; Becke, A. D.; Parr, R. G. J . Phys. Chem. 1996,

100, 12974. (b) Baerends, E. J .; Gritsenko, O. V. J . Phys. Chem. A 1997,

101, 5383.

Article Doi

Reactivity patterns of carbyne hydride complexes of tungsten

DOI: 10.1021/om000129h

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Article abstract of DOI:10.1021/om000129h

Full text of DOI:10.1021/om000129h

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