Coordinated carbenes from electron-rich olefins on RuHCl(PPr3/(i))2

View Article Online / Journal Homepage / Table of Contents for this issue

Coordinated carbenes from electron-rich oleÐns on RuHCl(PPri ) ¤

3 2

Joseph N. Coalter III,a John C. Bollinger,a John C. Hu†man,a Ulrike Werner–Zwanziger,a

Kenneth G. Caulton,*a Ernest R. Davidson,*a Helene Gerard,b Eric Clotb and Odile Eisenstein*b

a Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington,

IN 47405-4001, USA. E-mail: caulton=indiana.edu; davidson=indiana.edu

b L aboratoire de Structure et de Dynamique des Systemes Moleculaires et Solides (UMR 5636),

Universite de Montpellier 2, CC 14, Place E. Bataillon, 34095 Montpellier cedex 5, France.

E-mail: odile.eisenstein=lsd.univ-montp2.fr

Received (in New Haven, CT) 16th September 1999

Dehydrohalogenation of RuH Cl L (L \ PPri ) gives (RuHClL ) , shown to be a halide-bridged dimer by X-ray

2

2 2

3

2 2

crystallography; the Ñuoride analog is also a dimer. (RuHClL ) reacts with N , pyridine and C H (L@) to give

2 2

2

2 4

RuHClL@L , but with vinyl ether and vinyl amides, H C2CH(E) [E \ OR, NRC(O)R@] such oleÐn binding is

followed by isomerization to the heteroatom-substituted carbene complex L HClRu2C(CH )(E). The reaction

mechanism for such rearrangement is established by DFT(B3PW91) computations, for C H as oleÐn (where it is

found to be endothermic), and the structures of intermediates are calculated for H C2C(H)(OCH ) and for cyclic

and acyclic amide-substituted oleÐns. It is found, both experimentally and computationally, that the amide oxygen

is bonded to Ru, with a calculated bond energy of approximately 9 kcal mol~1 for an acyclic model. Less

electron-rich vinyl amides or amines form g2-oleÐn complexes, but do not isomerize to carbene complexes.

Calculated *E values for selected ““competitionÏÏ reactions reveal that donation by both Ru and the

heteroatom-substituted X are necessary to make the carbene complex L HClRu2C(X)(CH ) more stable than the

2

3

4

2

3

2

3

oleÐn complex L HClRu(g2-H C2CHX). This originates in part from a diminished endothermicity of the

2

oleÐn ] carbene transformation when the sp2 carbon bears a p-donor substituent. The importance of a hydride on

Ru in furnishing a mechanism for this isomerization is discussed. The compositional characteristics of Schrock and

Fischer carbenes are detailed, it is suggested that reactivity will not be uniquely determined by these characteristics,

and these new carbenes RuHCl[C(X)CH ]L are contrasted to Schrock and Fischer carbenes.

3

2

We reported recently1 that 16-electron Ru(H) Cl L (L \

uents on a vinylic carbon, as well as those carrying donor

functionality at more remote sites. This furnishes an unusually

simple preparation of a class of carbene ligands that does not

rely on the conventional routes to carbenes: alkali metal

alkyls and a-H abstraction [e.g., eqn. (3)], diazoalkanes [eqn.

(4)], and addition of nucleophile, then electrophile to metal

carbonyls [eqn. (5)]. This new method relies on the sponta-

neous (i.e., exothermic) rearrangement of free, then coordi-

nated vinyl ethers to carbene complexes by a ruthenium

monohydride [eqn. (6)]. In this paper, we investigate experi-

mentally the scope of this reaction, as well as the origin of this

thermodynamic preference using DFT calculations. The calcu-

lations will lead to a further clariÐcation of these results in

terms of the two ““classesÏÏ of carbene ligands, the ““Schrock

typeÏÏ as formed in eqns. (3) and (4), and the ““Fischer typeÏÏ, as

produced in eqn. (5).

2

2 2

PPri ) can be dehydrohalogenated to give 14-electron

3

RuHClL , which has an unusual structure of a cis-divacant

2

octahedron [eqn. (1), but vide infra].

We have come to see that one special advantage of this

geometry is that it has two empty sites cis and trans to H.

Coordination of the substrate occurs preferably trans to Cl

(smaller trans inÑuence) and thus cis to H. This can facilitate

the interaction between RuH and substrate. In contrast, the

strong trans e†ect of hydride puts the empty orbital of Ðve-

MCl ] 2 RCH Li ] M(CH R) ] M(CHR) ] RCH (3)

2

3

coordinate d6 16-electron species of the MHX(CO)L , etc.,

2

M ] N CHR ] M(CHR) ] N

(4)

type trans to the hydride [eqn. (2)]

2

`

E

M(CO) ] Nu ÈÈÈ M(CO)Nu ÈÈÈ

[M2C(OE)(Nu)]` (5)

RuH

H C2C(OR)H ÈÈÈ HRu2C(OR)(CH )

(6)

2

3

and the resulting adduct is thus less suitable for rapid reaction

between H and substrate S. This has major impact on the

kinetics of substrate transformation.2

Results

We report here a wide-ranging study of the surprising ways

(RuHClL )

in which RuHClL rearranges oleÐns bearing p-donor substit-

2 2

This molecule is synthesized over a 12 h period in pentane

2

¤ Non-SI units employed: 1 torr B 133 Pa; 1 kcal B 4.18 kJ.

[eqn. (1)]. The molecule shows diastereotopic Pri methyl

New J. Chem., 2000, 24, 9È26

This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2000

9

View Article Online

is insigniÐcant, and the reagent will be written here as the

monomer for simplicity.

RuHClL and equimolar pyridine form a 1 : 1 adduct in

2

benzene within the time of mixing. The hydride chemical shift,

[20.9 ppm, is sufficiently upÐeld to suggest that there is no

ligand trans to hydride, and the coordinated pyridine shows

Ðve proton and Ðve 13C chemical shifts, consistent with no

facile rotation about the Ru ^ N bond. This is a symptom of

a crowded environment, and addition of two equivalents of

pyridine reveals formation of two new species, in addition to

RuHClL (py), which are assigned as bispyridine adduct

2

RuHClL (py) (a) and Ðve-coordinate RuHClL(py) (b). The

2

downÐeld hydride chemical shift of a ([12.9 ppm, t, 2J

14 Hz) and the upÐeld signal with loss of coupling to one

\

PvH

phosphine (free phosphine is also observed) for b ([20.0 ppm,

d, 2J \ 30 Hz) support these assignments and help illus-

PvH

trate this crowding.

The methyl protons of RuHCl(PPri ) exchange over a

3 2

period of several hours with the deuterons of C D . Presum-

6

ably this takes place by generation of RuDCl(PPri ) and

C D H, followed by the ruthenium deuteride scrambling into

the phosphines as discussed below. The phenomenon is

3 2

6

5

detected by 1H NMR via a large increase in the protio signal

of benzene-d , coupled with a decrease and broadening of the

6

Fig. 1 ORTEP drawing of the nonhydrogen atoms of

RuHCl(N )(PPri ) showing selected atom labeling. The hydride was

signals for RuÈH and the Pri methyl groups when

RuHCl(PPri ) is placed in a Ñame-sealed NMR tube and

2

3 2

not located.

3 2

periodically monitored for 2 days.

hydrogens, which not only rules out a planar structure, but

was interpreted earlier as indicating a ““saw horseÏÏ monomeric

structure A. Both the 1H and the 31PM1HN NMR spectra show

only broadening, but no clear decoalescence at [95 ¡C in

Reactivity of RuHClL towards hydrocarbon oleÐns

2

RuHClL binds ethylene (1 atm or equimolar, 20 ¡C) to give a

2

1 : 1 adduct. The hydride chemical shift, [ 22.0 ppm, is still

toluene-d . Crystals grown for an X-ray di†raction structure

sufficiently upÐeld to suggest that there is no ligand trans to

hydride, consistent with structure B.

8

determination reveal the molecule to be the dimeric [RuH(l-

Cl)L ] .3 The Ñuoride analog has also been shown to be a

2 2

dimer by both multi-nuclear NMR and X-ray crystallography.

However, since RuHClL forms an adduct (see Fig. 1 and

2

Tables 1 and 2) with a reagent as weak as N (1 atm, 25 ¡C,

2

time of mixing), the inhibiting inÑuence of the chloride bridges

Table 1 Crystallographic data

RuHCl(PPri ) (C H NO)

3 2

RuHCl(N )(PPri )

3 2

6

9

2

Formula

Formula weight

C

569.15

H

ClNOP Ru

C

H

ClN P Ru

24 52

2

18 43

486.02

2 2

Crystal system

monoclinic

Space group

a/Ó

P2 /a

P2 /c

1

16.124(5)

7.9985(10)

b/Ó

11.289(4)

16.313(5)

100.30(1)

2921.59

4

8.9047(11)

16.614(2)

92.180(10)

1182.5(2)

2

c/Ó

b/0

U/Ó3

Z

T /¡C

[ 171

k(MoK )/cm~1

7.5

9.0

a

Meas. reÑections

5136

4692

0.027

0.0460

0.0349

6389

6212

0.030

0.0346

0.0675

Indep. reÑections

R

int

Ra

R

a

w

a R \ & p F o [ o F p /& o F o ; R \ [&w( o F o [ o F o )2/&w o F o 2]1@2 where w \ 1/p2( o F o ).

o

c

o

w

o

c

o

Table 2 Selected bond distances (Ó) and angles (¡) for RuHCl(N )(PPri )

3 2

2

Ru(1)ÈCl(2)

2.396(4)

2.3727(10)

89.29(13)

90.71(13)

90.8(5)

Ru(1)ÈN(13)

1.84(2)

1.10(2)

89.2(5)

175(2)

Ru(1)ÈP(3)

N(13)ÈN(14)

Cl(2)ÈRu(1)ÈP(3)

Cl(2)ÈRu(1)ÈP(3)d1

P(3)ÈRu(1)ÈN(13)

P(3)d1aÈRu(1)ÈN(13)

Ru(1)ÈN(13)ÈN(14)

a P(3)d1 is related to P(3) by the inversion center.

10

New J. Chem., 2000, 24, 9È26

View Article Online

Although this is the ground state structure of this molecule,

reaction of RuHClL with excess C D in C H for 1 h at

cal shift for R \ Et (Table 3) to those for all components with

functionalized alkyl groups in eqn. (7) suggests that none of

the latter O, N or F donors coordinates to Ru.4 Perhaps this

is caused by the difficulty of forming six-membered rings. For

the case of F, this conclusion is reinforced by a 19F chemical

shift that lies within 1 ppm of that of the free oleÐn, and by

the absence of coupling to F in the 31P NMR spectrum. Even

at [80 ¡C, 19F NMR spectra reveal that F remains uncoordi-

nated.

2

4

6 6

20 ¡C shows (2H NMR) deuteration of the H on Ru and also

the methyl groups of coordinated PPri . This is indicative of

3

reversible insertion of C D into the RuÈH bond and it also

2

4

indicates that the 16-electron oleÐn hydride form (B) is more

stable than Ru(C H )ClL . Deuteration of the Pri methyls is

2

5

2

accounted for by reversion to RuDCl[P(CH(CH ) ) ] and

3 2 3 2

then CH /RuD scrambling, as was independently established

3

for this species deuterated by two independent methods. Inser-

tion of ethylene into RuÈH is also evidenced by the formation

of ethane, detected by 1H NMR. Its formation most likely

occurs by alkane elimination from unstable Ru(C H )ClL ,

2

5

2

which has oxidatively added an Pri methyl group (CÈH). This

CÈH activation also o†ers an additional explanation for deu-

teration of the Pri methyl with C D . The metal-containing

2

4

products after CH CH elimination could not be identiÐed.

3

There is no isomerization of ethylene into the carbene ligand

CH(CH ).

When O is from an epoxide ring, the presence of a chiral

carbon b to the vinyloxy oxygen necessitates phosphine ine-

quivalence. From the magnitude of their 31PM1HN NMR (Fig.

2) chemical shift di†erence [*d \ only 0.09 ppm (15 Hz),

3

RuHClL also reacts within 30 min with the oleÐns 1-

hexene and styrene, but only 10% adduct is formed, with

unreacted RuHClL comprising the bulk of the resulting

mixture at 25 ¡C. Both these adducts are identiÐed by a new

2

2J \ 220 Hz], it is safe to assume that the chiral center is

PvP

hydride signal in 1H NMR ([23.7 ppm, m, for 1-hexene and

far from the phosphorus atoms, indicating no epoxide binding

[22.1 ppm, apparent triplet, for styrene) and corresponding

to ruthenium.

31PM1HN NMR AB patterns centered at 37.2 ppm (2J \ 287

The case of dihydrofuran [eqn. (8)] is interesting as it shows

that a cyclic internal vinyl ether is also easily isomerized.5 The

hydride chemical shift is consistent with no donation to Ru by

PvP

Hz) for 1-hexene and at 85.9 ppm (2J \ 34 Hz) for styrene.

PvP

The spectroscopic similarity of the ethylene, 1-hexene, and

ethyl vinyl ether adducts and large di†erence of the styrene

adduct suggests that styrene may coordinate di†erently

(perhaps as g2 : g1h2-vinyl : arene or g2h4-arene). Longer reac-

tion times yield no carbenes, but only complex mixtures of

products.

Reactivity of RuHClL towards vinyl ethers

2

RuHClL rapidly e†ects a formal 1,2-hydrogen migration

2

[eqn. (7)] of vinyl ethers into the coordinated carbene. The

reaction occurs for a variety of groups R, including those with

SiMe , ether, alcohol, tertiary amino, Ñuoro, and epoxide

3

functionality. All products show diastereotopic Pri methyl

groups, consistent with the presence of three di†erent substit-

uents, H, Cl and carbene, on Ru. While this reveals nothing

about the square pyramidal vs. trigonal bipyramidal geometry

around Ru, the hydride chemical shifts (Table 3), rather far

upÐeld ([21 ppm), could be interpreted in terms of the

hydride being approximately trans to an empty site (i.e.,

square pyramidal). The hydride chemical shift is thus also

perhaps the most generally sensitive indicator of whether

there is a ligand (from functionality in the substituent R) coor-

dinated trans to hydride. The similarity of the hydride chemi-

Fig. 2 31PM1HN

NMR

(162

MHz)

spectrum

of

RuHCl[C(Me)(OCH CHOCH )](PPri ) , showing the inequivalence

2

3 2

of the phosphorus nuclei caused by the epoxide carbon asymmetry.

Starred peaks are impurities and the arrows indicate the outer lines of

the AB pattern.

Table 3 Selected NMR data as a function of carbene substituent in C D

6

d RuÈH

2J /Hz

d Ru2C

2J /Hz

PvC

d RuÈP

PvH

Vinyl ethers

OEt

[21.7

[18.2

[19.4

[18.0

[21.3

[21.1

[21.4

[21.2

[21.3

[21.4

23

22

23

22

21

22

c

290

287

b

284

289

b

289

b

9.7

9.4

b

8.4

9.5

8.4

b

9.1

b

58.2

60.1

57.4

58.6

57.8

56.4

56.3

57.9

57.8

56.4

57.7

OCH CH CH Èa,d

2

OCy

OSiMe

3

OCH CH OBun

2

CH CH OH

2

(OCH CH ) OH

2 2

ÈOCH CH OÈe

2

OCH CH F

2

OCH CH NEt

2

OCH CHOCH

22

b

2

Vinyl amides

N(Me)C(O)Mef

[17.2

[19.6

26

265

262

9.7

10

50.4

49.3

NC(O)CH CH CH Èd,f

2

a 1H data reported in CD Cl . b Not measured. c Not resolved (broad). d Cyclic. e Dimetal carbene. f All NMR data in CD Cl .

2

2 2

New J. Chem., 2000, 24, 9È26

11

View Article Online

the ether b-oxygen, just as it does not occur for the products

in eqn. (7). Using the symmetrical difunctional vinyl ether as

in eqn. (9), with slow addition of the vinyl ether to RuHClL ,

2

a dimetal carbene is produced.

RuHCIL ] 1/2 CH 2CH(OCH CH O)CH2CH ]

2

L CIHRu2C(Me)(OCH CH O)(Me)C2RuHCIL (9)

2

The presence of inequivalent (i.e., H and Cl) substituents on

Ru, together with the carbene plane not eclipsing the RuP

plane,6 makes two isomers (C and D) possible for an unsym-

metrically substituted carbene, CRR@. Indeed, upon lowering

2

the temperature in toluene-d , one observes broadening, then

8

decoalescence and sharpening of the RuÈH, the CÈCH and

3

the OCH 1H NMR signals of two isomers (C and D) with a

2

Fig. 3 31PM1HN NMR monitoring of reaction progress when

RuHClL and H C2CH(OEt) are combined at [65 ¡C in toluene-d .

population ratio of more than 10 : 1. The 31PM1HN NMR con-

2

8

Doublet in RuHClL signal is due to incomplete hydride decoupling.

2

Ðrms this, with decoalescence at about [50 ¡C and two

separate resonances (major isomer at 55.8 and minor at 51.2

ppm) resolved below [70 ¡C. Lineshape analysis of the

31PM1HN NMR spectrum gives *G” \ 9.8 kcal mol~1 for

C ] D at [60 ¡C. The assignment of isomer structure to

spectra was done by NOE experiments of the hydrides at

[95 ¡C. The large (5 ppm) di†erence in the hydride chemical

shift of these isomers supports their being isomeric around the

Ru2C bond and not around the C(carbene)ÈOEt bond. These

observations are signiÐcant because (1) no previously known

compound has had suitable symmetry to prove that carbene

rotation is rapid at 25 ¡C and (2) carbene rotation is an essen-

tial step in the oleÐn metathesis6 process (i.e., forming the

metallacyclobutane).

Arrow shows initial growth of carbene product at 0 ¡C.

clear that RuÈH adds in both directions to the oleÐn, but only

one of these leads to carbene product; the regiochemistry of

carbene production is not caused by selectivity in the initial H

migration step. By 0 ¡C, carbene product grows in, with D

both at Ru (25%) and at the carbene methyl (75%). Thus,

attempts to establish mechanism by quantitative comparison

to the predictions of eqn. (10) are frustrated by general isotope

scrambling.8 However, the signiÐcantly slower reaction rate

observed using H C2CD(OEt) establishes that CÈD cleavage

2

occurs before or at the rate determining step. From the scram-

bling patterns observed, we propose that the most likely

mechanism of carbene formation combines mechanism b of

Scheme 1 and eqn. (10).

Mechanism. The reaction of equimolar RuHClL with ethyl

2

vinyl ether is immediate and complete at [65 ¡C in toluene-

d

to give a primary product whose 31P and 1H NMR are

8

consistent with a 1 : 1 oleÐn adduct. The 31PM1HN NMR (Fig.

3) is an AB pattern (J_PvPB\ 300 Hz), indicating that the

unsymmetrical oleÐn substituents are bound such that the

phosphines are inequivalent (but transoid).7

Carbene product formation demands cleavage of the CÈD

bond in H C2C(D)(OEt), but at least three mechanisms

2

(Scheme 1) can be envisioned: (a) direct CÈD oxidative addi-

tion to the ruthenium hydride, followed by hydrogen migra-

tion to the vinyl C , (b) primary addition of RuÈH to C2C,

followed by a-hydrogen migration to Ru, (c) concerted 1,2-

Reactivity of RuHClL towards vinyl amides

b

2

The vinyl amides are also transformed into the carbenes

shown in eqn. (11). The chemical shifts of the carbene carbon,

of the hydride, and of 31P are all sufficiently di†erent from

those in eqn. (7) to suggest the possibility of amide oxygen

coordination. Interestingly, there is a large di†erence in the 1H

NMR chemical shift of RuÈH and in the m(CO) of the pendant

hydrogen migration within the coordinated oleÐn. These have

distinct predictable consequences for the deuterium label since

(a) mixes RuH with CÈD, (b) migrates D exclusively to Ru

only after the RuÈH has been cleaved, and (c) migrates D

exclusively to the CH carbon. In fact, when RuHClL and

2

H C2CD(OEt) are combined at [40 ¡C and observed by 2H

2

NMR beginning at [20 ¡C, one sees immediately

RuDCl(oleÐn)L in which there is also D in the phosphine

2

methyl groups, and some free HDC2CH(OEt). These indicate

reversible oleÐn binding to Ru and reversible migration of H

(or D) from Ru to both oleÐnic carbons [eqn. 10)].

The scrambling of D into the phosphine methyls was already

established as a characteristic of RuDClL itself. It is thus

2

12

New J. Chem., 2000, 24, 9È26

View Article Online

Scheme 1

amide between the products from cyclic and acyclic vinyl

amides (R,R@ \ Me: d \ [17.2 m(CO) \ 1599 cm~1; R,R@ \

CH CH CH : d \ [19.6 m(CO) \ 1640 cm~1). These data

2

show that while both compounds may have C2O metal-

bound, the geometric constraints at the cyclic species hinder

its binding relative to the carbene derived from acyclic N-

methyl-N-vinyl acetamide. Carbonyl oxygen coordination was

conÐrmed by an X-ray crystal structure determination for the

product from 2-vinyl pyrrolidinone (Table 4 and Fig. 4). The

structure is derived from the Ðve-coordinate carbene complex-

The amide reactions proceed considerably slower than

those with vinyl ethers, taking 2È4 days to react completely.

After 1 h in C D , the mixture of 2-vinyl pyrrolidinone and

6

RuHClL exhibits 1H and 31P NMR signals for three major

2

intermediates, as well as for starting material and Ðnal

es Ru(carbene)Cl(H)L by addition of the pendant carbonyl

functionality of the carbene in the site trans to hydride. The

product. One intermediate exhibits an AX pattern (d 57.6,

2

33.4; 2J \ 274 Hz) in the 31P spectrum and an apparent

PvP

inner coordination sphere has idealized mirror symmetry,

which extends even to the conformations of all Pri groups.

Bond angles in the six-coordinate polyhedron are generally

within 10¡ of the ideal 90¡, except for within the Ðve-

membered ring of the bidentate carbene/amide ligand

[79.45(17)¡]; also the phosphorus nuclei deviate visibly from

octahedral symmetry [nPÈRuÈP \ 158.67(5)¡] and they bend

main ly towards hydride and sligtly towards chloride. The

RuÈC(carbene) distance is short (but not as short as to a car-

bonyl ligand9) and the distance to Cl trans to carbene is

unusually long [2.5387(14)A]. The Ru ^ O distance is not

especially long, in spite of its being trans to hydride. There is

no trace of interaction between the mutually cis ligands

hydride and carbene; hydride lies in the nodal plane of the

Ru2C bond. The distance from N28 to the carbene carbon is

8p (0.063 Ó) longer than to the carbonyl carbon (C24), which

suggests that the NÈC p bond is more in the amide group, and

less to the carbene carbon [eqn (12)].

triplet in 1H NMR (d [29.2, 2J \ 34.8 Hz) while the other

PvH

two show singlets in 31P (d 85.6, 74.7) and RuÈH doublets in

1H (d [10.1, [19.6; 2J \ 33.0, 35.1 Hz, respectively).

PvH

These latter intermediates are consistent with dissociation of

phosphine and indeed free phosphine is observed by 31P

NMR. Upon completion of the reaction, phosphine re-

coordination occurs, with the only product seen being the

amido-substituted carbene. Although the exact nature of all

intermediates cannot be inferred (coordination by oleÐn, N,

g2-carbonyl, or a combination of these groups all produce

inequivalent phosphines), the multiple coordination modes of

vinyl amides, coupled with the possibility of required phos-

phine dissociation, help explain the kinetic sluggishness of this

reaction.

Reaction of equimolar RuHClL and N-vinyl phthalimide

2

leads to E, which does not rearrange to a carbene isomer over

20 h at 25 ¡C. After this time, substantial decomposition of

product occurs in solution. Complex E shows inequivalent

Table 4 Selected bond distances (Ó) and angles (¡) for RuHCl(PPri ) (C H NO)

3 2

6

9

Ru(1)ÈCl(2)

2.5387(14)

2.3658(15)

2.3664(15)

2.273(3)

O(23)ÈC(24)

1.245(6)

1.350(6)

1.476(6)

1.413(6)

1.25(4)

Ru(1)ÈP(3)

N(28)ÈC(24)

Ru(1)ÈP(13)

N(28)ÈC(27)

Ru(1)ÈO(23)

N(28)ÈC(29)

Ru(1)ÈC(29)

1.880(5)

Ru(1)ÈH(1)

P(3)ÈRu(1)ÈP(13)

P(3)ÈRu(1)ÈO(23)

P(3)ÈRu(1)ÈC(29)

P(13)ÈRu(1)ÈO(23)

P(13)ÈRu(1)ÈC(29)

O(23)ÈRu(1)ÈC(29)

Ru(1)ÈP(3)ÈC(4)

Ru(1)ÈP(3)ÈC(7)

Ru(1)ÈP(3)ÈC(10)

Ru(1)ÈP(13)ÈC(14)

Ru(1)ÈP(13)ÈC(17)

Ru(1)ÈP(13)ÈC(20)

Ru(1)ÈO(23)ÈC(24)

C(24)ÈN(28)ÈC(27)

158.67(5)

99.96(10)

92.84(14)

100.57(10)

96.51(14)

79.45(17)

116.40(19)

114.40(7)

112.53(18)

113.92(18)

115.80(19)

113.68(20)

106.2(3)

C(24)ÈN(28)ÈC(29)

C(27)ÈN(28)ÈC(29)

Ru(1)ÈC(29)ÈN(28)

Ru(1)ÈC(29)ÈC(30)

N(28)ÈC(29)ÈC(30)

Cl(2)ÈRu(1)ÈH(1)

P(3)ÈRu(1)ÈH(1)

P(13)ÈRu(1)ÈH(1)

O(23)ÈRu(1)ÈH(1)

C(29)ÈRu(1)ÈH(1)

Cl(2)ÈRu(1)ÈP(3)

Cl(2)ÈRu(1)ÈP(13)

Cl(2)ÈRu(1)ÈO(23)

Cl(2)ÈRu(1)ÈC(29)

118.0(4)

129.8(4)

114.7(3)

133.8(4)

111.5(4)

96.4(16)

78.3(16)

82.1(16)

171.9(16)

92.7(16)

88.06(4)

85.71(5)

91.47(9)

170.90(15)

112.2(4)

New J. Chem., 2000, 24, 9È26

13

View Article Online

nitrogen is not the donor site in the observed adduct since the

phosphines are inequivalent, as they would be in a p-oleÐn

structure.

Reactivity with a conjugated diene ether substrate

Addition of 10 equiv. of the conjugated diene, 3-methylene-

2,3-dihydrofuran, to a solution of RuHCl(PPri ) in C D

3 2

6 6

results in complete isomerization to 3-methylfuran within 10

min. [eqn. (13)].

No reaction occurs from 3-methylfuran with RuHCl(PPri ) at

3 2

room temperature over several hours. This isomerization is

consistent with addition of RuÈH across the terminal alkene

to give the tertiary alkyl, followed by b-H elimination to

achieve aromatic stabilization in the resulting furan.

DFT computation of the ethylene Ç methyl carbene

isomerization

The isomerization of free ethylene into free methyl carbene is

known to be a very endothermic reaction (80 kcal mol~1).

Recent laser Ñash photolysis experiments and ab initio calcu-

lations on propene have shown that the energy of reaction is

60 kcal mol~1 endothermic.10 Isomerization of free oleÐn is

thus unlikely to happen in less extreme conditions (i.e., in

solution).

The reaction path for transforming ethylene into its isomer

C(H)CH in the presence of RuHCl(PH ) [Ru] (as a model

3

3 2

for RuHClL ) was determined with DFT(B3PW91) calcu-

2

lations (Fig. 5). As mentioned earlier, the 14-electron fragment

RuHClL does not exist as an isolated species. However, it is

2

a reasonable assumption to consider that the oleÐn causes the

dissociation of the dimer into two monomeric RuHClL ,

2

which is stabilized through coordination to the oleÐn. For the

Fig. 4 ORTEP drawing of the nonhydrogen atoms of RuHCl-

[C(Me)NC(O)CH CH CH ](PPri ) , showing selected atom labeling.

sake of discussion, we will consider that the starting entities

2

3 2

are thus [Ru] and C H .

2

4

The oleÐn coordinates [Ru] trans to Cl to form a 16-

electron intermediate 1, which is a square-based pyramid with

hydride at the apical site. This adduct has the classical

geometry of numerous Ðve-coordinate d6 species. The oleÐn is

coordinated opposite to the ligand with the smaller trans

inÑuence (Cl). This combination of ligands on the metal forces

the oleÐn to be cis to the hydride, which is favorable for

further reaction between these two ligands. The orientation of

the oleÐn also is a favorable factor since the C2C bond is

found to be aligned with RuÈH. This preferred orientation

minimizes the steric e†ect between the phosphine ligands and

the oleÐn and maximizes the stabilizing cis interaction

between the hydride and the oleÐn,11 although it should be

noted that the cis e†ect alone does not make the oleÐn tilt

toward H. The oleÐn adduct has no other remarkable struc-

tural aspects. The binding energy of [Ru] to C H is quite

phosphines, with 31P chemical shifts of 35.4 and 57.9 ppm and

a J of 278 Hz. These values are very close to those of the

PvP@

bis phosphine intermediate detected in reaction with 2-vinyl

pyrrolidinone. The large di†erence in chemical shift of the car-

bonyl groups by 13CM1HN NMR (10 ppm), coupled with a

hydride chemical shift similar to the carbenes from vinyl

amides, lends evidence for oxygen coordination. Thus, while

one keto group on N permits isomerization to a carbene

complex, two keto groups apparently leave the nitrogen too

weak a donor to stabilize a carbene.

2

4

large (39.2 kcal mol~1), which characterizes the high unsatu-

ration of [Ru]. The insertion of the oleÐn into the RuÈH bond

is a facile process since the transition state is found to be only

7.6 kcal mol~1 above 1. It produces an ethyl complex, 2,

which is less stable than 1 by 6.2 kcal mol~1. This ethyl

complex has a remarkably strong b agostic CÈH bond since

It is of interest that 9-vinylcarbazole (F) is not too bulky to

bind to RuHClL , but the reaction does not proceed to a

2

carbene complex, perhaps because the nitrogen lone pair is

too involved in the arene p system to stabilize the electrophilic

carbene G, which would also be very crowded. It is clear that

the C ÈH bond length is equal to 1.221 Ó, while RuÈH is sig-

b

niÐcantly short, 1.774 Ó. At the same time, the CÈC bond

length is signiÐcantly shorter (1.482 Ó) than that of a single

CÈC bond and the two RuÈC distances do not di†er greatly

(2.070 Ó and 2.293 Ó), although the initial di†erence in bond

lengths between RuÈC and RuÈC has been increased. The

a

b

transition state TS1-2 between 1 and 2 has the expected fea-

tures of an unsaturated ligand inserting into an RuÈH bond:

the ethylene is more unsymmetrically bonded (RuÈC \ 2.107,

a

14

New J. Chem., 2000, 24, 9È26

View Article Online

Fig. 5 DFT(B3PW91) optimized structures and energies for RuC H Cl(PH ) isomers.

3 2

2

5

RuÈC \ 2.215 Ó) than in 1 and less than in 2. However, in a

break the unusually strong C ÈH agostic bond in addition to

b

nonintuitive manner, C has moved closer to Ru than it was in

rotating about the single RuÈC bond. The transition state

b

a

1, in an apparent attempt to assist in HÈC bonding. The CÈC

TS2-3 has no agostic interaction (closest RuÉ É ÉH distance \

b

bond length (1.444 Ó) is intermediate between that in 1 and in

2.6 Ó) and thus the CÈC bond length is typical of that of a

single bond (1.523 Ó). The rotation of the ethyl group leads to

3, where the ethyl group has an a agostic hydrogen. The

energy of this intermediate is 9.8 kcal mol~1 above 2. This is

in great part due to the large di†erence in the strength of the

2. The main change in structure is thus the displacement of H

as measured by the ClÈRuÈH angle (97.6¡, 144.0¡, 159.0¡ as

one goes from reactant to product). According to the

Hammond postulate, TS1-2 should resemble more 2, to which

it is closer in energy, and this is true for the ClÈRuÈH angle

and the RuÈC distance. However, the behavior of Ru-C

agostic interactions. In 3, C ÈH (1.13 Ó) is much less elongated

a

than C ÈH in 2 and, consequently, the agostic H is much

(a

b

illustrates some limitation in using the Hammond postulate.

further away from Ru (2.334 Ó in 3). In addition, the CÈC

With regard to forming the HRu2C(H)Me moiety, the

geometry of 2 is poorly adapted for migrating a hydrogen

bond (1.517 Ó) is close to that of a single CÈC bond.

Since rotation about the RuÈC bond is energetically

a

from C to the metal. Rotation of the ethyl group is thus

demanding, we searched for an alternative path. Inversion at

a

necessary to put an a hydrogen in proximity to the nearest

the metal center would achieve the requirement to put an a

hydrogen in proximity to an empty metal orbital. The tran-

sition state, TSº2-3, for this transformation was located 33.1

empty orbital of the metal. Rotation of the ethyl is energeti-

cally demanding (12.1 kcal mol~1) since it is necessary to

New J. Chem., 2000, 24, 9È26

15

View Article Online

kcal mol~1 above 2. The geometry of this TS is square planar.

Its high energy shows the strong energetic preference for a

bent geometry at a d6 four-coordinate center.

The carbene complex is fully formed since the carbon bonded

to the metal is planar (sum of the angles at C \ 360¡). The

RuÈC distance is equal to 1.879 Ó, very close to that in the

Ðnal product (1.855 Ó). The RuÈH bond is also almost fully

formed (1.670 Ó) vs. 1.606 Ó in 4. The major di†erence

between TS3-4 and 4 lies in the angles between the three

ligands. The ClÈRuÈC angle varies from 145.0¡ (TS3-4) to

129.5¡ (4), while nHÈRuÈC varies from 53.5 to 87.9¡, accord-

ingly. In this last step of the reaction path, as well as in the

step of the insertion of ethylene into the RuÈH, there is no

synchronous variation of all the coordinates from reactants to

products (in contrast to the predictions of the Hammond

postulate).

The a migration from 3, to the Ðnal hydrido carbene

complex 4, is an easy process (*E” \ 6.4 kcal mol~1).

Remarkably, 3 and 4, although they are very di†erent in

bonding and in formal valence electron count, are iso-

energetic. Whatever determines the energies of both of these is

responsible for [Ru] being unable to isomerize ethylene to

ethylidene: the oleÐn form 1 is more stable and even the b

agostic ethyl, 2, which the calculations suggest to be

kinetically accessible at 25 ¡C, is signiÐcantly more stable than

3 and 4. This accounts for the deuterium scrambling and the

absence of an observable quantity of ethylidene complex in

the reaction of C D .

DFT computation of the vinyl ether Ç alkoxy carbene

isomerization

2

4

The model chosen for CH 2C(H)OR is CH 2C(H)OCH . The

2

3

geometry of the vinyl ether coordinated to [Ru] has been

optimized (Fig. 6). The overall geometry is that of a square

pyramid with an apical hydride ligand. The oleÐn prefers to

coordinate the metal in the mirror plane of the molecule, as

does ethylene. Even in the absence of large phosphines, the

conformation observed experimentally is thus shown to be

preferred. Both isomers 5 and 6 (Fig. 6) are found to be

minima on the potential energy surface with a preference of

0.9 kcal mol~1 for 6. This almost negligible di†erence in

energy is not due to an OÉ É ÉRu interaction in 6 since the

oxygen is outside of the bonding range to the metal (RuÉ É ÉO

distanceT3 Ó).

The Ðnal product 4 has the geometry of a trigonal bipyra-

mid distorted towards a Y shape through large ClÈRuÈC

(129.5¡) and ClÈRuÈH (142.5¡) angles. The plane of the

carbene eclipses the PÈRuÈP axes. This conformation permits

the empty carbene p orbital to interact with the highest

occupied d Ru orbital (H). Therefore, bulky phosphines could

force a rotation of the carbene plane. It has been shown that

the conformation of the carbene in the related

RuCl (PR ) (CHR) depends on the nature of the substituents

Comparing the ethylene and the CH 2C(H)OCH adducts,

2

3

it appears that the substitution by OCH has no signiÐcant

2

3 2

3

at the phosphine and carbene.6 The transition state TS3-4 to

form 4 has already many geometrical aspects of the Ðnal

product despite being energetically equidistant from 3 and 4.

e†ect on the geometry of the complex. In 6, there is a slight

decrease in the non-bonding distance between the unsub-

stituted carbon of CH 2C(H)OMe and Ru with respect to the

2

Fig. 6 DFT(B3PW91) optimized structures for isomeric RuC H (OCH )Cl(PH ) isomers.

3 2

2

4

3

16

New J. Chem., 2000, 24, 9È26

View Article Online

corresponding distance in the case of an ethylene ligand (2.19

Ó vs. 2.23 Ó), consistent with the slight attraction described

above. Remarkably, the RuÈoleÐn bond dissociation energy

(BDE B 39 kcal mol~1) is also not a†ected by the presence of

OCH (average di†erence of 3.0 kcal mol~1 with the greater

3

dissociation energy for ethylene). While OCH certainly

3

increases the electron-donating ability of the p system, it

decreases its p-accepting capability. These two e†ects act in

opposite directions to maintain the binding energy to the

metal constant. This emphasizes that [Ru], although strongly

electron-deÐcient, is not acting solely as a Lewis acid but cer-

tainly has important back-donating capabilities.

The structures of several conformations (all minima) of the

[Ru]2C(CH )(OCH ) isomer are also shown in Fig. 6. In the

3

two most stable conformations, the carbene is in the mirror

Fig. 7 Comparison of the inÑuence of substituent X on isomer sta-

plane of the molecule. These two conformations, 7 (OCH cis

bilities.

3

to H with respect to the Ru2C bond) and 8 (OCH trans to H

3

The presence of the p-donor group OCH has also signiÐ-

with respect to the Ru2C bond), are only 0.25 kcal mol~1

3

cantly decreased the di†erence in energy between the oleÐnic

apart and thus at the same energy. The conformation 9 with

the carbene plane perpendicular to the mirror plane is calcu-

lated to be 4.1 kcal mol~1 above the most stable conforma-

tion. Since 9 would be highly disfavored on steric grounds in

the real system, the two preferred conformations are 7 and 8.

Finally, a carbene complex in which the oxygen would coordi-

nate Ru (I) was sought as a minimum on the potential energy

surface without success. Any such structure optimized to 8.

No 18-electron C- and O-bonded carbene complex is more

stable than the 16-e unsaturated g1-bonded C(CH )(OCH )

adduct and its carbene isomers (Fig. 7). In the case of ethylene,

the isomerization was endothermic by 15.9 kcal mol~1. In the

case of vinyl ether, the isomerization is calculated to be essen-

tially thermoneutral. The isomer of the carbene complex with

the OMe group on C (9º) has been calculated to be 21.1 kcal

b

mol~1 above the most stable oleÐn adduct. The di†erence in

energy between the oleÐn adduct CH 2CHX and the carbene

2

isomer increases in the order X \ OMe on C (0), H (15.9)

a

OMe on C (21.1 kcal mol~1). Thus, the OMe group greatly

facilitates the formation of the isomer when positioned on C ,

but signiÐcantly disfavored the formation of carbene when on

b

3

species.

a

C . Despite the fact that the initial structure employed had O

b

in the vicinity of Ru, the optimized geometry of structure 9º

shows that O has moved away from the metal. The carbene

orientation and the coordination at Ru is similar to that of 9.

Despite the presence of unsaturation at Ru, the oxygen coor-

dination does not bring any stabilization. In fact, angles

RuÈC ÈC (132¡) and C ÈC ÈO (115¡) in 9º open to keep O

from being too close to the phosphine ligand. Thus, while

coordination of oleÐn does not show any signiÐcant prefer-

ence for having OMe at a given position (structure 5 and 6),

only 6 would lead to the carbene product.

The preferred orientation C(CH )(OCH ) is thus rotated by

3

90¡ with respect to that in 4, the C(H)CH complex. The coor-

3

dination around the metal is also di†erent for the two carbene

a

b

a

b

ligands. For C(H)CH , nClÈRuÈC is equal to 129.5¡ and

3

nClÈRuÈH is equal to 142.5¡. With the OCH substituent

3

nClÈRuÈC is 161.6¡ (7) and 167.5¡ (8), while nClÈRuÈH is

107.9¡ or 107.8¡, respectively. The coordination at the metal

has thus changed from a Y shape [C(H)Me] to a T shape

[C(CH )OCH ]. It should be noticed that the change from Y

It is especially illuminating to relate the di†erence in energy

between the unsubstituted or substituted oleÐn adduct and the

carbene complex to the corresponding values in the absence of

[Ru]. Thus, both the Ru fragment [eqn. (14) vs. (16)] and the

3

to T shapes at Ru is associated with the rotation of the

carbene and not solely with the presence of the OMe substit-

uent. Thus, in 9 where the C(Me)(OCH ) is perpendicular to

OCH substituent [eqn. (14) vs. (15)] drastically decrease the

3

the mirror plane, the coordination geometry at Ru is similar

isomerization energy of oleÐn into carbene since both can

to that of 4. The preference of di†erent carbene conformations

for the Y and T shape complexes has its origin in the back-

bonding from Ru to the carbene. In the Y shape, as mentioned

donate to the empty p orbital of the carbene. The competition

between [Ru] and OCH in donation to the same empty

3

carbene p orbital results in some interesting features in the

above, the highest occupied d orbital is d

carbene perpendicular to the mirror plane. In the T structure,

resulting in a

x²~y²

following isodesmic reactions.

C H ] C(H)CH *E \ 79.1 kcal mol~1

(14)

the d and d (J) orbitals are both destabilized by a Cl lone

2

4

3

xy

xz

pair and are thus each good candidates for back-donating

into carbene. An additional increase in back-bonding is

caused by bending the phosphine ligands away from the

carbene. This is only possible when the carbene lies perpen-

dicular to the RuÈP bonds as in 7 or 8 so that its p orbitals

CH C(H)(OCH ) ] C(CH )OCH *E \ 41.4 kcal mol~1

2

3

(15)

(16)

[Ru](C H ) ] [Ru]C(H)CH ) *E \ 15.9 kcal mol~1

2

4

3

[Ru](CH 2C(H)(OCH )) ] [Ru](C(CH )OCH )

can accept electrons from d

.

2

3

xz

*E \ 1.6 kcal mol~1 (17)

C H ] C(OCH )(CH ) ] CH 2CH(OCH )

2

4

3

2

3

] C(H)(CH ) *E \ 37.7 kcal mol~1 (18)

3

C H ] [Ru](C(H)CH ) ] C(H)CH

2

4

3

The OCH group acts as a p donor in the carbene and not

3

] [Ru](C H ) *E \ 63.2 kcal mol~1 (19)

in the oleÐn adduct as shown by the signiÐcantly shorter

2

4

C(sp2)ÈO bond in the former systems. The p donation of the

Eqn. (18) and (19) show that OCH and [Ru] independently

stabilize the carbene isomeric form with respect to the oleÐnic

3

OCH group weakens the electron donation from RuÈC as

3

proven by the comparison of 4 and 6 or 7 and 8, where the

form by large amounts. However, eqn. (20) [in comparison to

eqn. (19)] shows that [Ru] is less efficient in stabilizing

RuÈC bond is the shortest for C(H)CH .

a

3

New J. Chem., 2000, 24, 9È26

17

View Article Online

methoxycarbene than methyl carbene. This di†erence could be

optimized structure is in good accord with the experimental

structure (Fig. 8). All metal-to-ligand distances are close to the

experimental values with the exception of RuÉ É ÉO, which is

0.1 Ó too long. However, the calculated RuÉ É ÉO is sufficiently

short (2.370 Ó) to clearly indicate the presence of a RuÉ É ÉO

bond. The calculated geometry within the RuÈCÈNÈCÈO

moiety mimics closely the experimental values. The N center,

which is calculated to be planar, is closer to the C of carbonyl

due to the inÑuence of OCH on the oleÐn and/or the

3

carbene. However, there is no signiÐcant di†erence in BDE to

[Ru] for ethylene and CH 2CHOCH as shown by eqn. (21).

2

3

Thus, [Ru] stabilizes the non-substituted carbene signiÐcantly

better [eqn. (22)] than the C(CH )(OCH ). While OCH

3

diminishes the stabilizing inÑuence of [Ru] to the carbene due

to the fact that both are in competition to donate to the same

empty orbital of the carbene, it should be emphasized that the

(NÈC \ 1.382 Ó) than to C (1.391 Ó). The Ðve-membered ring

a

cooperative e†ect of both OCH and Ru is indispensable to

has the usual envelope shape.

3

compensate the large di†erence (79.1 kcal mol~1) in energy

The binding energy of oxygen to the metal can be estimated

from the di†erences in energy between 10 and optimized struc-

tures with no RuÉ É ÉO interaction. To save computational

time, a simpliÐed system 11 in which the Ðve-membered

pyrrole ring is truncated, has been selected. The optimized

structure of 11 (Fig. 8) gives results very similar to that of 10.

This model will thus be used for further study of the system.

The structure 12, lacking RuÉ É ÉO interaction and resulting

between the oleÐn and its isomeric carbene form [eqn. (14)].

CH 2C(H)OCH ] [Ru](C(CH )OCH ) ]

2

3

C(CH )OCH ] [Ru](CH 2C(H)OCH )

3

2

3

*E \ 39.8 kcal mol~1 (20)

[Ru](C H ) ] CH 2CHOCH ]

2

4

2

3

from a rotation about the C ÈN bond, was located as a

[Ru](CH 2CHOCH ) ] C H

a

2

3

2 4

minimum (Fig. 8). The energy of 12 is 8.6 kcal mol~1 higher

*E \ 2.6 kcal mol~1 (21)

[Ru](C(H)CH ) ] C(CH )OCH ]

than 11. Another minimum 13 (not shown), obtained from 12

by 180¡ rotation about the RuÈC bond, was located and is

a

3

calculated to be 9.8 kcal mol~1 above 11. The RuÉ É ÉO bond

[Ru][(C(CH )OCH )] ] C(H)CH

dissociation energy is thus estimated to be about 9 kcal

mol~1.

3

*E \ 25.8 kcal mol~1 (22)

There are some interesting geometry changes in going from

11 to 12. In losing the RuÉ É ÉO interaction, the carbene rotates

by 43¡ (13 has similar geometrical features). This unusual con-

formation of the carbene is thus intermediate between that of

C(H)CH and C(CH )(OCH ). There is an apparent corre-

DFT computational study of the amido carbene complex

The amido carbene complex in which PPri was replaced by

3

PH (10) was optimized with no symmetry restriction. The

3

Fig. 8 DFT(B3PW91) optimized structures for RuHCl(PH ) with amido oleÐns.

3 2

18

New J. Chem., 2000, 24, 9È26

View Article Online

lation between the donating power of the substituent on the

carbene and the conformation of the carbene in the complex.

We have seen that the orientation of the carbene was closely

connected to the coordination geometry at the metal [Y for

is a very high energy process ([60 kcal mol~1 for propene10

and 79.1 kcal mol~10 for ethylene in these calculations). The

presence of a transition metal complex has been shown to

facilitate the 1,2 shift in the case of alkyne to vinylidene.14 Our

calculations have shown that the multistep reaction initiated

by alkyne insertion into the RuÈH bond is considerably lower

in energy than the 1,2 shift. In the case of oleÐn, the 1,2 shift,

even if also facilitated by the metal, should remain energeti-

cally inaccessible. The presence of an additional H on the

metal is thus indispensable for the isomerization process.

The pathway presented here also explains the isotope label-

ing observation with C D . The isotope scrambling is

CHMe and

T for C(OMe)(Me)]. In the case of 11

(nClÈRuÈC \ 162.0¡ and nClÈRuÈH \ 114.5¡), the metal

a

coordination is also intermediate between the C(H)CH and

3

C(CH )OCH cases. In 12, the nitrogen (still planar) is closer

3

to C (1.380 Ó) than to the C(O) carbon (1.406 Ó) in contrast

a

to 11. The p donation of the nitrogen is thus more important

towards the carbene in 12 than in 11, due to the fact that the

electron accepting ability of the acyl group is no longer

enhanced by coordination to Ru.

2

4

explained by the oleÐn adduct entering the hydride migration

path, even if accumulation of the carbene complex is not ther-

modynamically possible.

Two oleÐn adducts, 14 and 15, with a NH(CO)(CH ) sub-

3

stituent have been optimized. Isomer 14 is 5.5 kcal mol~1

more stable than 15 and has the amide oxygen coordinated to

Ru with only a minor decrease in the PÈRuÈP angle (160.7¡ in

14 and 166.6¡ in 15). Thus, the more bulky phosphine used

experimentally should not prevent the coordination. The pro-

posal that O is coordinated to the metal in the oleÐn adduct

14 is supported by the structure of the oleÐn adduct of

Since the Ðnal complex is unsaturated, a study of the e†ect

of an electron-donating group remote from the oleÐnic func-

tion has been studied. It was hoped that this would stabilize

the Ðnal carbene by coordination to the unsaturated site. With

the exception of the amide function where the O is positioned

in close proximity to the metal and thus has been shown to

coordinate, it has been observed that a more remote function-

ality does not interact with the metal. This illustrates the rela-

tively poor Lewis acidity of Ru with a hydride trans to the

empty site.

CH 2CH(phthalimide).

2

The di†erence in energy between the most stable oleÐn

complex 14 and the more stable carbene isomer 11 is calcu-

lated to be 3.1 kcal mol~1 in favor of the oleÐn adduct (Fig.

7). This small di†erence in energy, together with inclusion of

steric e†ects (which favor the carbene over oleÐn complex),

accounts for the fact that isomerization of the oleÐn substi-

tuted by the amido group has been observed. In this case, two

factors contribute to make the carbene isomer energetically

accessible: p donation of the nitrogen amide and coordination

of the amide oxygen to Ru, which in turn probably enhances

the electron-donating ability of Ru toward the carbene. It is,

however, probable that p donation of the nitrogen lone pair is

a major component since no isomerization is observed in the

case of vinyl phthalimide.

The chemistry of transition metal carbene complexes,

L MC(X)R (i.e., terminal carbenes) has been categorized into

n

two types, named after their discoverers as Fischer carbenes

and Schrock carbenes. As outlined in a recent theoretical

study,15 these are conventionally distinguished by a low metal

oxidation state and X a p donor (OR@, NR@ , etc.) for Fischer

2

carbenes, and a high metal oxidation state and X a pure sigma

ligand (H, alkyl, silyl, etc.) for Schrock carbenes. In our case, is

a

Ru(II) complex of a carbene with a p-donor group

RuHCl(C(OR)R@)L and no CO ligands a Fischer- or a

2

Schrock-type carbene? These mentioned ““distinguishing

featuresÏÏ fail to recognize two other di†erences. (1) Fischer

carbene complexes generally have the strong p acid CO for

some or all of the co-ligands L (which will tend to minimize

M ] CXR back-bonding and thus put higher demands on

X ] C p bonding) while Schrock carbenes have strong sigma

donors (alkyls and phosphines) and sometimes p donors

(alkoxides) for L. (2) Fischer carbene complexes invariably

have an 18-electron count at M while Schrock carbene com-

plexes generally have 16 or fewer valence electrons. In short, it

is unreasonable that the overall di†erences are based primarily

on the MC(X)R substructure; the identity of L and the value

Discussion

The multistep reaction path that is described here is analo-

gous to that of the isomerization of terminal alkyne into vinyl-

idene in the presence of Ru.12 However, while the path is

exothermic from the acetylene adduct to the vinylidene

complex [eqn. (23)], it is endothermic in the case of ethylene

[eqn. (24)]. At the heart of this is the di†erence in energy

of n in L MC(X)R are important, and perhaps controlling

n

factors.

Above and beyond this analysis of di†erences, a distinction

between Fischer and Schrock carbenes is that the former react

with the carbene carbon behaving like an electrophile, while

Schrock carbenes react with the carbene carbon behaving like

a nucleophile. It is thus paradoxical that the low oxidation

state metal promotes electrophilic carbene character, since an

electron-rich metal should maximize back donation. Likewise,

a high metal oxidation state should not cause a nucleophilic

carbene carbon. Moreover, it is also irrational that a p-donor

substituent on the carbene carbon should leave that carbene

electrophilic.

between the isomeric species [*E(C H [ C2CH ) \ 40 kcal

2

mol~1]13 and [*E(C H [ C(H)CH ) \ 79.1 kcal mol~1].

2

4

3

This large di†erence, which is due to the fact that the third

bond of a triple bond is much weaker than the p bond of a

double bond, controls the thermochemistry of the reaction

even in the presence of the metal. The presence of a p-donor

In addition, exceptions exist to the above systematics.

Cp Ta(CH )(CH ) does not show Wittig reactivity under mild

group like OCH lowers the endothermicity of the isomer-

3

2 3 2

conditions. W(CPh )(CO) does not e†ect oleÐn metathesis

ization of free oleÐn to 50 kcal mol~1, thus approaching that

2

5

of free alkyne. Lowering the p-donating ability of the substit-

uent on the carbene disfavors the isomerization

(OMe [ amide [ phthalimide).

until one CO is displaced, from which we can conclude that

oleÐn metathesis requires prior WÈoleÐn bonding and does

not proceed from direct contact between the carbene carbon

and an oleÐn. Indeed, it is not at all established that oleÐn

metathesis beneÐts from nucleophilic vs. electrophilic carbene

carbon character. These characteristics may in fact be quite

irrelevant.

The reaction path found here for ethylene (and most likely

representative of that of vinyl ether) shows the key role of the

metal hydride in permiting the isomerization to occur. In the

absence of the metal fragment a 1,2-shift of H in free ethylene

New J. Chem., 2000, 24, 9È26

19

View Article Online

Reactivity is not necessarily a reÑection of the character of

an unperturbed molecule. In particular, the Wittig-like reacti-

vity of certain Schrock carbenes [eqn. (25), which is a prime

source for the claim of nucleophilic carbon character in

Schrock carbenes] probably originates from an adduct K in

which the acetone carbon is made more electrophilic by Ta

and such substrate binding also makes C@ more nucleophilic.

residual e. Schrock complexes are characterized mostly

by large residual and small d, b and r. These values have

been calculated (Table 5) for RuHCl(PH ) (CH(CH )),

3 2

3

RuHCl(PH ) (C(OCH )(CH )) in the three minima (7, 8 and

3 2

3

9) and for RuCl (PH ) (CH(CH )) as a reference system.

2

3 2

3

The parameter values show that the OCH substituted car-

benes are ideal Fischer carbenes, especially in the two most

3

stable conformations (7 and 8); conformation 9 has a slightly

R TaCHR ] Me CO ] ““R TaOÏÏ ] RHC2CMe (25)

higher residual but is still clearly

a Fischer carbene.

3

2

3

2

RuCl (PH ) [CH(CH )] is a typical Schrock complex with a

The unsaturation at M is probably a key factor in the reacti-

vity dichotomy between Fischer and Schrock carbenes. In

support of this assertion, a theoretical study15 has revealed

how addition of one Ñuoride to the Schrock carbene model

F WCH to give F WCH ~, alters the WÈCH bond to

2

3 2

3

large residual (0.325) and very small d, b and r values. Chang-

ing Cl into H on the metal gives a species that has reasonable

d, b and r values but a non-negligible residual. It is thus

remarkable that the same metal fragment with the same

formal oxidation state can result in carbene complexes with a

continuum of behavior between Fischer and Schrock types.

This is probably associated with a metal fragment having a

singlet-triplet gap highly sensitive to the nature of the substit-

uent. This is apparently a very remarkable feature of the 14-

4

2

5

2

something that resembles the same bond in (OC) WCH .

5

2

Indeed, Roper and colleagues long ago noted that oxidation

state is not a safe criterion for predicting electrophilic or

nucleophilic reactivity.16 Two related CpRe(CO) (CRR@)

2

species are susceptible to both electrophilic and nucleophilic

electron RuXYL fragments.

addition to the carbene carbon; when R is OEt, electrophilic

addition (i.e., H`) no longer occurs.17 Thus, metal oxidation

state is not a controlling factor, and unsaturation at the metal

is a key (but not sufficient) factor. In this context, the ruthe-

nium chemistry reported here illustrates a class of compounds

that Ðt neither traditional carbene complex category.

2

The isomerization reaction type observed here seems quite

general for vinyl ethers; it demonstrates that the hydrido

carbene is more stable thermodynamically than either the

hydrido oleÐn or the alkyl isomer [eqn. (26)] and it shows

that there is no tendency for the hetero substituent on the

carbene to diminish the unsaturation at Ru by direct O ] Ru

RuHCl[C(OR)R@]L carries a p-donor substituent on the

2

binding. Isotope labeling using CH 2CD(OEt) and DFT cal-

carbene carbon, the metal is in an intermediate oxidation state

2

culations both prove that the regiochemistry of addition of

[but Ru(II) is a fairly powerful p base], but the metal is

unsaturated.

RuÈH across the H C2CH(OR) bond is not selective, but that

2

only the direction shown in eqn. (26) leads to the thermody-

namically preferred carbene. The alternative intermediate

[eqn. (27)] leads to a carbene devoid of heteroatom stabiliza-

tion, which is apparently thermodynamically less stable.

Several theoretical studies using GVB, NBO and CDA

analyses have been carried out on representative selections of

carbene complexes to classify the carbene complexes as a

member of either Fischer or Schrock series.15 With these

tools, Fischer carbenes were shown to be donor-acceptor

complexes involving metal and carbene fragments in a singlet

state, while the Schrock carbenes should be discussed in terms

of interactions between metal and carbene fragments in the

triplet states. If in fact the energy gap between singlet and

triplet of each fragment is a controlling criterion, there is no

reason to partition into two classes, as a continuum situation

is highly probable. This is probably the right time to recognize

that there will be a continuum of carbene ““charactersÏÏ, and to

cease trying to place new ones in either the Fischer or the

Schrock category.17 The systems presented here o†er an ideal

study ground for a more in-depth understanding of what con-

trols the changes from Fischer to Schrock carbenes. The pres-

ence of unsaturation and the nature of the ligand trans to the

empty site are probably key factors that have not been noticed

earlier.

Why has this facile isomerization route to carbene ligands

not already been discovered? First, the organometallic chem-

istry of vinyl ethers has not been extensively investigated in

modern times,18,19 and what has been done centers on elec-

trophilic attack on the ether oxygen (i.e., RO~ abstraction, to

give vinyl complexes) of less electron-rich, and saturated mol-

ecules. More important, previous reports involved nonhydride

compounds, which are thus unable to e†ect the mechanism

established here. Finally, any previous study under hydrogen

gas, even if it involved carbene intermediates, would have

given an alkane product since the unsaturated carbenes of the

sort produced here are readily hydrogenated to alkanes [eqn.

A CDA analysis15 was carried out on several representative

16-electron carbene complexes resulting from union of the

fragments RuXY(PH ) and CH(CH ) or C(OCH )(CH ). As

3 2

3

shown by this analysis, a Fischer complex is characterized by

a large carbene ] metal donation (large positive d), a large

metal ] carbene back donation (large positive b),

a

large repulsive polarization (large negative r) and a small

Table 5 CDA analysis from DFT wavefunctions

d

b

r

e

(H P) RuHCl[CH(CH )]

0.335

0.470

0.487

0.003

0.273

0.264

0.314

0.058

[0.287

[0.323

[0.425

0.008

0.117

0.058

0.000

0.325

3

2

3

(H P) RuHCl[C(OMe)(CH )], 9

3

2

3

(H P) RuHCl[C(OMe)(CH )], 7 or 8

3

2

3

(H P) RuCl [CH(CH )]

3

2

3

20

New J. Chem., 2000, 24, 9È26

View Article Online

(28); 1 atm H , C D , 60 min at 25 ¡C]. To answer the ques-

O and N were represented by a 6-31G(d,p) basis set.26 In the

case of the oleÐn substituted by an amide group (10), a

2

6 6

tion that begins this paragraph, a referee has commented that

““It has, in a way . . . ÏÏ In a previous report,20 the thermody-

namic preference for ethylidene in the isomerization of ethyl-

ene on a highly reducing (Me SiNC H ) NTa fragment, was

STO-3G basis set was used for the CH group of the Ðve-

2

membered ring as well as the H of PH . Comparison between

3

the results with the smaller basis set and the larger one (as

3

2 4 3

attributes to an a-agostic interaction.

ClHL Ru2C(Me)(OEt) ] 2 H ] RuH ClL ] Et O (28)

deÐned above) for 11 proved the more restricted basis set to

give good geometrical results. Full geometry optimization was

performed without symmetry restriction. For the reaction

path of isomerization of the C H adduct into the C(H)CH

2

3

2

The implication of the above is that any unsaturated mono-

hydride has the potential to e†ect this carbene synthesis from

vinyl ethers. To be able to do this, the chosen metal must be

sufficiently electron-rich to tolerate the higher formal oxida-

tion state of the carbene product. In practice, however, we

have found that OsHCl(PPh ) can be stirred in C H with

2

4

3

complex, the nature of the optimized structure as a minimum

or a transition state was checked by numerical frequency cal-

culations. The transition-state structures were given small geo-

metrical perturbations along the reaction coordinates and

then further geometrical optimization was carried out to

ensure they connect the reactant and product of interest.

3 3

6 6

equimolar H C2CH(OR) (R \ Et or But) at 25 ¡C for up to 90

2

h without change. With RuHCl(PPh ) there is no reaction

with ethyl vinyl ether over 3 days at 60 ¡C in C D . We con-

tinue to search for other unsaturated monohydrides capable

of this isomerization, with special attention to whether a 14-

electron conÐguration and/or a four-coordinate structure is a

necessity.

3 3

Syntheses and reactions

6

All manipulations were performed using standard Schlenk

techniques or in an argon-Ðlled glovebox unless otherwise

noted. Solvents were distilled from Na/benzophenone or

CaH , degassed prior to use, and stored in air-tight vessels.

2

There is a general belief that Fischer carbenes are ““more

stableÏÏ than Schrock carbenes, and this is attributed to p don-

ation by the heteroatom to the carbene carbon. Quantitative

comparison of ““stabilityÏÏ is however not established in such

commentaries since there are no isomeric forms for experi-

mental comparison. Instead, the discussion usually hinges on

Fischer carbenes having an electrophlic carbon while Schrock

carbenes have nucleophilic carbon; these have no direct rela-

tion to ““stabilityÏÏ. What the calculations reveal here on the

systems studied experimentally is that, for isomeric alternative

carbenes on Ru, the heteroatom on the carbene carbon is

indeed more stable. V ia the thermodynamic cycles in Scheme

2, this can be traced primarily to the properties of the free

carbenes [*E(a ] b) vs. *E(b ] a) to make the two di†erent

carbenes]. The heteroatom makes the carbene more stable

(more energetically accessible). Since this is close to the calcu-

lated di†erence in overall *E(1) and *E(2), it follows that the

two BDEs do not di†er greatly. That is, di†erences in the

bonding of the two isomeric carbenes to Ru are less important

than the di†erences in the energies of the free carbenes them-

selves. Thus, no comparative conclusions can be drawn, from

the observed isomerization, about the Ru2C bond. The forma-

tion of the heteroatom carbene is possible due to properties of

the metal-free hydrocarbon isomers.

Commercially available vinyl ethers, amines and amides were

used as received after drying and degassing. 1H NMR chemi-

cal shifts are reported in ppm relative to protio impurities in

the deutero solvents. 31P and 19F NMR spectra are referenced

to external standards of 85% H PO and CFCl , respectively

3

4

3

(both at 0 ppm). NMR spectra were recorded with either

Varian GEMINI 2000 (300 MHz 1H; 121 MHz 31P; 75 MHz

13C; 282 MHz 19F) or Varian UNITY INOVA (400 MHz 1H;

162 MHz 31P; 101 MHz 13C; 376 MHz 19F) instruments. IR

spectra were recorded on a Nicolet 510P FT-IR spectrometer

equipped with OMNIC v.4.1b software.

Preparation of RuHCl(PPri ) . Under Ar, 750 mg (1.64

3 2

mmol) of RuH Cl (PPri ) 27 and 230 mg (1.64 mmol) of

2

3 2

lithium 2,2,6,6-tetramethylpiperidide were added to a Schlenk

Ñask equipped with a stir bar. Approximately 25 mL of

pentane was added and the reaction allowed to stir overnight.

The solution was Ðltered thought a medium porosity frit and

the solvent was removed to a liquid N trap. The deep red

2

product was dried in vacuo overnight to yield 510 mg of

RuHCl(PPri ) (73%). The compound can be heated mildly

3 2

(55 ¡C) to facilitate removal of the free amine generated and

can also be washed with small portions of hexa-

methyldisiloxane if necessary. 1H NMR (400 MHz, C D ,

6

20 ¡C): d [ 24.2 (t, 2J \ 32.8 Hz, RuH), 1.34 [dvt, J

\

PvH

Experimental

Computational details

3J \ 6.2 Hz, 18H, P(CHMe ) ], 1.36 [dvt, J \ 3J

\

HvH

2 3

PvH

HvH

6.2 Hz, 18H, P(CHMe ) ], 2.19 [m, 6H, P(CHMe ) ].

2 3

31PM1HN NMR (162 MHz, C D , 20 ¡C): d 84.1 (s). 13CM1HN

6

Ab initio calculations were carried out with the Gaussian 9421

set of programs within the framework of DFT at the B3PW91

level.22 The HayÈWadt e†ective core potential (quasi-rela-

tivistic for the metal centers) was used to replace the 28 inner-

most electrons of Ru23 and the 10 core electrons of P and

Cl.24 The associated double f basis sets were used. They were

augmented by d polarization functions for P and Cl.25 H, C,

NMR (75.5 MHz, C D , 20 ¡C): d 20.8 [s, P(CHMe ) ], 21.2

6

2 3

[s, P(CHMe ) ], 28.4 [vt, J \ 6.4 Hz, P(CHMe ) ].

2 3 PvC 2 3

RuHCl(PPri ) (N ). Under Ar, 15 mg (0.033 mmol)

3 2

2

RuHCl(PPri ) in 0.5 mL benzene-d was added to an NMR

3 2

6

tube equipped with a TeÑon stopcock. The sample was

degassed, the benzene frozen in ice, and the tube Ðlled to

Scheme 2

New J. Chem., 2000, 24, 9È26

21

View Article Online

approximately 1 atm with N . Agitation of the tube resulted

in complete conversion to the dinitrogen adduct within 5 min.

RuHClL with 1-hexene or styrene. Under argon, 10.0 mg

2

(0.022 mmol) RuHClL was dissolved in 0.5 mL C D in an

2

6 6

1H NMR (300 MHz, C D , 20 ¡C): d [ 28.1 (t, 2J \ 18.3

NMR tube and 2.8 lL (0.022 mmol) 1-hexene or 2.5 lL (0.022

mmol) styrene added. In each case, after 30 min, an oleÐn

adduct was observed in approximately 10% population rela-

6

PvH

\ 3J \ 6.6 Hz, 18H,

HvH

Hz, RuH), 1.22 [dvt,

J

PvH

P(CHMe ) ]),

d

1.24 [dvt,

J

\ 3J \ 6.6 Hz, 18H,

2 3

PvH

HvH

P(CHMe ) ], 2.56 [br s, 6H, P(CHMe ) ]. 31PM1HN NMR

(121 MHz, C D , 20 ¡C): d 55.6 (s).

tive to unreacted RuHClL , though longer reaction times lead

2 3

2

to an unidentiÐed mixture of products. The oleÐnic protons of

6

the adduct were not resolved due to coincidental overlap with

the PPri ligands. RuHClL (CH 2CHC H ). 1H NMR (400

RuHCl(PPri ) (C H N). Under Ar, 10 mg (0.022 mmol)

3 2

RuHCl(PPri ) was dissolved in 0.5 mL C D , 1.8 lL (0.022

3

2

4 9

MHz, benzene-d ): d [ 23.7 (m, 1H, RuH). 31PM1HN NMR

5

6

(162 MHz, benzene-d ): d 34.9, 39.5 (AB pattern, 2J \ 287

3 2

6 6

mmol) pyridine is added and the tube shaken. Conversion to

the pyridine adduct was complete in the time of mixing as

evidenced by a color change from dark red to bright red-

orange. 1H NMR (400 MHz, C D , 20 ¡C): d [ 20.9 (t,

6

PvP

Hz). RuHClL (CH 2CHPh). 1H NMR (400 MHz, benzene-

2

d ): d [ 22.1 (apparent t, 2J \ 34 Hz, 1H, RuH). 31PM1HN

6

HvP

6

NMR (162 MHz, benzene-d ): d 85.3, 86.4 (AB pattern,

2J \ 34 Hz).

6

2J \ 24.4 Hz, 1H, RuH), 1.38 [dvt, J \ 3J \ 6.4 Hz,

PvP

PvH

HvH

36H, P(CHMe ) , both diastereotopic methyl groups are seen

as a single signal from coincidental overlap], 1.71 [m, 6H,

RuHCl(PPri ) 2C(Me)OEt. Under Ar, 25 mg (0.055 mmol)

2 3

3 2

of RuHCl(PPri ) was placed in an NMR tube in C D . V ia

3 2

6 6

P(CHMe ) ], 6.02 (apparent t, 3J \ 6.0 Hz, 1H, C H N),

syringe, 5.2 lL (0.055 mmol) of ethyl vinyl ether was added

and the NMR tube sealed. 1H, 13CM1HN, and 31PM1HN NMR

spectra taken after approximately 30 min revealed quantitat-

2 3

HvH

5 5

6.26 (apparent t, 3J \ 6.0 Hz, 1H, C H N), 6.56 (apparent

HvH

t, 3J \ 7.4 Hz, 1H, C H N), 8.94 (d, 3J \ 5.6 Hz, 1H,

HvH HvH

C H N), 10.74 (d, 3J \ 5.6 Hz, 1H, C H N). 31PM1HN

HvH

5 5

5

ive conversion to RuHCl(PPri ) (2C(Me)OEt). The complex

5

5 5

3 2

NMR (162 MHz, C D , 20 ¡C): d 37.9 (s). 13CM1HN NMR (101

can be isolated as an orange-brown viscous oil from benzene

6

MHz, C D , 20 ¡C):

d

20.3 [s, P(CHMe ) ], 20.8 [s,

if a larger quantity is required. 1H NMR (300 MHz, C D ,

6

2 3

6

P(CHMe ) ], 25.4 [vt, J \ 6.0 Hz, P(CHMe ) ], 120.7 (s,

20 ¡C): d [ 21.65 (t, 2J \ 22.8 Hz, 1H, RuH), 1.13 [dvt,

2 3

PvC

5

2 3

PvH

C H N), 121.9 (s, C H N), 132.2 (s, C H N), 160.5 (s,

J

\ 3J \ 6.3 Hz, 18H0, P(CHMe ) ], 1.25 [dvt, J

\

5

5 5

PvH

HvH

2 3

PvH

C H N), 163.1 (s, C H N).

3J \ 6.3 Hz, 18H, P(CHMe ) ], 1.17 [t, 3J \ 7.2 Hz,

5

5 5

HvH 2 3 HvH

3H, Ru2C(Me)OCH CH ], 2.33È2.44 [m, 6H, P(CHMe ) ],

2

3

2 3

2.69 [s, 3H, Ru2C(Me)OEt], 4.37 [q, 3J \ 7.5 Hz, 2H,

RuHCl(PPri ) with 2 C H N. Under Ar, 10 mg (0.022

3 2

HvH

5

Ru2C(Me)OCH CH ]. 31PM1HN NMR (121 MHz, C D ,

mmol) RuHCl(PPri ) was dissolved in 0.5 mL C D , 3.6 lL

2

3

6 6

3 2

6 6

20 ¡C): d 58.2 (s). 13CM1HN NMR (75.5 MHz, C D , 20 ¡C): d

(0.044 mmol) pyridine added and the tube shaken. After

6

14.6 [s, Ru2C(Me)OCH CH ], 19.7 [s, P(CHMe ) ], 20.4 [s,

2 3

P(CHMe ) ], 26.2 [vt, J \ 9.1 Hz, P(CHMe ) ], 40.8 [s,

2 3 PvC 2 3

Ru2C(Me)OEt], 68.5 [s, Ru2C(Me)OCH CH ], 289.8 [t,

10 min 1H and 31PM1HN NMR revealed the generation

2

3

of

a

mixture

of

RuHCl(PPri ) (C H N)

(above),

3 2

RuHCl(PPri ) (C H N) , and RuHCl(PPri )(C H N) , as well

3 2

as the presence of free phosphine. RuHCl(PPri ) (C H N) :

3 2

1H NMR (400 MHz, C D , 20 ¡C): d [ 12.9 (t, 2J \ 14 Hz,

PvH

RuH). 31PM1HN NMR (162 MHz, C D , 20 ¡C): d 56.1 or 71.0

5 5

2

3

5

2

3

5

2

5

2J \ 9.7 Hz, Ru2C(Me)OEt].

PvC

5

2

Upon cooling a sample of RuHCl(PPri ) (2C(Me)OEt) in

3 2

toluene-d to [90 ¡C, slowed rotation of the ruthenium

8

6

carbene bond allowed detection of the two isomers, which

(s). RuHCl(PPri )(C H N) : 1H NMR (400 MHz, C D ,

3

5

PvH

2

6 6

di†er in E/Z stereochemistry about the (X)(Y)Ru2CRR@ bond.

20 ¡C): d [ 20.0 (d, 2J \ 30 Hz, RuH). 31PM1HN NMR (162

1H NMR (400 MHz, toluene-d , [80 ¡C): New signals were

MHz, C D , 20 ¡C): d 71.0 or 56.1 (s).

8

6

seen at d 4.95 and 4.29 [1 : 10 ratio, coalesced to the time-

averaged signal at d 4.38, Ru2C(Me)OCH CH ], d 2.06 and

2

3

RuHCl(PPri ) (CH 2CH ). Under Ar, 10 mg (0.022 mmol)

2.87 (1 : 10 ratio, coalesce at d 2.68, Ru2C(Me)OCH CH ],

3 2

2

3

RuHCl(PPri ) was added to an NMR tube equipped with a

and d [ 25.38 and [21.29 (1 : 10 ratio, coalesce at d [ 21.68,

3 2

TeÑon stopcock. The tube was Ðlled with C D to a predeter-

RuH). 31PM1HN NMR (162 MHz, toluene-d , [80 ¡C): d 51.8

6

8

mined mark on the tube so that the remaining head space

volume was 4.0 mL (approximately 0.5 mL C D ). The NMR

tube was cooled to 0 ¡C to freeze the benzene-d and was then

and 56.4 (1 : 10 ratio, coalesce at d 56.0).

6

Detection of RuHCl(PPri ) (CH CHOEt). Low tem-

3 2

2

6

perature adduct. Under Ar, RuHCl(PPri ) (10 mg, 0.022

evacuated. It was then Ðlled with ethylene (0.022 mmol) to 95

3 2

mmol) was dissolved in toluene-d (ca. 0.5 mL) in an NMR

8

mm Hg and the stopcock closed. The sample was then

warmed to room temperature, shaken, and its 1H and

31PM1HN NMR spectra taken over 30 min intervals. The

adduct that formed showed little or no decomposition over a

period of several hours. 1H NMR (400 MHz, C D , 20 ¡C): d

tube equipped with a TeÑon stopcock. Ethyl vinyl ether (2.0

lL, 0.022 mmol) was then added to the NMR tube such that

it did not mix with the toluene-d solution. The sample was

8

then cooled in a dry iceÈisopropanol bath, shaken to thor-

6

oughly mix the reagents and placed immediately in a pre-

cooled ([85 ¡C) NMR spectrometer probe. The probe

temperature was subsequently raised in 10 ¡C increments

(allowing 10 min to stabilize at each interval) and the 1H

and 31PM1HN spectra were recorded. Selected NMR spectro-

scopic data for RuHCl(PPri ) (CH 2CHOEt) follows. The

[ 22.0 (t, 2J \ 18.0 Hz, RuH), 1.15 [dvt, J \ 3J

PvH PvH

6.0 Hz, 18H, P(CHMe ) ], 1.20 [dvt, J \ 3J \ 6.0 Hz,

2 3 PvH HvH

18H, P(CHMe ) ], 2.25 [m, 6H, P(CHMe ) ], 2.79 [t, 4J

2 3 2 3 PvH

3.2 Hz, 4H, Ru(CH 2CH )]. 31PM1HN NMR (162 MHz, C D ,

\

HvH

\

2

6 6

20 ¡C): d 44.1 (s).

3 2

2

oleÐnic protons of the adduct were not resolved due to

Reaction of RuHCl(PPri ) with CD 2CD . Reversible

coincidental overlap with the PPri ligands. 1H NMR (300

3 2

2

3

insertion. Under Ar, 10 mg (0.022 mmol) RuHCl(PPri ) was

MHz, toluene-d ): d [15.52 (t, 2J \ 17.7 Hz, 1H, RuH),

3 2

8

PvH

added to an NMR tube equipped with a TeÑon stopcock in

3.69 [m, 1H, Ru(CH 2CHOCH CH )], 4.35 [m, 1H, Ru

(CH 2CHOCH CH )], 2.02 [m, 3H, P(CHMe ) ], 2.32 [m,

3H, P(CHMe ) ]. 31PM1HN NMR (121 MHz, toluene-d ): d

40.8, 46.0 (AB pattern, 2J_PAhPB\ 300 Hz).

Hydrogenation of RuHClL (2C(OEt)Me). Under argon,

10.0 mg (0.022 mmol) RuHClL was dissolved in 0.5 mL

C D in an NMR tube equipped with a TeÑon stopcock and

2

3

0.5 mL of benzene. The tube was frozen in ice, evacuated, and

2

2 3

3

2 3

CD 2CD (600 torr) was added. 2H NMR (20 ¡C) spectra

2

8

taken after 1 h at room temperature show deuterium incorp-

oration into the PPri methyl groups (d 1.2), and into the

3

hydride position (d [ 22.0) in addition to being present in the

2

oleÐnic adduct (d 2.8). This is indicative of reversible insertion

of the ethylene unit into the RuÈH bond.

2

6

22

New J. Chem., 2000, 24, 9È26

View Article Online

2.4 lL (0.022 mmol) ethyl vinyl ether added. After formation

of the carbene, as veriÐed by 31P NMR, the solution was

frozen in ice, the headspace gases removed, and the tube Ðlled

2H, OCH CH CH CH ), 1.17 [dvt, J \ 3J \ 6.6 Hz,

2

3

PvH

HvH

18H, P(CHMe ) ], 1.30 [dvt, J \ 3J \ 6.6 Hz, 18H,

2 3

P(CHMe ) ], 1.49 (apparent quintet, 3J \ 7.8 Hz, 2H,

2 3 HvH

OCH CH CH CH ), 2.40È2.50 [m, 6H, P(CHMe ) ], 2.76

PvH

HvH

to 1 atm with H . After 30 min at room temperature, over

2

3

2 3

50% conversion of RuHClL (2C(OEt)Me) to RuH ClL 28

[s, 3H, Ru2C(Me)OR], 3.27 (t, 3J \ 6.9 Hz,

2

3

2

HvH

and diethyl ether was achieved.

2H, OCH CH CH CH ), 3.56 (t, 3J \ 4.0 Hz,

2

3

HvH

2H, OCH CH OBun), 4.56 (t, 3J \ 4.0 Hz, 2H,

HvH

RuHCl(PPri ) (Cw OCH CH Cz H ). Under Ar, 25 mg (0.055

3 2

OCH CH OBun). 31PM1HN NMR (121 MHz, C D , 20 ¡C):

2

6 6

mmol) RuHCl(PPri ) was added to an NMR tube in C D .

d 57.8 (s). 13CM1HN NMR (75.5 MHz, C D , 20 ¡C): d 14.3

3 2

6

6 6

V ia syringe, 4.2 lL (0.055 mmol) of 2,3-dihydrofuran was

(s, OCH CH CH CH ), 19.9 (s, OCH CH CH CH ), 20.0

2

3

2

3

added and the tube sealed. After 30 min NMR spectra were

recorded. The benzene-d was then removed to a [196 ¡C

[s, P(CHMe ) ], 20.7 [s, P(CHMe ) ], 26.5 [vt, J \ 9.5

2 3 2 3 PvC

Hz, P(CHMe ) ], 32.4 (s, OCH CH CH CH ), 40.8

2 3

[s, Ru2C(Me)OR], 69.5 (s, OCH CH CH CH ), 71.4 (s,

6

2

3

trap, the product was re-dissolved in CD Cl , and the 1H

2

3

spectra measured again to resolve all peaks. In C D , the

OCH CH OBun), 72.7 (s, OCH CH OBun), 288.7 (t, 2J

\

6

2

PvC

central methylene unit of the carbene substituent was not

resolved. 1H, 13CM1HN, and 31PM1HN NMR showed quantitat-

ive conversion to RuHCl(PPri ) (2Cw OCH CH Cz H ). 1H

9.5 Hz, Ru2C).

RuHCl(PPri ) (2C(Me)OCH CH OH). Under Ar, 25 mg

3 2

2

3 2

2

NMR (300 MHz, CD Cl , 20 ¡C): d [ 18.20 (t, 2J \ 21.9

(0.055 mmol) of RuHCl(PPri ) was placed in an NMR tube in

2

PvH

\ 3J \ 6.3 Hz, 18H,

HvH

3 2

Hz, 1H, RuH), 1.19 [dvt,

J

C D . V ia syringe, 4.9 lL (0.055 mmol) of ethylene glycol

PvH

6 6

P(CHMe ) ], 1.21 [dvt,

J

\ 3J \ 6.3 Hz, 18H,

vinyl ether was added and the tube sealed. 1H, 13CM1HN, and

31PM1HN NMR spectra taken after 6 h revealed conversion to

RuHCl(PPri ) (C(Me)OCH CH OH). 1H NMR (400 MHz,

2 3

PvH

HvH

P(CHMe ) ], 1.76 (apparent quintet, 3J \ 7.3 Hz, 2H,

2 3

2

HvH

Ru2COCH CH CH ), 2.27È2.34 [m, 6H, P(CHMe ) ], 3.07 (t,

2 3

3J \ 7.7 Hz, 2H, Ru2COCH CH CH ), 4.19 (t, 3J \ 6.9

HvH HvH

Hz, 2H, Ru2COCH CH CH ). 31PM1HN NMR (121 MHz,

2

3 2

2

C D , 20 ¡C): d [21.11 (t, 2J \ 21.6 Hz, 1H, RuH), 1.13

2

6

PvH

[dvt, J \ 3J \ 6.6 Hz, 18H, P(CHMe ) ], 1.26 [dvt,

PvH HvH 2 3

2

C D , 20 ¡C): d 60.1 (s). 13CM1HN NMR (75.5 MHz, C D ,

J

\ 3J \ 6.6 Hz, 18H, P(CHMe ) ], 2.36È2.46 [m, 6H,

6

PvH

HvH

2 3

20 ¡C): d 20.5 [s, P(CHMe ) ], 20.8 [s, P(CHMe ) ], 24.0 (s,

2 3 2 3

Ru2COCH CH CH ), 25.5 [vt, J \ 9.4 Hz, P(CHMe ) ],

PvC 2 3

51.4 (s, Ru2COCH CH CH ), 76.0 (s, Ru2COCH CH CH ),

P(CHMe ) ], 2.72 [s, 3H, Ru2C(Me)OR], 3.53 (s, 1H, OH)

when 10.0 mg RuHClL and equimolar oleÐn are used in the

2

same solvent volume, OH has d 3.36); 3.68 (t, 3J \ 4.8 Hz,

2

HvH

286.6 (t, 2J \ 9.4 Hz, Ru2COCH CH CH ).

PvC

2H, OCH CH OH), 4.36 (t, 3J \ 4.8 Hz, 2H,

2

HvH

OCH CH OH). 31PM1HN NMR (162 MHz, C D , 20 ¡C): d

2

6 6

RuHCl(PPri ) (2C(Me)OC H ). Under Ar, 10 mg (0.022

56.4 (s). 13CM1HN NMR (101 MHz, C D , 20 ¡C): d 19.7 [s,

3 2

6

11

6 6

mmol) of RuHCl(PPri ) was placed in an NMR tube in

P(CHMe ) ], 20.4 [s, P(CHMe ) ], 26.3 [vt, J \ 10.0 Hz,

2 3 2 3 PvC

P(CHMe ) ], 40.8 [s, Ru2C(Me)OR], 61.1 (s, OCH CH OH),

2 3

74.3 (s, OCH CH OH), 288.8 (t, 2J \ 8.4 Hz, Ru2C).

PvC

3 2

C D . V ia syringe, 3.1 lL (0.022 mmol) of cyclohexyl vinyl

6

2

ether was added and the tube sealed. 1H and 31PM1HN NMR

spectra taken after 1 h showed complete conversion to

RuHCl(PPri ) (2C(Me)OC H ). 1H NMR (400 MHz, C D ,

2

RuHCl(PPri ) (2]C(Me)OCH CH OCH CH OH). Under

3 2

6

PvH

11

6

3 2

2

3 2

2

20 ¡C): d [19.39 (t, 2J \ 22.8 Hz, 1H, RuH), 1.21 [dvt,

Ar, 10 mg (0.022 mmol) of RuHCl(PPri ) was placed in an

J

\ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 1.33 [dvt,

NMR tube in C D . V ia syringe, 3.0 lL (0.022 mmol) of

PvH

HvH

2 3

6 6

\ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 1.03È1.75 [m,

diethylene glycol vinyl ether was added and the tube sealed.

1H and 31PM1HN NMR spectra taken after 1 h revealed con-

version to RuHCl(PPri ) (2C(Me)OCH CH OCH CH OH).

HvH 2 3

10H, Ru2C(Me)OC H ], 2.40È2.49 [m, 6H, P(CHMe ) ],

6

11

2 3

2.72 [s, 3H, Ru2C(Me)OC H ], 4.38È4.46 [m, 1H,

11

Ru2C(Me)OC H ]. 31PM1HN NMR (162 MHz, C D , 20 ¡C):

11

6

3 2

2

1H NMR (400 MHz, C D , 20 ¡C): d [21.40 (t, 2J \ 21.2

6

PvH

\ 3J \ 6.8 Hz, 18H,

HvH

d 57.4 (s).

Hz, 1H, RuH), 1.15 [dvt,

J

PvH

P(CHMe ) ], 1.27 [dvt,

P(CHMe ) ], 2.37È2.47 [m, 6H, P(CHMe ) ], 2.71 [s, 3H,

J

\ 3J \ 6.8 Hz, 18H,

2 3

PvH

HvH

RuHCl(PPri ) (2C(Me)OSiMe ). Under Ar, 20 mg (0.044

3 2

3

2 3

mmol) of RuHCl(PPri ) was placed in an NMR tube in

Ru2C(Me)OR], d 3.25 (t, 3J \ 4.4 Hz, 2H, OCH CH OH),

HvH

3 2

2

C D . V ia syringe, 6.7 lL (0.044 mmol) of vinyl-

3.51 (m, 4H, CH OCH ), 4.51 [t, 3J \ 4.4 Hz, 2H,

6

2

HvH

oxytrimethylsilane was added and the tube sealed. 1H,

13CM1HN, and 31PM1HN NMR spectra taken after 2 h revealed

quantitative conversion to RuHCl(PPri ) (2C(Me)OSiMe ).

Ru2C(Me)OCH ], the OH proton is obscured by signals for

2

the protons vicinal to the ether oxygen(s). 31PM1HN NMR (162

MHz, C D , 20 ¡C): d 56.3 (s).

3 2

3

6 6

1H NMR (400 MHz, C D , 20 ¡C): d [ 17.96 (t, 2J \ 22.0

6

PvH

Hz, 1H, RuH), 0.03 [s, 9H, Ru2C(Me)OSiMe ], 1.24 [dvt,

3

J

\ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 1.27 [dvt, J

\

RuHCl(PPr i ) (2C(Me)OCH CH O(Me)C2)RuHCl(PPri ) .

3 2 2 2 3 2

PvH

HvH

2 3

PvH

3J \ 6.4 Hz, 18H, P(CHMe ) ], 2.30È2.40 [m, 6H,

HvH 2 3

P(CHMe ) ], 2.57 [s, 3H, Ru2C(Me)OSiMe ]. 31PM1HN NMR

2 3

Under Ar, 150 mg (0.328 mmol) of RuHCl(PPri ) was charged

3 2

in a Schlenk Ñask and dissolved in 10 mL of benzene. Over a

3

(162 MHz, C D , 20 ¡C): d 58.6 (s). 13CM1HN NMR (101 MHz,

period of 1 h, 20.5 lL (0.164 mmol) of ethylene glycol divinyl

ether in 5 mL of benzene was added through a pressure equal-

ized dropping funnel and the reaction stirred overnight. The

6

C D , 20 ¡C):

d

1.2 [s, Ru2C(Me)OSiMe ], 20.2 [s,

6

3

PvC

P(CHMe ) ], 20.4 [s, P(CHMe ) ], 25.3 [vt, J \ 9.5 Hz,

2 3

P(CHMe ) ], 43.1 [s, Ru2C(Me)OSiMe ], 283.8 [t, 2J \ 8.4

benzene was removed to a N trap and the residue was dis-

3

PvC

2

Hz, RuC(Me)OSiMe ].

solved in pentane. Cooling at [60 ¡C overnight a†orded a

3

brown precipitate that was washed with a small amount of

cold pentane and dried in vacuo. Isolated yield: 65 mg (90%

by 31PM1HN NMR integration before work-up). 1H, 13CM1HN,

and 31PM1HN NMR showed clean conversion to

[RuHCl(PPri ) (2C(Me)OCH È)] . 1H NMR (300 MHz,

RuHCl(PPri ) (2C(Me)OCH CH OBun). Under Ar, 20 mg

3 2

2

(0.044 mmol) of RuHCl(PPri ) was placed in an NMR tube in

3 2

C D . V ia syringe, 7.3 lL (0.044 mmol) of ethylene glycol

6

butyl vinyl ether was added and the tube sealed. 1H, 13CM1HN

and 31PM1HN NMR spectra taken after 24 h revealed quanti-

tative conversion to RuHCl(PPri ) (2C(Me)OCH CH OBun).

3 2

2

C D , 20 ¡C): d [21.21 (t, 2J \ 21.8 Hz, 1H, RuH), 1.17

PvH

[dvt, J \ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 1.30 [dvt,

PvH HvH 2 3

\ 3J \ 6.4 Hz, 18H, P(CHMe ) ], d 2.33È2.44 [m, 6H,

HvH 2 3

P(CHMe ) ], 2.73 [s, 3H, Ru2C(Me)OCH È], 4.85 [s, 2H,

2 3

Ru2C(Me)OCH È]. 31PM1HN NMR (121 MHz, C D , 20 ¡C):

6

3 2

2

1H NMR (300 MHz, C D , 20 ¡C): d [21.29 (t, 2J \ 21.6

J

6

PvH

Hz,

1H,

RuH),

0.86

(t,

3J \ 7.5

Hz,

3H,

HvH

2

OCH CH CH CH ), 1.07 (apparent sextet, 3J \ 7.8 Hz,

2

3

HvH

2

6 6

New J. Chem., 2000, 24, 9È26

23

View Article Online

d 57.9 (s). 13CM1HN NMR (101 MHz, C D , 20 ¡C): d 19.7

J

\ 13.4, 6.3 Hz, 1H, OCH CHOCH ), 4.58 (dd, J

\

6

HvH

2

HvH

[s, P(CHMe ) ], 20.5 [s, P(CHMe ) ], 26.3 [vt, J

\

13.4, 2.1 Hz, 1H, OCH CHOCH ). 31PM1HN NMR (121 MHz,

C D , 20 ¡C): d 56.33, 56.24 (AB pattern, 2J \ 220 Hz).

2 3

PvC

2

9.7 Hz, P(CHMe ) ], 41.3 [s, Ru2C(Me)OCH È],

2 3

2

6

PvP

71.3

[s,

Ru2C(Me)OCH È],

9.1 Hz, Ru2C(Me)OCH È].

288.8

(t,

2J

\

2

PvC

Rw uHCl(PPri ) (2C(Me)N(Me)C(Oz )CH ). Under Ar, 75 mg

2

3 2 3

(0.164 mmol) of RuHCl(PPri ) was charged in a Schlenk Ñask

and dissolved in 10 mL of benzene. V ia syringe, 18.6 lL (0.180

mmol) of N-methyl-N-vinylacetamide was added and the

solution stirred for 4 days. The benzene was removed to a N

trap and the purple solid was washed with pentane.

Drying

3 2

Preparation of 2-Ñuoroethyl vinyl ether: CH 2CH(OCH -

2

CH F). Under Ar, 1.85 g (11.5 mmol) of diethylamino sulfur

2

triÑuoride (DAST)29 was dissolved in 10 mL CH Cl . The

solution was cooled to [78 ¡C and 1.03 mL (11.5 mmol) of

ethylene glycol vinyl ether was added via syringe. The solution

was allowed to warm to room temperature and stirred for 1 h,

2

in

vacuo

yielded

40

mg

(45%)

of

Rw uHCl(PPri ) (2C(Me)N(Me)C(Oz )CH3). 1H NMR (400 MHz,

3 2

then cooled to 0 ¡C and the solvent removed to an N trap.

CD Cl , 20 ¡C): d [ 17.24 (t, 2J \ 26.2 Hz, 1H, RuH), 0.96

2

PvH

The product was then fractionally distilled, collecting the 79È

[dvt, J \ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 1.28 [dvt,

PvH

\ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 2.20 [s, 3H,

HvH 2 3

Ru2C(Me)NR ], 2.22È2.36 [m, 6H, P(CHMe ) ], 2.43 [s, 3H,

HvH

2 3

81 ¡C fraction (760 torr). Yield : approx. 500 mg (49%). 1H

J

PvH

NMR (300 MHz, C D , 20 ¡C):d 3.28 (dt, 3J \ 28.5 Hz,

6

FvH

2

2 3

3J \ 3.9 Hz, 2H, OCH CH F), 3.89 [dd, 3J \ 6.9 Hz,

N(Me)C(O)Me], 3.34 [s, 3H, N(Me)C(O)Me]. 31PM1HN NMR

HvH

2J \ 1.5 Hz, 1H, CH 2CH(OR)], 4.01 [dd, 3J \ 14.1

HvH HvH

Hz, 2J \ 1.5 Hz, 1H, CH 2CH(OR)], 4.06 (dt, 3J \ 47.7

HvH FvH

Hz, 3J \ 3.9 Hz, 2H, OCH CH F), 6.30 [dd, 3J \ 14.1

HvH HvH

Hz, 3J \ 6.9 Hz, 1H, CH 2CH(OR)]. 13CM1HN NMR (75.5

HvH

MHz, C D , 20 ¡C): d 67.0 (d, 2J \ 20.5 Hz, OCH CH F),

FvC

81.5 (d, 1J \ 171 Hz, OCH CH F), 86.1 [s, CH 2CH(OR)],

FvC

151.7 [s, CH 2CH(OR)]. 19F NMR (282 MHz, C D , 20 ¡C):

2

HvH

(162 MHz, CD Cl , 20 ¡C): d 50.4 (s). 13CM1HN NMR (101

2

2 2

MHz, CD Cl , [20 ¡C): d 18.7 [s, P(CHMe ) ], 19.4 [s,

2

2 3

2

2 3

P(CHMe ) ], 22.9 [s, N(Me)C(O)Me], 25.9 [vt, J \ 8.6

2

PvC

Hz, P(CHMe ) ], 34.7 [s, N(Me)C(O)Me], 40.9 [s,

2

2 3

Ru2C(Me)NR ], 174.7 [s, N(Me)C(O)Me], 265.3 (t, 2J

9.7 Hz, Ru2C). m (CH Cl , 25 ¡C) \ 1599 cm~1.

\

6

2

PvC

2

6 6

CO

2 2

2

d [224.8 (tt, 2J \ 47.7 Hz, 3J \ 28.5 Hz).

HvF HvF

RuHCl(PPri ) (2C(Me)Nw C(O)CH CH Cz H ). Under Ar,

3 2 2 2 2

240 mg (0.524 mmol) of RuHCl(PPri ) was charged in a

Schlenk Ñask and dissolved in 35 mL of benzene. V ia syringe,

60.0 lL (0.561 mmol) of 1-vinyl-2-pyrrolidinone was added

and the solution stirred for 2 days. The benzene was re-

moved to a liquid N trap and the purple solid was

washed with pentane. Drying in vacuo yielded 160 mg

3 2

RuHCl(PPri ) (2C(Me)OCH CH F). Under Ar, 10 mg

3 2

2

(0.022 mmol) of RuHCl(PPri ) was placed in an NMR tube in

3 2

C D . V ia syringe, 2.5 lL (0.022 mmol) of 2-Ñuoroethyl vinyl

6

ether was added and the NMR tube sealed. 1H, 19F, and

31PM1HN NMR spectra taken after 3 h revealed quantitative

conversion to RuHCl(PPri ) (2C(Me)OCH CH F). 1H NMR

2

(90% by 31PM1HN integration before workup) of

3 2

2

(300 MHz, C D , 20 ¡C): d [21.32 (t, 2J \ 21.6 Hz, 1H,

RuHCl(PPri ) (2C(Me)Nw C(O)CH Cz H CH ). 1H NMR (400

6

PvH

RuH), 1.12 [dvt, J \ 3J \ 6.3 Hz, 18H, P(CHMe ) ],

PvH HvH 2 3

3 2

2

MHz, CD Cl , 20 ¡C): d [19.56 (t, 2J \ 25.8 Hz, 1H,

2

PvH

RuH), 0.98 [dvt, J \ 3J \ 6.4 Hz, 18H, P(CHMe ) ],

PvH HvH 2 3

1.27 [dvt, J \ 3J \ 6.4 Hz, 18H, P(CHMe ) ], 2.01 [s,

PvH HvH 2 3

3H, Ru2C(Me)NR ], 2.23È2.37 [m, 6H, P(CHMe ) ], 2.32

2 3

(apparent quintet, 3J \ 7.5 Hz, 2H, NC(O)CH CH CH ),

HvH

2.52 [t, 3J \ 8.0 Hz, 2H, NC(O)CH CH CH ], 3.70 [t,

HvH

3J \ 7.0 Hz, 2H, NC(O)CH CH CH ]. 31PM1HN NMR

HvH

(162 MHz, CD Cl , 20 ¡C): d 49.3 (s). 13CM1HN NMR (101

1.25 [dvt, J \ 3J \ 6.3 Hz, 18H, P(CHMe ) ], 2.32È2.44

PvH

HvH

2 3

[m, 6H, P(CHMe ) ], 2.72 [s, 3H, Ru2C(Me)OR], 4.26 (dt,

2 3

2J \ 47.7 Hz, 3J \ 3.9 Hz, 2H, OCH CH F), 4.46 (dt,

FvH

HvH

2

3J \ 29.7 Hz, 3J \ 3.9 Hz, 2H, OCH CH F). 31PM1HN

HvH

2

NMR (121 MHz, C D , 20 ¡C): d 57.8 (s). 19F NMR (282

6

2

MHz, C D , 20 ¡C): d [224.1 (tt, 2J \ 47.7 Hz, 3J

HvF HF

\

6

2

29.7 Hz).

2

MHz, CD Cl , [ 20 ¡C): d 19.0 [s, P(CHMe ) ], 19.6 [s,

2 3

P(CHMe ) ], 22.1 [s, NC(O)CH CH CH ], 25.9 [vt, J

2 3 PvC

8.6 Hz, P(CHMe ) ], 29.7 [s, NC(O)CH CH CH ], 40.4 [s,

2 3

Ru2C(Me)NR ], 45.9 [s, NC(O)CH CH CH ], 180.2 [s,

2

RuHCl(PPri ) (2C(Me)OCH CH NEt ). Under Ar, 10 mg

\

3 2

2

(0.022 mmol) of RuHCl(PPri ) was placed in an NMR tube in

3 2

2

C D . V ia syringe, 4.1 lL (0.022 mmol) of 2-(diethylamino)

6

2

ethanol vinyl ether was added and the tube sealed. 1H and

31PM1HN NMR spectra taken after 90 min revealed quantitat-

ive conversion to RuHCl(PPri ) (2C(Me)OCH CH NEt ). 1H

NC(O)CH CH CH ], 261.5 (t, 2J \ 10.0 Hz, Ru2C).

PvC

2

m

(CH Cl , 25 ¡C) \ 1640 cm~1.

CO

2

3 2

2

NMR (400 MHz, C D , 20 ¡C): d [21.41 (brs, 1H, RuH), 0.96

RuHCl(PPri ) (CH 2CH–NC H O ). Under Ar, 100 mg

3 2 2 8 4 2

6

[t, 3J \ 7.2 Hz, 3H, N(CH CH ) ], 1.16 [dvt, J

HvH 3 2

3J \ 6.4 Hz, 18H, P(CHMe ) ], 1.29 [dvt, J \ 3J

HvH 2 3 PvH

\

(0.218 mmol) of RuHCl(PPri ) and 38 mg (0.218 mmol) of

vinyl phthalimide were mixed and then stirred 1.5 h at room

temperature. The solvent was removed and the product dried

2

PvH

HvH

3 2

6.4 Hz, 18H, P(CHMe ) ], 2.40È2.50 (m, 6H, P(CHMe ) ],

2 3

2.47 [q, 3J \ 7.2 Hz, 2H, N(CH CH ) ], 2.74 [s, 3H,

HvH 3 2

Ru2C(Me)OR], 2.77 (t, 3J \ 6.8 Hz, 2H, OCH CH NEt ),

HvH

4.54 (t, 3J \ 6.8 Hz, 2H, OCH CH NEt ). 31PM1HN NMR

HvH

(162 MHz, C D , 20 ¡C): d 56.4 (s).

in vacuo. Yield: quantitative. 1H NMR (400 MHz, THF-d ,

2

8

0 ¡C): d [20.83 (dd, 2J \ 15.6, 27.6 Hz, 1H, RuH), 1.10

2

PvH

[dvt,

J

\ 3J \ 7.6 Hz, 9H, P(CHMe ) ], 1.25 [m,

2

PvH

HvH

2 3

29H, P(CHMe ) ], 1.64 (brd, 1H,

CH 2CHÈNC H O ), 2.41 (dd, 1H, J \ 14.0, 4.4 Hz,

CH 2CHÈNC H O ), 2.74 [br s, 3H, P(CHMe ) ], 2.85 [brs,

J

\ 3.2 Hz,

6

2 3

HvH

2

8

4

2

HvH

RuHCl(PPri ) (2C(Me)OCH CHOCH ). Under Ar, 10 mg

3 2

2

8

4

2 3

2

2 3

(0.022 mmol) of RuHCl(PPri ) was placed in an NMR tube in

3H, P(CHMe ) ], 4.74 (ddd

È

apparent dt, 1H, J

3 2

HvH

C D . V ia syringe, 2.2 lL (0.022 mmol) of glycidyl vinyl ether

\ 14.6, 6.4 Hz, CH 2CHÈNC H O ), 7.82 (m, 4H,

6

2

8 4 2

(racemic) was added and the NMR tube sealed. 1H and

31PM1HN NMR spectra taken after 1 h revealed quantitative

conversion to RuHCl(PPri ) (2C(Me)OCH CHOCH ). 1H

CH 2CHÈNC H O ). 31PM1HN NMR (162 MHz, THF-d ,

2

8

4

2

8

0 ¡C): d 35.4, 57.9 (AX pattern, J \ 278 Hz). 13CM1HN NMR

PvP

(101 MHz, THF-d , [20 ¡C): d 19.5, 19.8, 20.16, 20.22 [s,

3 2

2

8

NMR (300 MHz, C D , 20 ¡C): d [21.41 (t, 2J \ 22.2 Hz,

P(CHMe ) ], 24.1 [d, J \ 11.1 Hz, P(CHMe ) ], 24.8 [d,

6

PvH

\ 3J \ 6.4 Hz, 18H,

HvH

2 3

PvC

2 3

1H, RuH), 1.15 [dvt,

J

\ 16.1 Hz, P(CHMe ) ], 29.8 (s, CH 2CHÈNC H O ),

PvH

PvC

2 3

2

8 4 2

P(CHMe ) ], 1.26 [dvt,

P(CHMe ) ], 2.22 (dd,

\ 3J \ 6.4 Hz, 18H,

HvH

60.2 (s, CH 2CHÈNC H O ), 124.1, 124.7, 129.1, 130.8, 135.4

2 3

PvH

2

8 4 2

J

\ 5.3, 2.3 Hz, 1H,

(s, CH 2CHÈNC H O aromatics; the peak at 135.4 is over

twice as large as the others and arises from two signals with

coincidental overlap), 167.0, 176.6 (s, CH 2CHÈNC H O

carbonyls).

HvH

2

8 4 2

OCH CHOCH ), 2.30 (apparent t,

J

\ 4.4 Hz, 1H,

2

HvH

OCH CHOCH ), 2.35È2.45 [m, 6H, P(CHMe ) ], 2.72 [s, 3H,

2 3

Ru2C(Me)OR], 3.00 (m, 1H, OCH CHOCH ), 4.34 (dd,

2

8 4 2

2

24

New J. Chem., 2000, 24, 9È26

View Article Online

RuHCl(PPri ) with 9-vinyl carbazole. Under Ar, 10 mg

map phased on the nonhydrogen atoms, and were included as

isotropic contributors in the Ðnal cycles of least-squares

reÐnement. The thermal parameter of hydrogen atom H(10)

was Ðxed in the Ðnal cycles of least-squares to prevent it from

reÐning to a negative value; no other restraints or constraints

were applied. No attempt was made to locate the presumed

3 2

(0.022 mmol) of RuHCl(PPri ) and 4.3 mg (0.022 mmol) of

3 2

9-vinyl carbazole were placed in an NMR tube in C D at

6

25 ¡C. 1H, and 31PM1HN NMR spectra taken after 1 h revealed

approximately 30% conversion to an oleÐn adduct. In addi-

tion, broadened signals for RuHClL and the free oleÐn are

2

observed. In addition, an argument for bonding though the

hydride ligand. The molecule contains one Cl~ and one N

2

oleÐnic portion of the reactant is strengthened by the RuH

signal being more complicated than a triplet. Adduct: 1H

NMR (300 MHz, C D , 20 ¡C): d [19.52 (m, RuH), oleÐnic

ligand, disordered with each other through the center of sym-

metry at the site of the ruthenium atom. Although the

occupancies of these disordered ligands were Ðxed in the Ðnal

reÐnement, prior reÐnements in which those occupancies were

permitted to vary yielded the same occupancies within 1.5

standard uncertainties. However, the structural parameters of

6

protons appear to be buried under signals from the PPri

3

ligands. 31PM1HN NMR (121 MHz, C D , 20 ¡C): d 38.6, 47.3

(AB pattern, 2J \ 290 Hz).

6

PvP

the N ligand are not accurately determined due to this sys-

2

tematic error. A Ðnal di†erence Fourier map was featureless,

RuHCl(PPri ) with 3-methylene-2,3-dihydrofuran. Treat-

3 2

with the largest peak having an intensity of only 0.38 e Ó~3

and residing near the ruthenium atom.

CCDC reference number 440/154. See http://www.rsc.org/

suppdata/nj/a9/a907624G/ for crystallographic Ðles in .cif

format.

ment of 3-furaldehyde with hydrazine in ethylene glycol30

leads to a mixture of 62% 3-methylene-2,3-dihydrofuran and

38% 3-methylfuran.

Addition of 10 equiv. of the conjugated diene to a solution

of 10 mg RuHCl(PPri ) in 0.5 mL of C D results in complete

3 2

6 6

isomerization to 3-methylfuran within 10 min. No reaction

occurs from the 3-methylfuran with RuHCl(PPri ) at room

3 2

temperature over several hours.

Acknowledgements

Preparation of CH 2CD(OEt). The isotopically labeled

2

This work was supported by the U.S. NSF, the Universite de

Montpellier and the French CNRS.

oleÐn was prepared by hydrolysis of CH 2C(Li)OEt31 with an

2

excess of D O in o-xylene at [10 ¡C. Filtration and fractional

2

distillation (30È35 ¡C fraction) of the resulting mixture yielded

99% enriched CH 2C(D)OEt by 1H NMR.

2

References

Preparation of RuDCl(PPri ) . Method 1: RuD Cl (PPri )

3 2

2

3 2

was prepared with 99% enrichment by stirring

1 J. N. Coalter, G. J. Spivak, H. Gerard, E. Clot, E. R. Davidson, O.

Eisenstein and K. G. Caulton, J. Am. Chem. Soc., 1998, 120, 9388.

2 D. Huang, G. J. Spivak and K. G. Caulton, New J. Chem., 1998,

22, 1023.

RuH Cl (PPri ) under an atmosphere of D in CH Cl for

2

3 2

2

2 2

4 h at 25 ¡C. The head space gases were removed and the

Ñask reÐlled with D once during this time period. The

2

3 J. N. Coalter, J. C. Hu†man, W. E. Streib and K. G. Caulton,

manuscript in preparation.

crude RuD Cl (PPri ) was then washed with ether and dried

2

3 2

in vacuo, then dehydrohalogenated.

4 We propose that the 1H chemical shift for R \ Cy, SiMe , and

Method

2

:

RuDCl(PPri ) was prepared by stirring

3

3 2

CH CH CH (cyclic) are slightly downÐeld from that of R \ Et as

RuHCl(PPri ) in a small amount of acetone-d for 12 h at

25 ¡C to allow isotopic exchange through the enol tautomer of

2

a result of the inÑuence on the hydride of changing angle ClÈRu2C

due to electronic and steric factors with the bulkier R groups.

5 Remarkably, 2,3-dihydropyran, the six-membered ring analog,

fails to react after 12 h at 25 ¡C.

3 2

6

the acetone-d . Solution NMR shows [ 90% of the D

6

incorporation now located in the PPri methyl groups. This is

3

6 (a) P. Schwab, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc.,

1996, 118, 100; (b) S. T. Nguyen, L. K. Johnson, R. H. Grubbs and

J. W. Ziller, J. Am. Chem. Soc., 1992, 114, 3974; (c) Z. Wu, S. T.

Nguyen, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc., 1995,

117, 5503; (d) P. Schwab, M. B. France, J. W. Ziller and R. H.

Grubbs, Angew. Chem., Int. Ed. Engl., 1995, 34, 2039.

consistent with agostic stabilization of RuHClL by the PPri

2

3

ligand(s).

X-Ray structure determinations

7 Slower reaction rate with H C2CD(OEt) permits observation of

RuHCl(PPri ) (C H NO). Data were corrected for absorp-

2

3 2

6 9

this AB NMR pattern even at 25 ¡C.

tion and Lorentz and polarization e†ects and equivalent

reÑections were then averaged. The structure was solved using

direct methods (MULTAN78) and Fourier techniques. Two

8 Even if H C2CD(OEt) is reacted with RuHClL (2 : 1 mole ratio)

2

at 25 ¡C to minimize the time spent as the oleÐn adduct, D is

found statistically in RuD, Ru2CC(H,D) (OEt) and all three

3

methylene carbons of the C ring show 50 : 50 disorder, which

vinylic positions of free ethyl vinyl ether; this procedure only

5

was easily modeled. Hydrogen atoms were placed in Ðxed,

serves to decrease the deuteration in the phosphine methyl groups.

9 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G. Watson

and R. Taylor, J. Chem. Soc., Dalton T rans., 1989, S1.

10 F. Ford, T. Yuzawa, M. S. Platz, S. Matzinger and M. Fulscher, J.

Am. Chem. Soc., 1998, 120, 4430.

11 T. J. Johnson, A. Albinati, T. F. Koetzle, O. Eisenstein, J. C.

Hu†man and K. G. Caulton, Inorg. Chem., 1994, 33, 4966.

12 M. Olivan, E. Clot, O. Eisenstein and K. G. Caulton,

Organometallics, 1998, 17, 3091.

13 M. M. Gallo, T. P. Hamilton and H. F. Schaefer, J. Am. Chem.

Soc., 1990, 112, 8714.

14 J. Silvestre and R. Ho†mann, Helv. Chim. Acta, 1985, 68, 1461. Y.

Wakatsuki, N. Koga, H. Werner and K. Morokuma, J. Am. Chem.

Soc., 1997, 119, 360.

15 S. F. Vyboishchikov and G. Frenking, Chem. Eur. J., 1998, 4, 1428.

16 A. F. Hill, W. R. Roper, J. M. Waters and A. H. Wright, J. Am.

Chem. Soc., 1983, 105, 5939.

17 C. P. Casey, C. J. Czerwinski, D. P. Powell and R. K. Hayashi, J.

Am. Chem. Soc., 1997, 119, 5750.

idealized positions for the carbon atoms of the ligands, and a

di†erence Fourier examined to locate the metal hydride. All

hydrogen atoms were reÐned isotropically except those associ-

ated with the disordered carbon atoms. A Ðnal di†erence

Fourier was featureless, with the exception of several peaks of

density 1.3È3.02 e Ó~3 lying at the metal site. These are

undoubtedly due to inaccuracies in the absorption correction.

RuHCl(N )(PPri ) . Data were collected by the moving

2

3 2

crystal-moving detector technique with Ðxed background

counts at each extreme of the scan. Data were corrected for

Lorentz and polarization e†ects, and equivalent data were

averaged. The structure was solved by direct methods

(SHELXTL) and Fourier techniques. All carbon-bound

hydrogen atoms were located in a di†erence electron density

New J. Chem., 2000, 24, 9È26

25

View Article Online

18 (a) A. Cutler, S. Raghu and M. Rosenblum, J. Organomet. Chem.,

1974, 77, 371; (b) T. C. T. Chang, M. Rosenblum and S. B.

Samuels, J. Am. Chem. Soc., 1980, 102, 5931; (c) H. Chen and W.

D. Harman, J. Am. Chem. Soc., 1996, 118, 5672.

24 W. R. Wadt and P. J. Hay, J. Chem. Phys., 1985, 82, 284.

25 A. H. Hollwarth, M. B. Bohme, S. Dapprich, A. W. Ehlers, A.

Gobbi, V. Jonas, K. F. Kohler, R. Stegmann, A. Veldkamp and G.

Frenking, Chem. Phys. L ett., 1993, 208, 237.

19 W. D. Harman, Chem. Rev., 1997, 97, 1953.

26 P. C. Hariharan and J. A. Pople, T heor. Chem. Acta, 1973, 28, 213.

27 C. Grunwald, O. Gevert, J. Wolf, P. Gonzalez-Herrero and H.

Werner, Organometallics, 1996, 15, 1960.

28 T. E. Wilhelm, T. R. Belderrain, S. N. Brown and R. H. Grubbs,

Organometallics, 1997, 16, 3867.

29 W. J. Middleton, J. Org. Chem., 1975, 40, 574.

30 W. Miles, C. Berreth and P. Smiley, T etrahedron L ett., 1993, 34,

5221.

20 J. S. Freundlich, R. R. Schrock and W. M. Davis, J. Am. Chem.

Soc., 1996, 118, 3643.

21 M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G.

Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson,

J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G.

Zakrzewski, J. V. Ortiz, J. B. Foresman, C. Y. Peng, P. Y. Ayala,

W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts,

R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P.

Stewart, M. HeadÈGordon, C. Gonzalez and J. A. Pople, GAUSS-

IAN 94, Revision B3, Gaussian Inc., Pittsburgh, 1995.

31 R. Knorr and T. Roman, Angew. Chem., Int. Ed. Engl., 1984, 23,

366.

22 A. D. Becke, J. Chem. Phys., 1993, 98, 5648.

23 P. G. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82, 299.

Paper a907624g

26

New J. Chem., 2000, 24, 9È26

Article Doi

Coordinated carbenes from electron-rich olefins on RuHCl(PPr3/(i))2

DOI: 10.1039/a907624g

Source and publish data:

Authors:

Article abstract of DOI:10.1039/a907624g

Full text of DOI:10.1039/a907624g

Products guided by the article

R&D Labs maybe for 262359-23-9

Relevant to this article

Hot Product