Mono- and bis-(acetylacetonato) complexes of arene-ruthenium(II) and arene-osmium(II): Variation of the binding mode of η1-acetylacetonate with the nature of the arene

655

Mono- and bis-(acetylacetonato) complexes of

arene–ruthenium(II) and arene–osmium(II):

variation of the binding mode of η¹-

acetylacetonate with the nature of the arene

Martin A. Bennett, Thomas R.B. Mitchell, Mark R. Stevens, and Anthony C. Willis

Abstract: The mono(acetylacetonato) complexes [MCl(O,O′-acac)(η⁶-arene)] (M = Ru, Os, arene = C₆H₆, 1,3,5-

C₆H₃Me₃, C₆Me₆; M = Os, arene = 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃), which are formed from [MCl₂(η⁶-arene)]₂and thal-

lium or sodium acetylacetonate, react with thallium acetylacetonate to give bis(acetylacetonato) complexes [M(O,O′-

acac)(η¹-acac)(η⁶-arene)]. The η¹-acac ligand is bound through the γ-carbon atom for M = Ru, Os, arene = C₆H₆; M =

Os, arene = 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃and through a keto-oxygen atom for M = Ru, Os, arene = 1,3,5-C₆H₃Me₃,

C₆Me₆, the difference being attributed to a combination of steric and electronic effects. Cationic ruthenium(II) deriva-

tives [Ru(L)(O,O′-acac)(η⁶-arene]⁺(arene = C₆H₆, 1,3,5-C₆H₃Me₃, C₆Me₆; L = DMSO, MeCN, py, PPh₃) and

[Ru(CO)(O,O′-acac)(η⁶-arene]⁺(arene = 1,3,5-C₆H₃Me₃,C₆Me₆), and neutral osmium(II) η¹-acetato derivatives [Os(η¹-

OAc)(O,O′-acac)(η⁶-arene)] (arene = C₆H₆, 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃, 1,3,5-C₆H₃Me₃, C₆Me₆) are also described.

The molecular structures of the following complexes have been determined by X-ray crystallography: [Os(O,O′-

acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)], triclinic, space group P1 (No. 2), a = 9.922(2), b = 9.974(2), and c = 11.001(2) Å,

α = 68.33(1), β = 64.18(1), and γ = 62.38(1)°, V = 849.0(3) Å³, Z = 2; [Os(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)],

monoclinic, space group C2/c (No. 15), a = 16.032(4), b = 11.989(3), and c = 21.562(7) Å, β = 108.91(2)°, V =

3921(2) Å, Z = 8; [Os(η¹-OAc)(O,O′-acac)(η⁶-C₆H₆)], triclinic, space group P1 (No. 2), a = 8.368(4),

b = 8.402(4), and c = 11.008(4) Å, α = 71.68(3), β = 69.35(3), and γ = 69.77(3)°, V = 663.0(6) Å³, Z = 2.

Key words: arene–ruthenium, arene–osmium, acetylacetone, crystal structures.

Résumé : Les complexes mono(acétylacétonato) [MCl(O,O′-acac)(η⁶-arène)] (M = Ru, Os, arène = C₆H₆, 1,3,5-C₆H₃Me₃,

C₆Me₆; M = Os, arène = 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃), qui se forment par réaction de [MCl₂(η⁶-arène)]₂avec

l’acétylacétonate de thallium ou de sodium, réagissent avec l’acétylacétonate de thallium pour donner des complexes

bis(acétylacétonato) [M(O,O′-acac)(η¹-acac)(η⁶-arène)]. Le ligand η¹est lié par le carbone γ dans les cas où M = Ru,

Os, arène = C₆H₆; M = Os, arène = 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃et par l’atome d’oxygène de la cétone lorsque M =

Ru, Os, arène = 1,3,5-C₆H₃Me₃, C₆Me₆; on attribue les différences à une combinaison d’effets stériques et électroni-

ques. On décrit aussi les dérivés cationiques du ruthénium [Ru(L)(O,O′-acac)(η⁶-arène)]⁺(arène = C₆H₆, 1,3,5-

C₆H₃Me₃, C₆Me₆; L = DMSO; MeCN; py, PPh₃) et [Ru(CO)(O,O′-acac)(η⁶-arène)]⁺(arène = 1,3,5-C₆H₃Me₃, C₆Me₆) et

les dérivés neutres η¹-acétato de l’osmium(II) [Os(η¹-OAc)(O,O′-acac)(η⁶-arène)] (arène = C₆H₆, 1,2-C₆H₄Me₂, 1,2,3-

C₆H₃Me₃, 1,3,5-C₆H₃Me₃, C₆Me₆). Les structures moléculaires des complexes suivants ont été déterminées par diffrac-

tion des rayons X: [Os(O,O′-acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)], triclinique, groupe d’espace P1 (No. 2), avec a =

9,922(2), b = 9,974(2) et c = 11,001(2) Å, α = 68,33(1), β = 64,18(1) et γ = 62,38(1)°, V = 849,0(3) Å³et Z = 2;

[Os(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)], monoclinique, groupe d’espace C2/c (No. 15), avec a = 16,032(4), b =

11,989(3) et c = 21,562(7) Å, β = 108,91(2), V = 3921(2) Å³et Z = 8; [Os(η¹-OAc)(O,O′-acac)(η⁶-C₆H₆)], triclinique,

groupe d’espace P1 (No. 2), avec a = 8,368(4), b = 8,402(4) et c = 11,008(4) Å, α = 71,68(3), β = 69,35(3) et γ =

69,77(3)°, V = 663,0(6) Å³et Z = 2.

Mots clés : arène–ruthénium, arène–osmium, acétylacétone, structures cristallines.

[Traduit par la Rédaction] Bennett et al. 669

Received November 17, 2000. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on June 30, 2001.

This paper is dedicated to Brian James on the occasion of his 65^thbirthday, and in recognition of his many contributions to

organometallic chemistry, coordination chemistry, and homogeneous catalysis.

M.A. Bennett,¹T.R.B. Mitchell, M.R. Stevens, and A.C. Willis. Research School of Chemistry, Australian National University,

Canberra, ACT 0200, Australia.

¹Corresponding author (telephone: (61) 6249-3639; fax: (61) 6249-3216; email: bennett@rsc.anu.edu.au).

Can. J. Chem. 79: 655–669 (2001)

DOI: 10.1139/cjc-79-5/6-655

656

Can. J. Chem. Vol. 79, 2001

Fig. 1. Common binding modes of acetylacetonate to metal ions.

Introduction

Although the acac anion (CH₃COCHCOCH₃)^–(see List of

abbreviations),²and the mono-anions of other β-dicarbonyl

compounds, usually behave as bidentate chelate O,O′-donors

to transition metal ions, the more electronegative elements

towards the end of the 4d- and 5d-series, especially Hg(II),

Au(I), Au(III), Pt(II), Pd(II), Pt(IV), and Ir(III), display a

pronounced tendency to bind to the γ-carbon atom of

acetylacetonate ion (Fig. 1) (1–3). There are fewer examples

of this behaviour in the coordination chemistry of rhodium,

ruthenium, and osmium, which form stable chelate com-

plexes such as [M(O,O′-acac)₃]. Starting from the η⁵-

pentamethylcyclopentadienyl complexes [MCl₂(η⁵-C₅Me₅)]₂

(M = Rh, Ir), Maitlis et al. (4) have prepared [MCl(O,O′-

acac)(η⁵-C₅Me₅)], [Ir(O,O′-acac)(η¹-C-acac)(η⁵-C₅Me₅)], and

[Rh₂(µ-O,O′,C-acac)₂(η⁵-C₅Me₅)₂]Y₂(Y = BF₄, PF₆) (1); in

1 each acac anion is bound as an O,O′-bidentate ligand to

one rhodium atom and as a γ-C-donor to the other. Some

C₆Me₆; M = Os, arene = 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃) have

been prepared in yields of 60–80% by reaction of 1 mol of

the dichloride dimers [MCl₂(η⁶-arene)]₂with 2 mol of thal-

lium acetylacetonate or sodium acetylacetonate in dichloro-

methane or dichloromethane–methanol at room temperature.

The ruthenium compounds can also be obtained, in generally

lower yield, by heating [RuCl₂(η⁶-arene)]₂with acetylacetone

in DMF in the presence of anhyd Na₂CO₃for 2–10 min at

100°C; longer periods or higher temperatures cause the for-

mation of [Ru(acac)₃]. The complexes are orange or yellow,

air-stable, microcrystalline solids that are very soluble in

chloroform, dichloromethane, or methanol and are poorly

soluble in benzene or ether. Molecular weight determinations

in dichloromethane confirm that the ruthenium compounds

are monomeric. Selected spectroscopic data are collected in

Tables 1 and 2. In addition to the expected resonances in the

region of δ 5 arising from the protons of the complexed

1

arene, the H NMR spectra show a 1H singlet at δ 4.9–5.1

and a 6H singlet at δ ca. 1.9 due to the γ-proton and the

methyl protons of the acac group, respectively. The IR spec-

tra show a pair of strong bands at ca. 1570 and 1510 cm^–1,

which are assignable to coupled ν(C=O) + ν(C=C) modes of

the bidentate O,O′-acetylacetonate (1–3, 7). Thus, the data

are in agreement with the half-sandwich formulation 2, similar

to that proposed for the p-cymene–ruthenium and –osmium

analogues (5, 6).

analogous compounds are known in the isoelectronic η⁶-p-

cymene–ruthenium(II) and –osmium(II) systems. The com-

plexes [MCl(O,O′-acac)(η⁶-cym)] have been obtained by re-

action of [MCl₂(η⁶-cym)]₂with acetylacetone and base (5,

6), and [Os(O,O′-acac)(η¹-C-acac) (η⁶-cym)] is formed by

treatment of the tert-butylimido compound [Os(N-t-Bu) (η⁶-

cym)] with acetylacetone (6). We report here the preparation

and structural characterization of a wider range of (η⁶-

arene)ruthenium(II) and (η⁶-arene)osmium(II) acetylacetonato

complexes, and show that the mode of binding of a second

acetylacetonate anion to the [M(O,O′-acac)(η⁶-arene)] moi-

ety depends on the nature of the arene.

Results and discussion

Mono(acetylacetonato) complexes

Chloro(acetylacetonato) complexes of arene–ruthenium(II)

or arene–osmium(II) of general formula [MCl(acac)(η⁶-

arene)] (M = Ru, Os; arene = C₆H₆, 1,3,5-C₆H₃Me₃,

In a similar manner, we have also made the corresponding

hexafluoroacetylacetonato complexes [RuCl(η⁶-arene)(O,O′-

hfacac)] (arene = C₆H₆, 1,3,5-C₆H₃Me₃,C₆Me₆), whose

²Supplementary material may be purchased from the Depository of Unpublished Data, Document Delivery, CISTI, National Research Council

Canada, Ottawa, ON K1A 0S2, Canada. For information on obtaining material electronically go to http://www.nrc.ca/cisti/irm/unpub_e.shtml.

Crystallographic information has been deposited with the Cambridge Crystallographic Data Centre. Copies of the data can be obtained, free

of charge, on application to the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (Fax: 44-1223-336033 or e-mail:

deposit@ccdc.cam.ac.uk).

Bennett et al.

657

1

Table 1. H NMR data and characteristic IR bands for Ru(acac)(η⁶-arene) and Ru(hfacac)(η⁶-arene) complexes.

¹H NMR (δ)

Complex

Solvent

CDCl₃

acac-Me

acac-γ-H

Arene ring-H

Arene ring-Me

IR^a

[RuCl(O,O′-acac)

(η⁶-C₆H₆)]

1.97 (s, 6H)

5.16 (s, 1H)

5.61 (s, 6H)

1572, 1525

[RuCl(O,O′-acac)

(η⁶-1,3,5-C₆H₃Me₃)]

[RuCl(O,O′-acac)

(η⁶-C₆Me₆)]

[Ru(O,O′-acac)(dmso)

(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(dmso)

(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(dmso)

(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(NCMe)

(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(NCMe)

(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(py)

(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(py)

(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(py)

(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(CO)

(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(CO)

(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(PPh₃)

(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(PPh₃)

(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(PPh₃)

(η⁶-C₆Me₆)]BF₄

[RuCl(O,O′-hfacac)(PPh₃)

(η⁶-C₆H₆)]

[RuCl(O,O′-hfacac)

(η⁶-1,3,5-C₆H₃Me₃)]

[RuCl(O,O′-hfacac)

(η⁶-C₆Me₆)]

CDCl₃

CD₂Cl₂

CDCl₃

CD₂Cl₂

CDCl₃

1.98 (s, 6H)

1.92 (s, 6H)

2.04 (s, 6H)

2.10 (s, 6H)

2.04 (s, 6H)

2.00 (s, 6H)

2.01 (s, 6H)

1.92 (s, 6H)

1.93 (s, 6H)

1.96 (s, 6H)

2.03 (s, 6H)

2.04 (s, 6H)

1.66 (s, 6H)

1.67 (s, 6H)

1.73 (s, 6H)

5.15 (s, 1H)

4.94 (s, 1H)

5.28 (s, 1H)

5.27 (s, 1H)

5.21 (s, 1H)

5.13 (s, 1H)

4.96 (s, 1H)

4.90 (s, 1H)

5.42 (s, 1H)

5.41 (s, 1H)

4.71 (s, 1H)

4.60 (s, 1H)

5.85 (s, 1H)

5.79 (s, 1H)

4.84 (s, 3H)

2.12 (s, 9H)

1.97 (s, 18H)

1583, 1516

1584, 1513

1555, 1519

1565, 1523

1562, 1520

1569, 1514

1569, 1518

nm

5.77 (s, 6H)

4.98 (s, 3H)

2.06 (s, 9H)

2.01 (s, 18H)

5.20 (s, 6H)

2.05 (s, 18H)

5.75 (s, 6H)

5.01 (s, 3H)

1.95 (s, 9H)

1.96 (s, 18H)

2.23 (s, 9H)

2.16 (s, 18H)

nm

5.63 (s, 3H)

1580, 1519

1566, 1522

nm

5.59 (s, 6H)

4.91 (s, 6H)

1.84 (s, 9H)

1.73 (s, 18H)

nm

5.77 (s, 6H)

4.84 (s, 3H)

1628, 1605 (m),

1558

1629, 1584 (m),

1554

1624, 1574 (m),

1547

2.12 (s, 9H)

2.06 (s, 18H)

^aν(C=O), ν(C=C) of acac (KBr, cm^–1); bands are very strong except where indicated; nm = not measured.

IR spectra show strong ν(C=O), ν(C=C) bands in the region

of 1630–1550 cm^–1typical of bidentate O,O′-coordination

of hfacac (7–9). The far-IR spectra of the [RuCl(acac)(η⁶-

arene)] and [RuCl(hfacac)(η⁶-arene)] complexes contain a

medium-intensity band at ca. 280 cm^–1that may be assigned

to ν(RuCl).

Treatment of the [RuCl(O,O′-acac)(η⁶-arene)] complexes

with AgBF₄or AgPF₆in an acetone solution containing neu-

tral ligands (L = dimethylsulfoxide (DMSO), acetonitrile,

pyridine (py), triphenylphosphine) generates cationic com-

plexes [Ru(L)(O,O′-acac)(η⁶-arene)]⁺, which can be isolated

in good yield as their BF₄or PF₆salts. The IR spectra all

show the characteristic pair of bands at ca. 1570 and 1510 cm^–1

due to bidentate, O-bonded acac. The spectroscopic data

(Table 1) are consistent with the half-sandwich structure 3.

In the solid state, the IR spectra of the DMSO complexes

658

Can. J. Chem. Vol. 79, 2001

1

Table 2. H NMR data and characteristic IR bands for Os(η⁶-arene)(acac) complexes.

¹H NMR (δ)^a

Complex

Solvent acac-Me

acac-γ-H

Arene ring-H

Arene ring-Me IR^b

[OsCl(O,O′-acac)(η⁶-C₆H₆)]

C₆D₆

1.90 (s, 6H) 5.28 (s, 1H) 5.42 (s, 6H)

1.87 (s, 6H) 5.25 (s, 1H) 5.39 (m, 2H),

5.46 (m, 2H)

1570, 1527

[OsCl(O,O′-acac)(η⁶-1,2-C₆H₄Me₂)]

1.89 (s, 6H)

2.14 (s, 6H)

1579, 1520

1578, 1516

1580, 1520

CDCl₃1.99 (s, 6H) 5.35 (s, 1H) 5.84 (m, 2H),

5.93 (m, 2H)

[OsCl(O,O′-acac)(η⁶-1,2,3-C₆H₃Me₃)]

C₆D₆

1.87 (s, 6H) 5.23 (s, 1H) 5.29 (d, 2H),

5.53 (t, J = 5, 1H)

CD₂Cl₂1.94 (s, 6H) 5.30 (s, 1H) 5.68 (d, 2H),

5.87 (t, J = 5, 1H)

1.88 (s, 6H) 5.26 (s, 1H) 5.00 (s, 3H)

CDCl₃1.98 (s, 6H) 5.35 (s, 1H) 5.46 (s, 3H)

C₆D₆1.83 (s, 6H) 5.14 (s, 1H)

CDCl₃1.95 (s, 6H) 5.22 (s, 1H)

1.76 (s, 3H),

1.95 (s, 6H)

1.95 (s, 3H),

2.10 (s, 6H)

2.02 (s, 9H)

2.17 (s, 9H)

[OsCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]

[OsCl(O,O′-acac)(η⁶-C₆Me₆)]

C₆D₆

1.91 (s, 18H) 1580, 1518

2.03 (s, 18H)

1625,^d1580,

[Os(OAc)(O,O′-acac)(η⁶-C₆H₆)]^c

[Os(OAc)(O,O′-acac)(η⁶-1,2-C₆H₄Me₂)]^e

C₆D₆

1.87 (s, 6H) 5.23 (s, 1H) 5.72 (s, 6H)

1525

1631,^d1581,

1519

1634,^d1579,

1522

1626,^d1576,

1530

C₆D₆

1.85 (s, 6H) 5.19 (s, 1H) 5.79 (m, 2H),

1.83 (s, 6H)

6.06 (m, 2H)

1.89 (s, 6H) 5.14 (s, 1H) 5.78 (d, 2H),

[Os(OAc)(O,O′-acac)(η⁶-1,2,3-C₆H₃Me₃)]^eC₆D₆

[Os(OAc)(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]^eC₆D₆

1.65 (s, 3H),

1.83 (s, 6H)

2.08 (s, 9H)

6.50 (t, J = 5, 1H)

1.83 (s, 6H) 5.11 (s, 1H) 5.29 (s, 3H)

1.84 (s, 6H) 5.06 (s, 1H)

[Os(OAc)(O,O′-acac)(η⁶-C₆Me₆)] ^f

C₆D₆

2.01 (s, 18H) 1635,^d1575,

1524

^aCoupling constants (J) in Hz.

^bν(C=O), ν(C=C) of acac (KBr, cm^–1); bands are very strong.

^cδ 2.37 (s, 3H, CH₃CO₂).

^dν(C=O) of acetate.

^eδ 2.38 (s, 3H, CH₃CO₂).

^fδ 2.35 (s, 3H, CH₃CO₂).

contain a band at ca. 1120 cm^–1, which is assigned to ν(S=O)

of S-bonded DMSO (10a). The region 950–1100 cm^–1where

ν(S=O) of O-bonded DMSO is expected to appear is masked

by an intense ν(BF) absorption of the BF₄anion, but the

spectrum of [Ru(DMSO)(O,O′-acac)(η⁶-C₆H₆)]PF₆showed

no band attributable to ν(S=O) of O-bonded DMSO. How-

ever, the IR spectrum of [Ru(DMSO)(O,O′-acac)(η⁶-

C₆H₆)]PF₆in CD₂Cl₂contains a strong band at 1055 cm^–1

due to free DMSO, in addition to the band at 1112 cm^–1due

to S-coordinated DMSO, showing that this ligand is readily

ders that are insoluble in chloroform, dichloromethane, or

methanol and do not redissolve in acetone. They do dissolve

in acetonitrile or DMSO-d₆to generate solutions of the appro-

priate cations [Ru(L)(O,O′-acac)(η⁶-arene)]⁺(L = MeCN,

1

DMSO-d₆), as shown by H NMR spectroscopy. Elemental

analyses of the yellow solids were not completely satisfac-

tory, but the presence of a strong ν(C=O) band at 1620 cm^–1

in the IR spectra suggests that the complexes are the (η⁶-

arene)ruthenium(II) analogues (4) of the binuclear Rh(η⁵-

C₅Me₅) complex 1, containing bridging O,O′,C-acac groups.

1

lost from the coordination sphere. The H NMR spectra of

the DMSO complexes in CD₂Cl₂show a 6H singlet at δ 2.6

due to Me₂SO, the chemical shift being similar to that of

free DMSO (δ 2.53), and addition of DMSO to the solution

shifts the resonance towards that of free DMSO; hence, there

is rapid exchange on the NMR timescale between free and

coordinated DMSO. This conclusion was confirmed by add-

ing DMSO-d₆(6 mol) to [Ru(O,O′-acac) (DMSO)(η⁶-C₆H₆)]

1

in CH₂Cl₂; the H NMR spectrum of the recovered complex

showed the presence of only about one-sixth of the original

DMSO methyl protons. Since the observations imply the ex-

istence of the coordinatively unsaturated or solvent-stabilized

species [Ru(O,O′-acac)(η⁶-arene)]⁺, we treated the

[RuCl(O,O′-acac)(η⁶-arene)] complexes with AgBF₄or AgPF₆

in acetone. Silver chloride is precipitated, and yellow solu-

tions are formed that presumably contain [Ru(acetone)(O,O′-

acac)(η⁶-arene)]⁺. Addition of ether precipitates yellow pow-

Cationic carbonyl complexes [Ru(CO)(O,O′-acac)(η⁶-arene)]⁺

(arene = 1,3,5-C₆H₃Me₃, C₆Me₆) can be isolated as their BF₄

Bennett et al.

659

salts by bubbling CO through the yellow solutions containing

[Ru(acetone)(O,O′-acac)(η⁶-arene)]⁺. The mesitylene

complex is unstable in chloroform over a period of hours

and decomposes slowly in air. The IR spectra show an in-

tense ν(CO) band at ca. 2030–2050 cm^–1. Attempts to pre-

pare ethylene analogues were unsuccessful. Under the same

conditions, CO displaces benzene from solutions of

[Ru(L)(O,O′-acac)(η⁶-C₆H₆)]BF₄(L = Me₂CO, MeCN) to

give an intractable brown oil. Addition of ether to an

acetonitrile solution gave a low yield of a pale yellow crys-

talline salt formulated as [Ru(O,O′-acac)(CO)(MeCN)₃]BF₄

on the basis of spectroscopic data. In addition to the usual

resonances of coordinated acac there are two singlets in a

C₆Me₆) are obtained similarly from [OsCl(O,O′-acac)(η⁶-arene)],

and the benzene compound can also be isolated from the re-

action of [OsCl₂(η⁶-C₆H₆)]₂with Tl(acac) in a 1:4 mol ratio

in methanol. At a late stage of the study, during attempts to

grow single crystals of [Os(acac)₂(η⁶-C₆H₆)], we realized

that the η¹-acetato complexes [Os(η¹-O₂CMe)(O,O′-acac)(η⁶-

arene)] are formed as byproducts in these reactions; these

complexes have been prepared independently and have been

fully characterized (see above). We have not established

whether the byproducts arose from adventitious thallium ac-

etate impurity in the sample of Tl(acac), or more likely,

from a catalyzed process similar to the known base-

promoted decomposition of acetylacetonate ion to acetate

ion (11). In most cases the less soluble acetato complexes

could be separated from the bis(acetylacetonato) complexes

by fractional crystallization.

1

2:1 ratio in the H NMR spectrum at δ ca. 2.5 corresponding to

the methyl protons of coordinated acetonitrile. The IR spec-

trum contains a pair of weak bands in the region of

2300 cm^–1arising from ν(CN) of coordinated acetonitrile, a

strong ν(CO) band at 1982 cm^–1, and the usual pair of O,O′-

acac bands at ca. 1570 and 1510 cm^–1. These data are con-

sistent with either of the octahedral structures 5a or 5b in

which the acetonitrile ligands adopt a mer or fac arrangement

about ruthenium, respectively.

The key spectroscopic data for the [M(acac)₂(η⁶-arene)]

complexes are collected in Table 3. For the ruthenium com-

pound [Ru(acac)₂(η⁶-C₆H₆)], and for the osmium com-

pounds [Os(acac)₂(η⁶-arene)] (arene = C₆H₆, 1,2-C₆H₄Me₂,

1,2,3-C₆H₃Me₃), these data indicate a structure (6) in which

one acac group is still bidentate (O,O′) while the other is

bound as a monodentate ligand through the γ-carbon atom.

Chloride ion can also be abstracted from the osmium

complexes [OsCl(O,O′-acac)(η⁶-arene)], which react with sil-

ver acetate to give the acetato complexes [Os(η¹-OAc)(O,O′-

acac)(η⁶-arene)]. Their IR spectra (Table 2) show, in addition

to the usual O,O′-acac bands at ca. 1580 and 1520 cm^–1, a

strong ν(C=O) absorption at ca. 1630 cm^–1characteristic of

either monodentate or asymmetric bidentate acetate (10b);

Thus, the solid state and solution IR spectra show two pairs

of strong bands in the ν(C=O), ν(C=C) region, one due to

O,O′-acac at ca. 1580 and 1520 cm^–1, the other at 1650–

1680 and 1620 cm^–1assignable to CH(COMe)₂(7). Corre-

spondingly, the ¹H NMR spectra contain a singlet acac

methyl resonance at δ 1.9–2.3 (6H) and a γ-CH resonance at

δ 4.3–4.7 assignable to C-bonded acac, in addition to a

methyl resonance at δ ca. 1.8 (6H) and a γ-CH resonance at

ca. δ 5.2 due to O,O′-acac. In contrast, although the ¹H NMR

spectra of [M(acac)₂(η⁶-arene)] (M = Ru, Os; arene = 1,3,5-

C₆H₃Me₃, C₆Me₆) contain resonances typical of O,O′-acac,

the η¹- acac group in each case gives rise to two methyl

singlets at δ ca. 2.5 and 3.0, and a γ-CH singlet at δ ca. 5.0,

consistent with binding through a keto-oxygen atom (struc-

ture 7). The IR spectra show two pairs of strong bands in the

ν(C=O), ν(C=C) region, one due to O,O′-acac at ca. 1580

and 1520 cm^–1, the other at ca. 1620 and 1500 cm^–1. The

bands in the second pair clearly differ from those due to

η¹-C-bonded acac and are similar to those reported for the

1

the H NMR spectra show the expected 3H singlet at δ ca.

1.9. The structure of the η⁶-benzene complex has been con-

firmed by X-ray crystallography (see below).

Bis(acetylacetonato) complexes

The [RuCl(O,O′-acac)(η⁶-arene)] complexes react with an

equimolar quantity of Tl(acac) in methanol at –20°C to give

orange-red (benzene) or yellow (mesitylene, hexamethylbenzene)

microcrystalline solids of formula [Ru(acac)₂(η⁶-arene)]. At-

tempts to prepare analogous bis(hfacac) complexes were un-

successful. The benzene complex decomposes both as a solid

and in solution, and satisfactory elemental analyses could not

be obtained. The mesitylene and hexamethylbenzene com-

plexes are stable for short periods in the solid state at room

temperature, but they also decompose in solution at room

temperature over periods ranging from minutes in chloro-

form to several days in methanol. The corresponding ther-

mally more stable osmium compounds [Os(acac)₂(η⁶-arene)]

(arene = C₆H₆, 1,2-C₆H₄Me₂, 1,2,3-C₆H₃Me₃, 1,3,5-C₆H₃Me₃,

structurally

characterized

compound

[Rh(η¹-O-

acac)(CO){P(iPr)₃}₂] (1613 (w), 1515 (m) cm^–1)) (12). How-

ever, the bands reported for trans-[Pt(η¹-O-acac)₂(PEt₃)₂] and

1

Table 3. H NMR data and characteristic IR bands for M(acac)₂(η⁶-arene) complexes (M = Ru, Os).

¹H NMR (δ)

Complex

Solvent

C₆D₆

acac-Me

acac-γ-H

Arene ring-H

Arene ring-Me

IR^a

[Ru(O,O′-acac)

1.77 (s, 6H) (O,O′); 2.06

(s, 6 Η) (η¹-C)

1.83 (s, 6H) (O,O′); 1.98

(s, 6H) (η¹-C)

5.04 (s, 1H) (O,O′);

3.35 (s, 1 Η) (η¹-C)

5.60 (s, 1H) (O,O′);

3.12 (s, 1 Η) (η¹-C)

4.71 (s, 6H)

1574, 1520 (O,O′);

(η¹-C-acac)(η⁶-C₆H₆)]

1672, 1623 (m) (η¹-C)

CD₂Cl₂

C₆D₆

5.26 (s, 6H)

4.77 (s, 3H)

[Ru(O,O′-acac)(η¹-O-acac)

(η⁶-1,3,5-C₆H₃Me₃)]

1.89 (s, 6H) (O,O′); 1.91

(s, 3H), 2.17 (s, 3H) (η¹-O)

5.43 (s, 1H) (O,O′);

4.97 (s, 1H) (η¹-O)

2.08 (s, 9H)

1.96 (s, 18H)

1579, 1525 (O,O′);

1616 (m), 1500 (η¹-O)

[Ru(O,O′-acac)(η¹-O-acac)

1.89 (s, 6H) (O,O′); 1.84

(s, 3H), 2.14 (s, 3H) (η¹-O)

5.14 (s, 1H) (O,O′);

4.94 (s, 1H) (η¹-O)

1582, 1519 (O,O′);

(η⁶-C₆Me₆)]

1613 (m), 1489 (η¹-C)

[Os(O,O′-acac)(η¹-C-acac)

(η⁶-C₆H₆)]

1.88 (s, 6H) (O,O′)

5.27 (s, 1H) (O,O′);

4.64 (s, 1H) (η¹-C)

5.22 (s, 6H)

1570, 1520 (O,O′);

1678, 1631 (m) (η¹-C)

1583, 1523 (O,O′);

2.28 (s, 6H) (η¹-C)

1678 1650 (sh), 1633 (η¹-C)^b

[Os(O,O′-acac)(η¹-C-acac)

(η⁶-1,2-C₆H₄Me₂)]

C₆D₆

1.84 (s, 6H) (O,O′); 2.29 (s, 6H)

5.22 (s, 1H) (O,O′);

4.69 (s, 1H) (η¹-C)

5.42 (s, 1H) (O,O′);

4.30 (s, 1H) (η¹-C)

5.23 (m, 2H),

5.38 (m, 2H)

5.33 (s, 2H),

5.47 (s, 2H)

1.57 (s, 6H)

1.88 (s, 6H)

1573, 1520 (O,O′);

1646, 1630 (η¹-C)

1581, 1523 (O,O′);

1675, 1650 (sh), 1632 (η¹-C)^b

(η¹-C)

CD₂Cl₂

1.90 (s, 6H) (O,O′); 1.94 (s, 6H)

(η¹-C)

[Os(O,O′-acac)(η¹-C-acac)

(η⁶-1,2,3-C₆H₃Me₃)]

C₆D₆

1.82 (s, 6H) (O,O′)

5.17 (s, 1H) (O,O′);

4.73 (s, 1H) (η¹-C)

4.87 (d, 2H),

6.08 (t, 1H)

1.48 (s, 3H),

1.58 (s, 6H)

1575, 1527 (O,O′);

1646, 1626 (m) (η¹-C)

1581, 1522 (O,O′);

2.34 (s, 6H) (η¹-C)

1673, 1631 (η¹-C)^b

1576, 1531 (O,O′);

[Os(O,O′-acac)(η¹-O-acac)

(η⁶-1,3,5-C₆H₃Me₃)]

C₆D₆

1.77 (s, 6H) (O,O′); 2.47 (s, 3H),

3.05 (s, 3H) (η¹-O)

5.85 (s, 1H) (O,O′);

5.05 (s, 1H) (η¹-C)

4.95 (s, 3H)

5.41 (s, 3H)

1.95 (s, 9H)

2.16 (s, 9H)

1.84 (s, 18H)

1618 (m), 1502 (η¹-C)

CD₂Cl₂

C₆D₆

1.89 (s, 6H) (O,O′); 1.93 (s, 3H),

2.23 (s, 3H) (η¹-O)

5.46 (s, 1H) (O,O′);

5.23 (s, 1H) (η¹-O)

1582, 1524 (O,O′);

1617 (w), 1503 (η¹-O)^b

[Os(O,O′-acac)(η¹-O-acac)

(η⁶-C₆Me₆)]

1.76 (s, 6H) (O,O′)

5.52 (s, 1H) (O,O′);

5.00 (s, 1H) (η¹-O)

1580, 1526 (O,O′);

1624 (m), 1499 (η¹-O)

1579, 1523 (O,O′);

2.46 (s, 3H), 2.99 (s, 3H) (η¹-O)

1620 (w), 1502 (η¹-O)^b

a

ν(C=O), ν(C=C) of acac (KBr, cm^–1); bands are strong or very strong except where indicated.

^bIn CH₂Cl₂.

Bennett et al.

661

Fig. 2. Molecular structure of [Os(O,O′-acac)(η¹-C-acac)(η⁶-1,2-

C₆H₄Me₂)] with selected atom labeling. Thermal ellipsoids in the

ORTEP plot show 30% probability levels.

trans-[Pt(η¹-O-acac)₂(C₅H₁₀NH)₂] appear at somewhat dif-

ferent frequencies, namely 1650 (s) and 1605 (m) cm^–1(13)

and 1621 (vs) and 1583 (w) cm^–1(14), respectively, so that

conclusions based on IR data must be treated with caution.

Nevertheless, the proposed structures have been confirmed

by single crystal X-ray diffraction studies (see below).

1

Although the H NMR spectrum of [Ru(acac)₂(η⁶-C₆Me₆)]

in coordinating solvents such as acetone and acetonitrile is

similar to that in CDCl₃or CD₂Cl₂, the behaviour in metha-

nol is different and suggestive of selective protonation of the

acac ligands. At 28°C in methanol-d₄there is one broad res-

onance at δ ca. 1.97 arising from the methyl protons of both

acac ligands; the methine protons exchange rapidly with re-

sidual protons in the solvent and appear as a singlet at δ 4.77

(2H). It should be noted that the methine proton of

[RuCl(acac)(η⁶-C₆Me₆)] undergoes a similar but slower pro-

cess at room temperature, complete exchange requiring ca.

η³-acetylacetonate dianion derived by deprotonation of the

intermediate [Ru(O,O′-acac) (solvent)(η⁶-C₆Me₆)]⁺. Examples

of this mode of coordination are known for palladium(II)

(16) and platinum(II) (17).

Structures determined by X-ray crystallography

The molecular structures of [Os(O,O′-acac)(η¹-C-

acac)(η⁶-1,2-C₆H₄Me₂)], [Os(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-

C₆H₃Me₃)], and [Os(η¹-OAc)(O,O′-acac)(η⁶-C₆H₆)] are

shown in Figs. 2–4, respectively, with atom labeling. They

confirm the conclusions drawn above on the basis of spec-

troscopic data. Selected bond lengths and angles of these

three compounds are listed in Tables 4–6, respectively.

All three compounds contain an almost planar η⁶-arene

ring attached to an osmium atom that is coordinated trigonally

by a bidentate O,O′-bonded acac and a monodentate ligand.

In the first compound, the η¹-acac group is bound through

carbon atom C(8), the Os(1)–C(8) vector approximately

eclipsing one of the Os–C(arene) vectors (Os(1)–C(13)). The

orientation of the η⁶-arene ring places its two methyl groups

well away from the COCH₃substituents of the η¹-acac

group. The C=O groups of η¹-acac adopt a mutually anti-

orientation, and their bond lengths are as expected (1.221(5),

1.235(5) Å). The Os(1)—C(8) bond length (2.233(4) Å) is

slightly but significantly greater than the limited number of

reported Os(II)—CH₃and Os(II)—C sp³distances, which

fall in the range of 2.17–2.21 Å (18–21). In the second com-

pound, the η¹-acac group is bound through one of the keto-

oxygen atoms, i.e., it acts as a η¹-enolate; the Os—O vectors

of the trigonal array almost eclipse the methyl-bearing car-

bon atoms of the η⁶-arene ring. The Os—O(η¹-acac) dis-

tance (2.099(5) Å) is just significantly greater than the Os—O

(O,O′-acac) distances (2.078(5), 2.072(5) Å). The geometry

and metrical parameters of the enolate fragment are similar

to those observed in the acetylacetonato derivatives trans-

[Rh(η¹-O-acac)(CO)L₂] (L = P(iPr)₃, PCy₃) (12, 22),

1

100 h. At 7°C the H NMR spectrum of [Ru(acac)₂(η⁶-

C₆Me₆)] in methanol-d₄contains two broad methyl singlets

of approximately equal intensity at δ 1.93 and ca. 2.01, the

latter being partly obscured by the C₆Me₆singlet. At this

temperature, protonation of the monodentate ligand and sub-

sequent rapid exchange between coordinated and uncoordi-

nated acetylacetone averages the methyl environments of the

enolate ligand, whereas at 28°C this process is rapid for both

acac ligands. Only at –3°C in methanol-d₄do the expected

three acac methyl singlets appear.

The acac methyl protons of [Ru(acac)₂(η⁶-C₆Me₆)] ex-

change completely with CH₃OD over a period of 3 days at

room temperature, and the IR spectrum of the resulting

deuterated complex shows characteristic shifts of the

ν(C=O), ν(C=C) bands to ca. 1560 and 1480 cm^–1(15). A

plausible intermediate in this process is 8, which contains

662

Can. J. Chem. Vol. 79, 2001

Fig. 3. Molecular structure of [Os(O,O′-acac)(η¹-O-acac)(η⁶-

1,3,5-C₆H₃Me₃)] with selected atom labeling. Thermal ellipsoids

in the ORTEP plot show 30% probability levels.

Fig. 4. Molecular structure of [Os(O,O′-acac)(η¹-O₂CMe)(η⁶-

C₆H₆)] with selected atom labeling. Thermal ellipsoids in the

ORTEP plot show 30% probability levels.

[Cr(CO)₅{PPh(η¹-O-acac)₂}] (23), and [Mn(η⁵-

C₅H₅)(CO)₂{PPh₂(η¹-O-acac)}] (24), and in the

trifluoroacetylacetonato complex [Pd(O,O′-tfac)(η¹-O-

tfac){P(o-tolyl)₃}] (25); the enolate group is almost planar,

the Os-O and COCH₃groups are mutually trans about the

C—C bond, and the C=C and C=O groups are mutually cis.

As expected, the C—O bond length of the bound enolate

(1.301(9) Å) is greater than that of the uncoordinated C=O

group (1.23(1) Å). The structure of [Os(η¹-OAc)(O,O′-

acac)(η⁶-C₆H₆)] confirms that the acetato group is

monodentate, the Os—O bond length (2.077(3) Å) being

similar to those to the O,O′-acac unit (2.074(3), 2.064(3) Å).

In contrast to the two structures discussed above, the Os—O

vectors of the trigonal array do not eclipse the arene carbon

atoms.

Starting materials

Hydrated ruthenium chloride and osmium tetraoxide were

obtained from Johnson Matthey, U.K. The acetylacetonates

of sodium and thallium were prepared by literature proce-

dures (34, 35). Most of the [MCl₂(η⁶-arene)]₂complexes

were made by reaction of the appropriate cyclohexa-1,3-

diene or cyclohexa-1,4-diene with hydrated RuCl₃or

Na₂OsCl₆in refluxing ethanol (27–29). The previously un-

known compound [OsCl₂(η⁶-1,2,3-C₆H₃Me₃)]₂was made in

this way as orange microcrystals in 67% yield from

Na₂OsCl₆and a mixture of dihydro-isomers obtained by Li–

NH₃reduction of the arene. Anal. calcd. for C₉H₁₂Cl₂Os: C

28.35, H 3.2; found: C 27.8, H 2.8. The hexamethylbenzene

complexes [MCl₂(η⁶-C₆Me₆)]₂were prepared by fusion of

the corresponding p-cymene complexes with an excess of

hexamethylbenzene (19, 30, 31). Since cyclohexa-1,3-diene

undergoes extensive polymerization on heating with osmium

chlorides, we prepared [OsI₂(η⁶-C₆H₆)]₂(32), converted it

into the bis(acetate) by treatment with AgOAc for 2 days,

and treated the bis(acetate) with conc. HCl to give

[OsCl₂(η²-C₆H₆)]₂(33).

Experimental

General procedures

All experiments were performed under an inert atmo-

sphere with use of Schlenk techniques, and all solvents were

dried and degassed by standard methods before use. ¹H

NMR spectra were measured on Varian HA-100 or Jeol MH-

100 spectrometers at 100 MHz or on Varian Gemini 300-BB

or VXR-300 spectrometers at 300 MHz. Chemical shifts (δ)

are in ppm referenced to residual proton signals of the sol-

vent; coupling constants (J) are in Hz. IR spectra in the

range 4000–400 cm^–1were recorded as KBr discs or

Nujol™ mulls, or as CH₂Cl₂solutions in 0.1 mm path-

length cells, on PerkinElmer PE 457 or 683 spectrometers.

IR spectra in the range 450–150 cm^–1were measured as

polythene discs on a PerkinElmer FT-1800 instrument. Elec-

tron impact (EI) mass spectra at 70 eV were measured on

Preparations

[RuCl(O,O′-acac)(η⁶-arene)]

(i) A mixture of [RuCl₂(η⁶-C₆H₆)]₂(200 mg, 0.40 mmol)

and Tl(acac) (244 mg, 0.80 mmol) suspended in dichloro-

methane (15 mL) was stirred for 2 h and then filtered

through Celite™ to remove the precipitated TlCl. The or-

ange crystalline product [RuCl(O,O′-acac)(η⁶-C₆H₆)], which

formed on cooling the filtrate, was separated by filtration,

washed with ether, and dried in vacuo. The yield was

165 mg (66%). Similarly prepared from [RuCl₂(η⁶-1,3,5-

C₆H₃Me₃)]₂or [RuCl₂(η⁶-C₆Me₆)]₂and Tl(acac) with peri-

ods of stirring of 2 h and 10 min, respectively, were

1

AEI–MS 902 or VG Micromass 7070 F spectrometers. H

NMR and selected IR data are collected in Tables 1–3; ele-

mental analyses, which were carried out in-house, are listed

in Tables 7 and 8.

Bennett et al.

663

Table 4. Selected bond distances and angles in [Os(O,O′-

acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)].

Table 5. Selected bond distances and angles in [Os(O,O′-

acac)(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)].

Bond distances (Å)

Os(1)—O(1)

Os(1)—C(8)

Os(1)—C(12)

Os(1)—C(14)

Os(1)—C(16)

O(2)—C(4)

O(4)—C(9)

C(2)—C(3)

C(4)—C(5)

C(7)—C(8)

C(9)—C(10)

2.076(2)

2.233(4)

2.195(3)

2.189(4)

2.218(4)

1.277(4)

1.235(5)

1.388(5)

1.506(5)

1.481(6)

1.495(6)

Os(1)—O(2)

Os(1)—C(11)

Os(1)—C(13)

Os(1)—C(15)

O(1)—C(2)

O(3)—C(7)

C(1)—C(2)

C(3)—C(4)

C(6)—C(7)

C(8)—C(9)

C—C(arom)

2.078(2)

2.207(4)

2.156(3)

2.177(4)

1.289(4)

1.221(5)

1.503(5)

1.389(5)

1.511(6)

1.483(5)

1.405(6)–

1.431(6)

Os(1)—O(1)

Os(1)—O(3)

Os(1)—C(12)

Os(1)—C(14)

Os(1)—C(16)

O(2)—C(4)

O(4)—C(9)

C(2)—C(3)

C(4)—C(5)

C(7)—C(8)

C(9)—C(10)

2.078(5)

2.099(5)

2.172(8)

2.178(8)

1.282(9)

1.23(1)

1.40(1)

1.51(1)

1.36(1)

1.51(1)

Os(1)—O(2)

Os(1)—C(11)

Os(1)—C(13)

Os(1)—C(15)

O(1)—C(2)

O(3)—C(7)

C(1)—C(2)

C(3)—C(4)

C(6)—C(7)

C(8)—C(9)

C—C(arom)

2.072(5)

2.175(8)

2.173(8)

2.159(8)

1.278(9)

1.301(9)

1.50(1)

1.37(1)

1.50(1)

1.43(1)

1.39(1)–

1.45(1)

C(arom)—CH₃

1.508(6),

1.509(6)

C(arom)—CH₃

1.49(1)–

1.51(1)

Bond angles (°)

O(1)-Os(1)-O(2)

O(2)-Os(1)-C(8)

O(1)-C(2)-C(3)

O(2)-C(4)-C(3)

Os(1)-O(1)-C(2)

Os(1)-C(8)-C(7)

C(7)-C(8)-C(9)

O(3)-C(7)-C(8)

O(4)-C(9)-C(10)

Bond angles (°)

O(1)-Os(1)-O(2)

O(2)-Os(1)-O(3)

O(1)-C(2)-C(3)

O(2)-C(4)-C(3)

C(1)-C(2)-C(3)

Os(1)-O(1)-C(2)

Os(1)-O(3)-C(7)

C(6)-C(7)-C(8)

O(4)-C(9)-C(8)

C(8)-C(9)-C(10)

86.82(9)

83.0(1)

O(1)-Os(1)-C(8)

O(1)-C(2)-C(1)

C(2)-C(3)-C(4)

O(2)-C(4)-C(5)

Os(1)-O(2)-C(4)

Os(1)-C(8)-C(9)

C(6)-C(7)-C(8)

O(4)-C(9)-C(8)

C(8)-C(9)-C(10)

83.6(1)

114.8(3)

125.7(3)

115.1(3)

127.5(2)

107.7(3)

120.7(4)

124.4(4)

116.4(3)

87.2(2)

83.5(2)

O(1)-Os(1)-O(3)

O(1)-C(2)-C(1)

C(2)-C(3)-C(4)

O(2)-C(4)-C(5)

C(3)-C(4)-C(5)

Os(1)-O(2)-C(4)

O(3)-C(7)-C(8)

C(7)-C(8)-C(9)

O(4)-C(9)-C(10)

78.4(2)

114.7(8)

125.1(8)

113.2(8)

120.1(8)

125.4(6)

125.9(7)

128.4(8)

116.6(8)

125.7(3)

125.4(3)

126.8(2)

108.7(3)

120.2(3)

120.8(4)

119.2(4)

126.0(8)

126.7(8)

119.3(8)

126.2(6)

128.8(5)

122.5(8)

127.4(9)

116.0(8)

[RuCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)] (81%) and [RuCl(O,

O′-acac)(η⁶-C₆Me₆)] (82%).

Table 6. Selected bond distances and angles in [Os(η¹-OAc)(O,O ′-

acac)(η⁶-C₆H₆)].

(ii)

A

suspension of [RuCl₂(η⁶-C₆H₆)]₂(200 mg,

Bond distances (Å)

0.40 mmol) and Na(acac) (99 mg, 0.81 mmol) in dichloro-

methane–methanol (1:1) (15 mL) was stirred for 2 h at room

temperature. The solution was evaporated to dryness under

reduced pressure. The residue was extracted with dichloro-

methane and the solution was filtered. Addition of ether to

the filtrate and cooling gave orange crystals of the product,

which were separated by filtration, washed with ether, and

dried in vacuo. The yield was 150 mg (60%). The complexes

Os(1)—O(1)

Os(1)—O(3)

Os(1)—C(9)

Os(1)—C(11)

Os(1)—C(13)

O(2)—C(4)

O(4)—C(6)

C(2)—C(3)

C(4)—C(5)

C(7)—C(8)

C—C(arom)

2.074(3)

2.077(3)

2.131(7)

2.148(6)

2.152(7)

1.272(6)

1.219(6)

1.368(8)

1.489(8)

1.481(6)

1.32(1)–

1.46(1)

Os(1)—O(2)

Os(1)—C(8)

Os(1)—C(10)

Os(1)—C(12)

O(1)—C(2)

O(3)—C(6)

C(1)—C(2)

C(3)—C(4)

C(6)—C(7)

C(8)—C(9)

2.064(3)

2.135(7)

2.126(6)

2.128(6)

1.282(6)

1.283(6)

1.501(7)

1.390(8)

1.503(8)

1.483(5)

[RuCl(O,O′-acac)(η⁶-arene)] (arene

=

1,3,5-C₆H₃Me₃,

C₆Me₆) were prepared similarly, with periods of stirring of

2 h and 15 min, respectively, in yields of 60 and 85%, re-

spectively.

(iii) A mixture of [RuCl₂(η⁶-C₆H₆)]₂(200 mg, 0.40 mmol)

and an excess of anhyd Na₂CO₃(1 g) was suspended in

DMF (5 mL) and stirred for 10 min at 100°C. The solution

was filtered and methanol was added to the filtrate. The or-

ange crystals that separated on cooling were washed with

ether and dried in vacuo. The yield was 65 mg (26%).

Similarly prepared were [RuCl(O,O′-acac)(η⁶-1,3,5-

C₆H₃Me₃)] (63%) and [RuCl(O,O′-acac)(η⁶-C₆Me₆)] (29%),

the mixture being heated for only 2 min in the latter case.

Bond angles (°)

O(1)-Os(1)-O(2)

O(2)-Os(1)-O(3)

Os(1)-O(2)-C(4)

O(1)-C(2)-C(1)

C(1)-C(2)-C(3)

O(2)-C(4)-C(3)

C(3)-C(4)-C(5)

O(3)-C(6)-C(7)

87.4(1)

82.4(1)

O(1)-Os(1)-O(3)

Os(1)-O(1)-C(2)

Os(1)-O(3)-C(6)

O(1)-C(2)-C(3)

C(2)-C(3)-C(4)

O(2)-C(4)-C(5)

O(3)-C(6)-O(4)

77.9(1)

126.9(3)

126.1(3)

125.0(5)

127.1(5)

114.8(5)

126.1(5)

127.2(3)

114.7(5)

120.2(5)

125.3(5)

119.8(5)

113.2(5)

[RuCl(O,O′-hfacac)(η⁶-arene)]

(i) A solution of Tl(hfacac) (197 mg, 0.48 mmol) in di-

chloromethane (20 mL) was cooled to 0°C and treated with

[RuCl₂(η⁶-C₆H₆)]₂(200 mg, 0.40 mmol). The suspension

was stirred for 1 min and filtered at 0°C. Addition of ether to

the filtrate gave [RuCl(O,O′-hfacac)(η⁶-C₆H₆)] as an orange

crystalline solid, which was separated by filtration, washed

with ether, and dried in vacuo. The yield was 135 mg (67%).

The complex [RuCl(O,O′-hfacac)(η⁶-1,3,5-C₆H₃Me₃)] was

664

Can. J. Chem. Vol. 79, 2001

Table 7. Elemental analyses for Ru(acac)(η⁶-arene) complexes.

%C

%H

%Other

Complex

Calcd.

Found

Calcd.

Found

Calcd.

Found

[RuCl(O,O′-acac)(η⁶-C₆H₆)]^a

42.0

47.2

51.3

31.3

36.3

40.4

35.2

39.6

43.3

38.4

46.5

43.3

46.9

50.0

41.4

45.3

55.5

57.4

59.1

36.4

42.5

54.4

57.25

42.15

47.6

51.25

31.6

35.5

40.2

34.9

39.1

43.4

38.2

46.8

43.3

46.7

49.8

41.4

45.2

56.0

57.3

59.1

36.2

41.3

53.1

56.5

4.5

5.7

6.3

1.7

2.8

3.8

4.3

5.2

5.9

4.0

5.8

4.1

5.0

5.7

4.4

5.3

4.5

5.1

5.7

4.8

5.0

6.3

7.0

4.4

5.6

6.3

1.7

3.1

4.1

4.3

5.35

5.9

4.2

5.9

4.2

5.1

5.9

4.2

5.3

4.9

5.2

5.7

3.2

4.8

6.2

7.2

11.3 (Cl)

9.9 (Cl)

8.9 (Cl)

8.4 (Cl)

7.6 (Cl)

7.0 (Cl)

7.0 (S)

12.0 (Cl)

9.8 (Cl)

8.7 (Cl)

8.1 (Cl)

7.25 (Cl)

7.2 (S)

[RuCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]^b

[RuCl(O,O′-acac)(η⁶-C₆Me₆)]^c

[RuCl(O,O′-hfacac)(η⁶-C₆H₆)]

[RuCl(O,O′-hfacac)(η⁶-1,3,5-C₆H₃Me₃)]

[RuCl(O,O′-hfacac)(η⁶-C₆Me₆)]

[Ru(O,O′-acac)(dmso)(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(dmso)(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(dmso)(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(MeCN)(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(MeCN)(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(py)(η⁶-C₆H₆)]BF₄

6.6 (S)

6.1 (S)

6.3 (S)

5.7 (S)

3.45 (N)

2.9 (N)

3.15 (N)

2.9 (N)

2.65 (N)

3.0 (N)

2.8 (N)

3.0 (N)

2.9 (N)

2.5 (N)

[Ru(O,O′-acac)(py)(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(py)(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(CO)(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(CO)(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(PPh₃)(η⁶-C₆H₆)]BF₄

[Ru(O,O′-acac)(PPh₃)(η⁶-1,3,5-C₆H₃Me₃)]BF₄

[Ru(O,O′-acac)(PPh₃)(η⁶-C₆Me₆)]BF₄

[Ru(O,O′-acac)(η⁶-C₆H₆)]_n(BF₄)_n

[Ru(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]_n(BF₄)_n

[Ru(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)]

[Ru(O,O′-acac)(η¹-O-acac)(η⁶-C₆Me₆)]^d

^aMW calcd.: 315; found: 300 (osmometry in CH₂Cl₂).

^bMW calcd.: 356; found: 364 (osmometry in CH₂Cl₂).

^c%Ru calcd.: 25.4; found: 25.4. MW calcd.: 398; found: 392 (osmometry in CH₂Cl₂).

^d%Ru calcd.: 21.9; found: 21.8. MW calcd.: 461; found: 407.

1

prepared similarly from [RuCl(η⁶-1,3,5-C₆H₃Me₃)]₂and

Tl(hfacac).

(m, 2H) (py). Arene = 1,3,5-C₆H₃Me₃: H NMR (CDCl₃) δ:

7.49 (m, 2H), 7.87 (m, 1H), 8.50 (m, 2H) (py). Arene =

C₆Me₆: H NMR (CDCl₃) δ: 7.52 (m, 2H), 7.88 (m, 1H),

1

(ii) A solution of [RuCl₂(η⁶-C₆Me₆)]₂(150 mg, 0.22 mmol)

in dichloromethane (15 mL) was stirred for 1 min with

Tl(hfacac) (185mg, 0.45 mmol) at room temperature and

then filtered. The filtrate was evaporated to ca. half the vol-

ume and ether was added to give [RuCl(O,O′-hfacac)(η⁶-

C₆Me₆)] as a red crystalline solid. The yield was 143 mg

(63%).

8.14 (m, 2H) (py).

[Ru(O,O′-acac)(η⁶-arene)(CO]BF₄

A solution of AgBF₄(55 mg, 0.28 mmol) in acetone

(15 mL) was saturated with CO and treated with

[RuCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)] (100 mg, 0.28 mmol).

The solution was stirred for 5 min while CO was bubbled

into it, then filtered, and evaporated under reduced pressure

to ca. 5 mL volume. Addition of ether caused the product,

[RuCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)(CO)]BF₄, to form as a

yellow microcrystalline solid, which was separated by filtra-

tion, washed with ether, and dried in vacuo. The yield was

50 mg (41%). IR (KBr, cm^–1): 2045 (vs) (CO). A similar

procedure was used to prepare [RuCl(O,O′-acac)(η⁶-

C₆Me₆)(CO)]BF₄from [RuCl(O,O′-acac)(η⁶-C₆Me₆)]. Evap-

oration to dryness of the filtered acetone solution gave an

oil, which was dissolved in the minimum volume of di-

chloromethane. Addition of ether gave the product as a pale

yellow solid in 45% yield. IR (KBr, cm^–1): 2026 (vs) (CO).

[Ru(O,O′-acac)(η⁶-arene)(L)]BF₄(L = DMSO, MeCN, py,

PPh₃)

Equimolar quantities of [RuCl(O,O′-acac)(η⁶-arene)] and

AgBF₄were stirred in acetone at room temperature for

5 min. The solution was filtered through Celite™, the filtrate

was treated with an equimolar quantity of ligand L, and the

solution stirred for 1 h. Evaporation to ca. half the volume

and addition of ether gave the products as yellow micro-

crystalline solids, which could be recrystallized from

dichloromethane–ether. Yields were 40–80%. L = DMSO:

1

arene = C₆H₆: IR (KBr, cm^–1): 1124 (s) (S=O). H NMR

(CDCl₃) δ: 2.66 (s, Me₂SO). Arene = 1,3,5-C₆H₃Me₃: IR

1

(KBr, cm^–1): 1123 (s) (S=O). H NMR (CDCl₃) δ: 2.64 (s,

Me₂SO). Arene = C₆Me₆: IR (KBr, cm^–1): 1124 (s) (S=O).

¹H NMR (CDCl₃) δ: 2.57 (s, Me₂SO). L = MeCN: arene =

[Ru(acac)(arene)]_n(BF₄)_n

To a solution of AgBF₄(64 mg, 0.33 mmol) in acetone

(15 mL) was added [RuCl(O,O′-acac)(η⁶-C₆H₆)] (100 mg,

0.32 mmol). The mixture was stirred for 15 min and filtered.

Evaporation of the filtrate to ca. 5 mL volume and addition

of ether gave [Ru(acac)(η⁶-C₆H₆)]_n(BF₄)_nas a pale yellow

1

C₆H₆: IR (KBr, cm^–1): 2295 (w) (CN). H NMR (CD₂Cl₂) δ:

2.32 (s, MeCN). Arene = C₆Me₆: IR (KBr, cm^–1): 2290 (w)

1

(CN). H NMR (CDCl₃) δ: 2.42 (s, MeCN). L = py: arene =

1

C₆H₆: H NMR (CDCl₃) δ: 7.44 (m, 2H), 7.84 (m, 1H), 8.47

Bennett et al.

Table 8. Elemental analyses for Os(acac)(η⁶-arene) complexes.

665

%C

%H

Complex

Calcd.

Found

Calcd.

Found

[OsCl(O,O′-acac)(η⁶-C₆H₆)]

32.8

36.2

37.8

41.9

36.6

39.6

41.0

44.7

41.2

43.7

44.9

48.0

32.0

36.0

37.5

38.1

42.5

37.2

40.3

40.4

40.6

44.6

40.8

43.3

43.9

43.1

46.7

3.2

4.0

4.3

5.2

3.8

4.4

4.7

5.5

4.3

4.9

5.15

5.9

3.2

3.9

3.95

4.5

5.6

4.4

4.7

5.1

5.0

5.4

4.1

4.7

4.9

5.7

[OsCl(O,O′-acac)(η⁶-1,2-C₆H₄Me₂)]^a

[OsCl(O,O′-acac)(η⁶-1,2,3-C₆H₃Me₃)]

[OsCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]

[OsCl(O,O′-acac)(η⁶-C₆Me₆)]

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-C₆H₆)]

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-1,2-C₆H₄Me₂)]

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-1,2,3-C₆H₃Me₃)]

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-C₆Me₆)]

[Os(O,O′-acac)(η¹-C-acac)(η⁶-C₆H₆)]

[Os(O,O′-acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)]

[Os(O,O′-acac)(η¹-C-acac)(η⁶-1,2,3-C₆H₃Me₃)]

[Os(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)]

[Os(O,O′-acac)(η¹-O-acac)(η⁶-C₆Me₆)]

^a%Cl calcd.: 8.2; found: 8.2.

powder, which was separated by filtration and washed with

ether. The yield was 30 mg (26%). IR (KBr, cm^–1): 1620

(vs) (C=O)–(C=C). The mesitylene analogue was prepared

similarly in 31% yield. IR (KBr, cm^–1): 1620 (vs) (C=O),

(C=C).

(ii) The benzene complex can be made from [OsCl₂(η⁶-

C₆H₆)]₂and Na(acac) as described for the ruthenium ana-

logue (1(ii)) or as follows.

Addition of a few drops of acetyl chloride to a solution of

[Os(O,O′-acac)(η¹-C-arene) (η⁶-C₆H₆)](125 mg, 0.27 mmol)

(see below) in methanol (4 mL) caused a precipitate to form

immediately. The solvent was removed in vacuo and the res-

idue was extracted with dichloromethane. The extract was

filtered through Celite™, concentrated under reduced pres-

sure, and cooled to give [OsCl(O,O′-acac)(η⁶-C₆H₆)]

(73 mg, 67%) in two crops.

[Ru(O,O′-acac)(CO)(MeCN)₃]BF₄

Carbon monoxide was bubbled into a solution of [Ru(O,O′-

acac)(η⁶-C₆H₆) (MeCN)] BF₄(100 mg, 0.24 mmol) in ace-

tone (15 mL) for 5 min. The solution was filtered and the fil-

trate evaporated under reduced pressure to give a brown oil.

This was dissolved in acetonitrile and to the filtered solution

was added ether dropwise to precipitate [Ru(O,O′-

acac)(CO)(MeCN)₃]BF₄(20mg, 18%) as a pale yellow solid.

IR(KBr, cm^–1): 2300 (vw) (CN), 1980 (vs) (CO), 1570 (vs)

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-arene)]

A suspension of [OsCl(O,O′-acac)(η⁶-C₆H₆)] (48 mg,

0.12 mmol) and silver acetate (21 mg, 0.13 mmol) in ben-

zene (10 mL) was stirred overnight. The yellow solution was

separated by decantation from the precipitated AgCl, filtered

through Celite™, and evaporated to dryness. The resulting

yellow solid [Os(η¹-O₂CMe)(O,O′-acac)(η⁶-C₆H₆)] (47 mg,

92%) was spectroscopically and analytically pure.

1

(C=O), (C=C) of acac. H NMR (CDCl₃) δ: 2.00 (s, 6H,

acac-CH₃), 2.51 (s, 3H), 2.54 (s, 6H, MeCN), 5.31 (s, 1H,

acac-γ-CH). Anal. calcd. for C₁₂H₁₆BF₄N₃O₃Ru: C 32.9, H

3.8, N 9.6; found: C 32.9, H 3.7, N 9.6.

[OsCl(O,O′-acac)(η⁶-arene)]

The corresponding complexes containing 1,2-C₆H₄Me₂,

1,2,3-C₆H₃Me₃, 1,3,5-C₆H₃Me₃, and C₆Me₆were prepared

similarly in yields of 71, 95, 59, and 95%, respectively.

(i) A mixture of [OsCl₂(η⁶-1,3,5-C₆H₃Me₃)]₂(200 mg,

0.26 mmol) and Tl(acac) (160 mg, 0.53 mmol) was stirred in

dichloromethane (10 mL) for 2 h at room temperature. The

yellow solution was separated from the precipitated TlCl by

decantation and filtered through Celite™. The solution was

concentrated in vacuo and ether was added. Cooling in dry

ice – acetone gave [OsCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)] as

a yellow-brown solid (176 mg, 75%). Evaporation of the

supernatant liquid gave more yellow-brown solid, which was

[Ru(acac)₂(η⁶-arene)]

A mixture of [RuCl(O,O′-acac)(η⁶-C₆H₆)] (200 mg,

0.64 mmol) and Tl(acac) (190 mg, 0.63 mmol) was stirred in

methanol (10 mL) at –20°C for 2 h. The solution was evapo-

rated to dryness, the residue was extracted with ether, and

the extract was filtered, the temperature being kept below

0°C at all times. The filtrate was concentrated under reduced

pressure to give [Ru(O,O′-acac)(η¹-C-acac)(η⁶-C₆H₆)] as a

microcrystalline red solid, which darkened when warmed to

room temperature. The yield was 120 mg (51%).

1

shown by H NMR spectroscopy to be an approximately 1:1

mixture of [OsCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)] and the

acetato

complex

[Os(η¹-O₂CMe)(O,O′-acac)(η⁶-1,3,5-

C₆H₃Me₃)].

The complexes [OsCl(O,O′-acac)(η⁶-arene)] (arene = 1,2-

C₆H₄Me₂, 1,2,3-C₆H₃Me₃, and C₆Me₆) were prepared simi-

larly from the corresponding [OsCl₂(η⁶-arene)]₂complexes

in yields of 83, 74, and 73%, respectively.

The complexes [Ru(O,O′-acac)(η¹-O-acac)(η⁶-arene)]

(arene = 1,3,5-C₆H₃Me₃, C₆Me₆) were prepared similarly

from [RuCl(O,O′-acac)(η⁶-arene)] in yields of 40 and 60%,

respectively.

666

Can. J. Chem. Vol. 79, 2001

Table 9. Crystallographic data collection parameters for (η⁶-arene)osmium complexes.

[Os(O,O′-acac)(η¹-C-acac)

(η⁶-1,2-C₆H₄Me₂)]

[Os(O,O′-acac)

[Os(η¹-OAc)(O,O′-acac)

(η⁶-C₆H₆)]

Complex

(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)]

Formula

FW

C₁₈H₂₄O₄Os

494.59

C₁₉H₂₆O₄Os

508.61

C₁₃H₁₆O₄Os

426.47

Crystal system

Space group

a (Å)

b (Å)

c (Å)

Triclinic

P1 (No. 2)

9.922(2)

9.974(2)

11.001(2)

68.33(1)

Monoclinic

C2/c (No. 15)

16.032(4)

11.989(3)

21.562(7)

Triclinic

P1 (No. 2)

8.368(4)

8.402(4)

11.008(4)

71.68(3)

α (°)

β (°)

64.18(1)

108.91(2)

69.35(3)

γ (°)

V (Å³)

62.38 (1)

849.0(3)

69.77(3)

663.0(6)

3921(2)

Z

2

8

2

ρ_calcd.(g cm^–3)

Crystal size (mm)

Temperature (K)

F (000)

1.935

0.38 × 0.37 × 0.08

296 ± 1

1.723

0.25 × 0.20 × 0.17

296 ± 1

2.133

0.40 × 0.23 × 0.04

296 ± 1

480.00

1984.00

404.00

Colour, habit

µ (cm^–1)

Yellow, plate

75.22 (Mo Kα)

Philips PW 1100/20

ω–2θ

1.20 + 0.35 tan θ

60.0

4949

4508

0.104–0.578

281

1.73, –1.17

Yellow, multifaceted

65.18 (Mo Kα)

Philips PW 1100/20

ω–2θ

1.0 + 0.35 tan θ

55.0

4721

2717

0.318–0.436

217

0.56, –1.63

Orange, wedge

96.01 (Mo Kα)

Philips PW 1100/20

ω–2θ

1.20 + 0.34 tan θ

55.2

3064

2738

0.127–0.582

164

0.85, –0.72

Diffractometer

Data collection method

ω–Scan width (°)

2θ limits (°)

Total unique reflections

Total observed reflections^a

Max/min transmission factor^b

No. of parameters

Largest difference peak and

hole (e Å^–3)

R^c

0.023

0.026

1.54

0.032

0.034

1.53

0.023

0.027

1.50

c

R_w

GoF^d

^aI > 3σ (I).

^bAnalytical absorption correction.

^cR = Σ||F_o| – |F_c||/ Σ|F_o|; R_w= [Σ{w(|F_o| – |F_c|)}/ Σ(w|F_o|)²]^1/2

.

^d{Σw(|F_ο| – |F_c|)²/(N_o-N_v)}^1/2, where N_o= number of observations, N_v= number of variables.

[Os(acac)₂(η⁶-arene)]

tion and a colourless precipitate. The methanol was removed

in vacuo and the residue was extracted with ether and fil-

tered through Celite™. Concentration of the filtrate and

cooling gave a yellow solid containing mainly [Os(O,O′-

(i) A mixture of [OsCl₂(η⁶-C₆H₆)]₂(100 mg, 0.15 mmol)

and Tl(acac) (179 mg, 0.59 mmol) in methanol (10 mL) was

stirred for 2 h. The solvent was removed under reduced pres-

sure and the residue was extracted with dichloromethane.

The extracts were filtered through Celite™ and again evapo-

rated to dryness. The residue was extracted with ether (ca.

20 mL) and the ether solution passed down a short column

of Celite™. Concentration and cooling gave two crops

(34 mg in total) of a yellow solid containing [Os(O,O′-

acac)(η¹-C-acac)(η⁶-C₆H₆)] contaminated by the acetato

complex [Os(η¹-O₂CMe)(O,O′-acac)(η⁶-C₆H₆)] (ca. 10–

1

acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)], as shown by H NMR

spectroscopy. The yield was 82 mg (55%). Evaporation of

the supernatant liquid gave a further 34 mg of less pure

product. Yellow-brown X-ray quality crystals of [Os(O,O′-

acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)] were obtained by diffu-

sion of hexane into a benzene solution of the first solid;

these crystals also gave satisfactory microanalytical data. EI-

MS (70 eV) m/z : 496.1 (M⁺, based on ¹⁹²Os), 397 ([M – acac]⁺).

1

15%) as shown by H NMR spectroscopy. An X-ray quality

(iii) Similarly prepared from OsCl(O,O′-acac)(η⁶-1,2,3-

C₆H₃Me₃)] (123 mg, 0.28 mmol) and Tl(acac) (85 mg,

0.28 mmol) in methanol, after extraction with dichloro-

methane (10 mL), was crude [Os(O,O′-acac)(η¹-C-acac)(η⁶-

1,2,3-C₆H₃Me₃)] (127 mg, 89%). Purification was carried

out by extraction with ether as described above.

crystal of the latter was obtained by evaporation of the ether

solution. A crystalline, spectroscopically and analytically pure

sample of [Os(O,O′-acac)(η¹-C-acac)(η⁶-C₆H₆)] was obtained

by diffusion of pentane into a dichloromethane solution.

(ii) A mixture of [OsCl(O,O′-acac)(η⁶-1,2-C₆H₄Me₂)]

(130 mg, 0.30 mmol) and Tl(acac) (95 mg, 0.31 mmol) in

methanol (10 mL) was stirred for 2 h giving a yellow solu-

(iv) Reaction of [OsCl(O,O′-acac)(η⁶-1,3,5-C₆H₃Me₃)]

(150 mg, 0.34 mmol) with Tl(acac) (103 mg, 0.34 mmol) in

Bennett et al.

667

Table 10. Positional parameters and isotropic thermal parameters

for non-hydrogen atoms of [Os(O,O′-acac)(η¹-C-acac)(η⁶-1,2-

C₆H₄Me₂)].

Table 11. Positional parameters and isotropic thermal parameters

for non-hydrogen atoms of [Os(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-

C₆H₃Me₃)].

a

Atom

x

y

z

B_eq

Atom

x

y

z

B_eq

Os(1)

O(1)

O(2)

O(3)

O(4)

C(1)

C(2)

C(3)

C(4)

C(5)

C(6)

C(7)

C(8)

C(9)

C(10)

C(11)

C(12)

C(13)

C(14)

C(15)

C(16)

C(17)

C(18)

0.18151(1)

0.0834(2)

0.2262(2)

0.3610(3)

0.6139(3)

0.0263(4)

0.0971(3)

0.1658(4)

0.2185(3)

0.2720(4)

0.4659(5)

0.4089(4)

0.4134(3)

0.5454(4)

0.5934(4)

0.0695(4)

0.2231(4)

0.2572(4)

0.1433(5)

0.29901(1)

0.5387(2)

0.3002(2)

0.5716(3)

0.0977(3)

0.7945(3)

0.6232(3)

0.5690(3)

0.4161(3)

0.3779(4)

0.3523(5)

0.4306(4)

0.3380(3)

0.1867(4)

0.1407(4)

0.1278(3)

0.0511(3)

0.1076(4)

0.2344(4)

0.3093(4)

0.2542(4)

0.0780(5)

0.29616(1)

0.2434(2)

0.0929(2)

0.2550(3)

0.2733(3)

0.1137(4)

0.1205(3)

–0.0004(3)

–0.0087(3)

–0.1467(3)

0.4125(5)

0.2879(4)

0.2066(3)

0.1873(4)

0.0553(4)

0.3566(3)

0.3749(3)

0.4562(3)

0.5184(3)

0.4961(3)

0.4196(4)

0.2650(4)

0.3089(4)

2.147(2)

2.66(4)

2.58(3)

4.90(7)

5.25(6)

3.79(7)

2.53(4)

3.10(5)

2.60(5)

3.46(6)

5.3(1)

3.66(6)

2.93(5)

3.59(6)

4.40(7)

3.20(6)

2.99(5)

3.21(6)

3.59(6)

3.81(6)

3.50(6)

4.8(1)

Os(1)

O(1)

O(2)

O(3)

O(4)

C(1)

C(2)

C(3)

C(4)

C(5)

0.19613(2)

0.1366(4)

0.3051(3)

0.1456(3)

0.2731(5)

0.1030(6)

0.1626(6)

0.2398(6)

0.3048(6)

0.3877(6)

0.1229(6)

0.1809(6)

0.2600(6)

0.3027(6)

0.3951(7)

0.1396(5)

0.2331(6)

0.2842(6)

0.2417(6)

0.1507(6)

0.0976(6)

0.0858(6)

0.3836(6)

0.1055(7)

–0.00494(3)

0.1412(4)

0.0912(4)

0.0597(4)

0.0444(5)

0.3303(7)

0.2405(7)

0.2700(7)

0.1972(7)

0.2402(8)

0.1159(9)

0.0591(6)

0.0126(7)

0.0113(8)

–0.037(1)

–0.0884(6)

–0.0928(6)

–0.1326(6)

–0.1736(6)

–0.1695(6)

–0.1284(6)

–0.0386(8)

–0.1249(8)

–0.2042(8)

0.07174(1)

0.0270(3)

0.1204(3)

0.1427(3)

0.3525(3)

0.0065(4)

0.0447(4)

0.0949(5)

0.1282(4)

0.1782(5)

0.2389(5)

0.2062(4)

0.2407(4)

0.3100(4)

0.3333(5)

–0.0222(4)

0.0035(4)

0.0573(4)

0.1006(4)

0.0859(4)

0.0219(5)

–0.0861(4)

0.0787(5)

0.1340(5)

3.272(6)

3.7(1)

3.9(1)

3.8(1)

6.3(2)

5.1(2)

4.2(2)

4.7(2)

4.1(2)

5.8(3)

6.1(3)

3.9(2)

4.5(2)

4.9(2)

7.3(3)

3.7(2)

4.0(2)

4.2(2)

4.4(2)

4.2(2)

5.5(2)

5.7(3)

6.0(3)

C(6)

C(7)

C(8)

C(9)

C(10)

C(11)

C(12)

C(13)

C(14)

C(15)

C(16)

C(17)

C(18)

C(19)

–0.0062(4)

–0.0450(4)

0.0315(6)

0.3515(5)

–0.0832(4)

4.65(8)

^aB_eq= 8π²/3{U₁₁(aa^*)²+ U₂₂(bb^*)²+ U₃₃(cc^*)²+ 2U₁₂aa^*bb^*cos γ +

2U₁₃aa^*cc^*cos β + 2U₂₃bb^*cc^*cos α}.

^aB_eqdefined as in Table 10.

methanol (10 mL) and work-up as described for the o-xylene

preparation gave 150 mg (88%) of crude [Os(O,O′-acac)(η¹-

O-acac)(η⁶-1,3,5-C₆H₃Me₃)] contaminated with the acetato

complex. Yellow X-ray quality crystals of the former were

obtained by diffusion of hexane into a benzene solution.

(v) Reaction of [OsCl(O,O′-acac)(η⁶-C₆Me₆)] (94 mg,

0.19 mmol) with Tl(acac) (60 mg, 0.20 mmol) in methanol

(10 mL) and work-up as described above gave [Os(O,O′-

acac)(η¹-O-acac)(η⁶-C₆Me₆)] (38 mg, 36%), which was ca.

Table 12. Positional parameters and isotropic thermal parameters

for non-hydrogen atoms of [Os(O,O′-acac)(η¹-O₂CMe)(η⁶-C₆H₆)].

a

Atom

x

y

z

B_eq

Os(1)

O(1)

O(2)

O(3)

O(4)

C(1)

C(2)

C(3)

C(4)

C(5)

C(6)

C(7)

C(8)

C(9)

C(10)

C(11)

C(12)

C(13)

0.18666(2)

0.08777(2)

0.2837(4)

0.2798(4)

0.1704(5)

0.0402(6)

0.5568(8)

0.4477(6)

0.5251(7)

0.4433(6)

0.5496(8)

0.1353(7)

0.2229(9)

–0.086(1)

–0.0307(9)

–0.0470(9)

–0.127(1)

–0.1789(8)

–0.1610(9)

0.23193(2)

0.3121(4)

0.0746(3)

0.3257(4)

0.2379(5)

0.3596(7)

0.2725(6)

0.1585(6)

0.0651(5)

–0.0612(6)

0.3078(5)

0.3847(6)

0.326(1)

0.197(1)

0.0991(7)

0.139(1)

0.275(1)

0.3631(8)

2.743(4)

3.53(7)

3.61(7)

3.77(8)

5.2(1)

5.7(2)

3.8(1)

4.8(1)

3.9(1)

5.3(1)

3.5(1)

4.9(2)

7.3(2)

6.4(2)

7.4(2)

7.7(2)

6.6(2)

7.6(3)

–0.0167(4)

0.2701(5)

0.3100(5)

0.5922(5)

–0.1831(9)

–0.0321(7)

0.0726(9)

0.2120(8)

0.2991(9)

0.4775(7)

0.5256(8)

0.022(1)

1

90% pure, although H NMR spectroscopy and elemental

analyses indicated the presence of some of the acetato com-

plex.

Molecular structure determinations

Crystals of [Os(O,O′-acac)(η¹-C-acac)(η⁶-1,2-C₆H₄Me₂)]

and [Os(O,O′-acac)(η¹-O-acac)(η⁶-1,3,5-C₆H₃Me₃)] suitable

for X-ray diffraction studies were obtained by vapour diffu-

sion of hexane into benzene solutions. Crystals of [Os(O,O′-

acac)(η¹-OAc)(η⁶-C₆H₆)] were obtained fortuitously from an

ether solution of the crude η¹-C-acac complex. The crystal

data and parameters for data collection are summarized in

Table 9. The structures were solved by heavy atom Patterson

methods (36) and expanded by use of Fourier techniques

(37). Non-hydrogen atoms were refined anisotropically.

Most of the hydrogen atoms were located in the difference

electron density maps and the positions used to generate all

the hydrogen atoms, assuming idealized geometry. For the o-

xylene complex, the positional parameters for the hydrogen

atoms were refined, the isotropic B-values being held fixed

0.024(1)

0.183(2)

0.346(1)

0.327(1)

0.171(2)

^aB_eqdefined as in Table 10.

and tight restraints being imposed on distances and angles for

the methyl groups only. For the mesitylene and benzene com-

plexes, the hydrogen atoms were periodically recalculated but

668

Can. J. Chem. Vol. 79, 2001

not refined. The function minimized was Σw(|F_o| – |F_c|)²

with the weights w given by w = |σ²(F_o)|^–1. The software

packages used were Xtal (38) for data reduction and teXsan

(39) for structure solution, refinement, and graphics. Neutral

atom scattering factors were taken from ref. 40. Anomalous

dispersion effects were included in F_calc(41); values of ∆f ′

and ∆f ′′ and of mass attenuation coefficients were taken

from standard compilations (42, 43). Selected bond dis-

tances and angles are given in Tables 4–6, atomic coordi-

nates are listed in Tables 10–12.

9. M. Kilner, F.A. Hartman, and A. Wojcicki. Inorg. Chem. 6,

406 (1967).

10. (a) K. Nakamoto. Infrared and Raman spectra of inorganic and

coordination compounds. 5th ed. Part B. Wiley Interscience,

New York. 1997. pp. 102–104; (b) pp. 59–62.

11. J. March. Advanced organic chemistry. 4th ed. Wiley Inter-

science, New York. 1992. p. 631.

12. S.I. Yoshida, Y. Ohgomori, Y. Watanabe, K. Honda, M. Goto,

and M. Kurabashi. J. Chem. Soc. Dalton Trans. 895 (1988).

13. T. Ito, T. Kiriyama, and A. Yamamoto. Chem. Lett. 835 (1976).

14. S. Okeya, F. Egawa, Y. Nakamura, and S. Kawaguchi. Inorg.

Chim. Acta, 30, L 319 (1978).

Crystal data, complete tables of bond distances and an-

gles, atomic coordinates, anisotropic thermal parameters for

the non-hydrogen atoms, non-bonded contacts, and selected

least-squares planes have been deposited.²

15. B. Bock, K. Flatau, H. Junge, M. Kuhr, and H. Musso. Angew.

Chem. Int. Ed. Engl. 10, 225 (1971).

16. N. Yanase, Y. Nakamura, and S. Kawaguchi. Inorg. Chem. 19,

1575 (1980).

17. S. Okeya, Y. Nakamura, S. Kawaguchi, and T. Hinimoto. Bull.

Chem. Soc. Jpn. 55, 477 (1982).

Conclusion

18. E. Lindner, R.M. Jansen, W. Hiller, and R. Fawzi. Chem. Ber.

122, 1403 (1989).

19. W.A. Kiel, R.G. Ball, and W.A.G. Graham. J. Organomet.

Chem. 383, 481 (1990).

20. M.A. Esteruelas, F.J. Lahoz, J.A. Lopez, L.A. Oro, C.

Schlünken, C. Valero, and H. Werner. Organometallics, 11,

2034 (1992).

21. G. Bellachioma, G. Cardaci, A. Macchioni, and P. Zanazzi.

Inorg. Chem. 32, 547 (1993).

22. G.B. Ansell, S. Leta, A.A. Oswald, and E.J. Mozeleski. Acta

Crystallogr. Sect. C: Cryst. Struct. Commun. 42, 1516 (1986).

23. J. von Seyerl, D. Neugebauer, G. Huttner, C. Krüger, and Y-H.

Tsay. Chem. Ber. 112, 3637 (1979).

24. G. Huttner, J. von Seyerl, and D. Neugebauer. Cryst. Struct.

Commun. 9, 1093 (1980).

25. S. Ooi, T. Matsushita, K. Nishimoto, S. Okeya, Y. Nakamura,

and S. Kawaguchi. Bull. Chem. Soc. Jpn. 56, 3297 (1983).

26. P.M. Maitlis. Chem. Soc. Rev. 10, 1 (1981).

27. M.A. Bennett and A.K. Smith. J. Chem. Soc. Dalton Trans.

233 (1974).

In this work, we have shown that the [M(O,O′-acac)(η⁶-

arene)] (M = Ru, Os) fragments are capable of binding a

range of ligands containing nitrogen, phosphorus, oxygen,

and sulfur donor atoms. The mode of binding of a second

acac group depends on the nature of the arene. The fact that

the preferred binding mode changes from η¹-C to η¹-O in

going from 1,2,3- to 1,3,5-C₆H₃Me₃suggests that there is a

delicate balance, possibly mediated by a steric effect. The

more symmetrical arrangement of ring methyl groups could

give rise to an unavoidable steric repulsion between them

and the COCH₃groups of a η¹-C-acac group, thus favouring

coordination of the sterically less demanding η¹-O- enolate

form. However, on this basis alone, it is difficult to see why

η¹-C-bonding should be favoured for the isoelectronic com-

plexes of rhodium(III) and iridium(III) [M(O,O′-acac)(η¹-C-

acac)(η⁵-C₅Me₅)] (4), since the estimated average cone an-

gles of Rh^III-C₅Me₅and Ru^II-C₆H₃Me₃are likely to be very

similar (ca. 188°) (26). Another possibility is that, since the

charge separation in an arene–metal bond in the sense

(arene)(δ⁺)–metal(δ^–) is probably greater than that in its

isoelectronic C₅Me₅–metal counterpart, the negative charge

on the metal may be better accommodated by the more

electronegative oxygen atom of an O-bound enolate.

28. M.A. Bennett and A.M.M. Weerasuria. J. Organomet. Chem.

394, 481 (1990).

29. M.A. Bennett, M. Bown, L.Y. Goh, D.C.R. Hockless, and T.R.B.

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30. M.A. Bennett, T.N. Huang, T.W. Matheson, and A.K. Smith.

Inorg. Synth. 21, 74 (1982).

31. M. Bown, X.L.R. Fontaine, N.N. Greenwood, and J.D. Ken-

nedy. J. Organomet. Chem. 325, 233 (1987).

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List of Abbreviations

acac = acetylacetonate, 2,4-pentanedionato, CH₃COCHCOCH₃;

tfacac = trifluoroacetylacetonato, 1,1,1-trifluoro-2,4-pentane-

dionato, CF₃COCHCOCH₃; hfacac = hexafluoroacetylace-

tonato, 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato,

CF₃COCHCOCF₃; cym = p-cymene, 1,4-MeC₆H₄CHMe₂;

DMSO = dimethylsulfoxide; py = pyridine.

Article Doi

Mono- and bis-(acetylacetonato) complexes of arene-ruthenium(II) and arene-osmium(II): Variation of the binding mode of η1-acetylacetonate with the nature of the arene

DOI: 10.1139/v01-076

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