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Inorganica Chimica Acta 361 (2008) 3159–3164

Rh and Ir dibenzo[a,e]cyclooctatetraene complexes: Chloro,hydroxo, and mixed Au oxo complexes

Anupam Singh, Paul R. Sharp *

125 Chemistry, University of Missouri, Columbia, MO 65211, United States

Received 29 October 2007; accepted 2 December 2007Available online 14 December 2007

Dedicated to Robert J. Angelici.

Abstract

New and improved procedures are reported for the synthesis of [M(DBCOT)(l-Cl)]2 (M = Rh, Ir; DBCOT = dibenzo[a,e]cycloocta-tetraene) from MCl3(H2O)x or [M(COD)(l-Cl)]2 and DBCOT. Treatment of [M(DBCOT)(l-Cl)]2 with [(LAu)3(l-O)]BF4(L = PPh3,PtBu3) yields the mixed-metal oxo complexes [M(DBCOT)(l4-O)(AuL)2]2(BF4)2. Dimeric [Rh(DBCOT)(l-OH)]2 is obtained from thereaction of [M(DBCOT)(l-Cl)]2 with KOH in EtOH/H2O. All complexes except [Rh(DBCOT)(l-Cl)]2 have been structurally character-ized by single crystal X-ray diffraction.� 2007 Elsevier B.V. All rights reserved.

Keywords: Rhodium complexes; Iridium complexes; Diene; Oxo; Hydroxo; Chloro; Synthesis; X-ray crystal structures

1. Introduction

The chelating diene ligand dibenzo[a,e]cyclooctatetraene(DBCOT, Scheme 1) resembles the well-known and highlyutilized ligand 1,5-cyclooctadiene (COD) but has signifi-cantly different properties. DBCOT bonds more stronglyto some metal centers but more weakly to others and is aweaker donor ligand than COD giving more electrophilicmetal complexes [1,2]. It is also known for its resistanceto hydrogenation and this has lead to the use of DBCOTas a poison for homogeneous catalysts [3]. A recent reportof an improved DBCOT synthesis [4] and a facile prepara-tion of substituted DBCOT’s [5] makes this dialkene ligandparticularly attractive for investigation. Our previous work[2] on Pt(II) chemistry of DBCOT revealed different chem-istry from that of COD and we were interested in alsoexamining the differences in the analogous Rh(I) and Ir(I)

0020-1693/$ - see front matter � 2007 Elsevier B.V. All rights reserved.

doi:10.1016/j.ica.2007.12.007

* Corresponding author.E-mail address: sharpp@missouri.edu (P.R. Sharp).

DBCOT and COD chemistry. These results are reportedbelow.

2. Results and discussion

2.1. Chloro complexes

The original synthesis of [M(DBCOT)(l-Cl)]2 (1, M =Rh, Ir) [1] calls for DBCOT addition to CH2Cl2 solutionsof [M(COT)(l-Cl)]2. We find that this procedure is sensi-tive to the reaction time. For short reaction times(a few minutes) the isolated material is contaminated withthe mixed COD/DBCOT dimer M(DBCOT)(l-Cl)2M-(COD) [2]. With longer reaction times (20–30 min) highyields of pure yellow 1 are isolated (Scheme 1). While thisis a convenient synthesis of 1 a more direct preparationfrom the metal salts was sought. In analogy to the synthe-ses of [M(COD)(l-Cl)]2 [6–8] simply refluxing a mixture ofMCl3 � (H2O)x and DBCOT in EtOH/H2O gives excellentyields (>90%) of 1 (Scheme 1).

1H NMR spectra for 1 in CD2Cl2 are essentially identi-cal to those previously reported in CDCl3 [1]. For the Rh

[M(COD)(μ-Cl)]2

M

1 (M = Rh, Ir)

MCl

Cl

MCl3(H2O)x EtOH/H2O

CH2Cl2

reflux

DBCOT =

DBCOT+

DBCOT+

Scheme 1.

3160 A. Singh, P.R. Sharp / Inorganica Chimica Acta 361 (2008) 3159–3164

derivative, a broad singlet is observed at 6.97 ppm for thearomatic protons and the olefinic protons appear as a dou-blet at 5.09 ppm (JRh–H = 2.2 Hz). The Ir complex shows acomplex pattern from 7.03 to 6.86 ppm for the aromaticprotons and a singlet at 5.35 ppm for the olefinic protons.Layering the CD2Cl2 NMR sample with Et2O and storingthe mixture at �30 �C gave crystals of the Ir complex suit-able for X-ray diffraction. A drawing of the solid-statestructure is shown in Fig. 1. Crystal data and data collec-tion and processing parameters are listed in Table 1.Selected distances and angles are given in Table 2. Overall,the dimeric structure is as expected. The structure of theCOD analog, [Ir(COD)(l-Cl)]2, has been determined andis known in both orthorhombic and monoclinic poly-morphs [9–11]. An obvious difference between the struc-tures of [Ir(COD)(l-Cl)]2 and 1 (M = Ir) is that in[Ir(COD)(l-Cl)]2 the edge-shared Ir coordination planesare not coincident as they are in 1 (M = Ir). Instead, theyare folded at the Cl–Cl axis. A dihedral angle of 71� isobserved between the two Ir,Cl,Cl planes [9]. Such foldingin edge-shared d8-dimers of formula L2M(l-X)2ML2 hasbeen previously examined and is promoted by morestrongly donating ancillary ligands L [12,13]. This is consis-tent with the weaker donor properties of DBCOT overCOD [1,2] but the energy difference between folded andplanar structures is thought to be small and closely relatedcomplexes have been observed in both folded and planarforms. Thus, drawing a conclusion about a difference in

Fig. 1. Drawing of the solid-state structure of 1 (M = Ir). Atoms ar

the donor properties of COD and DBCOT based on thisstructural difference is probably not warranted. Becauseof the fold in 1 the Ir–Ir distance and the Ir–Cl–Ir angle dif-fer significantly between the two structures. Other thanthat, the metrical parameters of the COD and DBCOTstructures match closely with essentially identical meanIr–Cl and Ir–C distances and Cl–Ir–Cl angles.

2.2. Oxo and hydroxo complexes

Complexes 1 react smoothly with [(Ph3PAu)3(l-O)]BF4

to give yellow to orange dimeric mixed-metal oxo com-plexes [M(DBCOT)(l4-O)(AuL)2]2(BF4)2 (2, M = Rh, Ir)and Au(PPh3)Cl (Eq. (1)).

M

2, L = PPh3, M = Rh, Ir3, L = PBut

3, M = Rh

MO

O

THF/Et2O

LAuAuL

AuLLAu

1+

AuLLAuO

AuL2

BF4

(BF4)2

-2LAuCl

ð1Þ

An analogous reaction between 1 (M = Rh) and [(tBu3-

PAu)3(l-O)]BF4 gives the yellow tBu3P complex [Rh-(DBCOT)(l4-O)(tBu3PAu)2]2(BF4)2 (3, Eq. (2)).

4

EtOH/H2O1 KOH Rh Rh

HO

OHM = Rh

ð2Þ

e drawn as 50% probability ellipsoids. Hydrogen atoms omitted.

Fig. 2. Drawing of the solid-state structure of 2 (M = Rh). Atoms aredrawn as 50% probability ellipsoids. Hydrogen and all but the ipso phenylcarbon atoms have been omitted.

Table 3Selected distances (A) and angles (�) for 2 (M = Rh, Ir) and 3

2 (M = Rh) 2 (M = Ir) 3

Au1–M1 2.9589(6) 3.0036(2) 2.9922(3)Au1–M10 3.0365(7) 3.0092(2) 3.0002(3)Au1–Au2 2.9498(5) 3.0231(2) 3.1467(2)M1–M1 3.2136(11) 3.2185(3) 3.2197(5)Au1–P1 2.225(2) 2.2323(10) 2.2548(9)Au2–P2 2.215(2) 2.2195(10) 2.2446(9)Au1–O1 2.130(5) 2.167(2) 2.131(2)Au2–O1 2.051(5) 2.060(2) 2.054(2)M1–O1 2.070(5) 2.069(2) 2.083(2)M1–O10 2.088(4) 2.078(2) 2.093(2)Mean M–O 2.08(1) 2.074(6) 2.088(7)M1–C1 2.122(6) 2.121(3) 2.109(3)M1–C2 2.109(7) 2.112(3) 2.109(3)M1–C9 2.124(8) 2.120(4) 2.135(3)M1–C10 2.109(9) 2.117(4) 2.121(3)C1–C2 1.418(10) 1.424(5) 1.412(5)C9–C10 1.393(11) 1.422(5) 1.410(5)O1–Au1–P1 175.43(15) 170.96(7) 177.93(7)O1–Au2–P2 175.28(14) 175.35(7) 177.03(7)O1–M1–O1 78.8(2) 78.17(10) 79.12(9)Au1–O1–Au2 89.74(17) 91.27(9) 97.50(9)Au1–O1–M1 92.6(2) 90.30(9) 90.48(9)Au1–O1–M10 89.11(17) 90.27(9) 90.50(9)Au2–O1–M1 125.8(2) 127.04(12) 129.44(11)Au2–O1–M10 133.0(3) 131.09(12) 128.69(12)M1–O1–M1 101.2(2) 101.83(10) 100.88(9)

Table 1Crystal data and structure refinement details for 1 (M = Ir), 2 (M = Rh, Ir), 3, and 4a

1 2 (M = Rh) 2 (M = Ir) 3 4

Formula C32H24Cl2Ir2�2C4H8O� 2CH2Cl2

C104H84Au4B2F8O4P4Rh2 �4CH2Cl2

C104H84Au4B2-F8O4P4Ir2

C80H132Au4B2F8O4P4Rh2

� 2CH2Cl2

C32H26O2Rh2

� 3(C3H7NO)Fw 863.81 2970.96 3175.18 2586.89 867.64Space group P21/n P�1 P21/n P21/c P�1a (A) 12.3260(5) 14.3065(15) 13.2985(5) 12.4564(7) 9.163(3)b (A) 8.4654(4) 15.0265(16) 16.7304(6) 13.9482(8) 12.116(3)c (A) 12.3368(5) 15.1662(16) 24.0034(8) 27.0041(15) 18.863(5)a (�) 90 112.859(2) 90 90 93.873(4)b (�) 96.5710(10) 93.188(2) 100.3680(10) 99.3300(10) 103.295(4)c (�) 90 90.373(2) 90 90 111.320(4)V (A3) 1278.82(10) 2723.0(5) 5253.3(3) 4629.7(5) 1872.0(9)Z 2 1 2 2 2Dcalc (g/cm3) 2.244 1.812 2.007 1.856 1.539l (mm�1) 10.626 5.886 8.416 6.905 0.930R1

b, wR2c 0.0177, 0.0417 0.0483, 0.1167 0.0241, 0.0474 0.0243, 0.0528 0.0853, 0.2133

Goodness-of-fit 1.083 0.995 1.044 1.063 1.083

a k = 0.71070 A (Mo), T = �100 �C.b R1 ¼

PkF o j � j F ckð Þ=

PF o.

c wR2 ¼P

wðjj F o j � j F ckÞ2� �

=P

wF 2o

h i1=2; w ¼ 4F 2

o=P

F 2o

� �2.

Table 2Selected distances (A) and angles (�) for 1 (M = Ir)

Ir1–Ir10 3.5325(3) Ir1–C2 2.102(3)Ir1–Cl1 2.3865(8) Ir1–C9 2.115(3)Ir1–Cl10 2.3993(8) Ir1–C10 2.107(3)Mean Ir–Cl 2.393(9) C1–C2 1.440(4)Ir1–C1 2.100(3) C9–C10 1.425(4)Cl1–Ir1–Cl1 84.86(3) Ir1–Cl1–Ir1 95.14(3)

A. Singh, P.R. Sharp / Inorganica Chimica Acta 361 (2008) 3159–3164 3161

All three complexes were subjected to single crystal X-ray analysis. A drawing of 2 (M = Rh) is representativeand is given in Fig. 2. Crystal data and data collectionand processing parameters are summarized in Table 1.

Selected distances and angles are given in Table 3. Thestructures are similar to each other and to the previouslyreported COD and NBD analogs [14] with a planarM2O2 diamond core, an LAu fragment bonded to each Oatom in the core plane, and a second LAu fragmentbonded to each O atom perpendicular to the core plane.The resulting coordination about the O atoms is trigonalpyramidal with the M atoms and one Au atom in the plane

3162 A. Singh, P.R. Sharp / Inorganica Chimica Acta 361 (2008) 3159–3164

and the second Au atom in the axial position. Close M–Auand Au–Au contacts (�3.0 A) indicate closed shell d8–d10

and d10–d10 ‘‘aurophilic” interactions [15–17]. In compar-ing the structures of 2 (M = Rh), 2 (M = Rh), and 3 theclose congruency for these group 9 metals is apparent.The M–O, M–C, and M–M distances are all essentiallyidentical as are the angles inside the M2O2 diamond core.Sizeable differences only appear between 2 and 3 and whenthe parameters associated with the Au centers are exam-ined. Steric interactions between the PBu3 groups on theAu centers in 3 evidently cause a lengthening of the Au1–Au2 distance from 2.9589(6) and 3.0036(2) in 2 to3.1467(2) A in 3. In all three complexes the Au2 atomsare coplanar with the M2O2 core indicating that theincreased separation of the Au atoms in 3 results frommovement of the Au1 center. This is seen in the Au1–O–Au2 angle, which increases from 89.74(17)� and 91.27(9)�in 2 to 97.50(9)� in 3. Despite this difference the Au1–O dis-tances in the three complexes are essentially identical as arethe shorter Au2–O distances. The structure of the norbor-nadiene analog of 2 (M = Rh) has been reported and againthere is a close match with the current structures withnearly identical metrical parameters involving the non-diene interactions [14].

Table 4Selected distances (A) and angles (�) for [Rh(DBCOT)(l-OH)]2 (4)

Rh1–Rh2 2.9535(12) Rh1–C10 2.102(9)Rh1–O1 2.052(6) Rh2–C17 2.082(9)Rh1–O2 2.028(6) Rh2–C18 2.099(9)Rh2–O1 2.047(6) Rh2–C25 2.113(8)Rh2–O2 2.062(6) Rh2–C26 2.116(8)Mean Rh–O 2.05(1) C1–C2 1.430(12)Rh1–C1 2.095(8) C9–C10 1.393(12)Rh1–C2 2.115(8) C18–C17 1.389(12)Rh1–C9 2.107(8) C25–C26 1.425(12)O1–Rh1–O2 78.4(2) Rh1–O1–Rh2 92.2(2)O1–Rh2–O2 77.8(2) Rh1–O2– Rh2 92.5(2)

Fig. 3. Drawing of the solid-state structure of 4. Carbon bonded H atoms omatoms are drawn as arbitrary-sized spheres.

In contrast to the solid-state structures, 31P NMR spec-tra for 2 and 3 show equivalent phosphine ligands as indi-cated by a single peak at 26 and 88 ppm, respectively. (Lesslikely, is the possibility that the different phosphine ligandpeaks are coincidently overlapping in all three complexes.)Solution-state structures are either different or there israpid exchange between the two phosphine ligands sites.Exchange could occur by inversion of the O atom trigonalpyramid, a process that could be easily accomplished byrotation about the O atoms moving the axial LAu unit intothe O atom trigonal plane and the in-plane LAu unit intothe new axial position opposite the original axial position.Alternatively, dissociation exchange of the LAu+ frag-ments may be occurring. 1H NMR spectra for 2 and 3 showthe expected peaks for the phosphine ligands and theDBCOT ligands with overlap occurring in the aromaticregion for 2. The olefinic peaks are singlets for all threecomplexes. This should be compared to the doubletobserved for the parent chloride 1 (M = Rh) and indicatesa loss of coupling to the 103Rh center in 2 (M = Rh) and 3.

Chloro/hydroxo exchange in 1 (M = Rh) with KOH inethanol/water gives the hydroxo dimer [Rh(DBCOT)(l-OH)]2 (4) in 85% yield (Eq. (2)). The 1H NMR spectrumof 4 in CD2Cl2 shows DBCOT ligand aromatic signalsand the olefinic peak at 6.91 ppm as a singlet with no1H–103Rh coupling. The OH group is observed as a singletat 1.86 ppm.

A yellow crystal of 4 was subjected to an X-ray analysis.Crystal data and data collection and processing parametersare summarized in Table 1. Selected distances and anglesare listed in Table 4 and a drawing of the structure is givenin Fig. 3. The structure consists of the expected square pla-nar Rh centers with a common edge containing the bridg-ing OH groups. The structure is folded along the commonedge such that the two Rh coordination planes are offset.

In contrast to 1 (M = Ir), the structure of 4 is foldedwith a dihedral angle between the Rh1, O1, O2 and Rh2,O1, O2 planes of 43.6(2)�. This is smaller than the COD

itted. Non-H atoms are drawn as 50% probability ellipsoids. Hydrogen

A. Singh, P.R. Sharp / Inorganica Chimica Acta 361 (2008) 3159–3164 3163

analog, [Rh(COD)(l-OH)]2, where the two Rh,O,O planeshave a dihedral angle of 56� [18,19]. (The structure of[Rh(COD)(l-OH)]2 co-crystallized with another complexwas also determined but the [Rh(COD)(l-OH)]2 moleculeis disordered [20].) Correspondingly, the Rh–Rh distancein 4 (2.954(1) A) is longer than in the COD analog(2.878 A). The Rh–O distances in the two structures showsubstantial ranges (2.028–2.062 A and 2.052–2.098 A for[Rh(COD)(l-OH)]2) but suggest a slightly shorter distancein 4.

3. Conclusions

In contrast to Pt(II), where we observed significant dif-ferences in the chemistry of the COD and DBCOT systems,the Rh(I) and Ir(I) DBCOT systems follow essentially iden-tical chemistry to the COD analogs, at least for the limitedreactions in this investigation. (Previous workers haveobserved differences [1].) Structural data are also comple-mentary for the two systems with nearly identical metricalparameters or only slight variations of minimal signifi-cance. This closer match in the COD and DBCOTRh(I)/Ir(I) chemistry may be related to the closer matchin bonding for COD and DBCOT to the Rh(I) and Ir(I)centers than was observed for Pt(II).

4. Experimental

DBCOT (dibenzo[a,e]cyclooctatetraene) [4], [(LAu)3(l3-O)]BF4(L = PPh3, tBu3P) [21–23] and [M(COD)(l-Cl)]2(M = Rh [6,7], Ir [8]) were prepared by the literature proce-dures. Experiments were performed under a dinitrogenatmosphere in a Vacuum Atmospheres Corporation dry-box or on a Schlenk line. Solvents were dried and degassedand stored under dinitrogen over 4 A molecular sieves orsodium metal. NMR spectra were recorded on a BrukerAMX-250, �300, or �500 spectrometer at ambient probetemperatures. Shifts are given in ppm with positive valuesdownfield of TMS (1H and 13C) or external H3PO4(31P).13C and 1H NMR spectra were recorded in proton decou-pled mode. 195Pt NMR spectra are referenced to externalK2PtCl4(aq). Desert analytics performed the microanalyses(inert atmosphere). The presence of solvent of crystalliza-tion in the analyzed sample was confirmed by NMRspectroscopy.

4.1. Dichlorobis(g4-dibenzo[a,e]cyclooctatetraene)-

dirhodium, [Rh(DBCOT)(l-Cl)]2 (1, M = Rh)

Method A: A solution of RhCl3 � 3H2O (50.0 mg,0.190 mmol) in 10 mL of EtOH and 2 mL water was addedto a stirred solution of DBCOT (38.7 mg, 0.190 mmol) inEtOH (10 mL). The reaction mixture was brought to refluxwith stirring. Over 3 h the deep red solution slowly becameyellow and a solid deposited. The yellow solid was collectedby filtration, washed with water, ethanol, and then diethylether. Yield: 122.0 mg (94%).

Method B: A solution of [Rh(COD)(l-Cl)]2 (71.7 mg,0.100 mmol) in CH2Cl2 (5 mL) was added to stirred solu-tion of DBCOT (40.8 mg, 0.200 mmol) in CH2Cl2 (5 mL).The homogeneous mixture changed from yellow to orangewithin 5 min. The mixture was further stirred for 15 minand then concentrate in vacuo to ca. 5 mL. Et2O (10 mL)was added and the mixture was stored at �30 �C for24 h. The resulting fine yellow product was isolated byfiltration. Yield: 62.3 mg (91%). Anal. Calc. for C32H24-Rh2Cl2: C, 56.09; H. 3.53. Found: C, 56.27; H, 3.67% .1H NMR (250 MHz, CD2Cl2): 6.97 (s, 8H, aromaticCH), 5.09 (d, 4H, JRh–H = 2.2 Hz, olefinic CH).

4.2. Dichlorobis(g4-dibenzo[a,e]cyclooctatetraene)-diiridium, [Ir(DBCOT)(l-Cl)]2 (2)

Method A: IrCl3 � 3H2O (50.0 mg, 0.141 mmol) in 10 mLof EtOH and 2 mL water was added to a vigorously stirredsolution of DBCOT (28.9 mg, 0.141 mmol) in EtOH(10 mL). The resulting mixture was brought to reflux withstirring. Over 3 h the solution became yellow and soliddeposited. The volume of the solution was reduced invacuo to ca. 10 mL. Et2O (20 mL) was added and the mix-ture stored at �30 �C for 24 h. The resulting yellow solidwas collected by filtration, washed with water, ethanoland diethyl ether. Yield: 114.0 mg (94%).

Method B: A solution of [Ir(COD)(l-Cl)]2 (89.5 mg,0.100 mmol) in CH2Cl2 (5 mL) was added to stirred solu-tion of DBCOT (40.8 mg, 0.200 mmol) in CH2Cl2 (5 mL).The mixture changed from yellow to orange within5 min. The mixture was further stirred for 25 min and thenconcentrate in vacuo to ca. 5 mL. Et2O (10 mL) was addedand mixture was stored at �30 �C for 24 h. The resultingfine microcrystalline yellow product was isolated by filtra-tion. Yield: 76.0 mg (88%). Crystal for the X-ray analysiswas obtained by recrystallization from CD2Cl2/Et2O at�30 �C. Anal. Calc. for C32H24Ir2Cl2: C, 44.49; H, 2.80.Found: C, 44.09; H, 2.96%. 1H NMR (250 MHz, CD2Cl2):7.03–6.86 (m, 8H, aromatic CH), 5.35 (s, 4H, olefinicCH).

4.3. [Rh(DBCOT)(l4-O)(AuPPh3)2]2(BF4)2

(2, M = Rh)

A suspension of [Rh(DBCOT)(l-Cl)]2 (68.5 mg,0.100 mmol) in CH2Cl2(30 mL) was vigorously stirred withsolid [(Ph3PAu)3(l3-O)]BF4 (296 mg. 0.200 mmol). Themixture became homogeneous and orange within 30 minand was further stirred for 2 h and then concentrated invacuo (15 mL). Toluene (30 mL) was added and mixturewas stored at �30 �C for 24 h. The resulting pale yellow-orange microcrystalline solid was isolated by filtration.Yield: 225 mg (85%). Crystals for X-ray analysis wereobtained by recrystallization from CDCl2/THF. Anal.Calc. for C104H84Au4B2F8O2P4Rh2: C, 47.01; H, 3.19.Found: C, 46.96; H, 3.35%. 1H NMR (250 MHz, CD2Cl2):7.59–7.30 (m, 60H, Ph), 6.96–6.68 (m, 16H, aromatic CH),

3164 A. Singh, P.R. Sharp / Inorganica Chimica Acta 361 (2008) 3159–3164

4.83 (s, 8H, olefinic CH). 31P{1H} NMR (101.2 MHz,CD2Cl2): 26.1 (s).

4.4. [Rh(DBCOT)(l4-O)(AuPtBu3)2]2(BF4)2 (3)

A suspension of [Rh(DBCOT)(l-Cl)]2 (68.5 mg, 0.100mmol) in CH2Cl2 (30 mL) was vigorously stirred with solid[(tBu3PAu)3(l3-O)]BF4 (260 mg. 0.200 mmol). The mixturebecame homogeneous and red within 20 min. Reaction wasfurther stirred for 2 h and then concentrated in vacuo(15 mL). To this solution, toluene (30 mL) was addedand stored at �30 �C for 24 h. The resulting pale yellowsolid was isolated by filtration. Yield: 199 mg (82%). Crys-tals for X-ray analysis were obtained by recrystallizationfrom CD2Cl2/Et2O. Anal. Calc. for C80H132Au4B2-

F8O2P4Rh2: C, 39.41; H, 5.13. Found: C, 39.73; H,5.46%. 1H NMR (250 MHz, CD2Cl2): 7.00–6.81 (m, 16H,aromatic CH), 4.65 (s, 8H, olefinic CH), 1.54 (s, 54H,Me), 1.48 (s, 54H, Me). 31P{1H} NMR (101.2 MHz,CD2Cl2): 88.2 (s).

4.5. [Ir(DBCOT)(l4-O)(AuPPh3)2]2(BF4)2 (2, M = Ir)

[Ir(DBCOT)(l-Cl)]2 (86.3 mg, 0.100 mmol) in THF(30 mL) was vigorously stirred with solid [(Ph3PAu)3-(l3-O)]BF4 (296 mg. 0.200 mmol). The mixture becamehomogeneous and color turned to orange within 30 min.Stirring was continued for 2 h and then volume of solutionwas reduced in vacuo (15 mL). Et2O (30 mL) was addedand the mixture stored at �30 �C for 24 h. The orangemicrocrystalline solid was isolated by filtration. Yield:245 mg (86%). Crystals for X-ray analysis were obtainedby slow evaporation from a CDCl2 solution. Anal. Calc.for C104H84Au4B2F8O2P4Ir2: C, 44.04; H, 2.99. Found: C,43.83; H, 2.78. 1H NMR (250 MHz, CD2Cl2): 7.58–7.28(m, 60H, Ph), 6.90–6.75 (m, 16H, aromatic CH), 5.33 (s,8H, olefinic CH). 31P{1H} NMR (101.2 MHz, CD2Cl2):26.0 (s).

4.6. [Rh(DBCOT)(l-OH)]2 (6)

A solution of potassium hydroxide (12.32 mg,0.22 mmol) in 0.7 mL of H2O and 5 mL EtOH was addedto a suspension of [Rh(DBCOT)(l-Cl)]2 (68.5 mg, 0.100mmol) in EtOH (25 mL). After 5 h the resulting mixture

changed from yellow to orange. The mixture was furtherstirred for 4 and then concentrate in vacuo to ca. 10 mL.Et2O (20 mL) was added and mixture was stored at�30 �C for 24 h. Yield: 55.2 mg (85%). Crystal for theX-ray analysis was obtained by recrystallization fromDMF/Et2O at �30 �C. Anal. Calc. for C32H26O2Rh2: C,59.28; H, 4.04. Found: C, 59.25; H, 3.70%. 1H NMR(250 MHz, CD2Cl2): 7.16–7.20 (m, 16, aromatic CH),6.91 (s, 8H, olefinic CH), 1.86 (s, 2H, OH).

Appendix A. Supplementary material

Supplementary data associated with this article can befound, in the online version, at doi:10.1016/j.ica.2007.12.007.

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