Russian Chemical Bulletin, International Edition, Vol. 62, No. 5, pp. 1268—1271, May, 20131268

Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1268—1271, May, 2013.

1066�5285/13/6205�1268 © 2013 Springer Science+Business Media, Inc.

Synthesis and structure of (tricarbollide)iodide iridium complex[(�1�ButNH�1,7,9�C3B8H10)IrI2]2

D. A. Loginov,a A. M. Miloserdov,a Z. A. Starikova,a J. Holub,b and A. R. Kudinova

aA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,28 ul. Vavilova, 119991 Moscow, Russian Federation.

Fax: +7 (499) 135 5085. E�mail: arkudinov@ineos.ac.rubInstitute of Inorganic Chemistry, Academy of Sciences of the Czech Republic,

Research Center for New Inorganic Compounds and Advanced Materials, University of Pardubice,250 68 R

ez, Czech Republic

Cyclooctadiene complex (�1�ButNH�1,7,9�C3B8H10)Ir(cod) (1) was obtained by the re�action of [(7�ButNH�7,8,9�C3B8H10)]Tl with [(cod)IrCl]2 in the presence of TlPF6. The reac�tion of 1 with I2 gave diiodide [(�1�ButNH�1,7,9�C3B8H10)IrI2]2 (2a). According to the X�raydiffraction data, complex 2a has a dimeric structure with two bridging iodine atoms.

Key words: iridium, metallacarboranes, tricarbollide.

Rhodium and iridium (cyclopentadienyl) halide com�plexes [Cp*MX2]2 (X = Cl, Br, and I) are widely usedin organometallic synthesis.1,2 The elimination of halideions under the action of Ag+ salts in organic solvents af�fords highly reactive solvate complexes [Cp*M(Solv)3]2+

(Solv = Me2CO, MeCN, and others), whose further reac�tions make it possible to synthesize diverse organometallicderivatives containing the Cp*M fragment.3—6 Syntheticpossibilities of this approach can be extended by usinghalide complexes [(ring)MX2]2 containing other mono�anionic �ligands, for example, carborane ligands.7—9

Rhodium tricarbollide complexes [(�1�ButNH�1,7,9�C3B8H10)RhX2]2 (X = Br, I) have recently been synthe�sized by the reaction of cyclooctadiene derivative (�1�ButNH�1,7,9�C3B8H10)Rh(cod) (cod is cycloocta�1,5�di�ene) with halogens. Its structure was determined by X�raydiffraction analysis.10 In this work, we report the synthesisand structure of iridium analog [(�1�ButNH�1,7,9�C3B8H10)IrI2]2.

Results and Discussion

Iridium cyclooctadiene complex (�1�ButNH�1,7,9�C3B8H10)Ir(cod) (1) was synthesized by the reaction of[(7�ButNH�7,8,9�C3B8H10)]Tl with [(cod)IrCl]2 (cod iscycloocta�1,5�diene) in the presence of TlPF6 (Scheme 1).It is necessary to use the latter because of the low reactivi�ty of thallium tricarbollide. Note that the polyhedral rear�rangement of the carborane cage occurs in the course of

this reaction. Similar rearrangements have been observedearlier in the reactions of the [7�ButNH�7,8,9�C3B8H10]–

anion with other transition metal complexes.11—13 Themain reason for polyhedral rearrangements of metallacar�boranes is the Coulomb repulsion of the negatively chargedcarbon atoms.14 Unlike the rhodium analog, complex 1decomposes on prolonged storage both in air and an inertatmosphere and, hence, it was synthesized directly priorto further use.

Scheme 1

We found that the reaction of 1 with I2 afforded iodidecomplex [(�1�ButNH�1,7,9�C3B8H10)IrI2]2 (2a) ina yield of 79% (Scheme 2). Similar reactions with Cl2or Br2 give a complicated mixture of products, whose1Н NMR spectrum contains signals from the cyclooctadi�ene ligand. Probably, one of the products is a complex ofthe [(�1�ButNH�1,7,9�C3B8H10)Ir(cod)X]+ type, whose

Dedicated to blessed memory of P. V. Petrovskii who contrib�uted considerably to the development of organometallic chemistry.

(Tricarbollide)iridium complexes Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013 1269

formation has been observed earlier for the cyclopentadie�nyl derivatives.15 Nevertheless, halides [(�1�ButNH�1,7,9�C3B8H10)IrX2]2 (X = Cl (2b); Br (2c)) were isolatedin low yields after keeping a mixture of products in air fortwo weeks.

Scheme 2

The structure of iodide 2a was confirmed by X�raydiffraction analysis (Fig. 1). Selected bond lengths andangles are listed in Table 1. Complex 2а has a dimericstructure in which two iodine atoms occupy the bridgingposition and two other atoms are terminal. Interestingly,the bond of the iridium atom with the С(9) carbon atom inthe trans�position to the terminal iodine atom is longerthan the Ir—С(7) bond by 0.02 Å. In addition, the bonds ofthe iridium atom with the bridging iodine atoms Ir—I(2)and Ir—I(2A) in compound 2а (2.678 and 2.754 Å, re�spectively) differ significantly between each other, where�as in the related cyclopentadienyl complex [Cp*IrI2]2 they

are nearly equivalent (2.708 and 2.712 Å).16 The bond ofthe iridium atom with the terminal iodine atom Ir—I(1)(2.685 Å) is shorter than in [Cp*IrI2]2 (2.694 Å), indicat�ing its higher strength in complex 2а.

The pentagonal face of the carborane ligand С2B3 hasan envelope conformation with the deviation of the B(8)atom from the С(9)B(10)B(11)C(7) plane (the angle be�tween the С(7)B(8)C(9) and С(9)B(10)B(11)C(7) planesis 11.2). The Ir...С2B3 distance (1.552 Å) in 2а is some�what shorter than the Rh...С2B3 distance (1.596 Å) inthe related rhodium complex [(�1�ButNH�1,7,9�C3B8H10)RhI2]2.

Fig. 1. Structure of complex 2a (thermal ellipsoids of 50% probability). Hydrogen atoms, except for H(1) and H(1A), are omitted.

C(5)C(6)

H(1)

C(4)

C(1)

B(6)

B(5)B(8)

B(2)

B(3)

B(11)B(10)

B(4)

C(9)

Ir(1)

I(2A)

I(2)

Ir(1A) N(1A)

H(1A)

C(2)

C(7)

N(1)

I(1)

Table 1. Selected bond lengths (d) and an�gles () in complex 2a

Parameter Value

Bond d/Å

Ir(1)—C(7) 2.180(3) Ir(1)—B(8) 2.141(3) Ir(1)—C(9) 2.204(3) Ir(1)—B(10) 2.140(4) Ir(1)—B(11) 2.156(4) Ir(1)—I(1) 2.6845(3) Ir(1)—I(2) 2.6777(2) Ir(1)—I(2A) 2.7542(3) C(7)—B(8) 1.763(5) B(8)—C(9) 1.738(5) C(9)—B(10) 1.770(5) B(10)—B(11) 1.822(5) C(7)—B(11) 1.781(5) C(1)—N(1) 1.397(4) N(1)—C(2) 1.488(4)

Angle /deg

C(7)—B(8)—C(9) 105.1(2) B(8)—C(9)—B(10) 111.1(2) C(9)—B(10)—B(11) 106.4(2) B(10)—B(11)—C(7) 104.9(2) B(11)—C(7)—B(8) 111.1(2) C(1)—N(1)—C(2) 127.3(3)

Loginov et al.1270 Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013

To conclude, complex 2а turned out to be poorly reac�tive because of the strengthening of the Ir—I bonds. Inparticular, unlike the rhodium analog, this complex doesnot almost react with [(�C2B9H11)Tl]Tl. In addition, thepresence of the secondary amino group prevents the use ofAg+ salts for the elimination of iodide ions because of sideoxidation processes.

Experimental

The reactions were carried out under argon using anhydroussolvents prepared according to standard procedures. Proceduresrelated to the isolation of products were conducted in air. Thestarting compounds [(cod)IrCl]2 (see Ref. 17) and [(�7�But�

NH�7,8,9,�C3B8H10)]Tl (see Ref. 18) were synthesized usingknown procedures. 1Н NMR spectra were recorded on a BrukerAvance�400 instrument (400.13 MHz (1Н), 128.38 MHz (11В)).

(1�tert�Butylamino�1,7,9�tricarbollyl)(1,5�cyclooctadiene)�iridium, (�1�ButNH�1,7,9�C3B8H10)Ir(cod) (1). Dichloro�methane (4 mL) was added to a mixture of [(cod)IrCl]2 (72 mg,0.22 mmol), [(�7�ButNH�7,8,9,�C3B8H10)]Tl (90 mg,0.22 mmol), and TlPF6 (75 mg, 0.22 mmol). The reaction mix�ture was stirred for 2 h. The solvent was removed in vacuo, andthe residue was extracted with petroleum ether. After the solventwas removed in vacuo, complex 1 was obtained in a yield of 90mg (81%) as a yellow solid. Found (%): C, 35.45; H, 6.64;N, 2.75; B, 17.15. C15H32NB8Ir. Calculated (%): C, 35.67;H, 6.38; N, 2.77; B, 17.12. 1Н NMR (CDCl3), : 1.31 (s, 9 H, But);2.23 (s, 2 H, CH); 2.26—2.38 (m, 8 H, cod); 4.00 (s, 4 H, cod).11B{1H} NMR (CDCl3), : –22.8 (s, 2 B); –17.4 (s, 2 B); –15.3(s, 2 B); –11.8 (s, 2 B).

Bis[diiodo(1�tert�butylamino�1,7,9�tricarbollyl)iridium], [(�1�ButNH�1,7,9�C3B8H10)IrI2]2 (2а). A solution of iodine (45 mg,0.18 mmol) in diethyl ether (3 mL) was added to a solution ofcomplex 1 (90 mg, 0.18 mmol) in petroleum ether (6 mL). Thereaction mixture was stirred for 10 min (no inert atmosphere isrequired). A brown precipitate formed was separated by centri�fuging, washed with diethyl ether, and dried. The yield was 92 mg(79%). Found (%): C, 12.85; H, 2.97; N, 2.11; B, 13.13.C14N2H40B16Ir2I4. Calculated (%): C, 12.92; H, 3.10; N, 2.15;B, 13.29. 1Н NMR (CDCl3), : 1.26 (s, 9 H, But); 3.82 (s, 2 H,CH). 11B{1H} NMR (CDCl3), : –21.3 (s, 1 B); –17.2 (s, 5 B);–6.6 (s, 2 B).

Reactions of complex 1 with Cl2 and Br2. A solution of Br2(0.01 mL, 0.21 mmol) in petroleum ether was added to a solutionof complex 1 (105 mg, 0.21 mmol) in the same solvent (6 mL)(or Cl2 was purged for 10 min). A formed yellow precipitate wasseparated by centrifuging, washed with diethyl ether, and dried.The product was kept in air for two weeks for the completedisplacement of the cyclooctadiene ligand. After reprecipitationwith petroleum ether from dichloromethane, complexes [(�1�ButNH�1,7,9�C3B8H10)IrX2]2 (2b,c) were obtained as yel�low solids.

Complex 2b (X = Cl). The yield was 21 mg (22%). 1Н NMR(CD2Cl2), : 1.26 (s, 9 H, But); 4.12 (s, 2 H, CH). 11B{1H} NMR(CD2Cl2), : –20.7 (s, 2 B); –18.8 (s, 1 B); –16.9 (s, 2 B); –4.8(s, 2 B); –2.0 (s, 1 B).

Complex 2c (X = Br). The yield was 15 mg (13%). 1Н NMR(CDCl3), : 1.24 (s, 9 H, But); 4.05 (s, 2 H, CH). 11B{1H} NMR

(CDCl3), : –20.7 (s, 2 B); –18.0 (s, 1 B); –16.9 (s, 2 B); –5.2(s, 2 B); –3.0 (s, 1 B).

X�ray diffraction analysis of complex 2a. The red needle�likecrystals of C14H40B16I4Ir2N2 are monoclinic; they were grownby slow diffusion in a bilayer system petroleum ether—solutionof the complex in CH2Cl2. The unit cell parameters are a == 15.3998(9) Å, b = 6.5943(4) Å, c = 17.1407(9) Å, = 112.4710(10), V = 1608.49(16) Å3, space group P21/n, Z = 2,dcalc = 2.687 g cm–3. The experimental array of 17 103 reflec�tions was obtained on a Bruker APEX II CCD diffractometer at100 K (Mo�K radiation, 2max = 56.00) from a single crystal0.45×0.22×0.10 mm in size. After equivalent reflections wereaveraged, 3885 independent reflections were obtained (Rint == 0.0331), which were used for structure deconding and refine�ment. An absorption correction ( = 12.117 mm–1) was appliedusing the SADABS program (Tmax and Tmin are 0.377 and 0.074,respectively). The structure was solved by a direct method, andall non�hydrogen atoms were localized in difference electrondensity syntheses and refined for F2

hkl in the anisotropic approx�imation. The hydrogen atoms in the carborane fragment werelocalized in difference electron density syntheses, and other hy�drogen atoms were placed in the geometrically calculated posi�tions. All hydrogen atoms were refined in the isotropic approxi�mation in the riding model with U(H) = nU(C), where U(C) isthe equivalent temperature factor of the carbon atom to whichthe H atom is bound, n = 1.5 for Me groups. The final values ofthe R factors are R1 = 0.0175 (calculated from Fhkl for 3580reflections with I 2(I)), wR2 = 0.0398 (calculated from F2

hklfor all 3885 reflections), 172 refined parameters, goodness�of�fitis 1.001. All calculations were performed using the SHELXTLprogram package.19 The atomic coordinates, temperature fac�tors, and complete data on the geometric parameters were de�posited with the Cambridge Crystallographic Data Centre,CCDC 905725.

This work was financially supported by the RussianFoundation for Basic Research (Project No. 12�03�31212).aaa

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Received October 18, 2012;in revised form February 11, 2013

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