Hetero-bischelated complexes of iridium(III) with 1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 2,2′-bipyridine

Notes

i293

Jlnorf nud ('hem. 1975.VoL37, pp 293-1294. PergamonPress Printedin Great Britain

Hetero-bischelated complexes of iridium(Ill) with 1,10-phenanthroline, 5,6-dimethyl-l,10-phenanthroline, and 2,2'-bipyridine (Receir:ed 21 June 1974)

THE REAC'F1ONSof iridiumllII) with 2,2'-bipyridine Ibipyl and 1.10-phenanthroline (phenl have been studied by several workers[1-5]. A number of complexes of iridium(Ill) with substituted bipy and phen have also been prepared[6 7]. These studies have shown that complexes containing either one bidentate ligand or two bidentate ligands are generally obtained. The identity of the bis complexes as the cis-isomers has been conclusively established [4.5]. Very recently, the tris complexes of iridium(Ill) with bipy and phen have also been successfully prepared and identified for the first time{81. Several other d ~ platinum metal ions, such as Rh(lll), Ru(II), and Os(ll) are also known to form mono, bis, and tris-chelated complexes with bipy and phen[9]. Complexes of these three d ' metal ions containing various combinations of bipy and phen have been prepared[10-12]. The hetero-chelated complex ions, [Rh(bipy),(phen)] ~+ and [Rh(bipy)(phen)d 3+ have been reported to display unusual non-exponential luminescence decays [13]. In view of the unusual properties displayed by the Rh(llll hetero-trischelated complexes, we have devised a synthetic route for the preparation of the first hetero-bischelated complexes of lr(IIl). We wish to report the successful synthesis and characterization of eis-dichloro-1,10-phenanthroline-2.2'-bipyridine iridium(Ill) chloride, {[IrCle(phen)(bipy)]C1}, and cis-dichloro1,10-phenanthrofine-5,6-dimethyl- 1,10-phenanthroline iridium(Ill) chloride, {[lrCL,(phen)(5,6-Mephen)]C1}.

RESULTSANDDISCUSSION Both complexes were prepared by a modification of the method reported by Broomhead and Grumley [5] for [IrCL,(phenblCI. We followed their procedure for the preparation of 1.10phenanthrolinium tetrachloro(1,10-phenanthroline)iridium(llI) chloride, {[H-phenl{lrC14(phen)]}, and then converted to this to K[lrCl~(phen)]. The absence of any free phen or H-phen in the potassium salt was established by the lack of any fluorescence from a saturated aqueous solution of the complex. The desired complex was then prepared by heating K[IrCl,(phen)] with a twofold molar excess of the appropriate ligand (2,2'-bipyridine or 5 6-dimethyl1,10-phenanthroline) in glycerol. The [lrCl2(phen)(5.6-Mephen)]Cl was also prepared by heating K[IrCL(5,6-Mephen)l with a twofold molar excess of 1,10-phenanthroline in glycerol. The two samples of [IrCl~_(phen)(5,6-Mephen)]CI obtained by these approaches were found tu be identical in all respects. This rules out any possible redistribution of the bound chelate in the starting material as a result of heating in glycerol. The [IrCl:lphen)(bipy)]CI could not be prepared from K[IrCl~(bips)] due to our inability to isolate this starting material. Each complex was purified by ion-exchange chromatography on Macherey, Nagel and Co. MN 2100 CM Carboxymethyl-Cellulose. After elation the complexes were further purified by several recrystallizations from ice-cold 0.1 M HCI. The complexes were carefully protected from exposure to direct lights due to their potential photoreactivity{ 14-16]. Several i.r. bands of the two complexes are pertinent to their identification as hetero-bischelates. The very strong out-of-plane C--H deformation of the 5,6-carbocyclic protons* occurs at 848 cm ' in [lrCl~(phen)dCi and is absent in [lrCl:(bipy)2]CI. The ~ery strong band at 847 cm ' in [lrCl.,(phen)(bipy/]CI therefore *I.R. assignments are based on the assignments of Schilt and Taylor, for a number of pben and bipy complexes, on the assignments of Smith for a large number of substituted phens, and on suggestions by Grigg et a1.{17] concerning the assignments of Ihese bands.

provides evidence for chelated phen. The out-of-plane heterocyclic C-H deformation[17] occurs at 775 cm ' with moderate strength in [lrCI2lphen)e]CI and is very strong at 770 cm ' in [lrCl-(bipy)~]Cl. In the hetero-chelated complex a very strong band appears al: 774 cm '. This is consistent with the presence of both chelated bipy and phen in the complex. The presence of coordinated chlorine is confirmed by the appearance of strong bands at 338 cm ' and 314 cm ' in the hetero-chelated complex as compared with the [r-CI stretching frequencies of 339 cm ' and 314 cm ~ in [IrCl2(phen):]Cl[5]. The lr--Cl stretching frequencie, in [lrCle(bipy)dCI are located at 327 cm ' and 307 cm '. The out-of-plane carbocyclic C-H deformation is a~so absent in [IrCl:(5,6-Mephen),,]C1, as expected. The i.r. spectrum of [IrCI2(phen)(5,6-Mephen!]CI contains a very strong band at 847 cm ', again indicating the presence of chelated phen. The heterocyclic C-H deformation of [IrCl2(5,6-Mephen)e]Cl is found as a strong band at 808 cm ', The presence of a smmg band at g09 cm ' and a medium shoulder at 780 cm ~ in [IrCL,(phen)(5,6Mephen)]CI provides evidence that the complex contains both chelated phen and 5,6-Mephen. The It-C1 stretching frequencies in the hetero-chelated complex at 337 cm ' and 313 cm ~ again confirm the presence of coordinated CI in the molecule. The proton N MR spectra of the two complexes are shown in Fig. 1. The spectrum of [IrCL(phen)(bipy)]C1 consists of a complicated pattern of lines in the aromatic proton region. Comparison of this spectrum with the NMR spectra of [lrCl~(phenhlCI and [lrCl~(bipy)_qCI shows that the hetero-chelated complex contains both phen and bipy as expected. The spectrum of [IrCl2(phen)(5,6Mephen)]CI consists of two distinct regions The aromatic proton region again consists of a complicated series of lines which indicate the presence of both phen and 5,6-Mephen. The methyl proton region consists of two peaks, indicating the presence of two non-equivalent methyl groups. This splitting of the two raethyl groups provides the most conclusive evidence to date for the assignment of bis-chelated complexes of phen with It(Ill) to 'the cis configuration. Integration of the NMR spectrum of [lrCIz(phen)(5,6-Mephen)]CI results in an experimental ratio of aromatic protons to methyl protons of 2.10-2.43 compared to a theoretical value of 2.34 (14/61. EXPERIMENTAL Potassium tetrachloro(1,10-phenanthrolim' )iridiumflll ) ¢'hloride [H-phen][lrCl,(phen)] (1 g) was stirred in the dark wilh 5 M potassium acetate (200 ml) for 3 hr. During this time the solid complex changed from a deep orange to a light orange color, and the solution turned to a yellow color due to the slight solubility of the potassium ~alt. The K[lrCl~(phen)] was collected on a glass filter and washed repeatedly with cold water to remove free phen. Conversion of the phenanthrolinium salt tn the potassium salt was quantitative. Cis-dichlon~(l,10-phenanthroline)(2,2'-bipyridine )iridium { .ffl 1 chloride and cis-dichloro ( 1,10-phenanthmline )(5,6 dimethvl- 1,10phenanthroline liridium ( III ) chloride K[lrCl~(phen/] (0.45 g) was mixed with the appropriate ligand (0.245 g bipy or 0.315 g 5,6-Mephen) in glycerol ( t0 tnl) and heated to the boiling point for 1 rain. The mixture turned a deep, clear red color as the solution was heated and then to a bright yellow-orange color as the boiling point was reached. The reaction mixture was cooled immediately with ice and diluted with water (20 ml). This solution was passed onto a cation exchange column of Macherey. Nagel and Co. MN 2100 CM carboxymethyl-cellulose resin which had been converted to the potassium form by treatment with pH 6 KzHPO, buffer solution. After elution with water to remove

1294

Notes

,I

10.4

IO.O

.

.

.

.

9.6

.

.

.

9.2

[ Ir Clz(phen)(bipy)]Cl

8.8

'

'

8.4

' PPM

8'4

8.0

'

8'0

7.6

'

7'6

ff

3'4

310

Fig. 1. Proton NMR spectra of cis-dichloro- 1,10-phenanthroline-2,2'-bipyridine iridium(III) chloride and cis-dichloro1,10-phenanthroline-5,6-dimethyl-1,10-phenanthroline iridium(IlI) chloride in D20 at 95°C. glycerol, the complex was eluted from the column with 0.1 M HCI and then recrystallized several times from ice cold 0.1 M HCI. Yields of 0.10g of [IrCl2(phen)(bipy)]C1 and 0.15g of [IrCl2(phen)(5,6-Mephen)] were obtained. Anal. Calcd for [IrCI2C22Ht6N4]C1.3H20: C, 38.35; H, 3.22; N, 8.13. Found: C, 38.04; H, 3.46; N, 7.70. Calcd for [IrC12C26H~oN4]CI.3H20: C, 41.25; H, 3.46; N, 7.40. Found: C, 41.06; H, 3.65; N, 7.44.

Physical measurements The NMR spectra were recorded with a Varian HA-100 on solutions of the complexes in D20 at 95°C. I.R. spectra were recorded with a Perkin-Elmer 225 spectrophotometer on samples of the complexes in KBr pellets. Acknowledgements--Acknowledgement is made to the donors of The Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. We also acknowledge the partial support of this project provided by the Committee on Research of the University of California, Santa Barbara. We wish to thank Professor J. T. Gerig for providing NMR spectra and for consultation on their interpretation. Department of Chemistry University of California Santa Barbara, California, 93106

RICHARD J. WATTS* JOHN S. HARRINGTON

REFERENCES 1. R. D. Gillard and B. T, Heaton, J. chem. Soc. 451 (1969).

2. B. Chiswell and S. E. Livingstone, J. inorg, nucl. Chem. 26, 47 (1964). 3. R. E. De Simone and R. S. Drago, Inorg. Chem. 8, 2517 (1969). 4. L. H. Berka, R. R. Gagne, G. E. Philippon and C. E. Wheeler, Inorg. Chem. 9, 2705 (1970). 5. J. A. Broomhead and W. Grumley, Inorg. Chem. 10, 2002 (1971). 6. R.J. Watts and G. A. Crosby, J. Am. chem. Soc. 93, 3184 (1971). 7. R.J. Watts, G. A. Crosby and J. L. Sansregret, Inorg. Chem. 11, 1474 (1972). 8. J.N. Demas, submitted for publication in J. Am. chem. Soc. 9. W. P. Grilfith, The Chemistry of The Rarer Platinum Metals. Interscience Publishers, London (1967). 10. D. A. Buckingham, F. P. Dwyer, H. A. Goodwin and A. M. Sargeson, Aust. J. Chem. 17, 325 (1964). 11. M. K. DeArmond and W. Halper, J. phys. Chem. 75, 3230 (1971). 12. G. A. Crosby, Washington State University, Private communication (1973). 13. W. Halper and M. K. DeArmond, J. Luminescence 5, 225 (1972). 14. J.A. Broomhead andW. Grumley, Chem. Comm. 1211 (1968). 15. L.H. Berka and G. E. Phillippon, J. inorg, nucl. Chem. 32, 3355 (1970). 16. M. M, Muir and W. L. Huang, Inorg. Chem. 12, 1930 (1973). 17. A. A. Scbilt and R. C. Taylor, J. inorg, nucl. Chem. 9,221 (1959); R. C. Smith, Ph.D. Thesis, Iowa State University, Ames, Iowa (1961); E. C. M. Grigg, J. R. Hall and R. A. Plowman, Aust. J. Chem. 15,425 (1962); and E. C. M. Grigg and J. R. Hall, Aust. J. Chem. 15, 864 (1962).

Y. inorg,nucl.Chem.,1975,Vol.37,pp. 1294-1296. PergamonPress. Printedin GreatBritain

Oxofluorocomplexes moleculaires du niobium(V) (Received 9 July 1974) INTRODUCTION LES RBNSEIGNEMENTS concernant les complexes fluor6s des 616ments de la colonne V (vanadium, niobium et tantale) demeurent actuellement beaucoup plus succincts que ceux se rapportant aux d6riv6s chlor6s. Ainsi, les oxochlorocompos6s de type {MOCI3(AA)} et {VOCI~L2} ( M = V , Nb; AA =bpy;

L = OPCI3, py, etc.) ont 6t6 caract6ris6s de mani~re nette[1-3]; par contre leurs homologues fluor6s n'6taient pas connus jusqu'~ ces derniers temps. Ce n'est qu'en 1973 que nous avons nous m6mes d6crits les premiers complexes de type {VOF3(AA)}, {VOF3L2} et {VO=F(AA)}[4]. Avec le niobium(V), aucun compos6 analogue n'a 6t6 signal6 jusqu'~ pr6sent, la chimie de coordination