Trihydrogen complexes of iridium (original) (raw)
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Organometallics, 1999
The trisacetonitrile complexes [IrClH(P i Pr 3 )(NCCH 3 ) 3 ]BF 4 (1) and [IrH 2 (P i Pr 3 )(NCCH 3 ) 3 ]-BF 4 (2) have been prepared in one-pot reactions with high yields by reaction of the iridium-(I) dimers [Ir(µ-Cl)(coe) 2 ] 2 and [Ir(µ-OMe)(cod) 2 ] 2 with the phosphonium salt [HP i Pr 3 ]BF 4 . The rates of exchange between free acetonitrile and the labile acetonitrile ligands of complexes 1 and 2 have been measured by NMR spectroscopy. This kinetic study has shown that both complexes readily dissociate one acetonitrile ligand trans to hydride, giving rise to fluxional five-coordinate intermediates. Substitution products 3-7 have been obtained by treatment of complexes 1 and 2 with CO and PMe 3 . The structures determined for 3-7 can be rationalized on the basis of the steric requirements of the ligands, indicating that the products are formed by thermodynamic control. Ethene inserts reversibly into the Ir-H bond of 1 to give the compound [IrCl(Et)(P i Pr 3 )(NCCH 3 ) 3 ]BF 4 (8), which has been used for the preparation of the stable ethyliridium(III) complexes [IrCl(Et)(P i Pr 3 )(Py) 2 (NCCH 3 )]BF 4 (9) and [Ir(η 2 -O 2 CCH 3 )Cl(Et)(P i Pr 3 )(NCCH 3 ) 3 ] (10), respectively. The molecular structure of 10 has been determined by X-ray crystallography. The reaction of 2 with ethene, at low temperature, results in the sequential formation of the ethene complex [IrH 2 (
Synthesis and characterization of new pentamethylcyclopentadienyl iridium hydride complexes
Journal of Organometallic Chemistry, 2012
Pentamethylcyclopentadienyl iridium dihydride complexes [Cp*Ir(H) 2 (PR 3 )]; (PR 3 ¼ PPh 2 Me, PTA) were prepared by reaction of [Cp*IrCl 2 (PPh 2 Me)] and [Cp*IrCl 2 (PTA)], respectively, with an excess of sodium bis(2-methoxyethoxy)aluminium hydride (Red-Al). Protonation of the dihydride [Cp*Ir(H) 2 (PPh 2 Me)] with HBF 4 $Et 2 O at low temperature gave the classical trihydride complex [Cp*Ir(H) 3 (PPh 2 Me)]BF 4 that displays quantum mechanical exchange coupling. Reaction of [Cp*IrCl 2 (PPh 2 Me)] with CO gave the halfsandwich iridium carbonyl compound [Cp*IrCl(CO)(PPh 2 Me)]Cl which, by reaction with NaBPh 4 , yielded yellow microcrystals of [Cp*IrCl(PPh 2 Me)(CO)]BPh 4 adequate for X-ray diffraction analysis.
Synthesis and X-ray structures of cyclometalated iridium complexes including the hydrides
Dalton Trans., 2013
Cyclometalation of [Cp*IrCl 2 ] 2 with ketimine ligands generated very active catalysts for transfer hydrogenation of imines as well as reductive amination. The synthesis and X-ray diffraction structures of three such complexes are disclosed in this paper. The hydrides of two complexes, key intermediates in hydrogenation, have been isolated and their structures determined by X-ray diffraction as well.
Preparation and interconversion of two isomeric iridium trihydrides
Inorganic Chemistry, 1981
The preparation, separation, and structural characterization of a,b,c-trihydrido-~~rbonylbis(triphenylphosphine)iridium(III) and a,bf,-trihydrido-d-carbonylbis(triphenylphosphine)iridium(III) are described. The kinetics of interconversion of the two isomers and of the displacement of H2 from both isomers by triphenylphosphine have been measured and indicate that interconversion occurs via reversible reductive elimination/oxidation sequence. Both the isomerization and substitution reactions are postulated to involve the intermediate IrH(CO)P,. The relationship of the present results to other studies of the stereochemistry of oxidative additions to square-planar iridium(1) complexes is discussed.
Inorganic Chemistry, 1984
Reaction of [(dipho~)Rh(acetone)~]BF~ with mer,truns-IrHC12L3 (L = PMe2Ph, PEt2Ph, PEt3; diphos = Ph2PCH2CH2PPh2) affords the hydridebridged dinuclear complexes [(diphos)Rh(p-H)(p-Cl)IrCIL,] BF4. Solution studies show that the bridging ligands are only weakly coordinated to the rhodium. The molecular structure of 3 (L = PEt3) has been determined by X-ray diffraction: monoclinic, space group P21/c, 2 = 4, a = 11.786 (2) A, b = 19.673 (4) A, c = 22.571 (4) A, @ = 89.88 (1)O. The structure was solved by Patterson and Fourier methods using 5750 observed reflections [I 2 3u(Z)] and refined to a conventional R = 0.057. The coordination around rhodium is distorted square planar and that around iridium is distorted octahedral. The Rh-Ir distance is 2.903 (1) A, and the bridging chlorine atom is almost symmetrically bonded to the metals (Rh-Cl = 2.386 (3), Ir-CI = 2.381 (3) A). The isoelectronic complex [(diph~s)Rh(p-H)(p-Cl)IrH(PEt,)~]BF~ was obtained in a similar reaction, starting from mer,~is-IrH~Cl(PEt,)~. Its structure determined by X-ray diffraction, as above, is monoclinic, space group P21, Z = 2, a = 11.102 (2) A, b = 13.582 (3) A, c = 16.694 (4) A, @ = 85.06 (2)'. The final agreement factor (for the 4553 observed reflections) R is 0.062. As for compound 3 the coordination around Rh and Ir is distorted square planar and octahedral, respectively. There is a pronounced asymmetry in the chlorine bridge (Rh-Cl = 2.394 (5), Ir-Cl = 2.510 (5) A), and the metal-metal separation is 2.969 (2) A. t o the synthesis of cationic Rh(1)-Ir(II1) complexes. Experimental Section All operations were carried out under purified nitrogen. Solvents were distilled under nitrogen and dried prior to use. Elemental analyses were formed by the Microanalytical Section of the Swiss Federal Institute of Technology. Infrared spectra in the region 4000-400 cm-' were recorded on a Beckman IR 4250 spectrophotometer as KBr pellets or Nujol mulls. The IH and 31P{'HJ NMR spectra were recorded at 90.00 and/or 250.00 and 36.43 MHz, respectively, on a FT Bruker WH-90 or F T Bruker 250 instrument. 'H and chemical shifts are given relative to external (CH3)$i and H3P04, respectively. A positive sign denotes a shift downfield of the reference. A. Syntheses. [Rh(dipho~)(nbd)]BF,~ (nbd = norbornadiene), mer,truns-IrHCl2L3 (L = PMe2Ph, PEt2Ph, PEt3),9 and mer,cis-IrHCl2(PMePh2),,Io were prepared according to literature methods. For the preparation of mer,cis-IrH,CI(PEt,),, a toluene solution of [ (~o c)~I r C l ]~ (coc = cyclooctadiene) was reacted with 3 equiv of PEt,, and hydrogen was bubbled through the solution for 10 min, leading almost quantitatively to the product. (a) ETH-Zcntrum. (b) Taken in Dart from the Ph.D. thesis of H.L. (c)