Jim D. Atwood

Organoiridium complexes as models for homogeneously catalyzed reactions

Cas des additions oxydantes (dhydrogene, dhalogenure dalkyl, activation des liaisons C-H), deliminations reductrices, des carbonylations, des eliminations en β, des oligomerisations...

Ligand and metal effects on the reactivity of metal carbonyls

Abstract The reactivity of metal carbonyl complexes is surveyed. The effect of charge, electron count, row and electronic configuration of the metal are examined for mononuclear carbonyls and more limited information is examined for metal clusters. Ligand effects are also examined for the metal carbonyls. The reactivity of metal carbonyl complexes changes by at least 15 orders of magnitude. This paper provides a framework for understanding such a range of reactivity.

Mono-Sulfonated Derivatives of Triphenylphosphine, [NH4]TPPMS and M(TPPMS)2 (TPPMS = P(Ph)2(m-C6H4SO− 3); M = Mn2+, Fe2+, Co2+ and Ni2+). Crystal Structure Determinations for [NH4][TPPMS]·½H2O, [Fe(H2O)5(TPPMS)]TPPMS, [Co(H2O)5TPPMS]TPPMS and [Ni(H2O)6](TPPMS)4·H2O

Preparation of the ammonium salt of TPPMS, [NH4]TPPMS, TPPMS = PPh2(m-C6H4SO− 3), greatly enhances water solubility and provides an efficient route to other metal complexes of TPPMS, M(TPPMS)2 M = Mn2+, Co2+, Fe2+ and Ni2+. For Co2+ and Fe2+ the metal has an octahedral ligand environment with five water molecules and one TPPMS coordinated through the sulfonate oxygen; the second TPPMS is not coordinated. For Ni2+ the octahedral coordination sphere is composed of water molecules and the TPPMS ligands are not coordinated. Structures are fully reported for [NH4]TPPMS·½H2O and [Fe(H2O)5(TPPMS)]TPPMS and partially reported for [Co(H2O)5TPPMS]TPPMS and [Ni(H2O)6]TPPMS2·H2O. All of the structures show hydrophobic regions consisting of aromatic rings and hydrophilic regions with hydrogen-bonding interactions.

Structural studies on platinum alkene complexes and precursors

A number of platinum complexes, precursors to alkene complexes (Pt2Cl4(PPh3)2 and cis-PtCl2(CH3CN)(PPh3)), alkene complexes (cis-PtCl2(C2H4)(PPh3), cis-PtCl2(C3H6)(PPh3) and cis-PtCl2(1-C6H12)(PPh3)), the diamination product of a 1,3-butadiene platinum complex and the 1,2,3,4-tetramethylcyclobutadiene complex resulting from dimerization of 2-butyne have been synthesized, characterized and the structures determined by X-ray diffraction. The ethylene complex, cis-PtCl2(C2H4)(PPh3), has been a useful reagent for preparing other alkene complexes. Reaction of a bound butadiene complex with diethylamine yielded a diamination product with anti-Markovnikov stereochemistry. An attempt at binding cis-butyne to the metal center resulted in metal-assisted formation of 1,2,3,4-tetramethylcyclobutadiene with previously unreported geometry.

Synthesis, characterization and the unpleasantly disordered crystal structure of Ir(Ome)(CO)(PPh3)2(SO4)

Abstract The adducts of O2 and SO2 with trans-MeOIr(CO)(PPh3)2 are formed in equilibria and have been characterized. Reaction of the SO2 adduct, Ir(OMe)(SO2)(CO)(PPh3)2 with dioxygen leads to the sulfato complex, Ir(Ome)(CO)(PPh3)2(SO4), the structure of which has been determined. Ir(Ome)(CO)(PPh3)2(SO4) crystallizes in the monoclinic system with a 11.958(2), b 14.163(3), c 12.231(2) A, β 118.365(12)°, V 1822.7(6) A3 and Z = 2. Diffraction data for 2θ = 4.5–45.0° (Mo-Kα) were collected with a Syntex P21 diffractometer and the structure was solved (assuming space group P21/m and an unpleasant 2-fold disordered model) and refined to R = 4.8% for all 2512 independent data (R = 3.5% for those 2042 data with ¦FO¦ > 6σ(¦F¦)). The iridium(III) atom has a distorted octahedral coordination sphere with trans PPh3 ligands and a cis-chelating bidentate O,O′-SO4 group; the structure is completed by mutually cis OMe and CO ligands.

Formation of carboncarbon bonds on di(organo)iridium complexes, rr′Ir(CO)(PPh3)2X (R,R′ = Me, Ph, CH2Ph, C(O)CH3; X = Cl, I) and the crystal structure of cis,cis,trans-[Ir(CH3)2(CO)2(PPh3)2+][CF3SO3-]

Abstract The reactions of RX with trans -R′Ir(CO(PPh 3 ) 2 are reported. Addition of CH 3 C(O)Cl to trans -CH 3 Ir(CO)(PPh 3 ) 2 leads to acetone; addition of CH 3 I to trans -PhIr(CO)(PPh 3 ) 2 leads to toluene; and addition of CH 3 I to trans -C 6 H 5 CH 2 Ir(CO)(PPh 3 ) 2 leads to ethylbenzene. Reaction of C 2 H 5 Br with trans -CH 3 Ir(CO)(PPh 3 ) 2 leads to CH 4 and C 2 H 4 . The addition of CH 3 I to trans -CH 3 Ir(CO)(PPh 3 ) 2 leads to Ir(CH 3 ) 2 Ir(CO)(PPh 3 ) 2 I from which Ir(CH 3 ) 2 (CO)-(PPh 3 ) 2 + and Ir(CH 3 ) 2 (CO) 2 (PPh 3 ) 2 + can be prepared. These dimethyl complexes do not undergo reductive elimination of ethane, acetone or diacetyl under a variety of conditions (CH 4 and C 2 H 6 are formed at decomposition). Thus for these complexes the charge, the presence of a free coordination site and the cis stereochemistry do not facilitate reductive elimination reactions. To ascertain that no structural features were preventing reductive elimination from the dimethyl complex we have examined the structure of cis,cis,trans -[Ir(CH 3 ) 2 (CO) 2 (PPh 3 ) 2 + ][CF 3 SO 3 − ]. This crystallizes in the centrosymmetric triclinic space group P 1 ( C i 1 ; No. 2) with a 11.708(2), b 11.738(2) c 14.702(2) A, α 87.544(13), β 79.181(14), γ 76.963(15)°, V 1933.4(6) A 3 and D (calcd) 1.64 g cm −3 for mol. wt. 951.9 and Z = 2. x-ray diffraction data (Mo- K α , 2θ 4.5–50.0°) were collected with a Syntex P2 1 automated four-circle diffractometer and the structure was refined to R 3.5% for all 6835 reflections ( R 2.9% for those 6133 reflections with | F 0 | > 6σ(| F 0 |)). The central d 6 iridium(III) ion has a slightly distorted octahedral stereochemistry, with Ir-CO 1.943(5) and 1.956(5) A, Ir-CH 3 2.152(5) and 2.155(5) A and Ir-PPh 3 2.391(1) and 2.400(1) A; interligand angles include OC-Ir_CO 102.09(20), CH 3 -Ir-CH 3 89.70(19) and PPh 3 -Ir-PPh 3 174.68(4)°.

Synthesis and crystals structure of a carbomethoxy complex of pentacoordinate iridium(I), MeOC(O)Ir(CO)2(PPh3)2

The pentacoordinate complex MeOC(O)Ir(CO) 2 (PPh 3 ) 2 , prepared by carbonylation of trans -MeOIr(CO)(PPh 3 ) 2 , crystallizes in the centrosymmetric triclinic space group P with a 10.019(2), b 11.828(3), c 16.578(5) A, α 103.83(2), β 92.71(2), γ 114.27(2)°, V 1715(1) A 3 and Z = 2. Diffraction data were collected and the structure was solved and refined to R 4.9% for 4504 reflections with 2θ = 4.5–45.0° (Mo- K α ), and R 3.6% for those 3768 data with | F 0 | > 6σ(| F 0 7z.sfnc;). The iridium(I) atom is in a trigonal-bipyramidal coordination environment. Axial bond lengths are Ir-CO 2 Me 2.073(9) and Ir-P(2) 2.360(2) A; equatorial bond lengths are Ir-P(1) 2.392(2), Ir-CO(1) 1.891(8) and Ir-CO(2) 1.895(10) A. Isomerism in trigonal-bi-pyramidal molecules is discussed.

Catalytic homogeneous hydrogenation of terminal olefins by RCo(CO)2(P(OCH3)3)2 (R = CH3 or CH3C(O))

Abstract The complexes RCo(CO) 2 L 2 (R = CH 3 , CH 3 C(O), L = P(OCH 3 ) 3 ) show a marked activity (450 turnovers/h) for hydrogenation of terminal olefins at ambient conditions. There is very little activity for more hindered olefins. A number of reactions have been examined, which allow a mechanism for the catalytic cycle to be presented. This mechanism involves a series of methyl → acetyl interconversion which open coordination sites, very similar to η 3 · η 1 allyl interconversions.

Reaction of alkenes with trans-MeOIr(CO)(PPh3)2. Crystal and molecular structure of the pentacoordinate alkoxy-alkene iridium(I) complex, MeOIr(CO)(PPh3)2(TCNE)

Abstract The reaction of trans -MeOIr(CO)(PPh 3 ) 2 with TCNE (tetracyanoethylene) gives rise to the stable adduct MeOIr(CO)(PPh 3 ) 2 (TCNE), the structure of which has been determined via a single-crystal X-ray diffraction study. This complex crystallizes in the centrosymmetric orthorhombic space group Pbca ( D 15 2 h ; No. 61) with a 17.806(4), b 20.769(4), c 20.589(6) A, V 7614(3) A 3 and Z = 8. Diffraction data (Mo- K α , 2θ = 5–45°) were collected on a Syntex P2 1 automated four-circle diffractometer and the structure was solved and refined to R F 6.2% for 3502 data with | F 0 | > 3σ(| F 0 |) ( R F 4.3% for those 2775 data with | F 0 | > 6 σ(| F 0 |)). The central iridium atom has a distorted trigonal bipyramidal coordination geometry in which the methoxy group (Ir-OMe 2.057(8) A) and carbonyl ligand (Ir-CO 1.897(14) A) occupy axial sites with ∠MeOue5f8Irue5f8CO 174.7(4)°. The two triphenylphosphine ligands occupy equatorial sites (Irue5f8P(1) 2.399(3), Irue5f8P(2) 2.390(3) A, ∠P(1)ue5f8Irue5f8P(2) 110.32(11)° and the TCNE ligand is linked in an η 2 “face-on” fashion with the olefinic bond parallel to the equatorial coordination plane (Irue5f8C(4) 2.176(10), Irue5f8C(7) 2.160(12) A) and lengthened substantially from its value in the free olefin (C(4)ue5f8C(7) 1.539(17) A).

Addition of C2(CO2Me)2 to trans-MeIr(CO)(PPh3)2. Formation and isomerization of MeIr(CO)(PPh3)2[C2(CO2Me)2], and crystal structure of the thermodynamic isomer

The reaction of C 2 (CO 2 Me) 2 with trans -MeIr(CO)(PPh 3 ) 2 leads to a kinetic isomer which has been characterized by 1 H and 31 P NMR and infrared spectra and to a thermodynamic isomer which has been characterized by 1 H and 31 P NMR, infrared, microanalysis and X-ray crystallography. The isomerization occurs readily in solution at room temperature; somewhat more slowly at −20°C. The thermodynamically stable isomer of MeIr(CO)(PPh 3 ) 2 [C 2 (CO 2 Me) 2 ] crystallizes in the centrosymmetric monoclinic space group P 2 1 / c with a 14.847(2), b 16.648(2), c 15.656(3) A, β 90.595(14)°, V 3869.7(11) A 3 and Z = 4. Single-crystal X-ray diffraction data were collected with a Syntex P2 1 automated diffractometer (Mo- K α radiation, 2θ 5–40°) and the structure was solved and refined to R F 8.6% for all 3631 independent data ( R F 4.0% for those 2318 data with | F o | > 6σ(| F o |)). The Ir I center has a trigonal-bipyramidal environment with the methyl ligand and one PPh 3 ligand occupying axial sites (Ir-Me 2.193(14), Ir-P(1) 2.425(4) A). The C 2 (CO 2 Me) 2 ligand is π-bonded to the iridium atom and lies with its triple bond parallel to the equatorial coordination plane; the equatorial ligands are completed by the second PPh 3 ligand (Ir-P(2) 2.402(3) A) and a CO ligand (Ir-CO 1.812(15) A).