Pyrazolyl-Bridged Iridium Dimers. 18.¹ Influence of Metal−Metal Bonding on the Geometry of Diiridium(II) Adducts and Hydrido-diiridium Complexes Formed from the Diiridium(I) Prototype [Ir(μ-pz)(PPh₃)(CO)]₂ (pzH = Pyrazole) by Dihydrogen Addition or Protonation

Abstract

Slow uptake of molecular dihydrogen by the diiridium(I) prototype [Ir(mu-pz)(PPh(3))(CO)](2) (1: pzH = pyrazole) is accompanied by formation of a 1,2-dihydrido-diiridium(II) adduct [IrH(mu-pz)(PPh(3))(CO)](2) (2), for which an X-ray crystal structure determination reveals that (unlike in 1) the PPh(3) ligands are axial, with the hydrides occupying trans coequatorial positions across the Ir-Ir bond (2.672 A). Reaction with CCl(4) effects hydride replacement in 2, affording the monohydride Ir(2)H(Cl)(mu-pz)(2)(PPh(3))(2)(CO)(2) (3) in which Ir-Ir = 2.683 A. At one metal center, H is equatorial and PPh(3) is axial, while at the other, Cl is axial as is found in the symmetrically substituted product [Ir(mu-pz)(PPh(3))(CO)Cl](2) (4) (Ir-Ir = 2.754 A) that is formed by action of CCl(4) on 1. Treatment of 1 with I(2) yields the diiodo analogue 5 of 4, which reacts with LiAlH(4) to afford the isomorph Ir(2)H(I)(mu-pz)(2)(PPh(3))(2)(CO)(2) (6) of 3 (Ir-Ir = 2.684 A). Protonation (using HBF(4)) of 1 results in formation of the binuclear cation Ir(2)H(mu-pz)(2)(PPh(3))(2)(CO)(2)(+) (7: BF(4)(-) salt), which shows definitive evidence (from NMR) for a terminally bound hydride in solution (CH(2)Cl(2) or THF), but 7 crystallizes as an axially symmetric unit in which Ir-Ir = 2.834 A. Reaction of 7 with water or wet methanol leads to isolation of the cationic diiridium(III) products [Ir(2)H(2)(mu-OX)(mu-pz)(2)(PPh(3))(2)(CO)(2)]BF(4) (8, X = H; 9, X = Me).

Light-Emitting Self-Assembled Materials Based on d8 and d10 Transition Metal Complexes

“…70 X-ray structure determination showed that the two PPh 3 ligands would axially coordinate to the iridium(II) metal centers, while the hydrides would occupy the trans coequatorial positions along the intramolecular Ir(I)•••Ir(I) bond, the distance of which was determined to be 2.672 Å. 70 Further reaction with CCl 4 would replace the hydride to afford the monohydride complex, [Ir 2 (PPh 3 ) 2 (CO) 2 (μ-pz) 2 H(Cl)], with an intramolecular Ir-(I)•••Ir(I) separation of 2.683 Å. As evidenced by the X-ray crystal structure, the hydride was equatorial and the triphenylphosphine was in axial position of one of the metal centers.…”

“…As evidenced by the X-ray crystal structure, the hydride was equatorial and the triphenylphosphine was in axial position of one of the metal centers. 70 However, at another metal center, the chloride would be axial as found in the symmetrically substituted product, [Ir(Cl)(PPh 3 )(CO)(μ-pz)] 2 (Ir(I)•••Ir(I) distance = 2.754 Å), that was formed by the reaction of [Ir(PPh 3 )(CO)(μ-pz)] 2 with CCl 4 . 70 Bis(carbonyl)acetylacetonatoiridium (I), [Ir(CO) 2 (acac)], is another class of well-known complexes that has been utilized as a precursor in the preparation of metal films and coatings via chemical vapor deposition (CVD).…”

“…70 However, at another metal center, the chloride would be axial as found in the symmetrically substituted product, [Ir(Cl)(PPh 3 )(CO)(μ-pz)] 2 (Ir(I)•••Ir(I) distance = 2.754 Å), that was formed by the reaction of [Ir(PPh 3 )(CO)(μ-pz)] 2 with CCl 4 . 70 Bis(carbonyl)acetylacetonatoiridium (I), [Ir(CO) 2 (acac)], is another class of well-known complexes that has been utilized as a precursor in the preparation of metal films and coatings via chemical vapor deposition (CVD). 71 Needle-shaped single crystals with light yellow color were obtained by zone sublimation in a furnace under vacuum.…”

Protonation Reactions of Dinuclear Pyrazolato Iridium(I) Complexes

“…Previous examples of the protonation reactions of dinuclear iridium complexes include the reactions of [Ir 2 (μ-L) x (CO) 2 (PR 3 )] (L = Pz, x = 2; L = 1,8-diamidonaphthalene, x =1) with HBF 4 . The resulting cationic mono-hydride compounds were found to be active species for the addition of dihydrogen, water, and methanol . We describe in this paper the preparation of unusual dihydride Ir(III)/Ir(III) complexes and the striking influence of the chloride versus trifluoroacetic anions in the stabilization of intermediate Ir(II)/Ir(II) or Ir(I)/Ir(III) monoprotonated complexes.…”

Synthesis and characterization of two new types of oxovanadium complexes with pyrazole as ligand

“…-V(1)-N(5) 85.66(14) O(1)-V(1)-N(7) 91.29(15) O(1)-V(1)-N(1) 94.32(14) O(2)-V(1)-N(7) 87.41(13) O(2)-V(1)-N(1) 86.87(13) N(5)-V(1)-N(7) 90.22(14) N(5)-V(1)-N(1) 172.34(16) N(1)-V(1)-N(7) 91.12(14) O(1)-V(1)-N(3) 93.35(15) N(3)-V(1)-N(7)175.32(16) …”