80471-11-0Relevant academic research and scientific papers
Pyrazolyl-bridged iridium dimers. 6. Two-fragment, two-center oxidative addition of halogens and methyl halides to trans-bis(triphenylphosphine)dicarbonylbis(μ-pyrazolyl)diiridium(I)
Atwood, Jerry L.,Beveridge, Kathy A.,Bushnell, Gordon W.,Dixon, Keith R.,Eadie, Donald T.,Stobart, Stephen R.,Zaworotko, Michael J.
, p. 4050 - 4057 (2008/10/08)
Reaction between trans-lr(PPh3)2(CO)Cl and Na(pz) (pzH = C3N2H4, pyrazole) affords the scarlet diiridium complex [Ir(PPh3)(CO)(μ-pz)]2 (1a) characterized by single-crystal X-ray crystallography, in which the terminal PPh3 and CO ligands are mutually trans across the Ir2 axis with a formally nonbonded Ir2 separation of 3.163 (2) A?; the latter is somewhat longer [3.290 (1) A?] in the orange-red hexane solvate (1b). A systematic synthesis of the same compound is described, in which reaction of [Ir(COD)Cl]2 with pzH giving the dimer [Ir(COD)(μ-pz)]2 (2) is followed by treatment with CO and PPh3 to provide 1 in 82% yield. Reaction of 1 with Ir2 and Br2 leads to formation of yellow complexes formulated as 1-1 adducts formed by a two-center oxidative addition, i.e. [Ir(PPh3)(CO)(X)(μpz)]2 (X = I, Br); with Cl2 the corresponding product has been characterized crystallographically as [Ir(PPh3)(CO)(Cl)(4-Cl-pz)]2 (9) in which the trans configuration of 1 is retained Axial substitution at each Ir with Ir-Cl = 2.443 (6) A? has been accompanied by formation of a metal-metal bond [Ir-Ir = 2 737 (1) A?] and electrophilic substitution by Cl of the 4-position in each bridging pyrazolyl-ring system. Reaction between 1 and Mel affords a yellow 1:1 adduct (80% yield) for which a corresponding dimeric structure is proposed having Me attached to Ir(1) and I to Ir(2); by contrast with MeBr, reaction is slower to give an unidentified mixture of products. Crystals of 1a are triclinic, space group P1: a = 9.992 (4), b = 10.402 (4), c = 20.278 (8) A?; β = 90.01 (4), β = 90.10 (4), γ = 105.13 (4)°. Modification 1b crystallizes in P21/c: a = 15.528 (4), b = 9.713 (3), c = 30.544 (8) A?; β = 93.98 (2)°. For the addition product (9), the space group is P21/n: a = 15.851 (3), b = 28.617 (4), c = 11.092 (2) A?; β = 95.82 (2)°.
