Pyrazolyl-bridged iridium dimers. 6.1 two-fragment, two-center oxidative addition of halogens and methyl halides to trans-bis(triphenylphosphine)dicarbonylbis(ju-pyrazolyl)diiridium(I)

Jerry L. Atwood, Stephen R. Stobart, Michael J. Zaworotko, Kathy A. Beveridge, Gordon W. Bushnell, Keith R. Dixon, Donald T. Eadie, Stephen R. Stobart

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Abstract

Reaction between trans-Ir(PPh3)2(CO)Cl and Na(pz) (pzH = C3N2H4, pyrazole) affords the scarlet diiridium complex [Ir(PPh3)(CO)(μ-pz)]2 (la) 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) Å; the latter is somewhat longer [3.290 (1) Å] in the orange-red hexane solvate (lb). 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)(μ-pz)]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) Å has been accompanied by formation of a metal-metal bond [Ir-Ir = 2.737 (1) Å] 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 structureis proposed having Me attached to Ir(l) and I to Ir(2); by contrast with MeBr, reaction is slower to give an unidentified mixture of products. Crystals of la are triclinic, space group PI: a = 9.992 (4), b = 10.402 (4), c = 20.278 (8) Å; α = 90.01 (4), β = 90.10 (4), γ = 105.13 (4)°. Modification lb crystallizes in P21/c: a = 15.528 (4), b = 9.713 (3), c = 30.544 (8) Å; 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) Å β = 95.82 (2)°.

Original languageEnglish
Pages (from-to)4050-4057
Number of pages8
JournalInorganic Chemistry
Volume23
Issue number24
DOIs
Publication statusPublished - Jan 1984
Externally publishedYes

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