TY - JOUR
T1 - Phosphapentadienyl-Iridium-Phosphine Chemistry. Synthesis, Structure, and Spectroscopy of Phosphapentadienyl-Bridged Iridium Dimers
AU - Bleeke, John R.
AU - Rohde, Alicia M.
AU - Robinson, Kerry D.
PY - 1995/4
Y1 - 1995/4
N2 - The reactions of new lithium phosphapentadienide reagents with ClIr(PR3)3have been investigated. Treatment of ClIr(PEt3)3with lithium phosphapentadienide produced the phosphapentadienyl-bridged dimer [(μ-η1-phosphapentadienyl)Ir(PEt3)2]2 (1) as a 1.4:1 mixture of trans (1a) and cis (1b) isomers. The analogous reaction involving ClIr(PEt2Ph)3produced [(μ-η1-phosphapentadienyl)Ir(PEt2Ph)2]2 (2). Again, a 1.4:1 mixture of trans (2a) and cis (2b) isomers was obtained. The mechanism of trans → cis isomer conversion was probed by means of a “crossover” experiment: pure samples of trans isomers 1a and 2a were combined and their conversion to the equilibrium mixture of trans and cis isomers was monitored. The absence of “mixed-dimer” products (i.e., those containing both Ir(PEt3)2and Ir(PEt2Ph)2moieties) in these reactions ruled out a trans → cis isomerization mechanism involving monomeric (phosphapentadienyl)Ir(PR3)2units and supported a mechanism involving dissociation of one iridium–phosphido bond, inversion at the resulting terminal phosphido center, and re-formation of the iridium–phosphido bond. Treatment of ClIr(PEt3)3with lithium 2,4-dimethylphosphapentadienide generated [(μ-η1-2,4-dimethylphosphapentadienyl)Ir(PEt3)2]2(3). Again, an equilibrium mixture of trans (3a) and cis (3b) isomers was obtained, but the presence of the bulky dimethylphosphapentadienyl ligand led to a higher fraction of trans isomer (3a:3b = 8:1). The structure of 3a was confirmed by X-ray crystallography (triclinic, P1̅, a = 11.756(4) Å, b = 12.011(3) Å, c = 17.716(7) Å, α = 93.50(3)°, β = 92.89(3)°, γ = 108.67(3)°, V = 2359.0(15) Å3, Z = 2, R = 0.0277, Rw= 0.0345).
AB - The reactions of new lithium phosphapentadienide reagents with ClIr(PR3)3have been investigated. Treatment of ClIr(PEt3)3with lithium phosphapentadienide produced the phosphapentadienyl-bridged dimer [(μ-η1-phosphapentadienyl)Ir(PEt3)2]2 (1) as a 1.4:1 mixture of trans (1a) and cis (1b) isomers. The analogous reaction involving ClIr(PEt2Ph)3produced [(μ-η1-phosphapentadienyl)Ir(PEt2Ph)2]2 (2). Again, a 1.4:1 mixture of trans (2a) and cis (2b) isomers was obtained. The mechanism of trans → cis isomer conversion was probed by means of a “crossover” experiment: pure samples of trans isomers 1a and 2a were combined and their conversion to the equilibrium mixture of trans and cis isomers was monitored. The absence of “mixed-dimer” products (i.e., those containing both Ir(PEt3)2and Ir(PEt2Ph)2moieties) in these reactions ruled out a trans → cis isomerization mechanism involving monomeric (phosphapentadienyl)Ir(PR3)2units and supported a mechanism involving dissociation of one iridium–phosphido bond, inversion at the resulting terminal phosphido center, and re-formation of the iridium–phosphido bond. Treatment of ClIr(PEt3)3with lithium 2,4-dimethylphosphapentadienide generated [(μ-η1-2,4-dimethylphosphapentadienyl)Ir(PEt3)2]2(3). Again, an equilibrium mixture of trans (3a) and cis (3b) isomers was obtained, but the presence of the bulky dimethylphosphapentadienyl ligand led to a higher fraction of trans isomer (3a:3b = 8:1). The structure of 3a was confirmed by X-ray crystallography (triclinic, P1̅, a = 11.756(4) Å, b = 12.011(3) Å, c = 17.716(7) Å, α = 93.50(3)°, β = 92.89(3)°, γ = 108.67(3)°, V = 2359.0(15) Å3, Z = 2, R = 0.0277, Rw= 0.0345).
UR - https://www.scopus.com/pages/publications/0002796181
U2 - 10.1021/om00004a022
DO - 10.1021/om00004a022
M3 - Article
AN - SCOPUS:0002796181
SN - 0276-7333
VL - 14
SP - 1674
EP - 1680
JO - Organometallics
JF - Organometallics
IS - 4
ER -