Rhodium and iridium complexes with 2-(diphenylphosphanyl)anilido ligands: reactions with phenylacetylene and dimethyl acetylenedicarboxylate †

Abstract

Treatment of [Ir(CO)(PPh₃)(‘PNMe’)] (‘PNMe’ = 2-Ph₂PC₆H₄NMe^–) with phenylacetylene resulted in oxidative addition and opening of the chelate ring to afford mono- and bis-(alkynyl) derivatives, [IrH(C[triple bond, length half m-dash]CPh)(CO)(PPh₃)(‘PNMe’)] 1 and [IrH(C[triple bond, length half m-dash]CPh)₂(CO)(PPh₃)(η¹-‘PN(Me)H’)] 2, respectively. Complex 2 exists as two isomers with trans-located phosphane ligands and cis- or trans-coordinated alkynyl groups. The minimum values of the spin–lattice relaxation times, T₁^(min), observed for the hydride ligands of the two isomers ruled out the possibility of short IrH  · · ·  HN contacts in 2. Combination of [Ir(CO)(PPh₃)(‘PNMe’)] with dimethyl acetylenedicarboxylate (dmad) gave the irida(III)cyclopropene-like complex [Ir{C₂(CO₂Me)₂}(CO)(PPh₃)(‘PNMe’)] 3 as the expected 1∶1 adduct. In contrast, [Rh(CO)(PPh₃)(‘PNMe’)] and dmad interacted by insertion of the activated alkyne into the Rh–N bond, forming the seven-membered metallaheterocycle [Rh{C(CO₂Me)[double bond, length half m-dash]C(CO₂Me)N(Me)C₆H₄PPh₂-2}(CO)(PPh₃)] 4. [Ir(CO)(PPh₃)(‘PNH’)] (‘PNH’ = 2-Ph₂PC₆H₄NH^–) and dmad reacted to initially produce a mixture of metallacyclic [Ir{C₂(CO₂Me)₂}(CO)(PPh₃)(‘PNH’)] 5 and unchanged starting materials. Subsequent treatment with methanol resulted in the formation of the iridium(III) complex [Ir{C(O)OMe}{C(CO₂Me)[double bond, length half m-dash]CH[C(O)OMe]}(PPh₃)(‘PNH’)] 6, which X-ray crystallography showed to contain a chelating vinyl ligand featuring substantial carbenoid character.

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