Synthesis and characterization of [Pd2X2(μ-X)2{Ph2P(CH2CH2O)nCH2CH2PPh2-P,P′}]m (n = 3, 5, X = Cl, I) dimetallacrown ethers and the related dinuclear [Pd2Cl2(μ-Cl)2{Ph2P(CH2)12PPh2-P,P′}]m and [Pd2X2(μ-X2){Ph2P(CH2CH2O)2CH2CH3-P)2}] (X = Cl, I) complexes

Abstract

Reactions of the metallacrown ethers, [PdCl₂{PPh₂(CH₂CH₂O)_nCH₂CH₂PPh₂-P,P′}]_m (n = 3, 5), with PdCl₂ or Pd(PhCN)₂Cl₂ yield the new dimetallacrown ethers, [Pd₂Cl₂(μ-Cl)₂{PPh₂(CH₂CH₂O)_nCH₂CH₂PPh₂-P,P′}]_m (n = 3 (3), n = 5 (4)). Similar reactions of [PdCl₂{PPh₂(CH₂)₁₂PPh₂-P,P′}]_m and [PdCl₂{PPh₂(CH₂CH₂O)₂CH₂CH₃-P}₂] with PdCl₂ or Pd(PhCN)₂Cl₂ yield [Pd₂Cl₂(μ-Cl₂){PPh₂(CH₂)₁₂PPh₂-P,P′}]_m (5) and [Pd₂Cl₂(μ-Cl)₂{PPh₂(CH₂CH₂O)₂CH₂CH₃-P}₂] (6), respectively. The chloride-bridged dimetallacrown ethers, 3 and 4, are cleanly converted into the iodide-bridged dimetallacrown ethers, [Pd₂I₂(μ-I)₂{PPh₂(CH₂CH₂O)_nCH₂CH₂PPh₂-P,P′}]_m (n = 3 (7), n = 5 (8)) by reaction with excess NaI. In solution, 3 and 4 exist as mixtures of syn monomers and cyclic oligomers while 7 and 8 exist as mixtures of both syn and anti monomers and cyclic oligomers. The solid state structures of syn-[Pd₂I₂(μ-I)₂{PPh₂(CH₂CH₂O)₃CH₂CH₂PPh₂-P,P′}] (syn-7) and of anti-[Pd₂I₂(μ-I)₂{Ph₂P(CH₂CH₂O)₂CH₂CH₃)₂-P}₂} (anti-9) have been determined. These structures are consistent with the major species present in the solutions. They also suggest that syn-7 experiences ring-strain, which is consistent with the results from the ³¹P{¹H} NMR studies.