Metallacrown ethers with trans-tetracarbonylmolybdenum(0) centers

Academic Article

Abstract

  • Photolysis of the cis-Mo(CO) {Ph P(CH CH O) CH CH PPh -P,P′}, (1, n = 3; 2, n = 4; 3, n = 5) metallacrown ethers in tetrahydrofuran under nitrogen gives moderate yields of the corresponding trans-Mo(CO) {Ph P(CH CH O) CH CH PPh -P,P′} (4, n = 3; 5, n = 4; 6, n = 5) metallacrown ethers. The trans-metallacrown ethers are also obtained when catalytic amounts of HgCl are added to chloroform solutions of the cis-metallacrown ethers. The 1 ⇄ 4 and 2 ⇄ 5 equilibria are established within 3 min at ambient temperature and approximately equal amounts of the cis- and trans-metallacrown ethers are present in the equilibrium mixtures. The 3 ⇄ 6 equilibrium is more complicated because HgCl complexation by 3 also occurs in these solutions. Addition of excess HgCl to the equilibrium mixture of 3 and 6 results in the formation of the previously reported cis-Mo(CO) {μ-Ph P(CH CH O) CH CH PPh -P,P′,O, O′,O″,O‴,O″″}HgCl . Comparison of the X-ray crystal structures of the trans-metallacrown ethers 4-6 and trans-Mo(CO) {Ph P(CH CH O) -1-C H -2-(OCH CH ) PPh -P,P′} (7) indicates that both ring size and flexibility affect the conformations of the metallacrown ether rings. The larger oxygen-oxygen distances in the trans-metallacrown ethers, compared with those in the corresponding cis-metallacrown ethers 1, 3 and cis-Mo(CO) {Ph P(CH CH O) -1-C H -2-(OCH CH ) PPh -P,P′} (8), may explain why the trans-metallacrown ethers have not been observed to bind strongly the hard metal cations. © 2001 Elsevier Science B.V. 4 2 2 2 n 2 2 2 4 2 2 2 n 2 2 2 2 2 2 4 2 2 2 5 2 2 2 2 4 2 2 2 2 6 4 2 2 2 2 4 2 2 2 2 6 4 2 2 2 2
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    Author List

  • Duffey CH; Lake CH; Gray GM
  • Start Page

  • 199
  • End Page

  • 210
  • Volume

  • 317
  • Issue

  • 1-2