cis-Mo(CO)4{Ph2P(CH2CH2O)nCH2CH2PPh2} (n = 3–5) Metallacrown Ethers. X-ray Crystal Structure of cis-Mo(CO)4{Ph2P(CH2CH2O)3CH2CH2PPh2}

Academic Article

Abstract

  • A series of Ph2P(CH2CH2O).,CH2CH2PPh2 (1, n = 3; 2, n = 4; 3, n = 5) ligands and their cis-Mo(CO)4{Ph2P- (CH2CH2O)nCH2CH2PPh2} (4, n = 3; 5, n = 4; 6, n = 5) complexes have been prepared. Multinuclear NMR and IR spectroscopic studies of these complexes indicate that a single Mo complex, with the ligands cis coordinated to the Mo through the PPh2 groups, is formed with each ligand. The complexes have been titrated with LiBF4 and NaBPh4, and the titrations have been followed by 31P NMR spectroscopy. These studies indicate that 5 binds much more strongly to Li+ than to Na+, but 6 binds more strongly to Na+ than to Li+. Bimetallic complexes were isolated from the titration solutions. With 6, 1:1 adducts were obtained with both LiBF4 and NaBPh4, whereas with 5, a 1:1 adduct was obtained with LiBF4 and a 2:1 adduct was obtained with NaBPh4. These results demonstrate that the metallacrown ethers exhibit definite size selectivities toward the alkali-metal cations. The cis-Mo- (CO)4(Ph2P(CH2CH2O)nCH2CH2PPh2) (n = 3–5) complexes react with methyllithium and phenyllithium to yield cis-Mo- (CO)4(Ph2PCH=CH2)2. This result is surprising because related Mo(CO)4 complexes of bis(phosphinite)- and bis(phos- phite)-polyether ligands react with methyllithium and phenyllithium to yield acetyl and benzoyl complexes, respectively. The X-ray crystal structure of cis-Mo(CO)4{Ph2P(CH2CH2O)3CH2CH2PPh2} (4) is also reported. The complex crystallizes in the monoclinic space group P21/n (a = 22.219 (1), b = 14.8175 (4), c = 10.680 (1) Å; β = 98.523°; V = 3477.2 Å3; z = 4). The molybdenum is in a slightly distorted octahedral coordination geometry with a P–Mo–P angle of 93.78 (2)°. The metallacrown ether ring is distorted from the symmetric solution conformation primarily due to different rotations of the diphenylphosphino groups about the molybdenum-phosphorus bonds. The three oxygens in the metallacrown ether are at the vertices of an isosceles triangle, and the plane formed by these oxygens is perpendicular to that formed by the molybdenum and the two phosphorus atoms. © 1991, American Chemical Society. All rights reserved.
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    Author List

  • Varshney A; Gray GM
  • Start Page

  • 1748
  • End Page

  • 1754
  • Volume

  • 30
  • Issue

  • 8