Molecular structures of some tertiary phosphine betaines in their crystalline adducts

Article abstract of DOI:10.1016/S0022-2860(96)09348-9

Direct reaction of Ph₃P and Ph₂P(CH₂)₂PPh₂ with acrylic acid in AcOEt-acetone yielded the tertiary phosphine betaine triphenylphosphoniopropionate, ph₃P⁺(CH₂)₂CO; (L¹), and the novel double betaine ethylenebis(diphenylphosphoniopropionate) ^- O₂C(CH₂)₂Ph₂P⁺(CH₂)₂Ph₂P⁺(CH₂)₂CO₂/^-(L²), respectively. Reaction of Ph₃ P with fumaric acid in AcOEt/acetone did not afford the corresponding betaine derivative Ph₃P⁺CH(CO₂H)CH₂CO₂/^-, but decarboxylates to L¹ in situ. Four adducts of L¹, L² and Ph₃P⁺(CH₂)₃CO₂/^- (L³) have been prepared and characterized by single- crystal X-ray analysis. In L¹·2H₂O, 1, two betaine molecules are joined by donor hydrogen bonds from solvated H₂O molecules to form ten-membered rings which are further linked by hydrogen bonds to form chains extending parallel to [1 0 0]. In (HL¹)₂·(O₂CCH=CHCO₂)·HO₂CCH=CHCO₂H·2H₂O, 2, the fumaric acid molecules, fumarate anions and water molecules are interlinked by hydrogen bonds to form layers with an interlayer separation of 1/c* = 10.713(4) A; the HL¹ cations are sandwiched between adjacent layers and connected to them through hydrogen bonding. In L²·(CH₃)₂COγ5H₂O, 3, two independent L² molecules adopt different orientations and are cross-linked by hydrogen bonds with the water molecules to form layers with an interlayer spacing of 1/a* = 10.341(1) A; the (CH₃)₂CO molecules are sandwiched between adjacent layers. In [(HL³)₂(NO₃)]NO₃, 4, two independent HL³ cations are joined by one of the NO₃/^- group to form a dimeric cation.