Molecular structures of some tertiary phosphine betaines in their crystalline adducts

Abstract

Direct reaction of Ph 3P and Ph 2P(CH 2) 2PPh 2 with acrylic acid in AcOEt-acetone yielded the tertiary phosphine betaine triphenylphosphoniopropionate, Ph 3P +(CH 2) 2CO − 2 (L 1), and the novel double betaine ethylenebis(diphenylphosphoniopropionate) −O 2C(CH 2) 2Ph 2P +(CH 2) 2Ph 2P +(CH 2) 2CO − 2(L 2), respectively. Reaction of Ph 3P with fumaric acid in AcOEt/acetone did not afford the corresponding betaine derivative Ph 3P +CH(CO 2H)CH 2CO − 2, but decarboxylates to L 1 in situ. Four adducts of L 1, L 2 and Ph 3P +(CH 2) 3CO − 2 (L 3) have been prepared and characterized by single-crystal X-ray analysis. In L 1·2H 2O, 1, two betaine molecules are joined by donor hydrogen bonds from solvated H 2O molecules to form ten-membered rings which are further linked by hydrogen bonds to form chains extending parallel to [1 0 0]. In (HL 1) 2·(O 2CCHCHCO 2)·HO 2CCHCHCO 2H·2H 2O, 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 HL 1 cations are sandwiched between adjacent layers and connected to them through hydrogen bonding. In L 2·(CH 3) 2CO·5H 2O, 3, two independent L 2 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(a) A ̊ ; the (CH 3) 2CO molecules are sandwiched between adjacent layers. In [(HL 3) 2(NO 3)]NO 3, 4, two independent HL 3 cations are joined by one of the NO − 3 group to form a dimeric cation.