Macrocyclic copper(II) chelate derivatives of 2,9-bis(methoxymethyl)-2,9-dimethyl-4,7-dioxadecanedioic and 2,2,9,9-tetramethyl-4,7-dithiadecanedioic acids. The crystal and molecular structures of aqua, pyridine, and triphenylphosphine adducts of [2,9-bis(methoxymethyl)-2,9-dimethyl-4,7-dioxadecanedioato]copper(II)

Abstract

The preparation of 2,9-bis(methoxymethyl)-2,9-dimethyl-4,7-dioxadecanedioic acid (1; H₂Y) as a mixture of diastereomers is reported, as is its conversion into the macrocyclic, carboxylate-bridged, dimeric copper(II) derivatives [{CuYL}₂][L = water (2), no ligand (3), pyridine (4), or triphenylphosphine (5)]. Each of these has been obtained in two forms, namely (2a)–(5a) in which the carboxylate ligand is present in both DL and meso forms and (2b)–(5b) which contain only the meso form. Spectral data (i.r. and u.v.–visible) are discussed. Structures have been determined from diffractometer data for compounds (2a), (4b), and (5b) which crystallise in the triclinic space group P with Z= 1. Unit cell dimensions are: a= 11.506(4), b= 7.149(2), c= 13.085(3)Å, α= 101.01 (1), β= 114.06(2), γ= 90.85(2)° for (2a); a= 11.230(4), b= 9.940(4), c= 10.954(4)Å, α= 112.16(3), β= 107.26(3), γ= 81.22(3)° for (4b); and a= 14.593(1), b= 10.747(1), c= 11.894(2)Å, α= 75.025(6), β= 115.011(6), γ= 99.567(6)° for (5b). The structures were solved by Fourier and Patterson methods and refined by full-matrix least-squares calculations to final R values of 0.078, 0.084, and 0.061 respectively. In all cases, the molecule is located around a crystallographic centre of symmetry and contains two copper atoms bridged by four carboxylate groups. The Cu–Cu distances are 2.626(2), 2.655(1), and 2.676(1)Å for the aqua, pyridine, and triphenylphosphine complexes respectively. For the pyridine and triphenylphosphine complexes, the dicarboxylate ligand is exclusively meso whereas the considerable disorder observed in the aqua complex indicates the presence of a mixture of D, L, and meso forms. The conversion of 2,2,9,9-tetramethyl-4,7-dithia-decanedioic acid (6) into Cu(O₂CCMe₂CH₂SCH_2^–)₂·L [L = 0–1 H₂O (7) or pyridine (8)] is also described. It is suggested, on the basis of spectral and solubility properties, that these complexes have similar macrocyclic structures to those derived from (1).