SYNTHESIS AND COORDINATION CHEMISTRY OF TRIFUNCTIONAL PHOSPHONO-BIS-CARBONYL ALKANE LIGANDS

Trifunctional ligands, 1-phosphono-1-carbamoyl-n-alkyl ester alkanes [(RO)2P(O)][C(O)NEt2]C(H)[(CH2)n-C(O)OR'] (n = 1-3) were prepared from metathesis reactions of the metallated anions [(RO)2P(O)][C(O)NEt2]CH- and bromoalkyl esters. The ligands were fully characterized and selected coordination chemistry with La(III), Er(III), UO22+ and Th(IV) was examined. The molecular structures of three coordination complexes were determined by single crystal X-ray diffraction techniques. The 1:1 complex, Er(NO3)3{[(i-PrO)2P(O)][C(O)NEt2]CH[(CH2)2C(O)OMe]}, Crystallizes in the monoclinic space group, P2(1)/c with a = 9.418(4), b=15.547(7), c = 18.259(8) angstrom, beta = 92.29(4)-degrees, Z = 4, V = 2671(2) angstrom3 and rho(calc) = 1.787 g cm-3. The structure was solved by heavy atom methods and full matrix least-squares refinements converged at R(F) = 3.52% and R(wF) = 4.84% on 4086 reflections with F > 6sigma(F). The compound forms a polymeric structure in which each Er(III) is nine-coordinate. The Er atom is bonded to three bidentate nitrate ions and the bidentate carbamoylmethyl phosphonate fragment of one trifunctional ligand. It is also bridge bonded to the ester carbonyl group in a second molecular unit. The 2:1 complex, Er(NO3)3{[(i-PrO)2P(O)][C(O)NEt2]CH[(CH2)2C(O)OMe]}2, crystallizes in the monoclinic space group P2(1)/n with a = 16.090(8), b = 19.114(9), c = 17.166(8) angstrom, beta = 108.01(4)-degrees, Z = 4, V = 5021(4) angstrom3 and rho(calc) = 1.434 g cm-3. The structure was solved by direct methods and refinement converged at R(F) = 4.00% and R(wF) = 4.89% on 5109 independent reflections with F > 6sigma(F). The compound contains isolated molecules in which the Er(III) is nine-coordinate and bonded to three bidentate nitrate ions, the bidentate carbamoylmethyl phosphonate fragment of one ligand and the phosphonate of a second ligand. The 1:1 complex, UO2(NO3)2{[(i-PrO)2P(O)][C(O)NEt2]CH[(CH2)3C(O)OEt]}, crystallizes in the monoclinic space group P2(1)/c with a = 8.855(2), b = 16.257(5), c = 20.603(6) angstrom, beta = 92.07(2)-degrees, Z = 4, V = 2964(1) angstrom3, rho(calc) = 1.765 g cm-3. The structure was solved by direct methods and refinement converged at R(F) = 7.82% and R(wF) = 7.77% on 3906 independent reflections with F > 3sigma(F). The compound contains a linear UO22+ ion bonded to two bidentate nitrate ions and the bidentate carbamoylmethyl phosphonate fragment of the trifunctional ligand. The structures of these complexes are compared with structural data for complexes containing related 1-phosphono-1-carbamoyl-n-carbamoyl alkanes and 1,1-bis-phosphono-n-carbamoyl alkanes.