From 2,9-dialkyl-1,10-phenanthrolines 1, complexes of several structures were made with Cu(I) chloride.These were examined in detail by 1H NMR and x-ray crystallog.Those with stoichiometry of two phenanthrolines per Cu atom have the known structure 2 containing a cation with distorted tetrahedral geometry about the Cu atom [(2,9-dialkyl-1,10-phenanthroline)2Cu]+Cl-.The alkyl groups of compounds 2 show a marked upfield change in the chem. shift with respect to the ligands themselves.This is ascribed to an aromatic ring current effect.The complexes with 1:1 stoichiometry can have either of two isomeric structures 3 and 4, depending upon the bulk of the alkyl groups in the 2 and 9 positions of the phenanthroline system, how they were prepared, and whether they are in solution or solid phase.Isomer 3, favored with bulky alkyl groups has the Cu atom in a distorted trigonal geometry with coordinated Cl and does not exhibit the ring-current effect seen in 2.The structures of two of these compounds were determined by x-ray crystallog.Crystals of 3f (2,9-di-tert-butyl-1,10-phenanthroline·CuCl) were tetragonal with space group P42/n and a 19.700(3), c 9.680(2) Å, and Z = 8.This structure shows substantial distortion from trigonal planar geometry, due to the steric bulk of the tert-Bu groups.Crystals of 3h (2,9-dineopentyl-1,10-phenanthroline·CuCl) were monoclinic with space group P21/c and a 9.545(2), b 18.407(3), c 12.734(2) Å, β 107.75(2)°, and Z = 4.Compounds 4 have NMR identical with 2, but are isomeric with 3, having the structure [(2,9-dialkyl-1,10-phenanthroline)2Cu]+CuCl2-.The structure of 4g ([(2,9-n-pentyl-1,10-phenanthroline)2Cu]+CuCl2-) was determined by x-ray crystallog.Crystals of 4g were triclinic, space group P1̅ with a 13.861(3), b 14.108(3) Å, α 65.35(2), β 107.75(2), γ 90.05(2)°, and Z = 2.This structure clearly shows the positions of the alkyl groups of each ligand directly above the face of the aromatic system of the other in a distorted tetrahedral geometry about Cu.