title: Copper(II) complexes of novel N-alkylated derivatives of cis,cis-1,3,5-triaminocyclohexane. 1. Preparation and structure.
abstract: Novel N,N',N' '-trialkylated derivatives of cis,cis-1,3,5-triaminocyclohexane (tach), designated tach-R(3), were prepared through alkylation of N-protected tach with subsequent acid deprotection, to afford N-methyl, N-ethyl, and N-n-propyl derivatives as their trihydrobromide salts. The tach-neopentyl(3) and tach-furan(3) derivatives were prepared by formation of the imine from tach and pivaldehyde or furan-2-carboxaldehyde, respectively, followed by reduction of the imine. Complexes [Cu(tach-R(3))Cl(2)] (R = Me, Et, n-Pr, CH(2)-2-thienyl, and CH(2)-2-furanyl) were prepared from CuCl(2) in MeOH or MeOH-Et(2)O solvent. Crystallographic characterization of [Cu(tach-Et(3))Br(0.8)Cl(1.2)] (Pnma, a = 8.2265(1) A, b = 12.5313(1) A, c = 15.3587(3) A, Z = 4) reveals a square-based pyramidal CuN(3)X(2) coordination sphere in which one nitrogen donor occupies the apical position at a slightly longer distance (Cu-N = 2.218(5) A) than those of the basal nitrogens (Cu-N = 2.053(2) A). The solution-phase (pH 7.4 buffered and methanol) and solid-phase structures of [Cu(tach-R(3))Cl(2)] have been studied extensively by EPR and visible-near-IR spectroscopies. The square-based pyramidal structure is retained in solution, according to correspondence of solution and solid-state data. In aqueous solution, halide is replaced by water, as indicated by the high-energy UV-vis spectral shifts and bonding parameters of [Cu(tach-Et(3))](2+)(aq) derived from EPR data. The proposed aqueous-phase species, in the pH range 7.4 to 10.1, is [Cu(tach-Et(3))(H(2)O)(2)](2+). The complex [Cu(tach-Me(3))](2+)(aq) does not appear to dimerize or form metal-hydroxo species at pH 7.4, in contrast to other Cu(II)-triamine complexes, e.g., [Cu(1,4,7-triazacyclononane)](2+) (aq) and [Cu(tach-H(3))](2+)(aq) (the complex of unalkylated tach). This difference is attributed to the steric effect of the N-alkyl groups in the tach-R(3) series.
authors.affiliation: Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, USA.
authors.forename: G
authors.initials: G
authors.lastname: Park
authors.forename: J
authors.initials: J
authors.lastname: Shao
authors.forename: F H
authors.initials: FH
authors.lastname: Lu
authors.forename: R D
authors.initials: RD
authors.lastname: Rogers
authors.forename: N D
authors.initials: ND
authors.lastname: Chasteen
authors.forename: M W
authors.initials: MW
authors.lastname: Brechbiel
authors.forename: R P
authors.initials: RP
authors.lastname: Planalp
mesh_terms: D000478:Alkylation; D003300:Copper / Q000737:chemistry*; D003514:Cyclohexylamines / Q000737:chemistry*; D015394:Molecular Structure; D013057:Spectrum Analysis / Q000379:methods
chemical_list: C421444:1,3,5-triaminocyclohexane; D003514:Cyclohexylamines; D003300:Copper