Template syntheses based on tris (ethane-1,2-diamine)cobalt(III) lead to cobalt(III) complexes of cage hexamines of the ' sarcophagine ' type ( sarcophagine = sar = 3,6,10,13,16,19- hexaazabicyclo [6.6.6] icosane ) rapidly and in high yield. Reduction of these species to their cobalt(II) forms enables the ligands to be removed in concentrated acids at elevated temperatures, and in hot aqueous solutions containing excess cyanide ion. The free sarcophagine and 1,8-diaminosarcophagine [(NH2)2sar or diamsar] ligands are strong bases, accepting up to four and five protons, respectively, in aqueous solution. In chloride medium, I = 1.0, at 298 K, pK1 = 11.95, pK2 = 10.33, pK3 = 7.17, pK4 ≈ 0 for sarcophagine , and pK1 = 11.44, pK2 = 9.64, pK3 = 6.49, pK4 = 5.48, pK5 ≈ 0 for diaminosarcophagine , with very similar values being found for triflate medium. Crystal structure determinations for both free bases, the chloride, sulfate, perchlorate and nitrate salts of diamsar , the complex of zinc chloride with sar, and the magnesium nitrate complex with diamsar show remarkably small variations in the cavity defined by the bicyclic ligands, though relatively subtle bond length and bond angle changes can be rationalized in terms of the effects of proton and metal ion binding. Exhaustive methylation of sarcophagine produces the highly lipophilic, hexatertiary base hexamethylsarcophagine , which, in the solid state, adopts quite different conformations and nitrogen-atom configurations to those of sar itself. All the ligands rapidly form metal ion complexes of generally exceptional kinetic and thermodynamic stability.

The ligand sarcophagine (sar = 3,6,10,13,16,19-hexaazabicyclo 6.6.6 icosane) rapidly reacts with [Mn(0~2)6]~+ to form the nearly colourless [Mn(~ar)]'~ ion! which can readily be oxidized to the bright orange [~n ( s a r ) ]~+ ion (E0'+0.53 V v. n.h.e. in 0.1 moll-' CF3S03H at 295 K). A single-crystal structure determination on [Mn(sar)] (N03)3, space group I z2d, a 15-549(6), c 19.014(6) A, R 0.051, Rw 0.049 for 608 'observed' reflections, shows the coordination geometry of the manganese(111) ion, with site symmetry 2 , to be subject to a Jahn-Teller distortion, giving three pairs of Mn-N bond lengths of 2.18(1), 2.13(1) and 2.08(1) A. The [~n ( s a r ) ]~+ ion is stable in strongly acidic aqueous solutions, but in solutions of pH > 3 undergoes deprotonation and subsequent disproportionation reactions.The manganese (11) complex ion is less stable in acidic solutions, undergoing hydrolysis at a rate showing a first-order dependence on both proton and chloride ion concentrations. Both [Mn(sar)I2+ and [Mn(sar)13+ can be obtained in chiral forms, and the rate constant for electron self-exchange obtained by polarimetric measurements on solutions of mixtures of [Mn(sar)12+ and [Mn(sar)13+ of opposite chirality is 30 dm3 mol-I s-' at 298 K, I = 0.1 M. * sar represents 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane; (~~3 ) z s a r~' represents 1,8-reactivity by a factor >101° compared to [ C O ( O H~)~]~+ .~The magnitude of this effect is such that true kinetic inertness might also be expected for sarcophagine complexes of both transition and main Group metal ions such as Mg2+, Cr2+, Mn2+, Fe2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+, and our initial qualitative observations were consistent with this e~~e c t a t i o n .~We have now carried out detailed quantitative studies of most of these complex ion species and report herein characterization of the manganese system. * sar was extracted from [~o''(sar)]~+ ion by using hot aqueous NaCN or boiling concentrated HBr. The details of the extraction and the structures of various forms of the protonated ligand are in preparation. l1 Diebler, H., Eigen, M.

The syntheses of [ Mn ((NH3)2sar)](NO3)4.H2O and [ Mn ((NH3)2sar)](NO3)5.2H2O, manganese(II) and manganese(III) complexes of the cage amine ligand diaminosarcophagine ( di-aminosarcophagine = (NH2)2sar = 1,8-diamino-3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane ) in its diprotonated form are recorded, together with their single-crystal X-ray structure determinations at c. 295 K. The monoclinic P21 array of the manganese(II) complex (a 12.386(5), b 12.431(4), c 8.598(4) Ǻ, β 93.89(4)°, V 1321(1) Ǻ3,Z 2) is archetypical for similar complexes of a wide variety of transition metals; for the present determination, R was 0.027 for 2013 'observed' (I > 3σ(I)) reflections. The manganese(III) complex is monoclinic C 2/c, a 10.744(2), b 13.294(4), c 20.462(9) Ǻ, β 102.38(3)°, Z 4; R was 0.055 for 1629 'observed' reflections. Both structures show the six secondary nitrogen atoms of the ligand to be bound to the manganese ion in a configuration approximately halfway between a trigonal prism and an octahedron. The ligand is in the lel3 conformation. In the first complex, Mn -N distances, appropriate to high-spin manganese(II), range from 2.228(3) to 2.253(3) Ǻ, mean 2.238 Ǻ; in the second, surprisingly, the distances are even more closely ranged (unlike those of the sarcophagine analogue of the previous paper), 2.115(4)-2.127(4) Ǻ, the mean (2.122 Ǻ) being closely comparable to that recorded for the sar analogue, and show no appreciable variation attributable to the expected Jahn-Teller effect.

A synthesis of [( tren )Co(μ-NH2,μ-OH)Co( tren )]4+(3)( tren = tris (2- aminoethyl )amine) is reported along with a series of derivatives: [( tren ) XCo (μ-NH2) CoX ( tren )]n+, where X = CF3SO3- (n = 3)(4), X = CH3CN (n = 5)(5), and [( tren )Co(μ-NH2,μ-CH3C(O)NH)Co( tren )]4+ (6). The substitution of (4) by CH3CN to yield (5) was studied in CH3CN at 20°C, k = 9.0×10-3 s-1, and the intramolecular hydrolysis of (5) to yield the bridging acetamide complex (6) was studied at various acid concentrations. The X-ray crystal structures were determined for (3b) (exafluorophosphate, dihydrate) and (6b) (dithionate, tetrahydrate ). Both crystals are monoclinic, respectively P21/n with a 11.082(2), b 10.402(2), c 15.611(2)Ǻ, β 99.13(2)°, Z 2, and C2/c with a 14.328(2), b 14.046(1), c 16.497(2)Ǻ, β 101.90(1)°, Z 4. For the salt of (3), 2389 data with 1 ≥ 2σ(I) were refined to R 0.070 ( Rw 0.066), and, for the salt of (6), 3087 data with I ≥ 3σ(I) were refined to R 0.041 ( Rw 0.056). Both ions lie on pseudo-symmetric sites involving disorder of the bridging ligands . The structures establish the binding mode of the acetamido ion and the orientation of the tren groups in the isolated complexes.

The syntheses of complexes containing the [Ni( sar )]2+/3+ and [Ni((NH3)2sar)]4+ ions are described along with an X-ray crystal structure analysis of the salt [Ni((NH3)2sar)] (NO3)4.H2O ( sar is 3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane ; (NH3)2sar2+ is its 1,8-diammonio derivative). The NiIII ion is a powerful oxidant, with E′ = 0.90 V (v. n.h.e. at 298 K, I = 0.2, aqueous trifluoromethanesulfonate medium), but is relatively stable in dilute aqueous acid. Both the NiII and NiIII complexes of sar have been resolved into their enantiomeric forms, and their absorption, optical rotatory dispersion and circular dichroism spectra recorded and partly analysed. The electron self-exchange rate between enantiomeric forms in the different oxidation states has been measured by a stopped-flow circular dichroism method, and ket = (5.3�0.3)×103 dm3 mol-1 s-1 at 298 K, I = 0.2 (NaCF3SO3). The activation parameters, ΔH‡ 22�4 kJ mol-1 and ΔS‡ -100�12 J K-1 mol-1, and the rate constants are consistent with the comparatively small rearrangements required in the structures of the two ions relative to the optimal cavity radius for the cage of 2.05(1) Ǻ.