Axial additions in nickel(II) complexes of (5SR,7RS,12RS,14SR)-tetra-methyl-1,4,8,11-tetra-azacyclotetradecane (L_α) and crystal-structure analysis of the planar orange and octahedral violet perchlorate salts NiL_α,(ClO₄)₂

Abstract

Reduction of the nickel (11) complex of C-meso-5,7,12,14-tetramethyl-l,4,8,11 -tetra-azacyclotetradeca-4,11diene with NaBH, gives predominantly the nickel(l1) complex of the title ligand, La. Both orange (1) and violet (2) isomers of NiLa(C10J2 have been characterised and structures established by X-ray crystallography. Crystals of (1) are monoclinic. space group P2,lc with two formula units in a unit cell of dimensions a = 8.244(1), b = 8.656(1), c = 16.701 (1) A, and p = 110.28(1)". Crystals of (2) are triclinic, space group P'i with two formula units in a cell of dimensions a = 10.645(1), b = 8.298(1), c = 14.198(2) A, 01 = 121.36(1), p = 94.61 ( l ) , and y = 82.77(1)". Both structures were solved by the heavy-atom method and refined by full-matrix least-squares calculations. For (1 ), R = 0.036 for 2 434 observed reflections; for (2), R = 0.043 for 1 924 observed reflections. Orange complex (1) contains ionic perchlorate with the closest Ni O contact 2.808(5) A. In the centrosymmetric square-planar cation the Ni-N distances are 1.964(3) and 1.974(3) A. The purple complex (2) contains two independent discrete half molecules (2a) and (2b) lying on inversion centres in the asymmetric unit, both with axially bound perchlorate. Principal distances are Ni-0 2.235(3) and 2.221 (2) A and Ni-N 2.063(2)-2.081(2) A. The metal complexes have the trans Ill arrangement of the chiral nitrogen centres, with the four methyl groups equatorial. The complex [NiL,J2+ undergoes axial additions with unidentate ligands (HzO, Br-, CI-, NCS-, N3-, NO2-, 02CMe-) and trans-[NiLX2]"+ have been prepared and characterised. Infrared and d-d spectra are reported. The equilibrium [NiLJ2+ + 2H20 + [NiLa(OH2)2]2+ha~ been studied over a temperature range, yielding K = 5.06 at 25 "C with AH* = -22.1 kJ m o l -l and A S ' = -60.6 J K -l mol-l. KOLINSKI A N D KORYBUT-DASZKIEWICZ first described the nickel(I1) complexes of the macrocyclic ligand 5,7,12,14tetramet hyl-1,4,8,11-t etra-azac yclo t et radeca-4,11 -diene (I) (=L). The ligand contains two chiral carbon centres at C7 and C14 so that C-rac (11) and C-meso (111) diastereo- C-meso ( R , S

Structure of [Ni(Me8[14]aneCα)](ClO4)2 (Me8[14]ane = 2,5,5,7,9,12,12 14-octamethyl-1,4,8,11-tetraazacyclotetradecane)

“…Apart from these distances, there are no untoward inter-ion contacts. The centrosymmetric cation has (necessarily) trans-square-planar coordination with Ni--N distances 1.961 (2) and 1.948 (3)A in accord with values reported previously (Curtis, Swann & Waters, 1973;Hay, Jeragh, Ferguson, Kaitner & Ruhl, 1982 the C--C and C--N distances are in the normal ranges for such molecules (Hay, Pujari, KorybutDaszkiewicz, Ferguson & Ruhl, 1989, and references therein). The unique six-membered ring adopts a slightly flattened chair conformation, with the N--H moieties axial.…”

“…1), with normal N...O distances in the range 2.992 (18) to 3-204 (5) A (Table 2). In contrast to what was found in (IV) (Hay, Jeragh, Ferguson, Kaitner & Ruhl, 1982), no perchlorate oxygen is directly bonded to nickel. Apart from these distances, there are no untoward inter-ion contacts.…”

[(5SR,7RS,12RS,14RS)-5,7,12,14-Tetramethyl-1,4,8,11-tetraazacyclotetradecane]nickel(II) Diperchlorate

“…The Ni--N distances are close to the average Ni--N distance of 1.95 (4) A, for four-coordinate Ni II macrocyclic complexes (Lu, Chung & Ashida, 1991). In both molecules A and B of the diastereoisomer (II) and in all three molecules of the diastereoisomer (I) (Hay et al, 1982), the conformations of the 14-membered rings are similar. All four perchlorate groups are disordered.…”

“…According to a previous report (Hay, Jeragh, Ferguson, Kaitner & Ruhe, 1982), the reduction of C- meso-5 , 7 ,12 ,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene at the 50% probability level (Sheldrick, 1987). Perchlorate anions and selected H atoms are excluded for clarity.…”

A Macrocyclic Nickel(II) Complex Salt Containing Six-Coordinate Nickel(II) Ions in a Different Coordination Environment

“…1,6 Although the equilibrium is susceptible to temperature, addition of salts, ionic strength, etc., it is difficult to shift the above equilibrium completely to the octahedral side.1,2,7 Therefore, the isolated macrocyclic nickel(II) complexes are usually square-planar, and this is especially true when the perchlorate or hexafluorophosphate salts are added to the aqueous solutions of macrocyclic nickel(II) complexes in equilibrium. Later, the successful isolation of a trans-diaqua octahedral nickel(II) cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) has been appeared with its solid state X-ray structure as well as single crystal visible spectrum by Mochizuki and Kondo.…”