η3-1,3,5-triazacyclohexane complexes of tribenzylchromium(III)

Chromium(0) tricarbonyl complexes of 1,3,5-triazacyclohexanes

“…Suggestions that the longer Cr᎐N distances in the R = Bu t adduct may be a consequence of steric strain are tenuously based also: contacts are found between carbonyl oxygen atoms and the substituent methyl groups which lie to either side at O ؒ ؒ ؒ H distances of ≈2.6 Å, but there is little substantive evidence in other parameters of the system to support the notion that it is unduly sterically strained. Within [CrL 3 (C 3 H 6 N 3 R 3 )] arrays the ring torsion angles are surprisingly uniform and insensitive to changes in R or L, lying close to 67Њ (Tables 1 and 2); in the variety of structural characterisations carried out on (non-disordered) free More far-ranging comparisons of interest about Cr as the central metal atom are possible with related systems, in which the carbonyl groups may be replaced by benzyl, in combination with bulky R = cyclohexyl, as in [Cr(CH 2 Ph) 3 (tctach)], 3 or by chloride, as in [CrCl 3 (tnbtacn)] with the n-butyl-substituted tacn offering a different 'cone angle'. 16 Average values for these compounds in comparison with the present systems are given in Table 2.…”

Single-site heterogeneous Cr-based catalyst for the selective trimerisation of ethylene

“…1 compares the electronic spectra of complex 1 and of the heterogeneous system 2. The molecular structure of 1 has been described in literature 7 at around 28 000 cm 21 can also be noted. It was also found that species 2 can be transformed into complex 1 by treating the solid with a saturated hydrochloric acid gas stream.…”

“…1 compares the electronic spectra of complex 1 and of the heterogeneous system 2. The molecular structure of 1 has been described in literature 7 and consists of a regular octahedron CrN 3 Cl 3 containing Cr III , which gives rise to two well-defined d-d transitions at 13 900 and 19 700 cm 21 . The third allowed d-d transition is overshadowed by an intense charge transfer transition located at 38 000 cm 21 .…”

Chromium complexes of hydroxyl-functionalised 1,3,5-triazacyclohexanes

“…Since 1990 there has been much research concerned with the preparation and properties of η 3 -1,3,5-triazacyclohexane (tach) metal complexes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Although the literature dealing with triazacyclohexanes is extensive and triazacyclohexanes bearing functional groups (e.g. hydroxyl, allyl, nitro, nitrile, esters, amides, pyridyl) 18 are well known, studies of the co-ordination chemistry of this family of ligands has been limited to 1,3,5triazacyclohexanes with simple substituents (e.g.…”