Binding of Thioether Sulfur to Trivalent Chromium. A Family of CrS2N2O2 Complexes Derived from Acyclic Ligands

Hard–soft interactions in early transition-metal thioether macrocyclic chemistry: spectroscopic and extended X-ray absorption fine structure studies on chromium(III) thioether complexes

“…Reaction of [CrX 3 (thf ) 3 ] (X = Cl or Br, thf = tetrahydrofuran) with [9]aneS 3 or [10]aneS 3 in a 1 : 1 molar ratio in CH 2 Cl 2 solution gives the products [CrX 3 ([9]aneS 3 )] or [CrX 3 ([10]aneS 3 )] as powdered solids in high yield. Similarly, using [CrX 3 (thf ) 3 ] and [18]aneS 6 in a 2 : 1 molar ratio yields the binuclear species [(CrX 3 ) 2 (µ- [18]aneS 6 )]. We found that in order to promote coordination through the thioether donors it was necessary to remove the thf from the reaction mixture, otherwise the harder O-donor thf ligand would bind preferentially.…”

“…These results correlate very well with the average Cr᎐S, Cr᎐O or Cr᎐X distances derived from the X-ray crystallographic studies. 9, 25 For [CrX 3 ([9]aneS 3 )], [CrCl 3 ([10]aneS 3 )] and [(CrCl 3 ) 2 -(µ- [18]aneS 6 )] the EXAFS data were modelled for three sulfurs and three halogen atoms (Cl or Br as appropriate), while for cis-[CrBr 2 ([14]aneS 4 )]PF 6 two shells were modelled, one with four sulfurs and one with two bromides. For the complexes cis-[CrX 2 ([14]aneS 4 )]PF 6 no attempt was made to split the sulfur shell to take account of the slightly different distances expected for the Cr᎐S (trans to X) and Cr᎐S (trans to S) since X-ray structural studies have shown that the difference is very small (in this case only ca.…”

“…14 Very recently we have also reported the synthesis and crystal structure of the corresponding vanadium() species [VCl 3 ([9]aneS 3 )] which also involves fac tridentate [9]aneS 3 co-ordination, giving V᎐S 2.486(3), 2.515(2), 2.500(2), V᎐Cl 2.279(3), 2.310(3), 2.281(3) Å. 15 The only structurally characterised examples of chromium() thioether macrocyclic species are [CrCl 3 ([18]aneS 6 )] ( [18]aneS 6 = 1,4,7,10,13,16-hexathiacyclooctadecane) which involves fac tridentate co-ordination of the hexathia crown to Cr III , leaving three free thioether donors (see text below) 8 and cis-[CrCl 2 ([14]aneS 4 )]PF 6 ([14]aneS 4 = 1,4,8,11-tetrathiacyclotetradecane), the structure of which we have reported, involving S 4 Cl 2 co-ordination at Cr III with Cr᎐S 2.393(1), 2.407(2), Cr᎐Cl 2.295(1) Å. 9 We now report the preparation and spectroscopic characterisation of a series of chromium() thioether macrocyclic complexes incorporating [9]aneS 3 , [10]aneS 3 (1,4,7trithiacyclodecane), [14]aneS 4 , [16]aneS 4 (1,5,9,13-tetrathiacyclohexadecane) and [18]aneS 6 , together with chromium K-edge extended X-ray absorption fine structure (EXAFS) studies on selected examples.…”

“…In their system the metal ion is encapsulated by an N 5 S donor caging ligand which enforces the thioether co-ordination [Cr᎐S 2.399(2) Å]. Chakravorty and coworkers 18 have reported the preparation of a series of octahedral chromium() compounds involving S 2 N 2 O 2 chelating ligands, including a crystal structure of one example which shows d(Cr᎐S) = 2.417(3) and 2.445(3) Å. Both of these systems involve much harder donor sets than those of the present macrocyclic thioether complexes.…”

Chromium Complex Pre-Catalysts in Ethylene Oligomerization/Polymerization

“…A few highly selective catalytic systems have led to the trimerization of ethylene to 1-hexene, [33] one such example is the class of Cr(III) complexes containing thioether bonding. [34] McGuinness et al have studied Cr(III)-SNS complexes 63-66 (Scheme 10), which were found to be highly efficient catalysts for the trimerization of ethylene to 1-hexene. [14] Methyl 63 and ethyl 64 substituted complexes gave similar activities and selectivities.…”