Dono r-stab ilized hyper coordinated silic on (IV) chelat es wi th cyclohe xylid en eimino-N ligand gr ou p: Rol e of substi tuents on i oni zatio n (original) (raw)
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The Journal of Organic Chemistry, 2002
Aryl benzyl oximes having the configuration Z give rise to stereolabile atropisomers when a halogen atom is present in the ortho position of the aryl moiety, as a consequence of the restricted aryl-CN bond rotation. By means of dynamic 1 H NMR spectroscopy it has been possible to determine the corresponding rotation barrier, hence the lifetime of the atropisomers that, in the case of the iodine derivative, was found sufficiently long as to allow a physical separation to be achieved on an appropriately cooled enantioselective HPLC column. Comparison of the barriers determined by dynamic NMR and dynamic HPLC proved the equivalence of the two techniques. When the iodine atom was substituted by an R-naphthyl group, two dynamic processes were observed. That with the lower barrier could be determined by NMR and that with the higher barrier by HPLC, thus outlining the complementarity of these two techniques. † Università "La Sapienza". ‡ University of Bologna. § Università "G. D'Annunzio". (1) Part 88: Bartoli, G.; Grilli, S.; Lunazzi, L.; Massaccesi, M.; Mazzanti, A.; Rinaldi, S. de Meijere, A.; Kozhushkov, S. I.; Lunazzi, L.; Mazzanti, A. J. Am. Chem. Soc., in press. (3) Leardini, R.; Lunazzi, L.; Mazzanti, A.; McNab, H.; Nanni, D.
Organometallics, 1993
The silane [ 2-(MezNCHz)C&] ZSiClz (7) shows a new dynamic N**&-N "flip-flop" coordination mode below T, = 233 K (AG* = 46.5 (f0.5) kJ mol-l) with both amine donors displacing each other. 7 is pentacoordinated in the solid state; crystal data: orthorhombic, Paca, a = 13.802(1) A, b = 17.908(1) A, c = 15.544(2) A, Z = 8. Reaction of the silanes C~H~[~-(M~ZNCHZ)C~H~]S~C~P (61, 7, and [~-(M~Z N C H Z)-~-(~-C~H~) C~H~~Z S~C~Z (8) with chromiumpentacarbonylmetallate yields the silanediyl complexes [~-(M~zNCHZ)C~H~IC~H~S~=C~(CO)B (111, [2-(Mez-N C H Z) C~H~] zSi=Cr(CO)5 (12), and 12-(M~zNCHZ)-~-(~-C~H~)C~H~I zSi=Cr(CO)s (13); 12-(Mez-N C H Z) C~H~] H S~= C~(C O)~ (14) was obtained by photolytic methods. Silanediyl complexes with one chelating donor show a rigid coordination of the donor to silicon which can be lifted at higher temperatures (95 'C for 11, AG* = 80.4 (*0.5) kJ mol-'). A single crystal X-ray structure determination of 11 reveals a CrSi bond distance of 2.409(1) A and a N-Si bond length of 1.991(2) A. Crystal data: triclinic, Pi, a = 9.401(1) A, b = 10.207(1) A, c = 11.586(1) A, Z = 2. Silanediyl complexes with two intramolecular donor functions feature a dynamic "flip-flop" coordination of the amine groups to silicon. Both (dimethy1amino)phenyl groups in 12 and 13 can be detached from silicon under liberation of a three-coordinate silicon atom at T, = 58 'C (VTJH-NMR), AG* = 67.1 (f0.5) kJ mol-l for 12 and T, = 61 'C, AG* = 70.1 (k0.5) kJ mol-' for 13. A single crystal X-ray structure determination of 12 gives 2.408(1) A for the Si-Cr bond length and 2.046(2) A for the N1-Si dative bond (the second contact N2-Si has a nonbonding distance of 3.309 A; the sum of bond angles at silicon amounts to 351.3'). Crystal data: triclinic, Pi, a = 9.531(1) A, b = 10.339(1) A, c = 11.676(1) A, Z = 2. The donor in 12 has been functionalized at the nitrogen atom by protonation or complexation with BF3. Photolysis of 12 and 13 leads to a 1,2-amine shift of one donor from silicon to the metal with loss of CO. The product [2-(Me~NCHz)c6H31 [2-(MezrjCHz)C6H3] Si=Cr(CO)r (20) has been characterized by a single crystal X-ray structure determination and has a bond distance Cr-Si 2.3610(4) A and N1-Si 1.981(1) A. Crystal data: monoclinic, P21/c, a = 10.344(5) A, b = 11.761(3) A, c = 18.96(1) A, Z = 4. Furthermore, the silanediyl complex 12 has been immobilized on silica gel. IR and UV spectroscopy and 13C CPMAS NMR provide evidence for the fixation of (silica-0-) [~-(HNM~zCHZ)C~H~~[~-(M~ZNCHZ)C~H~~ Si=Cr(CO)s (22) to the surface via the silicon atom. Reaction of 13 with HzO leads to (HO) [~-(H N M~z C H Z) C~H~I [~-(M~Z N C H Z) C~H~I S~-Cr(CO)5 (23) which has a structure similar to 22 with a Cr-Si bond length of 2.469(2) A. The dimethylamino or dimethylammonium substituent is pointing away from the silicon atom forming hydrogen bridges between Nl-*HO*-HN2; crystal data: monoclinic, P&/n, a = 13.198(2) A, b = 17.017(2) A, c = 17.066(1) A, Z = 4.
Configurationally Stable Molecular Propellers: First Resolution of Residual Enantiomers
Angewandte Chemie International Edition, 2006
General procedure for the preparation of phosphine oxides 1a-c: A mixture of phosphorus oxybromide (1 mmol) and pyridine (9 mmoles) was added to the suitable N-methyl-2-alkylindole (3.8 mmoles) under nitrogen. The reaction mixture was heated at 90°C under stirring for 18 h, then diluted with dichloromethane and the resulting solution exhaustively extracted with a 1N HCl solution. The organic layer was washed with H 2 O, dried over Na 2 SO 4 and evaporated to dryness to give a residue which was chromatographed on a silica gel column to separate the phosphine oxide 1 from unreacted N-methyl-2-alkylindole, which was eluted first. Tris[3-(1,2-dimethylindolyl)]phosphine oxide (1a): 1,2-Dimethylindole (Aldrich [875-79-6]: 5.78 g; POBr 3 : 2.85 g; pyridine (6 mL). Chromatography eluant: CH 2 Cl 2 /EtOH 9.5:0.5. The product was crystallized from a 1:3 mixture of CHCl 3 /EtOAc. M.p. 270°C, 63% isolation yields; 1 H NMR (CDCl 3 , 300 MHz) δ = 7.29 (broad d, J = 8.1 Hz, 1H), 7.08 (td, J 1 = 7.4 Hz and J 2 = 1.4 Hz, 1H), 6.72 (td, J 1 = 8.1 Hz and J 2 = 1.1 Hz, 1H ), 6.67 (broad d, J = 7.4 Hz, 1H), 3.71 (s, N-CH 3 ), 2.57 (d, J = 1.34 Hz, CH 3 ) ; 31 P NMR (CDCl 3 , 300 MHz) δ = 8.33 (s); 13 C NMR (CDCl 3 , 300 MHz) δ = 145.34 (d, J = 18 Hz), 137.25 (d, J = 11.25 Hz), 128.67 (d, J = 12 Hz), 120.96 (s), 120.47 (s), 120.21 (s), 108.81 (s), 105.15 (d, J = 132 Hz), 29.58 (s), 12.24 (s); HRMS (EI) calcd for C 30 H 30 N 3 OP: [M] + 479.212651, found 479.213100. Tris[3-(2-ethyl-1-methylindolyl)]phosphine oxide (1b). 2-Ethyl-1-methylindole: 2.08 g;
Adv. Synth. Catal. 2015, 357, 3463 –
Thed evelopment of am ethod that employs at wo-chamber reaction vessela nd usesm olybdenum hexacarbonyl [Mo(CO) 6 ]a st he carbon monoxide (CO) source for the palladium-catalyzed transformation of nitroarenes into indoles or imidazoles is reported. Thes cope andl imitations of our method are illustrated with 23 examples.E xperiments that indicatet he mechanism of the C À H bond amination reactiont ob es tepwisea re also reported.
European Journal of Inorganic Chemistry, 2010
The anionic dinitrile ligand dicyanonitrosomethanide (dcnm), C(CN) 2 (NO) -, and the anion resulting from its addition product with water, carbamoylcyanonitrosomethanide (ccnm), C(CN)(CONH 2 )(NO) -, have been incorporated into lanthanoid complexes and display unusual η 2 (N,O) nitroso coordination modes. (Et 4 N) 3 [Ln(ccnm) 6 ] (1Ln; 1Ln = 1La, 1Ce, 1Pr, 1Nd, 1Sm) and (Me 4 N) 3 [Ln(ccnm) 6 ] (2Ln; 2Ln = 2La, 2Ce, 2Pr, 2Nd) are systems containing 12-coordinate homoleptic trianionic lanthanoidate complexes. The nitroso groups of the ccnm ligands form three-membered ring chelates with the lanthanoid metal centre, with the asymmetry of the nitroso η 2 interactions dependent upon the intramolecular N-H···O=N hydrogen bonding. Additional intermolecular hydrogen bonding interactions exist between adjacent amide and nitrile groups giving rise to 3D α-Po and 6,8connected (4 12 .6 3 )(4 20 .6 8 ) networks in 1Ln and 2Ln, respectively. The compounds (Me 4 N) 3 [Ln(dcnm) 6 ] (3Ln; 3Ln = 3La, 3Ce, 3Nd, 3Sm) also contain a 12-coordinate trianionic lan-
Adv. Synth. Catal. 2015, 357, 3463 –3468.pdf
Thed evelopment of am ethod that employs at wo-chamber reaction vessela nd usesm olybdenum hexacarbonyl [Mo(CO) 6 ]a st he carbon monoxide (CO) source for the palladium-catalyzed transformation of nitroarenes into indoles or imidazoles is reported. Thes cope andl imitations of our method are illustrated with 23 examples.E xperiments that indicatet he mechanism of the C À H bond amination reactiont ob es tepwisea re also reported.