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• 135394-60-4 bis-(2-((dimethylamino)methyl)phenyl)dichlorosilane 

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Reversible intramolecular base stabilization in silylene (silanediyl) complexes: Surprising reactivity for silylene coordination compounds with a dynamic N?Si?N bond

The silane [2-(Me2NCH2)C6H4] 2SiCl2 (7) shows a new dynamic N?Si?N "flip-flop" coordination mode below Tc = 233 K (ΔG? = 46.5 (±0.5) kJ mol-1) with both amine donors displacing each other. 7 is pentacoordinated in the solid state; crystal data: orthorhombic, Pbca, a = 13.802(1) A?, b = 17.908(1) A?, c = 15.544(2) A?, Z = 8. Reaction of the silanes C6H5[2-(Me2NCH2)C6H 4]SiCl2 (6), 7, and [2-(Me2NCH2)-5-(t-C4H9)C 6H3]2SiCl2 (8) with chromiumpentacarbonyl-metallate yields the silanediyl complexes [2-(Me2NCH2)C6H4]C6H 5Si=Cr(CO)5 (11), [2-(Me2-NCH2)C6H4] 2Si=Cr(CO)5 (12), and [2-(Me2NCH2)-5-(t-C4H9)C 6H3]2Si=Cr(CO)5 (13); [2-(Me2-NCH2)C6H4]HSi=Cr(CO) 5 (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, ΔG? = 80.4 (±0.5) kJ mol-1). 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, P1, 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 (dimethylamino)phenyl groups in 12 and 13 can be detached from silicon under liberation of a three-coordinate silicon atom at Tc = 58°C (VT-1H-NMR), ΔG? = 67.1 (±0.5) kJ mol-1 for 12 and Tc = 61°C, ΔG? = 70.1 (±0.5) kJ mol-1 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, P1, 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-(Me2NCH2)C6H3][2-(Me 2NCH2)C6H3]Si=Cr(CO)4 (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-O-)[2-(HNMe2CH2)C6H 4][2-(Me2NCH2)C6H 4]Si=Cr(CO)5 (22) to the surface via the silicon atom. Reaction of 13 with H2O leads to (HO)[2-(HNMe2CH2)C6H4][2-(Me 2NCH2)C6H4]Si-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 N1?HO?HN2; crystal data: monoclinic, P21/n, a = 13.198(2) A?, b = 17.017(2) A?, c = 17.066(1) A?, Z = 4.