Chemistry in Interphases: Chemical Exchange in a Polysiloxane-Bound Chlorohydridotris(ether-phosphine)ruthenium(II) Complex. An Investigation by Solid-State NMR Spectroscopy
作者:Ekkehard Lindner、Martin Kemmler、Theodor Schneller、Hermann A. Mayer
DOI:10.1021/ic00126a019
日期:1995.10
The reaction between HRuCl(PPh(3))(3) (2) and the ether-phosphine ligands R(Ph)PCH2CH2OCH3 [1a, 1b(T-0)], R(Ph)PCH2-tetrahydrofuryl [1c, 1d(T-0)] (R = Ph (a,c), CH2CH2CH2Si(OMe)(3) [b(T-0), d(T-0)] (for labeling see Table 1) affords the monomeric ruthenium complexes HRuCl(P similar to O)(2)(PO) [3a, c, 3b(T-0)(3), 3d(T-0)(3)] [P similar to O: eta(1)-P-coordinated, PO: eta(2)-PO-coordinated; T-0 = T type (T-0 = -Si(OMe)(3)) silicon atoms without Si-O-Si bonds]. Variable temperature P-31H-1} NMR spectroscopic investigations, which have been carried out in detail in the case of 3a, give evidence of fluxional behavior. In the presence of water and catalytic amounts of NEt(3) the monomeric precursors HRuCl(P similar to O)(2)(PO) [3b(T-0)(3), 3d(T-0)(3)] are subjected to a polycondensation (sol-gel process) to give the corresponding polysiloxane- (T-) bound (ether-phosphine)ruthenium(II) complexes 3b'(T-n)(3) and 3d'(T-n)(3) [(T-n): T type silicon atoms; n = 1-3 (number of Si-O-Si bonds)]. Solid-state Si-29 CP-MAS NMR spectroscopy has been used to establish a highly cross-linked polysiloxane matrix in the case of the polycondensated complex HRuCl(P similar to O)(2)(PO) [3d'(T-n)(3)]. According to P-31H-1} NMR and P-31 CP-MAS NMR spectra the complex geometry is retained on going from the monomers HRuCl(P similar to O)(2)(PO) [3b(T-0)(3), 3d(T-0)(3)] to the corresponding polymers 3b'(T-n)(3), 3d'(T-n)(3). If HRuCl(P similar to O)(2)(PO) [3d'(T-n)(3)] (stationary phase) is treated with methanol (mobile phase) a swollen gel is formed. The ruthenium complex in this interphase [3d'(T-n)(3) + CH3OH] shows a chemical exchange of the three ether oxygen donors (equivalence of all three P atoms) which has been demonstrated by P-31 and C-13 solid-state NMR spectroscopy. Temperature dependent measurements establish these findings. If HRuCl(P similar to O)(2)(PO) [3b(T-n)(3) and 3d'(T-n)(3)] are reacted with acetic acid and carbon monoxide to give the polysiloxane-bound complexes ClRu(O(2)CMe)(P similar to O)(3) [4b'(T-n)(3), 4d'(T-n)(3)] and HRuCl(CO)-(P similar to O)(3) [5b'(T-n)(3), 5d'(T-n)(3)], respectively, the exchange process is prevented by cleavage of the Ru-O bond. The complexes HRuCl(CO)(P similar to O)(3) [5b(T-n)(3), 5d'(T-n)(3)] reversibly take up carbon monoxide with formation of the supported complexes HRuCl(CO)(2)(P similar to O)(2) [6b'(T-n)(2), 6d'(T-n)(2)].