237437-64-8Relevant articles and documents
Ruthenium complexes containing two Ru-(η2-Si-H) bonds: Synthesis, spectroscopic properties, structural data, theoretical calculations, and reactivity studies
Delpech, Fabien,Sabo-Etienne, Sylviane,Daran, Jean-Claude,Chaudret, Bruno,Hussein, Khansaa,Marsden, Colin J.,Barthelat, Jean-Claude
, p. 6668 - 6682 (2007/10/03)
The bis(dihydrogen) complex RuH2(H2)2(PCy3)2 (1) reacts with the disilanes (R2SiH)2X to produce the dihydride complexes [RuH2{(η2-HSiR2)2X}(PCy 3)2] (with R = Me and X = O (2a), C6H4 (3), (CH2)2 (4), (CH2)3 (5), OSiMe2O (6)) and R = Ph, X = O (2b)). In these complexes, the bis(silane) ligand is coordinated to ruthenium via two σ-Si-H bonds, as shown by NMR, IR, and X-ray data and by theoretical calculations. 3, 4, and 6 were characterized by X-ray diffraction. In the free disilanes the Si-H bond distances and the JSi-H values are around 1.49 A and 200 Hz, respectively, whereas in the new complexes the values are in the range 1.73-1.98 A and 22-82 Hz, respectively for the σ-Si-H bonds. The importance of nonbonding H...Si interactions, which control the observed cis geometry of the two bulky PCy3 ligands, is highlighted by X-ray data and theoretical calculations. The series of bis(silane) model complexes, RuH2{(η2-HSiR2) 2X}(PR′3)2, with X = (CH)2, C6H4, (CH2)n, O, and OSiH2O, and with R and R′ = H or Me, was investigated by density functional theory (DFT) by means of two hybrid functional B3LYP and B3PW91. In the case of X = C6H4 three isomers were studied, the most stable of which has C2v symmetry and whose structure closely resembles the X-ray structure of 3. Calculated binding energies for the bis(silane) ligand to the RuH2(PH3)2 fragment vary from 130 to 192 kJ/mol, showing that in the more stable complexes, the Si-H bonds are bound more strongly than dihydrogen. The dynamic behavior of these complexes has been studied by variable temperature 1H and 31P{1H} NMR spectroscopy and exchange between the two types of hydrogen is characterized by barriers of 47.5 to 68.4 kJ/mol. The effect of the bridging group X between the 2 silicons is illustrated by reactions of compounds 2-6 with H2, CO, tBuNC. 3 is by far the most stable complex as no reaction occurred even in the presence of CO, whereas elimination of the corresponding disilane and formation of RuH2(H2)2-(PCy3)2, RuH2(CO)2(PCy3)2, or RuH2(tBuNC)2(PCy3)2 were observed in the case of 2 and 4-6. The mixed phosphine complexes [RuH2{(η2-HSiMe2)2X}(PCy 3)(PR3)] 3R-6R (with R = Ph and R = pyl) have been isolated in good yields (80-85%) and fully characterized by the addition of 1 equiv of the desired phosphine to 3-6. In the case of 4Ph, an X-ray determination was obtained. In the case of 2, elimination of the disiloxane was always observed. Addition of 1 equiv of a disilane to Ru(COD)(COT) in the presence of 2 equiv of the desired phosphine under an H2 atmosphere produces the complexes [RuH2{(η2-HSiMe2)2X}(PR 3)2] (X = C6H4, R = Ph (3Ph2) and R = pyl (3pyl2); X = (CH2)2, R = Ph, 4Ph2; R = pyl, 4pyl2). 4Ph2 was also characterized by an X-ray structure determination.
