18399-60-5Relevant articles and documents
Smith, J. G.,Thompson, D. T.
, (1967)
The reaction chemistry of transition-metal diphenylphosphorus complexes with organoaluminum compounds. The synthesis, characterization, and crystal and molecular structure of Cr(CO)5[PPh2(CH2)4OAl(CH 2SiMe3)2], an example of THF cleavage
Tessier-Youngs,Youngs, Wiley J.,Beachley Jr.,Churchill, Melvyn Rowen
, p. 1128 - 1138 (2008/10/08)
Metathetical and small molecule elimination reactions between appropriate transition-metal carbonyl diphenylphosphorus complexes and organoaluminum compounds have been investigated as synthetic routes to transition-metal derivatives of amphoteric ligands. The synthesis, characterization, and properties of the starting compounds for the metathetical reactions M(CO)5PPh2K·n(dioxane) (M = Cr, W, n = 2; M = Mo, n = 1) from M(CO)5PPh2H and KH are described. All data confirm that the dioxane molecules in these complexes retain their identity as cyclic ethers. Subsequent reactions of Cr(CO)5PPh2K·2(dioxane) with AlR2Br (R = Br, Me, Et, CH2SiMe3) in THF lead to the formation of high yields of fully characterized compounds with the empirical formula Cr(CO)5[PPh2(CH2)4OAlR2]. The (CH2)4O unit arises from the cleavage of the THF molecule. No THF-aluminum adducts are observed. The compound Cr(CO)5-[PPh2(CH2)4OAl(CH 2SiMe3)2] which incorporates a new amphoteric ligand has also been characterized by an X-ray structural study. The crystal is composed of dimeric units of formula [Cr(CO)5[PPh2-(CH2)4OAl(CH 2SiMe3)2]]2 which are in the centrosymmetric monoclinic space group P21/n with a = 11.939 (3) A?, b = 14.940 (A?), c = 21.014 (5) A?, β= 102.88 (2)°, V = 3654 A?3, Z = 2 (dimeric units), and mol wt 1301.5. Diffraction data (20(max) = 35°, Mo Kα radiation) were collected with a Syntex P21 automated four-circle diffractometer, the structure was solved by Patterson and difference-Fourier techniques, and the model was refined to RF = 9.2% and RwF = 8.2% for 1515 reflections with |Fo| > 3σ(|Fo|). The dimeric molecule lies on an inversion center. Each octahedral (OC)5CrPPh2- fragment is linked by an -(CH2)4O-unit (formed by cleavage of THF) to the two Al(CH2SiMe3)2 fragments. The central Al-O-Al-O ring is strictly planar, with obtuse Al-O-Al angles of 100.3 (6)° and acute O-Al-O angles of 79.7 (5)°. The second route to chromium derivatives of amphoteric aluminum-phosphorus ligands, small molecule elimination reactions between Cr(CO)5PPh2H and AlMe3 or AlMe2H, does not lead to compounds with Cr-P-Al bonds. Our observations suggest that the major site of reaction for the aluminum compounds is the carbonyl ligand.
1H, 13C and 31P NMR studies of some (C6H5)3-nPRn and (C6H5)3-nPRnCr(CO)5 (n=0-3; R=H, CH3, C2H5, i-C3H7, t-C4H9) derivatives
Vincent, E.,Verdonck, L.,Kelen, G. P. van der
, p. 699 - 704 (2007/10/02)
The 31P chemical shift of the (C6H5)3-nPRn and (C6H5)3-nPRnCr(CO)5 (n=0-3; R=H, CH3, C2H5, i-C3H7, t-C4H9) derivatives is dominated by the steric effect.A small inductive effect is also operative but there are no indications of notable (dCrdp)? back-bonding.The 13C chemical shift of the phenyl carbon atons indicates that (pring-dp)? electron delocalization is unimportant.The 13C chemical shift of the carbonyl atoms, which is mainly governed by the mean excitation energy, confirms the conclusion that there are no notable changes in (dCrdp)? back-bonding in this series of compounds.
