18399-61-6Relevant academic research and scientific papers
Reactions of M(CO)6 (M = Mo, W) with PPh2H and NaBH4
Keiter, Richard L.,Keiter, Ellen A.,Mittelberg, K. Neil,Scott Martin,Meyers, Victoria M.,Wang, Jin-Guu
, p. 1399 - 1403 (2008/10/08)
The reaction of M(CO)6 (M = Mo, W) with PPh2H and NaBH4 in high-boiling alcohols affords M(CO)5PPh2H (1), cis-M(CO)4(PPh2H)2 (2), fac-M(CO)3(PPh2H)3 (3), (OC)4M(μ-PPh2)2M(CO)4 (4), (OC)4M(μ-PPh2)2M(CO)3PPh 2H (5), trans-HPh2P(OC)3M(μ-PPh2) 2M(CO)3PPh2H (6), and cis-HPh2P-(OC)3M(μ-PPh2) 2M(CO)3PPh2H (7). Proper selection of the phosphine/metal carbonyl mole ratio optimizes the formation of 3, 5, or 6, and good yields of these products may be obtained. Complexes 1, 2, 4, and 7 are found as minor products. 31P NMR studies show that 1 and 2 are precursors to the phosphido-bridged complexes. A reaction sequence for the formation of observed products is proposed.
Reactions Leading to Formation and Cleavage of Metal-Metal and Metal-μ-Phosphido Bonds in Binuclear Molybdenum and Tungsten Complexes. Structural Analyses of W2(CO)8(μ-PPh2)2 and Its Two-Electron Reduction Product, 2
Shyu, Shin-Guang,Calligaris, Mario,Nardin, Giorgio,Wojcicki, Andrew
, p. 3617 - 3625 (2007/10/02)
Reduction of M2(CO)8(μ-PPh2)2 (M= Mo (1-Mo) or W (1-W)) and reactions of various binuclear molybdenumand tungsten anionic products were found generally to proceed with a remarkably facile scission or formation of M-M and M-(μ-PPh2) bonds.Thus, complexes 1 are converted by M'BR3H (M'= Li, R= Et; M'= K, R= sec-Bu) or LiAlH4 in THF to the M-M bond cleaved 2- (2) or to (3) depending on the nature and, usually the amount of the reductant.Reactions of 1 with LiR (R= Me (a), N-B (b), Ph (c)) afford the acyl anions (4a-c), of which yield the carbene complexes (5a,c) when treated with Me3OBF4.The M-M bond of 3 is readily broken by CO and n-BuLi to give - (6) and 2, respectively.Treatment of 3 with CF3COOH leads to a fragmentation of the binuclear unit with the formation of cis-M(CO)4(PPh2H)2 and M(CO)5(PPh2H).The dianions 2 are converted to the M-M bonded 3 and 4a when reacted with 1 equiv of CF3COOH and MeI (in THF or DMF), respectively.Possible mechanisms of these reactions are discussed.The structures of 1-W and its 2-electron reduction product,Li(THF)3+>22-W, were determined by single-crystal X-ray diffraction analyses.Both crystals are monoclinic of space group P21/c, with a= 9.830 (2) Angstroem, b= 19.802 (4) Angstroem, c= 16.889 (5) Angstroem, β= 103.72 deg, and Z= 4 for 1-W and a= 11.265 (5) Angstroem, b= 19.546 (3) Angstroem, c= 16.446 (5) Angstroem, β= 122.07 (3) deg, and Z= 2 for +>22-W.The structure of 1-W was solved and refined to R= 0.030 and RW= 0.33 by using 5206 independent reflections, whereas the structure of +>22-W was solved and refined to R= 0.051 and RW= 0.062 by using 3987 independent reflections.Both structures possess a planar W2P2 core.The W-W distance of 3.0256 (4) Angstroem in 1-W increases to a nonbonding value of 4.1018 (4) Angstroem in 2-W, and the W-P-W bond angles of 75.14 deg (mean) in 1-W widen to 104.20 deg in 2-W.The Li+ ion in +>22-W possesses an almost regular tetrahedral oxygen environment, being attached to three THF molecules and an equatorial CO of 2-W.
Reactions of M2(CO)8(μ-PPh2)2 (M = Mo or W) with BR3H- and LIR nucleophiles. Proton-induced cleavage of M-(μ-PPh2) bonds in binuclear anionic complexes
Shyu, Shin-Guang,Wojcicki, Andrew
, p. 809 - 812 (2008/10/08)
Reactions of M2(CO)8(μ-PPh2)2 (2, M = Mo or W) with 1 equiv of M′BR3H (M′ = Li or K; R = Et or sec-Bu) in THF proceed to [(CO)4M(μ-PPh2)M(CO)4-Scheme I (Chemical Equation Presented) (PPh2H)]- (3) and with 2 equiv of M′BR3H or LiAlH4, to [M2(CO)8(μ-PPh2)2]2- (4). Treatment of 4 with 1 equiv of CF3COOH in THF affords 3, whereas treatment of 3 with 1 equiv of CF3COOH yields cis -M(CO)4(PPh2H)2 and M-(CO)5(PPh2H) as major and minor products, respectively. Reactions of 2 with LiR (R = Me, n-Bu, and Ph) proceed regiospecifically to the equatorial isomers of [M2(CO)7-(COR)(μ-PPh2)2] -, which are alkylated by Me3O+BF4- to yield M2(CO)7[C(OMe)R] (μ-PPh2)2 (R = Me).
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.
