108270-60-6Relevant articles and documents
Photochemically generated transients from κ2- and κ3-Triphos derivatives of group 6 metal carbonyls and their reactivity with olefins
Kyran, Samuel J.,Muhammad, Sohail,Knestrick, Matthew,Bengali, Ashfaq A.,Darensbourg, Donald J.
, p. 3163 - 3170 (2012/06/04)
The synthesis and characterization of (κ2-Triphos)M(CO) 4 derivatives, where M = Mo, W and Triphos = MeC(CH 2PPh2)3, are reported. Photolyses of these metal carbonyls in dichloromethane or CO2-saturated dichloromethane readily afford the (κ3-Triphos)M(CO)3 complexes with no evidence of significant solvent or carbon dioxide interactions with the site vacated by CO. However, in the presence of 1-hexene a transient (κ2-Triphos)M(CO)3(1-hexene) adduct was observed, which subsequently releases the olefin with formation of the stable κ3-tricarbonyl species. In the case of M = W the kinetic parameters for this process were assessed, with the rate of olefin replacement being inversely proportional to [1-hexene]. A dissociative rate constant of 25.6 ± 1.1 s-1 at 298 K was determined for olefin loss, with the selectivity for 1-hexene vs free phosphine arm addition to the unsaturated intermediate being somewhat surprisingly large at 22. The activation parameters measured were δH? = 26.1 ± 0.4 kcal/mol and δS? = 36 ± 3 eu, which are consistent with a dissociative substitution reaction. The kinetic parameters for this transformation were unaffected in the presence of excess quantities of CO 2. Although no interaction of CO2 with the transient species resulting from CO loss in the κ2 complex was noted on the time scale of 50 ms, an intermediate described as an η2- HSiEt3 complex was observed upon addition of triethylsilane. This latter transient species underwent dissociation with κ3-complex formation about 15 times as fast as its 1-hexene analogue. X-ray structures of the κ2 complexes of Mo and W where the dangling phosphine arm has undergone oxidation are also reported.
Steric and electronic effects of mono- and tridentate phosphine ligands on the basicities of the metal in tungsten tris(phosphine) tricarbonyl complexes
Sowa Jr., John R.,Zanotti, Valerie,Angelici, Robert J.
, p. 848 - 853 (2008/10/08)
Titration calorimetry has been used to determine the heats of protonation (ΔHHM) of the fac-W(CO)3(PR3)3 (PR3 = PMePh2 (1), PEtPh2 (2), PMe2Ph (3), PEt2Ph (4), PMe3 (5), PEt3 (6)) and fac-W(CO)3(L3) (L3 = PhP(CH2CH2PPh2)2 (7), MeC(CH2PPh2)3 (8)) complexes with CF3SO3H in 1,2-dichloroethane solvent at 25.0°C. The W(CO)3(PR3)3 and W(CO)3(L3) complexes undergo protonation at the tungsten with 1 equiv of CF3SO3H to form [W(H)(CO)3(PR3)3]CF3SO 3(1H+-6H+) and [W(H)(CO)3(L3)]CF3SO3(7H +,8H+), respectively. For the W(CO)3(PR3)3 (1-6) complexes, the metal basicity (-ΔHHM) generally increases as phosphine basicity (-ΔHHP) increases; the ΔHHM values range from -15.1 kcal mol-1 (PR3 = PMePh2) to -25.0 kcal mol-1 (PR3 = PEt3). However, the trend in the ΔHHM values is also influenced by the steric bulk of the phosphine ligand. Steric crowding in the fac-W(CO)3(PR3)3 complexes is relieved when the complexes are protonated and the phosphine ligands adopt a less crowded arrangement in which they are approximately coplanar with the metal; metal basicity increases as the cone angle (θ) of the phosphine increases. ΔHHM of the tridentate phosphine complex 8 (-10.5 kcal mol-1) with the facially coordinating MeC(CH2PPh2)3 ligand is 6.2 kcal mol-1 less exothermic than that of 7 (-16.7 kcal mol-1) with the flexible PhP(CH2CH2PPh2)2 ligand. The lower basicity of 8 is attributed to a destabilization of the 8H+ product, which is forced by the MeC(CH2PPh2)3 ligand to adopt a structure less favorable than that of 7H+. The ΔHHM values (-18.3 and-20.1 kcal mol-1, respectively) of the Cp*Re(CO)2(PR3) (PR3 = PMe2Ph (9), PMe3 (10)) complexes have also been determined.
W(CO)3(PMTA) (PMTA = MeN(CH2CH2NMe2)2) as a starting material for syntheses of W(CO)3(PR3)3, W(CO)3(η6-arene), and the protonated W(H)(CO)3(PR3)3+ complexes
Zanotti, Valerio,Rutar, V.,Angelici, Robert J.
, p. 177 - 191 (2007/10/02)
A new and improved method for the synthesis of M(CO)3(PMTA) (M = W, Mo) from M(CO)6 and PMTA (MeN(CH2CH2NMe2)2) is described.The tridentate nitrogen ligand in W(CO)3(PMTA) is replaced, under relatively mild conditions, by tertiary phosphines (PMe3, PEt3, PMe2Ph, PMePh2, PhP(CH2CH2PPh2)2, CH3C(CH2PPh2)3, and Ph2P(CH2)nPPh2 where n = 1, 2) and arenes (C6H6, MeC6H5, p-Me2C6H4, C6Me6, C6H5Cl), which provides a general synthetic method for the preparation of W(CO)3(PR3)3 and W(CO)3(η6-arene) complexes.The reactions of W(CO)3(L)3 with CF3SO3H in CH2Cl2 solution yield the hydrido derivatives W(H)(CO)3(L)3+ which were characterized by their 1H and 31P NMR spectra at different temperatures.These studies show the W(H)(CO)3(L)3+ complexes to be fluxional as a result of both hydride and phosphine ligand migration.
