Oxygen and chlorine atom transfer between tungsten, molybdenum, and rhenium complexes. Competition between one- and two-electron pathways

X-ray Absorption Spectroscopy Systematics at the Tungsten L-Edge

“…The 1 H and 31 P NMR chemical shifts respond to the paramagnetism of the compounds. 28 The W II complex possesses a (t 2g ) 4 electron configuration, although a spin ground state cannot be applied given the large spin–orbit contribution from the 5d metal. A similar description is pertinent to [W IV Cl 4 (PMePh 2 ) 2 ], which exhibits a nonzero magnetic moment due to mixing of paramagnetic excited states by spin–orbit coupling, 54 a situation routinely encountered for octahedral d 2 species.…”

“…Literature procedures were employed for the syntheses of [W II Cl 2 (PMePh 2 ) 4 ], 27 [W II Cl 2 (dppe) 2 ] (dppe =1,2-bis(diphenylphosphino)ethane), 28 [W IV Cl 4 (PMePh 2 ) 2 ], 29 [W V (NPh)Cl 3 (PMe 3 ) 2 ], 30 [W VI (xylidene) 3 ], 31 [W 0 (Me 2 pipdt)(CO 4 )] (Me 2 pipdt = 1,4-dimethylpiperazine-2,3-dithione), 21 [W II (mdt)(CO) 4 ], 20 , 21 [W II (mdt)(CO) 2 (PMe 3 ) 2 ], 20 [W IV (mdt) 2 (CO) 2 ], 20 , 32 [W IV (mdt) 2 (CO)(PMe 3 )], 20 [W IV (mdt) 2 (PMe 3 ) 2 ], 20 [W IV (mdt) 2 (CN t Bu) 2 ], 22 [NEt 4 ] 2 [W IV (mdt) 2 (CN) 2 ], 22 [Ph 4 P] 2 [W IV (mnt) 3 ] (mnt 2– = maleonitriledithiolate), 33 [PPh 4 ] 2 [W IV (bdt) 3 ] (bdt 2– = benzene-1,2-dithiolate), 34 [NEt 4 ] 2 [W IV (bdt) 3 ], 34 [Et 4 N] 2 [W IV (mdt) 3 ], 35 [PPh 4 ][W V (bdt) 3 ], 34 [Et 4 N][W V (mdt) 3 ], 35 [W VI (bdt) 3 ], 36 [W VI (mdt) 3 ], 20 [W VI (pdt) 3 ] (pdt 2– = 1,2-diphenylethene-1,2-dithiolate). 36 Commercial sources of [W 0 (CO) 6 ] and [W VI Cl 6 ] were purified by vacuum sublimation before use.…”

trans-Dichlorobis[ethane-1,2-diylbis(diphenylphophine)-κ2P,P′]tungsten(II) pentane hemisolvate

“…A by-product was also formed in this reaction, which by elemental analysis and 1 H NMR spectroscopy was identi®ed as trans-[WCl 2 (dppe) 2 ], (4). Complex (4) was previously prepared by ligand exchange of trans-[WCl 2 (PMePh 2 ) 4 ] with dppe; however, its molecular structure was not reported (Over et al, 1992). The title compound, (4), crystallizes in the same space group (C2/c) as the isostructural molybdenum complex trans-[MoCl 2 (dppe) 2 ]Á0.5C 5 H 12 .…”

Selective deoxygenation of nitrate to nitrosyl using trivalent chromium and the Mashima reagent: reductive silylation

“…This problem demands new approaches to deoxygenation of nitrate. In contrast to deoxygenation of N V , abstraction of O atoms from a metal oxo complex can be accomplished by a low valent metal M′ (Scheme 1) via “oxygen atom transfer”, but this reaction can often merely form a bridging MOM′ complex 3–6. O atom abstraction can sometimes occur by two electron reduction by PR 3 , by CO, rarely and under forcing conditions with H 2 , or in more complicated transformations with boron hydrides 7…”