Oxo-hydrido and imido-hydrido derivatives of permethyltantalocene. Structures of (.eta.5-C5Me5)2Ta(:O)H and (.eta.5-C5Me5)2Ta(:NC6H5)H: doubly or triply bonded tantalum oxo and imido ligands?

Computational Study of Analogues of the Uranyl Ion Containing the −NUN− Unit: Density Functional Theory Calculations on UO22+, UON+, UN2, UO(NPH3)3+, U(NPH3)24+, [UCl4{NPR3}2] (R = H, Me), and [UOCl4{NP(C6H5)3}]-

“…This neatly rationalizes the linearity observed experimentally in [TaH-(C 5 Me 5 ) 2 NPh]. 42 Previous EHMO calculations therefore indicate that, provided the group attached to nitrogen is bound in a σ-only manner, bending at the imido nitrogen is a facile process, and NMR [44][45][46] One of the key issues in d block imido chemistry that is not a factor in uranium compounds is the 18-electron rule. Thus, the rationalization of the bonding in [TaH(C 5 Me 5 ) 2 NPh] 39,42 involves only a double bond between the metal and the nitrogen in order to avoid the 20-electron count implied by a Ta-N triple bond.…”

“…42 Previous EHMO calculations therefore indicate that, provided the group attached to nitrogen is bound in a σ-only manner, bending at the imido nitrogen is a facile process, and NMR [44][45][46] One of the key issues in d block imido chemistry that is not a factor in uranium compounds is the 18-electron rule. Thus, the rationalization of the bonding in [TaH(C 5 Me 5 ) 2 NPh] 39,42 involves only a double bond between the metal and the nitrogen in order to avoid the 20-electron count implied by a Ta-N triple bond. Perhaps the classic example in this area is the Os(N-2,6-C 6 H 3 -i-Pr 2 ) 3 system of Schrock et al 47 Linearity at the nitrogen atoms implies formal triple bonds and a 20-electron count at the metal center.…”

Bis(η-cyclopentadienyl)-molybdenum and -tungsten imido complexes: X-ray structures of [Mo(η-C5H5)2(NBut)] and [Mo(η-C5H4Me)2(NBut)Me]I

“…The X-ray structure of 4-1 has been determined and the cationic part is shown in Fig. 3 13 Interestingly, the X-ray structure of [Ta(qCSMes)2(H)(NPh)] apparently shows no unusual features for the Ta(q-C5MeS), unit and the Ta-N bond is long compared with that expected for a four-electron donor imido ligand.…”

(Alkyl)(monocyclopentadienyl)niobium and ‐tantalum Complexes in Insertion Processes

“…The oxygen ligandϪtantalum atom bond of 1.731 (7) Å is in the range reported for TaϭO double bonds. [32] As well as alkyl (methyl) room temperature in hexane or [D 6 ]benzene (NMR tube scale) to give [33] (Scheme 5), as result of migration of the alkyl group bonded to the metal atom to the electrophilic carbonyl atom of the previously groups with respect to the methyl group, which accords with the sequence established for the isocyanide insertion process. [33] When X ϭ Cl, R ϭ CH 2 CMe 3 (18) and X ϭ Me, R ϭ 2-(CH 2 NMe 2 )C 6 H 4 (49) 6 H 3 ; X ϭ Cl, R ϭ CH 2 CMe 3 , 18; X ϭ R ϭ Ph, 31) as starting materials failed to give the expected (η 2 -acyl)imido derivatives as they were spontaneously converted into the (η 2 -iminoacyl)oxo complexes [TaCp*X(O){η 2 -C(R)‫؍‬NR 1 }] after 35 d (X ϭ Cl, R ϭ CH 2 CMe 3 , 70) and 12 h (X ϭ R ϭ Ph, 71), respectively (Scheme 5); the formation of these products can be explained as with the analogous chloro(methyl)imidotantalum derivatives.…”