Reactions of [W₂(η-C₅H₄R)₂X₄](R = Me or Prⁱ, X = Cl or Br) with Lewis bases and synthesis of a complex containing a perpendicular bridging iminoacyl ligand

Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)

“…The same stereochemistry was also established for compound CpMoCl 3 (dmpe) [22]. The NMR properties of the W derivatives, however, indicate equivalence for the two P nuclei (singlet resonance in the 31 P-NMR spectrum and triplet resonance for the Cp protons in the 1 H-NMR spectrum of 4) and are therefore more consistent with the alternative fac stereochemistry illustrated in VI, which is common, on the other hand, to the previously reported Mo(IV) bis-phosphite derivative CpMoCl 3 [P(OCH 2 ) 3 CEt] 2 [9], and to the W(IV) carbonyl derivatives (C 5 H 4 i Pr)WBr 3 (CO) 2 [23] and Cp*WBr 3 (CO) 2 [15]. The fac geometry of compound 5 has been unambiguously confirmed by an X-ray structural determination (see Fig.…”

“…This distortion could be induced sterically by the proximity of the ring Me substituent and the Cl(1) atom and/or electronically by the back-donation from the metal d xy orbital to one of the ring d acceptor orbitals, as previously described [24]. A similar distortion has been noted for (h 5 -C 5 H 4 i Pr)WBr 3 (CO) 2 , whose stereochemistry is identical to that of compound 6 [23]. We are not aware of other crystal structures of monocyclopentadienyltungsten(IV) chloride or phosphine derivatives.…”

Electrophilic Addition vs Electron Transfer for the Interaction of Ag+ with Molybdenum(II) Hydrides. 1. Reaction with CpMoH(PMe3)3 and the Mechanism of Decomposition of [CpMoH(PMe3)3]+

“…This geometry is analogous to that established for a number of other Cp-containing 18-electron complexes of Mo(IV) and W(IV). [54][55][56][57][58][59][60][61] As may be expected from trans-influence arguments, the Mo-P(2) bond is significantly longer than the Mo-P(1) bond. No noticeable trans-effect, on the other hand, is exerted by the hydride ligand on the Cp ring, since the Mo-CNT distance of 1.97(1) or 1.98(1) Å for the two orientation of the ring in 3 are essentially indentical to the distance of 1.99(1) Å reported for complex [CpMoFCl(dppe)(MeCN)] + , where the ring is located trans relative to the weakly transdirecting fluoride ligand.…”

Monocyclopentadienylmolybdenum(iii) Chemistry

“…A similar tungsten compound, [Cp'WCl(CO)(p-Cl)] 2, has also been reported to have a structure of type X. 41 Other structures based on the four-legged piano stool geometry may be conceived, for instance one having a single bridge between two Mo(II1) centers, but no compounds appear to be known that would require an assebly different than those illustrated in VI-XII. The geometry observed for the tungsten compound [(C,H,-i-Pr)WCl,],, i.e., with an unbridged matel-metal triple bond,23 has never been observed for similar compounds of molybdenum.…”