Synthesis, Structure, and Hydride−Deuteride Exchange Studies of CpMoH₃(PMe₂Ph)₂ and Theoretical Studies of the CpMoH₃(PMe₃)₂ Model System

Abstract

The synthesis and characterization of CpMoH 3 (PMe 2 Ph) 2 , 1, is described. Compound 1 is obtained from the reaction between CpMoCl 3 , PMe 2 Ph, and LiAlH 4 , in 61% yield. Compound 1 has also been obtained from the reaction of CpMo(o-C 6 H 4 PMe 2 )(PMe 2 Ph) 2 with H 2 . Characterization of 1 by 1 H-and 31 P-NMR spectroscopies shows a high degree of fluxionality for the hydride atoms, even at low temperatures. A single-crystal X-ray structure indicates that the geometry is pseudo-octahedral, with a relative mer arrangement of the three H ligands and the two PMe 2 Ph ligands occupying relative trans positions. This is in contrast with the only other previously reported structure of a Mo(IV) trihydride, Cp*MoH 3 (dppe), which adopts a pseudo trigonal prismatic structure. The Mo-P (average 2.41(8) Å) and Mo-H distances (average 1.64(4) Å) are similar to those found in Cp*MoH 3 (dppe). The closest H-H distance is 1.79 Å, consistent with a classical hydride. The results of ab initio calculations for the CpMoH 3 (PMe 3 ) 2 model in different configurations agree with the experimental observations and suggest that a mechanism of hydride exchange consisting of a Bailar twist, which interconverts pseudo-octahedral mer, trans and fac geometries, is possible. The process of hydride-deuteride exchange of 1 in C 6 D 6 is also examined.

Molybdenum Trihydride Complexes: Computational Determinations of Hydrogen Positions and Rearrangement Mechanisms

“…Also the crucial H1−H2 distance is slightly shorter in Cp i Pr 4 molecule than in Cp t Bu 3 (Table 1). Theoretical investigations of similar complexes 26,27 produced distances in agreement with our structures, and a molecular dynamic simulation study confirmed a high probability of trihydride structures for related Mo complexes. 28 Full sets of geometrical data for all compounds in GP, THF, and MeCN as well as superposition of the most stable calculated structures with the experimental ones are given in section S.II of the SI.…”

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]+

“…The proposed arrangement is equivalent to that observed by X-ray crystallography for the isoelectronic complex CpMoH 3 (PMe 2 Ph) 2 . 61 A similar geometry has also been found through heteronuclear double-resonance experiments and X-ray diffraction study for the isoelectronic complex (C 6 H 5 Me)WH 2 (PMe 3 ) 3 2+ . 65 It is rather remarkable that the dihydride cation does not have any tendency to evolve dihydrogen.…”

“…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.…”

Reactions of Dienes with a Mo(0) Complex with Tetraphosphine Coligand [Mo(P4)(Ph2PCH2CH2PPh2)] (P4 = Meso‐o‐C6H4(PPhCH2CH2PPh2)2)

“…22,23 From the 1 H NMR criteria of the hydrido ligands, the coordination geometries of [CpMoH(L) 3 ] are known to be fairly non-rigid: [CpMoH-(CO) 2 (PR 3 )] are interconverting between cis and trans forms and [CpMoH(PMe 2 R) 3 ] shows the hydrido signal as quartets with J H-P of 52.6 (R = Me) and 50.9 (R = Ph) Hz. 7c, 24 In contrast, since the site exchange among the coordinating P atoms in 7 is not observable, doubly chelating P4 leads to the rigid geometry by excluding other possible structures.…”