Synthesis, Structure, and Protonation Studies of Cp*MH<sub>3</sub>(dppe) (M = Mo, W). Pseudo-Trigonal-Prismatic vs Pseudo-Octahedral Structures for Half-Sandwich Group 6 M(IV) Derivatives Brett Pleune Rinaldo Poli James C. Fettinger 10.1021/om961002o.s003 https://acs.figshare.com/articles/dataset/Synthesis_Structure_and_Protonation_Studies_of_Cp_MH_sub_3_sub_dppe_M_Mo_W_Pseudo-Trigonal-Prismatic_vs_Pseudo-Octahedral_Structures_for_Half-Sandwich_Group_6_M_IV_Derivatives/3779145 The compounds Cp*MH<sub>3</sub>(dppe) (M = Mo, <b>1</b>; W, <b>2</b>) are accessible in good yields from reacting the corresponding compound Cp*MCl<sub>4</sub> and LiAlH<sub>4</sub> in toluene/Et<sub>2</sub>O followed by methanolysis. The X-ray structure of <b>1</b> shows a pseudo-trigonal-prismatic geometry which is unprecedented for half-sandwich CpML<sub>5</sub>-type compounds. Protonation with HBF<sub>4</sub>·Et<sub>2</sub>O in Et<sub>2</sub>O at low temperature affords [Cp*MH<sub>4</sub>(dppe)]<sup>+</sup>BF<sub>4</sub><sup>-</sup> salts (M = Mo, <b>3</b>; W, <b>4</b>). While <b>3</b> spontaneously decomposes, even at low temperatures, in coordinating solvents and CH<sub>2</sub>Cl<sub>2</sub>, <b>4</b> is stable at room temperature in MeCN. An X-ray structure of <b>4</b> is consistent with a classical tetrahydrido species with a distorted pseudo-pentagonal-bipyramidal structure. The low-temperature NMR properties, <i>J</i><sub>HD</sub> ≤ 1 Hz for <b>4</b>-<i>d</i><sub>3</sub>, and the <i>T</i><sub>1(min)</sub> value for the hydride resonance are also consistent with this structural assignment. Decomposition of <b>3</b> in MeCN at room temperature selectively affords [Cp*MoH<sub>2</sub>(MeCN)(dppe)]<sup>+</sup>BF<sub>4</sub><sup>-</sup>, <b>5</b>. The NMR properties of this complex indicate a fluxional structure with inequivalent H and P nuclei and are consistent with a pseudo-trigonal-prismatic structure analogous to that of the precursor <b>1</b>. Further protonation of <b>5</b> in MeCN or direct protonation of <b>1</b> with excess acid in MeCN affords two isomers of complex [Cp*MoH(MeCN)<sub>2</sub>(dppe)](BF<sub>4</sub>)<sub>2</sub>, <b>6</b> and <b>7</b>. Thermal treatment in MeCN slowly converts <b>7</b> into <b>6</b> initially, but both isomers further transform into a third isomer, <b>8</b>, upon prolonged heating. The structure of <b>6</b> has been elucidated by X-ray crystallography and consists of a highly distorted pseudo-octahedral geometry with relative <i>trans</i> MeCN ligands. The structures of <b>7</b> and <b>8</b> and mechanisms of the interconversions between the various isomeric structures are proposed on the basis of the solution NMR studies. 1997-04-15 00:00:00 HBF dppe BF 4 compound trans MeCN ligands HD solution NMR studies Mo Et 2 O Cp CH 2 Cl 2 NMR properties room temperature