Trapping of an Heterometallic Unsaturated Hydride: Structure and Properties of the Ammonia Complex [MoMnCp(μ-H)(μ-PPh2)(CO)5(NH3)]

Abstract

Complexes displaying multiple bonds between different metal atoms have considerable synthetic potential because of the combination of the high electronic and coordinative unsaturation associated to multiple bonds with the intrinsic polarity of heterometallic bonds but their number is scarce and its chemistry has been relatively little explored. In a preliminary study, our attempted synthesis of the unsaturated hydrides [MoMCp(μ-H)(μ-PR2)(CO)5] from anions [MoMCp(μ-PR2)(CO)5]− and (NH4)PF6 yielded instead the ammonia complexes [MoMCp(μ-H)(μ-PR2)(CO)5(NH3)] (M = Mn, R = Ph; M = Re, R = Cy). We have now examined the structure and behaviour of the MoMn complex (Mo–Mn = 3.087(3) Å) and found that it easily dissociates NH3 (this requiring some 40 kJ/mol, according to DFT calculations), to yield the undetectable unsaturated hydride [MoMnCp(μ-H)(μ-PPh2)(CO)5] (computed Mo–Mn = 2.796 Å), the latter readily adding simple donors L such as CNR (R = Xyl, p-C6H4OMe) and P(OMe)3, to give the corresponding electron-precise derivatives [MoMnCp(μ-H)(μ-PPh2)(CO)5(L)]. Thus the ammonia complex eventually behaves as a synthetic equivalent of the unsaturated hydride [MoMnCp(μ-H)(μ-PPh2)(CO)5]. The isocyanide derivatives retained the stereochemistry of the parent complex (Mo–Mn = 3.0770(4) Å when R = Xyl) but a carbonyl rearrangement takes place in the reaction with phosphite to leave the entering ligand trans to the PPh2 group, a position more favoured on steric grounds.

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

“…+ afforded the hydride complex [MoMnCp(μ-H)(μ-PPh 2 )(CO) 5 (NH 3 )] (369). 309 Shortly after, the reactivity of the heavier congener [MoReCp(μ-PCy 2 )(CO) 5 ] − (368) toward simple donor ligands and p-block E−H reagents was reported. 310…”

“…Ruiz and co-workers have extensively investigated the chemistry of the anionic phosphinidene and phosphinidene oxide complexes illustrated in Figure . − A more extensive review of the chemistry of compounds 349 and 350 (and related compounds) was published by Ruiz in 2013, while the rich chemistry of the P 4 activation products [M 2 Cp 2 (μ-PCy 2 )­(CO) 2 (μ–κ 2 :κ 2 -P 2 )] − [M = Mo ( 351 ), W ( 352 )] and their corresponding methylation products [M 2 Cp 2 (μ-PCy 2 )­(CO) 2 (μ–κ 2 :κ 2 -P 2 Me)] [M = Mo ( 353 ), W ( 354 )] was reviewed by Caporali, Wolf and co-workers in 2021. , …”

“…Mononuclear (top), homodinuclear, and heterodinuclear (bottom) anionic complexes featuring phosphinidene and phosphinidene oxide ligands. − …”

Coordination and Dehydrogenation of Diphosphine–Borane Ph2PCH2PPh2·BH3 at a Heterometallic MoRe Center to Give an Agostic Boryl-Bridged Derivative

“…Recently, we implemented an efficient synthetic procedure for the hydride complex [MoReCp­(μ-H)­(μ-PCy 2 )­(CO) 5 (NCMe)] ( 1 ) which, while being itself an electron-precise species, undergoes displacement of the nitrile ligand by different molecules under mild conditions, whereby it effectively acts as a surrogate of the unsaturated hydride [MoReCp­(μ-H)­(μ-PCy 2 )­(CO) 5 ] (Cp = η 5 -C 5 H 5 ) . The latter is a very unstable molecule which cannot be even detected during protonation of the unsaturated anion [MoReCp­(μ-PCy 2 )­(CO) 5 ] – (Mo=Re)], and the same applies to the analogous MoMn hydride complex …”

“…4 The latter is a very unstable molecule which cannot be even detected during protonation of the unsaturated anion [MoReCp(-PCy2)(CO)5]  (Mo=Re)], 5 and the same applies to the analogous MoMn hydride complex. 6…”