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.
Highlights
The chemical behaviour of transition-metal complexes combining in the same molecule two or more close metal atoms of different elements is a living research area within modern Inorganic Chemistry
Complexes displaying multiple bonds between distinct metal atoms are a class of heterometallic species of particular interest, since they combine the high electronic and Inorganics 2018, 6, 125; doi:10.3390/inorganics6040125
According to density functional functional theory theory (DFT) calculations, the ammonia ligand in the title complex is weakly coordinated to the manganese atom, so it can dissociate at room temperature
Summary
The chemical behaviour of transition-metal complexes combining in the same molecule two or more close metal atoms of different elements (heterometallic complexes) is a living research area within modern Inorganic Chemistry. Inorganics 2018, 6, 125 high electronic and coordinative unsaturation inherent to multiple bonds with the polarity of heterometallic bonds, which should lead to increased reactivity, when compared to homometallic coordinative unsaturation inherent toofmultiple bonds has withbeen the polarity of little heterometallic which analogues [4,5,6,7,8]. The chemistry these species relatively explored bonds, so far, due to should lead to increased reactivity, when compared to homometallic analogues [4,5,6,7,8].
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