Nitrosyl derivatives of the unsaturated dihydrides [Mn2(μ-H)2(CO)6(μ-L2)] (L2 = Ph2PCH2PPh2, (EtO)2POP(OEt)2)

The title dimanganese complexes react with NO (5% in N2) at room temperature to give as major products the corresponding hexanitrosyl derivatives [Mn2(NO)6(μ-L2)] in moderate yields, and they react rapidly with NO2 to give the corresponding hydride derivatives [Mn2(μ-H)(μ-NO2)(CO)6(μ-L2)], these having a nitrite ligand bridging the dimetal centre through the N and O atoms. The dppm-bridged dihydride also reacts selectively at 273 K with (PPN)NO2 to give first the nitro derivative (PPN)[Mn2(μ-H)(H)(NO2)(CO)6(μ-dppm)], which then transforms into the nitrosyl complex (PPN)[Mn2(μ-CO)(CO)5(NO)(μ-dppm)] at room temperature or above (dppm = Ph2PCH2PPh2; PPN+ = [N(PPh3)2]+). The latter anion reacts with (NH4)PF6 to give the hydride-bridged nitrosyl complex [Mn2(μ-H)(μ-NO)(CO)6(μ-dppm)] and with [AuCl(PPh3)] to give the trinuclear cluster [AuMn2(μ-NO)(CO)6(μ-dppm)(PPh3)] (Mn–Au = ca. 2.68 Å; Mn–Mn = 2.879(2) Å). Both products are derived from the addition of the added electrophile at the intermetallic bond and rearrangement of the nitrosyl ligand into a bridging position. In contrast, methylation of the anion with CF3SO3Me takes place at the nitrosyl ligand to yield the unstable methoxylimide derivative [Mn2(μ-NOMe)(CO)6(μ-dppm)]. Analogous reactions at the nitrosyl ligand take place upon the addition of HBF4·OEt2 to the nitrosyl-bridged hydrides [Mn2(μ-H)(μ-NO)(CO)n(μ-dppm)m] (n = 6, m = 1; n = 4, m = 2) to give the corresponding hydroxylimide derivatives [Mn2(μ-H)(μ-NOH)(CO)n(μ-dppm)m]BF4, which were also thermally unstable and could not be isolated nor fully characterized.

The anionic nitrosyl complex [Mn2(μ-CO)(CO)5(NO)(μ-Ph2PCH2PPh2)]−, accessible from the unsaturated hydride [Mn2(μ-H)2(CO)6(μ-Ph2PCH2PPh2)], reacts with different electrophilic reagents through either its dimetal site or the oxygen atom of its nitrosyl ligand, thus allowing the synthesis of new complexes having nitrosyl or nitrosyl-derived bridging ligands, as shown in the Scheme (P–C–P = Ph2PCH2PPh2). Figure optionsDownload as PowerPoint slideResearch highlights
► The title hydrides are reactive towards NO and NO2.
► Anionic nitrosyl complexes can be made from the title hydrides and NO2−.
► Dimanganese nitrosyl complexes display Mn- and O-based reactivity.