Four‐Coordinated Manganese(II) Disilyl Complexes for the Hydrosilylation of Aldehydes and Ketones with 1,1,3,3‐Tetramethyldisiloxane

Abstract

The coordinatively unsaturated manganase(II) bis(supersilyl) complex Mn[Si(SiMe3)3]2(THF)2 (2) was synthesized in one step via the reaction of MnBr2 with two equivalents of KSi(SiMe3)3 in THF. Complex 2 acts as an effective precatalyst for the catalytic hydrosilylation of aldehydes and ketones with 1,1,3,3‐tetramethyldisiloxane (TMDS). The catalytic efficiency can be improved by combining 2 and adamantyl isocyanide (CNAd). The stoichiometric reaction of 2 and two equivalents of CNAd led to the isolation of Mn[Si(SiMe3)3]2(CNAd)2 (3) in high yield. Complex 3 shows superior catalytic performance than 2 in the hydrosilylation of relatively unreactive ketones.

Hydrosilylation of Aldehydes and Ketones Catalyzed by a 2-Iminopyrrolyl Alkyl-Manganese(II) Complex

“…The formation of mid- and late-transition metal-silyl complexes from their alkyl congeners by reaction of PhSiH 3 has been observed previously . Furthermore, we have previously reported the disproportionation of putative hydride complexes via liberation of molecular dihydrogen, when dealing with cobalt complexes with the same 2-iminopyrrolyl ligand. , Specifically, silyl-Mn­(II) complexes have been reported and very recently used as catalysts for the hydrosilylation of aldehydes and ketones . Unfortunately, preparative scale reactions to isolate a silyl-Mn­(II) complex were vain, either from the reaction of complex 2 with PhSiH 3 or via a metathetic exchange reaction of the chloride complex 1 with LiSiH 2 Ph.…”

Manganese-catalyzed hydrogenation, dehydrogenation, and hydroelementation reactions

“…484 Sunada demonstrated that Mn(hmds) 2 (THF) 2 complex Mn130 could also catalyze the carbonyl hydrosilylation reaction without an external ligand (Table 37, entry 13). 485 Recently, Kundu showed that Mn(I)-complex Mn131 also worked well towards the hydrosilylation reaction, albeit a slightly higher reaction temperature was required (Table 37, entry 14). 486 7.2.2.…”

The Rise of Manganese-Catalyzed Reduction Reactions

“…Further examples of Mn(II) hydrosilylation of aldehydes and ketones were presented by the groups of Madrahimov [46] and Sunada. [47] The latter managing to utilize TMDS (tetramethyldisiloxane) as the silane source. reduce esters to alcohols as the major product instead of ethers like the Cutler group; however, small amounts of ether (10-20%) could also be detected.…”

“…Further examples of Mn(II) hydrosilylation of aldehydes and ketones were presented by the groups of Madrahimov 46 and Sunada. 47 The latter managed to utilize TMDS (tetramethyldisiloxane) as the silane source.…”