Efficient Concatenation of CC Reduction, C−H Bond Activation, and C−C and C−N Coupling Reactions on Osmium: Assembly of Two Allylamines and an Allene

An osmium-promoted assembly of two allylamine molecules and gem-disubstituted allenes to afford π-allyl ligands with a diamine pendant substituent is reported. Complex OsH2Cl2(PiPr3)2 (1) reacts with 2 equiv of allylamine to give Os(CH2CH2CH2NH2)Cl(η2-CH2CHCH2NH2)(PiPr3) (2). At 0 °C carbon monoxide displaces the chloride ligand of 2. At 50 °C, the resulting salt [Os(CH2CH2CH2NH2)(CO)(η2-CH2CHCH2NH2)(PiPr3)]Cl (3) is transformed into Os(CHCHCH2NH2)Cl(CO)(nPrNH2)(PiPr3) (4) by an intramolecular σ-bond metathesis between the alkyl and olefin donor units of 3. The addition of HBF4 to the diethyl ether solutions of 4 affords the alkylidene [OsCl(CHCH2CH2NH2)(CO)(nPrNH2)(PiPr3)]BF4 (5). The reaction of 4 with TlPF6 under CO atmosphere leads to the cis-dicarbonyl derivative [Os(CHCHCH2NH2)(CO)2(nPrNH2)(PiPr3)]PF6 (6), which by treatment with 1-methyl-1-(trimethylsilyl)allene and 1,1-dimethylallene affords [Os{η3-CH2C(CHMeR)CHCH(NHnPr)CH2NH2}(CO)2(PiPr3)]PF6 (R = SiMe3 (7) Me (8)), as a result of the insertion of the allene into the Os−C(sp2) bond of 6 and the subsequent regio- and stereoselective 1,4-addition of a N−H bond of nPrNH2 to the resulting olefin-allyl organic fragment. In agreement with this, under CO atmosphere, complex 4 affords Os(CHCHCH2NH2)Cl(CO)2(PiPr3) (9), which reacts with 1-methyl-1-(trimethylsilyl)allene in the presence of TlPF6 to give [Os{η3-CH2C(CHCHCH2NH2)C(SiMe3)CH3}(CO)2(PiPr3)]PF6 (10). The addition of nPrNH2 and PhNH2 to 10 leads to 7 and [Os{η3-CH2C[CHMe(SiMe3)]CHCH(NHPh)CH2NH2}(CO)2(PiPr3)]PF6 (11), respectively. The X-ray structures of 2, 4, 7, and 10 are also reported.