High Structural Control in Metal‐Mediated Synthesis of New Functionalized Diphosphines Using Diphosphinoketenimines as Precursors

The diphosphinoketenimine ligand in the neutral complexes fac ‐[MnI(CO) 3 {(PPh 2 ) 2 CCNR}] ( 1 a : R = Ph; 1 b : R = p ‐tolyl) undergoes nucleophilic attack by MeLi and n BuMgCl yielding, after hydrolysis, the diphosphinoenamine‐containing complexes fac ‐[MnI(CO) 3 {(PPh 2 ) 2 CC(R′)NHR}] ( 3 a , b : R′ = Me; 4 a , b : R′ = n Bu). Complex 1 a reacts under the same conditions with H 2 CCCHMgBr to afford fac ‐[MnI(CO) 3 {(PPh 2 ) 2 CC(CH 2 CCCH)NHR}] ( 5 a ), which contains a terminal alkyne group on the α‐carbon atom of the diphosphinoenamine ligand. The cationic complexes fac ‐[Mn(CO) 4 {(PPh 2 ) 2 CCNR}] + ( 6 ) react with H 2 CCCHMgBr to afford diphosphinomethanide derivatives bearing three different types of functional groups, depending upon the substituent on the nitrogen atom of the ketenimine: cumulene in fac ‐[Mn(CO) 4 {(PPh 2 ) 2 CC(CHCCH 2 )N‐xylyl}] ( 7 d ), internal alkyne in fac ‐[Mn(CO) 4 {(PPh 2 ) 2 CC(CCCH 3 )N t Bu}] ( 8 ), and quinoline in 9 (R = Ph), whose formation implies an unusual cyclization process. Protonation of 7 d , 8 , and 9 with HBF 4 occurs at the nitrogen atom to give the cationic derivatives 10 d , 11 , and 12 , respectively, which contain the corresponding functionalized diphosphine ligands. Irradiation of 3 a , b and 4 a , b with Vis/UV light makes it possible to isolate the free ligands (PPh 2 ) 2 CC(R′)NHR ( 13 a , b and 14 a , b ), completing the metal‐assisted synthesis of these novel functionalized diphosphines. Irradiation of 12 with Vis/UV light generates free phosphinoquinoline ligand 15 , which readily affords a complex 16 containing 15 as a P,N‐chelating ligand when treated with [PdCl 2 (NCMe) 2 ], thus demonstrating its coordination capability.