Synthesis and characterization of CpMn(dfepe)(L) complexes (dfepe = (C2F5)2PCH2CH2P(C2F5)2; L = CO, H2, N2): an unusual example of a dihydride to dihydrogen photochemical conversion

Abstract The synthesis and properties of perfluoroalkylphosphine manganese complexes CpMn(dfepe)(L) (dfepe = (C 2 F 5 ) 2 PCH 2 CH 2 P(C 2 F 5 ) 2 ; L = CO, H 2 , N 2 ) are reported. CpMn(dfepe)(CO) ( 1 ) was prepared by treatment of CpMn(CO) 2 (thf) with excess dfepe. The observed ν (CO) (1934 cm −1 ) and E 1/2 (ox) (+1.09 V) values confirm the very electron-deficient nature of the CpMn(dfepe) moiety. Photolysis of 1 under a H 2 purge produced a 6:1 equilibrium isomeric mixture of the hydride complexes CpMn(dfepe)(H) 2 ( 2a ) and CpMn(dfepe)(η 2 -H 2 ) ( 2b ). Photolysis of a mixture of 2a and 2b in benzene resulted in complete conversion of 2a to 2b , which slowly thermally reconverted to an equilibrium mixture ( k  ∼ 2.3 × 10 −4 s −1 ). The dihydrogen complex 2b reacts with N 2 gas to produce CpMn(dfepe)(N 2 ) ( 3 ) ( ν (N 2 ) = 2113 cm −1 ). Attempts to isolate 3 resulted in production of the corresponding N 2 -bridged dimer, [CpMn(dfepe)] 2 (μ-N 2 ) ( 4 ) (Raman: ν (N 2 ) = 2015 cm −1 ).