The coordination of small molecules by manganese(II) phosphine complexes. Part 12. The synthesis of some tetrahydrofuran/long chain tertiary phosphine complexes of manganese(II) halides, MnX2(phosphine)(THF), and their reaction with molecular oxygen

Manganese(II) complexes of long chain phosphines, MnX 2 (phosphine)(THF) XCl, Br, I; phosphine=P(C 12 H 25 ) 3 , P(C 14 H 29 ) 3 , P(C 16 H 33 ) 3 , PPh(C 12 H 25 ) 2 , PPh(C 14 H 29 ) 2 , PPh(C 16 H 33 ) 2 ; THF=tetrahydrofuran have been prepared and characterised. These complexes react reversibly with molecular oxygen both in the solid state and in THF and toluene solution forming 1:1 Mn:O 2 adducts. These adducts are monomeric in toluene and THF and molecular weight measurements confirm that the THF ligand remains coordinated in toluene solution leading to the formation of MnX 2 (phosphine)(THF)(O 2 ) species. All the O 2 -adducts are highly coloured and binding curves have been constructed and K o 2 values calculated. Based on these K o 2 values the affinity for dioxygen is in the order XCl>Br>I in toluene solution, with Hill coefficient, n , indicating cooperativity (1-1.5). In THF dioxygen binding does not appear to be cooperative.