Lavender, Mark Harley; (1995) Phosphine stabilized di-iron complexes. Doctoral thesis (Ph.D.), UNSPECIFIED.

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Abstract

This thesis describes the synthesis and reactivity of phosphine stabilised dimetallic complexes containing bridging-hydride ligands. The complex [Fe2(CO)6([mu]-CO)([mu]-dppm)] (dppm = Ph2PCH2PPh2), reacts in the presence of uv irradiation with secondary phosphines to afford the complexes [Fe2(CO)4([mu]-CO)([mu]-H)([mu]-PR2)([mu]-dppm)] (1.Ph, R=Ph; 1.Cy, R=Cy). These have been found to display two general types of reactivity, namely insertion of unsaturated organic molecules into the metal-hydride bond, and elimination of the hydride ligand with replacement by a 3-electron donor. A variety of different organic molecules can be inserted affording a number of different products. Reaction with primary or activated secondary alkynes results in [σ]-[π] vinyl complexes of the general form [Fe2(CO)4([mu]- CRI=CHRII)([mu]-PR2)([mu]-dppm)] (RII = H for 1[degrees] alkynes). Heterocumulenes such as carbon disulphide and isothiocyanates also readily insert into the metal-hydride moiety in 1.Cy, to afford a dithioformato complex [Fe2(CO)4([mu]-S2CH)([mu]-PCy2)([mu]-dppm)] and formimidoyl, [Fe2(CO)4([mu]2-RN=CH)([mu]-PCy2)([mu]-dppm)] and N-thioformamido [Fe2(CO)4([mu]-RINCHS)([mu]-PCy2)([mu]-dppm)] complexes respectively. Elimination of the hydride occurs upon thermal reaction of the hydride complexes with secondary phosphines to afford the bis(phosphido) species [Fe2(CO)4([mu]-PPh2)2([mu]-dppm)] and [Fe2(CO)4([mu]-PPh2)([mu]-PCy2)([mu]-dppm)]. The hydride can also be replaced by protonation with acids containing nucleophilic anions. In this way the halide species [Fe2(CO)4([mu]-X)([mu]-PCy2)([mu]-dppm)] (X = F, Cl, Br, I) have been synthesised. Hydride elimination also occurs in the absence of external reagents, thus thermolysis of a toluene solution of 1.Ph or 1.Cy results in loss of benzene and formation of [Fe2(CO)5([mu]2-[eta]3- Ph2PCH2PPh)([mu]-PR2)]. Column chromatography of either hydride species affords the bridging-hydroxide species [Fe2(CO)4([mu]-OH)([mu]-PR2)([mu]-dppm)].

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