"Homo- And Hetero-dinuclear Complexes Of Cobalt" by David J. Elliot

Date of Award

1991

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Abstract

The work presented in this thesis concerns the synthesis and characterization of a series of novel phosphine-carbonyl complexes of cobalt. Chapters 2 and 3 outline mononuclear and homodinuclear cobalt complexes, chapters 4 and 5 discuss heterobimetallic complexes (CoM(CO){dollar}\sb{lcub}\rm n{rcub}{dollar}({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Rh,n = 3; M = Mn or Re, n = 5), and finally chapters 6 and 7 discuss complexes containing the {dollar}\mu{dollar}-PPh{dollar}\sb2{dollar} group and the complex ((CO){dollar}\sb2{dollar}({dollar}\eta\sp1{dollar}-dppm) Co({dollar}\mu{dollar}-dppm)BH{dollar}\sb2{dollar}), respectively.;Introduction of CO into Co(II)/phosphine/NaBH{dollar}\sb4{dollar} reaction systems, previously shown to produce a number of interesting complexes, has provided a novel approach to the synthesis of phosphine-carbonyl complexes of cobalt. A number of complexes were isolated including the previously known (CoH(CO) (PPh{dollar}\sb3)\sb3{dollar}) and also (Co(CO) (PP){dollar}\sb2{dollar}) {dollar}\sp+{dollar} (PP = dppm or dppe). In addition isomers of {dollar}\{lcub}{dollar}Co(CO){dollar}\sb2{dollar}(dppm){dollar}\{rcub}\sb2{dollar}, were prepared by this method. By introduction of RhCl{dollar}\sb3\cdot{dollar} (H{dollar}\sb2{dollar}O){dollar}\sb{lcub}\rm n{rcub}{dollar} into the reaction system, the heterobimetallic complex (CoRh(CO){dollar}\sb3(\mu{dollar}-dppm){dollar}\sb2{dollar}) was isolated. Complexes (M(CO) (dppm){dollar}\sb2{dollar}) (Co(CO){dollar}\sb4{dollar}), isolated for M = Co, and observed by {dollar}\sp{lcub}31{rcub}{dollar}P and {dollar}\sp{lcub}13{rcub}{dollar}C in the case of M = Rh, were observed to lose CO in the formation of complexes (CoM(CO){dollar}\sb{lcub}\rm n{rcub}(\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Co, n = 4; M = Rh, n = 3). Similarly the (Co(CO)(dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} cation reacted with other metal carbonyl anions (M(CO){dollar}\sb5{dollar}) {dollar}\sp-{dollar} (M = Mn or Re) to give the complexes ((CO){dollar}\sb2{dollar} ({dollar}\eta\sp1{dollar}-dppm) Co({dollar}\mu{dollar}-dppm)M(CO){dollar}\sb4{dollar}) and (CoM(CO){dollar}\sb5(\mu{dollar}-dppm){dollar}\sb2{dollar}).;The fluxionality of (CoM(CO){dollar}\sb{lcub}\rm n{rcub}(\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Co, n = 4; M = Rh, n = 3; M = Mn, n = 5) and protonated derivatives (Co{dollar}\sb2(\mu{dollar}-H) (CO){dollar}\sb4(\mu{dollar}-dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} and (CoRh({dollar}\mu{dollar}-H) (CO){dollar}\sb3(\mu{dollar}-dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} was investigated by variable temperature {dollar}\sp1{dollar}H, {dollar}\sp{lcub}13{rcub}{dollar}C and {dollar}\sp{lcub}31{rcub}{dollar}P NMR and four types of fluxionality were observed.;The reactivity of complexes (CoM(CO){dollar}\sb{lcub}\rm n{rcub}(\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Co, n = 4; M = Rh, n = 3) was investigated with a range of inorganic oxidizing agents and complexes (CoM ({dollar}\mu{dollar}-X) ({dollar}\mu{dollar}-CO)({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}(CO){dollar}\sb2{dollar}) {dollar}\sp{lcub}\rm n+{rcub}{dollar} (M = Co or Rh; X = Cl, n = 1; X = Br, n = 1; X = I, n = 1; X = S, n = 0) and (CoRh({dollar}\mu{dollar}-H) (CO){dollar}\sb{lcub}\rm n{rcub}{dollar}({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} (M = Co, n = 4; M = Rh, n = 3) were characterized. The reactivity of (CoM(CO){dollar}\sb{lcub}\rm n{rcub}{dollar}({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}) towards olefins was demonstrated to be limited.;Surprising results from the Co(II)/dppm/NaBH{dollar}\sb4{dollar}/CO reaction systems were the isolation of complexes (Co{dollar}\sb2{dollar}({dollar}\mu{dollar}-H) ({dollar}\mu{dollar}-PPh{dollar}\sb2{dollar}) ({dollar}\mu{dollar}-dppm){dollar}\sb{lcub}\rm n{rcub}{dollar}(CO){dollar}\sb{lcub}\rm 6-2n{rcub}{dollar}) (n = 1 or 2) and (Ni{dollar}\sb2{dollar}({dollar}\mu{dollar}-PPh{dollar}\sb2{dollar}) ({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}(CO){dollar}\sb2{dollar}) {dollar}\sp+{dollar}, resulting from the cleavage of a P-C bond in dppm under very mild conditions, and the isolation of ((CO){dollar}\sb2{dollar}({dollar}\eta\sp1{dollar}-dppm) Co({dollar}\mu{dollar}-dppm) BH{dollar}\sb2{dollar}) containing the first structurally characterized simple metal-BH{dollar}\sb2{dollar} linkage.

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