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An investigation of metal carbonyl complexes including 59Co and 35Cl nuclear Quadrupole resonance studies Chia, Lian Sai

Abstract

An improved method for preparing (L-L)Fe2(CO)6 complexes (L-L is a fluorocarbon-bridged ditertiary arsine or phosphine) has been developed. The reactions of these complexes with monodentate L and bidentate L-L ligands give rise to eight types of products. These include L[sup m](L-L)Fe2(CO)5 and (L-L) [sup m] (L-L)Fe2(CO)5 in which the mono-dentate ligand replaces one carbonyl group from Fe[sup A]; (L[sup m])2[sup s] (L-L)Fe2(CO)4 c A and (L-L) (L-L)Fe2(CO)4 in which two carbonyl groups on Fe have been replaced; (Lm)2(L-L)Fe2(CO)^, (L-L)b(L-L)Fe2(CO) and (dppp) [sup B] (L-L)Fe2(CO)4 in which one carbonyl group on each iron has been replaced; and (Lm)3(L-L)Fe2(CO) in which the ligands replace two carbonyl groups from Fe[sup A] and one from Fe[sup B] . The spectroscopic properties and some reactions of these derivatives are described. The reactions of Co2(CO)8 and (ir-alkyne)Co2(CO)6 with some monodentate and bidentate ligands and that of [LCo(CO)3]2 with bidentate ligands have been investigated. Several new compounds have been isolated; these include bridged derivatives (L-L) [sup b]2Co2(CO) [sup t]2(C0) [sup b]2 and L(L-L) [sup c]Co2(CO)3[sup t] (CO) [sup b]2, non-bridged derivatives (L-L)Co2(CO)^[sup t]7and [(L-L)Co(CO)3]2, ionic products [L2(L-L)Co(CO)]2+[sub 2](X⁻)2 and L4(L-L)Co2(CO)4[sup 2+](X⁻ )2, and substitution products L[sub n](RC = CR)Co2(CO)[sub 6-n](n = 1-4), (L-L)[sup c][sub 2](RC = CR)Co2(CO)4> (dppp)°(RC = CR)Co2(CO)2 (L-L)b2(RC = CR)Co2(CO)2 and (L-L)2(RC = CR)Co2(CO)2. The proposed molecular structures are based on chemical and spectroscopic information. In parallel with the preparative work, 59Co nqr studies on cobalt carbonyl complexes have been carried out. The effects of Y on the nqr spectra of the [Y3PCo(CO3)2 (Y = oph, 0Me, 0Et> Bu[sup n]) compounds are found to be both inductive and conjugative. The coupling constants of the L2Co(CO)+3X (L = Ph3P; X = Co(CO)4, BPh4) compounds appear to be insensitive to the formal oxidation state of the Co atom. The spectra of some substituted derivatives of Co2(C0)8 have been interpreted z o in the light of their structures. The nqr data of (RC = CR')Co2(CO)6 (R = R' = H, CH2OH, Ph, CF3; and R = Bu[sup t], R' = H) are found to be sensitive to the inductive and conjugative effects of the R and R' groups. Some 35Cl nqr studies on fluoroalicyclic YC = CC1(CF2)n (Y = substituent, n= 2 to 4) compounds were also undertaken. The 35 Cl nqr frequencies of these compounds are roughly related to the electronegativity of the substituents Y and to the ring size, suggesting that the inductive effect is the main factor responsible for the change. It also seems that the substituents F, OMe, N3, Me2 show both inductive and conjugative effects.

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