Glòria Segalés

Carbosilane dendrimers functionalized with AuFe3 clusters

Abstract The reaction of the carbosilane dendrimers Si(CH 2 CH 2 SiMe 3− n Cl n ) 4 ( n =1,2) with LiCH 2 PPh 2 afforded the new phosphino-terminated dendrimers Si(CH 2 CH 2 SiMe 2 CH 2 PPh 2 ) 4 ( 1 ) and Si(CH 2 CH 2 SiMe(CH 2 PPh 2 ) 2 ) 4 ( 2 ). By treatment of 1 and 2 with ClAu(tht), the gold-containing dendrimers Si(CH 2 CH 2 SiMe 2 CH 2 PPh 2 AuCl) 4 ( 3 ) and Si(CH 2 CH 2 SiMe(CH 2 PPh 2 AuCl) 2 ) 4 ( 4 ) were obtained, which in turn, reacted with (PPh 4 ) 2 [Fe 3 (CO) 11 ] to give the first metal-cluster-containing dendrimers reported so far: (PPh 4 ) 4 [Si(CH 2 CH 2 SiMe 2 CH 2 PPh 2 {AuFe 3 (CO) 11 }) 4 ] ( 5 ) and (PPh 4 ) 8 [Si(CH 2 CH 2 SiMe(CH 2 PPh 2 {AuFe 3 (CO) 11 }) 2 ) 4 ] ( 6 ).

Electrospray mass spectrometric studies of some heterometal anionic carbonyl clusters

Electrospray mass spectra (ESMS) are reported for a series of anionic transition-metal clusters of the type (PPh4)[Fe3(CO)10(μ-CO){μ-Hg(m)}] (m = Mo(CO)3Cp; Co(CO)4; Fe(CO)2Cp; W(CO)3Cp; Mn(CO)5) and also for the species of higher nuclearity (NEt4)[Fe6C(CO)16AuPPh3] in methanol solution. The results were compared with those obtained by FAB-MS, and they indicate that ESMS is the most appropriate technique by which to obtain control fragmentation. Information about the strength of the different metal-metal bonds present in the cluster can be deduced from the species generated.

Very large neutral and polyanionic Fe/Au cluster-containing dendrimers

Abstract Treatment of tetrahydrofuran solutions of a series of ClAu-terminated dendrimers with the iron anions [Fe2(CO)7(PPh2)]− and [Fe3(CO)11]2− has allowed the new dendrimer species decorated on the surface by Fe2Au or Fe3Au units to be isolated, including one having up to 192 Fe2Au clusters.

Transition metal clusters containing carbosilane dendrimers

Abstract The reaction of a series of AuCl-terminated carbosilane dendrimers with THF solutions of the anions [Mo(CO) 3 Cp] − , [Mo 2 (μ-H)(μ-dppm)(CO) 8 ] − and [Mn 3 (μ-H)(CO) 12 )] 2− enabled new mixed gold/transition metal clusters containing carbosilane dendrimers to be isolated.

Iron/gold carbide clusters containing Fe5Au or Fe5Au2 skeletons: X-ray crystal structure of [Fe5CAu2(CO)14(dppm)]

Abstract The reaction of (NEt4)2[Fe5C(CO)14] with (AuCl)2(diphos) depends on the stoichiometry of the process. Thus, with a 1:1 molar ratio, the cluster [Fe5CAu2(CO)14(diphos)] (diphos=dppm, 1; dppe, 2; dppp, 3) was obtained. The X-ray crystal structure of 1 revealed that the metal core can be described as a square-based pyramid of Fe atoms and a trigonal bipyramid, with two Fe and one Au atoms at the vertices of the base and one Au and one Fe atoms at the apices, sharing a triangular face of Fe atoms. However, the use of a 2 (iron anion):1 (gold derivative) molar ratio yielded the cluster (NEt4)2[{Fe5CAu(CO)14}2(diphos)] (diphos=dppm, 4; dppe, 5; dppp, 6), in which two octahedral Fe5Au metal cores are linked by the diphosphine. On reacting with ClAuPR3, the latter derivative underwent an unusual ligand redistribution process.

Electrophilic additions of mono-, di- and tri-gold units to the isoelectronic [Mn3(CO)12(μ-H)]2− and [Fe3(CO)11]2− anions

The reaction of [PPh4]2[Mn3(CO)12(μ-H)] with [ClAuPR3] or [(AuCl)2(μ-diphos)] in tetrahydrofuran gives the mixed manganesegold clusters [PPh4][Mn3(CO)12(μ3-H)(μ-AuPR3)] (R = Ph (1 or Me (2)) and [PPh4]2[{Mn3(CO)12(μ3-H)Au}2(μ-diphos)] (diphos = dppe (3)or dppm(4)) The reaction between the same manganese anion and [(AuCl)3(triphos)] produces [{Mn3(CO)12(μ3-H)Au}3(triphos)]3− (5), [{Mn3(CO)12(μ3-H)Au}2(triphos)(AuCl)]2−] (6) or [{Mn3(CO)12(μ3-H)Au}(triphos)(AuCl)2]− (7), depending on the molar ratio of the reagents. Isoelectronic irongold complexes [{Fe3(CO)11Au}3−x(triphos)(AuCl)x](3−x)− (x = 0 (8), 1 (9) or 2 (10)) were obtained by the reaction of the trinuclear [Fe3(CO)11]2− anion with [(AuCl)3(triphos)] in the appropriate molar ratio. Attempts to obtain mixed manganeseirongold clusters resulted in a mixture of compounds, the nature of which has been explained in terms of metal-ligand redistribution processes.

ELECTROCHEMICAL STUDIES OF MN3HGM (M = MO, W, MN, FE OR CO) AND MN3AU CLUSTER ANIONS

Abstract The electrochemical behaviour of compounds of the type (PPh4)[Mn3(CO)12(μ3-H)(μ-Hgm)][m = Mo(CO)3Cp(1), W(CO)3 Cp (2), Mn(CO)5 (3), Fe(CO)2 Cp (4) or Co(CO)4 (5)] and the [PPh4]+ salts of the anions [{Mn3(CO)12(μ3-H}2Hg]2− (6), [{Mn3(CO)12(μ3-H)Au} 2(dppe)]2− (7) and [{Mn3(CO)12( μ 3 - H ) Au } n ( triphos)(AuCl) 3−n ] n− [n = 1 ( 8 ), 2( 9 ), 3( 10 )] has heen investigated at Pt (or Au) electrodes in CH2Cl2 or THF by means of cyclic voltammetry and coulometry. All the compounds undergo a quasi-reversible oxidation and an irreversible reduction. The electrons involved in both oxidation and reduction are delocalized mainly onto the metal fragments, Mn3Hg and Mn3Au, and the slight changes in the redox potential throughout the series of compounds are explained in terms of the nucleophilicity of the metal fragments, m. In the series of gold clusters a weak electronic interaction has been observed between the metal units through the triphosphine.