Complexes of the Early Transition Metals with o-Mercaptophenol and 1,2-Dihydroxybenzene

Abstract

TAKATS. Can. J. Chem. 53,572 (1975). A novel synthetic approach, based on the reactivity of amido derivatives of the transition metals, M(NR,),,, towards protic reagents, for the synthesis of complexes of Ti, Zr, Hf, N b , and Ta with o-mercaptophenol and 1,2dihydroxybenzene is reported. The complexes, isolated as their tetraalkylammonium and tetraphenylarsonium salts, are moderately air stable, well behaved 2:l (Ti, Zr, HQ and 1:l (Nb, Ta) electrolytes. The u.v.-visible spectraof the complexes, which are somewhat reminiscent of the corresponding benzene-1,2dithiolates, are dominated by ligand-to-metal charge transfer bands. The band positions change in the expected manner, hypsochromic shifts in the order C,H4S2z-<C6H,S02-<C6H,022-for agiven metaland Ti <Zr -Hf, Nb < Ta, Nb < Zr for agiven ligand. It is argued that these spectral resemblances could be a possible indication of variations in coordination geometry of the reported complexes similar to the ones found in compounds of benzene-1,2-dithiol. Chem. 53,572(1975). On dkcrit une nouvelle synthkse pour lapreparation des composds du Ti, Zr, Hf, Nbet T a avec 1'0-mercaptoph6nolet le benzkne dihydroxy-1,2. Lasynthbseutilize la rkactivit6desamiduresdes mCtaux de transition, M(NR2),, vis vis les ligands contenant des protons acidiques. Les composes, obtenus sous forme de sels d'ammonium et d'arsonium quarternaires, sont modCrement stable B I'airet se comportent en solution commes desdlectrolytes 2: 1 (Ti, Zr, HQ et 1:l (Nb, Ta). Les spectres u.v.-visibles, qui sont dominks par des bandes de transfert de charge, ressemblent aceux des composes correspondants avec le benzkne-1,2dithiolene. La position des bandes change d'une manikre prkvisible; les dkplacements hyposochromes sont dans I'ordre C6H4S2Z-< C6H,0S2-<C6H,022-pour un metaldonnk et dans I'ordre Ti < Zr -Hf, Nb c Taet Nb < Zr pour un ligand donnk. On discute la possibilite que les ressemblances spectrales indiquent une variation dans la gkometrie de coordination similaire a celle trouvte dans le cas des composes avec le benzkne dithiol-1,2. IntroductionTi, Zr, and Hf, x = 4, R4E = (C2H5),N, X = In the course of our investigation on the 0 , and Y = S (also for% and Hf X = Y = 0 ) ; chemistry of benzene-I,2-and toIuene-3,4-dithiol whereM = Nb and Ta, x = 5, R4E = (C,H5)4-complexes of the early transition metals we have = 0~ and = S. devised a convenient new synthetic procedure The impetus to extend our studies to these for the preparation of such complexes (ref. 1 complexes was twofold. First, the complexes are and refs. therein). ~h~ method involved the related to the corresponding transition metal reaction of a metal amide, M(NR,),, with a benzene-l,2-dithiolates and as such might promixture of the dithiol and its sodium salt in vide additional information to our understanding tetrahydro fur an and subsequent replacement of of the unusual chemical properties (facile onethe sodium ions by a bulky organic cation. ~h~ electron transfer reactions, trigonal prismatic application of our method to the synthesis of ...

A Self‐Assembled Complex with a Titanium(IV) Catecholate Core as a Potential Bimodal Contrast Agent

“…Hence, we can represent the structure of the metallostar compound as Photophysical properties: The absorption spectrum of ligand H 6 4 is similar to that of the nonderivatized catechol [39] and displays a band at 281 nm (e = 7185 m À1 cm À1 ; Figure 2). This band slightly shifts to the blue region and a tail that extends to the red region appears upon complexation with…”

“…The position of the LMCT band is typical for Ti IV complexes of catechol. [23,39] Due to the high affinity of Ti IV ions to catechol ligands, [19,21,40] the formation of [(Gd4) 3 TiA…”

Visible absorption spectra of metal–catecholate and metal–tironate complexes

“…62 Consequently, previous studies with Ti 4ϩ and catechol discussed formation of only the tris-catecholate, [Ti(cat) 3 ] 2Ϫ , and at high concentrations of base (pH > 12) the bis µ-oxo dimer, [TiO(cat) 2 ] 2 . 24,62, 63 In an effort to examine the ability of titanium to form bis-or mono-catecholate complexes, titrations were performed using titanium in different oxidation states (i.e., Ti 3ϩ and Ti 4ϩ ), starting complexes (i.e., TiCl 4 , TiO(acac) 2 and TiBr 4 ), various conditions of pH (slightly acidic water to 1 M HCl), and concentrations (catechol : Ti 4ϩ of 3 : 1, 2 : 1, 1 : 1 and 0.3 : 0.1 mM). Although none of the conditions examined were able to bring about a clean conversion between species, all conditions produced a new titanium-catecholate complex in addition to [Ti(cat) 3 ] 2Ϫ .…”

A Tetranuclear Planar Hafnium Complex Containing O–Hf–S Moieties

“…Moreover, of particular interest is the formation of heteroleptic complexes with S and O atoms chelating the same metal ion, since the S-M-O fragment is expected to be characterized by electronic properties signifi- [14] and complexes of Hf with o-mercaptophenol and 1,2-dihydroxybenzene. [15] Other studies instead focus on S,S ligands used for Hf coordination, such as in bis(pentamethyl)hafnocene 1,8-dithiolatonaphthalene [16] or in the Hf complex with [NEt] 4 -[M(edt)] 3 (edt = ethane-1,2-dithiolate) [17] with secondary phosphane sulfide [Cp 2 Hf(SPPh)]. [18] Further examples of Hf-S complexes are reported in the literature.…”