Covalent compounds of quadrivalent transition metals. Part II. Chromium(IV) tertiary alkoxides and triethylsilyloxide

Abstract

End Road, London E.l Chromium(1V) tetra-alkoxides Cr(OR), (R = t-alkyl) and Cr(OSiEt,), have been prepared and their reactions studied. Variable-temperature magnetic susceptibilities, electronic and infrared spectra, electron spin resonance, and mass spectra have been measured for Cr(OBut), and the results are discussed in terms of a distorted tetrahedral Cr04 unit.QUADRIVALENT chromium compounds are comparatively rare. Apart from the halides CrX, (X = F, C1, Br),, and M1CrF5 and M1,CrF6 (M = K, Rb, Cs),, and the mixed oxides Mn4Cr06 and MI13Cr0, (M = Sr, Ba) which are complex, the volatile blue solid C ~( O B U ~) , ~ is the best authenticated quadrivalent chromium compound. We now report the preparation of more chromium(1v) alkoxides together with details of their physicochemical properties.Prefiarative Methods. -Chromium t etra-tertiary butoxide has been prepared by the following methods: (i) the action of di-t-butyl peroxide on dibenzenechromium; (ii) alcoholysis of Cr(NEt,),;5 (iii) oxidation of cr(Ol31.1~)~ in the presence of ButOH by various reagents [e.g. But,O,, CrO,(OBut),, Pb(OAc),, Br,, or OJ ; 5 (iv) from the reaction of CrC13,3THF with NaOBut and cuprous chloride; and (v) the addition of cuprous chloride to a suspension of LiCr(OBut), in refluxing tetrahydrofuran.' A number of pure tetra-t-alkoxides were prepared [mainly by method (ii)] and their physical properties are listed in Table 1. They are all blue liquids or low-melting solids which can be distilled i n vacuo. Molecular-weight determinations (cryoscopic in cyclohexane) showed that they were monomeric and 1

Ligand-Sensitive But Not Ligand-Diagnostic: Evaluating Cr Valence-to-Core X-ray Emission Spectroscopy as a Probe of Inner-Sphere Coordination

“…Cp 2 Cr (Cp = cyclopentadienyl) was purchased from Strem and used without further purification. The following model compounds were prepared following literature procedures: Np 4 Cr (Np = neopentyl), 18 Cr(O t Bu) 4 , 19 (tpfc)CrO (tpfc = tris (pentafluorophenyl)corrole), 20 Cr(14-TMC)(O 2 )(Cl) (14-TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), 21 [Cr(bpy 3 )](PF 6 ) 3 (bpy = 2,2′-bipyridine), 22 [Cr(NH 3 ) 6 ](NO 3 ) 3 , 23 and (NH 4 ) 2 [CrNCl 4 ]. 24 …”

Chromous siloxides of variable nuclearity and magnetism

“…2 Initial reports on discrete chromosiloxanes featuring monoanionic siloxy ligands include silyl chromates CrO 2 (OSiR 3 ) 2 (R = Me, Ph) 3,4 and tetravalent Cr(OSiEt 3 ) 4 . 5 Sterically demanding siloxy ligands like [OSi(OtBu) 3 ] and [OSitBu 3 ] were shown to afford discrete, lowvalent chromo(II)siloxanes, obtained as homoleptic [LCr(μ-L) CrL] dimers and [CrL 2 (Do) n ] monomers in the presence of donor molecules Do. [6][7][8][9][10][11] Structurally authenticated homoleptic Cr II siloxides comprise [Cr(OSitBu 3 )(μ-OSitBu 3 )] 2 (ref.…”

“…12 These features, as well as their stabilizing properties, make siloxy ligands an interesting target for the synthesis of otherwise elusive compounds. 5,10,14 Since the aggregation of the complexes is also known to bear on their magnetic properties we aimed at increasing the scope of readily available Cr II siloxides by introducing the ligands [OSiEt 3 ] and [OSiiPr 3 ].…”

Preparation and properties of 1-adamantoxides, 2-adamantoxides, and 1-adamantylmethoxides of Ti IV , V IV , Nb IV , Nb V , Cr III , Cr IV , Mo IV , Mn II , Fe III , and Co II . The crystal and molecular structure of tetrakis(1-adamantoxo)dimethylaminemolybdenum(IV)

“…The increased number of bands might well be due to interaction between v(M-0) and either 6(M-0-C) or vibrations of the alkyl substituents. The complexes (18) Mo(1-ado),(PMe,) (20) [Mn(l-admeo),], (21) [Fe(l-ado),], (22) [Fe( l-admeo),], (23) [Co(l-ado),], (24) [Co( l-admeo),], Ti(1-ado), and Ti(Z-ado), too show more than one band in the region in question at somewhat higher wavenumbers than found for Ti(OPri),. Assignments for Ti(1-admeo), are not possible due to the presence of CH, deformation modes.…”