Tom Nijbacker

Synthesis and X-ray crystal structure of 2-(methoxymethyl) phenyldicyclopentadienyltitanium(III)

Abstract Reaction of bis(2-methoxymethylphenyl)magnesium (1a) with Cp2TiCl2 in THF affords Cp2Ti[2-CH3OCH2C6H4] (3 and 2,2′-bis(methoxymethyl)biphenyl in high yield. The crystal structure of 3 has been determined and is the first structure of a Ti(III) compound in which the Ti atom is intramolecularly coordinated by oxygen. Two chemically identical and conformationally only slightly different residues were found to be present in the unit cell of 3. Compoun C18H19OTi (3) crystallizes in the monoclinic space group Pc (no. 7) with a a = 13.0248(8), b = 7.7769(5), c = 14.849(7) A , β = 106.448(4) 6 , V = 1442.55(15) A 3 , Z = 4 . The structure refinement converged to R1 = 0.0478 for 4891 F0 > 4σ(F0) and wR2 = 0.0968 for all 6600 unique data, S = 1.010. The structure shows a pseudotetrahedral coordination around the Ti atom by two ν5-cyclopentadienyl one carbon of the aryl ligand (TiC 2.19A) and an oxygen atom of the methoxymethyl group. The TiO distance of 2.20A is 1.48 A shorter than the expected van der Waals distance, which indicates a strong interaction between Ti and O. Reaction of bis(2-N,N-dimethylaminomethylphenyl)magnesium (1b) and Cp2TiCl2 affords in a similar fashion Cp2Ti[2-(CH3)2NCH2H4] (4) and 2,2′bis)N,N-dimethylaminomethyl)biphenyl.

Oligomeric 1,2-dihydro-1-magnesacyclobuta[a]naphthalene

l,2-Dihydro-l-magnesacyclobuta[a]naphthalene (4), a mixed benzylic/aromatic diorganylmagnesium reagent, was prepared from the corresponding dihalide and magnesium in THF, followed by removal of MgBrCl with 1,4-dioxane. It is the first example of its kind which is soluble in THF and was shown (UV, NMR, degree of association) to establish an equilibrium between a highly polar oligomer 4a and a less highly associated and more conventional diorganylmagnesium 4b. INTRODUCTION 1,2-Dihydro-l-magnesacyclobutabenzene (la) is a mixed benzylic/aromatic diorganylmagnesium reagent (Scheme 1) which has proven to be of value as a synthon for the preparation of organometallic heterocyclic derivatives [1-9]. Presumably, it has an oligomeric or polymeric structure, as it is rather poorly soluble; even in THF, which normally is a powerful solvent for organomagnesium compounds, the solubility is only about 0.0016 M. On one hand, this property is convenient if one wishes to obtain pure la, because on preparation from the corresponding dihalide 2a and magnesium, the primarily formed di-Grignard reagent 3a undergoes the Schlenck equilibrium with la from which the latter precipitates in pure form. On the other hand, the lack of solubility of la has so far mitigated attempts to obtain information about its structure.

1,8-Naphthalenediylzinc

1,8-Naphthalenediylzinc ( lb) was prepared from the corresponding mercury derivative lc by stirring with metallic zinc for 3 weeks at 50 °C in THF; an intermediate l g has been tentatively identified. Association measurements showed that lb is a dimer like lc and the group 14 analogues. INTRODUCTION In view of the successful application of 1,8-naphthalenediylmagnesium ( la) [1] for the preparation of fourmembered metallacycles [2] and of 1,8-dilithionaphthalene [3] for the preparation of several organic [4] and organometallic [5] 1,8-substituted derivatives of naphthalene, 1,8-naphthalenediylzinc ( l b ) appeared to be an attractive reagent for similar synthetic applications.