Unexpected Synthesis of Ortho-Substituted Diselenophenylenezirconocenes from the Para-Substituted Diphenylzirconocenes. Chemical and Structural Evidence of the Participation of a Cyclometalated Intermediate That Behaves as a Benzyne Zirconocene Equivalent

Abstract

Heating grey selenium with [v5-C5H4(t-Bu)lzZr(CsHq@-OCH3))2 in boiling octane affords the diselenophenylenezirconocene complex containing a methoxy group in the ortho position. A similar reaction, although less selective, occurs when starting from [v5-C5H4(t-Bu)12Zr-(Cd&(p-CH3))2. The structures of the diselenophenylenezirconocenes obtained were confirmed by NMR spectroscopy and definitively proved by comparison with the authentic orthosubstituted derivatives prepared from the corresponding methyl-o-anisyl-and methyl-otolylzirconocene. The mechanism proposed to explain this transformation involves the activation of a tert-butyl C-H bond by a transient benzynezirconocene species. The cyclometalation product, which is obtained by heating the diphenylzirconocene, reacts toward selenium and unsaturated organic compounds like the benzynezirconocene but the reaction takes place at room temperature. The cyclometalation pathway allows a more sterically hindered selenium-containing derivative [q5-C5H4(t-Bu)l2ZrSe2C6H3(o,o'-(CH&) to be prepared. The new diselenophenylenezirconocenes described are good precursors to generate benzodiselenagermoles and related spiro compounds by a zirconium-germanium transmetalation reaction. All the new products synthesized, zirconocene complexes and cyclometalated derivatives, benzodiselenagermoles, and spirobisbenzodiselenagermoles, were identified by the multinuclear NMR methods and mass spectrometry. The structure of the cyclometalated product [q5-C5H4(t-Bu)IZr[(2,5-(CH3)2CgH3)(1;1l: v5-CH2C(CH3)2C5H4)I was determined by X-ray diffraction analysis. This compound crystallizes in the monoclinic space group P21/c with two molecules per asymmetric unit with cell dimensions a = 8.278(3) .$, b = 20.113(9) A, c = 27.661(9) .$, and / 3 = 93.13(2)' at 295 K. Least-squares refinement led to a value for the final R index of 0.0642 for 2701 reflections with I =-2 4 1 ) .

Tetraselena crown ethers: synthesis and complexation with mercury salts. Crystal structure of a macrocycle and a mercury(II) complex

“…This distribution is in accordance with the methoxy group being at the 3 position on the benzene ring. 14 The 13 C NMR spectra of macrocycles 6-8 are also consistent with the proposed structures: three signals appear in the aromatic region between δ 127 and 135 and two in the aliphatic region between δ 27 and 71.…”

“…12, 13 The (3-methoxybenzene-1,2-diselenolato)zirconocene 12 was prepared by literature methods. 14 The chloroethers used in the synthesis were commercial products, distilled before use. Since the preparations of compounds 1-4 are essentially identical only the experimental details for 1 are presented.…”

Macrocycles containing 1,1′-ferrocenyldiselenolato ligands on group 4 metallocenes

“…Chemical shifts were in good agreement with those reported for structurally similar complexes. 17,34,36,37 Selenium resonances are largely sensitive to a change in the transition metal. Changing the transition metal from Ti to Zr has a shielding effect of −400 ppm (δ = 963.0 ppm (1), 558.0 ppm (2)), which is substantially larger than that recorded previously using a phenyl substituent (Δδ = −170 ppm).…”

“…13,15 Special interest was focussed on zirconocene dichalcogenides although high temperatures were required for the complex formation. 3,[15][16][17] Access to titanium and hafnium analogues through transmetallation decreased their overall yields dramatically to 40%, 18 and therefore the use of dilithium salts of diselenolate ligands with metallocene dichlorides was a good compromise for simple synthetic design and achieving high yields. 19 Few examples are found in the literature involving sulfur and tellurium analogue species.…”

Short‐Lived Orthobenzyne Complexes with Early Transition Metals of Group IV. First Direct Characterization and Electronic Cartography by Coupling FVT/UV‐PES with Calculations

“…With the methoxy substituent on the aryl group, the bis(trimethylphosphine) adduct of the benzydiyne complex has also been isolated in good yield, and this later forms mixtures of regioisomer metallacycles with many unsaturated organic compounds , . Other reactivities have also been developed, such as with chalcogens, and phosphaimines R 1 N=PR 2 R 3 ,…”