Generation of Bis[2,6-di(4-methoxy-phenyl)phenyl]plumbylene and its Insertion into n-Butyliodide to Give a Tetrahedral Triorganolead(IV) Iodide

Abstract

1 -Iodo-2,6-bis(4-methoxy-phenyl)benzene (BipapI) was prepared in a Grignard reaction from 4-bromo-anisol and 2,6-dibrom o-1 -iodo-benzene in tetrahydrofuran (61% yield). Treatment of BipapI with Az-butyllithium in hexane/diethylether gave the corresponding terphenyl-lithium compound BipapLi which crystallized as the dietherate in 83% yield. The structure of BipapLi • (OE2)2 has been determined by single crystal X-ray methods. The molecule is a monomer in the lattice, and the lithium atom is three-coordinate. Preparation of BipapLi in the presence of PbCl2 in diethylether gave a green solution, from which yellow crystalline (n -Bu)(Bipap)2Pbl was isolated in 73% yield. In the crystal this triorganolead(IV) iodide is monomeric and has tetrahedrally four-coordinate lead atoms.

Bis(μ-2,2′′-dimethoxy-m-terphenyl)di-μ3-iodo-bis(tetrahydrofuran)tetralithium(I)

“…In recent years, there have been a number of reports on crystal structure determinations of different terphenyl±lithium compounds. The solid-state structures of both hydrocarbonsoluble unsolvated compounds (Ruhlandt-Senge et al, 1993;Wehmschulte & Power, 1997), as well as of their Lewis-base adducts have been reported (Crittendon et al, 1999;Girolami et al, 1992;Olmstead & Power, 1991;Wegner et al, 2000). Such lithium derivatives are typically employed as transfer reagents.…”

Synthesis and structure of two lithium terphenyls and a “halide rich” terphenyl lithium species

“…After the mixture was cooled to room temperature, it was filtered and the pale yellow solid was washed with methanol and dried. Yield: 8 Ar Pmp 2 I (3.24 g, 6.52 mmol) was dissolved in hexane (60 mL) and cooled to 0°C in an ice bath for 30 min. Bu n Li (2.75 mL of a 2.5-M solution in n-hexane) was added to solution via syringe with rapid stirring.…”

“…The core of the molecule comprises a planar Li 2-C(ipso)I unit which subtends a dihedral angle of 48.1°w ith respect to the plane of the central aryl ring. The [8] (1.954 Å ), 2,6-(4-t BuC 6 H 4 ) 2 -C 6 H 3 Li(OEt 2 ) 2 [9] (1.950 Å ), but are longer than those in 2,6-(2,6-i Pr 2 -4-t Bu) 2 C 6 H 3 Li(OEt 2 ) [10] (1.881 Å ); and 2,6-Trip 2 C 6 H 3 Li(OEt 2 ) [11] (1.850 Å ) where the lithium is two coordinate. The Li-I distances (2.738(3) and 2.751(3) Å ) also resemble those observed in the complex [2, H 4 ) 2 C 6 H 3 Li(THF)LiI] 2 [14], where the Li-I distance are 2.760 and 2.820 Å .…”

“…The lithium derivatives of these large aryls are the most widely used transfer agents, and their crystal structures have shown that their aggregation numbers are lower than the typically found four or six due to their steric bulk [3]. For example, monomeric terphenyl lithium structures can be stabilized with use of one or two ethers, THFs, or a benzene donor molecule as in 2,4,6-Ph 3 C 6 H 2 Li(OEt 2 ) 2 [5], 2,6-Ph 2 C 6 H 3 Li(OEt 2 ) 2 [6], 2,6-(1-Naph) 2 C 6 H 3 Li(THF) 2 -(Naph = C 10 H 7 ) [7], 2,6-(4-MeOC 6 H 4 ) 2 C 6 H 3 Li(OEt 2 ) 2 [8], 2,6-(4-t BuC 6 H 4 ) 2 C 6 H 3 Li(OEt 2 ) 2 [9], 2,6-(2,6-i Pr 2 -4-t Bu) 2 C 6 H 3 Li(OEt 2 ) [10], 2,6-Trip 2 C 6 H 3 Li(OEt 2 ) (Trip = 2,4,6-i Pr 3 C 6 H 2 ) [11], or 2,6-Trip 2 C 6 H 3 Li(g 6 -C 6 H 6 ) [12]. Currently, two types of base free dimeric structures are known.…”

Co-complexes of ortho-dilithiated thiophenol or 2-trimethylsilylthiophenol with lithiated TMEDA molecules: synthesis, crystal structures and theoretical studies (TMEDA = N,N,N′,N′-tetramethylethylenediamine)

“…This coordination may be due to the bulky TMEDA and CH 2 MeNCH 2 CH 2 NMe 2 groups which shield Li(3), leaving no space for another donor ligand. There are several examples of lithium compounds with a trigonalplanar geometry in the literature, but in most of them at least one of the coordination sites is occupied by a heteroatom (N or O) 16,[25][26][27][28][29][30][31][32][33][34][35][36][37]. The sulfur atom is coordinated to two lithium atoms with bond lengths [S(1)-Li(1) 2.375(4) A ˚, S(1)-Li(2) 2.417(4) A ˚] shorter…”