The synthesis and characterization of sterically encumbered terphenyl compounds are described. These are 2,6- and 1,3, 3, and the solvated metal derivatives Et 2 OLiC 6 H 3 -2,6-Trip 2 , 4, and Me 2 SCuC 6 H 3 -2,6-Trip 2 , 5. They were characterized by 1 H and 13 C NMR spectroscopy and, in the case of 3-5, by X-ray crystallography. The monomeric structures of 4 and 5 and the two-coordinate nature of the metals underline the very bulky characteristics of these ligands. In addition the isolation of 3 rather than the intended iodine derivative 2,6-Mes* 2 C 6 H 3 I suggests that the synthetic route to the precursor halides can be limited by very large ring substituents.

The reaction of 1 equiv of (Et 2 O)LiC 6 H 3 -2,6-Trip 2 (Trip ) C 6 H 2 -2,4,6-i-Pr 3 ) with either GeCl 2 -dioxane or SnI 2 in ether affords the synthetically useful monomeric aryl-metal halides Ge(Cl){C 6 H 3 -2,6-Trip 2 } (1) and Sn(I){C 6 H 3 -2,6-Trip 2 } (2). The compounds have monomeric structures with two-coordination and v-shaped geometries at the group 14 element in the solid state. Treatment of the amide Sn{N(SiMe 3 ) 2 } 2 with (Et 2 O)LiC 6 H 3 -2,6-Trip 2 results in displacement of an amide group to afford the mixed aryl/amide species Sn{N(SiMe 3 ) 2 }-{C 6 H 3 -2,6-Trip 2 } (3), which also has a monomeric v-shaped geometry in the solid state. † Dedicated to Professor P. Jutzi on the occasion of his 60th birthday.

Stabilized only by steric effects and weak solvation by benzene, the aryllithium compound 1 exists as a monomeric benzene adduct. The unique structure of 1 in the solid state is shown on the right; the ortho substituents on the η1‐bound phenyl ring have been omitted for clarity.

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.32)(&mgr;-OH)](2).2C(6)H(6) (12). The structures of 2, 3a, 4, 6, 7, 9a, 10a, 10b, 11, and 12 were determined by X-ray crystallography. The structures of 3a, 9a, 10a, and 10b, are related to 3, 9, and 10, respectively, by partial occupation of chloride or hydride by hydroxide. The compounds were also characterized by (1)H, (13)C, (7)Li, and (27)Al NMR and IR spectroscopy. The major conclusions from the experimental data are that a single ortho terphenyl substituent of the kind reported here are not as effective as the ligand Mes (Mes = 2,4,6-t-Bu(3)C(6)H(2)-) in preventing further coordination and/or aggregation involving the aluminum centers. In effect, one terphenyl ligand is not as successful as a Mes substituent in masking the metal through agostic and/or steric effects.

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