Isolation and Chemistry of Aluminum Compounds Containing (S)-3,3‘-Bis(triphenylsilyl)-1,1‘-bi-2,2‘-naphthoxide Ligands

The reaction of the resolved, bulky binol (S)-3,3'-bis(triphenylsilyl)-2,2'-dihydroxy-1,1'-binaphthyl, (S)-H 2 O 2 C 2 0 H 1 0 {SiPh 3 } 2 -3,3' (1), with a variety of alkyl and amide compounds has been investigated. Reaction of 1 with [Al 2 Me 6 ] initially proceeds only in a 1:1 ratio to produce dinuclear [Al 2 (O 2 C 2 0 H 1 0 {SiPh 3 ) 2 -3,3')(CH 3 ) 4 ], (S)-2. Compound 2 contains a [Al(μ-C)(μ-O)] core, Al-Al = 2.739(2) A, with the binaphthoxide ligand oxygen atoms occupying terminal and bridging positions. In the presence of pyridine, 2 reacts further with 1 to produce [Al(O 2 C 2 0 H 1 0 {SiPh 3 } 2 -3,3')(CH 3 )(py)], (S)-4. The ethyl analogue of 4, [Al(O 2 C 2 0 H 1 0 {SiPh 3 } 2 -3,3')(CH 3 )(py)], (S)-5, was obtained from [Et 2 AlCl]. Both 4 and 5 were shown to adopt tetrahedral geometries in the solid state with O-Al-O angles of ∼107°. Reaction of [LiAl-(NMe 2 ) 4 ] with 1 produced a dinuclear compound, [LiAl(O 2 C 2 0 H 1 0 {SiPh 3 ) 2 -3,3')(NHMe 2 )-(NMe 2 ) 2 ], (S)-6, containing a terminal and bridging amido group. The lithium-bound HNMe 2 ligand could be substituted by pyridine to produce [LiAl(O 2 C 2 0 H 1 0 {SiPh 3 } 2 -3,3')(NC 6 H 5 )-(NMe 2 ) 2 ], (S)-7. In the solid state the formally three-coordinated lithium atoms in 6 and 7 are pyramidalized. The sum of the three angles for the LiN 2 O core is 305° and 322° for 6 and 7, respectively. This is due to an interaction of the lithium with one arene ring of an SiPh 3 group. In 6 the carbon atoms involved are an ipso- and ortho-carbon, while for 7 the ortho- and meta-carbon atoms of a Ph-Si ring are in close contact.