Divergent Isomerization Behavior and Rhodium(I) Coordination Chemistry of Indenyl Ligands Bearing either One or Two Pnictogen Donor Fragments

1-(Diphenylphosphino)-2-(dimethylamino)indene ( 2c ) has been prepared in 61% yield and upon exposure to Al 2 O 3 is mostly isomerized to 3-(diphenylphosphino)-2-(dimethylamino)indene ( 2d ) ( 2c: 2d ≈ 1:3); similarly, 1-(diisopropylphosphino)-2-(dimethylamino)indene ( 2a ) is only partially converted to the corresponding C3 isomer ( 2b ) upon treatment with Al 2 O 3 ( 2a: 2b ≈ 3:1). In contrast, 1-(diisopropylphosphino)indene ( 6a ) has been prepared in 92% yield and is easily converted to 3-(diisopropylphosphino)indene ( 6b ) on passing over Al 2 O 3; 0.5 equiv of [(η 4 -COD)RhCl] 2 and 6b combine to give [(κ 1 - P - 6b )(η 4 -COD)RhCl] ( 7 ) in 79% yield. Treatment of either 2-(dimethylamino)indene ( 1 ) or 6b with a stoichiometric amount of n -BuLi, followed by the addition of 0.5 equiv of [(η 4 -COD)RhCl] 2, produces the (η 5 -indenyl)rhodium(I) complexes 8 (53% yield) and 9 (88% yield), respectively, in which the pnictogen donor is apparently not coordinated to the rhodium center. When 2.5 equiv of n -BuLi is combined with 6b and subsequently treated with 0.5 equiv of [(η 4 -COD)RhCl] 2, 9 is also produced, along with a small amount of the unusual Rh 2 Li 2 species 10 . The crystallographically determined structures of 2d, 3 ·C 6 H 6, 7, and 10 ·C 7 H 8 are reported.