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 Al2O3 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 Al2O3
(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 Al2O3;
0.5 equiv of [(η4-COD)RhCl]2 and 6b combine to give [(κ1-P-6b)(η4-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 [(η4-COD)RhCl]2, produces the (η5-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 [(η4-COD)RhCl]2, 9 is also
produced, along with a small amount of the unusual Rh2Li2 species 10. The crystallographically determined structures of 2d, 3·C6H6, 7, and 10·C7H8 are reported.