Articles Divergent Isomerization Behavior and Rhodium(I) Coordination Chemistry of Indenyl Ligands Bearing either One or Two Pnictogen Donor Fragments Judy Cipot, Dominik Wechsler, and Mark Stradiotto* Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3 Robert McDonald and Michael J. Ferguson X-ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 Received July 21, 2003 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 crystallographi- cally determined structures of 2d, 3‚C 6 H 6 , 7, and 10‚C 7 H 8 are reported. Introduction Transition-metal complexes supported by π-coordi- nated η 5 -indenyl ligands have a longstanding history in the field of organometallic chemistry and continue to figure importantly in current research. 1 In particular, main-group-functionalized indenyl ligands have at- tracted considerable attention, 2 since they have been shown to impart interesting reactivity properties to both early- and late-transition-metal fragments. 3 Recently we reported the synthesis of the P,N-functionalized indene 2a and demonstrated that this versatile ligand system can be used in the preparation of neutral (3), cationic (4), and zwitterionic (5) Rh(I) complexes (Scheme 1); compounds 4 and 5 have been shown to catalyze the dehydrogenative coupling of triethylsilane and styrene. 4 During the course of this study we observed that (a) the clean conversion of 3 into 4 is accompanied by a structural rearrangement of the indene ligand in which the formerly allylic (C1) i Pr 2 P substituent is placed at the vinylic (C3) position and (b) in stark contrast to the numerous (η 4 -COD)Rh(η 5 -indenyl) (COD ) 1,5-cyclooc- tadiene) complexes, 5 the [(η 4 -COD)Rh] + fragment in 5 selectively binds in a κ 2 -P,N fashion to the periphery of the carbanion generated upon deprotonation of 2a, rather than coordinating in the usual η 5 manner to the face of the carbocyclic framework. In light of these observations, we became interested in preparing directly the ligand 2b (i.e. the C3 isomer of 2a) and in gaining a better understanding of the factors that favor the unusual κ 2 bonding arrangement found in 5. Herein we * To whom correspondence should be addressed. E-mail: mark.stradiotto@dal.ca. (1) (a) Calhorda, M. J.; Veiros, L. F. Coord. Chem. Rev. 1999, 185- 186, 37. (b) Lobanova, I. A.; Zdanovich, V. I. Russ. Chem. Rev. (Engl. Transl.) 1988, 57, 967. (2) Stradiotto, M.; McGlinchey, M. J. Coord. Chem. Rev. 2001, 219- 221, 311. (3) For some recent examples, see: (a) Xie, Z. Acc. Chem. Res. 2003, 36, 1. (b) Fan, W.; Waymouth, R. M. Macromolecules 2003, 36, 3010. (c) Lee, M. H.; Han, Y.; Kim, D.; Hwang, J.-W.; Do, Y. Organometallics 2003, 22, 2790. (d) Kamigaito, M.; Watanabe, Y.; Ando, T.; Sawamoto, M. J. Am. Chem. Soc. 2002, 124, 9994. (e) Greidanus, G.; McDonald, R.; Stryker, J. M. Organometallics 2001, 20, 2492. (4) Stradiotto, M.; Cipot, J.; McDonald, R. J. Am. Chem. Soc. 2003, 125, 5618. (5) For some recently reported Rh(η 5 -indenyl) complexes, see: (a) Santi, S.; Ceccon, A.; Carli, F.; Crociani, L.; Bisello, A.; Tiso, M.; Venzo, A. Organometallics 2002, 21, 2679. (b) Santi, S.; Ceccon, A.; Crociani, L.; Gambaro, A.; Ganis, P.; Tiso, M.; Venzo, A.; Bacchi, A. Organome- tallics 2002, 21, 565. (c) Schumann, H.; Stenzel, O.; Dechert, S.; Girgsdies, F.; Blum, J.; Gelman, D.; Halterman, R. L. Eur. J. Inorg. Chem. 2002, 211. (d) Rupert, K. C.; Liu, C. C.; Nguyen, T. T.; Whitener, M. A.; Sowa, J. R., Jr. Organometallics 2002, 21, 144. (e) Westcott, S. A.; Kakkar, A. K.; Taylor, N. J.; Roe, D. C.; Marder, T. B. Can. J. Chem. 1999, 77, 205. 5185 Organometallics 2003, 22, 5185-5192 10.1021/om0340589 CCC: $25.00 © 2003 American Chemical Society Publication on Web 10/18/2003