Heterobimetallic indenyl complexes. Synthesis and structure of cis-[Cr(CO)3(indenyl)RhL2 (L2 = norbornadiene, (CO)2)

Reaction of the potassium salt of [(eta6-indenyl)Cr(CO)3] at -30-degrees-C in THF with [Rh(Cl)NBD]2(NBD = norbornadiene) yields cis-[Cr(CO)3(indenyl)] Rh-(NBD), 2. Bubbling CO through a CH2Cl2 solution of 2 produces cis-[Cr(CO)3(indenyl)]Rh(CO)2, 3 in quantitative yield. X-ray analyses show for indenyl-Rh-(NBD), 1: a = 17.506(8) angstrom, b = 11.427(6) angstrom, c = 5.979(4) angstrom, beta = 90.8(2)degrees, space group P2(1)/n. For 2: a = 11.098(6) angstrom, b 17.684(8) angstrom, c = 8.253(5) angstrom, beta = 99.7(2)degrees, space group P2(1)/a. For 3: a = 16.558(8) angstrom, b 12.483(8) angstrom, c = 6.629(4) angstrom, space group P2(1)2(1)2(1). Both 2 and 3 have a doubly-bent indenyl moiety and show strongly distorted coordination modes toward the indenyl ligand of both metals. The driving force leading to such highly distorted structures probably arises mainly from a metal-metal interaction.