Pentacoordinated diolefinic rhodium(I) organocomplexes with α-diimine ligands.: Crystal structures of [Rh(Nbd)(LL)(PPh3)]ClO4 (Nbd = norbornadiene;: LL = Bdh, biacetylidihydrazone;: Pvdh, pyruvaldihydrazone;: Bda, biacetyldianil)

Pentacoordinated [Rh(Nbd)(LL)(PPh3)]ClO4 (Nbd = norbornadiene; LL = biacetyldihydrazone (Bdh) (1), pyruvaldehydedihydrazone (Pvdh) (2), glyoxaldihydrazone (Gdh) (3), biacetyldianyl (Bda) (4)) complexes are studied. The molecular structures of 1, 2, and 4 have been determined by X-ray diffraction. The three cations are best described as having distorted trigonal bipyramidal geometry with the olefinic bonds of Nbd spanning axial-equatorial sites; in 1 and 2 the other equatorial positions are occupied by the diimine groups and the PPh3 is in axial position while in 4 the diimine occupies axial-equatorial sites and the PPh3 is in equatorial position. Complexes 1 and 2 show intermolecular hydrogen bond N-H ... OClO3 linkages, strong in 2. In acetone solution compounds 1-4 undergo phosphine dissociation, inhibited at 273 K; 2, 3 and 4 behave as dimers with bridging diimine ligands. Neutral pentacoordinated [Rh(X)(L-2)(LL)] (X=Cl, SnCl3; L-2=Nbd, 1,5-cyclooctadiene (Cod); LL=Pvdh, Gdh) compounds undergo ionic dissociation in solution where at 183 K [Rh(SnCl3)(Nbd)(Pvdh)] shows a square pyramidal structure with SnCl3 in apical position. (C) 2000 Elsevier Science S.A. All rights reserved.