Structural Basis for Unusually Long Wavelength Charge Transfer Transitions in Complexes [MCl(ECH 2 CH 2 NMe 2 )(PR 3 )] (E ) Te, Se; M ) Pt, Pd): Experimental Results and TD-DFT Calculations Sandip Dey, † Vimal K. Jain,* ,† Axel Kno 1 dler, ‡ Axel Klein, ‡ Wolfgang Kaim,* ,‡ and Stanislav Za ´lis ˇ § NoVel Materials and Structural Chemistry DiVision, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India, Institut fu ¨ r Anorganische Chemie, UniVersita ¨ t Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany, and J. HeyroVsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejs ˇkoVa 3, CZ-18223 Prague, Czech Republic Received November 28, 2001 A series of new complexes, the blue compounds [PdCl(TeCH 2 CH 2 NMe 2 )(PR 3 )] (PR 3 ) PEt 3 , PPr n 3 , PBu n 3 , PMe 2 Ph, PMePh 2 , PPh 3 , PTol 3 ) and the red [PtCl(TeCH 2 CH 2 NMe 2 )(PR 3 )] (PR 3 ) PMe 2 Ph, PMePh 2 ), were synthesized and studied spectroscopically ( 1 H and 31 P NMR, UV/vis) and by cyclic voltammetry. The structures of [PdCl(TeCH 2 - CH 2 NMe 2 )(PPr n 3 )] (2b) [PdCl(TeCH 2 CH 2 NMe 2 )(PMePh 2 )] (2e), [PtCl(TeCH 2 CH 2 NMe 2 )(PMePh 2 )] (2i), and the related [PtCl(SeCH 2 CH 2 NMe 2 )(PEt 3 )] (3) were determined crystallographically, revealing a typical pattern of trans-positioned neutral N and P donor atoms in an approximately square planar setting. The molecules 2b, 2e, and 2i were calculated by TD-DFT methodology to understand the origin of the weak (ǫ ≈ 200 M -1 cm -1 ) long-wavelength bands at about 600 nm for Pd/Te complexes such as 2b or 2e, at ca. 460 nm for Pt/Te systems such as 2i, and at about 405 nm for Pt/Se analogues such as 3. These transitions are identified as charge transfer transitions from the selenolato or tellurolato centers to unoccupied orbitals involving mainly the phosphine coligands for the Pt II compounds and more delocalized MOs for the Pd II analogues. Calculations and electrochemical data were used to rationalize the effects of metal and chalcogen variation. Introduction Metal-mediated interaction between coordinated ligands is an important aspect of coordination chemistry. As an example, the charge transfer interactions between metal- bound donor and acceptor centers have been recognized and described qualitatively in planar complexes of group 10 metals with thiolato donors and R-diimine acceptors. 1,2a-c The possible function of organophosphines as acceptor components for charge transfer transitions in complexes has been reviewed recently. 2d In this work we present a study which involves Pd II - or Pt II -bound selenolate or tellurolate donors and triorganophosphines as acceptors in complexes [MCl(ECH 2 CH 2 NMe 2 )(PR 3 )] (E ) Se, Te; M ) Pd, Pt). This combination of heavier elements for main group donor, acceptor, and transition metal mediator poses a formidable challenge for quantum chemical calculations which we sought to interpret the unusual long-wavelength absorptions in a more quantitative way; corresponding methods such as relativistic time-dependent density functional theory (TD- DFT) have only recently become applicable to such large systems containing heavy elements. 3 Based on the crystallographically determined structures of compounds [PdCl(TeCH 2 CH 2 NMe 2 )(PPr n 3 )] (2b), [Pd- Cl(TeCH 2 CH 2 NMe 2 )(PMePh 2 )] (2e), and [PtCl(TeCH 2 CH 2 - NMe 2 )(PMePh 2 )] (2i) we present TD-DFT calculations and electrochemical measurements to understand the conspicuous * Authors to whom correspondence should be addressed. E-mail: kaim@iac.uni-stuttgart.de (W.K.); jainvk@apsara.barc.ernet.in (V.K.J.). ² Bhabha Atomic Research Centre. ‡ Universita ¨t Stuttgart. § Heyrovsky Institute. (1) (a) Paw, W.; Lachicotte, R. J.; Eisenberg, R. Inorg. Chem. 1998, 37, 4139. (b) Cummings, S. D.; Eisenberg, R. J. Am. Chem. Soc. 1996, 118, 1949. (c) Connick, W. B.; Gray, H. B. J. Am. Chem. Soc. 1997, 119, 11620. (2) (a) Vogler, A.; Kunkely, H. Top. Curr. Chem. 1990, 158, 1. (b) Kunkely, H.; Vogler, A. J. Organomet. Chem. 1993, 453, 269. (c) Kunkely, H.; Vogler, A. Inorg. Chim. Acta 1997, 264, 305. (d) Vogler, A.; Kunkely, H. Coord. Chem. ReV., in press. (3) Rosa, A.; Baerends, E. J.; van Gisbergen, S. J. A.; van Lenthe, E.; Groeneveld, J. A.; Snijders, J. G. J. Am. Chem. Soc. 1999, 121, 10356. Inorg. Chem. 2002, 41, 2864-2870 2864 Inorganic Chemistry, Vol. 41, No. 11, 2002 10.1021/ic011210v CCC: $22.00 © 2002 American Chemical Society Published on Web 05/07/2002