The secondary phosphines R(Ar*)PH(R = Me, iPr, Ph, Mes, Ar*) (2a-2h) with bulky aromatic substituents Ar* (Ar* = 2,3,6-R′ 3C6H2, R′ = iPr, tBu) are obtained in good yields by reaction of RPCl2, PCl3, PBr3 or Ar*P(Cl, Br)2 with 2,4,6-tBu3C6H2Li or 2,4,6- iPr3C6H2MgBr and subsequent reduction of the intermediate halophosphines R(Ar*)PX(X = Cl, Br) with LiAlH4. The X-ray structural analysis of Ph(2,4,6-iPr3C6H2)PH (2g), space group P1, shows P-C-distances of 1.824(1) and 1.838(1)Å. The lithium derivatives of 2a-2c are monomeric in solution as indicated by the 1 :1 :1 : 1-quartet 7L i - 31P fine structure of the 31P {1H} NMR signals at low temperatures. 2a-2c and 2f-2h form Ni(0) and Fe(0) complexes (CO)3NiL (6a-6f) and Fe(CO)4L (7a-7d), respectively. The Tolman electronic parameters of the bulky ligands are almost identical. Within the series 2a-2h the spatial shielding of the P atoms has been estimated using advanced molecular modeling techniques. The bulky ligand 2c forms coinage metal complexes [C u(CH3CN)2(2c)2] [PF6] (8), Cu2Cl2(2c)2 (9) and Cl-Au(2c) (10). While 10 is monomeric in solution, in the solid state it forms pairs of head to tail oriented monomers with almost linear Cl - Au - P skeletons (Cl - Au - P 175.47(9)°) as shown by an X-ray structural analysis.
Synthesis and Characterization of Super Bulky β-Diketiminato Group 1 Metal Complexes