Preparation,viaDouble Oxidative Addition, and Characterization of Bimetallic Platinum and Palladium Complexes:  Unique Building Blocks for Supramolecular Macrocycles.¹³C NMR Analysis of the Nature of the Palladium−Carbon Bond

Abstract

The high-yield preparation, by double oxidative addition, of nine novel platinum and palladium bis(trans-M(PR3)2X)aryl (M = Pt or Pd; R = PPh3 or PEt3; X = Br or I; aryl = 1,4-benzene, 4,4‘-biphenyl, 4,4‘‘-ter-p-phenyl, 4,4‘-tolane, or 4,4‘-benzophenone) complexes from the reaction of Pt(PPh3)4, Pt(PEt3)4, or Pd(PPh3)4 with the respective dihalo aromatic in toluene is described. These complexes were fully characterized by elemental analysis, mass spectrometry, and NMR (1H, 13C{1H}, and 31P{1H}) and vibrational (IR or Raman) spectroscopies. The single-crystal molecular structure of 4,4‘-bis(trans-Pt(PEt3)2I)biphenyl (2a) was determined by X-ray crystallography. The key structural feature of this complex is the dihedral angle of 18.9° between the two planes defined by the phenyl groups of the biphenyl linkage. The nature of the palladium−carbon bond is investigated by 13C{1H} NMR spectroscopy; Taft's σR parameter is found to correlate in a linear fashion with [δ(C ipso ) − δ(C o )] for these palladium complexes. These data indicate the 13C chemical shift of C ipso is linearly related to the amount of π-electron density of the carbon bound to the palladium center. The potential utility of these bimetallic platinum and palladium complexes as subunits in the generation of organometallic macrocycles is described.

Formation of Metallamacrocycles from Palladium(II), Platinum(II) and Copper(I) Complexes and the Ditopic Ligands [{p-(Ph2PO)C6H4}2CMe2], [{2-Ph2PO-3,5-(Me3C)2C6H2}2S], [{p-[(C10H6O)2PO]C6H4}2CMe2]

“…Another consequence of the ligand geometry is that when ligand 3 was used in the reaction with [Ru(η 6 -p-cymene)Cl 2 ] 2 , only the dinuclear complex {[Ru(η 6 -p-cymene)Cl 2 ] 2 [µ-(p-Ph 2 POC 6 H 4 ) 2 C(Me) 2 ]} was obtained [6] and attempts to ob- [11] A very interesting aspect connected with the formation of metallamacrocycles is the introduction of chirality by suitable self-assembly building blocks. In the case of 4, only the Cu I -based dinuclear macrocycle was formed with this ligand.…”

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

“…solution of the neutral cis-platinum complexes 114 to the solid bistriflate monomers 124a-d 130,131 resulted in the quantitative formation of the squares 125a-d (Scheme 46), respectively, of differing topology and dimensions. 132 Interestingly, it was found that the self-assembly of macrocycle 125c was concentration dependent.…”

Self-assembly of nanoscopic coordination cages of D 3h symmetry

“…Double oxidative addition to rigid aromatic ligands offers a unique way to direct the open coordination sites of metals (46), because nearly any desired angle can be fashioned provided the corresponding aryl halide is accessible. Presented here is a ligand-directed approach to molecular prisms, thus providing a versatile method for the construction of supramolecular structures of variable size and functionality, in high yield, and without the use of templates.…”