Experimental, Structural, and Theoretical Studies of Diplatinum Complexes Containing Bridging Phenylethenylidene Ligands Including the Excited-State Chemistry and Photophysics of Photochemically Generated Species

The results of a comprehensive investigation of the chemistry of the diplatinum compound [Pt2(μ-C=CHPh) (C≡CPh) (PEt3)4]BF4(1) and related derivatives are presented. Complex 1 reacts with halides, NCS^-, and various RS^-nucleophiles to give the neutral compounds [Pt2(μ-C=CHPh) (C=CPh) (PEt3)3X] with loss of one PEt3ligand. These Pt2X complexes react with acid and X^-nucleophile to give the neutral compounds [Pt2(μ-C=CHPh)(PEt3)3X2] upon loss of phenylacetylene. The X-ray structures of the Pt2Cl, Pt2I, and Pt2Br2complexes have been determined. [Pt2(μ-C=CHPh(C≡CPh)(PEts3)3Cl]: monoclinic; P21/c; Z = 4; a = 11.685 (1) A, b = 20.810 (7) A, c = 19.172 (4) A; β = 123.96 (1)°. [Pt2(μ-C=CHPh)-(C≡CPh)(PEt3)3I]: orthorhombic; Pbca; Z = 8; a = 18.004 (3) A, b = 22.805 (4) A, β= 19.328 (4) A. fPt2(μ-C=CHPh)(PEt3)3Br2]: monoclinic; Cc; Z = 8; a = 10.359 (1) A, b = 33.054 (9) A, c = 19.855 (5) A; β = 93.40 (2)°. SC-MEH-MO calculations of the electronic structure of compound 1 indicate a large negative charge on each of the Pt atoms which is reminiscent of the results reported earlier from similar calculations on the anion Pt2(P2O5H2)4^4-. Similarities between the photochemistry of the complexes reported herein and that known for Pt2(P2O5H2)4^4-are presented. Complex 1 reacts with Mel under photolysis to give Pt2I and Pt2I2, and it reacts as a catalyst under photolysis to produce acetone and molecular hydrogen from 2-propanol. The complex Pt2Cl emits a red-orange luminescence at 696 nm in a 4:1 ethanol/methanol matrix at 77 K upon excitation at 410 nm. This luminescent state has an average lifetime of 1.7 μs and is attained with an “optical” quantum yield of 0.010 (2). © 1989, American Chemical Society. All rights reserved.

Duke Scholars

Author Andrew T. McPhail Chemistry