Organometallic complexes for nonlinear optics .14. Syntheses and second-order nonlinear optical properties of ruthenium, nickel and gold sigma-acetylides of 1,3,5-triethynylbenzene: X-ray crystal structures of 1-(HC C)-3,5-C6H3(C CRuCl(dppm)(2))(2) and 1,3,5-C6H3(C CAu(PPh3))(3)

The complexes 1-(HC=C)-3,5-C6H3[M](2) ([M] = trans-C=CRuCl(dppm)(2) (1), C=CNi(PPh3)(eta(5)-C5H5) (2)) and 1,3,5-C6H3(C= CAu(PPh3))(3) (3) have been prepared by extensions of well-established sigma-acetylide synthetic methodologies, and 1 and 3 have been structurally characterized. Steric restrictions preclude coordination of three trans-RuCl(dppm)(2) or Ni(PPh3)(eta(5)-C5H5) moieties about the central 1,3,5-triethynylbenzene unit, a problem which the smaller Au(PPh3) group does not experience. The quadratic optical nonlinearities at 1.06 mu m have been investigated by hyper-Rayleigh scattering with the C-2v symmetry complexes 1 and 2 having significantly larger beta(HRS) than their monometallic [M]C=CPh ([M] = trans-RuCl(dppm)(2) (4) and Ni(PPh3)(eta(5)-C5H5) (5)) counterparts. The D-3h symmetry octopolar complex 3 has a similar nonlinearity to its dipolar monometallic analogue Au(C=CPh)(PPh3) (6). Complexes 1, 2 and 3 have lambda(max) similar to 4, 5 and 6 (i.e., no loss of optical transparency is observed), but have significantly larger oscillator strengths for the important optical transitions. (C) 1997 Elsevier Science S.A.