Bis(phthalocyaninato(2–)rhenium(II)): Synthesis,Properties, and Crystal Structure

Blue, paramagnetic bis(phthalocyaninato(2–)rhenium(II)) (μ_eff = 0,88 μ_B, per Re, at 300 K) is prepared by thermal decomposition of trans-bis(triphenylphosphine)phthalocyaninato(2–)rhenium(II), in boiling triphenylphosphine. It crystallizes in the triclinic space group P 1 with cell parameters as follows: a = 7.799(3) Å, b = 12.563(7) Å, c = 12.69(1) Å, α = 89.97(5)°, β = 94.14(5)°, γ = 106.39(4)°; Z = 1. Two cofacial phthalocyaninates are bonded together by a Re–Re bond with a Re–Re distance of 2.285(2) Å. The Re atoms are located distinctly outside the centre of the (N_iso)₄ planes by 0.426(3) Å. The Re–N_iso distance varies from 1.99(1) to 2.04(1) Å (average 2.02 Å). The pc^2– ligands are in an eclipsed conformation and concavely distorted. In the UV-VIS-NIR spectrum the B region is split into two bands of comparable intensity due to strong excitonic coupling. The Re–Re stretching vibration at 240 cm^–1 is selectively enhanced in the resonance Raman spectrum (λ_exc = 488 nm).