176507-46-3Relevant academic research and scientific papers
Stable mononuclear, 17-electron molybdenum(III) carbonyl complexes. Synthesis, structure, thermal decomposition, and Cl- addition reactions
Fettinger, James C.,Keogh, D. Webster,Poli, Rinaldo
, p. 3617 - 3625 (2007/10/03)
The first examples of stable, mononuclear 17-electron carbonyl complexes of Mo(III) have been synthesized, isolated, and characterized by IR and EPR spectroscopy. Oxidation of Cp*MoCl(CO)(PMe3)2 (1; E( 1/2 ) = -0.48 V vs Fc/Fc+), Cp*MoCl(CO)(dppe) (2; E( 1/2 ) = -0.44 V), and CpMoCl(CO)(dppe) (3; E( 1/2 ) = -0.25 V) with Fc+PF6- yields [1]PF6, [2]PF6, and [3]PF6, respectively. The IR stretching vibration of the 17-electron oxidation products are 136-153 cm-1 blue-shifted with respect to the corresponding stretching vibrations of the parent Mo(II) compounds. The room temperature EPR spectra show observable coupling to the Mo and P nuclei and indicate a trans geometry for 1+ and a cis geometry for 2+ and 3+. The four-legged piano stool geometry of 2+ with the phosphines atoms in relative cis positions has been confirmed by a single-crystal X-ray analysis. The X-ray data for [2]PF6·THF are the following: monoclinic, P21/n, a = 13.7394(14) A?, 6 = 20.421(2) A?, c = 14.857(2) A?, β = 99.119(8)°, V = 4115.8(8) A?3, Z = 4 D(x) = 1.469 g·cm-3, λ(Mo Kα) =0.71073 A?, μ (Mo Kα) = 0.562 mm-1, R(F) = 4.59%, R(wF2) = 10.77% for 4299 data with E(o) > 4σ(F(o)) The thermal stability of the cations decreases with increasing carbonyl stretching frequencies in the order 1+ > 2+ >> 3+. The decarbonylated product of thermolysis of 3+, [CpMoClF(dppe)(MeCN)]+PF6-, [4]PF6, which is believed to arise via a 15-electron [CpMoCl(dppe)]+ intermediate, has been isolated and characterized by 1H, 31P, and 19F NMR spectroscopies as well as a single-crystal X-ray analysis. The structure of 4+ shows a distorted pseudooctahedral geometry with the Cp ring and the F atom occupying the two axial coordination sites and the two phosphine atoms of the dppe occupying two cis equatorial sites. The data for [4]PF6·MeCN are as follows: monoclinic, P21/n, a = 13.160(2) A?, b = 10.942(2) A?, c = 25.010(3) A?, β = 95.225(10)°, V = 3586.4(9) A?3, Z = 4, D(x) = 1.557 g·cm-3, μ(Mo Kα) = 0.71073 A?, R(F) = 4.11% R(wF2) = 11.81% for 5964 data with F(o) > 4σ(F(o)). The nucleophilic addition of Cl- to 1+, 2+, or 3+ is followed by redox processes to afford mixtures of the parent Mo(II) carbonyl complexes 1-3 and Mo(IV) or Mo(V) products, depending on the nature of the ligands. The mechanism of these reactions has been elucidated through parallel chemical and electrochemical studies.
