Re Tricarbonyl Complexes with Ligands Containing P,N,N and P,N,O Donor Atom Sets: Synthesis and Structural Characterization

The coordination chemistry of the heterofunctionalized phosphines HPN2 and H2PNO and of an analogue containing
a relevant biomolecule, HPN-Pip (Pip = 4-(3-aminopropyl)-1-(2-methoxyphenyl)piperazine), was studied toward
the synthon (NEt4)2[ReBr3(CO)3]. The complexes isolated, [Re(CO)3(κ3-PN2)], 3, [Re(CO)3Br(κ2-H2PNO)], 4,
and [Re(CO)3Br(κ2-HPN-Pip)], 5, are the first examples of Re(I) compounds stabilized by such a combination of
donor atoms. All of the compounds are neutral, but the phosphines, depending on the combination of atoms, act
as monoanionic and tridentate (3) or as neutral and bidentate (4, 5). The characterization of 3−5 included IR, 1H
NMR, and 31P NMR spectroscopy and X-ray crystallographic analysis. Colorless crystals of compounds 3 and 4
were obtained by slow evaporation of a methanolic solution of 3 and from a boiling acetonitrile solution of 4.
Compound 3 crystallizes with two molecules of MeOH per asymmetric unit in the monoclinic space group P21/c,
a = 10.1237(8) Å, b = 9.4959(4) Å, c = 28.365(2) Å, β = 98.707(9)°, V = 2695.4(3) Å3, Z = 4; 4 crystallizes
in the triclinic space group P1̄, a = 10.0241(9) Å, b = 11.2060(10) Å, c = 13.0656(12) Å, α = 84.883(11)°, β
= 71.163(10)°, γ = 63.650(9)°, V = 1241.19(19) Å3, Z = 2.