Abstract
The parent tris(pyrazolyl)phosphine and its 3,5-Me2, 3-Ph, and 3-t-Bu derivatives have been prepared by a simple procedure and show modest Lewis basicity of the phosphorus apex as was established by the magnitude of the (1)JP,Se coupling constant of the phosphine selenides. Because of the chelating properties of both the N- and P-sites, neutral phosphorus-centered scorpion ligands allow coordination modes that are unavailable to the abundantly used anionic tris(pyrazolyl)borate scorpionates as we established for Cu(I)-complexation. The substituted P-scorpion ligands only allow for N-coordination, as the P-apex is presumably less accessible. Two X-ray crystal structures were obtained for the Cu-complex of tris(3,5-dimethylpyrazolyl)-phosphine with acetonitrile and triphenylphosphine in the fourth coordination site. The parent P-scorpion ligand can chelate with both its pyrazolyl groups and its P-apex with the product depending on the ratio in which it is mixed with the Cu(I) complex. Reacting two equivalents of the ligand with [Cu(MeCN)4][PF6] resulted in a complex in which Cu is coordinated to the three pyrazolyl groups of one ligand and to the P-apex of the other ligand as confirmed by an X-ray crystal structure determination and a DFT computational analysis. Reacting the ligand and the Cu(I) complex in an equimolar ratio resulted in a remarkable one-dimensional P-scorpion coordination polymer for which a single crystal X-ray structure could be determined. A detailed analysis of the structural features is presented.
Highlights
Tris( pyrazolyl)borates (A, Fig. 1) were first introduced by Trofimenko[1] in 1966 and became one of the most widely applied polydentate anionic ligands in coordination chemistry and catalysis because of their versatility and stability.[2–5]Neutral ligands result from changing the boron apex to a carbon one as in tris( pyrazolyl)methane (B)[6] for which ample syntheses have been reported.[7]
The parent tris( pyrazolyl)phosphine and its 3,5-Me2, 3-Ph, and 3-t-Bu derivatives have been prepared by a simple procedure and show modest Lewis basicity of the phosphorus apex as was established by the magnitude of the 1JP,Se coupling constant of the phosphine selenides
The parent P-scorpion ligand can chelate with both its pyrazolyl groups and its P-apex with the product depending on the ratio in which it is mixed with the Cu(I) complex
Summary
Tris( pyrazolyl)borates (A, Fig. 1) were first introduced by Trofimenko[1] in 1966 and became one of the most widely applied polydentate anionic ligands in coordination chemistry and catalysis because of their versatility and stability.[2–5]. Neutral ligands result from changing the boron apex to a carbon one as in tris( pyrazolyl)methane (B)[6] for which ample syntheses have been reported.[7]. Tris( pyrazolyl)phosphines have multiple coordination sites, making them well suited for ligation with more than one metallic complex. Janus-type ligands like tris(amidomethyl)phosphines with N- and P-coordination sites (Fig. 3c) have been deployed to form bimetallic complexes[39,40] and coordination polymers[41] with the Co–Y, Co–Gd, and Rh–Ti transition metal pairs. We present the synthesis of tris( pyrazolyl)phosphines C, their coordination with copper(I), and their Janus property to generate a one-dimensional coordination polymer. Both selenides were obtained as yellow powders after reaction of the parent compounds with an excess of selenium for two to three days in refluxing toluene, followed by filtration over silica, evaporation of the volatiles, and washing with pentane. The latter 1JP,Se coupling is at the high end of those reported
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