The synthesis and structural characterisation of some azo-containing phosphine chalcogenides and comparison to non-phosphorus-containing analogues

Abstract

p-HO-Ph(Ph₂)P(E) (E = S, 1b, Se, 1c) reacts with the diazonium salts [4-R-PhNN][BF₄] (R = H, Me, Et, ⁱPr, ^tBu, NMe₂, NO₂) to afford the new compounds [1-HO-2-(4-R-PhNN)-4-Ph₂P(E)C₆H₃] (E = S, R = H, 2a; Me, 2b; Et, 2c; ⁱPr, 2d; ^tBu, 2e; NMe₂, 2f; NO₂, 2g; E = Se, R = H, 2h; Me, 2i) in acceptable yield. Similarly m-HO-Ph(Ph₂)P(S) 3 reacts with two molar equivalents of the diazonium salts [4-R-PhNN][BF₄] (R = H, Me, NMe₂, NO₂) to give the new compounds 1-HO-2,4-(4-R-PhNN)-3-Ph₂P(S)-C₆H₂4a–d (R = H, 4a; Me, 4b; NMe₂, 4c; NO₂, 4d). All of the new compounds have been characterised by elemental analysis, ¹H, ³¹P-{¹H}, ¹³C-{¹H}-NMR spectroscopy and in selected cases UV–visible spectroscopy. The selectivity in the substitution reactions of 3 with the diazonium salts is influenced not only by the steric bulk of the Ph₂PS moiety but by the ortho-effect too. These data have been compared to those obtained from analogous coupling reactions between m-cresol and one and two molar equivalents of [4-Me-PhNN][BF₄] which afford 1-HO-3-CH₃-4-(4-Me-PhNN)C₆H₃5 and 1-HO-3-CH₃-2,4-(4-Me-PhNN)C₆H₂6 respectively. The compounds 2b·0.55CH₂Cl₂·0.2C₆H₁₄, 4b·CH₂Cl₂, 5 and 6b have been further characterised by X-ray crystallography.