Synthesis and rhodium complexes of macrocyclic PNP and PONOP pincer ligands

Abstract

A new dimension in pincer chemistry: introducing phosphine-based macrocyclic pincer ligands PNP-14 and PONOP-14.

Synthesis and group 9 complexes of macrocyclic PCP and POCOP pincer ligands

“…These data suggest that PCP-14 and POCOP-14 are marginally weaker donors than PCP-tBu and POCOP-tBu, respectively, consistent with similar findings for the neutral PNP and PONOP analogues and attributed to changes in the phosphine/phosphinite substituents alone. 6 Other trends apparent in the IR data associated with the extent of π-backbonding increasing in the order Ir > Rh, M(I) > M(III) and PCP > POCOP are fully in line with expectation and reinforced by similar trends in the X-ray derived metrics (Table 1) and NMR data (see Experimental section).…”

“…Likewise, attempted conversion of 2 to the corresponding borane protected chlorodialkylphosphine by acidolysis with HCl was unsuccessful. Instead the five step racemic synthesis outlined in Scheme 2, adapted from our work with PNP-14 and PONOP-14 and also involving ring-closing olefin metathesis, 6 was employed with the borane protected (saturated) macrocycle 12 proving to be the most conducive to resolution of the two diastereoisomers by column chromatography (cis-12, δ 31P 143.7; trans-12, δ 31P 143.8) and enabling determination of their respective configurations by single crystal X-ray diffraction (Fig. 1).…”

“…1 H NMR (500 MHz, toluene-d 0 , H 2 , selected data): δ 6.67 (d, 3 J HH = 7.9, 2H, Ar), 1.07 (vt, J PH = 7.5, 18H, tBu), −8.26 (t, 2 J PH = 9.9, 4H, IrH). 1 H NMR (500 MHz, toluene-d 8 ): δ 6.86 (t, 3 J HH = 7.9, 1H, Ar), 6.70 (d, 3 J HH = 7.9, 1H, Ar), 6.70 (d, 3 J HH = 7.9, 1H, Ar),…”

“…The preparation of analogous lutidine-and 2,6-dihydroxypyridine-derived PNP-14 and PONOP-14 ligands was described in a preceding contribution. 6…”

“…NMR (300 MHz, C 6 D 6 ): δ 7.43 (s, 1H, Ar{2-CH}), 7.04 (t,3 J HH = 8.0, 1H, Ar),6.95 (d, 3 J HH = 8.4, 2H, Ar), 5.76 (ddt, 3 J HH =16.8, 11.8, 6.7, 2H, CH̲ vCH 2 ), 4.95-5.10 (m, 4H, CHvCH̲ 2 ), 1.95 (app q, 3 J HH = 7, 4H, CH̲ 2 CHvCH 2 ), 1.75-1.90 (m, 2H, CH 2 ), 1.61 (app sex, J = 8, 4H, CH 2 ), 1.15-1.40 (m, 14H, CH 2 ), 1.04 (d, 3 J PH = 12.0, 18H, tBu).13 C{ 1 H} NMR (75 MHz, C 6 D 6 ): δ 161.0 (d, 2 J PH = 9.0, Ar{C}), 139.2 (s, C̲ HvCH 2 ), 130.2 (s, Ar), 114.6 (s, CHvC̲ H 2 ), 112.4 (d, 3 J PH = 11, Ar), 109.6 (t, 3 J PH = 12, Ar{2-CH}), 34.2 (s, C̲ H 2 CHvCH), 32.7 (d, 1 J PH = 16, tBu{C}), 31.5 (d, 2 J PH = 12, CH 2 ), 29.3 (s, CH 2 ), 29.2 (s, CH 2 ), 29.2 (d, 1 J PH = 24, PCH 2 ), 25.9 (d, 3 J PH = 16, CH 2 ), 25.4 (d, 2 J PH = 16, tBu{CH 3 }) 31 P{ 1 H} NMR (121 MHz, C 6 D 6 ): δ 142.40 (s, 1P), 142.36 (s, 1P). HR ESI-MS ( positive ion, 4 kV): 561.3231, [M + 2O + Na] + (calcd 561.3233) m/z.…”