Synthesis and coordination chemistry of new asymmetric donor/acceptor pincer ligands, 1,3-C6H4((CH2PBu)-Bu-t(R-f))(2) (R-f = CF3, C2F5)

摘要

Syntheses of new asymmetric pincer precursors 1,3-C6H4{CH2P(Bu-t,X)}(2) ((PCPH)-P-tBu,X; X = Cl, SiMe3, OPh) and a new class of hybrid donor/acceptor pincer ligands 1,3-C6H4{CH2P(Bu-t,R-f)}(2) ((PCPH)-P-tBu,Rf; R-f = CF3, C2F5) are reported. All (PCPH)-P-tBu,X compounds are obtained as mixtures of meso and rac diastereomers in varying ratios (meso:rac approximate to 4:1 to 3:2) which were used without separation. Treatment of Ru(cot)(cod) with (3PCPH)-P-tBu,CF under 1 atm H-2 in acetone at 20 degrees C produced the hydride solvate ((3PCP)-P-tBu,CF)Ru(acetone)(x)H which was not isolated, but could be trapped as stable diene complexes ((3PCP)-P-tBu,CF)Ru(L)(2)H (L-2 = cod (1_), nbd (2_)). Catalytic cyclooctane dehydrogenation studies demonstrate that 2_ has approximate to 50% the activity of ((3PCP)-P-CF)Ru(cod)(H), but significantly higher catalyst stability and is able to operate at higher catalyst loading concentrations without deactivation via bimolecular decomposition.