Ruthenium Complexes of a Simple Tridentate Ligand Bearing Two “Distal” Pyridine Bases

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Abstract
Treatment of N,N‘-bis(6-methyl-2-pyridinyl)-2,6-pyridinedicarboxamide (1) (H2LMe2) with RuCl2(PPh3)3 in toluene yields the complex RuCl2(PPh3)(LMe2{H}2) (2) in which the ruthenium atom is coordinated to the nitrogen atoms of the two deprotonated amides and the central pyridine of 1. The two pendant pyridines in 2 are both protonated, and hydrogen bonds are formed to the coordinated chloride positioned in the molecular cleft between these two groups. Both of the chlorides in 2 can be replaced by other anions in simple metathesis reactions, and treatment of 2 with excess SCN- or CH3CO2- yields the corresponding complexes RuX2(PPh3)(LMe2{H}2) (X: SCN-, 3; CH3CO2-, 4). Treatment of 2 with NO2- also results in displacement of the chlorides, but in this case, the protons on the pendant pyridines are lost and the nitrosyl-containing complex Ru(NO2)(NO)(PPh3)(LMe2) (5) is formed. Single-crystal X-ray structure determinations have been carried out for the following compounds: 1, space group C2/c, a = 13.588(6) Å, b = 11.518(2) Å, c = 12.731(3) Å, Z = 4, V = 1826.7 Å3; 2, space group P1̄, a = 10.482(5) Å, b = 11.349(8) Å, c = 15.710(4) Å, Z = 2, V = 1689(2) Å3; 5, space group P1̄, a = 12.204(2) Å, b = 13.065(3) Å, c = 14.722(6) Å, Z = 2, V = 1973.9(10) Å3.