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

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.