Palladium nitrosyl carboxylate complexes X-ray structures of Pd 4(μ-NO)2(μ-OCOCMe3)6

Abstract Two types of palladium nitrosyl carboxylate complexes were synthesized and their structures were characterized by several methods including an X-ray diffraction analysis. The tetranuclear complexes Pd4(μ-NO)2(OCOR)6 (R=CMe3, Me, Ph, CHMe2, CH2Cl, IIa–e, respectively) were synthesized by the reaction of Pd(NO)Cl with silver carboxylates Ag(OCOR). The structure of IIa was determined by a single crystal X-ray diffractometry. Crystals of IIa are monoclinic, space group P21/n, a=12.104(7), b=23.970(8), c=15.495(4) A, β=90.30(4)°, V=4496(4) A3. The least-square structure refinement on F2 was converged to R=0.0714 for 6228 reflections [I>2σ(I)]. In IIa the palladium atoms form near regular rectangle Pd4, with the edges bridged by the ligands. Two bridging NO groups occupying the opposite sides of the rectangle are in the cis-positions with respect to the Pd4 plane. These groups are symmetric, with the PdNO angles ranging from 120.4(5) to 121.8(5)°. The coordination polyhedrons of the Pd atoms are close to square planar ones. The reaction of the Pd4(CO)4(OCOCF3)4 clusters with nitrogen monoxide leads to a substitution of the carbonyl groups and formation of the low stable complex Pd4(NO)4(OCOCF3)4 (III) that was characterized by the spectroscopic and analytical data. The transformation of III during slow recrystallization from toluene gives Pd3(NO)2(OCOCF3)4·2C6H5Me (IV) and palladium black. The structure of IV was determined by an X-ray diffraction analysis. Crystals of IV are monoclinic, space group P21/n, a=9.2340(2), b=9.2859(2), c=18.0460(4) A, β=92.339(1)°, V=1546.08(6) A3. The least-square refinement on F2 was converged to R=0.0205 for 3209 reflections [I>2σ(I)]. In the linear tri-nuclear molecule of IV, any adjacent metal atoms are linked with a couple of the CF3CO2 ligands and are separated by 3.0755(2) A. Additionally, the terminal Pd atoms bear the NO and the η2-toluene ligands. The configuration of the N atoms corresponds to the ideal sp2-hybridization. The PdNO angle is 117.2(2)°. The N atoms form short contacts with the aromatic rings. The distance between the center of the ring and the nitrogen atom is 2.70 A. Complex IV is the first example of the Pd complex with the terminal nitrosyl ligand. The scheme of transformation of complex III to complex IV was proposed.