Dinuclear Pd(I)−Pd(I) and Pt(II)···Pt(II) Complexes Supported by Tridentate Pyphos Ligands (Pyphos = 6-(Diphenylphosphino)-2-pyridonate)

Two dinuclear complexes of palladium(I) and
platinum(II) have been prepared by using a tridentate ligand
containing
three kinds of coordination sites, i.e. oxygen, nitrogen,
and phosphorus atoms. Treatment of palladium(II)
acetate
with a mixture of 6-(diphenylphosphino)-2-pyridone (abbreviated as
PyphosH) and sodium methoxide in diglyme
produced a dimeric palladium(I) complex containing a metal−metal
bond,
Pd2(pyphos)2(pyphosH)2
(1), in 43%
yield. The dinuclear complex 1 has a Pd−Pd single
bond [2.623(1) Å] surrounded by two pyphos ligands
and
two pyphosH ligands, where the pyphos ligand connected to pyphosH
through an intramolecular hydrogen bond
[1:  monoclinic, space group C2/c
with a = 19.794(7) Å, b =
14.753(7) Å, c = 25.626(5) Å, β =
107.65(2)°, V
= 7131(4) Å3, Z = 4, and R
= 0.058 for 4760 reflections with I >
3σ(I) and 451 parameters]. In the case
of
platinum, a dinuclear platinum(II) complex,
Pt2(pyphos)4 (3), was prepared
in 84% yield by treatment of PtCl2(pyphosH)2 (2) with 2 equiv of sodium methoxide
in ethanol. The dimeric structure of 3 was confirmed
by
X-ray analysis. The interatomic distance between the two platinum
atoms of 3 is 4.3615(6) Å. Thus,
complex
3 does not contain any metal−metal bond [3: 
monoclinic, space group C2/c with a
= 19.646(2) Å, b = 11.411(4) Å, c = 30.368(3) Å, β = 109.782(8)°,
V = 6406(1) Å3, Z = 4,
R = 0.046 for 5844 reflections with I >
3σ(I)
and 425 parameters].