HETERONUCLEAR COMPLEXES DERIVED FROM TRANS-A(2)PTL(2)(A=NH3 OR CH3NH2, L=2-PYRIDONATE) - DISTORTED COORDINATION GEOMETRIES OF ALL 3 METALS IN TRANS-[A(2)PTL(2)CUL(2)PT(A(2))](2-BOND IN TRANS-[A(2)PTL(LH)](+)()AND AN EXTRAORDINARY SHORT HYDROGEN)
A. Schreiber et al., HETERONUCLEAR COMPLEXES DERIVED FROM TRANS-A(2)PTL(2)(A=NH3 OR CH3NH2, L=2-PYRIDONATE) - DISTORTED COORDINATION GEOMETRIES OF ALL 3 METALS IN TRANS-[A(2)PTL(2)CUL(2)PT(A(2))](2-BOND IN TRANS-[A(2)PTL(LH)](+)()AND AN EXTRAORDINARY SHORT HYDROGEN), Inorganic chemistry, 33(26), 1994, pp. 6101-6110
tran-[a(2)PtL(LH)]NO3.xH(2)O (a = NH3, L = 2-pyridonate, C5H4NO, LH =
2-hydroxypyridine, C5H5NO, x = 2 (1); a = CH3NH2, x = 0 (2)) have been
prepared, and Cu-II adducts of composition trans-[a(2)PtL(2)CuL(2)Pta
(2)] (NO3)(2) (a = NH3, (3); a CH3NH2 (4)) have been isolated. X-ray s
tructures of 2, 3, and 4 are reported. Crystal data are as follows: 2,
orthorombic system, space group Pccn, a = 8.486(1) Angstrom, b = 13.2
00(3) Angstrom, c = 13.920(1) Angstrom, Z = 4: 3, orthorombic, space g
roup Fdd2, a = 23.281(4) Angstrom, b = 22.551(4) Angstrom, c = 10.852(
2) Angstrom, Z = 8; 4, monoclinic system, space group P2(1)/a, a = 11.
448(4) Angstrom, b = 18.771(2) Angstrom, c = 16.085(3) Angstrom, beta
= 105.81(2), Z = 4. The cation of 2, in which the two heterocyclic lig
ands bind to Pt via N(1) positions and adopt a coplanar head-tail arra
ngement, is structurally not unusual. In the crystal, cations of 2 are
associated by very short intermolecular H bonds of 2.443(9) Angstrom
into infinite chains. Since the acidic proton of this H bond was not l
ocated, a differentiation between a symmetric single minimum H bond an
d a double minimum situation (with H disordered) Was not possible, but
IR spectroscopy (no deuterium shift of nu(OH) at ca. 750 cm(-1)) favo
rs the latter. The Cu-II ions in 3 and 4 are coordinated via 0(2) oxyg
ens of the four 2-pyridonato ligands. Geometries and several spectrosc
opic properties of 3 and 4 differ markedly from the corresponding comp
lexes of composition cis-[a(2)-Pt(L')(2)Cu(L')(2)Pta(2)](2+) (L' = bri
dging pyrimidine nucleobase; coordination of Pt via endocyclic ring N,
of Cu via exocyclic O) in the following ways: Coordination spheres of
both Pt-II and Cu-II, which are essentially square planar in the cis-
compounds, have undergone considerable distortions in 3, and 4. Pt-Cu
distances in 3 (2.6312-(4) Angstrom) and 4 (2.6320(8) and 2.6450(8) An
gstrom) are significantly shorter. The trans-compounds 3 and 4 are of
orange-red colors and exhibit d-d transitions at considerably lower en
ergy than the cis-compounds which are greenish. EPR spectra (g values,
A values) are also different and the powder spectrum of 3 is unusual,
being a superposition of signals due to the molecular g-tensor, and w
eak peaks due to an exchange-narrowed g-tensor.