Fa. Cotton et al., PENTANUCLEAR ZIRCONIUM CLUSTERS WITH CHLORIDE, HYDRIDE, AND PHOSPHINE-LIGANDS, Journal of the American Chemical Society, 116(10), 1994, pp. 4364-4369
The synthesis and characterization of new zirconium cluster compounds
of composition H4Zr5Cl12(PR(3))(5) are reported. By reaction of ZrCl4
with 1.60 mol equiv of Bu(3)SnH followed by 1 mol equiv of PR(3), the
pentanuclear species are obtained rather than the previously described
hexanuclear ones, Zr6Cl14(PR(3))(4). The compounds with PR(3) = PMe(3
) (1), PEt(3) (2), and PMe(2)Ph (3) have been characterized by X-ray c
rystallography and by P-31{H-1} and H-1 NMR spectroscopy. Compound 1.C
6H6 crystallizes in the triclinic space group P (1) over bar with cell
dimensions (-100 degrees C) of a = 11.833(2) Angstrom, b = 12.001(1)
Angstrom, c = 20.167(2) Angstrom, alpha = 77.651(9)degrees, beta = 86.
627(9)degrees, gamma = 64.23(1)degrees, V = 2517.4(5) Angstrom(3), and
Z = 2. Compound 2 crystallizes in the monoclinic space group C2/c wit
h cell dimensions (-75 degrees C) of a = 48.06(1) Angstrom, b = 12.667
(2) Angstrom, c = 22.829(5) Angstrom, beta = 113.36(2)degrees, V = 12
758(11) Angstrom(3), and Z = 8. Compound 3 crystallizes in the triclin
ic space group P (1) over bar with cell dimensions (21 degrees C) of a
= 12.623(2) Angstrom, b = 13.715(3) Angstrom, c = 19.382(4) Angstrom,
alpha = 91.58(2)degrees, beta = 96.78(2)degrees, gamma = 116.20(1)deg
rees, V = 2878(2) Angstrom(3), and Z = 2. These diamagnetic compounds
have NMR spectra showing that they retain solution structures that are
similar to those in the crystals. Furthermore, the H-1 NMR spectra of
2 and 3 show resonances at -1.18 and -2.58 ppm, respectively, which i
ntegrate to four hydride ligands per Zr-5 cluster. In all cases, the Z
r atoms define a distorted pyramid with a rectangular base. There are
two long basal edges (3.41-3.54 Angstrom) and two short ones (3.20-3.3
1 Angstrom). The slant edges are similar in length (3.29-3.33 Angstrom
) to the short basal edges. All eight of the Zr-Zr edges are bridged b
y a mu-Cl atom. One PR(3) ligand is bonded above the apical zirconium
atom, and the others are bonded to the basal zirconium atoms, with two
opposite ones in the basal plane and the other two below it. By using
X-ray data collected at -100 degrees C, the four hydride ligands were
found in (1.C6H6), two just inside the centers of the triangular Zr-3
faces with the longer basal edges [Zr-mu(3).H = 1.96(3) Angstrom] and
two symmetrically placed below the short basal edges [Zr-mu(2).H = 1.
96(8) Angstrom]. All four of these crystallographically independent hy
drogen atoms refined well.