W2Cl4(NR2)2(PR‘3)2 Molecules. 4. A New Synthetic Route to Products with a Staggered Conformation. Preparations and Characterizations of W2Cl4(NR2)2(PR‘3)2 (R = Et, Bu, Hex; R‘3 = Me3, Et2H) and an Intermediate Complex W2Cl4(NEt2)2(NHEt2)2
dataset
posted on 1997-02-12, 00:00 authored by F. Albert Cotton, Evgeny V. Dikarev, N. Nawar, Wai-Yeung WongA new and convenient synthetic route to a series of W⋮W
compounds with the general formula
W2Cl4(NR2)2(PR‘3)2 has been developed. The method has
been used in the preparation of
W2Cl4(NR2)2(PMe3)2
(R = Et (2),
Bu (3), Hex (4)) and
W2Cl4(NR2)2(PEt2H)2
(R = Et (5), Bu (6), Hex (7)).
Treatment of
W2Cl6(THF)4 with
the
appropriate dialkylamine NHR2 (R = Et, Bu, Hex) affords
an intermediate species having the stoichiometry
W2Cl4(NR2)2(NHR2)2.
This has been verified by single-crystal X-ray diffraction studies
for
W2Cl4(NEt2)2(NHEt2)2
(1) with the following crystallographic parameters:
orthorhombic space group Iba2, a =
11.6704(9) Å, b =
13.336(1) Å, c = 17.321(2) Å, Z =
4. The structure of 1 reveals that the molecule itself
deviates from an
eclipsed conformation with retention of a strong intramolecular
N−H···Cl hydrogen bonding and the torsion
angle involving the hydrogen bonded N and Cl atoms is 27.0°.
Each W atom is coordinated by a cis set of two
Cl and two N atoms with a W−W distance of 2.3084(5) Å.
There is a 1.6% orientational disorder of the W−W
unit. Subsequent addition of the monodentate phosphines
(PMe3 and PEt2H) to the intermediate complexes
produces
a variety of new W26+ complexes
W2Cl4(NR2)2(PR‘3)2,
2−7, in reasonable yields, depending on the
choices of
the amines and phosphines. The characterization of
2−7 has been accomplished using IR and
1H and
31P{1H}
NMR spectroscopy and mass spectrometry. The crystal structures of
2, 3, 6, and 7 are fully
described. Crystal
data for these compounds are as follows: for 2, triclinic
space group P1̄, a = 9.568(2) Å,
b = 17.294(7) Å, c =
17.418(5) Å, α = 111.82(3)°, β =
103.11(2)°, γ = 90.72(3)°, Z = 4; for
3, P1̄, a = 12.162(6) Å,
b = 14.955(4)
Å, c = 18.82 (1) Å, α = 95.66(3)°, β =
97.99(4)°, γ = 91.26(3)°, Z = 4; for
6, monoclinic space group
P21/n,
a = 17.970(3) Å, b = 10.993(2) Å,
c = 20.689(4) Å, β = 115.43(1)°,
Z = 4; for 7,
P21/c, a =
15.3937(7) Å, b
= 11.473(2) Å, c = 24.977(3) Å, β =
92.33(1)°, Z = 4. The molecular structures of
all these phosphine-containing complexes possess a common metal core unit and each entails
an essentially staggered
W2Cl4N2P2
conformation with the W atoms united by a triple bond (average W−W
distance, 2.322 Å). Each molecule
adopts a cis configuration with the P and N atoms mutually cis on each
W atom, consistent with the stereochemistry
of the intermediate species
W2Cl4(NR2)2(NHR2)2
formed in the first step.
