The reactions between W
2(O
2C
tBu)
6(M
3−M) and each of Na/Hg, NaBH
4, LiHBEt
3 and LiMe in hydrocarbon/THF solutions yield W
2(O
2C
tBu)
4(M
4−M). W
2(O
2C
tBu)
6 and KO
tBu (2 equiv.) or W
2(O
...tBu)
6 react to give W
2(O
2C
tBu)
2(O
tBu)
4 (
1) by ligand redistribution. Crystal data for
1 at − 172°C:
a = 11.200(3), b = 16.331(5), c = 10.490(3)
A
̊
, α = 95.71(2), β = 111.19(1), γ = 71.82(1)°
,
Z = 2,
D
calc = 1.685 g cm
−3, space group
P
-
1
. A similar reaction involving W
2(O
2C
tBu)
6 and LiNPr
2
i (2 equiv.) yields and isomeric mixture of W
2(O
2C
tBu)
4(N
iPr
2)
2, for which one isomer,
2, has been crystallographically characterized. Crystal data for
2 at −164°C:
a = 41.858(9), b = 10.009(2), c = 41.481(9)
A
̊
, Z = 16, D
calc
= 1.608
g cm
−3
, space group
C2/
c. Compound
2 was shown to react with KO
tBu (2 equiv.) to give a 6:1:1 mixture of products from which the major product W
2(O
2C
tBu)
2(N
iPr
2)
2(O
tBu)
2 (
3) was characterized. Crystal data for
3 at −174°C:
a = 10.675(4),
b = 9.836(4), c = 35.795(14)
A
̊
, β = 96.76(2)°, Z = 4, D
calc
= 1.631
g cm
−3
, space group
P2
1/
c. The reaction between W
2(O
2C
tBu)
6 and NaCp (2 equiv.) in THF gave an orange hydrocarbon soluble crystalline compound Na
2W
4O
4Cp
2(O
2C
tBu)
6·4
tBuCOOH·toluene, (
4· solvate). Crystal data for
4·solvate at −70°C:
a = 13.065(2), b = 14.941(2), c = 12.996(2)
A
̊
, β = 114.90(1), γ = 71.69(1)°, Z = 1
,
D
calc = 1.67(2) g cm
−3, space group
P
-
1
. In compounds
1, 2 and
3 there are Wz.3usco;;W bonds and each metal atom is coordinated to four ligand atoms. The Mz.3usco;M bond is spanned by a pair of
cis-ppivalate ligands. The structure of the W
4O
4Cp
2(O
2C
t Bu)
6
2− anion is a centrosymmetric bis-oxo bridged dimer
η
5-C
5H
5)(
η
1-O
2C
tBu)
2W (
μ-
η
1,
η
1-O
2C
tBu)W (=O)(
μ-O)
2 with a WW bonding distance of 2.537(1) Å.
The hydrolytic condensation of organotrichlorosilanes produces polycyclic oligomers known as polyhedral oligosilasesquioxanes (POSS). Our research efforts have focussed on the chemistry of ...incompletely-condensed POSS such as the trisilanol (c-C$\sb6$H$\sb{11})\sb7$Si$\sb7$O($\sb{2/2})\sb9$(OH)$\sb3$; molecules with sufficient degree of oligomerization as to be relevant models for highly siliceous oxide frameworks, but which retain reactive Si-OH functionality that allows for their exploitation as ligands in a variety of main-group and transition-metal complexes. The widespread importance of heterogeneous silica-supported transition-metal catalysts, and the potential of incompletely-condensed POSS as ligands in solution state models for these catalysts, has made it desirable to understand the chemistry of these interesting molecules; both the synthetic transformations and manipulations possible, as well as the bonding capabilities of these large frameworks. The readily apparent similarity of POSS and their complexes to the secondary building units (SBU's) which formally comprise a variety of three dimensional polysilicates such as Linde 4A molecular sieve and other zeolites is another important aspect of this research. The initial phase of this project involved the synthesis of main group complexes of the trisilanol (c-C$\sb6$H$\sb{11})\sb7$Si$\sb7$(O$\sb{2/2})\sb9$(OH)$\sb3$ and its derivatives. Complexes of P, As, Sb, Bi, B, Al, Ga, In, and Tl were successfully synthesized and characterized. The chemical diversity within group 15 alone required the development of several synthetic strategies in order to "cap" the trisilanol with those elements. The resulting pnictide complexes were all monomeric, and one member of the series, the phosphite (c-C$\sb6$H$\sb{11})\sb7$Si$\sb7$(O$\sb{2/2})\sb9$(O$\sb3$P), is a potentially useful ligand in organometallic chemistry. The chemistry of group 13 was much more interesting, owing to the Lewis acidity of these elements. A number of interesting dimeric species were prepared and structurally characterized, demonstrating the unique flexibility of silasesquioxane ligands in accommodating the peculiar demands of various substrates. The chemical implications of this work are discussed at length. Finally, the tetramethylstibonium derivatives of several incompletely-condensed POSS were prepared. These molecules show great promise as reagents in metathetical reactions with metal halide complexes. This reactivity was exploited in the preparation of several metallated derivatives of polyhedral oligosilasesquioxanes (POMSS). The uses and limitations of these reagents are discussed.
