While, i
n ge
neral, decamethylzi
ncoce
ne, Z
n(C
5Me
5)
2, a
nd other zi
ncoce
nes, Z
n(C
5Me
4R)
2 (R =H, Bu
t, SiMe
3), react with dialkyl a
nd diaryl derivatives, Z
nR'
2, to give the half-sa
ndwich compou
nds (
5-C
5Me
4R)Z
nR', u
nder certai
n co
nditio
ns the reactio
ns of Z
n(C
5Me
5)
2 with Z
nEt
2 or Z
nPh
2 produceu
nexpectedly the dizi
ncoce
ne Z
n2(
5-C
5Me
5)
2 (
1) i
n low yields, most likely as a result of the coupli
ng of two(
5-C
5Me
5)Z
n
ntities/bull.gif"> radicals. A
n improved, large scale (ca
. 2 g) sy
nthesis of
1 has bee
n achieved by reductio
nof equimolar mixtures of Z
n(C
5Me
5)
2 a
nd Z
nCl
2 with KH i
n tetrahydrofura
n. The a
nalogous reductio
n ofZ
n(C
5Me
4R)
2 (R = H, SiMe
3, Bu
t) yields o
nly decompositio
n products, but the isotopically labeleddimetalloce
ne
68Z
n2(
5-C
5Me
5)
2 a
nd the related compou
nd Z
n2(
5-C
5Me
4Et)
2 (
2) have bee
n obtai
ned bythis procedure. Compou
nd
2 has lower thermal stability tha
n 1, but it has bee
n u
nequivocally characterizedby low-temperature X-ray diffractio
n studies. As for
1 a combi
natio
n of structural characterizatio
n tech
niqueshas provided u
nambiguous evide
nce for its formulatio
n as the Z
n-Z
n bo
nded dimer Z
n2(
5-C
5Me
4Et)
2,with a short Z
n-Z
n bo
nd of 2.295(3) &Ari
ng; i
ndicative of a stro
ng Z
n-Z
n bo
ndi
ng i
nteractio
n. The electro
nicstructure a
nd the bo
ndi
ng properties of
1 a
nd those of related dizi
ncoce
nes Z
n2(
5-Cp')
2 have bee
n studiedby DFT methods (B3LYP level), with computed bo
nd dista
nces a
nd a
ngles for dizi
ncoce
ne
1 very similarto the experime
ntal values. The Z
n-Z
n bo
nd is stro
ng (ca
. 62 kcal·mol
-1 for
1) a
nd resides i
n the HOMO-4, that has a co
ntributio
n of Z
n orbitals close to 60%, co
nsisti
ng mostly of the Z
n 4s orbitals (more tha
n96%).