Reaction of the hydride com
plexes [M
2C
p2(
![](/images/entities/mgr.gif)
-H)(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4] (M = Mo, W; C
p =
5-C
5H
5)with [FeC
p2]BF
4 proceeds in a 1:2 ratio to give the unsaturated tetracarbonyl salts [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4]BF
4, which s
pontaneously (M = Mo) or in the
presence of CO (M = W)transform into the corres
ponding electron-
precise
pentacarbonyls [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(
![](/images/entities/mgr.gif)
-CO)(CO)
4]BF
4. In contrast, reaction of the above hydride com
plexes with [FeC
p2](BAr
'4) (Ar
' =3,5-C
6H
3(CF
3)
2)
proceeds in a 1:1 ratio to give the
paramagnetic salts [M
2C
p2(
![](/images/entities/mgr.gif)
-H)(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4](BAr
'4). No further reaction takes
place with [FeC
p2](BAr
'4) unless a
proton acce
ptorsuch as water or tetrahydrofuran is
present, in which case the corres
ponding salts [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4](BAr
'4) or [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(
![](/images/entities/mgr.gif)
-CO)(CO)
4](BAr
'4) are ra
pidly formed. Reactionsof the anions [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4]
- (as (H-DBU)
+ salts, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) with [FeC
p2]BF
4 proceed ste
pwise to give first the 33-electron radicals [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4], which can be isolated as very air-sensitive green solids, and then theunsaturated salts [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4]BF
4, which are identical to those formed from theneutral hydrides. The structure and dynamic behavior of the new com
pounds are analyzedon the basis of solution IR,
1H,
31P, and
13C NMR or ESR s
pectrosco
pic data. In addition,the redox and other chemical transformations connecting all the new com
pounds arediscussed on the basis of the synthetic and structural data, as well as cyclic voltammetrymeasurements carried out in dichloromethane on the neutral hydrides [M
2C
p2(
![](/images/entities/mgr.gif)
-H)(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4] and the anions [M
2C
p2(
![](/images/entities/mgr.gif)
-PPh
2)(CO)
4]
- (as [N(PPh
3)
2]
+ salts).