The complex [7,10-
![](/im<font color=)
ages/entities/mgr.gif">-H-7-CO-7,7-(PPh
3)
2-
isonido-7,8,9-ReC
2B
7H
9] h
as been synthesized by tre
atment of the complexs
alt [NHMe
3][3,3-Cl
2-3,3-(CO)
2-
closo-3,1,2-ReC
2B
9H
11] with PPh
3 in refluxing THF (tetr
ahydrofur
an)
and isol
ated
asintensely colored or
ange-red microcryst
als. Spectroscopic NMR
and IR d
at
a h
ave suggested th
at the product h
as
a highly
asymmetric structure with two inequiv
alent PPh
3 lig
ands
and
a single CO lig
and. Me
asurement of
11BNMR spectr
a in p
articul
ar h
ave indic
ated seven distinct boron vertexes,
although the resulting c
age degr
ad
ation byremov
al of two BH vertexes w
as confirmed only following X-r
ay cryst
allogr
aphic
an
alysis, which reve
aled thepent
adec
ahedr
al
isonido-7,8,9-ReC
2B
7 architecture. The
11B NMR reson
ances sp
an
an enormous chemic
al shiftr
ange (
![](/im<font color=)
ages/gifch
ars/Delt
a.gif" BORDER=0 >
![](/im<font color=)
ages/gifch
ars/delt
a.gif" BORDER=0 > = 113),
and this
appe
ars to be
a direct consequence of the deshielding of the boron vertex directlyopposite the qu
adril
ater
al
a10001">ReCCB aperture. The new complex h
as been shown by electrochemic
al me
asurementsto undergo
a reversible one-electron oxid
ation. Digit
ally simul
ated cyclic volt
ammogr
ams support
a proposed squ
arescheme (
E1/2 = 0.58, 0.69 V vs ferrocene) involving
a reversible
isonido-closo tr
ansition of the met
all
ac
arbor
anec
age. Most unusu
ally for
a met
all
ac
arbor
ane complex,
ambient temper
ature solutions in CH
2Cl
2 and DMF h
avebeen shown to be intensely turquoise-blue fluorescent (
![](/im<font color=)
ages/gifch
ars/l
ambd
a.gif" BORDER=0 >
em = 442 nm,
![](/im<font color=)
ages/gifch
ars/Phi.gif" BORDER=0 > = 0.012). Fluorescence spectroscopyme
asurements in MeTHF (2-methyltetr
ahydrofur
an) gl
ass
at 77 K h
ave indic
ated th
at the likely c
ause of such
abro
ad emission is du
al fluorescence (
![](/im<font color=)
ages/gifch
ars/l
ambd
a.gif" BORDER=0 >
em = 404, 505 nm), with both emissions displ
aying vibronic structure. Followingexcited-st
ate lifetime dec
ay
an
alysis, the emissive beh
avior h
as been
accredited to met
al-perturbed
1IL st
ates, withthe lower energy emission
arising from
a slight geometric distortion of the initi
ally excited complex.