The reactions of the unsymmetrical, coordinatively unsaturateddirhenium(II) complexes[Re
2Br
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)(CNXyl)]Y (XylNC = 2,6-dimethylphenyl isocyanide; Y =O
3SCF
3 (
3a), PF
6(
3b)) with XylNC afford at leastthree isomeric forms of the complex cation[Re
2Br
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)(CNXyl)
2]
+.Two forms have very similarbis(
![](/images/entities/mgr.gif)
-halo)-bridged edge-sharing bioctahedral structures of thetype[(CO)BrRe(
![](/images/entities/mgr.gif)
-Br)
2(
![](/images/entities/mgr.gif)
-dppm)
2Re(CNXyl)
2]Y(Y = O
3SCF
3(
4a/4a'), PF
6(
4b/4b')), while the third is an openbioctahedron[(XylNC)
2BrRe(
![](/images/entities/mgr.gif)
-dppm)
2ReBr
2(CO)]Y(Y = O
3SCF
3 (
5a),PF
6 (
5b)). While the analogous chlorocomplex cation[Re
2Cl
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)(CNXyl)
2]
+was previously shown to exist in three isomeric forms, only one ofthese has been found to be structurally similarto the bromo complexes (i.e. the isomer analogous to
5a and
5b). The reaction of
3a with CO gives thesalt[Re
2Br
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)
2(CNXyl)]O
3SCF
3(
7), in which the edge-sharing bioctahedral cation[(XylNC)BrRe(
![](/images/entities/mgr.gif)
-Br)(
![](/images/entities/mgr.gif)
-CO)(
![](/images/entities/mgr.gif)
-dppm)
2ReBr(CO)]
+has an all-cis arrangement of
![](/images/gifchars/pi.gif)
-acceptor ligands. The Re-Redistances in thestructures of
4b',
5a, and
7 are 3.0456(8), 2.3792(7), and 2.5853(13)Å, respectively, and accord with formalRe-Re bond orders of 1, 3, and 2, respectively. Crystal data for[Re
2Br
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)(CNXyl)
2](PF
6)
0.78(ReO
4)
0.22·CH
2Cl
2(
4b') at 295 K: monoclinic space group
P2
1/
n (No. 14) with
a =19.845(4) Å,
b =16.945(5) Å,
c = 21.759(3) Å,
![](/images/gifchars/beta2.gif)
=105.856(13)
![](/images/entities/deg.gif)
,
V = 7038(5) Å
3, and
Z = 4. The structure was refined to
R= 0.060 (
Rw = 0.145) for 14 245 data(
Fo2 >2
![](/images/gifchars/sigma.gif)
(
Fo2)). Crystal data for[Re
2Br
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)(CNXyl)
2]O
3SCF
3·C
6H
6 (
5a) at 173K: monoclinic space group
P2
1/
n(No. 14) with
a = 14.785(3) Å,
b =15.289(4) Å,
c =32.067(5) Å,
![](/images/gifchars/beta2.gif)
= 100.87(2)
![](/images/entities/deg.gif)
,
V=7118(5) Å
3, and
Z = 4. Thestructure was refined to
R = 0.046(
Rw = 0.055)for 6962 data (
I > 3.0
![](/images/gifchars/sigma.gif)
(
I)). Crystaldata for[Re
2Br
3(
![](/images/entities/mgr.gif)
-dppm)
2(CO)
2(CNXyl)]O
3SCF
3·Me
2CHC(O)Me(
7) at295 K: monoclinic space group
P2
1/
n(No. 14) with
a = 14.951(2) Å,
b =12.4180(19) Å,
c = 40.600(5) Å,
![](/images/gifchars/beta2.gif)
= 89.993(11)
![](/images/entities/deg.gif)
,
V = 7537(3) Å
3,and
Z = 4. The structure was refined to
R= 0.074 (
Rw = 0.088) for
6595data(
I > 3.0
![](/images/gifchars/sigma.gif)
(
I)).