Two diphenylformamidinate compounds of the quadruply-bonded Re26+ core

Article abstract of DOI:10.1016/S0020-1693(98)00325-9

The compounds Re₂(DPhF)₃Cl₃ and Re₂(DPhF)₂Cl₄ have been prepared and structurally characterized (DPhF = anion of N,N-diphenylformamidine). The former has three bridging DPhF ligands, two equatorial Cl ligands and one axial Cl ligand. The Re-Re distances in two different crystallographic forms are 2.2318(8) A and 2.2288(9) A. The second compound has two trans DPhF ligands and the Re₂Cl₄ unit is planar with Re-Re = 2.177(1) A, Re-Cl(av) = 2.319(5) A, Re-N(av) = 2.06(1) A and Cl-Re-Cl(av) = 106.0(1)°.

Full text of DOI:10.1016/S0020-1693(98)00325-9

Inorganica Chimica Acta 285 (1999) 149±151
Note
Two diphenylformamidinate compounds of the
6‡
quadruply-bonded Re2 core
F. Albert Cotton*, Lee M. Daniels, Steven C. Haefner
Department of Chemistry, Laboratory of Molecular Structure and Bonding, Texas A&M University, P.O. Box 300012,
College Station, TX 77842-3012, USA
Received 22 July 1998; accepted 6 August 1998
Abstract
The compounds Re2(DPhF)3Cl3 and Re2(DPhF)2Cl4 have been prepared and structurally characterized (DPhF ˆ anion of N,N-
diphenylformamidine). The former has three bridging DPhF ligands, two equatorial Cl ligands and one axial Cl ligand. The Re±Re
Ê
distances in two different crystallographic forms are 2.2318(8) A and 2.2288(9) A. The second compound has two trans DPhF ligands and
Ê
Ê
Ê
Ê
the Re2Cl4 unit is planar with Re±Re ˆ 2.177(1) A, Re±Cl(av) ˆ 2.319(5) A, Re±N(av) ˆ 2.06(1) A and Cl±Re±Cl(av) ˆ 106.0(1)8. #
1999 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Rhenium complexes; Quadruply-bonded complexes; Diphenylformadinate complexes; Dinuclear complexes
1. Introduction
re¯uxed for 24 h producing an orange precipitate. The
reaction was cooled and ®ltered in air. The orange solid
was washed repeatedly with hot hexanes (5 Â 20 ml). The
product was recrystallized by dissolution in methylene
chloride followed by slow addition of diethyl ether. The
resulting solid was collected by ®ltration, washed with
diethyl ether (4 Â 20 ml) and dried under vacuum; yield
0.32 g (69%). IR (Nujol, cm 1): 1703(s), 1700(s), 1591(m),
1531(m), 1516(s), 1487(s), 1355(m), 1342(m), 1321(s),
1212(s), 1078(w), 1027(m), 937(m), 850(w), 780(w),
757(m), 695(m), 502(w), and 415(w). Electronic absorption
spectrum (ꢀmax, CH2Cl2, nm): 510. C.V. (200 mV s 1, CH2-
In recent years, work in this laboratory has shown that the
diarylformamidinate ions, PhNC(H)NPh (DPhF) and (p-
tol)NC(H)N(p-tol) (DtolF), have great utility for the sta-
bilization of M2 cores [1] . Most commonly the com-
pounds are of the type M2(DArF)4 or M2(DArF)4X2 but
n‡
other compounds occur. We report here two such cases
6‡
obtained with Re2
.
2. Experimental
Cl2, tetrabutylammonium hexa¯uorophosphate): E1/2,red
ˆ
The starting materials, Re2Cl5(PMePh2)3 [2] and
Re2Cl4(PEt3)4 [3] were prepared by literature methods.
Diphenylformamidine (HDPhF) was purchased from
Aldrich. Solvents were freshly distilled under N2 from
suitable drying agents. All operations were carried out under
argon in standard Schlenkware.
0.97 V versus Ag/AgCl (ÁE ˆ 102 mV). This compound
may also be prepared from Re2Cl4(PEt3)4 using excess
formamidine under similar conditions.
The crystals obtained as above were solvent-free. When
20 mg of Re2(DPhF)3Cl3 was dissolved in 5 cm3 of hot
acetonitrile in an open vial and this solution was set aside to
cool and partially evaporate, a crop of orange crystals of
composition Re2(DPhF)3Cl3Á2CH3CN was obtained.
2.1. Preparation of Re2(DPhF)3Cl3
A suspension of Re2Cl5(PMePh2)3 (0.50 g, 0.43 mmol)
and HDPhF (0.34 g, 1.7 mmol) in 10 ml of toluene was
2.2. Preparation of trans-Re2Cl4(DPhF)2
A solution of Re2(DPhF)3Cl3 (0.025 g, 0.002 mmol) in
1 ml of CH3CN and 3 ml CH2Cl2 was treated with 0.2 ml of
85% HBF4ÁEt2O. The resulting red solution was layered
*Corresponding author. Tel.: +1-409-845-4432; fax: +1-409-845-9351.
0020-1693/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00325-9

150
F.A. Cotton et al. / Inorganica Chimica Acta 285 (1999) 149±151
Table 2
with diethyl ether to produce a small crop of dark red
crystals. The yield was not established.
Ê
Selected bond lengths (A) and angles (8) for Re2(DPhF)3Cl3
Re(1)±N(1)
Re(1)±N(3)
Re(1)±N(5)
Re(1)±Re(2)
Re(1)±Cl(1)
Re(1)±Cl(3)
Re(2)±N(4)
Re(2)±N(6)
Re(2)±N(2)
Re(2)±Cl(2)
N(1)±C(1)
2.103(7)
2.105(6)
2.121(6)
2.2318(8)
2.368(2)
2.446(2)
2.035(6)
2.052(7)
2.066(7)
2.357(2)
1.34(1)
N(1)±C(2)
N(2)±C(1)
N(2)±C(8)
N(3)±C(14)
N(3)±C(15)
N(4)±C(14)
N(4)±C(21)
N(5)±C(27)
N(5)±C(28)
N(6)±C(27)
N(6)±C(34)
1.44(1)
1.32(1)
1.43(1)
1.30(1)
1.47(1)
1.33(1)
1.44(1)
1.30(1)
1.46(1)
1.34(1)
1.44(1)
2.3. X-ray crystallography
Methods and instruments regularly used in this laboratory
and previously described [4] were employed. Because the
crystals of Re2(DPhF)3Cl3Á2CH3CN and Re2(DPhF)2Cl4
were very thin plates, the quality of the data obtained
was relatively poor, the structures are not of high quality,
and they will not be reported in detail.
N(1)±Re(1)±N(3)
N(1)±Re(1)±N(5)
N(3)±Re(1)±N(5)
N(1)±Re(1)±Re(2)
N(3)±Re(1)±Re(2)
N(5)±Re(1)±Re(2)
N(1)±Re(1)±Cl(1)
N(3)±Re(1)±Cl(1)
N(5)±Re(1)±Cl(1)
Re(2)±Re(1)±Cl(1)
N(1)±Re(1)±Cl(3)
N(3)±Re(1)±Cl(3)
N(5)±Re(1)±Cl(3)
Re(2)±Re(1)±Cl(3)
90.8(3)
173.8(3)
94.6(3)
89.6(2)
88.0(2)
87.7(2)
86.3(2)
168.8(2)
89.0(2)
102.69(5)
94.5(2)
83.9(2)
89.0(2)
170.97(5)
Cl(1)±Re(1)±Cl(3)
N(4)±Re(2)±N(6)
N(4)±Re(2)±N(2)
N(6)±Re(2)±N(2)
N(4)±Re(2)±Re(1)
N(6)±Re(2)±Re(1)
N(2)±Re(2)±Re(1)
N(4)±Re(2)±Cl(2)
N(6)±Re(2)±Cl(2)
N(2)±Re(2)±Cl(2)
85.63(7)
87.8(3)
91.1(3)
172.6(3)
93.3(2)
94.5(2)
92.9(2)
160.3(2)
90.1(2)
88.4(2)
3. Results and discussion
The compound Re2(DPhF)3Cl3 is the third example of
this sort of stoichiometry and structure, the previous ones
being Re2(O2CCMe3)3Cl3 [5] and Re2(O2CC2H5)(mhp)2Cl3
[6]. We have prepared it from two different starting materi-
als and determined its structure in two crystalline forms.
One of these, containing no solvent of crystallization, gave a
good quality structure. The crystallographic parameters are
summarized in Table 1 and selected metric parameters of
the molecule are collected in Table 2. A labeled drawing is
Re(1)±Re(2)±Cl(2) 106.38(5)
N(2)±C(1)±N(1)
N(3)±C(14)±N(4)
N(5)±C(27)±N(6)
122.7(7)
121.5(8)
121.8(8)
Table 1
Crystal data and structure refinement for Re2(DPhF)3Cl3, Re2(DPhF)3Cl3Á2CH3CN and Re2(DPhF)2Cl4
Re2(DPhF)3Cl3
Re2(DPhF)3Cl3Á2CH3CN
Re2(DPhF)2Cl4
Formula
Formula weight
Space group
C39H33Cl3N6Re2
1064.46
C43H39Cl3N8Re2
1146.57
C26H22Cl4N4Re2
904.68
P21/n
P21/c
P1
Ê
a (A)
Ê
b (A)
Ê
c (A)
11.060(2)
15.305(3)
9.256(3)
9.646(2)
15.352(3)
91.29(1)
105.13(1)
90.92(1)
1322.5(6)
2
13.622(1)
24.722(8)
10.093(2)
28.106(6)
ꢁ (8)
ꢂ (8)
ꢃ (8)
90
90
99.09(1)
102.81(3)
90
3678(1)
90
4234(2)
Ê 3
V (A )
Z
4
4
3
dcalc (g cm )
Crystal size (mm)
1.922
0.10 Â 0.05 Â 0.03
1.799
0.40 Â 0.10 Â 0.05 mm
2.272
0.50 Â 0.35 Â 0.10
9.573
1
m (Mo Ka) (mm
)
6.832
5.944
Data collection instrument
Radiation (monochromated in incident beam)
Orientation reflections, number, range (2ꢄ)
Temperature (K)
Nonius FAST
Nonius FAST
Nonius CAD4
Mo Ka
250, 9.1±20.8
Mo Ka
250, 8±20
Mo Ka
25, 20±23.5
123(2)
183(2)
213(2)
Scan method
!
2.16±25.00
6471
!
1.78± 22.50
5414
!-2ꢄ
2.11± 23.98
3824
Data collected range, ꢄ (8)
No. of unique data, total:
No. of parameters refined
Transition factors, max., min.
Final R indices (I > 2ꢅ(I)]a,b
R indices (all data)
Quality-of-fit indicatorc
Weight parameters, a, bb
Largest shift/esd, final cycle
451
300
325
0.818, 0.576
R1 ˆ 0.041, wR2 ˆ 0.098
R1 ˆ 0.053, wR2 ˆ 0.109
1.155
0.750, 0.460
R1 ˆ 0.066, wR2 ˆ 0.140
R1 ˆ 0.099, wR2 ˆ 0.154
1.058
0.8039, 0.3528
R1 ˆ 0.056, wR2 ˆ 0.146
R1 ˆ 0.066, wR2 ˆ 0.154
1.189
0.04, 40.0
0.003
0.055, 125.0
0.001
0.11, 0.0
0.002
3
Ê
Largest peak, (e A
)
3.2(2)
3.1(3)
4.4(5)
P
P
aR1 ˆ ||Fo| |Fc||/ |Fo|.
P
P
2
2
bwR2 ˆ [ w(Fo
Fc2)2/ w(Fo2)2]1/2, w ˆ 1/[ꢅ2(Fo2) ‡ (aÁp)2 ‡ bÁp, p ˆ [max(Fo or 0) ‡ 2(Fc2)]/3.
2
cQuality-of-fit ˆ [Æw(|Fo
|
|Fo2|)2/(Nobs Nparam.)]1/2
.

F.A. Cotton et al. / Inorganica Chimica Acta 285 (1999) 149±151
151
Ê
Me3)3Cl3, 2.229(2) A, and similar to that in Re2(O2CC2H5)-
Ê
(mph)2Cl3, 2.2041(6) A.
The third crystal structure determined in this work is that
of trans-Re2(DPhF)2Cl4. This is a type of structure fre-
quently seen in this area of chemistry. In this case the unit
cell contains two independent centrosymmetric molecules,
shown in Fig. 2. The bond distances and angles are normal
and the average values of the principal ones are given in the
caption to the ®gure.
The previously reported rhenium compounds of the
DArF type of ligand and several with DTolF , are all of
the paddlewheel type with a Re2(DTolF)4 core [7]. For three
6‡
with an Re2 unit and Cl or OMe axial ligands the Re±Re
Ê
distances are in the range 2.271±2.305 A.
Fig. 1. The Re2(DPhF)3Cl3 molecules, with thermal displacement
ellipsoids at the 30% probability level. The numbering scheme is the
one used in Table 2.
4. Supplementary material
Tables of atomic coordinates and additional data for all
the three structures are available from the corresponding
author on request.
Acknowledgements
We thank the National Science Foundation for support of
this work.
References
Fig. 2. The two independent Re2(DPhF)2Cl4 molecules. The principal
dimensions, averaged over both and over chemically equivalent ones are:
Ê
Ê
Ê
[1] F.A. Cotton, R.A. Walton, Multiple Bonds between Metal Atoms,
2nd edn., Oxford University Press, 1993.
Re±Re ˆ 2.177(1)A , Re±N ˆ 2.06(1)A, Re±Cl ˆ 2.319(5)A, Cl±Re±
Cl ˆ 106.0(1)8.
[2] K.R. Dunbar, R.A. Walton, Inorg. Chem. 24 (1985) 5.
[3] C.A. Hertzer, R.A. Walton, Inorg. Chim. Acta 22 (1977) L10.
[4] L. Chen, F.A. Cotton, Inorg. Chim. Acta 267 (1998) 271.
[5] F.A. Cotton, L.D. Gage, C.E. Rice, Inorg. Chem. 18 (1979) 1138.
[6] A.R. Cutler, S.M.V. Esjornson, P.E. Fanwick, R.A. Walton, Inorg.
Chem. 27 (1988) 287.
Ê
given in Fig. 1. The Re±Re distance found is 2.2318(8) A
while that in the less satisfactory structure of the acetonitrile
Ê
solvate is the same within experimental error, 2.2288(9) A.
Ê
The mean, 2.230 A, is the same as that in Re2(O2CC-
[7] F.A. Cotton, T. Ren, J. Am. Chem. Soc. 114 (1992) 2495.