Synthesis of Mo(V) dimers of the form [Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)(µ-O
2
CR)] (R =
C
6
H
5
, (o-OH)C
6
H
4
, (p-Cl)C
6
H
4
, (2,4-(OH)
2
C
6
H
3
), (o-I)C
6
H
4
). The tetramer
[Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)(µ-O
2
C)C
6
H
4
(p-µ-O
2
C)Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)] was obtained in the case of (p-COOH)C
6
H
4
(COOH). The crystal and molecular structures of [Mo
2
O
2
(acac)
2
(

-O)(

-OC
2
H
5
)(

-OOCC
6
H
5
)] and [Mo
2
O
2
(acac)
2
(

-O)(

-
OC
2
H
5
)(

-OOCC
6
H
4
(o-OH))] are detailed.
Soumya Sreehari, Rudy L. Luck*
Contribution from
Department of Chemistry, Michigan Technological University, 1400, Townsend Drive,
Houghton, MI 49931
Supplementary material
Table S1 Elemental analyses of complexes 1 to 6
Figure S1
1
H NMR spectrum of 2
Figure S2
1
H NMR spectrum of 3
Figure S3 1 H NMR spectrum of 4
Figure S4
1
H NMR spectrum of 5

Figure S1 1 H NMR spectrum of 2 , recorded in CDCl
3
Figure S2
1
H NMR spectrum of 3 , recorded in CDCl
3

Figure S3
1
H NMR spectrum of 4 , recorded in CDCl
3

Figure S4
1
H NMR spectrum of 5 , recorded in CDCl
3
Experimental details:
Preparation of [Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)(µ-O
2
CC
6
H
4
( o -OH))](2)
0.327 g (1.0 mmol) of MoO
2
(acac)
2
and 0.140 g (1.0 mmol) of ortho hydroxybenzoic acid were mixed with 7.0 ml of ethanol in a thick walled glass tube fitted with a Teflon cap.
The sealed tube was heated in an oil bath to 120 ºC for 20 hours resulting in a dark brown solution. The setup was cooled overnight; the solution filtered, concentrated and refrigerated.
48 hours later, complex 2 was obtained as a orange brown crystalline solid (0.063 g, 20% yield) after filtration. IR neat (cm
-1
): 3099 (br, OH), 1584, 1460, 1378, 1221, 972 (m,
Mo=O), 955 (m, Mo=O), 849, 704, 674.
1
H NMR (CDCl
3
, 400 MHz, 25 ºC) δ (ppm): 9.93 (s,
1H) 6.59 – 7.21 (m, 4H), 6.06 (s, 2H), 4.92 (q, J = 6.8 Hz, 2H), 2.38 (s, 6H), 2.36 (s, 6H),
1.73, (t, J = 14 Hz 3H). Elemental analyses for Mo
2
O
11
C
19
H
24
( .
0.4SiO
2
): Calcd. - C, 35.42;
H, 3.75%. Found - C, 35.66; H, 3.69%.
Preparation of [Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)(µ-O
2
CC
6
H
4
( pCl))] (3)
0.652 g (1.9 mmol) of MoO
2
(acac)
2
and 0.313 g (1.0 mmol) of para chlorobenzoic acid were mixed with 12.0 ml of ethanol in a thick walled glass tube fitted with a Teflon cap. The sealed tube was heated in an oil bath to 120 ºC for 20 hours resulting in a dark brown solution. The setup was cooled overnight; the reaction mixture was filtered, concentrated and refrigerated. 48 hours later, complex 3 was obtained as dark brown powder (0.099 g, 15% yield) after filtration. IR neat (cm
-1
): 1559, 1537, 1518, 1416, 1343, 1281, 1086, 1015, 962
(m, Mo=O), 948 (m, Mo=O), 847, 727, 678.
1
H NMR (CDCl
3
, 400 MHz, 25 ºC) δ (ppm):
7.08 – 7.28 (m, 4H), 6.02 (s, 2H), 4.86 (q, J = 7.2 Hz, 2H), 2.37 (s, 6H), 2.34 (s, 6H), 1.72, (t,

J = 14 Hz, 3H). Elemental analyses for Mo
2
O
10
C
19
H
24
Cl( .
1.25SiO
2
): Calcd. - C, 31.97, H,
3.25% Found - C, 31.61, H, 3.36%.
Preparation of [Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)(µ-O
2
CC
6
H
3
(2,4-(OH)
2
))](4)
0.328 g (1.0 mmol) of MoO
2
(acac)
2
and 0.155 g (1.0 mmol) of 2, 4-dihydroxybenzoic acid were mixed with 7.0 ml of ethanol in a thick walled glass tube fitted with a Teflon cap.
The sealed tube was heated in an oil bath to 120 ºC for 22 hours resulting in a dark brown solution with some solid residue. The setup was cooled overnight; the reaction mixture filtered, concentrated and refrigerated. 48 hours later, complex 4 was obtained as a dark reddish brown powder (0.050 g, 16% yield) after filtration. IR neat (cm
-1
): 3315 (br, OH),
1628, 1537, 1523, 1418, 1341, 1284, 1093, 1020, 967 (m, Mo=O), 957 (m, Mo=O), 934, 860,
739, 681.
1
H NMR (CDCl
3
, 400 MHz, 25 ºC) δ (ppm): 9.96 (s, 2H) 6.97 – 6.99 (m, 3H), 6.04
(s, 2H), 4.90 (q, J = 7.2 Hz, 2H), 2.365 (s, 6H), 2.361 (s, 6H), 1.72, (t, J = 14 Hz, 3H).
Elemental analyses for Mo
2
O
12
C
19
H
24
( .
0.75SiO
2
): Calcd. - C, 33.45; H, 3.55%. Found - C,
33.73; H, 3.88%.
Preparation of [Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
)(µ-O
2
CC
6
H
4
( oI))](5)
0.652 g (1.9 mmol) of MoO
2
(acac)
2
and 0.496 g (2.0 mmol) of ortho iodobenzoic acid were mixed with 12.0 ml of ethanol in a thick walled glass tube fitted with a Teflon cap. The sealed tube was heated in an oil bath to 120 ºC for 20 hours resulting in a dark brown solution. The setup was cooled overnight; the reaction mixture filtered, concentrated and refrigerated. 48 hours later, complex 5 was obtained as a dark brownish black powder (0.202 g, 28% yield) after filtration. IR neat (cm
-1
): 1588, 1518, 1413, 1342, 1282, 1089, 1016, 964
(m, Mo=O), 949 (m, Mo=O), 846, 736, 679. 1 H NMR (CDCl
3
, 400 MHz, 25 ºC) δ (ppm):

6.85 – 7.72 (m, 4H), 6.00 (s, 2H), 4.97 (q, J = 7.2 Hz, 2H), 2.35 (s, 6H), 2.34 (s, 6H), 1.78, (t,
J = 14 Hz, 3H). Elemental analyses for Mo
2
O
10
C
19
H
24
I( .
2.25SiO
2
): Calcd. - C, 30.90, H,
3.14%. Found - C, 30.41, H, 2.98%
Preparation of [(Mo
2
O
2
(acac)
2
(µ-O)(µ-OC
2
H
5
))
2
(µ-O
2
C)C
6
H
4
( p -µ-O
2
C))](6)
0.328 g (1.0 mmol) of MoO
2
(acac)
2
and 0.170 g (1.0 mmol) of terephthalic acid were mixed with 7.0 ml of ethanol in a thick walled glass tube fitted with a Teflon cap. The sealed tube was heated in an oil bath to 115 ºC for 14 hours resulting in a dark red solution. The setup was cooled overnight and a bright orange crystalline powder was seen at the bottom of the reaction tube. This powder was filtered and dried to obtain complex 6 (0.108 g, 38% yield). IR neat (cm -1 ): 1523, 1397, 1343, 1280, 1091, 1017, 964 (m, Mo=O), 942 (m, Mo=O),
827, 748, 679.
1
H NMR (CDCl
3
, 400 MHz, 25 ºC) δ (ppm): 7.13 (s, 4H), 5.97 (s, 4H), 4.79
(q, J = 6.8 Hz, 4H), 2.34 (s, 12H), 2.30 (s, 12H), 1.68, (t, J = 14 Hz, 6H). Elemental analyses for Mo
4
O
20
C
32
H
42
( .
C
2
H
5
OH): Calcd. - C, 34.71, H, 4.11% Found - C, 35.17, H, 3.4%