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Reactivity of the complexes Mo(CO)3(η2-NN)(η1-(dppm) (NN = bpy, phen, dmp) with HgX2 (X = Cl, Br, I, CN, SCN). Formation of trimetallic MoHgMo and bimetallic MoHg complexes
Polyhedron Vol. IO, No. 22, pi. 261 l-2616. Printed in Great Britain
0277-5387/91 s3.00+.00 0 1991 Pergamon Press plc
1991
REACTIVITY OF THE COMPLEXES Mo(CO)&*-NN)(q’-dppm) (NN = bpy, phen, dmp) WITH HgX2 (X = Cl, Br, I, CN, SCN). FORMATION OF TRIMETALLIC Mo-Hg-Mo AND BIMETALLIC Mo-Hg COMPLEXES 1w. CANO* and J. A. CAMP0 Departamento de Q&mica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutense, 28040-Madrid, Spain (Received IO May 1991; accepted 28 June 1991)
Abstract-The reactions of the complexes [Mo(CO),($-NN)(q’-dppm)] [NN = 2,2’-bipyridyl (bpy), 1, lo-phenanthroline (phen), 2,9-dimethyl- 1,lo-phenanthroline (dmp) ; dppm = bis(diphenylphosphino)methane] with HgX, (X = Cl, Br, I, CN, SCN) led to three types of compounds [Mo(CO)&‘-NN)(X)J,Hg (NN = bpy, phen; X = Cl, Br, CN, SCN. NN = dmp ; X = CN), [Mo(CO)~(~*-NN)(~-dppm)HgI]HgI~ (NN = bpy, phen ; X = I) and [Mo(CO),(q2-dmp)(HgX)(X)] (X = Cl, Br, I, SCN), depending on the NN-ligand and the mercuric derivative employed. The fo~ation of the trinuclear complexes ~o(CO),(q”NN)(X)],Hg is favoured over the expected bimetallic derivatives, in which two metals are bridged by the dppm ligand. Bimetallic compounds are obtained when bulky ligands are present, such as dmp bonded to a molybdenum atom or I bonded to mercury, and only in the latter case is a Mo-Hg complex bridged by dppm obtained.
Heterobimetallic complexes containing a transition metal bonded to mercury are of current interest, especially because some of these have been used as intermediates in organic and organometallic synthesis. Complexes containing constraining ligands such as Ph2PCH2PPh2 [bis(diphenylphosphino)methane, dppm] are of special interest since proximity effects involved in bridging behaviour can be used to favour formation of the metal-metal bond. ’ However, dppm bridged systems involving molybdenum and mercury have not been described and we are interested in the study of this type of compound. On the other hand it has been established that complexes of the type [Mo(CO),(q*-dppm)(q’dppm)] [dppm = bis(diphenylphosphino)methane] in their reactions with transition metal derivatives are able to form dinuclear heterobimetallic complexes bridging two metals by the dppm ligand.*r3 However, no bimetallic derivatives were obtained from the reaction of ~o(CO)~(~~dppm)(~‘-dppm)]
with HgX2 (X = Cl, SCN) (although Mo-Hg bonded species have been suggested as intermediates) and new dicarbonyl molybdenum-complexes were formed by elimination of mercury.4 In a previous communication, we have reported the behaviour of the related [Mo(CO)3(q2-bpy)(q’dppm)] complex towards some metal derivatives. Molybdenum-metal complexes were formed in all cases, and in particular a trinuclear compound [Mo(CO)j(q2-bpy)(C1)]2Hg was obtained in the reaction with HgC12. * As an extension of the above results we have studied the reactions of [Mo(CO),(q2-NN)(q’dppm)] @N = 2,2’-bipyridyl (bpy), 1,lO-phenanthroline 2.9-dimethyl-l,lO-phen(phen), anthroline (dmp)] with HgX2 (X = Cl, Br, I, CN, SCN), in an attempt to form new heterobimetallic Mo-Hg complexes with dppm as bridge. RESULTS
AND DISCUSSION
The spectroscopic and analytical data of the isolated compounds are surnamed in Tables 1 and *Author to whom correspondence should be addressed. 2. 2611
2612
M. CAN0 Table
1. Analytical,
conductivity
and J. A. CAMP0
and IR data
for the complexes
[Mo(CO),(q2-NN)(X)],Hg,
[Mo(CO),(r12-NN)01-dppm)HgIlHgI, and [Mo(CO),(?2-dmp)(HgX)(X)1 Compound (Colour)
[Mo(CO),(?2-bpy)(C1)1,Hg
Analyses (%) C H N
A,,,* (ohm- ’ cm2 mol- ‘)
VCOC (cm- ‘)
32.9 (33.1
1.6 1.7
5.8 6.0)
13.2
1978sh 1950s 1935s 1850sh 1835~s
35.9 (36.4
1.6 1.6
5.5 5.7)
9.4
1978m 194Ovs 1888sh 1848s 1820~s
30.7 (31.0
1.6 1.9
4.0 4.2)
13.5
1978vs 1895sh 1870s
29.7 (30.1
1.3 1.6
5.2 5.4)
12.5
1975sh 1952s 1938s 1855sh 1838~s
32.8 (33.4
1.4 1.5
5.0 5.2)
10.2
1974m 1942s 1850s 1825~s
26.9 (27.3
1.3 1.6
3.5 3.7)
14.2
1978~s 1870s
27.7 (28.0
1.5 1.9
1.7 1.7)
52.0
1968~s 1872sh 1852~s
28.8 (29.0
1.6 1.8
1.8 1.7)
43.2
1965~s 1878sh 1852~s
[Mo(CWr12-dmp)(HgI)(I)l (Yellow)
24.0 (24.3
1.2 1.4
3.1 3.3)
10.3
1975s 1870s
[Mo(CO),(tt2-bPY)(NCS)I,Hg
33.9 (34.0
1.6 1.6
8.0 8.5)
17.6
1982~s 1950vs 1905sh 1882s 1840~s 2090sh(v& 2075s(v,,)
36.8 (37.1
1.5 1.6
7.8 8.1)
14.7
1975s 195ovs 1872~s 1855s 2095s(v,,) 2060sh(vc,q)
32.1 (32.4
1.5 1.7
7.6 8.0)
15.0
1978vs 1900s 1862~s 2098s(v&
(Yellow-orange)
[MWO) dv 2-pW(Cl)lJ% (Orange)
[Mo(CO)~(r12-dmp)(HgC1)(C1)1 (Orange)
[Mo(CO),(?2-bpy)(Br)l,Hg (Orange)
[Mo(CO)j(t12-phen)(Br)12Hg (Orange)
[Mo(CO)~(r12-dmp)(HgBr)(Br)l (Orange)
[Mo(CO),(?2-bpy)(~-dppm)HgIlHg13 (Yellow)
[Mo(CO)~(r12-phen)(~-dppm)HgIlHgI, (Yellow)
(Orange)
[Mo(CO)3(t12-phen)(NCS)12Hg (Orange)
[Mo(CO),(r12-dmp)(HgSCN)(SCN)1 (Orange-yellow)
2613
Reactivity of complexes Table l+ontinued Analyses (%) N C H
Compound (Colour)
[MotCO),(rt*-bpy)(CN)l,Hg (Yellow)
[Mo(CO),(?‘-phen)(CN)l,Hg (Orange-yellow)
[Mo(CO) dtl*-dw)(CN)l2Hg (Orange-yellow)
Amb(ohm- ’ cm*mol-‘)
VCOC (cm-- ‘)
36.0 (36.4
1.6 1.7
8.9 9.1)
12.5
1995s 1975vs 1898sh 1870~s 1845~s 2105w(v&
39.2 (39.6
1.5 1.7
8.4 8.7)
15.2
1988~s 1960~s 1895sh 1862~s 2105m(vc,)
41.7 (42.1
2.2 2.4
8.0 8.2)
9.5
1985s 1960s 1890~s 1870sh 2105w(v&
a Found ; (calculated). bin dimethylformamide solutions lo-’ M. ‘In KBr pellets ; vs = very strong, s = strong, m = medium, w = weak, sh = shoulder.
Table
2.
NMR
data
for
drvWWlW
[Mo(CO),(q*-NN)(y-
3
NN
6 (3’P)
*JP-P
(CH2 in dppm)
(ppm)
(Hz)
by
4.45bf
30.0br, 48.7bP 29.6d, 49.0d”
149
phen
4.2lbP
26.3br, 44.4bP
6 (‘I-9 (ppm>
“In (CD3)&0 solution at -20°C. bIn (CD,),CO solution at room temperature. br = broad ; d = doublet.
(a) Reactivity of [Mo(CO),(q*-NN)(q’-dppm)] (NN = bpy, phen) with HgX, (X = Cl, Br) The [Mo(CO),(q2-NN)(q’-dppm)] complex (NN = bpy, phen) reacts with mercury(I1) halide, HgX, (X = Cl, Br), in a 1 : 1 or 1: 2 molar ratio at room temperature and no CO evolution is observed. The solids isolated are insoluble in common solvents and they have been characterized as a mixture of [Mo(CO),(q2-NN)(X)],Hg and HgX,*ndppm. The IR spectra of the solids show in the carbonyl region the characteristic pattern of bands of [Mo(CO),(q2-bpy)(X)],Hg complexes ;5*6however, absorptions attributed to coordinated dppm ligand
are also observed, and suggest the presence of HgX, * ndppm (NN = bpy, phen ; X = Cl, Br). In order to confirm our hypothesis we studied compounds of the type HgX, * ndppm, synthesized by direct reactions between HgX, and dppm. New products, characterized as HgX, sndppm (X = Cl, n = l/3; X = Br, n = 1) were isolated and all of these were insoluble in common solvents.’ The 3’P-NMR spectra of the above compounds, registered in DMSO-d6, show a singlet (X = Cl, 6 = 2.25 ppm; X = Br, 6 = 2.00 ppm) with their corresponding mercury satellites.’ These signals appear at the same position as those observed for the solids formed in the reactions referred to above, and confirm the suggested presence of the adducts HgX, * ndppm in the products of these reactions. On this basis we thought that a 2 : 1 (MO : Hg) stoichiometry for the reaction between the molybdenum complex [Mo(CO),(q2-NN)(q’-dppm)] and HgX, could yield the trinuclear derivative exclusively. We have carried out these 2 : 1 reactions and the products isolated were characterized as the expected complexes [Mo(CO)~(~*-NN)(X)],Hg. This fact indicates that the dppm ligand is always liberated from the starting molybdenum complex and that the formation of HgX, * ndppm compounds occurs when an excess of HgX, with respect to the 2 : 1 molar ratio of the reaction is employed.
Reactivity of complexes
(d) Reactivity of [Mo(CO)3(~2-dmp)(~‘-dppm)] with HgX, (X = Cl, Br, I, CN, SCN) Related reactions between the complexes [Mo(CO),(~2-dmp)(~‘-dppm)] and HgX, (X = Cl, Br, I, CN, SCN) have been studied. In the starting molybdenum complex we have introduced dmp as the NN-ligand, which is more basic and presents more demanding steric effects than the others. compounds of the Surprisingly, type [Mo(CO)3(n2-dmp)(HgX)(X)] (X = Cl, Br, I, SCN) were isolated, and only products of double insertion of the type [M0(C0)~(q~-dmp)(CN)]~Hg were obtained in the reaction with Hg(CN),. This different behaviour could be attributed to the low stability of the Mo-Hg-CN bonds.”
2615
(Devon, U.K.). IR spectra were recorded on a Perkin-Elmer 1300 spectrophotometer with KBr pellets. The NMR spectra were recorded on a Varian XL-300 spectrometer at room temperature and -20°C operated at 299.95 MHz for ‘H and 121.42 MHz for 3’P, with (CH3)$i as internal standard for ‘H and 85% phosphoric acid as external standard for 3’P ; the solvents used were (CD3)2CO and (CD3)SO. Conductance measurements were performed in dimethylformamide solutions at room temperature.
(b) Reactions
Preparation of [Mo(CO)3(q2-NN)(X)]2Hg (NN = bpy, phen ; X = Cl, Br). 0.1 mmol of HgX, was added to a solution of [Mo(CO)~(~~-NN)(~‘CONCLUSIONS dppm)] (0.2 mmol) in dichloromethane (15 cm3). The mixture was stirred for 1 h and the precipitate forFormation of trinuclear complexes of the type med was filtered off, washed with dichloromethane [(r2-NN)(CO),00M~Hg--Mo(X)(CO)3(~2-NNll and petroleum ether (b.p. 4&6O”C) and dried in appears to be favoured by reaction between [MO vacua. (CO),(q2-NN)(L)] and HgX,; even when L is a Preparation of [Mo(CO)3(~2-NN)(X)]2Hg (NN PP-ligand coordinated in a monodentate form as = bpy, phen ; X = CN, SCN). 0.12 mm01 of q’-dppm this behaviour is not modified, and the HgX, was added to a solution of [Mo(CO)~(~~~expected bimetallic complexes in which two metals NN)(q’-dppm)] (0.24 mmol) in dichloromethane (15 are bridging by dppm ligand are not formed. cm’). The mixture was stirred for 30 min for Particular results are obtained when bulky Hg(SCN)2 and 2 h for Hg(CN)2. The solid formed ligands are present, such as in the case of dmp was filtered off, washed with petroleum ether (b.p. bonded to molybdenum or I bonded to mercury, 4060°C) and dried in vucuo. and bimetallic derivatives are formed in these Preparation of [Mo(CO)3(~2-NN)(~-dppm)HgI] cases. An intermediate species as in Fig. 2 is proHgl, (NN = bpy, phen). 0.5 mmol of HgI, was posed to explain the formation of the final cationic added to a solution of [Mo(CO),(~~-NN)(~‘compound [M0(CO),(~~-NN)(~-dpprn)Hg1]+. This dppm)] (0.25 mmol) in dichloromethane (15 cm’). fact does not occur when the NN-ligand is dmp, A colour change was observed immediately probably due to the greater electronic and steric (from violet to yellow-orange) and the formation properties of this ligand. of a yellow precipitate occurred. The mixture was stirred for 15 min, and the solid was filtered off, C washed with petroleum ether (b.p. 40-60°C) and dried in vacua. Preparation of [Mo(CO),(q2-dmp)(HgX)(X)] (X = Cl, Br, I, SCN). 0.5 mmol of HgX, was added (I+NN)(CO~MO ;----;HgI to a solution of [Mo(CO),(q2-dmp)(q ‘-dppm)] (0.25 ‘. I” mmol) in dichloromethane (10 cm3). A colour change was observed quickly (from violet to Fig. 2. orange). The compounds were obtained by precipitation with petroleum ether (b.p. 4&6O”C) after EXPERIMENTAL 5-10 min of stirring. The compound obtained with Hg(SCN)2 precipitated in the reaction medium. The (a) General solids were filtered off, washed with petroleum ether All reactions were carried out under oxygen-free (b.p. 4&60”(Z) and dried in vacua. dry nitrogen. Analytical grade solvents were used. The [Mo(CO)~(r12-NN)(r1-dppm)l Cm = by, Acknowledgement-Financial support for this work from phen, dmp) complexes were prepared as previously the Comisibn Asesora de Investigacibn Cienttica y T&described. l8 C, H and N analyses were carried out nica (CAICYT) is gratefully acknowledged (Project No. by Elemental Micro-Analysis Laboratories Ltd. 367184).
A /p ‘\
M. CAN0
2616
and J. A. CAMP0
REFERENCES 1. B. Chaudret, B. Delavaux and R. Poilblanc, Coord. Chem. Rev. 1988,86, 191. 2. E. E. Isaacs and W. A. G. Graham, Inorg. Chem. 1975,14,2560. 3. A. Blagg, P. G. Pringle and B. L. Shaw, J. Chem. Sot., Dalton Trans. 1987, 1495 and refs therein. 4. A. Blagg, A. T. Hutton and B. L. Shaw, Polyhedron 1987,6,95. 5. M. Cano, J. A. Campo, P. Ovejero and J. V. Heras, Inorg. Chim. Acta 1990, 170, 139. 6. P. Correa, M. E. Vargas and J. Granifo, Polyhedron 1987,6, 1781. 7. M. Cano and J. A. Campo, unpublished results. 8. M. P. Pardo and M. Cano, J. Organomet. Chem. 1983,247, 293. 9. M. A. Lobo, M. F. Perpiilan, M. P. Pardo and M. Cano, J. Organomet. Chem. 1983,254,325. 10. M. Panizo and M. Cano, J. Organomet. Chem. 1984, 266,247.
11. M. P. Pardo and M. Cano, J. Organomet. Chem. 1984,270,3 11. 12. A. Lopez, M. Panizo and M. Cano, J. Organomet. Chem. 1986,311,145. 13. R. D. Fischer and K. Noack, J. Organomet. Chem. 1969, 16, 125. 14. D. M. Adams, Metal-Ligand and Related Vibrations. Edward Arnold, London (1967). 15. R. Bhattacharyya, G. Prashad Bhattacharjee and A. Mohan Saha, Polyhedron 1985,4,583, and refs therein. 16. R. Bhattacharyya and G. Prashad Bhatacharjee, J. Chem. Sot., Dalton Trans. 1983, 1593. 17. M. M. Kubicki, R. Kergoat, J. E. Guerchais, C. Bois and P. L’Haridon, Inorg. Chim. Acta 1980, 43, 17. 18. M. Cano, J. A. Campo, V. Perez-Garcia, E. GutiCrrez-Puebla and C. Alvarez-Ibarra, J. Organomet. Chem. 1990,382,397. 19. T. A. George, J. Organomet. Chem. 1971,33, C13.
0277-5387/91 s3.00+.00 0 1991 Pergamon Press plc
1991
REACTIVITY OF THE COMPLEXES Mo(CO)&*-NN)(q’-dppm) (NN = bpy, phen, dmp) WITH HgX2 (X = Cl, Br, I, CN, SCN). FORMATION OF TRIMETALLIC Mo-Hg-Mo AND BIMETALLIC Mo-Hg COMPLEXES 1w. CANO* and J. A. CAMP0 Departamento de Q&mica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutense, 28040-Madrid, Spain (Received IO May 1991; accepted 28 June 1991)
Abstract-The reactions of the complexes [Mo(CO),($-NN)(q’-dppm)] [NN = 2,2’-bipyridyl (bpy), 1, lo-phenanthroline (phen), 2,9-dimethyl- 1,lo-phenanthroline (dmp) ; dppm = bis(diphenylphosphino)methane] with HgX, (X = Cl, Br, I, CN, SCN) led to three types of compounds [Mo(CO)&‘-NN)(X)J,Hg (NN = bpy, phen; X = Cl, Br, CN, SCN. NN = dmp ; X = CN), [Mo(CO)~(~*-NN)(~-dppm)HgI]HgI~ (NN = bpy, phen ; X = I) and [Mo(CO),(q2-dmp)(HgX)(X)] (X = Cl, Br, I, SCN), depending on the NN-ligand and the mercuric derivative employed. The fo~ation of the trinuclear complexes ~o(CO),(q”NN)(X)],Hg is favoured over the expected bimetallic derivatives, in which two metals are bridged by the dppm ligand. Bimetallic compounds are obtained when bulky ligands are present, such as dmp bonded to a molybdenum atom or I bonded to mercury, and only in the latter case is a Mo-Hg complex bridged by dppm obtained.
Heterobimetallic complexes containing a transition metal bonded to mercury are of current interest, especially because some of these have been used as intermediates in organic and organometallic synthesis. Complexes containing constraining ligands such as Ph2PCH2PPh2 [bis(diphenylphosphino)methane, dppm] are of special interest since proximity effects involved in bridging behaviour can be used to favour formation of the metal-metal bond. ’ However, dppm bridged systems involving molybdenum and mercury have not been described and we are interested in the study of this type of compound. On the other hand it has been established that complexes of the type [Mo(CO),(q*-dppm)(q’dppm)] [dppm = bis(diphenylphosphino)methane] in their reactions with transition metal derivatives are able to form dinuclear heterobimetallic complexes bridging two metals by the dppm ligand.*r3 However, no bimetallic derivatives were obtained from the reaction of ~o(CO)~(~~dppm)(~‘-dppm)]
with HgX2 (X = Cl, SCN) (although Mo-Hg bonded species have been suggested as intermediates) and new dicarbonyl molybdenum-complexes were formed by elimination of mercury.4 In a previous communication, we have reported the behaviour of the related [Mo(CO)3(q2-bpy)(q’dppm)] complex towards some metal derivatives. Molybdenum-metal complexes were formed in all cases, and in particular a trinuclear compound [Mo(CO)j(q2-bpy)(C1)]2Hg was obtained in the reaction with HgC12. * As an extension of the above results we have studied the reactions of [Mo(CO),(q2-NN)(q’dppm)] @N = 2,2’-bipyridyl (bpy), 1,lO-phenanthroline 2.9-dimethyl-l,lO-phen(phen), anthroline (dmp)] with HgX2 (X = Cl, Br, I, CN, SCN), in an attempt to form new heterobimetallic Mo-Hg complexes with dppm as bridge. RESULTS
AND DISCUSSION
The spectroscopic and analytical data of the isolated compounds are surnamed in Tables 1 and *Author to whom correspondence should be addressed. 2. 2611
2612
M. CAN0 Table
1. Analytical,
conductivity
and J. A. CAMP0
and IR data
for the complexes
[Mo(CO),(q2-NN)(X)],Hg,
[Mo(CO),(r12-NN)01-dppm)HgIlHgI, and [Mo(CO),(?2-dmp)(HgX)(X)1 Compound (Colour)
[Mo(CO),(?2-bpy)(C1)1,Hg
Analyses (%) C H N
A,,,* (ohm- ’ cm2 mol- ‘)
VCOC (cm- ‘)
32.9 (33.1
1.6 1.7
5.8 6.0)
13.2
1978sh 1950s 1935s 1850sh 1835~s
35.9 (36.4
1.6 1.6
5.5 5.7)
9.4
1978m 194Ovs 1888sh 1848s 1820~s
30.7 (31.0
1.6 1.9
4.0 4.2)
13.5
1978vs 1895sh 1870s
29.7 (30.1
1.3 1.6
5.2 5.4)
12.5
1975sh 1952s 1938s 1855sh 1838~s
32.8 (33.4
1.4 1.5
5.0 5.2)
10.2
1974m 1942s 1850s 1825~s
26.9 (27.3
1.3 1.6
3.5 3.7)
14.2
1978~s 1870s
27.7 (28.0
1.5 1.9
1.7 1.7)
52.0
1968~s 1872sh 1852~s
28.8 (29.0
1.6 1.8
1.8 1.7)
43.2
1965~s 1878sh 1852~s
[Mo(CWr12-dmp)(HgI)(I)l (Yellow)
24.0 (24.3
1.2 1.4
3.1 3.3)
10.3
1975s 1870s
[Mo(CO),(tt2-bPY)(NCS)I,Hg
33.9 (34.0
1.6 1.6
8.0 8.5)
17.6
1982~s 1950vs 1905sh 1882s 1840~s 2090sh(v& 2075s(v,,)
36.8 (37.1
1.5 1.6
7.8 8.1)
14.7
1975s 195ovs 1872~s 1855s 2095s(v,,) 2060sh(vc,q)
32.1 (32.4
1.5 1.7
7.6 8.0)
15.0
1978vs 1900s 1862~s 2098s(v&
(Yellow-orange)
[MWO) dv 2-pW(Cl)lJ% (Orange)
[Mo(CO)~(r12-dmp)(HgC1)(C1)1 (Orange)
[Mo(CO),(?2-bpy)(Br)l,Hg (Orange)
[Mo(CO)j(t12-phen)(Br)12Hg (Orange)
[Mo(CO)~(r12-dmp)(HgBr)(Br)l (Orange)
[Mo(CO),(?2-bpy)(~-dppm)HgIlHg13 (Yellow)
[Mo(CO)~(r12-phen)(~-dppm)HgIlHgI, (Yellow)
(Orange)
[Mo(CO)3(t12-phen)(NCS)12Hg (Orange)
[Mo(CO),(r12-dmp)(HgSCN)(SCN)1 (Orange-yellow)
2613
Reactivity of complexes Table l+ontinued Analyses (%) N C H
Compound (Colour)
[MotCO),(rt*-bpy)(CN)l,Hg (Yellow)
[Mo(CO),(?‘-phen)(CN)l,Hg (Orange-yellow)
[Mo(CO) dtl*-dw)(CN)l2Hg (Orange-yellow)
Amb(ohm- ’ cm*mol-‘)
VCOC (cm-- ‘)
36.0 (36.4
1.6 1.7
8.9 9.1)
12.5
1995s 1975vs 1898sh 1870~s 1845~s 2105w(v&
39.2 (39.6
1.5 1.7
8.4 8.7)
15.2
1988~s 1960~s 1895sh 1862~s 2105m(vc,)
41.7 (42.1
2.2 2.4
8.0 8.2)
9.5
1985s 1960s 1890~s 1870sh 2105w(v&
a Found ; (calculated). bin dimethylformamide solutions lo-’ M. ‘In KBr pellets ; vs = very strong, s = strong, m = medium, w = weak, sh = shoulder.
Table
2.
NMR
data
for
drvWWlW
[Mo(CO),(q*-NN)(y-
3
NN
6 (3’P)
*JP-P
(CH2 in dppm)
(ppm)
(Hz)
by
4.45bf
30.0br, 48.7bP 29.6d, 49.0d”
149
phen
4.2lbP
26.3br, 44.4bP
6 (‘I-9 (ppm>
“In (CD3)&0 solution at -20°C. bIn (CD,),CO solution at room temperature. br = broad ; d = doublet.
(a) Reactivity of [Mo(CO),(q*-NN)(q’-dppm)] (NN = bpy, phen) with HgX, (X = Cl, Br) The [Mo(CO),(q2-NN)(q’-dppm)] complex (NN = bpy, phen) reacts with mercury(I1) halide, HgX, (X = Cl, Br), in a 1 : 1 or 1: 2 molar ratio at room temperature and no CO evolution is observed. The solids isolated are insoluble in common solvents and they have been characterized as a mixture of [Mo(CO),(q2-NN)(X)],Hg and HgX,*ndppm. The IR spectra of the solids show in the carbonyl region the characteristic pattern of bands of [Mo(CO),(q2-bpy)(X)],Hg complexes ;5*6however, absorptions attributed to coordinated dppm ligand
are also observed, and suggest the presence of HgX, * ndppm (NN = bpy, phen ; X = Cl, Br). In order to confirm our hypothesis we studied compounds of the type HgX, * ndppm, synthesized by direct reactions between HgX, and dppm. New products, characterized as HgX, sndppm (X = Cl, n = l/3; X = Br, n = 1) were isolated and all of these were insoluble in common solvents.’ The 3’P-NMR spectra of the above compounds, registered in DMSO-d6, show a singlet (X = Cl, 6 = 2.25 ppm; X = Br, 6 = 2.00 ppm) with their corresponding mercury satellites.’ These signals appear at the same position as those observed for the solids formed in the reactions referred to above, and confirm the suggested presence of the adducts HgX, * ndppm in the products of these reactions. On this basis we thought that a 2 : 1 (MO : Hg) stoichiometry for the reaction between the molybdenum complex [Mo(CO),(q2-NN)(q’-dppm)] and HgX, could yield the trinuclear derivative exclusively. We have carried out these 2 : 1 reactions and the products isolated were characterized as the expected complexes [Mo(CO)~(~*-NN)(X)],Hg. This fact indicates that the dppm ligand is always liberated from the starting molybdenum complex and that the formation of HgX, * ndppm compounds occurs when an excess of HgX, with respect to the 2 : 1 molar ratio of the reaction is employed.
Reactivity of complexes
(d) Reactivity of [Mo(CO)3(~2-dmp)(~‘-dppm)] with HgX, (X = Cl, Br, I, CN, SCN) Related reactions between the complexes [Mo(CO),(~2-dmp)(~‘-dppm)] and HgX, (X = Cl, Br, I, CN, SCN) have been studied. In the starting molybdenum complex we have introduced dmp as the NN-ligand, which is more basic and presents more demanding steric effects than the others. compounds of the Surprisingly, type [Mo(CO)3(n2-dmp)(HgX)(X)] (X = Cl, Br, I, SCN) were isolated, and only products of double insertion of the type [M0(C0)~(q~-dmp)(CN)]~Hg were obtained in the reaction with Hg(CN),. This different behaviour could be attributed to the low stability of the Mo-Hg-CN bonds.”
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(Devon, U.K.). IR spectra were recorded on a Perkin-Elmer 1300 spectrophotometer with KBr pellets. The NMR spectra were recorded on a Varian XL-300 spectrometer at room temperature and -20°C operated at 299.95 MHz for ‘H and 121.42 MHz for 3’P, with (CH3)$i as internal standard for ‘H and 85% phosphoric acid as external standard for 3’P ; the solvents used were (CD3)2CO and (CD3)SO. Conductance measurements were performed in dimethylformamide solutions at room temperature.
(b) Reactions
Preparation of [Mo(CO)3(q2-NN)(X)]2Hg (NN = bpy, phen ; X = Cl, Br). 0.1 mmol of HgX, was added to a solution of [Mo(CO)~(~~-NN)(~‘CONCLUSIONS dppm)] (0.2 mmol) in dichloromethane (15 cm3). The mixture was stirred for 1 h and the precipitate forFormation of trinuclear complexes of the type med was filtered off, washed with dichloromethane [(r2-NN)(CO),00M~Hg--Mo(X)(CO)3(~2-NNll and petroleum ether (b.p. 4&6O”C) and dried in appears to be favoured by reaction between [MO vacua. (CO),(q2-NN)(L)] and HgX,; even when L is a Preparation of [Mo(CO)3(~2-NN)(X)]2Hg (NN PP-ligand coordinated in a monodentate form as = bpy, phen ; X = CN, SCN). 0.12 mm01 of q’-dppm this behaviour is not modified, and the HgX, was added to a solution of [Mo(CO)~(~~~expected bimetallic complexes in which two metals NN)(q’-dppm)] (0.24 mmol) in dichloromethane (15 are bridging by dppm ligand are not formed. cm’). The mixture was stirred for 30 min for Particular results are obtained when bulky Hg(SCN)2 and 2 h for Hg(CN)2. The solid formed ligands are present, such as in the case of dmp was filtered off, washed with petroleum ether (b.p. bonded to molybdenum or I bonded to mercury, 4060°C) and dried in vucuo. and bimetallic derivatives are formed in these Preparation of [Mo(CO)3(~2-NN)(~-dppm)HgI] cases. An intermediate species as in Fig. 2 is proHgl, (NN = bpy, phen). 0.5 mmol of HgI, was posed to explain the formation of the final cationic added to a solution of [Mo(CO),(~~-NN)(~‘compound [M0(CO),(~~-NN)(~-dpprn)Hg1]+. This dppm)] (0.25 mmol) in dichloromethane (15 cm’). fact does not occur when the NN-ligand is dmp, A colour change was observed immediately probably due to the greater electronic and steric (from violet to yellow-orange) and the formation properties of this ligand. of a yellow precipitate occurred. The mixture was stirred for 15 min, and the solid was filtered off, C washed with petroleum ether (b.p. 40-60°C) and dried in vacua. Preparation of [Mo(CO),(q2-dmp)(HgX)(X)] (X = Cl, Br, I, SCN). 0.5 mmol of HgX, was added (I+NN)(CO~MO ;----;HgI to a solution of [Mo(CO),(q2-dmp)(q ‘-dppm)] (0.25 ‘. I” mmol) in dichloromethane (10 cm3). A colour change was observed quickly (from violet to Fig. 2. orange). The compounds were obtained by precipitation with petroleum ether (b.p. 4&6O”C) after EXPERIMENTAL 5-10 min of stirring. The compound obtained with Hg(SCN)2 precipitated in the reaction medium. The (a) General solids were filtered off, washed with petroleum ether All reactions were carried out under oxygen-free (b.p. 4&60”(Z) and dried in vacua. dry nitrogen. Analytical grade solvents were used. The [Mo(CO)~(r12-NN)(r1-dppm)l Cm = by, Acknowledgement-Financial support for this work from phen, dmp) complexes were prepared as previously the Comisibn Asesora de Investigacibn Cienttica y T&described. l8 C, H and N analyses were carried out nica (CAICYT) is gratefully acknowledged (Project No. by Elemental Micro-Analysis Laboratories Ltd. 367184).
A /p ‘\
M. CAN0
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and J. A. CAMP0
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