Aryl- and diarylthioureamolybdenum carbonyls

J. inorg,nucl.Chem., 1973,Vol. 35, pp. 457-463. PergamonPress. Printedin Great Britain

ARYL-

AND

DIARYLTHIOUREAMOLYBDENUM CARBONYLS

S. C. T R I P A T H I , S. C. S R I V A S T A V A and R. D. P A N D E Y Department of Chemistry, University of Gorakhpur, Gorakhpur, (U. P.) India (Received 1 May 1972) aryl- and diarylthioureamolybdenum pentacarbonyls and nine mixed derivatives [Tr-CsHsMo(CO)2L]2 (L = aryl or diarylthiourea) have been synthesised. Bonding properties of these thioureas have been interpreted by measurement of the i.r. spectra of synthesised substituted molybdenum carbonyls. The i.r. spectra of arylthioureamolybdenum pentacarbonyls have an additional C - O band in the low frequency side of the strongest peak. This additional C - O band may be attributed to the lifting of the degeneracy of the E mode due to the unsymmetrical structures of the arylthioureas. Two C - O bands observed in [rr-C~HsMo(CO)zL]2 derivatives may be attributed to modes (A,, + B~). Abstract-Ten

INTRODUCTION

1N OUR earlier communications [ 1-4] we have reported the behaviour of some of the nitrogen donor ligands in substitution reactions with hexacarbonylmolybdenum (o). Here we describe the preparation and characterisation of several new substituted molybdenum carbonyl derivatives containing substituted thioureas as ligands. Although, there has been considerable study of the ligand behaviour of sulphur donors like the dialkyl or diarylsulphides, dialkyl- or diaryldisulphides, dithioalkanes, sulphur dioxide, sulphur trioxide etc. in the displacement of carbon monoxide in metal carbonyls no attention has been paid to substituted thioureas. Since these donors have been extensively exploited, it is surprising that they are unfamiliar in studies of the ligand exchange reactions of metal carbonyls. Only two thiourea containing metal carbonyls, tris(thiourea)tricarbonylmolybdenum (o) [5] and o- phenanthrolinethioureatricarbonylmolybdenum(o)[6] have been reported. We have used ten aryl- and diarylthioureas as ligands in two different types of reactions, i.e. with the parent hexacarbonylmolybdenum(o) in the first instance, and with cyclopentadienylmolybdenum tricarbonyl dimer in the second. Ten aryl- or diarylthioureamolybdenum pentacarbonyls, [Mo(CO)~L], and 9 mixed derivatives [Tr-C~HsMo(CO)2L]2 (L=phenylthiourea, o, m, p-tolylthioureas, c~- and /3- naphthylthioureas, sym-diphenylthiourea, sym-di-o-tolylthiourea, sym-di-p-tolylthiourea, sym-di-a-naphthylthiourea) have been synthesised. Bonding properties of these substituted thioureas are interpreted by measurement of the i.r. spectra of the aryl- or diarylthioureamolybdenum pentacarbonyls. 1. S. C. Tripathi and S. C. Srivastava, J. organometal. Chem. 23, 193 2. S. C. Tripathi and S. C. Srivastava, J. organometal. Chem. 25, 193 3. S. C. Tripathi, S. C. Srivastava and G. Prasad, Proc. Xth. Int. p. 38 (1967). 4. S. C. Tripathi, S. C. Srivastava and G. Prasad, Proc. Xlth Int. p. 447 (1968). 5. F. A. Cotton and F. Zingales, Chem. Ind. 1219 (1960). 6. L. W, Houk and G. R. Dobson, lnorg. Chem. 5, 2119 (1966). 457

(1970). (1970). Conf. Coordin. Chem., Japan, Conf. Coordin. Chem., Israel,

458

S . C . T R I P A T H I , S. C. S R I V A S T A V A and R. D. P A N D E Y RESULTS AND DISCUSSION

All the [Mo (CO)~L] compounds were prepared in 70-90% yield by straightforward thermal reactions in evacuated sealed tubes or under reflux in a nitrogen atmosphere using a 1 : 1 mixture of dichloromethane and toluene. In spite of several attempts not more than one CO group could be displaced. The products are grey or greyish black solids which decompose above 150°C without melting. They are insoluble in aliphatic or aromatic hydrocarbons, alcohols, petroleum ether and ether, and soluble in dichloromethane, acetone and tetrahydrofuran. Substitution of carbon monoxide in the cyclopentadienylmolybdenum tricarbonyl dimer by other ligands have been little studied. Arsenido- and phosphido-derivatives have been reported by Hayter et al. [7, 8]. Nyholm[9] described the three possibilities of substitution by substituted phosphine and phosphite ligands using u.v. irradiation. King [ 10] has reported the complete displacement of carbon monoxide with dimethyldisulphide with the formation of [¢rCsHsM(CHa)2S2]~ containing four sulphur bridges. Cyclohexene-sulphide [11] yielded both, the unstable monomer [~r-CsHsMo(CO)2SCrH~I] and the stable dimer [zr-CsH~Mo(CO)zSCrHI~]2. In our investigations all the reactions were carried out by two methods, namely by refluxing the aryl- or diarylthiourea and the dimer in an inert solvent under nitrogen or by u.v. irradiation. The reaction time varied between 2-2.5 hr for reflux reactions and 40-60 hr for irradiation reactions. All the reactions yielded symmetrical disubstituted derivatives [~rCsHsMo(CO)2L]z. Our efforts to prepare other derivatives, including complete displacement of carbon monoxide, have failed. All the compounds are grey or dark brown in colour and insoluble in hydrocarbons, light petroleum, alcohols and carbontetrachloride, and fairly soluble in chloroform. Infrared spectra The i.r. spectra of both classes of compounds bear a strong resemblance to the spectra of other thiourea complexes [12] supporting the assumption that the aryl- or diarylthiourea molecules are attached to molybdenum via the sulphur. A strong absorption of the parent substituted thioureas around 1100 cm -1 is very much weaker or even disappears on complex formation .This observation can be explained by the considerable change in the nature of the N - C bond, as well as of the C=S bond, on coordination of the substituted thioureas through the sulphur atom. A lowering of about 50 cm -1 in the substituted derivatives observed for the band near 720 cm -1 may be attributed to the reduced double bond character of the C---S bond. Compounds of the type [Mo(CO)~L] possess C4v symmetry. Assignments of the carbonyl bands have been done on the basis of the work by Orgel [13] Cotton 7. 8. 9. 10. 1 I. 12.

R. G. Hayter, Inorg. Chem. 2, 1031 (1963). W. R. Cullen and R. G. Hayter, J. A m. chem. Soc. 86, 1030 (1964). R.J. Haines, R. S. Nyholm and M. H. B. Stiddard, J. chem. Soc. (A)43 (1968). R. B. King, J. Am. chem. Soc. 85, 1587 (1963). P. M. Tr¢ich¢l and G. R. Wilkes, lnorg. Chem. 5, 1182 (1966). A. Yamaguchi, R. B. Penald, I. Mizushima, T. J. Lane, C. Curran and J. V. Quagliano, J. Am. chem. Soc. 80, 527 (1958). 13. L. E. Org¢l, lnorg. Chem. 1, 25 (1962).

Aryl- and diarylthioureamolybdenum carbonyls

459

and Kraihanzel[14]. Bands due to the BI mode which are Raman active are visible in the i.r. in all the complexes because the structures of the ligands interfere with perfect C4v symmetry. In addition to four bands, the i.r. spectra of arylthioureamolybdenum pentacarbonyls have a well defined shoulder in the low frequency side (1895-1887 cm -1) of the strongest peak. This could arise because the unsymmetrical structures of the arylthioureas lift the degeneracy of E mode as observed in the case of several phosphorous donor ligands[15]. The two CO stretching force constants kl and k2, i.e. force constants of the CO groups cis and trans to the substituent diarylthioureas, respectively, and k~, the C O - C O interaction constants have been evaluated by Cotton and Kraihanzel's secular equations[14]. These equations are not applicable for the calculation of C - O force constants and C O - C O interaction constants in the case of arylthioureamolybdenum pentacarbonyls due to the splitting of the E mode, hence the C - O stretching frequencies are tabulated as such in the case of [Mo (CO)s (arylthiourea)] derivatives. The CO stretching frequencies and C - O force constants (Table 1) in these derivatives are slightly higher compared to aminemolybdenum pentacarbonyls[l, 16] and lower than other derivatives, containing alkyl or arylsulphides I 17] as ligands. These data indicate that the sulphur atom in the aryl- or diarylthioureas function as significant rr-acceptors but substantially less than the sulphur atoms in other ligands such as the alkyl or arylsulphides in [Mo(CO),~L] derivatives. In the case of mixed derivatives, [Tr-CsH.~Mo(CO)2L]2, two C - O stretching bands are observed (Table 2). These bands may be assigned to modes (A,, + B~,) assuming that the M o - M o structure of [Tr-CsHsMo(CO)a]2 (local C,,h symmetry of carbonyl groups [ 18]) is retained in the substituted complexes. In the mull spectra of these complexes coupling with solid state vibrational modes leads to a lowering of the C - O frequencies in the mull phase. It appears that the band due to mode B~ is more sensitive to this effect. EXPERIMENTAL Hexacarbonylmolybdenum(o) (Climax Molybdenum Co.) was sublimed before use. Cyclopentadienylmolybdenum tricarbonyl-dimer was prepared by an established method [ 19]. All the experiments were performed in dry nitrogen or in vacuo. The u.v. lamp (30 W) used was made by Philips Co, Holland. 1. R. spectra were measured on a Perkin-Elmer spectrophotometer model 221. In [Mo(CO).~L] complexes the range 1600-2200 cm -t was examined in CHCI3 solution. Mulls were used for the range 600-1600 cm ', since CHCI3 interferes this region. Preparation o f phenylthioureapentacarbonylmolybdenum(o)

Hexacarbonylmolybdenum(o) (0.2g) and phenylthiourea (0-104 g) were refluxed in a 1:1 mixture (10 ml) of toluene and dichloromethane under nitrogen for 2 hr. A greyish black air stable solid was recovered by sweeping out the solvent with the help of nitrogen and finally drying in vacuo. Unchanged hexacarbonylmolybdenum(o) (practically nil) was removed by sublimation. The product was recrystallised from a mixture of methanol and acetone and dried in vacuo. Yield: 0.208 g, 70.9%. Anal. Found: C, 37-0, N, 2.2, H, 6.9. MoC 12HsN2SO5 requires C, 37.1 ; H, 2-0; N, 7.2%. 14. 15. 16. ! 7. 18. 19.

F. A. Cotton and C. S. Kraihanzel, J. Am. chem. Soc. 84, 4432 (1962). S. O. Grim, D. A. Wheatland and W. McFarlane, J. Am. chem. Soc. 89, 5573 (1967). F . A . Cotton and C. S. Kraihanzel, lnorg. Chem. 2, 533 (1963). F. A. Cotton and F. Zingales, J. A m. chem. Soc. 83, 351 ( 1961 ). F. C. Wilson and D. P. Shoemaker, J. chem. Phy. 27, 809 (1957). G. Wilkinson, J. Am. chem. Soc. 76, 209 (1954).

460

S . C . TRIPATHI, S. C. SRIVASTAVA and R. D. PANDEY

Table 1. CO stretching bands, CO stretching force constants and CO-CO interaction constant in [Mo(CO)sL] derivatives Compound

[(sym-CeHsNHCSNHC~Hs)Mo(CO)5]

[(sym-o-CH3C~H4NHCSNHCeH4CH3)Mo(CO)s]

[(sym-p-CH3CsH4NHCSNHCeH4CH3) Mo(CO)5]

[(sym-a-CIoHrNHCSNHC1oHT)Mo(CO)~]

[(C~HsNHCSNH2)Mo(CO)5]

[(o-CH3C6H4NHCSNH2) Mo(CO)5]

[(p-CH3C6H4NHCSNH2)Mo(CO)5]

[(m-CHaCeH4NHCSNH2)Mo(CO)5]

[(a-C10HTNHCSNH2) Mo(CO)5]

[(fl-CIoHrNHCSNH2) Mo(CO)5]

*Accuracy ___5 cm -'.

Frequency* (cm -1) 2055 w 1972 (sh) 1932 s 1900 (sh) 2055 w 1975 (sh) 1928 s 1900 (sh) 2055 w 1970 (sh) 1928 s 1900 (sh) 2051 w 1972 (sh) 1932 s 1900 (sh) 2045 w 1972 (sh) 1932 s 1900 (sh) 1890 (sh) 2045 w 1975 (sh) 1928 s 1900 (sh) 1887 (sh) 2055 w 1970 (sh) 1928 s 1900 (sh) 1890 (sh) 2045 w 1975 (sh) 1928 s 1900 (sh) 1890 (sh) 2045 w 1975 (sh) 1928 s 1900 (sh) 1895 (sh) 2045 w 1970 (sh) 1928 s 1900 (sh) 1887 (sh)

Mode

kl

k2 mdyn//~

k~

,41 14.96 15"70 B1 El A1 A1 B1 15.00 15'75 E ,41 ,41 BI 14"97 1 5 " 6 7 E A1 A1 B1 1 4 . 9 6 15.70 E ,41 .41 BI },4 1+ A ' +`4"

0.31

A1 B1 }A 1+`4' +A" `41 BI },4 1+`4' +A" A1 B1 }A 1+ A ' +A" A1 B1 }A i + A ' +,4" ,41 B1 }A 1+,4' +A"

0"37

0"33

0.31

Aryl- and diarylthioureamolybdenum carbonyls

461

Table 2. CO Stretching frequencies of mixed [*r-CsHsMo(CO)#lz derivatives CO frequencies (cm -1) A. + B~ (mull)

Compounds

1923 (s), 1930 (s), 1923 (s), 1923 (s), 1930 (s), 1923 (s), 1923 (s), 1930 (s), 1930 (s),

[CsHsMo(CO)z(CtHsN HCSNH)]z [CsHsMo(CO)2(o-CHaCoH4N HCSNH2)lz [C,~HsMo(CO)2(m-CH3CeH4N HCSN H2)]2 [CsHsMo(CO)2(p-CHaCtH4N HCSN H2)]2 [CsH~Mo(CO)z(a-C1oHrNHCSN Hz)]2 [C5HsMo(CO)z~-C10HTNHCSN Hz)]2 [CsHtMo(CO)z(sym-CoHsNHCSNHCoHs)]2 [CsH~Mo(CO)z(sym-o-CH3CoH4NHCSNHCoH4CH3)]2 [C~HsMo(CO)2(sym-c~-C10HTNHCSN HCI0HT)]2

1816 (s) 1801 (s) 1816 (s) 1816 (s) 1826 (s) 1816 (s) 1801 (s) 1801 (s) 1801 (s)

(in CHCI3)

1949 (s), 1930 (s), 1930 (s), 1923 (s), 1930 (s), 1930 (s), 1949 (s), 1942 (s), 1923 (s),

1845 (s) 1835 (s) 1835 (s) 1835 (s) 1852 (s) 1852 (s) 1835 (s) 1852 (s) 1835 (s)

Table 3 Complex

Reflux time Yield (hr) (%) C

[(o-CH3CtHaNHCSNHz)Mo(CO)5]

2'5

70"4

[(p-CH3C6H4NHCSNH2)Mo(CO)s]

2"5

76'6

[(m-CH3CaH4NHCSNHz)Mo(CO).~]

2

74"4

[(a-CloHrNHCSNH~)Mo(CO)5]

3

85' 1

[(/3-C10H7NHCSNH2)Mo(CO)5]

1'5

90'0

[(sym-CeH.~N HCSN HCtH~)Mo(CO)5]

1.5

88.4

[(sym-o-CH3C6H4NHCSNHC6H4CHa)Mo(CO)5]

2.5

83.5

[(sym-p-CH3CtH4N HCSNHCaH4CH3)Mo(CO)5]

80.0

80.0

2.5

76-7

[(sym-a-C10H7NHCSNHC10HT)Mo(CO)5]

F 38"4 C 38"8 F 38"9 C 38"8 F 37"9 C 38"8 F 42'9 C 43-8 F 43'6 C 43'8 F 47.4 C 46.5 F 49.3 C 48.7 F 49-3 C 48.7 F 56.4 C55.3

Analysis H 2"8 2'4 2'4 2'4 2"2 2"4 2'2 2"2 2" I 2"2 2.8 2.6 3.4 3.2 3-0 3.2 3.1 2.8

N 7"3 6'9 6'9 6-9 6.5 6.9 6-3 6"3 6.4 6'3 6.4 6.0 5-8 5-6 5.5 5.6 4.9 4.9

Reflux time, yields and analyses of other substituted molybdenum pentacarbonyl complexes are given in Table 3.

Preparation of tetracarbonylbis (penylthiourea ) di-~r-cyclopentadienyldimolybdenum( l ) Reflux method. Cyclopentadienylmolybdenum tricarbonyl dimer[19] (0.4g) and phenylthiourea (0-3g) were refluxed in a 1 : 1 mixture (20 ml) of toluene and dichloromethane for 2.5 hr under nitrogen. Greyish crystals appeared at the completion of reaction. Solvents were evaporated by bubbling nitrogen into the reaction flask. The solid mass was washed several times with ethanol to remove unreacted phenylthiourea. The product was recrystallised in chloroform under nitrogen and was dried in vacuo. Yield: 0.42 g (70%). Anal. Found: C, 45.2; H, 3.4; N, 7.5%. MoC2~H26N4S204 requires C, 45.5; H, 3.5; N, 7.5%.

Reddish brown Grey Grey Yellowish grey

2.5/50 2-5/50 2.5/60 2.5/60 2-5/60 2.5/60

[CsHsMo(CO)2(p-CH3CeH4NHCSNH~)]~

[CsHsMo(CO)2(a-C10HTNHCSN H2)]~

[CsH5Mo(CO)2(/3-CjoHTNHCSNH~)]2

[CsHsMo(CO)2(sym-CoHsNHCSNHCeHs)]~

[CsHsMo(CO)2(sym-o-CH3C6H4N HCSN HC6H4CH3)]2

[CsHsMo(CO)2(sym-a-C10HrNHCSNHCloHT)]~

Brown

Brown

Reddish brown

2.5/50

[CsHsMo(CO)2(m-CHaCsH4NHCSNH2)h

56.6[43"7

54.0/42.1

63.3/38.5

53-8/31-6

70.4/54.0

78.0/46.4

64.4/34-1

76.0/43.2

Yield (%) Reflux method/ irradiation method

grey

Colour

2.5/50

Preparation Reflux time/ irradiation time (hr)

[CsHsMo(CO)z(o-CH~C6H4NH CSNHz)]2

Compound

Table 4

F46-8 C 46"9 F 45"8 C 46"9 F 45.7 C 46.9 F 50"8 C 51.5 F51.4 C 51"5 F 53-6 C 53-9 F 55"6 C 55-8 F 61-2 C 61 "6

3"7 3-9 3"1 3"9 3-7 3.9 2-9 3-5 3.1 3.5 3"5 3.8 4.0 4-4 3-5 3-8

7-3 7"3 7"1 7-3 7.0 7.3 6-6 6.6 6-6 6.6 6-1 6-3 5.8 5.9 5.0 5.1

Analysis (%) C H N

-¢

e~

<

O~

Aryl- and diarylthioureamolybdenum carbonyls

463

U,V. irradiation method. Above reaction mixture was irradiated by u.v. light for 40 hr. Work up for the isolation of the product was identical. Yield 0.34 g (56.3%). Preparation, yield and analysis of other derivatives synthesised by both the methods are given in Table 4. A cknowledgement- Financial support given by C.S.I.R. (New Delhi) to carry out this work is grate-

fully acknowledged. A gift of molybdenum hexacarbonyl from the Climax Molybdenum Co. is also gratefully acknowledged.