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The reaction of niobium(V) and tantalum(V) halides with aliphatic amines
JOURNAL OF THE LESS-COMMON METALS
40
THE REACTION
OF NIOBIUM(V)
AND TANTALUM(V)
ALIPHATIC I’. J. H. CARNELL Department
AND
WITH
AMINES G. W. A. FOWLES
of Chemistry, The University, (Received
HALIDES
Southampton (Great Britain)
July z8th, 1961)
SUMMARY The reactions of niobium(V)chlor with a range of primary and secondary aliphatic amines have been studied, and some of the analogous reactions of niobium(V)brom and tantalum(V)brom have also been examined. The results of these studies have been correlated with earlier work on the reactions of the niobium(V) and tantalum(V) halides with amines. With secondary aliphatic amines, NHRa, all the halides give aminobasic metal halides, MXa(NR&*NHRz; molecular weight studies on some of these show them to be monomeric in benzene solution. The higher primary amines, NHzR, give analogous products, MXS(NHR)Z*NH~R, but with ethylamine and methylamine there is evidence that a third M-X bond is solvolysed. Tertiaryamines appear to form insoluble adducts. INTRODUCTION
Recently, the reactions of tantalum(V) chloride with aliphatic amines have been studied in some detailr, and a more limited investigation2 of some of the analogous reactions of niobium(V) chloride has also been made. These latter investigations have now been extended to cover a wider range of amines, and several analogous reactions of niobium(V) and tantalum(V) bromide have been examined. The results we quote here confirm the general observation that the more covalent halides of the transition metals undergo solvolytic reactions with both primary and secondary aliphatic amines. Since the products formed with secondary amines have been characterised more fully than the rest, they will be considered first. Table I summarises the results obtained in both the earlier and present work. TABLE PRODUCTS
OF THE
REACTIONS
OF SECONDARY AND
AMINES
I WITH
HALIDES
OF QUINQUEVALENT
H&de
NHMen
NHEts
NbCls NbBrs TaCIh TaBrs
NbCls (NMez)a*NHMez NbBrs(NMes)s*NHMes* TaCla (NMez)z*NHMez TaBrs (NMe+*NHMen*
NbClr(NEt&*NHEtz* TaC13(NEtz)a*NHEtz* -
* Compounds
NIOBIUM
TANTALUM
described in the experimental
section of this paper. J. Less-Common
Metals, 4 (Ig6z) 40-45
REACTIONOF Nb(V) ANDTa(V) HALIDESWITHALIPHATICAMINES The reactions
may be described MXs
+
5
by the general
41
equation:
NHRz = MX3(NR&*NHR2 + z NHRz.HX
The aminobasic metal halides are soluble in benzene, and can be extracted almost although minor contamination by the quantitatively from the reaction mixture, amine hydrohalide is likely (especially with the diethylamine products) unless at least two successive extractions are made. The two chloro compounds, MCL(NMe&. NHMe2, have been shown to be monomeric in benzene solution, and it is likely that the other analogous compounds will also be unassociated in solution. The co-ordinated molecule of amine enables the metal atoms to achieve a covalency of six, presumably with octahedral configurations. It is interesting to compare these compounds with those derived from the analogous product, MoClsreactions of molybdenum(V) chloride 3. Thus the dimethylamine (NMez)z.NHMez, is directly analogous, and the molybdenum atom again achieves a covalency of six by the co-ordination of a molecule of dimethylamine. Diethylamine and di-n-propylamine, on the other hand, give rise to products [MoCI~(NR&]Z, in which the covalency of six is achieved by dimerisation. The quinquevalent molybdenum atom is rather smaller than the niobium atom, since the extra electron enters a 4d level and does not completely shield the additional positive charge on the nucleus, so that although the niobium atom is big enough to take up a molecule of any of the amines, the smaller molybdenum atom cannot manage this with the larger diethylamine and di-n-propylamine molecules. By using the more strongly nucleophilic diethylamine anion, [NEt$, BRADLEY ANDTHOMAS~have recently succeeded in breaking all five tantalum-chlorine bonds; the product isolated appeared to be Ta(NEt&(NEt). Although it is clear that solvolysis occurs in the primary amine reactions, the products have not always been so well characterised, since separation of the aminobasic metal halide from the amine hydrohalide is not always possible. In its reactions with n-propylamine and n-butylamine, niobium(V) chloride behaves in an analogous manner to tantalum(V) chloride, two niobium-chlorine bonds being solvolysed giving the compounds NbCls(NHR)z.NHzR; the co-ordinated molecule of amine presumably gives an octahedral configuration to the niobium atom. Molybdenum(V) chloride behaves in just the same way with n-butylamine, but with n-propylamine two products are formed: MoCls(NHPrn)2.NHzPr” and [MoC12(NHPm)3]2; the latter compound is the major product. Since these experiments with molybdenum(V) chloride show that solvolysis is greater with the lower members of the primary amine series, we might expect a similar behaviour with the niobium(V) and tantalum(V) halides. This is confirmed by the results of the niobium(V) chloride-ethylamine reaction, in which two niobium-chlorine bonds are solvolysed quite quickly and the third more slowly. After some three months the reaction appears complete, and corresponds to the equation : NbCl5 + 6 NHzEt
=
NbCh(NHEt)a
+
3 NHzEt*HCl
the products have been separated quantitatively. Since ethylamine effects the solvolysis of three niobium-chloride bonds, it is clear that methylamine must do the same. This is consistent with the original observationzthat smallamounts of [NbC12(NHMe)& could be extracted from the reaction mixture with chlorobenzene; it was assumed that J. Less-Common
Metals, 4 (1962)
40-45
P. J. H. CARNELL,
42
G. W. A. FOWLES
the bulk of the product was insoluble because it was polymerised to a greater extent. The overall composition of the products of the niobium(V) chloride-methylamine reaction depends on the reaction time, the amine uptake increasing with time, and this is again consistent with the solvolysis of three niobium-chlorine bonds, two very easily and the third more slowly. The position is much less certain with the analogous reactions of tantalum(V) chloride, since no separations can be effected of the products of either the ethylamine or methylamine reactions. The results were originally interpreted on the basis of only two tantalum-chlorine bonds being solvolysed, the evidence for this being largely based on thermal decomposition studies. Thus tantalum(V) chloride takes up seven moles of methylamine, three of which are lost on heating ilz uacuo to 100%; a further mole of amine is lost at 150%. This seemed consistent with the scheme: TaClh +
7 NHaMe
= TaCls(NHMe)2*3 NHzMe + z NHsMeaHCI 1 100% TaCls(NHMe)z + z NHaMe*HCl J 15o’C TaCls(NMe) + z NHzMe*HCl
This was preferred to postulating a back reaction between the aminobasic tantalum(V) chloride and methylamine hydrochloride. It is, however, in contrast to the behaviour of niobium(V) chloride. The reactions with tertiary amines are also somewhat inconclusive, since the products are insoluble in the usual solvents, so that it is not established whether they are single substances or mixtures. Both of the chlorides, and the bromide of niobium, give diamagnetic products of overall composition MX5.2 NMes. Since no reduction in valence state occurs, the products must be considered either as simple adducts or mixtures of solvolysis products; solvolysis is less likely since it involves the breaking of a C-H or N-C bond. Pending further structural information we formally represent the products as adducts. Tantalum(V) bromide does not react completely with trimethylamine, even over a period of two years, but this is probably because the surface of the bromide becomes covered with a layer of insoluble reaction products. EXPERIMENTAL
The halides were prepared by heating the metal powder in a stream of the halogen vapour, and purified by sublimation.
Found
y.
Comfmund
NbCls NbBrs TaBr5
Nb
Ta
Cl
Br
Nb
34.6 19.0 -
31.7
65.6 -
79.9 68.5
34.5 18.9 -
Bf
31.2
65.7 -
81.1 68.8
Amines were purified as described previously. Analyses were made for the elements in the usual way. Wherever possible, percentage analyses were made, but some reaction products clung tenaciously to the J. Less-Common
Metals, 4 (1962) 40-45
REACTIONOF Nb(V) AND Ta(V) HALIDES WITH ALIPHATICAMINES
43
sides of the vessel and were hydrolysed in situ; in such cases only ratios are quoted. Reactions were carried out in all-glass closed vacuum systems with the complete exclusion of moisture. With some systems, the reactants were mixed in a weighed bulb, the excess of amine distilled off, and the overall composition of the product determined by weight difference. In all reactions the halide and amine were sealed in ampoules, shaken mechanically for several days, and then placed on one side until examination. Excess of amine was removed and the residue treated with benzene in an attempt to extract any aminobasic metal halide. With some reaction products, nothing dissolved in benzene, and in these cases other more polar solvents such as chlorobenzene were also tried; in the systems subsequently described, however, these solvents were no more successful than benzene. Solvents such as alcohols dissolved up the mixtures through an irreversible reaction with the aminobasic metal halide. With some of the higher amines, the metal compound was contaminated with amine hydrochloride, but when the extract was retreated with benzene a clean separation then resulted. (i) Niobium(V)
chloride-methylamine
As shown in Figs. I(a) and I(b), the overall composition of the white products became NbCls.6 NHsMe and NbCls.4 NHzMe after prolonged pumping at 2o°C and 100°C respectively. In ampoule experiments, more methylamine appeared to be associatedwith the niobium(V) chloride (cf. Table II).
I IO
I
20
I
I
30
Time (h) -
40
Fig. I. Overall composition of the product of the NbCls-NHzMe reactiox TABLE II PUP?$i?&,g RU92 NO.
I 2
3
Temp. (“Cl 20
40 IO0
TiV%e (W
composittin
Overall Nb:Cl:N
I2
1.00
I2
I.00
8
:4.9g
:6.4g
:4,91 : 5.87 1.00 : 4.89 : 4.88
None of the product was soluble in benzene. J.
Less-Common
Metals,
4 (1962)
40-45
P. J. H. CARNELL,
44
G. W. A. FOWLES
(iz;) Niobiwm(V) chloride-ethylamine Removal of excess of ethylamine from an ampoule product gave a yellow, glass-like solid, from which further ethylamine could only be slowly removed in vacua. However, when the reaction was carried out in benzene, with only a small excess of amine, the product was a powder, the composition of which depended on the reaction time, (cJ Table III). The product was kept in vacua for 12.h at 40’ before analysis.
TABLE Run NO. I
2
3
Reaction
III
time
3 days days Several months 12
compostiion
Ove*all Nb:CI:N
I.00 : 4.93 : 5.54 I.00 : 4.92 :5.63 I .oo : 4.92 : 6.09
When the product of 3 months’ reaction was extracted with benzene, a residue of 3 moles of ethylamine hydrochloride (found (%): 43.8 Cl, 17.2 N; talc. (%) for CsHaNCl: 43.5 Cl, 17.2 N) remained. The composition of the soluble solid varied from Nb : Cl :N = 1.0 : 2.8 : 3.0 to 1.0 : 2.0 : 3.0, the Nb : Cl ratio getting progressively nearer to I : z as the reaction time was increased. Found (for product of run 3) : Nb : Cl : N = 1.00 : 2.03 : 2.97. (iii) Niobium(V)
chloride-n-propylamine
Treatment of the reaction mixture gave a soluble orange solid (found (%) : 25.1 Nb, 28.2 Cl, 11.4 N; NbCls(NHPrn)z*NHaPrn requires (%): 24.7 Nb, 28.3 Cl, 11.2 N), and a residue of two moles of Iz-propylamine hydrochloride (found: 36.2 Cl, 14.3 N; CaHioNCl requires: 37.1 Cl, 14.7 N). (iv) Niobium(V)
chloride-n-butylamine
A two-stage extraction of the products with benzene gave a residue of n-butylamine hydrochloride (found: 32.4 Cl, 12.8 N; C4HizNCl requires: 32.4 Cl, 12.8 N), and the niobium compound NbCb(NHBun)z*NH2Bun (found: Nb : Cl : N = 1.00 : 3.01 : 3.03). (v) Niobium(V)
chloride-diethylamine reaction
By using the two-stage benzene extraction procedure, the niobium portion of the product was again obtained pure. Found (%): 21.6 Nb, 24.7 Cl, 9.7 N; NbCls(NEt&* NHEta requires (%): 22.3 Nb, 25.4 Cl, 10.1 N. (vtJ Niobium(V)
bromide-methylamine
The greenish-white solid had the analysis (%) : 13.4 Nb, 55.9 Br, 14.2 N. NbBrh * 7 NHzMe requires (%) : 13.1 Nb, 56.3 Br, 13.8 N. None of the product dissolved in benzene or chlorobenzene. (vii) Niobium(V)
bromide-dimethylamine reaction
This resembled the analogous reaction of niobium(V) chloride, and a brown solid J. Less-Common
Metals,
4 (1962) 40-45
REACTIONOF
Nb(V) AND Ta(V) HALIDESWITHALIPHATICAMINES
45
could be extracted with benzene. Found (%) : 2o.z Nb, 51.8 Br, 8.7 N. NbBra(NMe&* NHMeg requires (%): 20.0 Nb, 51.5 Br, 9.0 N. (viii) Niobium(V)
bromide- trimethylamine
The pale brown solid, which was insoluble in organic solvents, had an analysis (%) : 15.6 Nb, 65.0 Br, 4.6 N. NbBrS.2 NMe3 requires: 15.2 Nb, 65.4 Br, 4.6 N. The solid was diamagnetic (x = -0.196.106 e.m.u.). (ix) Tantalum(V)
chloride-diethylamine
Previously reported experiments were unable to effect a complete separation of the products, but by a process of successive extractions with benzene the pure aminobasic tantalum(V) chloride, TaCb(NEt&*NHEtz has now been obtained. Found: Ta : Cl :N = 1.00 : 2.91 : 2.95. (x) Tantalum(V)
bromide-methylamine
The pale yellow solid had a variable overall composition, TaBrbaxNHzMe, with x between 7 and 8 ,after it had been heated in vacua for at least 12 h at 50%. None of the solid dissolved in organic solvents. (xi) Talztalum(V) bromide-dimethylamine Weighed bulb experiments showed the orange product to have the overall composition TaBrs.5 NHMe2, after heating to constant weight at 40°C in vacua, and a similar composition was obtained for the products of the ampoule reactions. Found (%): 32.0 Ta, 43.0 Br, 7.30 N. TaBrs(NMe&.NHMe2 requires (y’): 32.7 Ta, 43.3 Br, 7.50 N. (xii) Tantalum(V)
bromide-trimethylamine
Only a small amount
of surface reaction
had occurred
even after two years.
ACKNOWLEDGEMENT
We gratefully acknowledge the award by the University of Southampton.
of a maintenance
grant
to P. J. H. CARNELL
REFERENCES
1 P. J. H.
CARNELL AND G. W. A. FOWLES, .I. Chem. Sot., (1959) 4113. 2 G. W. A. FOWLES AND C. M. YLEASS, J. Chem. Sot., (1957)2078. 3 D. A. EDWARDS AND G. W. A. FOWLES, J. Chem. Sot., (1961) 24. 4 D. C. BRADLEY AND I. M. THOMAS, Proc. Chem. SOL, (1959) 225.
J. Less-Common
Metals,
4 (1962) 40-45
40
THE REACTION
OF NIOBIUM(V)
AND TANTALUM(V)
ALIPHATIC I’. J. H. CARNELL Department
AND
WITH
AMINES G. W. A. FOWLES
of Chemistry, The University, (Received
HALIDES
Southampton (Great Britain)
July z8th, 1961)
SUMMARY The reactions of niobium(V)chlor with a range of primary and secondary aliphatic amines have been studied, and some of the analogous reactions of niobium(V)brom and tantalum(V)brom have also been examined. The results of these studies have been correlated with earlier work on the reactions of the niobium(V) and tantalum(V) halides with amines. With secondary aliphatic amines, NHRa, all the halides give aminobasic metal halides, MXa(NR&*NHRz; molecular weight studies on some of these show them to be monomeric in benzene solution. The higher primary amines, NHzR, give analogous products, MXS(NHR)Z*NH~R, but with ethylamine and methylamine there is evidence that a third M-X bond is solvolysed. Tertiaryamines appear to form insoluble adducts. INTRODUCTION
Recently, the reactions of tantalum(V) chloride with aliphatic amines have been studied in some detailr, and a more limited investigation2 of some of the analogous reactions of niobium(V) chloride has also been made. These latter investigations have now been extended to cover a wider range of amines, and several analogous reactions of niobium(V) and tantalum(V) bromide have been examined. The results we quote here confirm the general observation that the more covalent halides of the transition metals undergo solvolytic reactions with both primary and secondary aliphatic amines. Since the products formed with secondary amines have been characterised more fully than the rest, they will be considered first. Table I summarises the results obtained in both the earlier and present work. TABLE PRODUCTS
OF THE
REACTIONS
OF SECONDARY AND
AMINES
I WITH
HALIDES
OF QUINQUEVALENT
H&de
NHMen
NHEts
NbCls NbBrs TaCIh TaBrs
NbCls (NMez)a*NHMez NbBrs(NMes)s*NHMes* TaCla (NMez)z*NHMez TaBrs (NMe+*NHMen*
NbClr(NEt&*NHEtz* TaC13(NEtz)a*NHEtz* -
* Compounds
NIOBIUM
TANTALUM
described in the experimental
section of this paper. J. Less-Common
Metals, 4 (Ig6z) 40-45
REACTIONOF Nb(V) ANDTa(V) HALIDESWITHALIPHATICAMINES The reactions
may be described MXs
+
5
by the general
41
equation:
NHRz = MX3(NR&*NHR2 + z NHRz.HX
The aminobasic metal halides are soluble in benzene, and can be extracted almost although minor contamination by the quantitatively from the reaction mixture, amine hydrohalide is likely (especially with the diethylamine products) unless at least two successive extractions are made. The two chloro compounds, MCL(NMe&. NHMe2, have been shown to be monomeric in benzene solution, and it is likely that the other analogous compounds will also be unassociated in solution. The co-ordinated molecule of amine enables the metal atoms to achieve a covalency of six, presumably with octahedral configurations. It is interesting to compare these compounds with those derived from the analogous product, MoClsreactions of molybdenum(V) chloride 3. Thus the dimethylamine (NMez)z.NHMez, is directly analogous, and the molybdenum atom again achieves a covalency of six by the co-ordination of a molecule of dimethylamine. Diethylamine and di-n-propylamine, on the other hand, give rise to products [MoCI~(NR&]Z, in which the covalency of six is achieved by dimerisation. The quinquevalent molybdenum atom is rather smaller than the niobium atom, since the extra electron enters a 4d level and does not completely shield the additional positive charge on the nucleus, so that although the niobium atom is big enough to take up a molecule of any of the amines, the smaller molybdenum atom cannot manage this with the larger diethylamine and di-n-propylamine molecules. By using the more strongly nucleophilic diethylamine anion, [NEt$, BRADLEY ANDTHOMAS~have recently succeeded in breaking all five tantalum-chlorine bonds; the product isolated appeared to be Ta(NEt&(NEt). Although it is clear that solvolysis occurs in the primary amine reactions, the products have not always been so well characterised, since separation of the aminobasic metal halide from the amine hydrohalide is not always possible. In its reactions with n-propylamine and n-butylamine, niobium(V) chloride behaves in an analogous manner to tantalum(V) chloride, two niobium-chlorine bonds being solvolysed giving the compounds NbCls(NHR)z.NHzR; the co-ordinated molecule of amine presumably gives an octahedral configuration to the niobium atom. Molybdenum(V) chloride behaves in just the same way with n-butylamine, but with n-propylamine two products are formed: MoCls(NHPrn)2.NHzPr” and [MoC12(NHPm)3]2; the latter compound is the major product. Since these experiments with molybdenum(V) chloride show that solvolysis is greater with the lower members of the primary amine series, we might expect a similar behaviour with the niobium(V) and tantalum(V) halides. This is confirmed by the results of the niobium(V) chloride-ethylamine reaction, in which two niobium-chlorine bonds are solvolysed quite quickly and the third more slowly. After some three months the reaction appears complete, and corresponds to the equation : NbCl5 + 6 NHzEt
=
NbCh(NHEt)a
+
3 NHzEt*HCl
the products have been separated quantitatively. Since ethylamine effects the solvolysis of three niobium-chloride bonds, it is clear that methylamine must do the same. This is consistent with the original observationzthat smallamounts of [NbC12(NHMe)& could be extracted from the reaction mixture with chlorobenzene; it was assumed that J. Less-Common
Metals, 4 (1962)
40-45
P. J. H. CARNELL,
42
G. W. A. FOWLES
the bulk of the product was insoluble because it was polymerised to a greater extent. The overall composition of the products of the niobium(V) chloride-methylamine reaction depends on the reaction time, the amine uptake increasing with time, and this is again consistent with the solvolysis of three niobium-chlorine bonds, two very easily and the third more slowly. The position is much less certain with the analogous reactions of tantalum(V) chloride, since no separations can be effected of the products of either the ethylamine or methylamine reactions. The results were originally interpreted on the basis of only two tantalum-chlorine bonds being solvolysed, the evidence for this being largely based on thermal decomposition studies. Thus tantalum(V) chloride takes up seven moles of methylamine, three of which are lost on heating ilz uacuo to 100%; a further mole of amine is lost at 150%. This seemed consistent with the scheme: TaClh +
7 NHaMe
= TaCls(NHMe)2*3 NHzMe + z NHsMeaHCI 1 100% TaCls(NHMe)z + z NHaMe*HCl J 15o’C TaCls(NMe) + z NHzMe*HCl
This was preferred to postulating a back reaction between the aminobasic tantalum(V) chloride and methylamine hydrochloride. It is, however, in contrast to the behaviour of niobium(V) chloride. The reactions with tertiary amines are also somewhat inconclusive, since the products are insoluble in the usual solvents, so that it is not established whether they are single substances or mixtures. Both of the chlorides, and the bromide of niobium, give diamagnetic products of overall composition MX5.2 NMes. Since no reduction in valence state occurs, the products must be considered either as simple adducts or mixtures of solvolysis products; solvolysis is less likely since it involves the breaking of a C-H or N-C bond. Pending further structural information we formally represent the products as adducts. Tantalum(V) bromide does not react completely with trimethylamine, even over a period of two years, but this is probably because the surface of the bromide becomes covered with a layer of insoluble reaction products. EXPERIMENTAL
The halides were prepared by heating the metal powder in a stream of the halogen vapour, and purified by sublimation.
Found
y.
Comfmund
NbCls NbBrs TaBr5
Nb
Ta
Cl
Br
Nb
34.6 19.0 -
31.7
65.6 -
79.9 68.5
34.5 18.9 -
Bf
31.2
65.7 -
81.1 68.8
Amines were purified as described previously. Analyses were made for the elements in the usual way. Wherever possible, percentage analyses were made, but some reaction products clung tenaciously to the J. Less-Common
Metals, 4 (1962) 40-45
REACTIONOF Nb(V) AND Ta(V) HALIDES WITH ALIPHATICAMINES
43
sides of the vessel and were hydrolysed in situ; in such cases only ratios are quoted. Reactions were carried out in all-glass closed vacuum systems with the complete exclusion of moisture. With some systems, the reactants were mixed in a weighed bulb, the excess of amine distilled off, and the overall composition of the product determined by weight difference. In all reactions the halide and amine were sealed in ampoules, shaken mechanically for several days, and then placed on one side until examination. Excess of amine was removed and the residue treated with benzene in an attempt to extract any aminobasic metal halide. With some reaction products, nothing dissolved in benzene, and in these cases other more polar solvents such as chlorobenzene were also tried; in the systems subsequently described, however, these solvents were no more successful than benzene. Solvents such as alcohols dissolved up the mixtures through an irreversible reaction with the aminobasic metal halide. With some of the higher amines, the metal compound was contaminated with amine hydrochloride, but when the extract was retreated with benzene a clean separation then resulted. (i) Niobium(V)
chloride-methylamine
As shown in Figs. I(a) and I(b), the overall composition of the white products became NbCls.6 NHsMe and NbCls.4 NHzMe after prolonged pumping at 2o°C and 100°C respectively. In ampoule experiments, more methylamine appeared to be associatedwith the niobium(V) chloride (cf. Table II).
I IO
I
20
I
I
30
Time (h) -
40
Fig. I. Overall composition of the product of the NbCls-NHzMe reactiox TABLE II PUP?$i?&,g RU92 NO.
I 2
3
Temp. (“Cl 20
40 IO0
TiV%e (W
composittin
Overall Nb:Cl:N
I2
1.00
I2
I.00
8
:4.9g
:6.4g
:4,91 : 5.87 1.00 : 4.89 : 4.88
None of the product was soluble in benzene. J.
Less-Common
Metals,
4 (1962)
40-45
P. J. H. CARNELL,
44
G. W. A. FOWLES
(iz;) Niobiwm(V) chloride-ethylamine Removal of excess of ethylamine from an ampoule product gave a yellow, glass-like solid, from which further ethylamine could only be slowly removed in vacua. However, when the reaction was carried out in benzene, with only a small excess of amine, the product was a powder, the composition of which depended on the reaction time, (cJ Table III). The product was kept in vacua for 12.h at 40’ before analysis.
TABLE Run NO. I
2
3
Reaction
III
time
3 days days Several months 12
compostiion
Ove*all Nb:CI:N
I.00 : 4.93 : 5.54 I.00 : 4.92 :5.63 I .oo : 4.92 : 6.09
When the product of 3 months’ reaction was extracted with benzene, a residue of 3 moles of ethylamine hydrochloride (found (%): 43.8 Cl, 17.2 N; talc. (%) for CsHaNCl: 43.5 Cl, 17.2 N) remained. The composition of the soluble solid varied from Nb : Cl :N = 1.0 : 2.8 : 3.0 to 1.0 : 2.0 : 3.0, the Nb : Cl ratio getting progressively nearer to I : z as the reaction time was increased. Found (for product of run 3) : Nb : Cl : N = 1.00 : 2.03 : 2.97. (iii) Niobium(V)
chloride-n-propylamine
Treatment of the reaction mixture gave a soluble orange solid (found (%) : 25.1 Nb, 28.2 Cl, 11.4 N; NbCls(NHPrn)z*NHaPrn requires (%): 24.7 Nb, 28.3 Cl, 11.2 N), and a residue of two moles of Iz-propylamine hydrochloride (found: 36.2 Cl, 14.3 N; CaHioNCl requires: 37.1 Cl, 14.7 N). (iv) Niobium(V)
chloride-n-butylamine
A two-stage extraction of the products with benzene gave a residue of n-butylamine hydrochloride (found: 32.4 Cl, 12.8 N; C4HizNCl requires: 32.4 Cl, 12.8 N), and the niobium compound NbCb(NHBun)z*NH2Bun (found: Nb : Cl : N = 1.00 : 3.01 : 3.03). (v) Niobium(V)
chloride-diethylamine reaction
By using the two-stage benzene extraction procedure, the niobium portion of the product was again obtained pure. Found (%): 21.6 Nb, 24.7 Cl, 9.7 N; NbCls(NEt&* NHEta requires (%): 22.3 Nb, 25.4 Cl, 10.1 N. (vtJ Niobium(V)
bromide-methylamine
The greenish-white solid had the analysis (%) : 13.4 Nb, 55.9 Br, 14.2 N. NbBrh * 7 NHzMe requires (%) : 13.1 Nb, 56.3 Br, 13.8 N. None of the product dissolved in benzene or chlorobenzene. (vii) Niobium(V)
bromide-dimethylamine reaction
This resembled the analogous reaction of niobium(V) chloride, and a brown solid J. Less-Common
Metals,
4 (1962) 40-45
REACTIONOF
Nb(V) AND Ta(V) HALIDESWITHALIPHATICAMINES
45
could be extracted with benzene. Found (%) : 2o.z Nb, 51.8 Br, 8.7 N. NbBra(NMe&* NHMeg requires (%): 20.0 Nb, 51.5 Br, 9.0 N. (viii) Niobium(V)
bromide- trimethylamine
The pale brown solid, which was insoluble in organic solvents, had an analysis (%) : 15.6 Nb, 65.0 Br, 4.6 N. NbBrS.2 NMe3 requires: 15.2 Nb, 65.4 Br, 4.6 N. The solid was diamagnetic (x = -0.196.106 e.m.u.). (ix) Tantalum(V)
chloride-diethylamine
Previously reported experiments were unable to effect a complete separation of the products, but by a process of successive extractions with benzene the pure aminobasic tantalum(V) chloride, TaCb(NEt&*NHEtz has now been obtained. Found: Ta : Cl :N = 1.00 : 2.91 : 2.95. (x) Tantalum(V)
bromide-methylamine
The pale yellow solid had a variable overall composition, TaBrbaxNHzMe, with x between 7 and 8 ,after it had been heated in vacua for at least 12 h at 50%. None of the solid dissolved in organic solvents. (xi) Talztalum(V) bromide-dimethylamine Weighed bulb experiments showed the orange product to have the overall composition TaBrs.5 NHMe2, after heating to constant weight at 40°C in vacua, and a similar composition was obtained for the products of the ampoule reactions. Found (%): 32.0 Ta, 43.0 Br, 7.30 N. TaBrs(NMe&.NHMe2 requires (y’): 32.7 Ta, 43.3 Br, 7.50 N. (xii) Tantalum(V)
bromide-trimethylamine
Only a small amount
of surface reaction
had occurred
even after two years.
ACKNOWLEDGEMENT
We gratefully acknowledge the award by the University of Southampton.
of a maintenance
grant
to P. J. H. CARNELL
REFERENCES
1 P. J. H.
CARNELL AND G. W. A. FOWLES, .I. Chem. Sot., (1959) 4113. 2 G. W. A. FOWLES AND C. M. YLEASS, J. Chem. Sot., (1957)2078. 3 D. A. EDWARDS AND G. W. A. FOWLES, J. Chem. Sot., (1961) 24. 4 D. C. BRADLEY AND I. M. THOMAS, Proc. Chem. SOL, (1959) 225.
J. Less-Common
Metals,
4 (1962) 40-45