Dec. 5, 1960
TRANSITION METALIONCOMPLEXES OF DIMETHYL SULFOXIDE
6013
ends and 51% middles with no branches being observed, when the reaction was carried out exactly as reported.* This is an example of the fact that reorganization often occurs during a reaction and that structure proofs acceptable in organic chemistry generally do not apply t o inorganic chemistry or to the organic derivatives of elements in the second row or below in the Periodic Table! Although use of hydrolysis t o investigate inorganic structures often leads to false conclusions,5 the predominately unbranched polyphosphoryldimethylamides appear to represent the unusual case in which the structure of the reaction products of hydrolysis carried out under optimum conditions can be related approximately to the structure of the unhydrolyzed substance. In other words, the data indicate that all dimethylamido groups can be converted to dimethylammonium ions of the corresponding phosphates without rearrangements involving the P-0-P linkages, when branching groups are absent or present in only small amounts. This is probably attributable to a combination of a slow rate of P-n' scission with a considerably slower rate of P-0-P scission in water a t room temperature or below. The reorganization in carbon tetrachloride t o form rings without concomitant molecular degradation indicates that rings are favored when the reorganizing molecules are separated by 0 0 0 molecules of an inert solvent. This is in accord I 1 I [(CH3)2iT]?P-O-P(OC~H~)2 2ClP[X(CH3)2]2--f with the theory of ring formation developed by 0 organic chemists. It, therefore, appears that the 0 0 I production of rings during the hydrolysis of longchain phosphates is a phenomenon which is separable from the degradation process. I n other words, the first step in path 3 in the hydrolysis 0 scheme presented by McCullough, Van Wazer If the reaction proceeded as written, 75y0 of the and Griffith" is probably a simple structural rephosphorus would have been present as end groups organization step not involving reaction with the and 25y0 as branches. Instead, n.m.r. showed water molecules. that the reaction product consists of the reorganiAcknowledgment.-We wish to thank Dr. L. C. zation-equilibrium mixture of 1% ortho, 48y0 D. Groenweghe for equations 4 and 5 of this paper (20) J. R. Van Wazer, THISJ O U R N A L , 78, 5709 (1956). Also see and the ideas underlying them. H , H . Jaff6, J . Inorg. Nuclear Chem., 4, 372 (1957).
quite closely. This means that factors other than charge difference between building units can play an important role in determining the values of the structural-unit-reorganization equilibria. As will be indicated in the discussion of Paper XI in this series, change in the degree of a-bonding when going from one building unit to anotherz0 and K z = may well be the cause of K1 = 5 X 2.5 X instead of K , = K z = 0.333. I n this system, branches are not present in appreciable amounts until R- blue in about three to five minutes and blue crystals precipitated. The crystals were rernoved by filtration. washed with benzene and dried over phosphorus pentoxide. Care was taken t o exclude atmospheric moisture, as tlie coinpound is extremely deliquescent. T h e yield was 97( . -4nal. Calcd. for { X [ O S ( C H , ' ~ , ][h?CII]: G} C , 19.80; H , 4.98. Found: C, 19.85; H , 1.96. dcetone and ethyl ether precipitate the same compourirl when used in place of benzene. JThen the dimetliylsulfoxide solution of nickel chloride is heated to about XI0, the color changes from light green t ( i intense blue. This color change is completely reversible upon heating and cooling. Maintenance of the temperature a t 50" for 6 hr. resulted in the deposition o f large blue crystals, which were filtered, w;ished with acetnne and dried river phosphorus pentoxide. Anal. Calcd. for (Si[OS[CH?),],}[ SiClr]: C, 19.80; H,1.98. Found: C,19.60; H , 4.96. Trimethylphenylammonium Tetrachloronickelate (II).111 order t o establish the formula as written for the above compiiund, metathesis reactions were perfornictl. Tri( 3 ) 1%'. Hieber and A . Lipp, C ~ P VHZe r. . , 9 2 , 2085 (1959). ( 4 ) V. G u t m a n n and IC. Utvary, Mo,ialsh. C h e w , 90, 701; (1959). (5) I . Lindqvist a n d P. Rinarsson, A r l o Chein. S r n d , 13, 420 I 1959). (6) E. L. hfuetterties, THISJ O U R X A L , 82, 1082 (1Yf;O). (7) S o x ADDEDI N Pn0oF.-Subsequent to the acceptance uf this paper a n article h y F. A . Cotton and R . Francis, THISJ o i i n K A L , 82, 2986 (1960). o n the preparation and properties of some of these compounds has appeared.
methylpheriylammonium nitrate (0.014 moles) in 50 nil. of absolute ethanol was mixed with a n ethanolic solution containing 0.007 moles of [Ni(DMS0)6] [SiCld]. A blue powder precipitated upon vacuum removal of three-fourths of the ethanol. Two recrystallizations from absolute ethanol produced the pure product. Anal. Calcd. for (C9H14N)2XiC14: C, 45.71; H, 5.97; N,5.92. Found: C,45.52; H , 5.97; S , 6 . 1 6 . Hexakis-(dimethylsulfoxide)-nickel(I1)Tetraphenylborate.-One gram of [Ni(os(cH$)l)6][Xicld] was dissolved in absolute ethanol and added t o an ethanolic solution of sodium tetraphenylborate. After the addition of excess ether the green precipitate which forms was filtered off and recrystallized three times from absolute ethanol. The resultant light green needles are slightly hygroscopic. Anal. Calcd. for ( S i [OS(CH,)2]8} [B(csHj)q]a: c , 61.80; H, 6.57. Found: C, 62.13; H , 6.82. Hexakis-(dimethylsulfoxide)-cobalt(I1) Tetrachlorocobaltate (II).-Twenty grams of anhydrous cobalt(I1) chloride was dissolved in i25 ml. of dimethylsulfoxide b y warming the solution t o 50 . -4fter stirring the solution for 10 hr. with a magnetic stirrer, a hygroscopic blue powder precipitated upon the addition of 300 ml. of ethyl acetate. LVashing with anhydrous ethyl ether and drying over phosphorus pentoxide gave a 96% yield of product. The product was recrystallized twice from a SOYGnitromethane-ethyl acetate mixture. Anal. Calcd. for (Co[OS(CH3)2]8}[CoCId]: C, 19.78; H,4.98. Found: C, 19.25; H , 5 . 2 2 . Trimethylphenylammonium Tetrachlorocobaltate(11).This compound mas produced from [Co(DMSO)c ] [ CoCL ] in 97:; yield by a procedure similar t o that described for the corresponding nickel complex. Anal. Calcd. for (CgH14N)aCoC1q:C, 45.69; H, 5.96; S , 5.92. Found: C,45.73; H , 5.95; S,5.86. Hexakis-(dimethylsulfoxide)-cobalt(I1)Iodide.--;\ solution of 13 g. of anhydrous cobalt chloride in i5 inl. of absolute ethanol was added, with stirring, t o a solution of 30 g. of sodium iodide in 130 ml. of absolute ethanol; the solution was filtered from the precipitated sodium chloride. T o the blue solution 100 g. of dimethylsulfoxide was added with stirring. Upon the addition of 300 ml. of ether a coarsely crystalline precipitate forms immediately. This material was filtered and air-dried (weight 75 g.). The crude compound was purified by three recrystallizations from hot methylene chloride. The pink crystals obtained are rmly slightly deliquescent. Anal. Calcd. for (Co[OS(CH:i)2]s}12: C, 18.41; H, 4.61. Found: C, 18.13; H, 4.80. Hexakis-( dimethylsulfoxide)-cobalt( 11) Tetraiodocobaltate (11).-This compound was prepared by a method identical t o the one used for hexakis(dimetliylsu1foxide)-cobalt(I1) iodide, except 25 g. of dimethylsulfoside was added instead of 100 g. Upon addition o f ether, the compound separates as an oil, which quickly crystallizes with further stirring. The yield was 76% of deep green deliquescent crystals. This product was recrystallized from hot absolute ethanol. A n a l . Calcd. for { c o [ o s ( C H ~ ) ~ CoId]: ]6)[ C, 13.16; H , 3.29. Found: C, 12.88; H , 3.37. Tetrakis-(dimethylsulfoxide)-copper(11) Tetrachlorocuprate (II).-A dark brown solution was obtained by dissolving 6 g . of cupric chloride in 3.5 mi. of dimethylsulfoxide. After stirring for twenty minutes a light green slurry formed. The slurry was stirred for 2 hr., benzene added t o complete precipitation, the solid was filtered and mashed with anhydrous ether. T h e product was dissolved in warm ethanol and precipitated by adding petroleum ether and cooling t o - j0. Light green flakes are obtained in 91(,5; yield. .4nnl. Calcd. for {Cu[OS(CH3),];][CuCli]: C, lfi.52; H,4.16. Found: C, 16.51; H , 1 . 1 2 . Tetrakis-(dimethylsulfoxide)-copper(I1) Tetrabromocuprate (11).--4 very dark colored solution is obtained when 10 g. of cupric bromide is dissolved in 100 ml. of dimethylsulfoxide. The solution was filtered and excess benzene was added. After vigorous stirring for two minutes yellow crystals precipitated. The product obtained in 9 0 7 ~yield was filtered, washed with ether and dried. The product is slightll- hygroscopic and was recrystallized from ethanol.
TRANSITION METALIONCOMPLEXES OF DIMETHYL SULFOXIDE
Dec. 3, 1960
Anal. Calcd. for ( CU[OS(CH,)Q]~) [CuBrr]: C, 12.65; H,3.19. Found: C, 12.74; H,3.11. Hexakis-( dimethylsulfoxide)-manganese( 11)Tetrachloromanganate (II).-Dimethylsulfoxide was saturated with anhydrous manganese (11) chloride a t 60-70°, filtered, and an equal volume of absolute ethanol was added. The solution deposited large tan-brown crystals after standing for several hours a t room temperature. These were removed by filtration, washed with a 1:4 ethanol-ether mixture and dried in z~acuo. Special care was taken throughout t o exclude moisture, since the compound is extremely deliquescent. Anal. Calcd. for {hfn[OS(C&)2]s}[Mnclk]: c , 20.00; H, 5.00. Found: C, 20.18; H , 5.14. Mercuric Thiocyanate-dimethyl Sulfoxide Complex.Dimethylsulfoxide was saturated with mercuric thiocyanate a t 70-80’. The filtered solution was allowed to stand several hours, whereupon large colorless crystals are deposited. These were removed and dried. Anal. Calcd. for H ~ ( S C S ) Y ~ ( C H ~ ) ~C,S O15.22; : H, 2.54; 3,5.92. Found: C, 15.39; H , 2.53; h-, 5.89. Though the stoichiometry is well established the structure of this complex is yet unknown.
TABLE I SPECTRA OF COMPLEXES IS X-ISIBLE REGIONIN AXE SOLUTIOS A,
imal
{ M ~ [ O S ( C H B ) I ] G J [ M ~442 C ~ ~ ] 3.10 428 3.91 371 12.35
{ CO[OS(C H B )6~] ][ COCII]
668 386 [(CH3)aSC6Hi]?[COCI4] 693 666 635 { CO [os(CH3h16 1 1 9 708 670 653 620 371 {Co[OS(CH3)21fi)[CoIi] 665 371 { C U [ O S ( C H B )[CuCL] ~]~} 466 370 { C U [ O S ( C H I ) ~ ] ~ ) [ C U B 642 ~,] 371 { Si[OS(CH3)?]8)[ B ( C S H S )660 ~]~ 370
CHsNOz solution
0.08
859 482
,0009
767 659 468
.0005
707 818 826 723 3473
,0005
538 2423
,0003
1164 1520 993 2640
,0007
2.10 10.5
TABLE I1 COMPLEXES I?: NITROMETHANE SOLUTION”
INFRARED SPECTRA O F THE
S=O stretch, cm.-‘
Complex
1045 i,s 1004 i,s 994 i,m 1045 i,m 1001 i,mb { Co[OS(CH3)2Ifi}[COII] 987 i,s { Si[OS(CH3)2]6)[ N ~ C L I 1037 m,br 1000 i,s ( C U [ O S ( C H B ) ?[CuClrl I~} 1042 m,br 1014 m,br (Poorly defined) 987 i,s { CU[OS(CH~)PII} [CuBrrl 1030-1037 (shoulder) 989 i,s The first symbol refers t o the band intensity: i, intense; m, medium; The second symbol refers t o band width: s, sharp; m, medium; br, broad; v, very. Frequency not NITROMETH- accurate because of overlap.
Molarity of Complex ion
BO15
.(IO08 .05
Discussion When the metal halides employed in this research are dissolved in the solvent dimethylsulfoxide, interaction between the solvent and metal ion occur. Solid compounds containing coordinated dimethylsulfoxide and the tetrahalometalate anion are obtained when the metals are precipitated from solution. These structures are supported by elemental analyses and examination of the visible spectra of the compounds in solution. In addition, metathesis reactions were carried out to further support the assigned structure. Trimethylphenylammonium tetrachloronickelate (11) and hexakis-(dimethylsulfoxide)-nickel(I1) tetraphenylborate were obtained from the KiCl?-dimethylsulfoxide complex. Trimethylphenylammonium tetrachlorocobaltate(11)was obtained in 9iycyield from the corresponding cobalt complex.
(CH3)zSO { Mn [OS(CH3)216) [MnCLI { CO[OS(CHB)*I~) [COCIII (C~[OS(CHB)~]G}I?
INFRARED SPECTRAOF
TABLE I11 COMPLEXES I N TUJOL MULL^
THE
S=O stretch, cm
Complex
-1
{ Co[OS(CH3)216)[CoClal { C ~ ( O S ( C H B ) ~1 2] G } ( Co[OS(CH3)2]6)[cOI41 { S ~ [ O S ( C H B ) [NiCL] Z]~)
1002 i,s 992 i,s 987 i,s 992 i,m f r’;i[OS(CH3)216)[ B ( C G H S ) ~ I Z 1000 i,s { Cu[OS(CHs)214}[CUCL] 1028 i,vs 995 i,vs 985 m,vs 1027 i,vs { Cu[OS(CH3)214}[CuBrc] 992 i,vs 982 m,vs Hg(SCn’)2 2( CH9)zSO 1027 i,s The first symbol refers to the band intensity: i, intense; m, medium; The second symbol refers to band width; s, sharp; m, medium; br, broad; v, very.
The complexes are decomposed immediately when placed in water. The complexes of NiC12, CoC12, HgClz and LInCl, are very hygroscopic, while the CuC12 complex is not affected on standing in air for three to four days. The nature of the species in solution is more complex. It appears that sulfoxide and chloride have coordinating abilities that enable competition between the two species; chloride being a slightly better coordinator under the conditions studied. This leads to equilibria which are demonstrated by nickel(I1) chloride solutions. The color of [Ni(D;lISO)s]++cation is a pale green as demonstrated by the color of its tetraphenylborate salt. The color of the alkyl ammonium tetrachloronickelates (11) are an intense blue. When nickel chloride is dissolved in dimethylsulfoxide a light green solution is obtained. When the temperature is raised or a low dielectric constant solvent is added, an intense blue color develops. This suggests the equilibria [xi(DhfSO)6]+ + -f yc1-(sOlv) [Ni(DMSO),Cly]2-~
+ c1 J [NiC14]=
+ (6 - x)DMSO
-Cl-
+ x DMSO
(1)
6016
DEVON iy. YfEEK, DARELK.
STRAUB AND
A dilution of sulfoxide, or a decrease in the dielectric constant of the solvent, shifts the above equilibria to the right. The change in color with temperature is reversible. The formation of XiC14a t elevated temperatures may be due to decreased solvation of chloride ion or to a difference in the heat and entropy of formation of the chloro and sulfoxide complexes such that a plot of log K fus, 1/T for the chloro tetrahedral complex crosses that of the octahedral sulfoxide complex. I t is not necessary that the curves actually cross, for in view of the high Emax for NiCld they need only approach each other. The visible and infrared spectra of solutions of these complexes gives additional support to the proposed equilibria in solution. The visible spectra are similar in shape to those reported by Gill and Nyholm8 for the corresponding alkylammonium tetrahalometalates. However, the Amax and Emax values are different and the peaks are often not as well resolved. These differences cannot be attributed to absorptions by the six-coordinate cations which are present in our compounds but not in the ammonium salts, for in general the emax values for octahedral ions are very small* as demonstrated by our result with [Ni(D&fSO)6] [B(C6&)4]2. The spectra must arise from the presence of other four-coordinate species of the general formula M[B4-xClt]+2--. where B = solvent or dimethylsulfoxide. There is evidence that such equilibria exist in the tetrahalo complexes reported by Gill and Nyholm. Even with halide-metal ion ratios of four to one these authors often observed a change in the spectra upon the addition of excess halide. In solutions of [Co(DMSO)6][CoCL] a similar change occurs upon the addition of chloride ion. The absorption becomes more intense and the peaks are more clearly resolved. The A, and emax values calculated for CoC14= in this solution containing 4 moles of added chloride ion per mole of complex are identical with those of [C~H,N(CH,),],[COC~,].Thus all of the cobalt is converted to tetrachlorocobaltate and the dimethylsulfoxide is displaced. X similar result is obtained when excess chloride or bromide is added to solutions of the dimethylsulfoxide complexes of copper. The infrared spectra of nitromethane solutions of our complexes supports the proposed equilibria and furnishes evidence that sulfoxide coordinates through the oxygen. I n free dimethylsulfoxide, the S-0 stretching frequency occurs a t 1045 cm.-'. I n all of the complexes studied in this research, this absorption is shifted to lower frequency indicating coordination through oxygen. The in(8) N. S. Gill and R.
s.Nyholm, J . Chenz. Soc., 3997 (1959).
RUSSELLs. DRAG0
Vol. 82
frared spectrum of [cO(D?dso)6][coc14] indicates no free dimethylsulfoxide in nitromethane solution. However, when chloride is added, free dimethylsulfoxide is observed, consistent with the conversion of all of the cobalt to CoCI4-. The above equilibrium between halide and dimethylsulfoxide is nicely demonstrated by the iodo and tetraiodocobaltate complexes of hexakis(dimethylsulfoxide) cobalt(I1). Iodide is a poorer coordinating agent than chloride, and in the presence of a large excess of sulfoxide all of the cobalt is coordinated by sulfoxide. When sulfoxide is not present in excess, the iodide competes effectively with sulfoxide, and the hexakis-(dimethylsulfoxide)-cobalt(11) tetraiodocobaltate(I1) is formed along with the iodide. Stoichiometric amounts of sulfoxide results in the formation of [Co(DI\IIS0)6][ C O I ~ ] .The infrared spectrum of a Nujol mull of [CO(Dh~SO)6]Izindicates all the sulfoxide is coordinated. When the infrared spectrum of this complex is examined in nitromethane solution, an uncomplexed sulfoxide peak is observed, and the presence of tetraiodocobaltate is indicated by the visible spectrum, supporting an equilibrium of the type 2[co(DhfSO)~]I% [ C O ( D h f S 0 ) 6 []C O I d ]
+ 6DAISO
(2)
The dissolution of [ c o (DRISO)6]12 in nitromethane is accompanied by a visual change in color from pink to the characteristic blue-green color of the tetraiodocobaltate ion. The frequency shift of the sulfoxide upon coordination should be proportional to the strength of the metal-oxygen bond. It thus appears from an examination of the spectra in nitromethane solution that cobalt and copper are roughly comparable in their coordinating ability toward sulfoxide, while manganese and nickel may be weaker and mercury the weakest. The colors of the solid complexes of copper are surprising in that they are different from the colors of the corresponding alkylammonium tetrahalocuprates. Though there is definite evidence for the existence of CuX4= in solution, the structure of the solid is not known with certainty. The structure of the mercury complex is also in doubt because the insolubility of this substance and lack of color made investigation difficult. Acknowledgments.-The authors would like t o acknowledge the financial assistance of the Atomic Energy Commission (Contract No. AT(11-1)758) which made the research possible. Thanks are also due to Mr. Nemeth and staff of the University hlicroanalytical Laboratory.
