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Hydrido and halogenohydrido complexes of rhenium(III)
J. ilaorg, nucl. Chem. 1967, Vol. 29, pp. 1433 to 1439. Pergamon Press Ltd. Printed in Northern Ireland
HYDRIDO A N D HALOGENOHYDRIDO COMPLEXES OF RHENIUM(III) M. FRENI, R. DEMICHELIS a n d D. GIUSTO Centro Nazionale di Chimica del C.N.R., l'Istituto di Chimica Generale dell'Universit~t di Milano
(First received 20 July 1966; in revbed form 3 January 1967) Abstract--Some new complex hydrides of rhenium are described: ReH3(DPE)(PPh3)~ (I), ReHa(DPE)~(II), ReH2(PPha)3(DPE)I (V) and ReH~(DPE)2X (V'I), where Ph = Cells, DPE = (C6Hs)2PCH2----CH2P(CeHs)2,X = C1, Br, I. The first two behave like bases, because they react with acids to give the cations ReH4(PPhs)z(DPE)+(III) and ReH~(DPE)2+ (IV) respectively. No evolution of hydrogen is observed by reaction with iodine. Their i.r. and NMR spectra are given. INTRODUCTION COMPLEX r h e n i u m hydrides are k n o w n with ~r-cyclopentadienyl group, (1) triphenylp h o s p h i n e t2) a n d c a r b o n m o n o x i d e ta~ as ligands. I n this paper we report o n the complex r h e n i u m hydrides with 1:2-bis-diphenylp h o s p h i n o e t h a n e ( D P E ) as a ligand, which have been obtained, o n CHATT'S suggestion, t4) by a s u b s t i t u t i o n reaction n a m e l y by treating the already k n o w n r h e n i u m hydrides i n particular ReHs(PPha)3,t2~ with D P E . EXPERIMENTAL
Apparatus NMR spectra were recorded on a Perkin-Elmer model R-10, instrument at 60 Mc/s, or Varian HA-100, instrument at 100 Me/s, by using carbon disulphide, deuteroacetone and deuterobenzene saturated solutions, with TMS as internal reference. The measurements were made at 37°C. The data and conditions of measurements are given in Table 1. I.R. spectra were recorded on a Perkin-Elmer, model-237, Infracord spectrometer (Table'2). Molecular weights were taken on a Meehrolab model 301-A osmometer in benzene or in chloroform solution. Dipole moments were determined by the approximate method of Jensen from dielectric constant measurements on 10-1-10-8 M benzene solutions with Dipolmeter DM-01 and cell DLF-2 (Wissenschaftlich Technische Werkst~itten of Weilheim/Oberbayern). Magnetic susceptibilities were measured on a Gouy balance at room temperature.
Rhenium analysis Rhenium was determined as tetraphenylarsonium perrhenate, after treatment in Carius tube with nitric acid. Trihydridobis(triphenylphosphine)1; 2-bis-diphenylphosphinoethanerhenium (Ill). (I). ( I) A mixture of 3 g of ReHs(PPha)a and 2"5 g of DPE (molar ratio 1 : 2) was refluxed in 50 ml of benzene for 48 hr. The resulting yellow solution was faltered hot, and, on addition of 100 ml ethanol, yellow crystals separated (2"3 g; yield, 7070). (Found: C, 66.9; H, 5.53; P, 11.4; Re, 17.0. Cale. for CsaH6~P4Re: C, 67"2; H, 5-13; P, 11"2; Re, 16.8.) The compound is soluble in benzene, carbon disulphide; insoluble in ethanol, hexane. c1~M. L. H. GREEN,L. PRATTand G. WiLkINSON, Y. chem. Soc. 3916 (1958). ~ L. MALATESTA,M. FREr,rt and V. VALE~, Gazz. chim. ital. 94, 1278 (1964). ~8~M. F~a~a, V. VALEr~ and D. GIUSTO,J. inorg, nucl. Chem. 27, 755 (1965). ~4~j. CnATT,J. D. GARrORXH,N. P. Jorr~soN and G. A. RowE, J. chem. Soc. 601 (1964). 1433
M. FRENI, R. DEMICHELISand D. GIUSTO
1434
TABLE 1
No. I
II
III
IV
V
VI
Compound ReHs(PPh3)z(DPE)*
ReHa(DPE)zI"
ReH~(PPh~)z(DPE)+t
ReH~(DPE)s+~
ReH2(PPh3),(DPE)I'J"
ReH2(DPE)~CI§
ReHI(DPE)IBr
ReH~(DPE)2I
Proton resonance ~-
Relative intensity
Fine structure
Coupling constant
3"15 8 16"27 16"75
50 4 1 2
multiplet doublet singlet quintet
C~Hs CH2 Re-H
2.95 8 17.97
40 2 3
multiplet multiplet quintet
C6H6 CH~ Re-H
Jr-a = 17
3.02 7.42 13-88
25 2 2
multiplet doublet quintet
C6H5 CHz Re-H
dP-~t = 22-1
2.7 7.64 15.34
10 1 1
multiplet muitiplet quintet
CeH~ CHs Re-H
Jr-a = 19"9
3 8 15.0
25 2 1
multiplet multiplet quintet
C6H5 CH~ Re - H
JP-a = 26
2.9 8 17.9 2-9 8 20 2.9 8 21.6
20 2 1 20 2 1 20 2 1
multiplet multiplet quintet multiplet multiplet quintet multiplet multiplet quintet
CoHs CH~ Re-H C6H5 CH~ Re-H C6H5 CH2 Re-H
(c/s)
Assignment
drr_a = 10 Jv-n = 24,
JP-a = 14.4
Jr-a = 16
Jr_rT = 24
* At 100 Me/s, in CSv t At 60 Me/s, in CS~. At 100 Me/s, in deuteroacetone. § At 60 Me/s, in deuterobenzene. TABLE2 No.
Compound
vze_a (cm-1)
~Re-a (cm-1)
I II III IV V VI
ReHs(PPhs)2(DPE) ReHs(DPE)s [ReH,(PPhs),fDPE)]C1 [ReH,(DPE)2]C1 ReHz(PPh3)2(DPE)I ReH~(DPE)2C1 ReH2(DPE)~Br ReH~(DPE)~I
1960-1900-1820(w) 1860(s) 1970(vw) 1950(vw) 2040(w)-2000(m) 2040(vw)-2020(vw) 2010(vw)-2030(vw) 2050(vw)
840 ? 850? 850 ? 850? 890 ?
Hydrido and halogenohydrido complexes of rhenium(III)
1435
(2) 0.200 g of compound (III) were dissolved in 10 ml of ethanol and treated with 0.1 ml of ethanolic solution of NaOH 2 M (molar ratio 1:1). (Found: C, 67.9; H, 5.33.) On standing for 48 hr, yellow crystals separated (0.150 g; yield, 78 ~o). Tetrahydridobis( triphenylphosphine) l ;2-bisdiphenylphosphinoethanerheniurn chloride (liD. 0.418 g of the compound (I) were dissolved in 50 ml of benzene and treated drop by drop with a benzenie solution of hydrogen chloride until the solution was discoloured. On standing, white crystals separated (0.321 g; yield, 74~o). (Found: C, 64.2; H, 5.35; Re, 16.4; C1, 3.5. Calc. for C6~HssC1P4Re: C, 64-5; H, 4-98; CI, 3-09; Re, 16.2.) The compound is soluble in ethanol, acetone, chloroform; insoluble in benzene and hexane. Tetrahydridobis( triphenylphosphine ) l ;2-bis-diphenylphosphinoethanerhenium perchlorate. (1) An ethanolic solution of 1 g of the compound (III) in 50 ml of ethanol was treated with a solution of NaC104 in 10 ml of ethanol. White crystals separated (0.99 g, yield, 94~o). (Found: C, 60"41; H, 4"54; C1, 3"07; Re, 16.00. Calc for C6~H~sC104P4Re: C, 61.4; H, 4"80; C1, 2'93; Re, 15.4.) The compound is soluble in acetone, hot ethanol, chloroform; insoluble in benzene, hexane. (2) 0.300 g of the compound (I) were dissolved in 40 ml of benzene and treated drop by drop with an ethanolie solution of perchloric acid until the solution was discoloured. On standing, white crystals separated (0-200 g; yield, 62Yo). (Found: C, 61.7; H, 4.90.)
Tetrahydridobis(triphenylphosphine)l;2-bis-diphenylphosphinoethanerhenium tetraphenylborate. An ethanolic solution of 0.2 g of the compound (III) in 40 ml of ethanol was treated with a solution of 0.06 g of NaB(C6Hs)4 in 10 ml of ethanol (molar ratio 1:1). White crystals separated (0.22 g; yield, 90~o). (Found: C, 71.0; H, 5.16; Calc. for CseHTsBP4Re: C,72"2; H, 5.45.) The compound is soluble in acetone, nitrobenzene, chloroform; insoluble in benzene, ethanol, hexane. Tetrahydridobis(triphenylphosphine)l ;2-bisdiphenylphosphinoethanerhenium iodide. 0-214 g of the compound (I) were dissolved in 25 ml of benzene and treated drop by drop with a benzenic solution of hydrogen iodide 0.02 N until the solution was discoloured (25 ml). On standing white crystals separated (0.058g; yield, 24~o). (Found: C, 59.6; H, 4"9; Re, 15"5; I, 10"5. Calc. for Ce~HsslP4Re: C, 60"0; H, 4"68; Re, 15"0; I, 10"3.) The compound is soluble in ethanol, acetone, chloroform; insoluble in benzene, hexane. Dihydridoiodobis(triphenylphosphine)l ;2-bisdiphenylphosphinoethanerhenium (III). (V). 0.200 g of the compound (I) were dissolved in 25 ml of benzene and dropped in 25 ml of an ethanolic solution of I~ 0.008 N, by stirring (molar ratio 2:1). Yellow crystals separated (0.073 g; yield, 29 ~). (Found: C, 59.73; H, 4.60. Calc. for C82H~6IP4Re: C, 60.2; H, 4.53.) The compound is insoluble in common organic solvents. Trihydridobis(1 ;2-bisdiphenylphosphinoethane)rhenium (III). (II). (1) A mixture of 0.6 g of ReHs(PPha)3 and 0.6 g of DPE (molar ratio 1:2) was heated in a sealed evacuated tube for 2 hr at 180°. By addition of 8 ml of acetone, yellow crystals separated (0.3 g; yield, 50~). (Found: C, 63.71; H, 4.95; Re, 19.0. Calc. for CszHsxP4Re: C, 63.6; H, 5.18; Re, 18.9.) The compound is soluble in benzene, tetrahydrofuran and carbon disulphide; insoluble in acetone, ethanol, hexane. (2) 0.261 g of compound (IV) was dissolved in 10 ml of ethanol and treated with 1 ml of an ethanolic solution of NaOH 2 M. On standing, yellow crystals separated (0.185 g; yield, 74~o). (Found: C, 62"98; H, 4-98.) Tetrahydridobis(1 ;2-bisdiphenylphosphinoethane)rhenium chloride. (IV). (1) 0.500 g of the compound (II) were dissolved in 50 ml of benzene and treated drop by drop with a benzenie solution of hydrogen chloride until the solution was discoloured. White crystals separated, which recrystallized from acetone and hexane (0.420g; yield, 80~). (Found: C, 60.0; H, 5-09; CI, 3.7; Re, 18.4. Calc. for C52H52C1P4Re: C, 61.1; H, 5.1; CI, 3-5; Re, 18.2.) The compound is soluble in ethanol, acetone, chloroform; insoluble in benzene, hexane. (2) 0"500 g of the compound (II) were dissolved in 100 ml of benzene and treated with 0-5 ml of saturated benzenic solution of chlorine. White crystals separated (0.250 g; yield, 48 ~ ) and the yellow solution was treated as below. (Found: C, 60-5; H, 4.95.) Tetrahydridobis(1;2-bisdiphenylphosphinoethane)rhenium perchlorate. (1) 0.215 g of the compound (II) were dissolved in 15 ml of benzene and treated with 6 ml of ethanolic solution of HC104 (1 ml of HC104 q- 5 ml of ethanol). White crystals separated, which recrystallized from acetone and hexane (0.134g; yield, 59~). (Found: C, 57.3; H, 4.77; CI 3.07; Calc. for C52Hs~C104P4Re: C, 57.5; H, 4.79; CI, 3-27.)
1436
M. FgE~, R. DEMICHELISand D. GIUSTO
(2) 0"241 g of ReH4(DPE)2C1 and 0.03 g of NaCIO4 (molar ratio 1 : 1) were dissolved in 10 ml of ethanol. White crystals separated (0.208 g; yield, 81 ~). (Found: C, 58.0; H, 5.0.) TetrahydrMobis(1 ;2-bisdiphenylphosphinoethane)rhenium bromide. 0"513 g of the compound (II) were dissolved in 50 ml of benzene and treated with 3.5 ml of benzene solution of bromine 0.15 N (molar ratio 2:1). White crystals separated (0.330 g; yield, 60~). (Found: C, 58"0; H, 5-7; Br, 8.64; Re, 18.0. Calc. for CszHs~BrP4Re: C, 58.5; H, 5.54; Br, 8"53; Re, 17'45.) The compound is soluble in benzene; chloroform; insoluble in ethanol, hexane. Tetrahydridobis( 1 ;2-bisdiphenylphosphinoethane)rhenium iodide. (1) 0'500 g of the compound (II) were dissolved in 50 ml of benzene and treated, drop by drop, with a benzene solution of hydrogen iodide 0.02 N, until the solution was discoloured (25 ml). White crystals separated 0.440 g; yield, 78%). (Found: C, 55.10; H, 4.95. Calc. for C52H52IP4Re: C, 56.10; H, 4.68.) (2) 0.500 g of the compound (II) were dissolved in 50 ml of benzene and treated with 5.5 ml of I2 0.09 N (molar ratio 2:1). White crystals separated (0-283 g; yield, 50~). The yellow solution was treated as below. (Found: C, 56"3; H, 4"75.) Dihydridoiodobis(1;2-bisdiphenylphosphinoethane)rhenium(III). (VI). (1) The yellow solution which was obtained in (2) of the preparation of ReH4fDPE)2I, was evaporated to dryness. Yellow crystals separated, which recrystallized from benzene and ethanol (0.209 g; yield, 37 ~o). (Found: C, 55.9; H, 4.60. Calc. for C~H~0IP4Re: C, 56.2; H, 4-5; I, 11.5.) (2) 0.500 g of the red compound RefDPE)212, suspended in 20 ml of tetrahydrofuran, were treated with 0.200 g of LiA1H4 and heated until the red compound was dissolved. After filtering, 30 ml of ethanol were added to the solution. Yellow crystals separated (0.115 g; yield, 25~o). (Found: C, 56.01; H, 4.60; I, 11.6.) Dihydridochlorobis(1 ;2-bisdiphenylphosphinoethane)rhenium (III). (1) The yellow solution which was obtained in the preparation of [ReH~(DPE)8]C1, was evaporated to dryness. Yellow crystals separated, which recrystallized from benzene and ethanol (0.200 g; yield, 39 ~o). (Found: C, 61.0; H, 5.0. Calc. for C52HsoC1P4Re: C, 61-2; H, 4.90; CI, 3.44). (2) 0.400 g of the yellow compound Re(DPE)2C12, suspended in 20 ml of tetrahydrofuran, were treated with 0.200 g of LiA1H4 and heated until the yellow compound was dissolved. After filtering, 30ml of ethanol were added to the solution. Yellow crystals separated (0.040 g; yield, 10~o). (Found: C, 60.40; H, 5.40; CI, 3.50.) Dihydridobromobis(1 ;2-bisdit~henylphosphinoethane)rhenium (III). (1) The yellow solution which was obtained in the preparation of ReH4(DPE)2Br, was evaporated to dryness. Yellow crystals separated, which recrystallized from benzene and ethanol (0.154 g; yield, 27.6 ~). (Found: C, 58.3; H, 5.40; Calc. for Cs~HsoBrP4Re: C, 58.6; H, 5-32; Br, 7.50; Re, 17.5.) (2) 0.350 g of the yellow compound [ReO2(DPE)2]Br, suspended in 20 ml of tetrahydrofuran, were treated with 0.200 g of LiA1H4 and heated until the yellow compound was dissolved. After filtering, 30 ml of ethanol were added to the solution. Yellow crystals separated (0.040 g; yield, 12~). (Found: C, 58.5; H, 4.5; Br, 7.2; Re, 17.9.) Tetrachloro(l ;2-bisdiphenylphosphinoethane)rhenium (IV). 0"502 g of the compound (I) were dissolved in 100 ml of benzene and treated with 2 ml of a saturated benzenic solution of chlorine. On standing, orange crystals separated which were recrystallized from acetone and hexane (0-218 g; yield, 66~o). (Found: C, 41-61; H, 3-71; CI, 18.8; Re, 26.2. Cale. for CzsH24CI4P~Re: C, 43'0; H, 3"3; C1, 19.6; Re, 25.6.) The compound is soluble in acetone; insoluble in benzene, ethanol, chloroform, hexane. Dichlorobis(1 ;2-bisdiphenylphosphinoethane)rhenium chloride. (I) 0"410 g of the compound (II) were dissolved in 40 ml of benzene and treated with an excess of a saturated solution of chlorine (2ml). Yellow crystals separated (0-300g; yield, 76~o). (Found: C, 58.5; H, 5.04; CI, 10"5; Re, 18.1. Cale. for Cs~H48ClsP~Re: C, 57.3; H, 4.4; CI, 9"78; Re, 17.20.) (2) 0-200 g of [ReH4fDPE)2]CI were dissolved in 10 ml of ethanol and treated with an excess of a saturated solution of chlorine (1 ml). Yellow crystals separated (0.180 g; yield, 85~o). (Found: C, 58-0; H, 4.5.) Diiodobis(1 ;2-bisdiphenylphosphinoethane)rhenium iodide. 0"059 g of ReH2fDPE)aI were dissolved in 6 ml of benzene and treated with 2"4 ml of a benzene solution of iodine 0.092 N (molar ratio 1 : 4). Brown crystals separated (0.040 g; yield, 54 ~). (Found: C, 45.41 ; H, 3.95. Calc. for Cs~H4813P4Re: C, 45'8; H, 3-52.)
Hydrido and halogenohydrido complexesof rhenium(Ill)
1437
RESULTS AND DISCUSSION The substitution of triphenylphosphine (PPha) by DPE can be carded out by the use of a large excess of substituting ligand either in benzene solution or without a solvent. Depending on the conditions, two yellow hydrides can be isolated, ReH 3(PPh3)2(DPE) (I) and ReHa(DPE)~ (II). Both compounds contain the same number of hydridic hydrogen atoms and appear to be monomeric non-electrolytes diamagnetic both in the solid state and in benzene solution: the rhenium appears to be heptacoordinated as in ReHa(PPha)4. t2~ Reactions. Unlike the complex rhenium hydrides with triphenylphosphine, neither compounds (I) or (II) evolve hydrogen when treated with acids and actually show basic character. They react with acids, adding one proton each, yielding white diamagnetic salts in which the cations [ReH4(PPha)2(DPE)]+ (lid and [ReH4(DPE2)]+ (IV) are present. When the salts of these cations with anions such as chloride, iodide, perchlorate are treated with alkali, the reverse reaction takes place which leads to the starting hydrides (I) and (II), according to the following schemes: +H+
ReHa(PPh3)z(DPE) ~
~ [ReHa(PPha)2(DPE)]+ +OH-
+H +
ReH~(DPE)2
.~
> [ReH4(DPE)~]+ +OH-
It is interesting to note that compounds (I) and (II), unlike the other rhenium hydrides, do not evolve gas when treated with halogens in benzene solution; in contrast such reactions led to the formation of halogenocomplexes of rhenium which still contain hydrogen atoms directly bound to the metal: 2 ReH3(PPha)~(DPE) ÷ X2 ~ [ReH4(PPh3)~(DPE)] X + ReH2(PPha)2(DPE)X 2 ReH3(DPE)~ + X2 --~ [ReH4(DPE)2] X + ReH2(DPE)2X
(V) (VI)
Since the hydrides (I) and (II) are monomeric, it is suggested that this reaction takes place stepwise: the first step, in which hydrogen halide and halogenohydrides (V) and (VI) are formed, is followed by another in which the unreacted bases (II) and (I) combine with the hydrogen halide to give the halides of cations (IV) and (III). The dihydridohalide (VI) has also been obtained by the reduction of Re(DPE)2X2ts~ and [ReO2(DPE)2] X t6~ (X ---- C1, Br, I) with LiA1H4. The Re-H bonds in compound (VI) behave peculiarly, as no hydrogen is evolved on heating with acids or iodine. With iodine the reaction appears to follow the path: ReH~(DPE)zI + 2 12 --o.2 HI + [Re(DPE)2I~]I in which four equivalents of iodine react with 1 mole of ReH2(DPE)2I, giving two equivalents of hydriodic acid. The dihydridohalides are stable at room temperature to acids: they do not show basic character and are recovered unchanged from aqueous-acid solutions. The hydride (I) reacts with chlorine yielding Re(DPE)CI~ (VII), and triphenylphosphineoxide. The hydride (II) is converted by chlorine into the already known salt [Re(DPE)2C12]C1,tS~ without loss of ligand. ts~j. CHArt and G. A. RowE,J. chem. Soc. 4019 (1962). ~6~(a) F. NYMANand G. A. STERN,Proc. 8th Int. Conf. Coord. Chem. Wien (1964); (b) M. FR~I, D. GIUSTOand P. ROMm,Gazz. chim. ital. (in press).
1438
M. F~r~,
R. DEmcrmus
and D. G~STO
LR. spectra. The main evidence of the presence of hydrogen atoms bound to the metal is given by the i.r. and N M R spectra. The i.r. spectrum of compound (I) both in Nujol and in benzene solution has three weak bands in the metal-hydrogen stretching region, two at 1960 and 1900 cm-1, the third still weaker at 1820 cm -1. In contrast only one very strong band appears in the same region of the i.r. spectrum of compound (II). No absorption band assignable to Re-H bending frequencies was observed in the expected region owing to the presence of a very broad band due to the ligand. As with the rhenium hydrides previously reported, t~) we were not able to prepare deuterated compounds, so that the assignment of the absorption bands to Re-H stretching vibrations is not quite conclusive. On addition, since the bands in the i.r. spectrum of compound (I) are broad and weak, any structural interpretation based upon them is tentative. TABLE 3
No. I III
V II IV
VI
VII
Compound ReHs(PPhs)2(DPE) [ReH~(PPhs)~(DPE)]CI [ReH~(PPhs)2(DPE)]CIO 4 [ReH4(PPhs)~(DPE)]I [ReH4(PPhs)z(DPE)]BPh4 ReH2(PPhs)z(DPE)I ReHs(DPE)z [ReH4(DPE)2]CI [ReH4(DPE)2]C104 [ReH4(DPE)2]I [ReH4(DPE)~]Br ReH2(DPE)2CI ReHz(DPE)2Br ReH2(DPE)zI Re(DPE)C14 [Re(DPE)2Clz]C1
Colour
M.p. (°C)
yellow white white white white yellow yellow white white white white yellow yellow yellow orange yellow
164 170 178 190 140 135 202 172 180 158 162 172 dee 178 185 dec 245 240
A~* ( ~ - 1 c m 2) -113 104 110 93 --129.0 118.3 127.4 128"2 ----126
Mol. wt. Calc. Found 1111
1237 985
1019.5 1064 1111 726
1090~: ----1123 +* 1110t ----902:~ 1006~: 1120~: 705:~ --
Z ~ . 106
5800 6000
p(D) 8.28 -----4.95 ----4.20 4.43 4-89 ---
* I n a c e t o n e solution. t I n b e n z e n e solution. I n c h l o r o f o r m solution.
All that can be said is that while the i.r. spectrum of compound (I) is in agreement with low molecular symmetry, the presence of a single strong Re-H absorption band in the i.r. spectrum of compound (II) indicates a more highly symmetrical arrangement of hydrogen atoms. Unfortunately the broad and very weak bands of the i.r. spectrum of the cations (III) and (IV) are hardly sufficient to confirm the existence of the rhenium-hydrogen bonds (Table 3). The same is true for the halogenohydrides ReH2(DPE)~X (X = C1, Br, I), which show only very weak bands at about 2000 cm-1. N M R spectra. Both the stoichiometry and the hydridic nature of compounds (I) and (II) and their derivatives (III), (IV), (V) and (VI) have been unequivocally confirmed by the N M R data, measured in CS2, acetone or chloroform solution at 60 or 100 Mc/sec (Table 1). The N M R spectrum of the compound(I) shows two resonance patterns at r = 16"27 and 16.75 respectively, indicating that the hydrogen nuclei are non-equivalent. The resonance pattern at 16.75 r is due to two equivalent hydrogen nuclei and it consists of a quintet caused by the presence of four equivalent phosphorus nuclei (JP-a = 24 c/s), which is further split by mutual coupling with the third hydrogen atom
Hydrido and halogenohydridocomplexesof rhenium(III)
1439
(Ja-2H = 10 C/S). The resonance at 16.27 ~- does not show coupling with the phosphorus atoms; it consists of a band which is not clearly resolved owing to the low solubility of the compound and the fact that the two resonance patterns are very close together. All the other compounds gave a single symmetrical resonance pattern consisting of a quintet from the coupling of the hydrogen nuclei with four equivalent phosphorus atoms. The chemical shift of the hydridic hydrogens in the halogenohydride complexes is larger than in the other rhenium hydrides: this is further evidence for the anionic character of the hydride anion in these compounds. It is noteworthy that in the compounds of type (VI), rhenium has a coordination number of seven, while the corresponding halogeno complexes are electrolytes in which rhenium is hexacoordinated in the cation. Since the chemical shift of the halogenohydrides in series decrease I > Br > CI, it seems reasonable to assume that the hydridic character of the hydrogen increases in reverse order. Finally, the observed dipole moments of about 5 D for these halogenocompounds is in agreement with a pentagonal bipyramidal structure (calculated value, 6.4 D), with the two hydrogen atoms at the apices. The compounds described in this paper are all crystalline, but only with compound (I) has it been possible to carry out an X-ray structural study, the results of which will soon be published elsewhere.
HYDRIDO A N D HALOGENOHYDRIDO COMPLEXES OF RHENIUM(III) M. FRENI, R. DEMICHELIS a n d D. GIUSTO Centro Nazionale di Chimica del C.N.R., l'Istituto di Chimica Generale dell'Universit~t di Milano
(First received 20 July 1966; in revbed form 3 January 1967) Abstract--Some new complex hydrides of rhenium are described: ReH3(DPE)(PPh3)~ (I), ReHa(DPE)~(II), ReH2(PPha)3(DPE)I (V) and ReH~(DPE)2X (V'I), where Ph = Cells, DPE = (C6Hs)2PCH2----CH2P(CeHs)2,X = C1, Br, I. The first two behave like bases, because they react with acids to give the cations ReH4(PPhs)z(DPE)+(III) and ReH~(DPE)2+ (IV) respectively. No evolution of hydrogen is observed by reaction with iodine. Their i.r. and NMR spectra are given. INTRODUCTION COMPLEX r h e n i u m hydrides are k n o w n with ~r-cyclopentadienyl group, (1) triphenylp h o s p h i n e t2) a n d c a r b o n m o n o x i d e ta~ as ligands. I n this paper we report o n the complex r h e n i u m hydrides with 1:2-bis-diphenylp h o s p h i n o e t h a n e ( D P E ) as a ligand, which have been obtained, o n CHATT'S suggestion, t4) by a s u b s t i t u t i o n reaction n a m e l y by treating the already k n o w n r h e n i u m hydrides i n particular ReHs(PPha)3,t2~ with D P E . EXPERIMENTAL
Apparatus NMR spectra were recorded on a Perkin-Elmer model R-10, instrument at 60 Mc/s, or Varian HA-100, instrument at 100 Me/s, by using carbon disulphide, deuteroacetone and deuterobenzene saturated solutions, with TMS as internal reference. The measurements were made at 37°C. The data and conditions of measurements are given in Table 1. I.R. spectra were recorded on a Perkin-Elmer, model-237, Infracord spectrometer (Table'2). Molecular weights were taken on a Meehrolab model 301-A osmometer in benzene or in chloroform solution. Dipole moments were determined by the approximate method of Jensen from dielectric constant measurements on 10-1-10-8 M benzene solutions with Dipolmeter DM-01 and cell DLF-2 (Wissenschaftlich Technische Werkst~itten of Weilheim/Oberbayern). Magnetic susceptibilities were measured on a Gouy balance at room temperature.
Rhenium analysis Rhenium was determined as tetraphenylarsonium perrhenate, after treatment in Carius tube with nitric acid. Trihydridobis(triphenylphosphine)1; 2-bis-diphenylphosphinoethanerhenium (Ill). (I). ( I) A mixture of 3 g of ReHs(PPha)a and 2"5 g of DPE (molar ratio 1 : 2) was refluxed in 50 ml of benzene for 48 hr. The resulting yellow solution was faltered hot, and, on addition of 100 ml ethanol, yellow crystals separated (2"3 g; yield, 7070). (Found: C, 66.9; H, 5.53; P, 11.4; Re, 17.0. Cale. for CsaH6~P4Re: C, 67"2; H, 5-13; P, 11"2; Re, 16.8.) The compound is soluble in benzene, carbon disulphide; insoluble in ethanol, hexane. c1~M. L. H. GREEN,L. PRATTand G. WiLkINSON, Y. chem. Soc. 3916 (1958). ~ L. MALATESTA,M. FREr,rt and V. VALE~, Gazz. chim. ital. 94, 1278 (1964). ~8~M. F~a~a, V. VALEr~ and D. GIUSTO,J. inorg, nucl. Chem. 27, 755 (1965). ~4~j. CnATT,J. D. GARrORXH,N. P. Jorr~soN and G. A. RowE, J. chem. Soc. 601 (1964). 1433
M. FRENI, R. DEMICHELISand D. GIUSTO
1434
TABLE 1
No. I
II
III
IV
V
VI
Compound ReHs(PPh3)z(DPE)*
ReHa(DPE)zI"
ReH~(PPh~)z(DPE)+t
ReH~(DPE)s+~
ReH2(PPh3),(DPE)I'J"
ReH2(DPE)~CI§
ReHI(DPE)IBr
ReH~(DPE)2I
Proton resonance ~-
Relative intensity
Fine structure
Coupling constant
3"15 8 16"27 16"75
50 4 1 2
multiplet doublet singlet quintet
C~Hs CH2 Re-H
2.95 8 17.97
40 2 3
multiplet multiplet quintet
C6H6 CH~ Re-H
Jr-a = 17
3.02 7.42 13-88
25 2 2
multiplet doublet quintet
C6H5 CHz Re-H
dP-~t = 22-1
2.7 7.64 15.34
10 1 1
multiplet muitiplet quintet
CeH~ CHs Re-H
Jr-a = 19"9
3 8 15.0
25 2 1
multiplet multiplet quintet
C6H5 CH~ Re - H
JP-a = 26
2.9 8 17.9 2-9 8 20 2.9 8 21.6
20 2 1 20 2 1 20 2 1
multiplet multiplet quintet multiplet multiplet quintet multiplet multiplet quintet
CoHs CH~ Re-H C6H5 CH~ Re-H C6H5 CH2 Re-H
(c/s)
Assignment
drr_a = 10 Jv-n = 24,
JP-a = 14.4
Jr-a = 16
Jr_rT = 24
* At 100 Me/s, in CSv t At 60 Me/s, in CS~. At 100 Me/s, in deuteroacetone. § At 60 Me/s, in deuterobenzene. TABLE2 No.
Compound
vze_a (cm-1)
~Re-a (cm-1)
I II III IV V VI
ReHs(PPhs)2(DPE) ReHs(DPE)s [ReH,(PPhs),fDPE)]C1 [ReH,(DPE)2]C1 ReHz(PPh3)2(DPE)I ReH~(DPE)2C1 ReH2(DPE)~Br ReH~(DPE)~I
1960-1900-1820(w) 1860(s) 1970(vw) 1950(vw) 2040(w)-2000(m) 2040(vw)-2020(vw) 2010(vw)-2030(vw) 2050(vw)
840 ? 850? 850 ? 850? 890 ?
Hydrido and halogenohydrido complexes of rhenium(III)
1435
(2) 0.200 g of compound (III) were dissolved in 10 ml of ethanol and treated with 0.1 ml of ethanolic solution of NaOH 2 M (molar ratio 1:1). (Found: C, 67.9; H, 5.33.) On standing for 48 hr, yellow crystals separated (0.150 g; yield, 78 ~o). Tetrahydridobis( triphenylphosphine) l ;2-bisdiphenylphosphinoethanerheniurn chloride (liD. 0.418 g of the compound (I) were dissolved in 50 ml of benzene and treated drop by drop with a benzenie solution of hydrogen chloride until the solution was discoloured. On standing, white crystals separated (0.321 g; yield, 74~o). (Found: C, 64.2; H, 5.35; Re, 16.4; C1, 3.5. Calc. for C6~HssC1P4Re: C, 64-5; H, 4-98; CI, 3-09; Re, 16.2.) The compound is soluble in ethanol, acetone, chloroform; insoluble in benzene and hexane. Tetrahydridobis( triphenylphosphine ) l ;2-bis-diphenylphosphinoethanerhenium perchlorate. (1) An ethanolic solution of 1 g of the compound (III) in 50 ml of ethanol was treated with a solution of NaC104 in 10 ml of ethanol. White crystals separated (0.99 g, yield, 94~o). (Found: C, 60"41; H, 4"54; C1, 3"07; Re, 16.00. Calc for C6~H~sC104P4Re: C, 61.4; H, 4"80; C1, 2'93; Re, 15.4.) The compound is soluble in acetone, hot ethanol, chloroform; insoluble in benzene, hexane. (2) 0.300 g of the compound (I) were dissolved in 40 ml of benzene and treated drop by drop with an ethanolie solution of perchloric acid until the solution was discoloured. On standing, white crystals separated (0-200 g; yield, 62Yo). (Found: C, 61.7; H, 4.90.)
Tetrahydridobis(triphenylphosphine)l;2-bis-diphenylphosphinoethanerhenium tetraphenylborate. An ethanolic solution of 0.2 g of the compound (III) in 40 ml of ethanol was treated with a solution of 0.06 g of NaB(C6Hs)4 in 10 ml of ethanol (molar ratio 1:1). White crystals separated (0.22 g; yield, 90~o). (Found: C, 71.0; H, 5.16; Calc. for CseHTsBP4Re: C,72"2; H, 5.45.) The compound is soluble in acetone, nitrobenzene, chloroform; insoluble in benzene, ethanol, hexane. Tetrahydridobis(triphenylphosphine)l ;2-bisdiphenylphosphinoethanerhenium iodide. 0-214 g of the compound (I) were dissolved in 25 ml of benzene and treated drop by drop with a benzenic solution of hydrogen iodide 0.02 N until the solution was discoloured (25 ml). On standing white crystals separated (0.058g; yield, 24~o). (Found: C, 59.6; H, 4"9; Re, 15"5; I, 10"5. Calc. for Ce~HsslP4Re: C, 60"0; H, 4"68; Re, 15"0; I, 10"3.) The compound is soluble in ethanol, acetone, chloroform; insoluble in benzene, hexane. Dihydridoiodobis(triphenylphosphine)l ;2-bisdiphenylphosphinoethanerhenium (III). (V). 0.200 g of the compound (I) were dissolved in 25 ml of benzene and dropped in 25 ml of an ethanolic solution of I~ 0.008 N, by stirring (molar ratio 2:1). Yellow crystals separated (0.073 g; yield, 29 ~). (Found: C, 59.73; H, 4.60. Calc. for C82H~6IP4Re: C, 60.2; H, 4.53.) The compound is insoluble in common organic solvents. Trihydridobis(1 ;2-bisdiphenylphosphinoethane)rhenium (III). (II). (1) A mixture of 0.6 g of ReHs(PPha)3 and 0.6 g of DPE (molar ratio 1:2) was heated in a sealed evacuated tube for 2 hr at 180°. By addition of 8 ml of acetone, yellow crystals separated (0.3 g; yield, 50~). (Found: C, 63.71; H, 4.95; Re, 19.0. Calc. for CszHsxP4Re: C, 63.6; H, 5.18; Re, 18.9.) The compound is soluble in benzene, tetrahydrofuran and carbon disulphide; insoluble in acetone, ethanol, hexane. (2) 0.261 g of compound (IV) was dissolved in 10 ml of ethanol and treated with 1 ml of an ethanolic solution of NaOH 2 M. On standing, yellow crystals separated (0.185 g; yield, 74~o). (Found: C, 62"98; H, 4-98.) Tetrahydridobis(1 ;2-bisdiphenylphosphinoethane)rhenium chloride. (IV). (1) 0.500 g of the compound (II) were dissolved in 50 ml of benzene and treated drop by drop with a benzenie solution of hydrogen chloride until the solution was discoloured. White crystals separated, which recrystallized from acetone and hexane (0.420g; yield, 80~). (Found: C, 60.0; H, 5-09; CI, 3.7; Re, 18.4. Calc. for C52H52C1P4Re: C, 61.1; H, 5.1; CI, 3-5; Re, 18.2.) The compound is soluble in ethanol, acetone, chloroform; insoluble in benzene, hexane. (2) 0"500 g of the compound (II) were dissolved in 100 ml of benzene and treated with 0-5 ml of saturated benzenic solution of chlorine. White crystals separated (0.250 g; yield, 48 ~ ) and the yellow solution was treated as below. (Found: C, 60-5; H, 4.95.) Tetrahydridobis(1;2-bisdiphenylphosphinoethane)rhenium perchlorate. (1) 0.215 g of the compound (II) were dissolved in 15 ml of benzene and treated with 6 ml of ethanolic solution of HC104 (1 ml of HC104 q- 5 ml of ethanol). White crystals separated, which recrystallized from acetone and hexane (0.134g; yield, 59~). (Found: C, 57.3; H, 4.77; CI 3.07; Calc. for C52Hs~C104P4Re: C, 57.5; H, 4.79; CI, 3-27.)
1436
M. FgE~, R. DEMICHELISand D. GIUSTO
(2) 0"241 g of ReH4(DPE)2C1 and 0.03 g of NaCIO4 (molar ratio 1 : 1) were dissolved in 10 ml of ethanol. White crystals separated (0.208 g; yield, 81 ~). (Found: C, 58.0; H, 5.0.) TetrahydrMobis(1 ;2-bisdiphenylphosphinoethane)rhenium bromide. 0"513 g of the compound (II) were dissolved in 50 ml of benzene and treated with 3.5 ml of benzene solution of bromine 0.15 N (molar ratio 2:1). White crystals separated (0.330 g; yield, 60~). (Found: C, 58"0; H, 5-7; Br, 8.64; Re, 18.0. Calc. for CszHs~BrP4Re: C, 58.5; H, 5.54; Br, 8"53; Re, 17'45.) The compound is soluble in benzene; chloroform; insoluble in ethanol, hexane. Tetrahydridobis( 1 ;2-bisdiphenylphosphinoethane)rhenium iodide. (1) 0'500 g of the compound (II) were dissolved in 50 ml of benzene and treated, drop by drop, with a benzene solution of hydrogen iodide 0.02 N, until the solution was discoloured (25 ml). White crystals separated 0.440 g; yield, 78%). (Found: C, 55.10; H, 4.95. Calc. for C52H52IP4Re: C, 56.10; H, 4.68.) (2) 0.500 g of the compound (II) were dissolved in 50 ml of benzene and treated with 5.5 ml of I2 0.09 N (molar ratio 2:1). White crystals separated (0-283 g; yield, 50~). The yellow solution was treated as below. (Found: C, 56"3; H, 4"75.) Dihydridoiodobis(1;2-bisdiphenylphosphinoethane)rhenium(III). (VI). (1) The yellow solution which was obtained in (2) of the preparation of ReH4fDPE)2I, was evaporated to dryness. Yellow crystals separated, which recrystallized from benzene and ethanol (0.209 g; yield, 37 ~o). (Found: C, 55.9; H, 4.60. Calc. for C~H~0IP4Re: C, 56.2; H, 4-5; I, 11.5.) (2) 0.500 g of the red compound RefDPE)212, suspended in 20 ml of tetrahydrofuran, were treated with 0.200 g of LiA1H4 and heated until the red compound was dissolved. After filtering, 30 ml of ethanol were added to the solution. Yellow crystals separated (0.115 g; yield, 25~o). (Found: C, 56.01; H, 4.60; I, 11.6.) Dihydridochlorobis(1 ;2-bisdiphenylphosphinoethane)rhenium (III). (1) The yellow solution which was obtained in the preparation of [ReH~(DPE)8]C1, was evaporated to dryness. Yellow crystals separated, which recrystallized from benzene and ethanol (0.200 g; yield, 39 ~o). (Found: C, 61.0; H, 5.0. Calc. for C52HsoC1P4Re: C, 61-2; H, 4.90; CI, 3.44). (2) 0.400 g of the yellow compound Re(DPE)2C12, suspended in 20 ml of tetrahydrofuran, were treated with 0.200 g of LiA1H4 and heated until the yellow compound was dissolved. After filtering, 30ml of ethanol were added to the solution. Yellow crystals separated (0.040 g; yield, 10~o). (Found: C, 60.40; H, 5.40; CI, 3.50.) Dihydridobromobis(1 ;2-bisdit~henylphosphinoethane)rhenium (III). (1) The yellow solution which was obtained in the preparation of ReH4(DPE)2Br, was evaporated to dryness. Yellow crystals separated, which recrystallized from benzene and ethanol (0.154 g; yield, 27.6 ~). (Found: C, 58.3; H, 5.40; Calc. for Cs~HsoBrP4Re: C, 58.6; H, 5-32; Br, 7.50; Re, 17.5.) (2) 0.350 g of the yellow compound [ReO2(DPE)2]Br, suspended in 20 ml of tetrahydrofuran, were treated with 0.200 g of LiA1H4 and heated until the yellow compound was dissolved. After filtering, 30 ml of ethanol were added to the solution. Yellow crystals separated (0.040 g; yield, 12~). (Found: C, 58.5; H, 4.5; Br, 7.2; Re, 17.9.) Tetrachloro(l ;2-bisdiphenylphosphinoethane)rhenium (IV). 0"502 g of the compound (I) were dissolved in 100 ml of benzene and treated with 2 ml of a saturated benzenic solution of chlorine. On standing, orange crystals separated which were recrystallized from acetone and hexane (0-218 g; yield, 66~o). (Found: C, 41-61; H, 3-71; CI, 18.8; Re, 26.2. Cale. for CzsH24CI4P~Re: C, 43'0; H, 3"3; C1, 19.6; Re, 25.6.) The compound is soluble in acetone; insoluble in benzene, ethanol, chloroform, hexane. Dichlorobis(1 ;2-bisdiphenylphosphinoethane)rhenium chloride. (I) 0"410 g of the compound (II) were dissolved in 40 ml of benzene and treated with an excess of a saturated solution of chlorine (2ml). Yellow crystals separated (0-300g; yield, 76~o). (Found: C, 58.5; H, 5.04; CI, 10"5; Re, 18.1. Cale. for Cs~H48ClsP~Re: C, 57.3; H, 4.4; CI, 9"78; Re, 17.20.) (2) 0-200 g of [ReH4fDPE)2]CI were dissolved in 10 ml of ethanol and treated with an excess of a saturated solution of chlorine (1 ml). Yellow crystals separated (0.180 g; yield, 85~o). (Found: C, 58-0; H, 4.5.) Diiodobis(1 ;2-bisdiphenylphosphinoethane)rhenium iodide. 0"059 g of ReH2fDPE)aI were dissolved in 6 ml of benzene and treated with 2"4 ml of a benzene solution of iodine 0.092 N (molar ratio 1 : 4). Brown crystals separated (0.040 g; yield, 54 ~). (Found: C, 45.41 ; H, 3.95. Calc. for Cs~H4813P4Re: C, 45'8; H, 3-52.)
Hydrido and halogenohydrido complexesof rhenium(Ill)
1437
RESULTS AND DISCUSSION The substitution of triphenylphosphine (PPha) by DPE can be carded out by the use of a large excess of substituting ligand either in benzene solution or without a solvent. Depending on the conditions, two yellow hydrides can be isolated, ReH 3(PPh3)2(DPE) (I) and ReHa(DPE)~ (II). Both compounds contain the same number of hydridic hydrogen atoms and appear to be monomeric non-electrolytes diamagnetic both in the solid state and in benzene solution: the rhenium appears to be heptacoordinated as in ReHa(PPha)4. t2~ Reactions. Unlike the complex rhenium hydrides with triphenylphosphine, neither compounds (I) or (II) evolve hydrogen when treated with acids and actually show basic character. They react with acids, adding one proton each, yielding white diamagnetic salts in which the cations [ReH4(PPha)2(DPE)]+ (lid and [ReH4(DPE2)]+ (IV) are present. When the salts of these cations with anions such as chloride, iodide, perchlorate are treated with alkali, the reverse reaction takes place which leads to the starting hydrides (I) and (II), according to the following schemes: +H+
ReHa(PPh3)z(DPE) ~
~ [ReHa(PPha)2(DPE)]+ +OH-
+H +
ReH~(DPE)2
.~
> [ReH4(DPE)~]+ +OH-
It is interesting to note that compounds (I) and (II), unlike the other rhenium hydrides, do not evolve gas when treated with halogens in benzene solution; in contrast such reactions led to the formation of halogenocomplexes of rhenium which still contain hydrogen atoms directly bound to the metal: 2 ReH3(PPha)~(DPE) ÷ X2 ~ [ReH4(PPh3)~(DPE)] X + ReH2(PPha)2(DPE)X 2 ReH3(DPE)~ + X2 --~ [ReH4(DPE)2] X + ReH2(DPE)2X
(V) (VI)
Since the hydrides (I) and (II) are monomeric, it is suggested that this reaction takes place stepwise: the first step, in which hydrogen halide and halogenohydrides (V) and (VI) are formed, is followed by another in which the unreacted bases (II) and (I) combine with the hydrogen halide to give the halides of cations (IV) and (III). The dihydridohalide (VI) has also been obtained by the reduction of Re(DPE)2X2ts~ and [ReO2(DPE)2] X t6~ (X ---- C1, Br, I) with LiA1H4. The Re-H bonds in compound (VI) behave peculiarly, as no hydrogen is evolved on heating with acids or iodine. With iodine the reaction appears to follow the path: ReH~(DPE)zI + 2 12 --o.2 HI + [Re(DPE)2I~]I in which four equivalents of iodine react with 1 mole of ReH2(DPE)2I, giving two equivalents of hydriodic acid. The dihydridohalides are stable at room temperature to acids: they do not show basic character and are recovered unchanged from aqueous-acid solutions. The hydride (I) reacts with chlorine yielding Re(DPE)CI~ (VII), and triphenylphosphineoxide. The hydride (II) is converted by chlorine into the already known salt [Re(DPE)2C12]C1,tS~ without loss of ligand. ts~j. CHArt and G. A. RowE,J. chem. Soc. 4019 (1962). ~6~(a) F. NYMANand G. A. STERN,Proc. 8th Int. Conf. Coord. Chem. Wien (1964); (b) M. FR~I, D. GIUSTOand P. ROMm,Gazz. chim. ital. (in press).
1438
M. F~r~,
R. DEmcrmus
and D. G~STO
LR. spectra. The main evidence of the presence of hydrogen atoms bound to the metal is given by the i.r. and N M R spectra. The i.r. spectrum of compound (I) both in Nujol and in benzene solution has three weak bands in the metal-hydrogen stretching region, two at 1960 and 1900 cm-1, the third still weaker at 1820 cm -1. In contrast only one very strong band appears in the same region of the i.r. spectrum of compound (II). No absorption band assignable to Re-H bending frequencies was observed in the expected region owing to the presence of a very broad band due to the ligand. As with the rhenium hydrides previously reported, t~) we were not able to prepare deuterated compounds, so that the assignment of the absorption bands to Re-H stretching vibrations is not quite conclusive. On addition, since the bands in the i.r. spectrum of compound (I) are broad and weak, any structural interpretation based upon them is tentative. TABLE 3
No. I III
V II IV
VI
VII
Compound ReHs(PPhs)2(DPE) [ReH~(PPhs)~(DPE)]CI [ReH~(PPhs)2(DPE)]CIO 4 [ReH4(PPhs)~(DPE)]I [ReH4(PPhs)z(DPE)]BPh4 ReH2(PPhs)z(DPE)I ReHs(DPE)z [ReH4(DPE)2]CI [ReH4(DPE)2]C104 [ReH4(DPE)2]I [ReH4(DPE)~]Br ReH2(DPE)2CI ReHz(DPE)2Br ReH2(DPE)zI Re(DPE)C14 [Re(DPE)2Clz]C1
Colour
M.p. (°C)
yellow white white white white yellow yellow white white white white yellow yellow yellow orange yellow
164 170 178 190 140 135 202 172 180 158 162 172 dee 178 185 dec 245 240
A~* ( ~ - 1 c m 2) -113 104 110 93 --129.0 118.3 127.4 128"2 ----126
Mol. wt. Calc. Found 1111
1237 985
1019.5 1064 1111 726
1090~: ----1123 +* 1110t ----902:~ 1006~: 1120~: 705:~ --
Z ~ . 106
5800 6000
p(D) 8.28 -----4.95 ----4.20 4.43 4-89 ---
* I n a c e t o n e solution. t I n b e n z e n e solution. I n c h l o r o f o r m solution.
All that can be said is that while the i.r. spectrum of compound (I) is in agreement with low molecular symmetry, the presence of a single strong Re-H absorption band in the i.r. spectrum of compound (II) indicates a more highly symmetrical arrangement of hydrogen atoms. Unfortunately the broad and very weak bands of the i.r. spectrum of the cations (III) and (IV) are hardly sufficient to confirm the existence of the rhenium-hydrogen bonds (Table 3). The same is true for the halogenohydrides ReH2(DPE)~X (X = C1, Br, I), which show only very weak bands at about 2000 cm-1. N M R spectra. Both the stoichiometry and the hydridic nature of compounds (I) and (II) and their derivatives (III), (IV), (V) and (VI) have been unequivocally confirmed by the N M R data, measured in CS2, acetone or chloroform solution at 60 or 100 Mc/sec (Table 1). The N M R spectrum of the compound(I) shows two resonance patterns at r = 16"27 and 16.75 respectively, indicating that the hydrogen nuclei are non-equivalent. The resonance pattern at 16.75 r is due to two equivalent hydrogen nuclei and it consists of a quintet caused by the presence of four equivalent phosphorus nuclei (JP-a = 24 c/s), which is further split by mutual coupling with the third hydrogen atom
Hydrido and halogenohydridocomplexesof rhenium(III)
1439
(Ja-2H = 10 C/S). The resonance at 16.27 ~- does not show coupling with the phosphorus atoms; it consists of a band which is not clearly resolved owing to the low solubility of the compound and the fact that the two resonance patterns are very close together. All the other compounds gave a single symmetrical resonance pattern consisting of a quintet from the coupling of the hydrogen nuclei with four equivalent phosphorus atoms. The chemical shift of the hydridic hydrogens in the halogenohydride complexes is larger than in the other rhenium hydrides: this is further evidence for the anionic character of the hydride anion in these compounds. It is noteworthy that in the compounds of type (VI), rhenium has a coordination number of seven, while the corresponding halogeno complexes are electrolytes in which rhenium is hexacoordinated in the cation. Since the chemical shift of the halogenohydrides in series decrease I > Br > CI, it seems reasonable to assume that the hydridic character of the hydrogen increases in reverse order. Finally, the observed dipole moments of about 5 D for these halogenocompounds is in agreement with a pentagonal bipyramidal structure (calculated value, 6.4 D), with the two hydrogen atoms at the apices. The compounds described in this paper are all crystalline, but only with compound (I) has it been possible to carry out an X-ray structural study, the results of which will soon be published elsewhere.