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Cobalt complexes with pnicogen (phosphine or pyridine) and thiolato ligands. Syntheses, x-ray crystal structures and spectroscopic characterization
Polyhedron
Vol. 12, No. 8, pp. 871478,
1993 0
Printed in Great Britain
0277-5387193 S6.00+ ~30 1993 Pergamon Press Ltd
COBALT COMPLEXES WITH PNICOGEN (PHOSPHINE OR PYRIDINE) AND THIOLATO LIGANDS. SYNTHESES, X-RAY CRYSTAL STRUCTURES AND SPECTROSCOPIC CHARACTERIZATION BEI-SHENG KANG,* YONG-JIN XU, JINGHAI PENG, DA-XU WU, XUE-TAI CHEN, YONGHAN HU, MAO-CHUN HONG and JIA-XI LU
State Key Laboratory of Structural Chemistry and Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P.R.C. (Received
1 October 1992 ; accepted 18 December 1992)
Abstract-Mixed pnicogen and thiolato mononuclear cobalt complexes, CO(SR),(PBU”~)~ [R = Ph (1) ; R = Stolyl-p (2)] and Co(mpo),L [L = PBu”~ (3) ; L = Py (4)], have been synthesized and studied spectroscopically. The complexes 1 and 2 are tetrahedral, as deter-
mined by magnetic susceptibility studies. The structures of 3 and 4 were determined by Xray diffraction. The cobalt(I1) ions in both 3 and 4 are in a square-pyramidal environment with the two trans-oriented mpo ligands in the basal plane and the pnicogen group in the axial position.
Cobalt complexes with mixed pnicogen (phosphine or pyridine) and dithiolene ligands were studied 20 years ago for their interesting spectroscopic features and electron transfer properties. l-5 Balch3g4 and Schrauzer’ have studied the magnetic, electronic and ligand exchange properties of a series of mononuclear dithiolene cobalt complexes containing phosphine ligands PPh3, PBun3 or P(OEt)3. Some cobalt complexes with a combination of mono-, bi- or tridentate phosphine and mono- or bidentate thiolate ligands have been identied structurally, such as mononuclear [Co(SPh),(PPh,)]and [Co(Stolyl-m)2(dppep)l,6[Co@Ph)ddpw)l and [Co(SPh)2(dppep)],7 [Co(bdt)2(PBun3)]-,8 binuclear [Co,(SR),(p-SR),(dppm)]’ (R = Ph, tolylC,H,Bu’-p) and [Cq(SPh)(p-SPh), m, -P, and trinuclear [Co3(bdt)3(PBu”3)3].* @ppe)l?‘O In our continuing investigation on the coordination chemistry of cobalt complexes containing mono- or bidentate thiolate and monodentate phosphine ligands, a series of mononuclear com-
* Author to whom correspondence should be addressed. Abbreviations : Hmpo : o-mercaptopyridine N-oxide ; dtpo : 2,2’-dithiobis(pyridine N-oxide) ; dppep : {Ph*P (CH2)2}zPPh; dppp : Ph2P(CH2),PPh, ; dppe : Ph,P (CH&PPh2; dppm: PhtPCH2PPh,; H,bdt : o-benzenedithiol ; H,mnt : maleonitriledithiol.
plexes (l-3) was obtained and the X-ray structure, magnetic and electrochemical properties and ‘H NMR spectra studied. The isolation of complex 4 is an indication that pyridine is a much stronger coordinating ligand than phosphine. EXPERIMENTAL Materials and methods
All reactions were performed under an atmosphere of dinitrogen in Schlenk-type apparatus on a vacuum-line. Solvents were dried over molecular sieves, distilled and degassed before use. The reagents CoCl, (Merck), CO(OAC)~* 4H20 (Merck), PBun3 (Merck), sodium o-mercaptopyridine N-oxide (Nampo, Aldrich), PhSH (Fluka) and HStolyl-p (Merck) are commercially available. Sodium thiolates were prepared by mixing sodium metal and thiol in dry benzene and isolating the white powder obtained. Physical measurements were performed on the following instruments : IR, Digilab FTS40 spectrophotometer ; ‘H NMR, Varian FT-80A spectrometer ; magnetic susceptibility, Gouy-Faraday magnetic balance by the Faraday method ; CV, Longjin Model 8511B potentiostat (a platinuminlay working electrode, platinum-wire auxiliary electrode, S.C.E. reference electrode).
871
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BEI-SHENG KANG et al.
Preparations
Co(SPh)z(PBun3)2 (1). To an MeCN (50 cm 3) solution of CoC12 (0.82 g, 6.32 mmol) and NaSPh (1.67 g, 12.64 mmol) was added PBun3 (3 cm 3, 12.64 mmol, d = 0.85 g cm- 3) with stirring at room temperature. After 20 h the solution was filtered and the purple filtrate gave 2.3 g (53%) of dark crystals of 1 on standing at 5°C overnight. Found : C, 61.3 ; H, 9.6; Co, 8.5; P, 9.6; S, 9.8. Calc. for C36H64CoP2S2 : C, 63.4; H, 9.4; Co, 8.7; P, 9.1 ; S, 9.4%. IR (KBr): 3050, 2960, 2940, 2870, 1575, 1465, 1080, 1025, 970, 910, 740, 695, 480, 425, 360 c m - 1.
Co(Stolyl-p)2(PBun3)2 (2). To an MeCN (50 cm 3) solution of COC12(0.82 g, 6.32 mmol) and NaStolylp (1.83 g, 12.64 mmol) was added PBun3 (3 cm 3, 12.64 mmol) slowly with stirring at room temperature. After stirring for 20 h and filtration the purple solution gave 2.1 g (46.9%) of dark crystals of 2 on standing at 5°C overnight. Found : C, 64.3 ; H, 9.8; Co, 8.0; P, 8.8; S, 9.8. Calc. for C38H68CoP252 : C, 64.3 ; H, 9.7 ; Co, 8.3 ; P, 8.7 ; S, 9.0%. IR (KBr): 3040, 2960, 2940, 2870, 1590, 1485, 1460, 1090, 1020, 970, 910, 810, 720, 630, 490, 395, 340 cm- 1. Co(mpo)EPBun3 (3). To an EtOH (40 cm 3) solution of COC12 (0.09 g, 0.69 mmol) was added, with stirring at room temperature, a mixture of dtpo (0.175 g, 0.69 mmol), sodium metal (0.032 g, 1.39 mmol) and PBun3 (0.32 cm 3, 1.28 mmol) in EtOH (10 cm3). The solution turned reddish-brown immediately, which was filtered and the filtrate gave block-shaped dark crystals of 3 (yield 63%) on standing at 5QC for several days. After isolation of 3 the mother liquor on prolonged standing gave plate-shaped dark red crystals of Co(mpo)3, which was identified by comparison of its IR spectrum with the known compound, 11 showing the oxidation ofcobalt(II) to cobalt(III). Found: C, 50.9 ; H, 7.1; Co, 11.5; N, 5.3; P, 6.1. Calc. for C22H35CoNzO2PS2: C, 51.5 ; H, 6.9; Co, 11.5 ; N, 5.5; P, 6.0%. IR (KBr): 3089, 3066, 3022, 2955, 2928, 2866, 1598, 1538, 1455, 1414, 1187, 1156, 1144, 1086, 824, 781,705,602, 569, 457, 350 cm -1. Co(mpo)aPy (4). To a stirred MeCN (40 cm 3) solution of Co(OAc)2 • 4H20 (0.25 g, 1.0 mmol) was added first pyridine (0.08 cm 3, 1.0 mmol) and then an MeOH (10 cm 3) solution of Nampo (0.30 g, 2.0 mmol) at room temperature. After standing at 5°C for 2 weeks the dark plate-like crystalline product of 4 separated, together with some unreacted Co(OAc)2 which was detected from its red colour. This crude product was filtered and washed with MeOH twice (10 cm 3) to give the pure complex 4 (yield 10%). Found: C, 45.9; H, 2.9; Co, 15.7; N,
10.0. Calc. for C15H13CoN3OzS2: C, 46.2; H, 3.4; Co, 15.1; N, 10.8%. IR (KBr): 3097-3012 (six peaks), 1596, 1538, 1456, 1441, 1411, 1216, 1182, 1159, 1136, 1088, 1066, 824, 767, 748, 705,635,611, 571,520, 447, 429, 353 cm- 1. Crystal structure determinations
The crystallographic data and data collection parameters for complexes 3 and 4 are summarized in Table 1. Single crystals were coated with epoxy resin and mounted on the Rigaku AFC5R diffractometer for data collection with Mo-K, radiation. After data reduction, including correction for Lorentz and polarization effects, the remaining unique reflections with I > 3o-(1) were used for subsequent structure solution and refinement. The structures were solved by direct methods and successive Fourier syntheses and refined by full-matrix least-squares procedures with anisotropic thermal parameters for all the non-hydrogen atoms. The hydrogen atoms were added only to the structurefactor calculations but not refined. All calculations were performed on a VAX 11/785 computer with the SDP program package. RESULTS AND DISCUSSION Synthesis
It was found that monodentate thiolate substituted mononuclear cobalt(II) complexes with bior tridentate phosphine ligands are more stable than those with monodentate phosphines, since many complexes6.7.9,10 of the former type have been characterized structurally while only one complex of the latter type has been reported. 6This unique complex, (Et4N)[Co(SPh)3(PPh3)], was obtained by reaction of CoC12 with NaSPh and PPh3 in the ratio 1 : 3 : 1.6 When a ratio of 1:2:2 for CoC12:NaSPh (or NaStolyl-p) :PBun3 was employed the reaction in MeCN led to the complex Co(SPh)2(PBun3)2 (1) or Co(Stolyl-p)ffPBun3)2 (2), which was identified by elemental analysis, IR and 1H NMR. Due to the extreme air-sensitivity of the single crystals of 1 and 2 for X-ray diffraction study the bidentate ligalad omercaptopyridine-N-oxide was employed and complexes ofpenta-coordination can be obtained which are much more stable than the tetra-coordinated ones. With a molar ratio of 1 : 1:2 for the starting materials Co2+:dtpo:PBun3 the complex Co(mpo)aPBun3 (3) was obtained, where dtpo was decomposed heterolytically by the neocleophilic attack of the methoxide ion present in solution on the S--S bond to give the anionic ligand mpo-. The complex Co(mpo)2Py (4) was isolated instead when
Co(SR),(PBu”& Table 1. Summary of crystallographic
and Co(mpo),L
873
data and data collection parameters for complexes 3 and 4 3
Formula Mol. wt Space group a (A) b (A) c (A) 0: (“) B (“) Y(“) v (A’) Z d,,r, (g cm- ‘) Crystal dimensions (mm) Temperature (“C) Radiation (wavelength) Monochromator Linear absorbance coefficient (cn- ‘) Scan method 20 range (“) Scan width (“)
F(OOO) Number Number Number Largest
of reflections collected of data for refinement” of variables residue (e k ‘)
R Rw “I > 3.00(Z). bw = 1.0. =w = l/[o’(F,)‘+0.020(F,)2+
COC~~H,,NZW’S, 513.57
PT 9.947(2) 15.740(5) 8.444(2) 94.63(2) 99.47(2) 96.12(2) 1290.0 2 1.32 0.30 x 0.25 x 0.20 23 MO-K, (0.71069 A) Graphite 9.0 U-28 50.0 0.47 542 4448 3809 271 0.48 0.053 0.0556
4
COCI&,~NJVZ 390.35
Pi
12.091(2) 14.435(3) 9.675(2) 103.68(2) 99.76(2) 83.66(2) 1612.6 4 1.61 0.25 x 0.25 x 0.15 co-& (0.71069 A) Graphite 13.2 U-28 46.1 0.46 796 4768 2237 415 0.51 0.065 0.075’
1.01.
Table 2. Selected bond distances (A) and angles (“) for the complex Co(mpo)2PBu”3 (3) 1) Co-P co-O(2) S(2+C(21) P-C(35) 0(1)-N(l) N(l)--C(ll) N(2)--C(2 1) co-S(
wtco--s(2) S(l)-Co-O( 1) S(2)---Co-P S(2)-co-O(2) P-Co-O(2) co-s(1jC(ll) Co-P-q3 1) co-P-C(39) Co-0(2)-N(2)
2.355(2) 2.424(3) 2.018(4) 1.701(6) 1.832(7) 1.352(6) 1.355(7) 1.350(7) 153.78(6) 83.8(l) 101.75(9) 82.3( 1) 95.2(l) 96.4(2) 116.7(3) 110.9(2) 117.0(3)
co-S(2) co-O( 1) S(l)-C(l1) P-C(3 1) P-C(39) 0(2)-N(2) N(Lt-C(l5) N(2)--~(25) S( l)-CO-P S( I)-co-O(2) S(2)--co-G( 1) P-Co-o( 1) O( l)-Go-o(2) co-s(2)-c!(21) co-P-X(35) Co-0(1)-N(l)
2.375(2) 1.997(3) 1.702(5) 1.827(8) 1.833(7) 1.346(6) 1.359(6) 1.359(5) 104.24(9) 92.0( 1) 91.4(l) 108.3(l) 156.6(l) 95.4(2) 118.1(3) 118.4(3)
BEI-SHENG KANG et al.
874
Table 3. Selected bond distances (/~) and angles (°) for the complex Co(mpo)2Py (4) Co(I)--S(I 1) Co(1)--S(12) Co(1)--O(11) Co(1)--O(12) Co(1)--N(1 B) S(11)--C(111) S(12)--C(121) O(11)--N(11) O(12)--N(12)
2.401(2) 2.366(2) 1.967(4) 1.955(4) 2.090(4) 1.733(6) 1.708(6) 1.363(6) 1.339(5)
S(11)--Co(1)--S(12) S(I 1)--Co(1)--O(11) S(I 1)--Co(1)--O(12) S(11)--Co(1)--N(I B) S(12)--Co(1)--O(11) S(12)--Co(1)--O(12) S(12)--Co(I)--N(1 B) O(11)--Co(1)--O(12) O(11)--Co(I)--N(1B) O(12)--Co(I)--N(1B) Co(1)--S(! 1)--C(111) Co(1)--S(12)--C(121) Co(1)--O(11)--N(11) Co(1)--O(12)--N(12) Co(1)--N(1B)--C(IB) Co(1)--N(1B)--C(3B)
Co(2)--S(21) Co(2)--S(22) Co(2)--O(21) Co(2)--O(22) Co(2)--N(201) S(21)--C(211) S(22)--C(221) O(21)--N(21) O(22)--N(22) 157.26(7) 82.9(2) 92.5(1) 98.3(1) 90.4(1) 83.5(1) 104.5(1) 153.1(2) 104.8(2) 102.2(2) 95.4(2) 95.7(2) 119.6(3) 119.2(3) 122.6(4) 118.0(4)
under the same reaction conditions a trace of pyridine was added, showing the stronger coordination ability of the pyridine molecule. Complex 4 can also be prepared with a Co 2+ : dtpo : Py ratio of 1 : 2 : 1. The amount ofpyridine has to be limited to less than 1 mol since if an excess ofpyridine was employed the complex Co(mpo)2Py2 forms immediately, which can be identified by the appearance of proton peaks corresponding to mpo and py in the ratio of 1 : 1 in the ~H N M R spectrum. Facile formation of the mono- and bis-pyridine adducts of [Co(mnt)2] 1 ,2 has been reported. Structure
Single-crystal X-ray diffraction studies have been performed on complexes 3 and 4. Tables 2 and 3 give the selected atomic distances and bond angles for complexes 3 and 4, respectively. Figures 1 and 2 depict the O R T E P structures of 3 and 4, respectively. A comparison of related structural data with other mpo substituted complexes ~-~3 is shown in Table 4. There are two discrete molecules of 4 in an asymmetric unit. Molecules of both 3 and 4 contain a squarepyramidally coordinated cobalt atom chelated by two trans-oriented mpo ligands in the basal plane
2.364(2) 2.398(2) 1.961(4) 1.990(4) 2.101(4) 1.681(6) 1.694(6) 1.334(5) 1.334(6)
S(21)--Co(2)--S(22) S(21)--Co(2)--O(21) S(21)--Co(2)~O(22) S(21)--Co(2)--N(201) S(22)--Co(2)--O(21) S(22)--Co(2)--O(22) S(22)--Co(2)--N(201) O(21)--Co(2)--O(22) O(21)--Co(2)--N(201) O(22)--Co(2)--N(201) Co(2)--S(21)--C(211) Co(2)--S(22)--C(221) Co(2)---O(21)--N(21) Co(2)--O(22)--N(22) Co(2)--N(201)--C(201 ) Co(2)--N(201)--C(205)
155.97(7) 84.0(1) 91.8(1) 104.8(1) 91.1(1) 82.3(2) 99.3(1) 153.8(2) 101.1(2) 105.0(2) 94.6(2) 95.0(2) 119.3(4) 120.3(4) 120.7(4) 119.1(4)
and a neutral pnicogen molecule, PBUn3 or Py, in the axial position. The C o - - S and C o - - O bonds in both complexes 3 and 4 are in the ranges 2.36-2.40 and 1.96-2.02 ~, respectively, which are all longer than those in the six-coordinate Co(mpo)3 (average 2.194 and 1.933 /~).11 The N - - O bond changes neither with the coordination number nor with the type of central atom of the complexes and is maintained in the range 1.34-1.35 ~, whilst the average S - - C bonds are in the range 1.70-1.72/~ for the complexes listed in Table 4 with the shortest values for complexes 3 and 4, agreeing with the fact that the thione form is the predominant coordination mode of mpo : ~3
0 Thiol
OH Thione
Thus, this results in the shortening of the C - - S bond compared to the normal covalent distance (1.81 /~)14 for a single bond. The C o - - P distance of 2.424 A in 3 is so far the longest observed in cobalt-phosphine complexes,6-10, ~5,~6 implying the weak bonding and easy dissociation of PBun3,
CO(SR),(PBU”,)~and Co(mpo),L
875
Fig. 1. ORTEP structure of the complex Co(mpo),PBun3 (3) with the carbon atoms represented by arbitrary spheres for clarity.
which agrees well with the ‘H NMR data (see below). The bite angles S,-Co-O, (average 83.2”) for the trans-coordinated mpo ligands in complexes 3 and 4 are obviously smaller than those in Co(mpo),” (88.0”) or Ni(mpo)2’3 (89.6”), where
the mpos are in facial (S,-Co-S, 91.2”) or cis conformations (S,-Co-S, 92X), respectively, but comparable to that in Fe(mpo)3’2 (S,-Co-0, 167.7”) in which the mpo 8 1. lo ; &,-Co-S, ligands are meridionally oriented. This result may indicate the fact that the S .a. S interaction, when
C(4B)
Fig. 2. ORTEP structure of the complex Co(mpo),Py (4).
f
876
BEI-SHENG KANG et al. Table 4. Comparison of average atomic distances (/~) and bond angles (°) of some complexes containing o-mercaptopyridine N-oxide Parameter
3
4
Fe(mpo) 31:
Co(mpo) 311
Ni(mpo) 213
2.382 1.968 1.343 1.704 95.2 119.6 83.2 156.6
2.194 1.933 1.348 1.716 96.8 116.0 88.0 91.15
On--Co--Om
156.6
153.5
Coordination
5
5
2.419 2.009 1.340 1.716 96.7 121.3 81.1 167.74 100.37 89.10 167.7 97.6 88.3 6a
2.133 1.866 1.350 1.712
Sn--Co----O m
2.365 2.008 1.349 1.702 95.9 117.7 83.1 153.8
Co--S Co--O O~N S--C Co--S--C Co--O---N S,--Co---On
86.9
6b
89.6 92.81
88.1
4
a Meridional. bFacial.
the sulphur atoms are in nearby positions, expands the bite angle by drawing electrons away from the chelate ring. Both C o - - S - - C (average 95.6 °) and C o - - O - - N (average 118.7 °) angles within the fivemembered chelate ring C o - - O - - N - - C - - S are within the normal ranges 13for the sulphur and oxygen donor atoms to employ mainly p and sp 2 hybrid orbitals for bonding, respectively.
Spectroscopic studies The I R spectra of complexes 1 and 2 are quite similar to each other, except for the C - - H out-ofplane bending absorptions of the benzene ring. Two peaks at 740 and 698 c m - ~are characteristic for the mono-substituted phenyl group in complex 1, while the p-tolyl group in complex 2 gave only one absorption at 810 cm ~ for the 1,4-disubstituted phenyl ring. Complex 3 showed an absorption at 1144 c m - ~ with a shoulder at 1156 c m - ~ for S - - C bonds, which appeared as two strong bands at 1136 and 1159 cm-1 for complex 4. These absorptions are indications of partial k S double bond character, as compared with the free ligand H m p o (1142 cm-1) which has been established by Jones t7 to be predominantly in the thione form. The appearance of a set of three peaks in the region 2960-2870 c m in complexes 1-3 is a clear indication of the presence of the PBun3 group. The C - - H stretching vibrations of the m p o ligand appear in the range 3100-3020 c m - ~ in complexes 3 and 4 and the C o - - S absorptions appear at 457 and 350 c m - ~ (3) and 447 and 353 cm i (4).
The 1H N M R data at room temperature of complexes 1~4 are listed in Table 5, where the paramagnetism of the complexes is clearly shown by the large chemical shifts. Contact contributions to the chemical shifts are shown by signals with alternating signs for the meta- and para-protons of the phenyl groups: 29.74 and - 4 8 . 8 8 ppm, respectively, in the ratio 2:1 for complex 1, while the ortho-proton signals are too broad to be detected. In the meantime, complex 2 showed the same result of contact interaction where methyl substitution in the para-position for the tolyl-p group alternates the sign of the p-proton to give a signal at 52.92 ppm, with the m-protons appearing at 29.89 ppm. Complexes 3 and 4 showed very similar chemical shifts for the m p o ligands, yet the fate of the pnicogen ligands is quite different in the solvent DMSO. The spectrum showed the dissociation of PBun3 for 3 as the chemical shifts of 0.98 and 1.50 p p m are close to those for the free ligand. 8 The pyridine ligand in 4 showed completely different chemical shifts as compared with the free molecule (8.5, 7.35 and 7.0 for ~-, r- and ~-H, respectively)~ 18 with the signal for a-protons near 20 p p m buried under the peaks of Hc of m p o (see Table 5 for proton assignment). These data indicate the strong affinity of pyridine with the central Co 2÷ ion as compared to phosphine.
Physical-chemical properties All the complexes are paramagnetic. The magnetic moments of I and 2 at r o o m temperature are
Co(SR),(PBu”,),
and Co(mpo),L
877
Table 5. ‘H NMR data (ppm) of the complexes l-4 at room temperature
Complex Co(SPh),(PBu”,), Co(Stolyl-p),(PBu”,), Co(mpo),PBu”, Co(mpo),Py
Solvent
m-H
CD&l, CD&l2 DMSO-ds DMSO-ds
29.74 29.89 / /
SR pH
p_CH,
-48.88 /
/ 52.92
HA
65.5 65.5
mpo” H, Hc
18.7 18.3
Hn
/ / 19.9 24.7 19.8 24.5
a-CH,
PBu”, B-CH,
90.08 3.62 89.5 3.62 0.98-1.506 12.3 (B-H) 8.0 (F-H)’
Other 1.74 1.69
‘The assignment for protons of mpo :
bData indicate dissociation of Bu”~. ‘Data for the pyridine ligand.
4.40 and 4.54 PB, respectively. These values being higher than the calculated spin-only value of 3.87 PB for a high spin state S = 3/2 for cobalt(I1) show that there is a certain degree of orbital contribution to the magnetic moment.‘9-21 Knowing that tetra-
-1.26
hedral [CO(SR)J’-~~ possesses a solid moment of 4.6 pB23 and comparing with a series of reported phosphine substituted cobalt(I1) complexes with tetrahedral structures and magnetic moments in the range 4.41-4.63 ,uB,” the tetrahedral geometry
V
(b)
-0.65
V
Fig. 3. Cyclic voltammograms
0.0
-0.65
V
of (a) complex 1 and (b) complex 2 in MeCN vs S.C.E. at a scan rate of 100 mV s- ’ at room temperature.
878
BEI-SHENG KANG et al.
of the cobalt atom in complexes 1 and 2 can be deduced. Their X-ray single-crystal structure determinations await low temperature facilities. The effective magnetic m o m e n t of 3.77 #~ for complex 3 corresponds to a spin-only state of S = 3/2 for the cobalt(II) ion. The cyclic v o l t a m m o g r a m s of complexes 1 and 2 were measured in M e C N in the range 1.5 to - 1.5 V, either reductively or oxidatively. Both complexes showed two quasi-reversible reduction waves and two irreversible oxidation waves, as shown in Fig. 3. It is believed that in addition to the reduction ( - 1.26 and - 1.33 V) or oxidation (0.43 and 0.41 V) of the complexes (3 and 4, respectively), the ligands also engaged in redox processes within the applied potentials. The waves near 1.0 V account for the oxidation of the thiolates. Acknowledgement--This work was supported by NNSF, NSFCAS and FNSF.
REFERENCES 1. I. G. Dance, Inorg. Chem. 1973, 12, 2381. 2. I. G. Dance and T. R. Miller, Inorg. Chem. 1974, 13, 525. 3. A. L. Balch, Inorg. Chem. 1967, 6, 2158. 4. A. L. Balch, Inorg. Chem. 1971, 10, 388. 5. G. N. Schrauzer, V. P'. Mayweg, H. W. Finck and W. Heinrich, J. Am. Chem. Soc. 1966, 88, 4604. 6. F. L. Jiang, G. W. Wei, Z. Y. Huang, X. J. Lei, M. C. Hong, B. S. Kang and H. Q. Liu, J. Coord. Chem. 1992, 25, 183. 7. G. W. Wei, M. C. Hong, Z. Y. Huang and H. Q. Liu, J. Chem. Soc., Dalton Trans. 1991, 3145.
8. B. S. Kang, J. H. Peng, M. C. Hong, D. X. Wu, X. T. Chen, L. H. Weng, X. J. Lei and H. Q. Liu, J. Chem. Soc., Dalton Trans. 1991, 2897. 9. G. W. Wei, H. Q. Liu, Z. Y. Huang, M. C. Hong, L. R. Huang and B. S. Kang, Polyhedron 1991, 10, 553. 10. G. W. Wei, H. Q. Liu, Z. Y. Huang, L. R. Huang and B. S. Kang, J. Chem. Soc., Chem. Commun. 1989, 1839. 11. Y. H. Hu, L. H. Weng, L. R. Huang, X. T. Chen, D. X. Wu and B. S. Kang, Acta Cryst. 1991, C47, 2655. 12. Y. H. Hu, X. T. Chen, L. Dai, L. H. Weng and B. S. Kang, Jeigou Huaxue 1993, 12, 38. 13. X. T. Chen, Y. H. Hu, D. X. Wu, L. H. Weng and B. S. Kang, Polyhedron 1991, 10, 2651. 14. J. D. Lydon, R. C. Elder and E. Deutsch, Inorg. Chem. 1982, 21, 3186. 15. P. B. Hitchcock and G. M. McLanghlin, J. Chem. Soc., Dalton Trans. 1976, 1929. 16. W. Levason, J. S. Ogden and M. D. Spicer, Inorg. Chem. 1989, 28, 2128. 17. R. A. Jones and A. R. Katritzsky, J. Chem. Soc., 1960, 2937. 18. R. M. Silverstein and G. C. Bassler, Spectrometric Identification of Organic Compounds, p. 85. John Wiley and Sons, New York (1964). 19. R. H. Holm and F. A. Cotton, J. Chem. Phys. 1960, 32, 1168. 20. F. A. Cotton and M. Goodgame, J. Am. Chem. Soc. 1961, 83, 1177. 21. F. A. Cotton, O. D. Faut, D. M. L. Goodgame and R. H. Holm, J. Am. Chem. Soc. 1961, 83, 1780. 22. R. W. Lane, J. A. Ibers, R. B. Frankel, G. C. Papaefthymiou and R. H. Holm, J. Am. Chem. Soc. 1977, 99, 84, 23. J. R. Dorfman, Ch. P. Rao and R. H. Holm, Inorg. Chem. 1985, 24, 453.
Vol. 12, No. 8, pp. 871478,
1993 0
Printed in Great Britain
0277-5387193 S6.00+ ~30 1993 Pergamon Press Ltd
COBALT COMPLEXES WITH PNICOGEN (PHOSPHINE OR PYRIDINE) AND THIOLATO LIGANDS. SYNTHESES, X-RAY CRYSTAL STRUCTURES AND SPECTROSCOPIC CHARACTERIZATION BEI-SHENG KANG,* YONG-JIN XU, JINGHAI PENG, DA-XU WU, XUE-TAI CHEN, YONGHAN HU, MAO-CHUN HONG and JIA-XI LU
State Key Laboratory of Structural Chemistry and Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P.R.C. (Received
1 October 1992 ; accepted 18 December 1992)
Abstract-Mixed pnicogen and thiolato mononuclear cobalt complexes, CO(SR),(PBU”~)~ [R = Ph (1) ; R = Stolyl-p (2)] and Co(mpo),L [L = PBu”~ (3) ; L = Py (4)], have been synthesized and studied spectroscopically. The complexes 1 and 2 are tetrahedral, as deter-
mined by magnetic susceptibility studies. The structures of 3 and 4 were determined by Xray diffraction. The cobalt(I1) ions in both 3 and 4 are in a square-pyramidal environment with the two trans-oriented mpo ligands in the basal plane and the pnicogen group in the axial position.
Cobalt complexes with mixed pnicogen (phosphine or pyridine) and dithiolene ligands were studied 20 years ago for their interesting spectroscopic features and electron transfer properties. l-5 Balch3g4 and Schrauzer’ have studied the magnetic, electronic and ligand exchange properties of a series of mononuclear dithiolene cobalt complexes containing phosphine ligands PPh3, PBun3 or P(OEt)3. Some cobalt complexes with a combination of mono-, bi- or tridentate phosphine and mono- or bidentate thiolate ligands have been identied structurally, such as mononuclear [Co(SPh),(PPh,)]and [Co(Stolyl-m)2(dppep)l,6[Co@Ph)ddpw)l and [Co(SPh)2(dppep)],7 [Co(bdt)2(PBun3)]-,8 binuclear [Co,(SR),(p-SR),(dppm)]’ (R = Ph, tolylC,H,Bu’-p) and [Cq(SPh)(p-SPh), m, -P, and trinuclear [Co3(bdt)3(PBu”3)3].* @ppe)l?‘O In our continuing investigation on the coordination chemistry of cobalt complexes containing mono- or bidentate thiolate and monodentate phosphine ligands, a series of mononuclear com-
* Author to whom correspondence should be addressed. Abbreviations : Hmpo : o-mercaptopyridine N-oxide ; dtpo : 2,2’-dithiobis(pyridine N-oxide) ; dppep : {Ph*P (CH2)2}zPPh; dppp : Ph2P(CH2),PPh, ; dppe : Ph,P (CH&PPh2; dppm: PhtPCH2PPh,; H,bdt : o-benzenedithiol ; H,mnt : maleonitriledithiol.
plexes (l-3) was obtained and the X-ray structure, magnetic and electrochemical properties and ‘H NMR spectra studied. The isolation of complex 4 is an indication that pyridine is a much stronger coordinating ligand than phosphine. EXPERIMENTAL Materials and methods
All reactions were performed under an atmosphere of dinitrogen in Schlenk-type apparatus on a vacuum-line. Solvents were dried over molecular sieves, distilled and degassed before use. The reagents CoCl, (Merck), CO(OAC)~* 4H20 (Merck), PBun3 (Merck), sodium o-mercaptopyridine N-oxide (Nampo, Aldrich), PhSH (Fluka) and HStolyl-p (Merck) are commercially available. Sodium thiolates were prepared by mixing sodium metal and thiol in dry benzene and isolating the white powder obtained. Physical measurements were performed on the following instruments : IR, Digilab FTS40 spectrophotometer ; ‘H NMR, Varian FT-80A spectrometer ; magnetic susceptibility, Gouy-Faraday magnetic balance by the Faraday method ; CV, Longjin Model 8511B potentiostat (a platinuminlay working electrode, platinum-wire auxiliary electrode, S.C.E. reference electrode).
871
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BEI-SHENG KANG et al.
Preparations
Co(SPh)z(PBun3)2 (1). To an MeCN (50 cm 3) solution of CoC12 (0.82 g, 6.32 mmol) and NaSPh (1.67 g, 12.64 mmol) was added PBun3 (3 cm 3, 12.64 mmol, d = 0.85 g cm- 3) with stirring at room temperature. After 20 h the solution was filtered and the purple filtrate gave 2.3 g (53%) of dark crystals of 1 on standing at 5°C overnight. Found : C, 61.3 ; H, 9.6; Co, 8.5; P, 9.6; S, 9.8. Calc. for C36H64CoP2S2 : C, 63.4; H, 9.4; Co, 8.7; P, 9.1 ; S, 9.4%. IR (KBr): 3050, 2960, 2940, 2870, 1575, 1465, 1080, 1025, 970, 910, 740, 695, 480, 425, 360 c m - 1.
Co(Stolyl-p)2(PBun3)2 (2). To an MeCN (50 cm 3) solution of COC12(0.82 g, 6.32 mmol) and NaStolylp (1.83 g, 12.64 mmol) was added PBun3 (3 cm 3, 12.64 mmol) slowly with stirring at room temperature. After stirring for 20 h and filtration the purple solution gave 2.1 g (46.9%) of dark crystals of 2 on standing at 5°C overnight. Found : C, 64.3 ; H, 9.8; Co, 8.0; P, 8.8; S, 9.8. Calc. for C38H68CoP252 : C, 64.3 ; H, 9.7 ; Co, 8.3 ; P, 8.7 ; S, 9.0%. IR (KBr): 3040, 2960, 2940, 2870, 1590, 1485, 1460, 1090, 1020, 970, 910, 810, 720, 630, 490, 395, 340 cm- 1. Co(mpo)EPBun3 (3). To an EtOH (40 cm 3) solution of COC12 (0.09 g, 0.69 mmol) was added, with stirring at room temperature, a mixture of dtpo (0.175 g, 0.69 mmol), sodium metal (0.032 g, 1.39 mmol) and PBun3 (0.32 cm 3, 1.28 mmol) in EtOH (10 cm3). The solution turned reddish-brown immediately, which was filtered and the filtrate gave block-shaped dark crystals of 3 (yield 63%) on standing at 5QC for several days. After isolation of 3 the mother liquor on prolonged standing gave plate-shaped dark red crystals of Co(mpo)3, which was identified by comparison of its IR spectrum with the known compound, 11 showing the oxidation ofcobalt(II) to cobalt(III). Found: C, 50.9 ; H, 7.1; Co, 11.5; N, 5.3; P, 6.1. Calc. for C22H35CoNzO2PS2: C, 51.5 ; H, 6.9; Co, 11.5 ; N, 5.5; P, 6.0%. IR (KBr): 3089, 3066, 3022, 2955, 2928, 2866, 1598, 1538, 1455, 1414, 1187, 1156, 1144, 1086, 824, 781,705,602, 569, 457, 350 cm -1. Co(mpo)aPy (4). To a stirred MeCN (40 cm 3) solution of Co(OAc)2 • 4H20 (0.25 g, 1.0 mmol) was added first pyridine (0.08 cm 3, 1.0 mmol) and then an MeOH (10 cm 3) solution of Nampo (0.30 g, 2.0 mmol) at room temperature. After standing at 5°C for 2 weeks the dark plate-like crystalline product of 4 separated, together with some unreacted Co(OAc)2 which was detected from its red colour. This crude product was filtered and washed with MeOH twice (10 cm 3) to give the pure complex 4 (yield 10%). Found: C, 45.9; H, 2.9; Co, 15.7; N,
10.0. Calc. for C15H13CoN3OzS2: C, 46.2; H, 3.4; Co, 15.1; N, 10.8%. IR (KBr): 3097-3012 (six peaks), 1596, 1538, 1456, 1441, 1411, 1216, 1182, 1159, 1136, 1088, 1066, 824, 767, 748, 705,635,611, 571,520, 447, 429, 353 cm- 1. Crystal structure determinations
The crystallographic data and data collection parameters for complexes 3 and 4 are summarized in Table 1. Single crystals were coated with epoxy resin and mounted on the Rigaku AFC5R diffractometer for data collection with Mo-K, radiation. After data reduction, including correction for Lorentz and polarization effects, the remaining unique reflections with I > 3o-(1) were used for subsequent structure solution and refinement. The structures were solved by direct methods and successive Fourier syntheses and refined by full-matrix least-squares procedures with anisotropic thermal parameters for all the non-hydrogen atoms. The hydrogen atoms were added only to the structurefactor calculations but not refined. All calculations were performed on a VAX 11/785 computer with the SDP program package. RESULTS AND DISCUSSION Synthesis
It was found that monodentate thiolate substituted mononuclear cobalt(II) complexes with bior tridentate phosphine ligands are more stable than those with monodentate phosphines, since many complexes6.7.9,10 of the former type have been characterized structurally while only one complex of the latter type has been reported. 6This unique complex, (Et4N)[Co(SPh)3(PPh3)], was obtained by reaction of CoC12 with NaSPh and PPh3 in the ratio 1 : 3 : 1.6 When a ratio of 1:2:2 for CoC12:NaSPh (or NaStolyl-p) :PBun3 was employed the reaction in MeCN led to the complex Co(SPh)2(PBun3)2 (1) or Co(Stolyl-p)ffPBun3)2 (2), which was identified by elemental analysis, IR and 1H NMR. Due to the extreme air-sensitivity of the single crystals of 1 and 2 for X-ray diffraction study the bidentate ligalad omercaptopyridine-N-oxide was employed and complexes ofpenta-coordination can be obtained which are much more stable than the tetra-coordinated ones. With a molar ratio of 1 : 1:2 for the starting materials Co2+:dtpo:PBun3 the complex Co(mpo)aPBun3 (3) was obtained, where dtpo was decomposed heterolytically by the neocleophilic attack of the methoxide ion present in solution on the S--S bond to give the anionic ligand mpo-. The complex Co(mpo)2Py (4) was isolated instead when
Co(SR),(PBu”& Table 1. Summary of crystallographic
and Co(mpo),L
873
data and data collection parameters for complexes 3 and 4 3
Formula Mol. wt Space group a (A) b (A) c (A) 0: (“) B (“) Y(“) v (A’) Z d,,r, (g cm- ‘) Crystal dimensions (mm) Temperature (“C) Radiation (wavelength) Monochromator Linear absorbance coefficient (cn- ‘) Scan method 20 range (“) Scan width (“)
F(OOO) Number Number Number Largest
of reflections collected of data for refinement” of variables residue (e k ‘)
R Rw “I > 3.00(Z). bw = 1.0. =w = l/[o’(F,)‘+0.020(F,)2+
COC~~H,,NZW’S, 513.57
PT 9.947(2) 15.740(5) 8.444(2) 94.63(2) 99.47(2) 96.12(2) 1290.0 2 1.32 0.30 x 0.25 x 0.20 23 MO-K, (0.71069 A) Graphite 9.0 U-28 50.0 0.47 542 4448 3809 271 0.48 0.053 0.0556
4
COCI&,~NJVZ 390.35
Pi
12.091(2) 14.435(3) 9.675(2) 103.68(2) 99.76(2) 83.66(2) 1612.6 4 1.61 0.25 x 0.25 x 0.15 co-& (0.71069 A) Graphite 13.2 U-28 46.1 0.46 796 4768 2237 415 0.51 0.065 0.075’
1.01.
Table 2. Selected bond distances (A) and angles (“) for the complex Co(mpo)2PBu”3 (3) 1) Co-P co-O(2) S(2+C(21) P-C(35) 0(1)-N(l) N(l)--C(ll) N(2)--C(2 1) co-S(
wtco--s(2) S(l)-Co-O( 1) S(2)---Co-P S(2)-co-O(2) P-Co-O(2) co-s(1jC(ll) Co-P-q3 1) co-P-C(39) Co-0(2)-N(2)
2.355(2) 2.424(3) 2.018(4) 1.701(6) 1.832(7) 1.352(6) 1.355(7) 1.350(7) 153.78(6) 83.8(l) 101.75(9) 82.3( 1) 95.2(l) 96.4(2) 116.7(3) 110.9(2) 117.0(3)
co-S(2) co-O( 1) S(l)-C(l1) P-C(3 1) P-C(39) 0(2)-N(2) N(Lt-C(l5) N(2)--~(25) S( l)-CO-P S( I)-co-O(2) S(2)--co-G( 1) P-Co-o( 1) O( l)-Go-o(2) co-s(2)-c!(21) co-P-X(35) Co-0(1)-N(l)
2.375(2) 1.997(3) 1.702(5) 1.827(8) 1.833(7) 1.346(6) 1.359(6) 1.359(5) 104.24(9) 92.0( 1) 91.4(l) 108.3(l) 156.6(l) 95.4(2) 118.1(3) 118.4(3)
BEI-SHENG KANG et al.
874
Table 3. Selected bond distances (/~) and angles (°) for the complex Co(mpo)2Py (4) Co(I)--S(I 1) Co(1)--S(12) Co(1)--O(11) Co(1)--O(12) Co(1)--N(1 B) S(11)--C(111) S(12)--C(121) O(11)--N(11) O(12)--N(12)
2.401(2) 2.366(2) 1.967(4) 1.955(4) 2.090(4) 1.733(6) 1.708(6) 1.363(6) 1.339(5)
S(11)--Co(1)--S(12) S(I 1)--Co(1)--O(11) S(I 1)--Co(1)--O(12) S(11)--Co(1)--N(I B) S(12)--Co(1)--O(11) S(12)--Co(1)--O(12) S(12)--Co(I)--N(1 B) O(11)--Co(1)--O(12) O(11)--Co(I)--N(1B) O(12)--Co(I)--N(1B) Co(1)--S(! 1)--C(111) Co(1)--S(12)--C(121) Co(1)--O(11)--N(11) Co(1)--O(12)--N(12) Co(1)--N(1B)--C(IB) Co(1)--N(1B)--C(3B)
Co(2)--S(21) Co(2)--S(22) Co(2)--O(21) Co(2)--O(22) Co(2)--N(201) S(21)--C(211) S(22)--C(221) O(21)--N(21) O(22)--N(22) 157.26(7) 82.9(2) 92.5(1) 98.3(1) 90.4(1) 83.5(1) 104.5(1) 153.1(2) 104.8(2) 102.2(2) 95.4(2) 95.7(2) 119.6(3) 119.2(3) 122.6(4) 118.0(4)
under the same reaction conditions a trace of pyridine was added, showing the stronger coordination ability of the pyridine molecule. Complex 4 can also be prepared with a Co 2+ : dtpo : Py ratio of 1 : 2 : 1. The amount ofpyridine has to be limited to less than 1 mol since if an excess ofpyridine was employed the complex Co(mpo)2Py2 forms immediately, which can be identified by the appearance of proton peaks corresponding to mpo and py in the ratio of 1 : 1 in the ~H N M R spectrum. Facile formation of the mono- and bis-pyridine adducts of [Co(mnt)2] 1 ,2 has been reported. Structure
Single-crystal X-ray diffraction studies have been performed on complexes 3 and 4. Tables 2 and 3 give the selected atomic distances and bond angles for complexes 3 and 4, respectively. Figures 1 and 2 depict the O R T E P structures of 3 and 4, respectively. A comparison of related structural data with other mpo substituted complexes ~-~3 is shown in Table 4. There are two discrete molecules of 4 in an asymmetric unit. Molecules of both 3 and 4 contain a squarepyramidally coordinated cobalt atom chelated by two trans-oriented mpo ligands in the basal plane
2.364(2) 2.398(2) 1.961(4) 1.990(4) 2.101(4) 1.681(6) 1.694(6) 1.334(5) 1.334(6)
S(21)--Co(2)--S(22) S(21)--Co(2)--O(21) S(21)--Co(2)~O(22) S(21)--Co(2)--N(201) S(22)--Co(2)--O(21) S(22)--Co(2)--O(22) S(22)--Co(2)--N(201) O(21)--Co(2)--O(22) O(21)--Co(2)--N(201) O(22)--Co(2)--N(201) Co(2)--S(21)--C(211) Co(2)--S(22)--C(221) Co(2)---O(21)--N(21) Co(2)--O(22)--N(22) Co(2)--N(201)--C(201 ) Co(2)--N(201)--C(205)
155.97(7) 84.0(1) 91.8(1) 104.8(1) 91.1(1) 82.3(2) 99.3(1) 153.8(2) 101.1(2) 105.0(2) 94.6(2) 95.0(2) 119.3(4) 120.3(4) 120.7(4) 119.1(4)
and a neutral pnicogen molecule, PBUn3 or Py, in the axial position. The C o - - S and C o - - O bonds in both complexes 3 and 4 are in the ranges 2.36-2.40 and 1.96-2.02 ~, respectively, which are all longer than those in the six-coordinate Co(mpo)3 (average 2.194 and 1.933 /~).11 The N - - O bond changes neither with the coordination number nor with the type of central atom of the complexes and is maintained in the range 1.34-1.35 ~, whilst the average S - - C bonds are in the range 1.70-1.72/~ for the complexes listed in Table 4 with the shortest values for complexes 3 and 4, agreeing with the fact that the thione form is the predominant coordination mode of mpo : ~3
0 Thiol
OH Thione
Thus, this results in the shortening of the C - - S bond compared to the normal covalent distance (1.81 /~)14 for a single bond. The C o - - P distance of 2.424 A in 3 is so far the longest observed in cobalt-phosphine complexes,6-10, ~5,~6 implying the weak bonding and easy dissociation of PBun3,
CO(SR),(PBU”,)~and Co(mpo),L
875
Fig. 1. ORTEP structure of the complex Co(mpo),PBun3 (3) with the carbon atoms represented by arbitrary spheres for clarity.
which agrees well with the ‘H NMR data (see below). The bite angles S,-Co-O, (average 83.2”) for the trans-coordinated mpo ligands in complexes 3 and 4 are obviously smaller than those in Co(mpo),” (88.0”) or Ni(mpo)2’3 (89.6”), where
the mpos are in facial (S,-Co-S, 91.2”) or cis conformations (S,-Co-S, 92X), respectively, but comparable to that in Fe(mpo)3’2 (S,-Co-0, 167.7”) in which the mpo 8 1. lo ; &,-Co-S, ligands are meridionally oriented. This result may indicate the fact that the S .a. S interaction, when
C(4B)
Fig. 2. ORTEP structure of the complex Co(mpo),Py (4).
f
876
BEI-SHENG KANG et al. Table 4. Comparison of average atomic distances (/~) and bond angles (°) of some complexes containing o-mercaptopyridine N-oxide Parameter
3
4
Fe(mpo) 31:
Co(mpo) 311
Ni(mpo) 213
2.382 1.968 1.343 1.704 95.2 119.6 83.2 156.6
2.194 1.933 1.348 1.716 96.8 116.0 88.0 91.15
On--Co--Om
156.6
153.5
Coordination
5
5
2.419 2.009 1.340 1.716 96.7 121.3 81.1 167.74 100.37 89.10 167.7 97.6 88.3 6a
2.133 1.866 1.350 1.712
Sn--Co----O m
2.365 2.008 1.349 1.702 95.9 117.7 83.1 153.8
Co--S Co--O O~N S--C Co--S--C Co--O---N S,--Co---On
86.9
6b
89.6 92.81
88.1
4
a Meridional. bFacial.
the sulphur atoms are in nearby positions, expands the bite angle by drawing electrons away from the chelate ring. Both C o - - S - - C (average 95.6 °) and C o - - O - - N (average 118.7 °) angles within the fivemembered chelate ring C o - - O - - N - - C - - S are within the normal ranges 13for the sulphur and oxygen donor atoms to employ mainly p and sp 2 hybrid orbitals for bonding, respectively.
Spectroscopic studies The I R spectra of complexes 1 and 2 are quite similar to each other, except for the C - - H out-ofplane bending absorptions of the benzene ring. Two peaks at 740 and 698 c m - ~are characteristic for the mono-substituted phenyl group in complex 1, while the p-tolyl group in complex 2 gave only one absorption at 810 cm ~ for the 1,4-disubstituted phenyl ring. Complex 3 showed an absorption at 1144 c m - ~ with a shoulder at 1156 c m - ~ for S - - C bonds, which appeared as two strong bands at 1136 and 1159 cm-1 for complex 4. These absorptions are indications of partial k S double bond character, as compared with the free ligand H m p o (1142 cm-1) which has been established by Jones t7 to be predominantly in the thione form. The appearance of a set of three peaks in the region 2960-2870 c m in complexes 1-3 is a clear indication of the presence of the PBun3 group. The C - - H stretching vibrations of the m p o ligand appear in the range 3100-3020 c m - ~ in complexes 3 and 4 and the C o - - S absorptions appear at 457 and 350 c m - ~ (3) and 447 and 353 cm i (4).
The 1H N M R data at room temperature of complexes 1~4 are listed in Table 5, where the paramagnetism of the complexes is clearly shown by the large chemical shifts. Contact contributions to the chemical shifts are shown by signals with alternating signs for the meta- and para-protons of the phenyl groups: 29.74 and - 4 8 . 8 8 ppm, respectively, in the ratio 2:1 for complex 1, while the ortho-proton signals are too broad to be detected. In the meantime, complex 2 showed the same result of contact interaction where methyl substitution in the para-position for the tolyl-p group alternates the sign of the p-proton to give a signal at 52.92 ppm, with the m-protons appearing at 29.89 ppm. Complexes 3 and 4 showed very similar chemical shifts for the m p o ligands, yet the fate of the pnicogen ligands is quite different in the solvent DMSO. The spectrum showed the dissociation of PBun3 for 3 as the chemical shifts of 0.98 and 1.50 p p m are close to those for the free ligand. 8 The pyridine ligand in 4 showed completely different chemical shifts as compared with the free molecule (8.5, 7.35 and 7.0 for ~-, r- and ~-H, respectively)~ 18 with the signal for a-protons near 20 p p m buried under the peaks of Hc of m p o (see Table 5 for proton assignment). These data indicate the strong affinity of pyridine with the central Co 2÷ ion as compared to phosphine.
Physical-chemical properties All the complexes are paramagnetic. The magnetic moments of I and 2 at r o o m temperature are
Co(SR),(PBu”,),
and Co(mpo),L
877
Table 5. ‘H NMR data (ppm) of the complexes l-4 at room temperature
Complex Co(SPh),(PBu”,), Co(Stolyl-p),(PBu”,), Co(mpo),PBu”, Co(mpo),Py
Solvent
m-H
CD&l, CD&l2 DMSO-ds DMSO-ds
29.74 29.89 / /
SR pH
p_CH,
-48.88 /
/ 52.92
HA
65.5 65.5
mpo” H, Hc
18.7 18.3
Hn
/ / 19.9 24.7 19.8 24.5
a-CH,
PBu”, B-CH,
90.08 3.62 89.5 3.62 0.98-1.506 12.3 (B-H) 8.0 (F-H)’
Other 1.74 1.69
‘The assignment for protons of mpo :
bData indicate dissociation of Bu”~. ‘Data for the pyridine ligand.
4.40 and 4.54 PB, respectively. These values being higher than the calculated spin-only value of 3.87 PB for a high spin state S = 3/2 for cobalt(I1) show that there is a certain degree of orbital contribution to the magnetic moment.‘9-21 Knowing that tetra-
-1.26
hedral [CO(SR)J’-~~ possesses a solid moment of 4.6 pB23 and comparing with a series of reported phosphine substituted cobalt(I1) complexes with tetrahedral structures and magnetic moments in the range 4.41-4.63 ,uB,” the tetrahedral geometry
V
(b)
-0.65
V
Fig. 3. Cyclic voltammograms
0.0
-0.65
V
of (a) complex 1 and (b) complex 2 in MeCN vs S.C.E. at a scan rate of 100 mV s- ’ at room temperature.
878
BEI-SHENG KANG et al.
of the cobalt atom in complexes 1 and 2 can be deduced. Their X-ray single-crystal structure determinations await low temperature facilities. The effective magnetic m o m e n t of 3.77 #~ for complex 3 corresponds to a spin-only state of S = 3/2 for the cobalt(II) ion. The cyclic v o l t a m m o g r a m s of complexes 1 and 2 were measured in M e C N in the range 1.5 to - 1.5 V, either reductively or oxidatively. Both complexes showed two quasi-reversible reduction waves and two irreversible oxidation waves, as shown in Fig. 3. It is believed that in addition to the reduction ( - 1.26 and - 1.33 V) or oxidation (0.43 and 0.41 V) of the complexes (3 and 4, respectively), the ligands also engaged in redox processes within the applied potentials. The waves near 1.0 V account for the oxidation of the thiolates. Acknowledgement--This work was supported by NNSF, NSFCAS and FNSF.
REFERENCES 1. I. G. Dance, Inorg. Chem. 1973, 12, 2381. 2. I. G. Dance and T. R. Miller, Inorg. Chem. 1974, 13, 525. 3. A. L. Balch, Inorg. Chem. 1967, 6, 2158. 4. A. L. Balch, Inorg. Chem. 1971, 10, 388. 5. G. N. Schrauzer, V. P'. Mayweg, H. W. Finck and W. Heinrich, J. Am. Chem. Soc. 1966, 88, 4604. 6. F. L. Jiang, G. W. Wei, Z. Y. Huang, X. J. Lei, M. C. Hong, B. S. Kang and H. Q. Liu, J. Coord. Chem. 1992, 25, 183. 7. G. W. Wei, M. C. Hong, Z. Y. Huang and H. Q. Liu, J. Chem. Soc., Dalton Trans. 1991, 3145.
8. B. S. Kang, J. H. Peng, M. C. Hong, D. X. Wu, X. T. Chen, L. H. Weng, X. J. Lei and H. Q. Liu, J. Chem. Soc., Dalton Trans. 1991, 2897. 9. G. W. Wei, H. Q. Liu, Z. Y. Huang, M. C. Hong, L. R. Huang and B. S. Kang, Polyhedron 1991, 10, 553. 10. G. W. Wei, H. Q. Liu, Z. Y. Huang, L. R. Huang and B. S. Kang, J. Chem. Soc., Chem. Commun. 1989, 1839. 11. Y. H. Hu, L. H. Weng, L. R. Huang, X. T. Chen, D. X. Wu and B. S. Kang, Acta Cryst. 1991, C47, 2655. 12. Y. H. Hu, X. T. Chen, L. Dai, L. H. Weng and B. S. Kang, Jeigou Huaxue 1993, 12, 38. 13. X. T. Chen, Y. H. Hu, D. X. Wu, L. H. Weng and B. S. Kang, Polyhedron 1991, 10, 2651. 14. J. D. Lydon, R. C. Elder and E. Deutsch, Inorg. Chem. 1982, 21, 3186. 15. P. B. Hitchcock and G. M. McLanghlin, J. Chem. Soc., Dalton Trans. 1976, 1929. 16. W. Levason, J. S. Ogden and M. D. Spicer, Inorg. Chem. 1989, 28, 2128. 17. R. A. Jones and A. R. Katritzsky, J. Chem. Soc., 1960, 2937. 18. R. M. Silverstein and G. C. Bassler, Spectrometric Identification of Organic Compounds, p. 85. John Wiley and Sons, New York (1964). 19. R. H. Holm and F. A. Cotton, J. Chem. Phys. 1960, 32, 1168. 20. F. A. Cotton and M. Goodgame, J. Am. Chem. Soc. 1961, 83, 1177. 21. F. A. Cotton, O. D. Faut, D. M. L. Goodgame and R. H. Holm, J. Am. Chem. Soc. 1961, 83, 1780. 22. R. W. Lane, J. A. Ibers, R. B. Frankel, G. C. Papaefthymiou and R. H. Holm, J. Am. Chem. Soc. 1977, 99, 84, 23. J. R. Dorfman, Ch. P. Rao and R. H. Holm, Inorg. Chem. 1985, 24, 453.