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Some carbonyl halide complexes of manganese(I) and rhenium(I) containing trithiophosphite ligands
321
Journal of Organometallic Chemistry. 0 Elsevier Sequoia S.A., Susanne -
91 (1975) 321-326 Printed in The Netherlands
SOME CARBONYL HALIDE COMPLEXES OF MANGANESE(l) RHENIUM(i) CONTAINTNG TRITHIOPHOSPHIT’E LIGANDS
JAMES R. WAGNER Clippinger
AND
and DAVID G. HENDRICICER
Laboratories,
Department
of Chemistry,
Ohio
University.
A thens.
Ohlo
45 i0 I (US-A
(Received December 17th. 1974)
Summary The reaction of trithiophosphites, P(SR)s (R = CHa, C2H, and C, H5 ), with M(C0)5X (M = Mn, Kc, X = Cl, Br) yields complexes of the gene4 formula M(CO),P(SR),X and M(CO),[P(SR),]2X. The geometry of the disubstituted complexes is established from infrared and PMR spectroscopy to be fat-Re(CO)s[ P(SR),],X and mer-[ truns- (P(SR),} 2Mn(CO)3X] while all M(CO),P(SR)sX compounds are found to be cis. From a comparison of the v(C0) absorptions of the trithiophosphite complexes with analogous compounds containing phosphites, phosphines and aminophosphines, the order P(SR)s > P(OR)a > P(NR& > PRs is obtained.
lntroduc tion Although transition metal complexes of phosphines [ 1,2], phosphites [ 31 and aminophosphines [3] number well into the tens of thousands, less than two dozen complexes which contain trithiophosphites, P(SR),, have been reported [ 3,4] _ Of these few compounds, only about one quarter have been adequately characterized [5,3]. This is somewhat surprising in view of the facile methods of synthesis for an extensive number of trithiophosphites and the reported applicability of these ligands as stabilizers for lubricating oils and polyolefins [4]. In the light of this and the lack of data !rom which an evaluation of the influence of the SR moiety on the bonding properties of a tricovalent phosphorus may be made, we have prepared and characterized several complexes of Mnr and Rer carbonyl halides which contain P(SCH,)a, P(SC,H,), and P(SC,H6)a_ Results
and discussion
A major difficulty encountered in the preparation of many metal complexes of trithiophosphites is their relatively rapid decomposition, particularly in solution, to yield stable metal sulfides. The diamagnetic complexes reported herein
.)
322 are stable as solids for up to two weeks. However, in CHCI, or CC14 solution they decompose completely within a few hours. Table 1 contains the infrared and PMR data for 15 new complexes, fom of which have been characterized only from theh infrared spectra. Attempts to obtain these materials in the Pure state employing column chromatography were thwarted by decomposition. The infrared spectra of the M(C0)4LX complexes exhibit the four absorptions of appropriate intensity ~II the u(C0) region expected for a cis-configuration (c, symmetry) which is most common when L is a phosphine, phosphite or an aminophosphine [‘i-lo]. For the M(CO)sLzX complexes there are three possible geometries: fat (C, symmetry), mer with trans L’s (C, symmetry), mer with cis L’s (C, symmetry). The rhenium comple.ues eshibit the three strong v(C0) absorptions reported for numerous complexes possessing the The three CO absorptions of weak, strong and medium intensity observed for the manganese compounds are characteristic of a mer comples having a tram ligand arrangement [7,14,15]. Themes compound (CsHs)Mn(CO)s(diphos), which of necessity contains &-phosphorus atoms, is reported to show only two v(C0) absorptlons [ 161. The Crans-directing ability of the trithiophosphite ligands favors the formation of fat-Mn(C0)aL2X. However, compounds of this type when L = phosphite or phosphine have been shown to isomerize rapidly to yield the sterically less hindered trans-Mn(CO)aL,X [7,14]. Thus with P(SR),, which is more bulky than corresponding phosphites, and at the temperature used in preparation, the isolation of truns-Mn(CO)a[ P(SR)a] aX is expected. The preference of Re(CO)aLaX compleses for the fat form may, in part, be attributed to the decrease in steric interaction between ligands bound to the large Re atom [ 121. From Tabie 1 it can be seen that for similar complexes wherein only the R group of the trithiophosphite is varied, the positions of the v(C0) absorptions follow the order P(SCsHj)s > P(SCH,), > P(SC,H,), . A similar trend was observed in numerous complexes containing phosphites and phosphines and may be correlated with the electronic effect of the R group [5]. A comparison of the v(C0) positions of the trithiophosphite complexes with analogous ones containing phosphines [7,9,12,14,15,17,19], aminophosphine [lo] and phosphites [7,12,14,18] yieids the following frequency order: P(SR), > P(OR), > P(NRa)a > PR3. The arguments concerning the implication of this order with respect to the o and R bonding abilities of ligands have been adequately discussed elsewhere [5,20]_ Previously it has been shown that the R and u bonding capacity of is greater than P(OCH,),CC,H,,, using the treatment of Graham P(SCH~)~CCSH,, [51- The Y(CO) absorptions of Mo(CO)~P(SCH~)~ [6] occur at higher energy than for Mo(CO),P(GCHs)s. Our data and those of Keiter and Verkade [ 51 support the idea that in bonding ability towards metals in low oxidation states, P(SR), > P(OR)s where R is the same moiety. Further evidence in support of the assigned geometries is obtained from the PMR spectra. The occurrence of a large amount of virtual spin-pin coupling when two phosphorus ligands are Crans across a metal center is well established ]21-231. The obmwnce of a sharp 1/2/l triplet for the Mn(CO)a [P(SCHs)s]sx complexes supports the proposed bans ligand arrangement. For the fucWC0)3[WCH3)312X compounds a multiplet of severai lines with the outer two being of greatest intensity (l/=0.8/1) is detected. This pattern, which mdi-
3’23
i. f
_.__.
. ..-..-
4 B.p 20-4o”C. IJ Not
i~ohtcd
Mn(CO)JIwCrjH5)3l~cI _-_.--_-._.- -__-
____
Compound
b/l 2/l
G/l G/l 511
611 5/l 1011 1011 3/l
III ~1 pure
_.. form.
-_.-
__
.--- - .. .. _
l/l l/l 2/l 211
..-. _-.__
--.
. -....
ILcucllon rlmc (I\)
-._
..-_
cc14
cc14
CI,HI,
.
_.
. -.
----
C
(16.74) (lG.67) (24.63) (23.13)
(38.17) (313.86)
(28.70)
2”#“’ (27aB2) _--__-__-_-
20.72 (20.83) 19.32 (19.66) 29.GG (29.87)
1G.BB 16.07 24.63 23.20 b
38.40 36.60
28.92 .!I
.--__ -_._----_I_________
----
_--I -_------
(2.79) (2.61) (4.12) (3.89)
3/1G (3.40) 3.16 (3.19) G-00 (6.02) 4.64 (&67)
2.80 2.66 4.13 3.A2
2.30 (2.18) 2.04 (2.06)
3.G7 (3.63)
II
Annly UcnJ dntn found (culcd.) (%I) ~_--
-_ . ..- --.-_--
CHCIJ-heximc pet. ether wt. cthor-hcxnnc .--_ ._._ _.-
PCnlllIX
prntnnc
2 1 2 24 2
cc14
cc14
ccl.1 cc14 24
rthcr cthcr Del. cthcr pet. ether cthher
12 2 2
cc14 cc14
cc14
rolvenL
__.
CIlCI>-hrxwe PCI. Cllld pet. cthcr-liexnne pet. rther-hcxnne
I’rcclpllutln~
2 2
._
..
--_-___
- ._ . . -
cc14
.- ____.. - _ ._____.7 CCL1 1 cc13
Solvcnl
.. -.
._._. --
Mole rntlo RSR)~ IM(CO)s x
daul
DATA .__. .__..--.-
PmPumllvc --_-_
PREPARATIVE AND ANALYTICAL - .-_-.-....-.-.--
TABLE 2
--
Ornnec Ornnge Ornnge Orongo Crcum
White Whrro Whlto Whll0 Whlre
Orungc whlre Groom Crenm
Color
cates a small degree of P-P coupling, is typical of cis-phosphorus Iigands and thus substantiates the geometry assigned on the basis of u(C0) data. For the trans-Mn(CO)3[P(SC,H5),]2X complexes the CH2 or a-proton resonance which occurs as a quintuplet for the free ligand has coalesced to yield a broad single absorption_ The PMR spectra of the fat-Re(CO),[ P(SC2H5)J 2X compounds eshibit a quintuplet with measurable absorbance between the peaks, similar to that reported for Ni[ P(OCzH5)3]4 [21]. The deshielding of the cr-protons of P(SC2H5)3 and P(CH,), on comples formation and the increase in J(PSCH) is jzypical of other phosphorus donor tigands [ 31. Experimental Infrared spectra were recorded for chloroform solutions contained in a 0.2 mm NaCl cell using a Perkin-Elmer Model 621 spectrophotometer and were calibrated against polystyrene film. The PMR spectra were recorded for saturated deuteriochloroform solution which contained tetramethylsilane as an Internal reference using a Var~an HA-100 spectrometer. Mass spectra were recorded using a Hitachi-Perkin-Elmer RMUGE spectrometer operating at an ionization voltage of 80 eV. Carbon and hydrogen compositions were ascertained by combustion employing a F and M C-H-N Analyzer hfodel 185. Published methods were followed for the preparation of the M(CO)sX compounds where M = Mn, Re; X = Cl, Br [24,25]. Trimethyl and triethyl trithlo-
phosphite were prepared by heating to 50°C an acetone solution which contained the appropriate dialkyl disuifide (0.8 mol), yellow phosphorus (0.5 mol) and 1 ml of 15 IV KOH [26]. Triphenyl trithiophosphite was obtained from the reaction of phosphorus trichloride (0.2 mol) with an excess of thiophenol (0.8 mol) at 65°C [27]. The purity of the ligands was verified by their boiling or melting points, PMR spectra, mass spectra and carbon, hydrogen analysis (Table 2). Since the ligands are nosious and their toxicity levels have not been established, appropriate caution should be observed when handling these materials or their compleses. For the preparation of the complexes, a procedure similar to the one given below was used. Any variation in detail of the preparations is given, along with the analytical data for the compounds, in Table 2. fat-Bromotncarbonylbis( trimethyltrithiophosphite)rhenium(i) To 0.41 g (1.0 mmol) of bromopentacarbonylrhenium(1)
tetrachloride solution
was added
1 ml (5.0 mmoi) of trimethyl 2 h under to
was reflused
temperature and tion. addition
helium atmosphere,
of
original
in 25 ml of carbon
trithiophosphite. it
by
of 10 ml of diethyl ether to this was on filter, washed and dried in vacua 24 h.
of
After t.he
cooled
to room
evapora-
the 5 ml of
Acknowledgment
The
wish to
Research
Committee
the support
this work
the Ohio
316
References 1 G. Booth. h G.M. Kosolapoff and L. btaier (Ed%). Organopbosphorus fnterscience. New York. 1972. PP. 134-545. 2 C.A. McAuliffe. Transition Me&J Complexes of Phosphorus. Arsenic 3 4 6 6 7 8
9 10 11
12 13
Compound% and Antimony
VoL
f. Wiley-
f&and%
John
Wiley. New York. 1973. J.G. Verkade and K-J. Co&ran. in GM. Kosolapoff and L Maier (Eds.). Orgaoo~hospborus Com~ou~ds. Vol -?. Wiley-Intersclence. New York. 1972, pp I-188. W. Gem ad H_iR Hudsoo in G.M. Kosolapoff and L. Tier (Ed%). OrxzanoPhospborus ComP-ds. VoLV. Wiley-Interscience. New York, 1973. pp 21-329. RL. Keiierand J.G. Verkade. Inorg. Chem.. 8 (1969) 2115. R. hLtbieu. hf. L-eon and Ft. Poilblanc. Laorg. Chem.. 2 (1970) 2030. R.J. Ang=lici and F. Basolo. J. Amer. Chem. Sot.. 84 (1962) 2495. R.J. Angelia and F. Basolo. lnonz. Chem.. 2 (1963) 728. F. Zmgzdes. U. Sartorelh. F. Canziam and LL Rave&a. Inor& Chem.. 6 (1967) 154. R.B. King and T.F. Koreoowski. J. OrganometaL Chem.. 17 (1969) 95. F. Zingales. V. Sartorelh and A. Trovati. Ioorg. Chere. 6 (1967) 1246. EW. Abel and S.P. Tyfield. Caa J. Chem_. 47 (1969) 4627. E Singfetoa. J.T. Moelwyn-Hughes axed A.W.B. Gamer. J. OrgsnomeLal. Cbem.. 21 (1970) 449.
14 R.J. Angelici. F. Basolo and A.J. Poe. J. Amer. Chem. SOL. 85 (1963) 2215. 15 AG. Osborne and M.H.B. Stiddard. J. Cbem. Sot.. 11962) 4715. 16 W.D. Bannixter. B.L. Boo&. BI. Greea and R.N. Haseldine. J. Cbem. Sot. A. (1969) 698. 17 RH.Reimano and E. Smgleton. J. Organometal. Chem.. U (1972) C18. 18 B.L. Booti and R.N. Haszeldme. J. Chem. Sot. A. (1966) 159. 19 J.T. Moelwyn-Hughes. kW.B. Garner and AS. Howard. J. Chem. Sot. A. (1971) 2370. 20 S-0. Gtim acd D.A Wheallaod. lnorg. Chem.. 8 (1369) 1716 and references therein.
Journal of Organometallic Chemistry. 0 Elsevier Sequoia S.A., Susanne -
91 (1975) 321-326 Printed in The Netherlands
SOME CARBONYL HALIDE COMPLEXES OF MANGANESE(l) RHENIUM(i) CONTAINTNG TRITHIOPHOSPHIT’E LIGANDS
JAMES R. WAGNER Clippinger
AND
and DAVID G. HENDRICICER
Laboratories,
Department
of Chemistry,
Ohio
University.
A thens.
Ohlo
45 i0 I (US-A
(Received December 17th. 1974)
Summary The reaction of trithiophosphites, P(SR)s (R = CHa, C2H, and C, H5 ), with M(C0)5X (M = Mn, Kc, X = Cl, Br) yields complexes of the gene4 formula M(CO),P(SR),X and M(CO),[P(SR),]2X. The geometry of the disubstituted complexes is established from infrared and PMR spectroscopy to be fat-Re(CO)s[ P(SR),],X and mer-[ truns- (P(SR),} 2Mn(CO)3X] while all M(CO),P(SR)sX compounds are found to be cis. From a comparison of the v(C0) absorptions of the trithiophosphite complexes with analogous compounds containing phosphites, phosphines and aminophosphines, the order P(SR)s > P(OR)a > P(NR& > PRs is obtained.
lntroduc tion Although transition metal complexes of phosphines [ 1,2], phosphites [ 31 and aminophosphines [3] number well into the tens of thousands, less than two dozen complexes which contain trithiophosphites, P(SR),, have been reported [ 3,4] _ Of these few compounds, only about one quarter have been adequately characterized [5,3]. This is somewhat surprising in view of the facile methods of synthesis for an extensive number of trithiophosphites and the reported applicability of these ligands as stabilizers for lubricating oils and polyolefins [4]. In the light of this and the lack of data !rom which an evaluation of the influence of the SR moiety on the bonding properties of a tricovalent phosphorus may be made, we have prepared and characterized several complexes of Mnr and Rer carbonyl halides which contain P(SCH,)a, P(SC,H,), and P(SC,H6)a_ Results
and discussion
A major difficulty encountered in the preparation of many metal complexes of trithiophosphites is their relatively rapid decomposition, particularly in solution, to yield stable metal sulfides. The diamagnetic complexes reported herein
.)
322 are stable as solids for up to two weeks. However, in CHCI, or CC14 solution they decompose completely within a few hours. Table 1 contains the infrared and PMR data for 15 new complexes, fom of which have been characterized only from theh infrared spectra. Attempts to obtain these materials in the Pure state employing column chromatography were thwarted by decomposition. The infrared spectra of the M(C0)4LX complexes exhibit the four absorptions of appropriate intensity ~II the u(C0) region expected for a cis-configuration (c, symmetry) which is most common when L is a phosphine, phosphite or an aminophosphine [‘i-lo]. For the M(CO)sLzX complexes there are three possible geometries: fat (C, symmetry), mer with trans L’s (C, symmetry), mer with cis L’s (C, symmetry). The rhenium comple.ues eshibit the three strong v(C0) absorptions reported for numerous complexes possessing the The three CO absorptions of weak, strong and medium intensity observed for the manganese compounds are characteristic of a mer comples having a tram ligand arrangement [7,14,15]. Themes compound (CsHs)Mn(CO)s(diphos), which of necessity contains &-phosphorus atoms, is reported to show only two v(C0) absorptlons [ 161. The Crans-directing ability of the trithiophosphite ligands favors the formation of fat-Mn(C0)aL2X. However, compounds of this type when L = phosphite or phosphine have been shown to isomerize rapidly to yield the sterically less hindered trans-Mn(CO)aL,X [7,14]. Thus with P(SR),, which is more bulky than corresponding phosphites, and at the temperature used in preparation, the isolation of truns-Mn(CO)a[ P(SR)a] aX is expected. The preference of Re(CO)aLaX compleses for the fat form may, in part, be attributed to the decrease in steric interaction between ligands bound to the large Re atom [ 121. From Tabie 1 it can be seen that for similar complexes wherein only the R group of the trithiophosphite is varied, the positions of the v(C0) absorptions follow the order P(SCsHj)s > P(SCH,), > P(SC,H,), . A similar trend was observed in numerous complexes containing phosphites and phosphines and may be correlated with the electronic effect of the R group [5]. A comparison of the v(C0) positions of the trithiophosphite complexes with analogous ones containing phosphines [7,9,12,14,15,17,19], aminophosphine [lo] and phosphites [7,12,14,18] yieids the following frequency order: P(SR), > P(OR), > P(NRa)a > PR3. The arguments concerning the implication of this order with respect to the o and R bonding abilities of ligands have been adequately discussed elsewhere [5,20]_ Previously it has been shown that the R and u bonding capacity of is greater than P(OCH,),CC,H,,, using the treatment of Graham P(SCH~)~CCSH,, [51- The Y(CO) absorptions of Mo(CO)~P(SCH~)~ [6] occur at higher energy than for Mo(CO),P(GCHs)s. Our data and those of Keiter and Verkade [ 51 support the idea that in bonding ability towards metals in low oxidation states, P(SR), > P(OR)s where R is the same moiety. Further evidence in support of the assigned geometries is obtained from the PMR spectra. The occurrence of a large amount of virtual spin-pin coupling when two phosphorus ligands are Crans across a metal center is well established ]21-231. The obmwnce of a sharp 1/2/l triplet for the Mn(CO)a [P(SCHs)s]sx complexes supports the proposed bans ligand arrangement. For the fucWC0)3[WCH3)312X compounds a multiplet of severai lines with the outer two being of greatest intensity (l/=0.8/1) is detected. This pattern, which mdi-
3’23
i. f
_.__.
. ..-..-
4 B.p 20-4o”C. IJ Not
i~ohtcd
Mn(CO)JIwCrjH5)3l~cI _-_.--_-._.- -__-
____
Compound
b/l 2/l
G/l G/l 511
611 5/l 1011 1011 3/l
III ~1 pure
_.. form.
-_.-
__
.--- - .. .. _
l/l l/l 2/l 211
..-. _-.__
--.
. -....
ILcucllon rlmc (I\)
-._
..-_
cc14
cc14
CI,HI,
.
_.
. -.
----
C
(16.74) (lG.67) (24.63) (23.13)
(38.17) (313.86)
(28.70)
2”#“’ (27aB2) _--__-__-_-
20.72 (20.83) 19.32 (19.66) 29.GG (29.87)
1G.BB 16.07 24.63 23.20 b
38.40 36.60
28.92 .!I
.--__ -_._----_I_________
----
_--I -_------
(2.79) (2.61) (4.12) (3.89)
3/1G (3.40) 3.16 (3.19) G-00 (6.02) 4.64 (&67)
2.80 2.66 4.13 3.A2
2.30 (2.18) 2.04 (2.06)
3.G7 (3.63)
II
Annly UcnJ dntn found (culcd.) (%I) ~_--
-_ . ..- --.-_--
CHCIJ-heximc pet. ether wt. cthor-hcxnnc .--_ ._._ _.-
PCnlllIX
prntnnc
2 1 2 24 2
cc14
cc14
ccl.1 cc14 24
rthcr cthcr Del. cthcr pet. ether cthher
12 2 2
cc14 cc14
cc14
rolvenL
__.
CIlCI>-hrxwe PCI. Cllld pet. cthcr-liexnne pet. rther-hcxnne
I’rcclpllutln~
2 2
._
..
--_-___
- ._ . . -
cc14
.- ____.. - _ ._____.7 CCL1 1 cc13
Solvcnl
.. -.
._._. --
Mole rntlo RSR)~ IM(CO)s x
daul
DATA .__. .__..--.-
PmPumllvc --_-_
PREPARATIVE AND ANALYTICAL - .-_-.-....-.-.--
TABLE 2
--
Ornnec Ornnge Ornnge Orongo Crcum
White Whrro Whlto Whll0 Whlre
Orungc whlre Groom Crenm
Color
cates a small degree of P-P coupling, is typical of cis-phosphorus Iigands and thus substantiates the geometry assigned on the basis of u(C0) data. For the trans-Mn(CO)3[P(SC,H5),]2X complexes the CH2 or a-proton resonance which occurs as a quintuplet for the free ligand has coalesced to yield a broad single absorption_ The PMR spectra of the fat-Re(CO),[ P(SC2H5)J 2X compounds eshibit a quintuplet with measurable absorbance between the peaks, similar to that reported for Ni[ P(OCzH5)3]4 [21]. The deshielding of the cr-protons of P(SC2H5)3 and P(CH,), on comples formation and the increase in J(PSCH) is jzypical of other phosphorus donor tigands [ 31. Experimental Infrared spectra were recorded for chloroform solutions contained in a 0.2 mm NaCl cell using a Perkin-Elmer Model 621 spectrophotometer and were calibrated against polystyrene film. The PMR spectra were recorded for saturated deuteriochloroform solution which contained tetramethylsilane as an Internal reference using a Var~an HA-100 spectrometer. Mass spectra were recorded using a Hitachi-Perkin-Elmer RMUGE spectrometer operating at an ionization voltage of 80 eV. Carbon and hydrogen compositions were ascertained by combustion employing a F and M C-H-N Analyzer hfodel 185. Published methods were followed for the preparation of the M(CO)sX compounds where M = Mn, Re; X = Cl, Br [24,25]. Trimethyl and triethyl trithlo-
phosphite were prepared by heating to 50°C an acetone solution which contained the appropriate dialkyl disuifide (0.8 mol), yellow phosphorus (0.5 mol) and 1 ml of 15 IV KOH [26]. Triphenyl trithiophosphite was obtained from the reaction of phosphorus trichloride (0.2 mol) with an excess of thiophenol (0.8 mol) at 65°C [27]. The purity of the ligands was verified by their boiling or melting points, PMR spectra, mass spectra and carbon, hydrogen analysis (Table 2). Since the ligands are nosious and their toxicity levels have not been established, appropriate caution should be observed when handling these materials or their compleses. For the preparation of the complexes, a procedure similar to the one given below was used. Any variation in detail of the preparations is given, along with the analytical data for the compounds, in Table 2. fat-Bromotncarbonylbis( trimethyltrithiophosphite)rhenium(i) To 0.41 g (1.0 mmol) of bromopentacarbonylrhenium(1)
tetrachloride solution
was added
1 ml (5.0 mmoi) of trimethyl 2 h under to
was reflused
temperature and tion. addition
helium atmosphere,
of
original
in 25 ml of carbon
trithiophosphite. it
by
of 10 ml of diethyl ether to this was on filter, washed and dried in vacua 24 h.
of
After t.he
cooled
to room
evapora-
the 5 ml of
Acknowledgment
The
wish to
Research
Committee
the support
this work
the Ohio
316
References 1 G. Booth. h G.M. Kosolapoff and L. btaier (Ed%). Organopbosphorus fnterscience. New York. 1972. PP. 134-545. 2 C.A. McAuliffe. Transition Me&J Complexes of Phosphorus. Arsenic 3 4 6 6 7 8
9 10 11
12 13
Compound% and Antimony
VoL
f. Wiley-
f&and%
John
Wiley. New York. 1973. J.G. Verkade and K-J. Co&ran. in GM. Kosolapoff and L Maier (Eds.). Orgaoo~hospborus Com~ou~ds. Vol -?. Wiley-Intersclence. New York. 1972, pp I-188. W. Gem ad H_iR Hudsoo in G.M. Kosolapoff and L. Tier (Ed%). OrxzanoPhospborus ComP-ds. VoLV. Wiley-Interscience. New York, 1973. pp 21-329. RL. Keiierand J.G. Verkade. Inorg. Chem.. 8 (1969) 2115. R. hLtbieu. hf. L-eon and Ft. Poilblanc. Laorg. Chem.. 2 (1970) 2030. R.J. Ang=lici and F. Basolo. J. Amer. Chem. Sot.. 84 (1962) 2495. R.J. Angelia and F. Basolo. lnonz. Chem.. 2 (1963) 728. F. Zmgzdes. U. Sartorelh. F. Canziam and LL Rave&a. Inor& Chem.. 6 (1967) 154. R.B. King and T.F. Koreoowski. J. OrganometaL Chem.. 17 (1969) 95. F. Zingales. V. Sartorelh and A. Trovati. Ioorg. Chere. 6 (1967) 1246. EW. Abel and S.P. Tyfield. Caa J. Chem_. 47 (1969) 4627. E Singfetoa. J.T. Moelwyn-Hughes axed A.W.B. Gamer. J. OrgsnomeLal. Cbem.. 21 (1970) 449.
14 R.J. Angelici. F. Basolo and A.J. Poe. J. Amer. Chem. SOL. 85 (1963) 2215. 15 AG. Osborne and M.H.B. Stiddard. J. Cbem. Sot.. 11962) 4715. 16 W.D. Bannixter. B.L. Boo&. BI. Greea and R.N. Haseldine. J. Cbem. Sot. A. (1969) 698. 17 RH.Reimano and E. Smgleton. J. Organometal. Chem.. U (1972) C18. 18 B.L. Booti and R.N. Haszeldme. J. Chem. Sot. A. (1966) 159. 19 J.T. Moelwyn-Hughes. kW.B. Garner and AS. Howard. J. Chem. Sot. A. (1971) 2370. 20 S-0. Gtim acd D.A Wheallaod. lnorg. Chem.. 8 (1369) 1716 and references therein.