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Organoimido complexes of Mo(IV), Mo(V) and Mo(VI): preparation, structure and reactivity
Polyhedron Vol. 5, No. l/Z, pi. 301-304, Printed in Great Britain
1986 0
0277-5387j86 1986 Pqmon
S3.00+ Prcs
.OO Ltd
ORGANOIMIDO COMPLEXES OF MO(W), MO(v) AND MO(W): PREPARATION, STRUCTURE AND REACTIVITY C. Y. CHOU,
D. D. DEVORE,
S. C. HUCKETT
and E. A. MAATTA*
Department of Chemistry, Kansas State University, Manhattan, KS 66506, U.S.A. J. C. HUFFMAN Molecular Structure Center, Indiana University, Bloomington, IN 47405, U.S.A. and F. TAKUSAGAWA Department of Chemistry, University of Kansas, Lawrence, KS 66045, U.S.A. (Received 12 June 1985)
Abstract-Two series of p-tolylimido (Ntol) complexes of Mo(VI), MO(V) and Mo(IV) are described. One series, containing diethyldithiocarbamate ligands, is formed via oxygen atom abstraction from Mo(VI)O(Ntol)(SzCNEtz)z using tertiary phosphines which affords the oxo-bridged MO(V) dimer [Mo(Ntol)(SzCNEt2)2]z0 and the Mo(IV) species Mo(Ntol&CNEt,),. In solution, the Ma(V) dimer participates in a disproportionation equilibrium affording the Mo(V1) and Mo(IV) complexes. Mo(Ntol)(S&NEtz)z reacts with O2 to regenerate MoO(Ntol)(S,CNEt,),, thus completing a catalytic phosphine oxidation cycle. Mo(Ntol)(S,CNEt& also reacts with MezSO to yield the Mo(V1) complex and Me,S, and with dimethylacetylenedicarboxylate to yield the alkyne complex, Mo(Ntol)(DMAC)(S,CNEt,)2. The second series of p-tolylimido complexes contains chloride and phosphine co-ligands and derives from the Mo(V1) species Mo(Ntol)Cl,(THF). In the presence of tertiary phosphines, this complex undergoes reduction to afford monomeric MO(V) complexes of the form Mo(Ntol)Cl,L, (L = Ph,P, EtPh,P and Me,P; L, = Ph2PC2H4PPh2). The bis(monodentate phosphine) complexes possess the trans, mergeometry while the diphos complex is assigned the cis, mer-configuration. Reduction of Mo(Ntol)C1,(Me,P)z by Na-Hg in the presence of Me,P affords the Mo(IV)complex cis, merMo(Ntol)Cl,(Me,P), whose molecular structure is described.
In recent years, an increasing research effort has been focused on transition-metal complexes bearing organoimido ligands (NR), and it is now clear that such species are of importance and utility in a diverse array of processes ranging from synthetic procedures (e.g. the amination,’ aziridinatior? and metathesis3 of olefins) to biological functions (e.g. metabolism of certain hydrazines4). Molybdenum organoimido complexes are of additional interest in that they may
* Author to whom correspondence should be addressed.
serve as models of the {Mo(NH)} species that are likely intermediates in nitrogen fixation’ and in the ammoxidation of propylene.‘j Most of the organoimido molybdenum complexes prepared to date are Mo(V1) species.7 Herein we describe two series of ptolylimido complexes of Mo(VI), M(V) and Mo(IV). One series, containing diethyldithiocarbamate ligands, displays prominent oxygen atom transfer reactivity; the second series, containing chloride and phosphine ligands, is characterized by facile oxidation and reduction reactions.
301
C. Y. CHOU et al.
302
RESULTS
AND
DISCUSSION
Dithiocarbamate complexes
The reaction of the p-tolylimido Mo(VI) species MoO(Ntol)L, (L = S,CNEt,) with 0.5 equivalents of Ph,P or EtPh,P in CH,C& produces the corresponding phosphine oxide and a dinuclear MO(V) complex Mo,O(Ntol),L, [eqn (l)] :s MoO(Ntol)L,
+0.5R,P + Mo,O(Ntol),L,
+ 0.5R,PO.
(1)
Two core structures, A and B, are conceivable for the MO(V) dimer ; the oxo-bridged structure A is
Solutions of Mo(Ntol)L, react rapidly with O2 (1 atm) at ambient temperature to regenerate MoO(Ntol)L, [eqn (4)] : Mo(Ntol)L, +$02 + MoO(Ntol)L,.
(4)
Thus, taken collectively, eqns (l), (3) and (4) constitute a catalytic phosphine oxidation cycle. We have observed the oxidation of ca 50 equiv. of PPh, using this system without any diminution of catalytic activity. Mo(Ntol)L, solutions also react with dimethylsulfoxide to afford MoO(Ntol)L, and dimethyl sulfide [eqn (5)] : Mo(Ntol)L, + Me,SO + MoO(Ntol)L, indicated by IR data [absence of v(Mo=O)] and 1‘0 NMR studies [S( “0) = 1002 ppm]. The electronic spectrum of (Mo(Ntol)L,),O in toluene displays an intense absorption at 533 nm, a region characteristic of mono-oxo-bridged MO(V) dimers.g However, this band does not obey Beer’s law, a result which by analogy to the behavior of the corresponding Mo203L, system,” suggests the occurrence of the disproportionation equilibrium shown in eqn (2) :
Chloride and phosphine species
The reaction of p-tolylazide with MoCl,(THF), (THF = tetrahydrofuran) in 1,Zdichloroethane the p-tolylimido Mo(V1) species provides Mo(Ntol)Cl,(THF) in excellent yield [eqn (611:12 MoCl,(THF),
+ p-tolN, + Mo(Ntol)Cl,(THF)
e
K
MoO(Ntol)L, (2)
2 +
Mo(Ntol)L,
In support of this proposition, we find that toluene solutions of [Mo(Ntol)LJzO react with EtPhzP to produce EtPh,PO and the reactive 16-electron Mo(IV) species Mo(Ntol)L, [eqn (311: [Mo(Ntol)L,],O
f EtPhzP + 2Mo(Ntol)L, + EtPh,PO.
(3)
Although we have not isolated a pure sample of Mo(Ntol)L,, we have been able to probe its reactivity in solution. Thus, when the reaction of eqn (3) is conducted in the presence of an excess of the activated alkyne dimethylacetylenedicarboxylate (DMAC), the bright yellow alkyne complex Mo(Ntol)(DMAC)L, is formed. Solution ‘H NMR results and an X-ray diffraction study” confirm the expected pentagonal bipyramidal geometry for this species (C).
+ Me,S. (5)
+ N,.
(6)
The molecular structure of this 16-electron species features a short MO-N bond [1.717(3) A] and a near-linear MO-N-C bond angle [174.5(3)“], consonant with the presence ofa triply-bonded, fourelectron donor tolylimido ligand. The MO-O bond length of 2.234(3) A for the THF molecule suggests that the tolylimido ligand exerts a trans-influence of ca 0.2 A in this complex. The reaction of Mo(Ntol)Cl,(THF) with various tertiary phosphines (L) in 1,Zdichloroethene solutioninducesreductionofthemetalandaffordsptolylimido Ma(V) complexes of the form Mo(Ntol)Cl,L, [eqn (7)] :13 Mo(Ntol)Cl,(THF)
+ 2L + Mo(Ntol)Cl,L,,
(7)
where L = Ph,P, EtPh,P or Me,P; and LZ = Ph,PC2H4PPh2. These 17-electron~monomeric d’ complexes are air-stable in the solid state and display. magnetic moments near the spin-only value structure of 0f 1.73 clg. The molecular pseudodisplays a Mo(Ntol)Cl,(EtPh,P), octahedral &ordination about the MO atom, with a
Organoimido complexes of MO(W), MO(V) and MO(W) meridional arrangement of the chlorine atoms and a trans-disposition of the phosphine ligands. Thus, the overall geometry is similar to that previously found for the analogous Re and W complexes,
Mo(Ntol)Cl,(Me,P),
[eqn (9)] :
Mo(Ntol)Cl,(Me,P),
+ Me3P + Na-Hg -+ Mo(Ntol)Cl,(Me,P),.
303
(9)
A meridional arrangement of the Me3P ligands is indicated by NMR spectroscopy. In the ‘H spectrum, the methyl protons of the Me,P groups and appear as a triplet (6 1.42, JHp = 3.6 Hz, 18 H) and a doublet (6 1.28, J, = 7.8 Hz, 9 H), while the 31P{‘H) spectrum consists of a triplet at 6 5.38 Solutions of the Mo(Ntol)Cl,L, complexes give rise (J,, = 18.1 Hz; area 1) and a doublet at 6 -7.32 to sharp ESR spectra at room temperature. The [J,, = 18.1 Hz (area 2)]. spectra of the Ph,P, EtPh,P and Me,P complexes The molecular structure of Mo(Ntol)Cl,(Me,P), are very similar and reveal superhyperfine coupling has been determined. A drawing of the molecule is to two equivalent 31P nuclei, consistent with their shown in Fig. 1 and selected bond lengths and angles expected trans, mer-geometry. The ESR spectrum of are given in Table 1. The pseudo-octahedral the chelating diphos complex, however, shows structure features the expected meridional configurstrong coupling to only one 31P nucleus: since the ation of the Me3P ligands with the chlorine atoms unpaired electron is expected to reside in the occupying mutually cis-positions. Perhaps the most formally non-bonding MO &,-orbital, the cis, mersalient aspect of the structure is the absence of a geometry is indicated for this species. trans-influence exerted by the tolylimido ligand : the The phosphine ligands in Mo(Ntol)Cl,(EtPh,P), trans MO-Cl(3) bond distance of2.497(1) A is in fact can be substituted by the corresponding phosphine ca 0.03 A shorter than the cis MO-Cl(2) distance oxide [eqn (811: [2.525(l) A]. This small lengthening of MO-Cl(2) can be ascribed to the trans-influence of the Me,P Mo(Ntol)Cl,(EtPh,P), +2EtPh2P0 ligand which is also evidenced by the MO-P bond -, Mo(Ntol)Cl,(OPEtPh,),. (8) lengths: the pair of mutually trans phosphines display identical MO-P distances of 2.509(l) A ESR evidence suggests that the trans, mer-geometry while the MO-P(~) bond length is ca 0.04 A shorter is maintained for the bis(phosphine oxide) complex. at 2.471(l) A. When a toluene solution containing either Mo(Ntol)Cl,(EtPh,P), or Mo(Ntol)Cl,(OPEtPh,), is exposed to moist air, crystals of the Mo(V1) complex [MoO&l,(OPEtPh,)
*&oluene]
are deposited and the mother liquor is found to contain p-toluidine and EtPh,PO. When the preceeding experiment is conducted under an atmosphere of dry 02, an extremely hydrolytically sensitive intermediate species containing a terminal 0x0 ligand and a tolylimido group can be identified by IR spectra. We believe this species to be MoO(Ntol)Cl,(OPEtPh,), by analogy to the known complex MoO(NH)C1,(OPEtPhz)Z,16 which also contains a readily hydrolyzed imido ligand. Sodium amalgam reduction of Mo(Ntol)CIJ(Me,P), in toluene in the presence of PMe, proceeds cleanly to give a dark green, diamagnetic Mo(IV) species,
Fig. 1. An ORTEP drawing of Mo(Ntol)Cl,(Me,P),. Thermal ellipsoids are drawn at the 50% probability level.
304
C. Y. CHOU et al. Table 1. Selected bond distances (A) and an&s (“) in Mo(Ntol)Cl,(Me,P), Mo( l)-Cl(2) Mo( l)-C1(3) Mo(l)_P(4)
2.525(l) 2.497( 1) 2.471(l)
MO(~)-P(S) Mo( 1)-P(6) Mo( 1)-N(7)
2.509( 1) 2.509( 1) 1.739(2)
MO(~)-N(7)-C(17) N(7)-MO(~)-Cl(3) N(7)-MO(~)-Cl(2) N(7)-MO(~)-P(4) N(7)-Mo( 1)-P(5) N(7)-Mo( 1)-P(6) C1(2)-MO(~)-Cl(3) C1(2)-MO(~)-P(4)
175.39(17) 171.78(6) 97.62(6) 89.35(6) 96.46(6) 91.71(6) 89.65(2) 172.40(2)
C1(2)-MO(~)-P(5) C1(2)-MO(~)-P(6) P(4)-MO(~)-P(5) P(4)-Ma(l)-P(6) P(5)-Ma(l)-P(6) C1(3)-MO(~)-P(4) Cl(3)-Ma(l)_(5) C1(3)-Ma(l)-P(6)
82.1q3) 81.55(3) 94.15(3) 101.36(3) 162.54(3) 83.61(2) 88.29(2) 85.56(2)
EXPERIMENTAL Crystal data@ Mo(Ntol)Cl,(Me,P), C16H34NC12P3M~, M = 500.22, monoclinic, P2,/n, a = 11.214(2) A, b = 22.371(3) A, c = 9.525(2) A, /I = 94.62(l)“, U = 2381.8(5) A3, Z = 4, D, = 1.395, p = 9.63 cm- l.
Data collection Syntex P2, diffractometer, graphite-monochromated MO-K, radiation (2 = 0.71069 A), 0-28 technique, scan range 1.0” below K,, and 1.1” above Kez, scan speed 1.5-20.0” min-‘, 4.0 < 26 < 45.0”, 3616 reflections measured, 3134 unique [data with I, < 0.2a(Z,) reset to I, = 0.2a(Z,)], empirical absorption correction applied.
Structure solution and rejnement Heavy-atom, two block matrix least squares. Non-hydrogen atoms assigned anisotropic thermal parameters, hydrogen atoms isotropic. Anomalous dispersion corrections for MO, Cl and P. Final agreement factors: R = 0.032, and R, = 0.036. Other details as described in Ref. 11. are grateful to the donors of the Petroleum Research Fund, administered by the American
Acknowledgements-We
Chemical Society, and to the Bureau of General Research at Kansas State University for support of this research. D.D.D. thanks the Phillips Petroleum Corp. for a fellowship.
REFERENCES 1. D. W. Patrick, L. K. Truesdale, S. A. Biller and K. B.
Sharpless, J. Org. Chem. 1978,43,2628. 2. (a) J. T. Groves and T. Takahashi, J. Am. Chem. Sot. 1983, 105, 2073; (b) D. Mansuy, J.-P. Mahy, A. Dureault, G. Bedi and P. Battioni, J. Chem. Sot., Chem. Commun. 1984,116l. 3. J. Kress, M. Wesolek, J.-P. LeNy and J. A. Osborn, .Z.Chem. Sot., Chem. Commun. 1981,1039. 4. (a) R. N. Hines and R. A. Pro&, J. Pharmacol. Exp. Ther. 1980,214,80; (b) R. A. Prough, P. C. Freeman and R. N. Hines, .Z.Biol. Chem. 1981,256,4178. 5. J. Chatt, J. R. Dilworth and R. L. Richards, Chem. Rev. 1978,78, 589. 6. J. D. Burrington, C. T. Kartisek and R. K. Grasselli, J. Catal. 1983,81,489. 7. W. A. Nugent and B. L. Haymore, Coord. Chem. Rev. 1980,123. 8. D. D. Devore and E. A. Maatta, Znorg. Chem. 1985,24, 2846. 9. E. I. Stiefel, Prog. Znorg. Chem. 1977,22, 1. 10. (a) R. Barral, C. Bocard, I. Seree de Roth and L. Sajus, Tetrahedron Lett. 1972,1693 ; (b) W. E. Newton, J. L. Corbin, D. C. Bravard, J. E. Searles and J. W. McDonald, Znorg. Chem. 1974,13, 1100. 11. D. D. Devore, F. Takusagawa and E. A. Maatta, Znorg. Chim. Acta (in press). 12. C. Y. Chou, J. C. Huffman and E. A. Maatta, .Z.Chem. Sot., Chem. Commun. 1984,1184. 13. C. Y. Chou, J. C. Huffman and E. A. Maatta, Znorg. Chem. (in press). 14. D. Bright and J. A. Ibers, Znorg. Chem. 1969,8,703. 15. D. C. Bradley, M. B. Hursthouse, K. M. A. Malik, A. J. Neilson and R. L. Short, J. Chem. Sot., Dalton Trans. 1983,265l. 16. J. Chatt, R. Choukroun, J. R. Dilworth, J. Hyde, P. Vella and J. Zubieta, Transition Met. Chem. 1979, 4, 59.
1986 0
0277-5387j86 1986 Pqmon
S3.00+ Prcs
.OO Ltd
ORGANOIMIDO COMPLEXES OF MO(W), MO(v) AND MO(W): PREPARATION, STRUCTURE AND REACTIVITY C. Y. CHOU,
D. D. DEVORE,
S. C. HUCKETT
and E. A. MAATTA*
Department of Chemistry, Kansas State University, Manhattan, KS 66506, U.S.A. J. C. HUFFMAN Molecular Structure Center, Indiana University, Bloomington, IN 47405, U.S.A. and F. TAKUSAGAWA Department of Chemistry, University of Kansas, Lawrence, KS 66045, U.S.A. (Received 12 June 1985)
Abstract-Two series of p-tolylimido (Ntol) complexes of Mo(VI), MO(V) and Mo(IV) are described. One series, containing diethyldithiocarbamate ligands, is formed via oxygen atom abstraction from Mo(VI)O(Ntol)(SzCNEtz)z using tertiary phosphines which affords the oxo-bridged MO(V) dimer [Mo(Ntol)(SzCNEt2)2]z0 and the Mo(IV) species Mo(Ntol&CNEt,),. In solution, the Ma(V) dimer participates in a disproportionation equilibrium affording the Mo(V1) and Mo(IV) complexes. Mo(Ntol)(S&NEtz)z reacts with O2 to regenerate MoO(Ntol)(S,CNEt,),, thus completing a catalytic phosphine oxidation cycle. Mo(Ntol)(S,CNEt& also reacts with MezSO to yield the Mo(V1) complex and Me,S, and with dimethylacetylenedicarboxylate to yield the alkyne complex, Mo(Ntol)(DMAC)(S,CNEt,)2. The second series of p-tolylimido complexes contains chloride and phosphine co-ligands and derives from the Mo(V1) species Mo(Ntol)Cl,(THF). In the presence of tertiary phosphines, this complex undergoes reduction to afford monomeric MO(V) complexes of the form Mo(Ntol)Cl,L, (L = Ph,P, EtPh,P and Me,P; L, = Ph2PC2H4PPh2). The bis(monodentate phosphine) complexes possess the trans, mergeometry while the diphos complex is assigned the cis, mer-configuration. Reduction of Mo(Ntol)C1,(Me,P)z by Na-Hg in the presence of Me,P affords the Mo(IV)complex cis, merMo(Ntol)Cl,(Me,P), whose molecular structure is described.
In recent years, an increasing research effort has been focused on transition-metal complexes bearing organoimido ligands (NR), and it is now clear that such species are of importance and utility in a diverse array of processes ranging from synthetic procedures (e.g. the amination,’ aziridinatior? and metathesis3 of olefins) to biological functions (e.g. metabolism of certain hydrazines4). Molybdenum organoimido complexes are of additional interest in that they may
* Author to whom correspondence should be addressed.
serve as models of the {Mo(NH)} species that are likely intermediates in nitrogen fixation’ and in the ammoxidation of propylene.‘j Most of the organoimido molybdenum complexes prepared to date are Mo(V1) species.7 Herein we describe two series of ptolylimido complexes of Mo(VI), M(V) and Mo(IV). One series, containing diethyldithiocarbamate ligands, displays prominent oxygen atom transfer reactivity; the second series, containing chloride and phosphine ligands, is characterized by facile oxidation and reduction reactions.
301
C. Y. CHOU et al.
302
RESULTS
AND
DISCUSSION
Dithiocarbamate complexes
The reaction of the p-tolylimido Mo(VI) species MoO(Ntol)L, (L = S,CNEt,) with 0.5 equivalents of Ph,P or EtPh,P in CH,C& produces the corresponding phosphine oxide and a dinuclear MO(V) complex Mo,O(Ntol),L, [eqn (l)] :s MoO(Ntol)L,
+0.5R,P + Mo,O(Ntol),L,
+ 0.5R,PO.
(1)
Two core structures, A and B, are conceivable for the MO(V) dimer ; the oxo-bridged structure A is
Solutions of Mo(Ntol)L, react rapidly with O2 (1 atm) at ambient temperature to regenerate MoO(Ntol)L, [eqn (4)] : Mo(Ntol)L, +$02 + MoO(Ntol)L,.
(4)
Thus, taken collectively, eqns (l), (3) and (4) constitute a catalytic phosphine oxidation cycle. We have observed the oxidation of ca 50 equiv. of PPh, using this system without any diminution of catalytic activity. Mo(Ntol)L, solutions also react with dimethylsulfoxide to afford MoO(Ntol)L, and dimethyl sulfide [eqn (5)] : Mo(Ntol)L, + Me,SO + MoO(Ntol)L, indicated by IR data [absence of v(Mo=O)] and 1‘0 NMR studies [S( “0) = 1002 ppm]. The electronic spectrum of (Mo(Ntol)L,),O in toluene displays an intense absorption at 533 nm, a region characteristic of mono-oxo-bridged MO(V) dimers.g However, this band does not obey Beer’s law, a result which by analogy to the behavior of the corresponding Mo203L, system,” suggests the occurrence of the disproportionation equilibrium shown in eqn (2) :
Chloride and phosphine species
The reaction of p-tolylazide with MoCl,(THF), (THF = tetrahydrofuran) in 1,Zdichloroethane the p-tolylimido Mo(V1) species provides Mo(Ntol)Cl,(THF) in excellent yield [eqn (611:12 MoCl,(THF),
+ p-tolN, + Mo(Ntol)Cl,(THF)
e
K
MoO(Ntol)L, (2)
2 +
Mo(Ntol)L,
In support of this proposition, we find that toluene solutions of [Mo(Ntol)LJzO react with EtPhzP to produce EtPh,PO and the reactive 16-electron Mo(IV) species Mo(Ntol)L, [eqn (311: [Mo(Ntol)L,],O
f EtPhzP + 2Mo(Ntol)L, + EtPh,PO.
(3)
Although we have not isolated a pure sample of Mo(Ntol)L,, we have been able to probe its reactivity in solution. Thus, when the reaction of eqn (3) is conducted in the presence of an excess of the activated alkyne dimethylacetylenedicarboxylate (DMAC), the bright yellow alkyne complex Mo(Ntol)(DMAC)L, is formed. Solution ‘H NMR results and an X-ray diffraction study” confirm the expected pentagonal bipyramidal geometry for this species (C).
+ Me,S. (5)
+ N,.
(6)
The molecular structure of this 16-electron species features a short MO-N bond [1.717(3) A] and a near-linear MO-N-C bond angle [174.5(3)“], consonant with the presence ofa triply-bonded, fourelectron donor tolylimido ligand. The MO-O bond length of 2.234(3) A for the THF molecule suggests that the tolylimido ligand exerts a trans-influence of ca 0.2 A in this complex. The reaction of Mo(Ntol)Cl,(THF) with various tertiary phosphines (L) in 1,Zdichloroethene solutioninducesreductionofthemetalandaffordsptolylimido Ma(V) complexes of the form Mo(Ntol)Cl,L, [eqn (7)] :13 Mo(Ntol)Cl,(THF)
+ 2L + Mo(Ntol)Cl,L,,
(7)
where L = Ph,P, EtPh,P or Me,P; and LZ = Ph,PC2H4PPh2. These 17-electron~monomeric d’ complexes are air-stable in the solid state and display. magnetic moments near the spin-only value structure of 0f 1.73 clg. The molecular pseudodisplays a Mo(Ntol)Cl,(EtPh,P), octahedral &ordination about the MO atom, with a
Organoimido complexes of MO(W), MO(V) and MO(W) meridional arrangement of the chlorine atoms and a trans-disposition of the phosphine ligands. Thus, the overall geometry is similar to that previously found for the analogous Re and W complexes,
Mo(Ntol)Cl,(Me,P),
[eqn (9)] :
Mo(Ntol)Cl,(Me,P),
+ Me3P + Na-Hg -+ Mo(Ntol)Cl,(Me,P),.
303
(9)
A meridional arrangement of the Me3P ligands is indicated by NMR spectroscopy. In the ‘H spectrum, the methyl protons of the Me,P groups and appear as a triplet (6 1.42, JHp = 3.6 Hz, 18 H) and a doublet (6 1.28, J, = 7.8 Hz, 9 H), while the 31P{‘H) spectrum consists of a triplet at 6 5.38 Solutions of the Mo(Ntol)Cl,L, complexes give rise (J,, = 18.1 Hz; area 1) and a doublet at 6 -7.32 to sharp ESR spectra at room temperature. The [J,, = 18.1 Hz (area 2)]. spectra of the Ph,P, EtPh,P and Me,P complexes The molecular structure of Mo(Ntol)Cl,(Me,P), are very similar and reveal superhyperfine coupling has been determined. A drawing of the molecule is to two equivalent 31P nuclei, consistent with their shown in Fig. 1 and selected bond lengths and angles expected trans, mer-geometry. The ESR spectrum of are given in Table 1. The pseudo-octahedral the chelating diphos complex, however, shows structure features the expected meridional configurstrong coupling to only one 31P nucleus: since the ation of the Me3P ligands with the chlorine atoms unpaired electron is expected to reside in the occupying mutually cis-positions. Perhaps the most formally non-bonding MO &,-orbital, the cis, mersalient aspect of the structure is the absence of a geometry is indicated for this species. trans-influence exerted by the tolylimido ligand : the The phosphine ligands in Mo(Ntol)Cl,(EtPh,P), trans MO-Cl(3) bond distance of2.497(1) A is in fact can be substituted by the corresponding phosphine ca 0.03 A shorter than the cis MO-Cl(2) distance oxide [eqn (811: [2.525(l) A]. This small lengthening of MO-Cl(2) can be ascribed to the trans-influence of the Me,P Mo(Ntol)Cl,(EtPh,P), +2EtPh2P0 ligand which is also evidenced by the MO-P bond -, Mo(Ntol)Cl,(OPEtPh,),. (8) lengths: the pair of mutually trans phosphines display identical MO-P distances of 2.509(l) A ESR evidence suggests that the trans, mer-geometry while the MO-P(~) bond length is ca 0.04 A shorter is maintained for the bis(phosphine oxide) complex. at 2.471(l) A. When a toluene solution containing either Mo(Ntol)Cl,(EtPh,P), or Mo(Ntol)Cl,(OPEtPh,), is exposed to moist air, crystals of the Mo(V1) complex [MoO&l,(OPEtPh,)
*&oluene]
are deposited and the mother liquor is found to contain p-toluidine and EtPh,PO. When the preceeding experiment is conducted under an atmosphere of dry 02, an extremely hydrolytically sensitive intermediate species containing a terminal 0x0 ligand and a tolylimido group can be identified by IR spectra. We believe this species to be MoO(Ntol)Cl,(OPEtPh,), by analogy to the known complex MoO(NH)C1,(OPEtPhz)Z,16 which also contains a readily hydrolyzed imido ligand. Sodium amalgam reduction of Mo(Ntol)CIJ(Me,P), in toluene in the presence of PMe, proceeds cleanly to give a dark green, diamagnetic Mo(IV) species,
Fig. 1. An ORTEP drawing of Mo(Ntol)Cl,(Me,P),. Thermal ellipsoids are drawn at the 50% probability level.
304
C. Y. CHOU et al. Table 1. Selected bond distances (A) and an&s (“) in Mo(Ntol)Cl,(Me,P), Mo( l)-Cl(2) Mo( l)-C1(3) Mo(l)_P(4)
2.525(l) 2.497( 1) 2.471(l)
MO(~)-P(S) Mo( 1)-P(6) Mo( 1)-N(7)
2.509( 1) 2.509( 1) 1.739(2)
MO(~)-N(7)-C(17) N(7)-MO(~)-Cl(3) N(7)-MO(~)-Cl(2) N(7)-MO(~)-P(4) N(7)-Mo( 1)-P(5) N(7)-Mo( 1)-P(6) C1(2)-MO(~)-Cl(3) C1(2)-MO(~)-P(4)
175.39(17) 171.78(6) 97.62(6) 89.35(6) 96.46(6) 91.71(6) 89.65(2) 172.40(2)
C1(2)-MO(~)-P(5) C1(2)-MO(~)-P(6) P(4)-MO(~)-P(5) P(4)-Ma(l)-P(6) P(5)-Ma(l)-P(6) C1(3)-MO(~)-P(4) Cl(3)-Ma(l)_(5) C1(3)-Ma(l)-P(6)
82.1q3) 81.55(3) 94.15(3) 101.36(3) 162.54(3) 83.61(2) 88.29(2) 85.56(2)
EXPERIMENTAL Crystal data@ Mo(Ntol)Cl,(Me,P), C16H34NC12P3M~, M = 500.22, monoclinic, P2,/n, a = 11.214(2) A, b = 22.371(3) A, c = 9.525(2) A, /I = 94.62(l)“, U = 2381.8(5) A3, Z = 4, D, = 1.395, p = 9.63 cm- l.
Data collection Syntex P2, diffractometer, graphite-monochromated MO-K, radiation (2 = 0.71069 A), 0-28 technique, scan range 1.0” below K,, and 1.1” above Kez, scan speed 1.5-20.0” min-‘, 4.0 < 26 < 45.0”, 3616 reflections measured, 3134 unique [data with I, < 0.2a(Z,) reset to I, = 0.2a(Z,)], empirical absorption correction applied.
Structure solution and rejnement Heavy-atom, two block matrix least squares. Non-hydrogen atoms assigned anisotropic thermal parameters, hydrogen atoms isotropic. Anomalous dispersion corrections for MO, Cl and P. Final agreement factors: R = 0.032, and R, = 0.036. Other details as described in Ref. 11. are grateful to the donors of the Petroleum Research Fund, administered by the American
Acknowledgements-We
Chemical Society, and to the Bureau of General Research at Kansas State University for support of this research. D.D.D. thanks the Phillips Petroleum Corp. for a fellowship.
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