- Email: [email protected]
Paramagnetic nitrile complexes of tris{3,5-dimethylpyrazolyl}borato nitrosyl molybdenum
PolyhedronVol. 15, No. 13. pp. 2247 2249, 1996
~)
Pergamon 0277-5387(95)00479-3
Copyright ~Li 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0277 5387/96 $15.00+0.00
PARAMAGNETIC NITRILE COMPLEXES OF TRIS{3,5DIMETHYLPYRAZOLYL) BORATO NITROSYL MOLYBDENUM SIMON E. M. FLYNN, JON A. McCLEVERTYt and MICHAEL D. WARD School of Chemistry, University of Bristol, Cantocks Close, Bristol BS8 1TS, U.K.
and ANDRZEJ WLODARCZYKt Department of Physical Chemistry, Krakow Technical University, Krakow, Poland
(Received 8 September 1995; accepted 27 September 1995) Abstract--The nitrile complexes [Mo(NO)Tp*I(NCR)] (R = Me, Pr n and CH2CH2CH2CN), obtained by reaction of [Mo(NO)Tp*I2] with the nitrile at room temperature, are paramagnetic (one unpaired electron), exhibiting characteristic EPR spectra and undergoing, electrochemically, an irreversible reduction process.
The coordinatively unsaturated (16e) complex [Mo(NO)Tp*I2] [Tp* = hydrotris(3,5-dimethylpyrazol-l-yl)borate] is redox-active) Much of its substitution chemistry appears to involve redox reactions arising from prior dissociation of I , which can then act as a reducing agent for the parent diiodide, giving the paramagnetic (17e) [Mo(NO)Tp*I2] . This uninegative anion is labile, apparently dissociating to give paramagnetic (17e) [Mo(NO)Tp*I(solvent)] in solution and this species may be important in subsequent substitution to give alkoxides, amido species, etc. Both such species have been detected by electrochemical and EPR spectral techniques.I In an unexpected reaction in acetonitrile, [Mo (NO)Tp*I2] reacted with Ag +, a potential oxidizing agent, to give the reduced (17e) product [Mo(NO) Tp*(NCMe)2] +, whose structure was established crystallographically.2 We have suggested 3 that this compound may arise by the following sequence : [Mo(NO)Tp* I2] + MeCN --* [Mo(NO)Tp*I(NCMe)] + + I-
~"Authors to whom correspondence should be addressed.
[Mo(NO)Tp*I2] + I- ~ [Mo(NO)Tp*I2]- + 1/2 I2 [Mo(NO)Tp*I2]
+ M e C N -~ [Mo(NO)Tp*I(NCMe)] + I
[Mo(NO)Tp*|(NCMe)] + + I[Mo(NO)Tp*I(NCMe)] + 1/2 I2 [Mo(NO)Tp*I(NCMe)] + MeCN [Mo(NO)Tp*(NCMe)2] + + I The reduction of [Mo(NO)Tp*I2] by I has been observed, 1 iodine was detected as a by-product of the reaction, 2 but we were unable to isolate or detect the mono-nitrile product [Mo(NO)Tp*I(NCMe)]. However, related pyrazole complexes [Mo(NO) TpI(pzH)] 4 and a chloro-pyridine analogue, [Mo(NO)Tp*Cl(py)],5 have been characterized. So there seems to be no reason, apriori, why the mononitrile species [Mo(NO)Tp*I(NCMe)] should not exist. Preliminary investigations of the behaviour of [Mo(NO)Tp*I2] in acetonitrile showed that unless the diiodide was scrupulously purified by chromatography prior to reaction, then a mixture of products was formed. The mixture showed several
2247
2248
S. E. M. FLYNN
NO stretching vibrations, was paramagnetic and probably contained, among several products, the known cation [Mo(NO)Tp*(NCMe)2] +, as the iodide. However, reaction with pure diiodide in neat acetonitrile at room temperature afforded pure [Mo(NO)Tp*I(NCMe)] in modest yield as a light green solid which has limited stability in chlorinated hydrocarbons and solvents containing traces of water. This compound exhibited VNo at 1624 c m - 1, some 30 cm-I lower than the related brown bisacetonitrile cation [Mo(NO)Tp*(NCMe)2] + (V~o 1657 cm-1). On repeating the synthesis of [Mo(NO) Tp*(NCMe)2] +, we observed that [Mo(NO) Tp*(NCMe)] is an intermediate, being formed rapidly when [Mo(NO)Yp*I2] is dissolved in acetonitrile, but that on addition of Ag +, it quickly disappeared as the cation was formed. The related butyronitrile complex [Mo(NO) Tp*I(NCPrn)] was formed in the same way as [Mo(NO)Tp*(NCMe)]. However, the glutaronitrile complex [Mo(NO)Tp*I{NC(CH2)3 CN}] was formed, together with [Mo(NO) Tp*I(OH)], by treatment of the diiodide with a large excess of the nitrile, which could only be removed from the reaction mixture by heating in v a c u o . However, the complex could be prepared more conveniently by reaction of 1 mol equiv, of the diiodide with 2 mol equiv, of the nitrile in thf. The green mono-substituted product was formed in c a 45% yield and after its removal from the solution and evaporation, a brown solid was formed in about 20% yield, which appeared to contain impure [Mo(NO)Tp*{NC(CH2)3CN}2] + (YNO : 1 6 5 2 cm-1, comparable to its acetonitrile analogue). We could obtain no evidence for the bimetallic species [{Mo(NO)Yp*l} 2NC(CH2) 3CN]. The new complexes showed IR absorptions consistent with their formulations, v i z . VBH at c a 2550 cm-~, and absorptions at c a 2150 and 1540 cmassociated with the nitrile groups and pyrazolyl rings of Tp*, respectively. The NO stretching frequencies occurred at 1627 + 3 cm - 1, typical of such neutral 17e complexes and close to that of [Mo(NO) Tp*Cl(py)] (1623 cm ~).5 The cations [Mo(NO) Tp*(NCR)2] + [R = Me, (CH2)3CN], which are also 17e species, showed VNoat c a 1655 cm t, being higher than the neutral species because of the positive charge. Interestingly, the NO stretching frequency of the nitrile cations was at least 25 cm-1 higher than the isoelectronic pyridine and pyrazole complexes ([Mo(NO)Tp*(py)2 ] + VNo = 1630 cm-~) in KBr discs, 3 suggesting that the nitriles are poorer a-donors and/or better ~-acceptors than the Nheterocycles. Although we have not measured magnetic susceptibilities in the solid state, in solution the new
e t al.
compounds exhibit EPR spectra consistent with the presence of one unpaired electron. The neutral species [Mo(NO)Tp*I(NCR)] exhibited giso in the range 2.011-2.012 (cf. [Mo(NO)Tp*Cl(py)], g = 1.9705) and isotropic AMo of c a 4.5 mT {95Mo (15.9%), 92Mo (9.6%), I = 5/2}. The hyperfine coupling constants are comparable with those in related neutral 17e species, [Mo(NO)Tp*XQ].4'5 Cyclic voltammetric studies of [Mo(NO) Tp*I(NCR)] revealed that all complexes underwent an irreversible reduction process, at c a - 1 . 7 V vs the ferrocene/ferricinium couple. The process may involve formation of [Mo(NO)Tp*I(NCR)]-, which then dissociates I-, which was detected voltammetrically (oxidation to I2 and formation of I3) and confirmed by wave enhancement on addition of [Bu]N]I. The bis(acetonitrile) cation [Mo(NO)Tp*(NCMe)2] + was reduced in a reversible one-electron process at - 1 . 4 1 V vs the ferrocene/ferricinium couple. This process corresponds to the formation of [Mo(NO)Tp*(NCMe)2], formally isoelectronic with [Mo(CO)2(NO)Tp*]. Thus, we have confirmed that the neutral species [Mo(NO)Tp*I(NCR)] does exist. Furthermore, the last step in the reaction sequence for converting [Mo(NO)Yp*I2] into [Mo(NO)Tp*(NCMe)2] + involves displacement of I - from [Mo(NO) Tp*(NCMe)] in acetonitrile and we have observed this process in solution. EXPERIMENTAL
All reagents were used as purchased without further purification, except [Mo(NO) {HB(Me2pz)3} I2] which was prepared as described in the literature. I Solvents were specially purified, dried and degassed. All yields are based on the starting metalcontaining compound. ~H N M R spectra were recorded on a Jeol GX270 instrument and FAB mass spectra were obtained using a VG-Prospec with 3-nitrobenzylalcohol as matrix. IR spectra were measured in KBr discs using a PE1600 F T I R spectrophotometer. EPR measurements were made using a Bruker ESP 300 E instrument in an X-band field, the data being calibrated with reference to external D P P H (9 = 2.0037). Elemental analyses were determined by the Microanalytical Laboratory of the School of Chemistry, University of Bristol. Electrochemical measurements were made using an EG & PAR model 273A potentiostat. A standard three-electrode configuration was used, with a Pt-bead working and auxiliary electrodes, and a saturated calomel electrode (SCE) as reference. Ferrocene was added at the end of each experiment as an internal standard; all potentials are quoted vs the
Tris {3,5-dimethylpyrazolyl }borato nitrosyl molybdenum ferrocene/ferrocenium couple (Fc/Fc+). Dichloromethane was used as solvent, being purified by distillation from Call2 and [NBu]][PF6] (10 x M) as base electrolyte. [Mo(NO)Tp*I (NCMe)] A solution of [Mo(NO)Tp*I2] (0.2 g, 0.296 mol) in acetonitrile (30 cm 3) was stirred at room temperature until it became green. The solvent was then evaporated almost to dryness in vacuo, diethyl ether (ca 10-15 cm 3) added and the mixture allowed to stand at ca - 2 0 ° C overnight. The green powder which had precipitated was filtered off, washed with ether and dried in vacuo (0.04 g, 21%). Found: C, 34.6; H, 4.4; N, 18.6; I, 22.0. Calc. for C17H25 BINsOMo: C, 34.5; H, 4.3; N, 19.0; I, 21.5%. MS (positive ion FAB): m/z = 593 ([M]+), 522 ([Mo(NO)Tp*I]+). IR (KBr disc): 2552 (VBH); 2153 (YEN); 1624 (VNo) cm 1. EPR (CH2C12 solution): 9,~o= 2.1021 ; A~so= 4.58 mT {9SMo (15.9%), 92Mo (9.6%), I = 5/2}. Electrochemistry (CH2C12 solution) : Er = - 1.74 V (irreversible). [Mo(NO)Tp*(NCMe)2I[PF6] A solution of [Mo(NO)Tp*I2] (0.2 g, 0.296 mol) in acetonitrile (30 cm 3) was stirred at room temperature. AgPF6 (0.6 g, 0.8 tool) was added and the AgI which precipitated was filtered off. The solvent was then almost evaporated in vacuo and diethyl ether added, as above. The brown powder which precipitated was filtered off and dried in vacuo (0.12 g, 60%). Found: C, 35.4; H, 4.4; N, 19.2; F, 17.4. Calc. for CwH2sBF6NgOPMo : C, 35.7; H, 4.4; N, 19.7; F, 17.8%. MS (positive FAB): m / z = 507 ([M] +, 425 ([Mo(NO)Tp*] +). IR (KBr disc) : 2553 (VBH); 2150 (YEN); 1657 (VNo) cm -1. Electrochemistry (CHzCI2 solution) : - 1.42 V ( E v a - E p c = 141 mV; for ferrocene/ferricinium couple, Ep~ - Ep~ = 120 mV). [Mo(NO)Tp*I(NCPr")] This compound was prepared in the same way as its acetonitrile analogue, affording a light green powder (0.12 g, 51%). F o u n d : C, 36.8; H, 4.8; N,
2249
17.8. Calc. for CwHz9BINsOMo: C, 36.9; H, 4.7; N, 18.1%. MS (positive ion FAB): m / z = 6 2 1 ([M]+), 552 = ([Mo(NO)Tp*I]+). IR (KBr disc): 2553 (VBH); 2148 (VcN); 1630 (VNo) cm -I. EPR (CH2C12 solution) : 9iso = 2.01196 ; A,so = 4.56 mT {95Mo (15.9%), 92Mo (9.6%), 1 = 5/2}. Electrochemistry (CH2C12 solution): Ef = - 1 . 7 4 V (irreversible). [Mo(NO)Tp*I {NC(CH2) 3CN}] A solution of [Mo(NO)Tp*I2] (0.2 g, 0.296 mol) and gtutaronitrile (0.055 g, 0.592 mol) in thf (50 cm 3) was stirred until the solution became brown. The solvent was then evaporated to near dryness in vacua and diethyl ether added. A green powder precipitated, which was filtered off, washed with ether and dried in vacua (0.90 g, 47%). Found: C, 37.6; H, 4.7; N, 19.2. Calc. for C20H28BINgOMo: C, 37.3; H, 4.4; N, 19.6%. MS (positive ion FAB) : r e ~ z = 6 4 4 ([M]+); 552 ([Mo(NO)Tp*I]+). IR (KBr disc): 2554 (VBH); 2150 (VCN); 1629 (VNo) cm -l. EPR (CH2C12 solution): 9iso=2.01190, Aj~o=4.56 mT {95Mo (15.9%), 92Mo (9.6%), 1 = 5/2}. Electrochemistry (CH2C12 solution): - 1.71 V (irreversible). Acknowledgements--We are grateful to the SERC for
support (AW), Krakow Technical University for leave of absence (AW) and Drs J. P. Maher and A. J. Amoroso for general assistance with physical measurements. REFERENCES
1. T. N. Briggs, C. J. Jones, J. A. McCleverty, B. D. Neaves, N. El Murr and H. M. Colquhoun, J. Chem. Soc., Dalton Trans. 1985, 1249. 2. G. Denti, M. Ghedini, J. A. McCleverty, H. Adams and N. A. Bailey, Trans. Met. Chem. 1982, 7, 222. 3. N. A1 Obaidi, A. J. Edwards, C. J. Jones, J. A. McCleverty, B. D. Neaves, F. E. Mabbs and D. Collison, J. Chem. Soc., Dalton Trans. 1989, 127. 4. A. Wlodarczyk, S. S. Kurek, J. P. Maher, A. S. Batsanov, J. A. K. Howard and J. A. McCleverty, Polyhedron 1993, 12, 715. 5. S. L. W. McWhinnie, C. J. Jones, J. A. McCleverty, D. Collison and F. E. Mabbs, J. Chem. Soc., Chem. Commun. 1990, 940. 6. S. J. Reynolds, C. F. Smith, C. J. Jones and J. A. McCleverty, Inorg. Synth. 1985, 23, 4.
~)
Pergamon 0277-5387(95)00479-3
Copyright ~Li 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0277 5387/96 $15.00+0.00
PARAMAGNETIC NITRILE COMPLEXES OF TRIS{3,5DIMETHYLPYRAZOLYL) BORATO NITROSYL MOLYBDENUM SIMON E. M. FLYNN, JON A. McCLEVERTYt and MICHAEL D. WARD School of Chemistry, University of Bristol, Cantocks Close, Bristol BS8 1TS, U.K.
and ANDRZEJ WLODARCZYKt Department of Physical Chemistry, Krakow Technical University, Krakow, Poland
(Received 8 September 1995; accepted 27 September 1995) Abstract--The nitrile complexes [Mo(NO)Tp*I(NCR)] (R = Me, Pr n and CH2CH2CH2CN), obtained by reaction of [Mo(NO)Tp*I2] with the nitrile at room temperature, are paramagnetic (one unpaired electron), exhibiting characteristic EPR spectra and undergoing, electrochemically, an irreversible reduction process.
The coordinatively unsaturated (16e) complex [Mo(NO)Tp*I2] [Tp* = hydrotris(3,5-dimethylpyrazol-l-yl)borate] is redox-active) Much of its substitution chemistry appears to involve redox reactions arising from prior dissociation of I , which can then act as a reducing agent for the parent diiodide, giving the paramagnetic (17e) [Mo(NO)Tp*I2] . This uninegative anion is labile, apparently dissociating to give paramagnetic (17e) [Mo(NO)Tp*I(solvent)] in solution and this species may be important in subsequent substitution to give alkoxides, amido species, etc. Both such species have been detected by electrochemical and EPR spectral techniques.I In an unexpected reaction in acetonitrile, [Mo (NO)Tp*I2] reacted with Ag +, a potential oxidizing agent, to give the reduced (17e) product [Mo(NO) Tp*(NCMe)2] +, whose structure was established crystallographically.2 We have suggested 3 that this compound may arise by the following sequence : [Mo(NO)Tp* I2] + MeCN --* [Mo(NO)Tp*I(NCMe)] + + I-
~"Authors to whom correspondence should be addressed.
[Mo(NO)Tp*I2] + I- ~ [Mo(NO)Tp*I2]- + 1/2 I2 [Mo(NO)Tp*I2]
+ M e C N -~ [Mo(NO)Tp*I(NCMe)] + I
[Mo(NO)Tp*|(NCMe)] + + I[Mo(NO)Tp*I(NCMe)] + 1/2 I2 [Mo(NO)Tp*I(NCMe)] + MeCN [Mo(NO)Tp*(NCMe)2] + + I The reduction of [Mo(NO)Tp*I2] by I has been observed, 1 iodine was detected as a by-product of the reaction, 2 but we were unable to isolate or detect the mono-nitrile product [Mo(NO)Tp*I(NCMe)]. However, related pyrazole complexes [Mo(NO) TpI(pzH)] 4 and a chloro-pyridine analogue, [Mo(NO)Tp*Cl(py)],5 have been characterized. So there seems to be no reason, apriori, why the mononitrile species [Mo(NO)Tp*I(NCMe)] should not exist. Preliminary investigations of the behaviour of [Mo(NO)Tp*I2] in acetonitrile showed that unless the diiodide was scrupulously purified by chromatography prior to reaction, then a mixture of products was formed. The mixture showed several
2247
2248
S. E. M. FLYNN
NO stretching vibrations, was paramagnetic and probably contained, among several products, the known cation [Mo(NO)Tp*(NCMe)2] +, as the iodide. However, reaction with pure diiodide in neat acetonitrile at room temperature afforded pure [Mo(NO)Tp*I(NCMe)] in modest yield as a light green solid which has limited stability in chlorinated hydrocarbons and solvents containing traces of water. This compound exhibited VNo at 1624 c m - 1, some 30 cm-I lower than the related brown bisacetonitrile cation [Mo(NO)Tp*(NCMe)2] + (V~o 1657 cm-1). On repeating the synthesis of [Mo(NO) Tp*(NCMe)2] +, we observed that [Mo(NO) Tp*(NCMe)] is an intermediate, being formed rapidly when [Mo(NO)Yp*I2] is dissolved in acetonitrile, but that on addition of Ag +, it quickly disappeared as the cation was formed. The related butyronitrile complex [Mo(NO) Tp*I(NCPrn)] was formed in the same way as [Mo(NO)Tp*(NCMe)]. However, the glutaronitrile complex [Mo(NO)Tp*I{NC(CH2)3 CN}] was formed, together with [Mo(NO) Tp*I(OH)], by treatment of the diiodide with a large excess of the nitrile, which could only be removed from the reaction mixture by heating in v a c u o . However, the complex could be prepared more conveniently by reaction of 1 mol equiv, of the diiodide with 2 mol equiv, of the nitrile in thf. The green mono-substituted product was formed in c a 45% yield and after its removal from the solution and evaporation, a brown solid was formed in about 20% yield, which appeared to contain impure [Mo(NO)Tp*{NC(CH2)3CN}2] + (YNO : 1 6 5 2 cm-1, comparable to its acetonitrile analogue). We could obtain no evidence for the bimetallic species [{Mo(NO)Yp*l} 2NC(CH2) 3CN]. The new complexes showed IR absorptions consistent with their formulations, v i z . VBH at c a 2550 cm-~, and absorptions at c a 2150 and 1540 cmassociated with the nitrile groups and pyrazolyl rings of Tp*, respectively. The NO stretching frequencies occurred at 1627 + 3 cm - 1, typical of such neutral 17e complexes and close to that of [Mo(NO) Tp*Cl(py)] (1623 cm ~).5 The cations [Mo(NO) Tp*(NCR)2] + [R = Me, (CH2)3CN], which are also 17e species, showed VNoat c a 1655 cm t, being higher than the neutral species because of the positive charge. Interestingly, the NO stretching frequency of the nitrile cations was at least 25 cm-1 higher than the isoelectronic pyridine and pyrazole complexes ([Mo(NO)Tp*(py)2 ] + VNo = 1630 cm-~) in KBr discs, 3 suggesting that the nitriles are poorer a-donors and/or better ~-acceptors than the Nheterocycles. Although we have not measured magnetic susceptibilities in the solid state, in solution the new
e t al.
compounds exhibit EPR spectra consistent with the presence of one unpaired electron. The neutral species [Mo(NO)Tp*I(NCR)] exhibited giso in the range 2.011-2.012 (cf. [Mo(NO)Tp*Cl(py)], g = 1.9705) and isotropic AMo of c a 4.5 mT {95Mo (15.9%), 92Mo (9.6%), I = 5/2}. The hyperfine coupling constants are comparable with those in related neutral 17e species, [Mo(NO)Tp*XQ].4'5 Cyclic voltammetric studies of [Mo(NO) Tp*I(NCR)] revealed that all complexes underwent an irreversible reduction process, at c a - 1 . 7 V vs the ferrocene/ferricinium couple. The process may involve formation of [Mo(NO)Tp*I(NCR)]-, which then dissociates I-, which was detected voltammetrically (oxidation to I2 and formation of I3) and confirmed by wave enhancement on addition of [Bu]N]I. The bis(acetonitrile) cation [Mo(NO)Tp*(NCMe)2] + was reduced in a reversible one-electron process at - 1 . 4 1 V vs the ferrocene/ferricinium couple. This process corresponds to the formation of [Mo(NO)Tp*(NCMe)2], formally isoelectronic with [Mo(CO)2(NO)Tp*]. Thus, we have confirmed that the neutral species [Mo(NO)Tp*I(NCR)] does exist. Furthermore, the last step in the reaction sequence for converting [Mo(NO)Yp*I2] into [Mo(NO)Tp*(NCMe)2] + involves displacement of I - from [Mo(NO) Tp*(NCMe)] in acetonitrile and we have observed this process in solution. EXPERIMENTAL
All reagents were used as purchased without further purification, except [Mo(NO) {HB(Me2pz)3} I2] which was prepared as described in the literature. I Solvents were specially purified, dried and degassed. All yields are based on the starting metalcontaining compound. ~H N M R spectra were recorded on a Jeol GX270 instrument and FAB mass spectra were obtained using a VG-Prospec with 3-nitrobenzylalcohol as matrix. IR spectra were measured in KBr discs using a PE1600 F T I R spectrophotometer. EPR measurements were made using a Bruker ESP 300 E instrument in an X-band field, the data being calibrated with reference to external D P P H (9 = 2.0037). Elemental analyses were determined by the Microanalytical Laboratory of the School of Chemistry, University of Bristol. Electrochemical measurements were made using an EG & PAR model 273A potentiostat. A standard three-electrode configuration was used, with a Pt-bead working and auxiliary electrodes, and a saturated calomel electrode (SCE) as reference. Ferrocene was added at the end of each experiment as an internal standard; all potentials are quoted vs the
Tris {3,5-dimethylpyrazolyl }borato nitrosyl molybdenum ferrocene/ferrocenium couple (Fc/Fc+). Dichloromethane was used as solvent, being purified by distillation from Call2 and [NBu]][PF6] (10 x M) as base electrolyte. [Mo(NO)Tp*I (NCMe)] A solution of [Mo(NO)Tp*I2] (0.2 g, 0.296 mol) in acetonitrile (30 cm 3) was stirred at room temperature until it became green. The solvent was then evaporated almost to dryness in vacuo, diethyl ether (ca 10-15 cm 3) added and the mixture allowed to stand at ca - 2 0 ° C overnight. The green powder which had precipitated was filtered off, washed with ether and dried in vacuo (0.04 g, 21%). Found: C, 34.6; H, 4.4; N, 18.6; I, 22.0. Calc. for C17H25 BINsOMo: C, 34.5; H, 4.3; N, 19.0; I, 21.5%. MS (positive ion FAB): m/z = 593 ([M]+), 522 ([Mo(NO)Tp*I]+). IR (KBr disc): 2552 (VBH); 2153 (YEN); 1624 (VNo) cm 1. EPR (CH2C12 solution): 9,~o= 2.1021 ; A~so= 4.58 mT {9SMo (15.9%), 92Mo (9.6%), I = 5/2}. Electrochemistry (CH2C12 solution) : Er = - 1.74 V (irreversible). [Mo(NO)Tp*(NCMe)2I[PF6] A solution of [Mo(NO)Tp*I2] (0.2 g, 0.296 mol) in acetonitrile (30 cm 3) was stirred at room temperature. AgPF6 (0.6 g, 0.8 tool) was added and the AgI which precipitated was filtered off. The solvent was then almost evaporated in vacuo and diethyl ether added, as above. The brown powder which precipitated was filtered off and dried in vacuo (0.12 g, 60%). Found: C, 35.4; H, 4.4; N, 19.2; F, 17.4. Calc. for CwH2sBF6NgOPMo : C, 35.7; H, 4.4; N, 19.7; F, 17.8%. MS (positive FAB): m / z = 507 ([M] +, 425 ([Mo(NO)Tp*] +). IR (KBr disc) : 2553 (VBH); 2150 (YEN); 1657 (VNo) cm -1. Electrochemistry (CHzCI2 solution) : - 1.42 V ( E v a - E p c = 141 mV; for ferrocene/ferricinium couple, Ep~ - Ep~ = 120 mV). [Mo(NO)Tp*I(NCPr")] This compound was prepared in the same way as its acetonitrile analogue, affording a light green powder (0.12 g, 51%). F o u n d : C, 36.8; H, 4.8; N,
2249
17.8. Calc. for CwHz9BINsOMo: C, 36.9; H, 4.7; N, 18.1%. MS (positive ion FAB): m / z = 6 2 1 ([M]+), 552 = ([Mo(NO)Tp*I]+). IR (KBr disc): 2553 (VBH); 2148 (VcN); 1630 (VNo) cm -I. EPR (CH2C12 solution) : 9iso = 2.01196 ; A,so = 4.56 mT {95Mo (15.9%), 92Mo (9.6%), 1 = 5/2}. Electrochemistry (CH2C12 solution): Ef = - 1 . 7 4 V (irreversible). [Mo(NO)Tp*I {NC(CH2) 3CN}] A solution of [Mo(NO)Tp*I2] (0.2 g, 0.296 mol) and gtutaronitrile (0.055 g, 0.592 mol) in thf (50 cm 3) was stirred until the solution became brown. The solvent was then evaporated to near dryness in vacua and diethyl ether added. A green powder precipitated, which was filtered off, washed with ether and dried in vacua (0.90 g, 47%). Found: C, 37.6; H, 4.7; N, 19.2. Calc. for C20H28BINgOMo: C, 37.3; H, 4.4; N, 19.6%. MS (positive ion FAB) : r e ~ z = 6 4 4 ([M]+); 552 ([Mo(NO)Tp*I]+). IR (KBr disc): 2554 (VBH); 2150 (VCN); 1629 (VNo) cm -l. EPR (CH2C12 solution): 9iso=2.01190, Aj~o=4.56 mT {95Mo (15.9%), 92Mo (9.6%), 1 = 5/2}. Electrochemistry (CH2C12 solution): - 1.71 V (irreversible). Acknowledgements--We are grateful to the SERC for
support (AW), Krakow Technical University for leave of absence (AW) and Drs J. P. Maher and A. J. Amoroso for general assistance with physical measurements. REFERENCES
1. T. N. Briggs, C. J. Jones, J. A. McCleverty, B. D. Neaves, N. El Murr and H. M. Colquhoun, J. Chem. Soc., Dalton Trans. 1985, 1249. 2. G. Denti, M. Ghedini, J. A. McCleverty, H. Adams and N. A. Bailey, Trans. Met. Chem. 1982, 7, 222. 3. N. A1 Obaidi, A. J. Edwards, C. J. Jones, J. A. McCleverty, B. D. Neaves, F. E. Mabbs and D. Collison, J. Chem. Soc., Dalton Trans. 1989, 127. 4. A. Wlodarczyk, S. S. Kurek, J. P. Maher, A. S. Batsanov, J. A. K. Howard and J. A. McCleverty, Polyhedron 1993, 12, 715. 5. S. L. W. McWhinnie, C. J. Jones, J. A. McCleverty, D. Collison and F. E. Mabbs, J. Chem. Soc., Chem. Commun. 1990, 940. 6. S. J. Reynolds, C. F. Smith, C. J. Jones and J. A. McCleverty, Inorg. Synth. 1985, 23, 4.