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Interaction of PN with metal atoms in a krypton matrix
INORG. NUCL. CHEM. LETTERS Vol. 14, pp. I13-I15, 1978o @ P e r g a m o n Press Ltd. Printed in Great Britain.
0020-1650/78/0301-0113502o00/0
INTERACTION OF PN WITH METAL ATOMS IN A KRYPTONMATRIX i and Peter L. Timms
Robert M. Atkins
School of Chemistry, University of B r i s t o l , B r i s t o l
(Received
3
BS8 ITS,
U.K.
February ]978; received for publication ]6 February 1978)
In a previous p u b l i c a t i o n ( I ) , we reported the matrix i n f r a r e d spectrum of PN and i t s trimer P3N3.
The molecule PN might be expected to act as a ligand towards zero-valent
t r a n s i t i o n metals because i t is i s o - e l e c t r o n i c with CS which is now recognised as a powerful ligand (2,3), and because of i t s r e l a t i o n s h i p to phosphine and d i n i t r o g e n .
Here we report
some studies on reactions of PN with metal atoms in i n e r t matrices. Gaseous pI4N or pI5N was generated by heating the corresponding isotopic form of P3N5 to 900°C under vacuum; d i n i t r o g e n was also l i b e r a t e d .
The r e s u l t i n g mixture of PN and N2 was
condensed together with a metal vapour and excess of krypton, on a caesium iodide window at 1OK using established matrix techniques (4). on i n i t i a l
The infrared spectrum of the matrix was taken
deposition and a f t e r s l i g h t heating had allowed d i f f u s i o n w i t h i n the matrix.
Simpler spectra were obtained by condensing PN with Cu, Ag, or Au atoms than with Co, Ni, or Pd atoms because the l a t t e r metals formed complexes with N2 or with N2 + PN as well as with PN alone.
Condensation of PN with Cu atoms gave a new band d i s t i n c t from the bands due to PN
and P3N3, which we assign to a co-ordinated P-N stretch (see Table f o r frequencies).
Using a
mixture of p|4N and pI5N a three-band pattern emerged suggesting that two PN units are co-ordinated to copper in t h i s complex.
The absence of other new bands in the P-N stretching
region is consistent with a l i n e a r , centro-symmetric complex NzP ~ Cu + P~N
or
P~N ~ Cu ~ N~P
Ozin (5) has reported thatCu(CO)2, formed between Cu atoms and CO in a matrix, i~ also l i n e a r . Our results do not permit a clear d i s t i n c t i o n between Cu-NP and Cu-PN.
Molecular o r b i t a l
c a l c u l a t i o n s for PN by McLean and Yoshimine (6) suggest that bonding through phosphorus may be more probable. Gold atoms behaved l i k e copper atoms, giving a three-band pattern infrared spectrum on reaction with a mixture of pI4N and pI5N, which suggests that Au(PN)2 is formed.
With both
copper and gold, the bands ascribed to M(PN)2 showed some f i n e structure which changed i r r e v e r s i b l y with temperature, t y p i c a l of matrix s i t e e f f e c t s .
An analogous observation was
made on Au(CO)2 by Ozin (3). When s i l v e r atoms, PN and krypton were condensed together at 1OK, the matrix was an intense blue colour compared with the straw colour matrix seen using copper or gold atoms.
The
infrared spectrum of the matrix containing pI4N and Ag atoms, showed two new bands, a weak band at 1203 cm-I and a strong feature centred at 1048 cm- I . 1176 and 1026 cm-I r e s p e c t i v e l y .
additional band centred at 1036 cm- I . l-
With pI5N, the frequencies shifted to
Mixed pI4N and pI5N caused the appearance of only one The results suggest that at 1OK two species are present
The work includes part of the material in the Ph.D. thesis ( B r i s t o l University, 1976) of this author whose present address is Department of Engineering and Applied Science, Mason Laboratory, Yale U n i v e r s i t y , 9, Hillhouse Ave, flew Haven, Conn. 06520, U.2.A. 113
]]4
PN with Metal Atoms in a Krypton Matrix
TABLE Assigoment of P-N Stretching Bands Band Position
Assignment
Band Position
{cm -I )
Assignment
(cm -I )
1323
p14N a
1137
1293 1215 1196
pl5 N a Cu(pI4N)~ Cu(pI4N)~pI5N)
ll07 1240 1222
p 14N a p315N3 a -3 "J Au(pI~N)2 Au(pI4N)(pI5N)
1184
Cu(pI5N)2
1209
Au(pI5N)2
a values from ref. I. in the matrix. The species giving the higher frequency bands seems to contain only one PN molecule and i t may be Ag + P-N. The species giving the stronger and broader lower frequency bands seems to contain two PN molecules. I t is unlikely that the lower frequency bands are due to N~P ÷ Ag ÷ P-=Nbecause the P-N stretching frequency is so much below that for the comparable copper of gold compounds. Morelikely, the low frequency bands are due to a dimer of Ag + P-N with bridging PN groups, i.e. N LII
A/p\ g\ /Ag P
III
N
The observed shift of 150 om-l between the monomer and dimer is similar to that found between terminal and bridging carbonyl stretching frequencies. The matrices formed by condensing PN and krypton with Co, Ni or Pd atoms gave infrared spectra containing several new, weak, sharp bands in the 1200-1350 cm-l region. Thesebands can be assigned to co-ordinated PN. Bandsdue to the known metal-dinitrogen complexes were observed in the 2100 cm-l region together with some new bands which we assign to N-N stretches in mixed N2/PN complexes of the metals. The spectrum from nickel atoms and PN became simpler as the temperature was raised to 45K; only two bands of appreciable intensity remained, one at 2175 cm"I and the other at 1300 cm- l . The band at 2175 cm-l corresponds in frequency to that reported for Ni(N2)4 in a matrix (7). The band at 1300 cm-l may be due to Ni(PN)4, analogous to the iso-electronic Ni(CS)4 (3). However, the band assigned to Ni(PN)4 was weak and we did not succeed in attempts to prove the stoichiometry using a mixture of pI4N and p(15N) (8). Our metal-PN complexes appear to decompose on removal of the matrix gas but this does not rule out the possibility that PN complexes of metals could be stabilised by the presence of other ligands, as has been observed with complexes of CS (2). We thank Owens-I11inois Inc. and the Science Research Council for research support.
PN with Metal Atoms in a Krypton Matrix
References I. 2.
R.M. ATKINS and P.L. TIMMS, Spectrochimica Acta, 33A, 853 (1977). M.C. BAIRD and G. WILKINSON, Chem.Comm., 267 (1966).
3. 4. 5. 6. 7. 8.
G.A. OZIN and A. VANDERVOET, Prog.in Inorg.Chem., 19, I05 (1975). M. MOSCOVITSand G.A. OZIN, Cryochemistry, p.261, Wiley-lntersience, New York (1976). E.P. KUNDIG, M. MOSCOVITSand G.A. OZIN, J.Amer.Chem.Soc., 97, 2097 (1975). A.D. McLEANand M. YOSHIMINE, supplement to IBM J.Res.Dev., 12, 206 (1968). H. HUBER, E.P. KUNDIG, M. MOSCOVITSand G.A. OZIN, J.Amer.Chem.Soc., 95, 332 (1973). E.P. KUNDIGand P.L. TIMMS, unpublished results.
115
0020-1650/78/0301-0113502o00/0
INTERACTION OF PN WITH METAL ATOMS IN A KRYPTONMATRIX i and Peter L. Timms
Robert M. Atkins
School of Chemistry, University of B r i s t o l , B r i s t o l
(Received
3
BS8 ITS,
U.K.
February ]978; received for publication ]6 February 1978)
In a previous p u b l i c a t i o n ( I ) , we reported the matrix i n f r a r e d spectrum of PN and i t s trimer P3N3.
The molecule PN might be expected to act as a ligand towards zero-valent
t r a n s i t i o n metals because i t is i s o - e l e c t r o n i c with CS which is now recognised as a powerful ligand (2,3), and because of i t s r e l a t i o n s h i p to phosphine and d i n i t r o g e n .
Here we report
some studies on reactions of PN with metal atoms in i n e r t matrices. Gaseous pI4N or pI5N was generated by heating the corresponding isotopic form of P3N5 to 900°C under vacuum; d i n i t r o g e n was also l i b e r a t e d .
The r e s u l t i n g mixture of PN and N2 was
condensed together with a metal vapour and excess of krypton, on a caesium iodide window at 1OK using established matrix techniques (4). on i n i t i a l
The infrared spectrum of the matrix was taken
deposition and a f t e r s l i g h t heating had allowed d i f f u s i o n w i t h i n the matrix.
Simpler spectra were obtained by condensing PN with Cu, Ag, or Au atoms than with Co, Ni, or Pd atoms because the l a t t e r metals formed complexes with N2 or with N2 + PN as well as with PN alone.
Condensation of PN with Cu atoms gave a new band d i s t i n c t from the bands due to PN
and P3N3, which we assign to a co-ordinated P-N stretch (see Table f o r frequencies).
Using a
mixture of p|4N and pI5N a three-band pattern emerged suggesting that two PN units are co-ordinated to copper in t h i s complex.
The absence of other new bands in the P-N stretching
region is consistent with a l i n e a r , centro-symmetric complex NzP ~ Cu + P~N
or
P~N ~ Cu ~ N~P
Ozin (5) has reported thatCu(CO)2, formed between Cu atoms and CO in a matrix, i~ also l i n e a r . Our results do not permit a clear d i s t i n c t i o n between Cu-NP and Cu-PN.
Molecular o r b i t a l
c a l c u l a t i o n s for PN by McLean and Yoshimine (6) suggest that bonding through phosphorus may be more probable. Gold atoms behaved l i k e copper atoms, giving a three-band pattern infrared spectrum on reaction with a mixture of pI4N and pI5N, which suggests that Au(PN)2 is formed.
With both
copper and gold, the bands ascribed to M(PN)2 showed some f i n e structure which changed i r r e v e r s i b l y with temperature, t y p i c a l of matrix s i t e e f f e c t s .
An analogous observation was
made on Au(CO)2 by Ozin (3). When s i l v e r atoms, PN and krypton were condensed together at 1OK, the matrix was an intense blue colour compared with the straw colour matrix seen using copper or gold atoms.
The
infrared spectrum of the matrix containing pI4N and Ag atoms, showed two new bands, a weak band at 1203 cm-I and a strong feature centred at 1048 cm- I . 1176 and 1026 cm-I r e s p e c t i v e l y .
additional band centred at 1036 cm- I . l-
With pI5N, the frequencies shifted to
Mixed pI4N and pI5N caused the appearance of only one The results suggest that at 1OK two species are present
The work includes part of the material in the Ph.D. thesis ( B r i s t o l University, 1976) of this author whose present address is Department of Engineering and Applied Science, Mason Laboratory, Yale U n i v e r s i t y , 9, Hillhouse Ave, flew Haven, Conn. 06520, U.2.A. 113
]]4
PN with Metal Atoms in a Krypton Matrix
TABLE Assigoment of P-N Stretching Bands Band Position
Assignment
Band Position
{cm -I )
Assignment
(cm -I )
1323
p14N a
1137
1293 1215 1196
pl5 N a Cu(pI4N)~ Cu(pI4N)~pI5N)
ll07 1240 1222
p 14N a p315N3 a -3 "J Au(pI~N)2 Au(pI4N)(pI5N)
1184
Cu(pI5N)2
1209
Au(pI5N)2
a values from ref. I. in the matrix. The species giving the higher frequency bands seems to contain only one PN molecule and i t may be Ag + P-N. The species giving the stronger and broader lower frequency bands seems to contain two PN molecules. I t is unlikely that the lower frequency bands are due to N~P ÷ Ag ÷ P-=Nbecause the P-N stretching frequency is so much below that for the comparable copper of gold compounds. Morelikely, the low frequency bands are due to a dimer of Ag + P-N with bridging PN groups, i.e. N LII
A/p\ g\ /Ag P
III
N
The observed shift of 150 om-l between the monomer and dimer is similar to that found between terminal and bridging carbonyl stretching frequencies. The matrices formed by condensing PN and krypton with Co, Ni or Pd atoms gave infrared spectra containing several new, weak, sharp bands in the 1200-1350 cm-l region. Thesebands can be assigned to co-ordinated PN. Bandsdue to the known metal-dinitrogen complexes were observed in the 2100 cm-l region together with some new bands which we assign to N-N stretches in mixed N2/PN complexes of the metals. The spectrum from nickel atoms and PN became simpler as the temperature was raised to 45K; only two bands of appreciable intensity remained, one at 2175 cm"I and the other at 1300 cm- l . The band at 2175 cm-l corresponds in frequency to that reported for Ni(N2)4 in a matrix (7). The band at 1300 cm-l may be due to Ni(PN)4, analogous to the iso-electronic Ni(CS)4 (3). However, the band assigned to Ni(PN)4 was weak and we did not succeed in attempts to prove the stoichiometry using a mixture of pI4N and p(15N) (8). Our metal-PN complexes appear to decompose on removal of the matrix gas but this does not rule out the possibility that PN complexes of metals could be stabilised by the presence of other ligands, as has been observed with complexes of CS (2). We thank Owens-I11inois Inc. and the Science Research Council for research support.
PN with Metal Atoms in a Krypton Matrix
References I. 2.
R.M. ATKINS and P.L. TIMMS, Spectrochimica Acta, 33A, 853 (1977). M.C. BAIRD and G. WILKINSON, Chem.Comm., 267 (1966).
3. 4. 5. 6. 7. 8.
G.A. OZIN and A. VANDERVOET, Prog.in Inorg.Chem., 19, I05 (1975). M. MOSCOVITSand G.A. OZIN, Cryochemistry, p.261, Wiley-lntersience, New York (1976). E.P. KUNDIG, M. MOSCOVITSand G.A. OZIN, J.Amer.Chem.Soc., 97, 2097 (1975). A.D. McLEANand M. YOSHIMINE, supplement to IBM J.Res.Dev., 12, 206 (1968). H. HUBER, E.P. KUNDIG, M. MOSCOVITSand G.A. OZIN, J.Amer.Chem.Soc., 95, 332 (1973). E.P. KUNDIGand P.L. TIMMS, unpublished results.
115