Complexes of the Group V metals with diphenylacetylene. Crystal structure of dicarbonylbiscyclopentadienylbis-�-diphenylacetylenediniobium

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  Complexes of the Group V metals with diphenylacetylene. Crystal structure of dicarbonylbiscyclopentadienylbis-�-diphenylacetylenediniobium
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  CHEMICAL zyxwvusr OMMUNICATIONS, 968 1365 n-Complexes of the Group V Metals with Diphenylacetylene. Crystal Structure of zy icarbonylbiscyclopentadienylbis diphenylacetylenediniobium By A. N. NESMEYANOV, . I. GUSEV,* A. A. PASYNSKII, . N. ANISIMOV, . E. KOLOBOVA, nd Yu. T. STRUCHKOV zyxw Institute of Organo-element Compounds, Academy of Science of the U.S.S.R., Vavilova, 28, Moscow, U.S.S.R.) WE have reported1 that when C5H5Nb(CO), is irradiated with ultraviolet light in the presence of diphenylacetylene (tolan), C5H5Nb(CO),Ph,C, is formed. Further photochemical reactions of C,H,M(C0)4 (M=V,Nb, zyxwvu r Ta) with tolan gave C5H V(CO) Ph,C,, C5H5V(CO) Ph,C,) zyxwv   C,H,Nb(CO) (Ph,C,),, and C5H5Ta(CO)(Ph,C,),.3 From these complexes, C,H,V(CO),( n-Ph4C4), [C ,H ,Nb (CO) Ph,C,] [C 5H Ta (CO) Ph,C,] and C,H,Nb(CO) (Ph,C,) 3,3 were synthesised in the absence of u.v.-irradiation. For certain of these complexes, a preliminary X-ray study has been p~blished.~ Kow we report the results of an X-ray study of [C,H,Nb(CO)Ph,C,], I) m.p. 248-250 decomp.), which is formed, as air-stable, dark violet prisms, by heating zyxwvutsr SO ) a concentrated solution of C,H,Nb(CO),Ph,C, in toluene. According to cryoscopic data, the complex I) is dimeric, M 670, calc. 728, whilst lH n.m.r. and i.r. spectra (CDCI,), show that each Nb atom is bonded to the cyclopentadienyl ring, one terminal carbonyl group, and two bridging tolan molecules (a sharp singlet of C5H5-ring protons at zyxwv   4-17 p.p.m.; one band at zyxwvuts   (CEO) 1970 cm.-l; there is no band of a non-bridging co-ordinated triple bond in the region5 1600-1900 cm.-l). According to the mass spectrum there is a Nb-Nb bond (a peak of [C,H,Nb]f, with m/e 316, but no peak for [C,H,Nb]+). The diamagnetism of (I) suggests a double character for the Nb-Nb bond. On this basis the following molecular structure was pro- posed, which is confirmed by the present X-ray analysis. Compound (I) s the first organometallic complex studied with a Nb-Nb bond and the first n-complex with two bridging acetylenic ligands between two metal atoms. Crystal data: I) s triclinic, a 10.43, b 9-60, Dm 1.54, D 1-58 g.~m.-~ or 1, M 728, space group Pi. Intensities of ca. 1400 independent reflections were estimated visually disregarding absorption correction (an equi- inclination Weissenberg goniometer, unfiltered copper radiation). The structure was solved by the heavy-atom technique and refined by the full- matrix least-squares method with isotropic tem- perature factors. At the present stage of refine- ment, R 0.13, with standard deviations in bond lengths of 0.005-0.03 zy   and in bond angles of 0-3-2-0 depending on the atomic numbers. The dimeric molecule (Figure) is situated in the inversion centre. The tolan ligand geometry is c 9.12 A, 110.3 , zy   71.1 , 114.1 ,    P  u   b   l   i  s   h  e   d  o  n   0   1   J  a  n  u  a  r  y   1   9   6   8 .   D  o  w  n   l  o  a   d  e   d   b  y   T  e  m  p   l  e   U  n   i  v  e  r  s   i   t  y  o  n   2   4   /   1   0   /   2   0   1   4   0   0  :   2   5  :   5   2 . View Article Online / Journal Homepage / Table of Contents for this issue  1366 CHEMICAL zyx OMMUNICATIONS, 968 defined by the torsion angle C(3)C( )C(2)/C( )C 2)- C(4) which is equal to 28 and by the angle of 49 between phenyl ring planes. The co-ordinated triple bond length (1.39 zyxwvu   .02 A) is greater than that for two known complexes, each with one bridging tolan group, Ni,(C,H,),Ph2C2 11) and Co,(CO),Ph,C, (HI),' where this bond length is 1.35 zyxwvut   0.03 and 1.369 A.8 But the bond angles at acetylenic carbon atoms in 11) are 138 and 142 and in 111) 137 and 139 , zyxwvut .e. distinctly larger than the C(3)C(l)C(2) and C(4)C(2)C(l) angles in (I). This difference cannot be accounted for by steric hindrances but is probably caused by the lesser s-character of the co-ordinated triple bond in I) than in 11) and 111). It is o interest that, because of a steric repulsion between the carbonyl group carbon atom and the C(2) atom (see the Figure), the acetylenic group is not symmetrical with respect to the Nb-Nb bond, z  g the angle between the C(l)-C(2) and Nb-Nb vectors is equal to 80 instead of 90 . The average distance between the Nb-atom and the carbon atoms of the planar cyclopentadienyl ring is 2.45 A, ut the deviations of the individual values from this average are quite significant. Probably this inclination of the C,H,-ring is be caused by the very short intermolecular con- tacts C zyx   C (3.27 and 3-29 A in which just those C,H,-ring atoms having the minimum distances (2.40 and 2-43 A rom the Nb-atom participate. The Nb-Nb bond distance (2.74 A is much shorter than the analogous distance (3.31 A n N-N~I,~ nd somewhat less than the interatomic distance in Nb metal (2-86 A . If one takes the half of the Nb-Nb distance (1.66 A in cc-NbI, as an Nb single bond covalent radius then the distance Nb-C(cyclopentadieny1) may be estimated as 1-66 + 0.77 2-43 A 0.77 A s the sp3-hybridized carbon atom radius) which is reasonably close to the average experimental value in (I). Insofar as the Nb-Nb bond in (I) is much shorter than the doubled Nb radius and the complex is diamagnetic, this metal-to-metal bond probably has double- bond characteristics, which is consistent with the 18-electron rule. Just as in C5H5Nb(CO),,l0 he Nb atom in (I) is 7-co-ordinated; however, its co-ordination poly- hedron is severely distorted because of the metal- to-metal bond formation. Now we are completing the X-ray studies of C,H,V(CO),(.rr-Ph,C,) and have found that the first compound is monomeric, with two tolan molecules co-ordinated independently. C,H,Nb(CO) (PhZC,),, C,H,Nb(CO)(Ph2C2)3, and FIGURE zyxwvuts Received, August 2nd, 1968; Corn. 1060.) 1 A. N. Nesmejanov, K. N. Anisimov, N. E. Kolobova, and A. A. Pasynskii, Izvest. Akad. Nauk S.S.S.R., Otdel. z   A. N. Nesmejanov, K. N. Anisimov, N. E. Kolobova, and A. A. Pasynskii, Doklady Akad. Nauk S.S.S.R., 1968 A. N. Nesmeyanov, K. N. Anisimov, N. E. Kolobova, and A. A. Pasynskii, Izvest. Akad. Nauk S.S.S.R., Otdel. khim. Nauk, 1966 774. to be published. khim. Nauk, 1968 to be published. 4G G. Alexandrov, A. I. Gusev, andYu. T. Struchkov. Zhur. strukt. Khim., 1968 9 333. F. L. Bowden and A. B. P. Lever, Organometallic Chem. Rev., 1968 3 227. 0 S. Mills and B. H. Show, J. Organometallic Chem., 1968 2, 595. W. G. Sly, J. Amer. Chem. Soc. 1959 81 18. D. A. Brown, J. Chem. Phys., 1960 33 1037. L. F. Dahl and D. L. Wampler, Acta Cryst. 1962 15, 903. 1 R. J. Doedens and L. F. Dahl, J. Amer. Chem. zyxwvu OC. 965 87, 2576.    P  u   b   l   i  s   h  e   d  o  n   0   1   J  a  n  u  a  r  y   1   9   6   8 .   D  o  w  n   l  o  a   d  e   d   b  y   T  e  m  p   l  e   U  n   i  v  e  r  s   i   t  y  o  n   2   4   /   1   0   /   2   0   1   4   0   0  :   2   5  :   5   2 . View Article Online
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