C(3A)
C(05)
C(53)
C(54)
(s, 3 H), 2.45 (s, 3 H), 1.66 (s, 3 H), 1.64 (s, 3 H), 1.17 (s, 3 H, MeC6H3).
13C NMR (C6D6, 30 °C): 1, d 98.3 (CH2Ph); 2, d 246.9 (xyNC), 43.5
(CH2Ph), 18.5 (xyMe).
C(08)
Si(3)
C(57)
C(04)
C(52)
‡ Crystal data: for 2 at 203 K: C59H51N4Ti, M = 863.99, monoclinic, space
group C2/c (no. 15), a = 37.22(1), b = 12.153(3), c = 21.069(9) Å,
b = 104.23(3)°, U = 9237(10) Å3, Dc = 1.242 g cm23, Z = 8. Of the 6154
unique reflections collected (5.36 @ 2q @ 45.34°) with Mo-Ka radiation
C(31)
C(3)
C(55)
C(65)
C(64)
C(23)
C(01)
C(02)
C(03)
C(51)
C(82)
C(4)
N(1)
2
(l = 0.71073 Å), the 6154 with Fo > 2s (Fo2) were used in the final least-
N(5)
N(6)
C(24)
squares refinement to yield R(Fo) = 0.045 and RW(Fo2) = 0.112.
For 3 at 296 K: C56H52N4Si2Ti2, M = 933.04, triclinic, space group P1
C(07)
C(8)
C(81)
–
Ti(1)
C(25)
(no. 2), a = 10.066(2), b = 10.481(2), c = 13.170(3) Å, a = 109.17(2),
b = 104.98(2), g = 93.62(2)°, U = 1251(1) Å3, Dc = 1.238 g cm23, Z = 1.
Of the 5056 unique reflections collected (5.32 @ 2q @ 52.64°) with Mo-Ka
radiation (l = 0.71073 Å), the 5056 with I > 3s(I) were used in the final
least-squares refinement to yield R = 0.036 and RW = 0.041.
C(63)
C(7)
C(83)
C(13)
Ti(2)
C(26)
C(27)
C(33)
C(14)
N(11)
C(34)
N(21)
C(67)
N(31)
C(213)
C(28)
C(15)
For 4 at 233 K: C71H68N6Si2Ti2, M = 1157.35, monoclinic, space group
C(312)
C(311)
P21/n (no. 14), a
= 12.788(2), b = 33.329(5), c = 14.616(3) Å,
b = 96.76(2)°, U = 6186(3) Å3, Dc = 1.242 g cm23, Z = 4. Of the 8122
unique reflections collected (5.26 @ 2q @ 113.70°) with Cu-Ka radiation
C(16)
C(19)
C(35)
C(110)
C(29)
(l = 1.54184 Å), the 8122 with Fo > 2s(Fo2) were used in the final least-
2
C(36)
C(39)
squares refinement to yield R(Fo) = 0.074 and RW(Fo2) = 0.184. Atomic
coordinates, bond lengths and angles, and thermal parameters have been
deposited at the Cambridge Crystallographic Data Centre (CCDC). See
Information for Authors, Issue No. 1. Any request to the CCDC for this
material should quote the full literature citation and the reference number
182/447.
C(210)
C(310)
Fig. 3 Molecular structure of 4 showing the atomic numbering scheme.
Selected interatomic distances (Å): Ti(1)···Ti(2) 2.804(2), Ti(1)–N(1)
2.064(7), Ti(1)–N(11) 2.006(7), Ti(1)–N(31) 2.321(7), Ti(1)–C(8)
1.970(8), Ti(1)–C(7) 2.097(9), Ti(2)–C(7) 2.16(1), Ti(2)–N(21) 2.013(8),
Ti(2)–N(31) 2.018(7), Ti(2)–N(6) 1.936(7), Ti(2)–N(5) 1.950(8), Ti(2)–
C(4) 2.250(9), Ti(2)–C(7) 2.163(10), C(7)–C(8) 1.34(1), C(7)–N(6)
1.34(1), C(4)–N(5) 1.31(1), C(3)–C(4) 1.44(1), C(2)–C(3) 1.38(1),
N(1)–C(2) 1.37(1).
References
1 R. R. Schrock, Acc. Chem. Res., 1997, 30, 9; P. W. Wanandi,
W. D. Davis and C. C. Cummins, J. Am. Chem. Soc., 1995, 117, 2110;
R. K. Minhas, L. Scoles, S. Wong and S. Gambarotta, Organometallics,
1996, 15, 1113; J. D. Scollard and D. H. McConville, Organometallics,
1995, 14, 5478; K. Aoyagi, P. K. Gantzel, K. Kalai and T. D. Tilley,
Organometallics, 1996, 15, 923; A. D. Horton, J. de With, A. J. van der
Linden and H. van de Weg, Organometallics, 1996, 15, 2672.
2 L. Scoles, R. Minhas, R. Duchateau, J. Jubb and S. Gambarotta,
Organometallics, 1994, 13, 4978.
3 R. P. Planalp, R. A. Andersen and A. Zalkin, Organometallics, 1983, 2,
16.
4 P. N. Riley, R. D. Profilet, P. E. Fanwick and I. P. Rothwell,
Organometallics, 1996, 15, 5502.
5 G. R. Davies, J. A. J. Jarvis and B. T. Kilbourn, Chem. Commun., 1971,
1511.
6 S. L. Latesky, A. K. McMullen, I. P. Rothwell and J. C. Huffman,
Organometallics, 1985, 4, 902.
7 I. P. Rothwell and L. D. Durfee, Chem. Rev., 1988, 88, 1059.
8 L. R. Chamberlain, L. D. Durfee, P. E. Fanwick, L. H. Kobriger,
S. L. Latesky, A. K. McMullen, I. P. Rothwell, K. Folting, J. C.
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390.
ligands have been formed by addition of xyNC to trimethyl-
silylmethylidyne bridges in 1,3-dimetallacyclobutadiene deriv-
atives of Nb or Ta.4 The unit may have originated via initial
a-hydrogen abstraction to produce an alkylidyne intermediate
or by hydrogen abstraction from an initially formed iminoacyl.
In both cases the hydrogen abstraction takes place by a
carbazole ligand. The other bridging unit corresponds to the
insertion of 2 equiv. of isocyanide into an alkylidene bridge
combined with a 1,2-hydrogen shift. The transfer of adjacent
hydrogen to iminoacyl carbon atoms has precedence.7
An interesting feature of the molecular structure of 4
concerns the distances within the iminoacyl component.
Specifically the Ti–N(5) and Ti–C(4) distances lead to a value
of 20.3 Å for the parameter [d(Ti–N)2d(Ti–C)].7 This value
combined with the long C(4)–N(5) distance are consistent with
the much debated amido-carbene resonance picture.10
We thank the National Science Foundation (Grant CHE-
9321906) for financial support of this research.
9 M. R. Collier, M. F. Lappert and R. Pearce, J. Chem. Soc., Dalton
Trans., 1973, 445.
10 K. Tatsumi, A. Nakamura, P. Hofmann, P. Stauffert and R. Hoffmann,
J. Am. Chem. Soc., 1985, 107, 4440.
Footnotes
† Selected spectroscopic data: 1H NMR (C6D6, 500 MHz, 30 °C): 1, d
6.58–7.91 (m, 18 H, aromatics), 3.24 (s, 4 H, TiCH2Ph); 2, d 6.39–8.02 (m,
32 H, aromatics), 3.69 (s, 4 H, CH2Ph), 1.46 (s, 12 H, Me2C6H3); 3, d 14.75
(s, 2 H, m-CHSiMe3), 20.50 (s, 18H, m-CHSiMe3); 4, d 2.55 (s, 3 H), 2.47
Received in Bloomington, IN, USA, 3rd March 1997; Com.
7/01493G
1110
Chem. Commun., 1997