_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Allyl (-enyl) complexes
ro tati an
Fig. 8.2 Interchange of syn and anti protons.
H1:: ~ :~H
(M)
[M]
Fig. 8.3 Rotation about M-allyl axis- syn and anti protons not interchanged.
A
146.6
c2
A
8
48.4
1 i
-~-~--,·--,-r--
80 60 40 ppm
Fig. 8.4 "C-{ 'H }-n.m.r. spectrum (2 5.2 MHz) of (1] '-C 2 H,)Pt (9"C, toluene-d 8 ). The
satellites are due to coupling with 1 "'Pt ( ~ ~.7% natural abundance): A
(trans)J(PtC,) = 225.2. J(PtC 2 ) = 61.1 Hz; B(cis)J(PtC,) = 226.0, J(PtC 2 )
= 54.5 Hz. (From Jolly, P.W. and Mynott. R. ( 1981) Adv. Organomet. Chem .. 19.
25 7.)
show cis-trans geometrica! isomerism in solution in hydrocarbon solvents. This is
revealed by 'Hand 13 C n.m.r. studies, when two sets ofresonances are observed.
At- 24°C in toluene-d 8 Ni(C 3 H 5 ) 2 consists of 70% trans and 30% cis isomer. Each
isomer gives rise to two signals (C', C 3 ) and c> in the 13 C spectrum ('H broad band
decoupled). In the case ofPt(C 3 H 5 ) 2 (Fig. 8.4) these are accompanied by satellite
257