The complexes M
3[Pt(SnX
3)
5](M = Bu
4N
+,PhCH
2PPh
3+; X = Cl, Br),
cis-M
2[PtX
2(SnX
3)
2](M = Bu
4N
+,PhCH
2PPh
3+,CH
3PPh
3+,Pr
4N
+; X = Cl, Br),
and[PhCH
2PPh
3]
2[PtBr
3(SnBr
3)]have been prepared
andcharacterized by
119Sn
and 195Pt NMR,far-infrared,
and electronic absorption
and emission spectroscopies.Inacetone solutions the[Pt(SnX
3)
5]
3-ions retain their trigonal bipyramidal structures but arestereochemically nonrigidas evidenced by
119Sn
and 195Pt NMRspectroscopy. For[Pt(SnCl
3)
5]
3-spin correlation is preserved bet
ween183
and 363 K establishing that the nonrigidity is due tointramolecular tin site exchange, probably via Berrypseudorotation. Whereas,[Pt(SnCl
3)
5]
3-does not undergo loss of SnCl
3- orSnCl
2 to form either[Pt(SnCl
3)
4]
2-or[PtCl
2(SnCl
3)
2]
2-,[Pt(SnBr
3)
5]
3-is not stable in acetone solution in the absence of excessSnBr
2 and forms[PtBr
2(SnBr
3)
2]
2-and[PtBr
3(SnBr
3)]
2-by loss of SnBr
2. Similarly,[PtCl
2(SnCl
3)
2]
2-is stable in acetone atambient temperatures but disproportionates at elevated temperatures
and[PtBr
2(SnBr
3)
2]
2-loses SnBr
2 in acetoneto form[PtBr
3(SnBr
3)]
2-.The crystal structures of methyltriphenylphosphonium
cis-dibromobis(tribromostannyl)platinate(II)
and benzyltriphenylphosphoniumtribromo(tribromostannyl)platinate(II) have beendetermined. Bothcompounds crystallize in the triclinic space group
P![](/images/entities/onemacr.gif)
in unit cells
with
a = 12.293(16) Å,
b= 12.868(6) Å,
c =25.047(8) Å,
![](/images/gifchars/alpha.gif)
= 96.11(3)
![](/images/entities/deg.gif)
,
![](/images/gifchars/beta2.gif)
= 91.06(3)
![](/images/entities/deg.gif)
,
![](/images/gifchars/gamma.gif)
= 116.53(3)
![](/images/entities/deg.gif)
,
calc = 2.30 gcm
-3,
Z = 3
and with
a = 11.046(7)Å,
b = 14.164(9) Å,
c =22.549(10) Å,
![](/images/gifchars/alpha.gif)
= 89.44(4)
![](/images/entities/deg.gif)
,
![](/images/gifchars/beta2.gif)
= 83.32(5)
![](/images/entities/deg.gif)
,
![](/images/gifchars/gamma.gif)
= 68.31(5)
![](/images/entities/deg.gif)
,
calc = 1.893 gcm
-3,
Z= 2, respectively. Least-squares refinements converged at
R = 0.057
and 0.099 for 4048
and 4666independentobserved reflections
with
I/
![](/images/gifchars/sigma.gif)
(
I) > 3.0
and I/
![](/images/gifchars/sigma.gif)
(
I) > 2.0, respectively. Forthe former, the asymmetric unit contains1.5
cis-[PtBr
2(SnBr
3)
2]
2-ions, 0.5 of
which is disordered in such a
way as to bepseudocentrosymmetric. Thisdisordering involves a half-occupied PtBr
2 unit appearingon either side of the center. Simultaneously, onebrominefrom each SnBr
3 lig
and changes sides
while the other t
wobromines appear in average positions
with very smalldisplacements bet
ween their positions. The Pt-Sn distance in[PtBr
3(SnBr
3)]
2-(2.486(3) Å) is slightly shorterthan that in
cis-[PtBr
2(SnBr
3)
2]
2-(2.4955(3) Å, average),
and both are significantly longer thanthat previouslyfound in
cis-[PtCl
2(SnCl
3)
2]
2-(2.3556 Å, average),
which is not consistent
with the relativemagnitudes of the
1J(
195Pt-
119Sn)coupling constants (28 487, 25 720,
and 27 627 Hz, respectively).From our electronic absorption
and emission studies of the Pt-SnX
3-complexes,
we conclude that (a) the lo
w-energy transitions ared-dtransitions analogous to those found in[PtX
4]
2- systems, (b) theSnCl
3- lig
and is a stronger
![](/images/gifchars/sigma.gif)
donor thanSnBr
3-,(c) the triplet state from
which the emission occurs is split byspin-orbit coupling into different spin-orbitstates, (d) a forbidden spin-orbit state must lie at or near thebottom of the spin-orbit manifold, (e) the solidstate crystal environment perturbs the platinum-tin halide electronicstates,
and (f) dispersion of the samples insolvents changes this perturbation,
which can be rationalized in termsof an in-plane distortion of the squareplanar platinum coordination sphere.