The syntheses of Ni(PTA)
4 (
5), Pd(PTA)
4 (
6),
and Pt(PTA)
4 (
8) are accomplished through the reduction of theM
IICl
2 salts in water with excess 1,3,5-triaza-7-phosphaadamantane (PTA). The products are obtained as partiallyprotonated derivatives with protonation occurring at the nitrogen atoms of the bound PTA lig
ands. Crystal structuresillustrating the monoprotonated
and bis-protonated derivatives of
8, [Pt(PTA)
3(PTAH)][Cl] (
1S)
and [Pt(PTA)
2(PTAH)
2][BF
4]
2 (
2S), are reported. The crystal structure of an intermediate along the reduction pathway, [PdCl(PTA)
3][Cl] (
7), is also presented, showing a trans influence whereby the Pd-P bond length trans to the Cl
-lig
and is shorter, 2.238(3) Å, than the average Pd-P bond length cis to the Cl
- lig
and, 2.334(2) Å. Complex
8is also protonated at the metal center to form [(H)Pt(PTA)
4][X], where X = Cl
-, BF
4-, HCO
3-,
and C
3H
5CO
2-,through the addition of weak acids such as CO
2/H
2O, NH
4Cl, PTAH
+Cl
-, HPy
+BF
4-,
and crotonic acid. Additionof strong acids such as HCl or HBF
4 results in protonation at the PTA lig
ands. Thereby, the Pt metal center isshown to have a p
Ka between 7.44
and 9.25. The bound PTA lig
ands on complex
8 have a p
Ka below 4.69 butabove 2.12. Ni(CO)
4-n(PTA)
n derivatives are also reported for
n = 3 (
9), 2 (
10),
and 1 (
11). Using IR data of
11,PTA is determined to have an electronic parameter (
![](/images/gifchars/chi.gif)
) as defined by Tolman to be 15.3 cm
-1, indicating PTA tobe slightly less donating than PPh
3, where
![](/images/gifchars/chi.gif)
= 12.8 cm
-1. Complex
10 is crystallized out of a MeOH/ethersolution maintained at -15
![](/images/entities/deg.gif)
C
and characterized by X-ray crystallography. It is a distorted tetrahedron
and hasa crystallographically determined Tolman cone angle of PTA of 103
![](/images/entities/deg.gif)
. Monitored reactions of Ni(PTA)
4 with COin water via in situ IR techniques show that the rate observed for the dissociation of PTA to provide Ni(CO)(PTA)
3 is 7.92 × 10
-4 s
-1 at 20
![](/images/entities/deg.gif)
C. This rate, along with
31P NMR results, indicates that the M
0(PTA)
4 complexesexhibit little dissociation
and slow exchange of the bound PTA lig
ands.