ALTERNATIVE LIGANDS .32. NOVEL TETRAPHOSP HANE NICKEL-COMPLEXES WITH TRIPOD-LIGANDS OF THE TYPE XM'(OCH(2)PME(2))(N)(CH(2)CH(2)PR(2))(3-N) (M'=SI, GE N=0-3)

Tripod Ligands of the type XM'(OCH(2)PMe(2))(n)(CH(2)CH(2)PMe(2))(3-n) (M' = Si, Ge; n = 0-3) (1-6, Table 1) have been used together with PP h(3) or PMe(3) for the preparation of novel tetraphosphane complexes o f Nickel. The representatives LNiPPh(3) (7-12) are obtained by reactio n of Ni(COD)(2) (COD = 1,5-cyclooctadiene) with the corresponding liga nds and PPh(3) in toluene in moderate yields. The synthesis of the der ivatives LNiPMe(3) (13-18) is partly (16-18) accomplished in. analogy to the Ph(3)P-complexes; compounds 13-16 are obtained in higher yields by reaction of Ni(PMe(3))(4) with the respective ligand. As a rule, 1 3-18 cannot be separated from by-products. The trinuclear complex H(2) CH(2)PMe(2))(3)[Ni(PMe(2)CH(2)CH(2))(3)SiF](3) (19) is formed together with 18 in the reaction of Ni(COD)(2) with 6 and PMe(3). The new comp ounds have been characterized (if possible) by analytical (C, H), but in general by spectroscopic investigations (IR; H-1-, C-13-, F-19-, P- 31-NMR; MS). A weak, but significant Ni --> Si interaction through the cage is indicated by the following results: (i) Large low-field shift s Delta delta(f), of 35.2 ppm (12), 38.3 ppm (18) and 37.7 ppm (19); ( ii) (6)J(PF) coupling constants [or (3)J(PNiSiF) through the cage] of 6.0 Hz (12) and 7.6 Hz (18) together with a low-field shift Delta delt a(Si) of 12.8 ppm (12); (iii) NiSi distances of 3.95 Angstrom in 7 and 3.92 Angstrom in 12, accompanied by a compression of the cage along t he Ni ... Si axis. An additional release from the high charge density on Ni results from pi-backbonding to the phosphane Ligands.