Hy. Yang et al., DEMETALATION OF A DIMOLYBDENUM CYCLOTETRAPHOSPHOXANE CAGE COMPLEX ANDSYNTHESES OF HETEROBIMETALLIC CAGES, Organometallics, 13(12), 1994, pp. 4825-4834
Selective excision of the Mo-II vertex in the mixed-valent, adamantano
id cage complex Mo(CO)(4)[(Pr2NPO)-Pr-i]Mo-4(CO)(2)I-2 with sodium dit
hiocarbamate yielded the metalla ligand Mo(CO)(4)[(Pr2NPO)-Pr-i](4) (1
). Complex 1 has been characterized by spectroscopy and by X-ray cryst
allography. Its structure retains the parent adamantane framework exce
pt for the vacant metal vertex. Significant distortions of the P4O4 co
re are noted with [Mo]-P-O bonds (1.623 (4) Angstrom) shortened at the
expense of the uncoordinated P-O bonds (1.671 (4) Angstrom). Nucleoph
ilic attack by primary alcohols (ROH) on 1 led to cleavage of a single
P-O-P bond to give [((i)Pr(2)MPO)(2)((i)Pr(2)NPOR)((Pr2NP)-Pr-i(O)H)]
(R = Me, 3a; R = Et, 3b); the postulated monocyclic structure of 3a h
as been confirmed by X-ray crystallography. Synthetically the covergen
t lone pairs in 1 enabled formation of new heterobimetallic cage compl
exes of the type Mo(CO)(4)[(Pr2NPO)-Pr-i](4)M (4a-g; M = Cr(CO)(4), Fe
(CO)(3), NiBr2, PtCl2, Cu(MeCN)(2)BF4, AgNO3, PdBr2). The molecular st
ructure of Mo(CO)(4)[(Pr2NPO)-Pr-i]4NiBr2 (4c) has been determined. A
pseudotetrahedral coordination geometry was observed at the paramagnet
ic Ni-II center, and the P4O4 core was found to have readjusted to its
electronic demands. Comparison of the spectral properties of the cons
erved Mo(CO)(4) moiety in these products suggests a small but observab
le transmission of intracage influence from the heterometal. Treatment
of 4c with iron pentacarbonyl led to reduction of the nickel vertex a
nd formation of the diamagnetic complex Mo(CO)(4)[(Pr2NPO)-Pr-i]Ni-4(C
O)(2) (6). Competitive chlorination and iodination of 6 revealed prefe
rential halogenation at the nickel site.