Nuclear magnetic resonance studies of some novel metal carbonyl complexes and other derivatives of 2,6,7-trioxa-1,4-diphospha-bicyclo[2.2.2]octane

Abstract

The novel coordination properties of the nonchelating bifunctional phosphorus ligand P(OCH2)3P have allowed the characterization of (OC)6MP(OCH2)3P and (0C)5MP(0CH2)3PM(C0)5 (M = Cr, Mo, and W); axial (OC)4FeP(OCH2)3P, axial (0C)4FeP(CH20)3P, and diaxial (OC)4FeP(OCH2)3PFe(CO)4; [CH3P(OCH2)3P]BF4 and [P(OCH2)3PCH3]BF4; and [(OC)5WP(OCH2)aPCH3]BF4. The mode of coordination of the ligand in the monometallic and phosphonium compounds was determined from the characteristic changes in the P81 chemical shifts and the PH and PP coupling constants. These methods were also used to characterize the unusual nonaxial (OC)4FeP(OCH2)3P (see ref 18). The magnitudes and signs of the VPH, Vph, and 37PP coupling constants in all of the compounds were obtained from the proton nmr spectra using indor techniques where appropriate. The trends in these parameters as the electron-withdrawing power of the fourth group attached to phosphorus increases in the order, electron pair < metal carbonyl fragment < methyl group < chalcogen, are interpreted in terms of the expected changes in nuclear charge of the atoms and s character of the bonds in the ligand. Infrared studies indicate that quaternization of the ligand in [(OC5)WP(OCH2)3P] to form [(OC)sP(OCH2)3PCH3]BF4 does not detectably alter the overall nature of the tungsten-phosphorus bond.

Comparisons of Phosphorus Ligation Properties in P(CH2NR)3P

“…Transition Metal Complexes of 8a,b and 9a. The PC 3 phosphorus of 8a reacts with W(CO) 5 (THF) in THF to give 8h (48% yield) as the only product, in contrast to our earlier report of the reaction between W(CO) 5 (aniline) and 3a in 1:1 ratio that produced a mixture of 3n , q in variable yield …”

“…In 1965 our group and others reported various syntheses of 3a . Although phosphines are usually considered to be more Lewis basic than phosphites, the PO 3 phosphorusof 3a was shown to react preferentially with chalcogens and transition metals, and evidence consistent with better π-acceptor properties of the PO 3 phosphorus was presented. 6a,− A variety of nonmetal derivatives ( 3b − k ) and transition metal complexes ( 3l − x ) of 3a have appeared in the literature. 6a,− R groups other than H in 3a (i.e., 4 − 7 ), halo derivatives P(RCHO) 3 PX 2 of 4 − 6 , oxo derivatives P[C(R)HO] 3 PO and OP[C(CCl 3 )HO] 3 P of 4 − 6 , and P[C(CCl 3 )HO] 3 P=NTs have also been synthesized. −

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Synthesis of 2,6,7-trioxa-4-phosphabicyclo[2.2.2]octane systems

“…Moreover, it was highly desirable to determine the conditions necessary for a more reliable preparation of P(CH20)3P since this difunctional nonchelating ligand has been found to exhibit interesting coordination properties. 4 It is not obvious a priori why the transesterification of P(CH2OH)3 with P(OMe)3 should be more difficult than the analogous reaction with RC(CH2OH)3 or cfs-l,3,5-cyclohexanetriol. These latter triols with P(OMe)j afford P(OCH2)3CR and P(OCH)3(CH2)3, respectively, in high yields and numerous reports in the literature from other laboratories6 as well as ours6 on the use of these bicyclic phosphites in other reactions The resulting solution of P(CH2OH)3 was strongly basic when tested with moist pH paper and gave no further precipitate upon introduction of a few additional drops of NaOCH3 solution.…”

Phosphorus-31 NMR of some bicyclic phosphorus compounds

“…Compound (Table l) is a "cage" compound which is of special interest because of the simultaneous presence of a phosphine and a phosphite moiety in the same compound. Although phosphines are usually considered to be more basic ligands than phosphites, the phosphite end of reacts in preference to the phosphine end with transition metals and chalcogens ( 3,4). This unexpected behavior of the cage compound may be due to the strong molecular dipole moment of 3.10 D for this ligand, in which the phosphite end of the molecule comprises the negative end of the molecular dipole (4 ).…”

“…Although phosphines are usually considered to be more basic ligands than phosphites, the phosphite end of reacts in preference to the phosphine end with transition metals and chalcogens ( 3,4). This unexpected behavior of the cage compound may be due to the strong molecular dipole moment of 3.10 D for this ligand, in which the phosphite end of the molecule comprises the negative end of the molecular dipole (4 ). The rigid cage structure of _1_ prevents it from acting as a chelating ligand, but it can serve as a bridging group connecting two metal centers as in _2_.…”