The binary transition-metal monophosphides CrP, MnP, FeP, and CoP have been studied with X-ray photoelectron spectroscopy. The shifts in phosphorus 2p(3/2) core line binding energies relative to that of elemental phosphorus indicated that the degree of ionicity of the metal-phosphorus bond decreases on progressing from CrP to CoP. The metal 2p(3/2) core line binding energies differ only slightly and show similar line shapes to those of the elemental metals, reaffirming the notion that these transition-metal phosphides have considerable metallic character. The satellite structure observed in the Co 2p(3/2) X-ray photoelectron spectra of Co metal and CoP was examined by reflection electron energy loss spectroscopy and has been attributed to plasmon loss, not final state effects as has been previously suggested. Valence-band spectra of the transition-metal phosphides agree well with the density of states profiles determined from band structure calculations. The electron populations of the different electronic states were extracted from the fitted valence-band spectra, and these confirm the presence of strong M-P and weak P-P bonding interactions. Atomic charges determined from the P 2p core line spectra and the fitted valence-band spectra support the approximate formulation M(1+)P(1-) for these phosphides.

The electronic structures of metal-rich binary phosphides M 2 P and M 3 P (M ) Cr-Ni) have been examined by means of X-ray photoelectron and absorption spectroscopy and compared with those of the monophosphides MP. The P 2p 3/2 binding and P K-edge absorption energies decrease with greater ionic character of the M-P bonding and indicate the presence of anionic phosphorus, contrary to previous theoretical assertions but consistent with our previous results. Interatomic effects play a more important role in affecting the energy shifts in these metal-rich phosphides than in the monophosphides, becoming more pronounced with higher metal concentration. Although the M 2p 3/2 XPS spectra show no discernible shifts in binding energies, they reveal satellite features whose intensity can be related to metal charge in the Co-and Ni-containing phosphides. In these cases, the metal charge becomes less positive with higher metal concentration. For Ni 2 P and Ni 3 P, this trend was confirmed from an analysis of the Ni L-edge and M-edge XANES spectra.

The silylated aryloxo ligands bis(o-silyloxyphenyl)phenylphosphine (abbreviated PhP{OT}(2)) and tris(o-trimethylsilyloxyphenyl)phosphine (abbreviated P{OT}(3), where T = Me(3)Si) were prepared. Complexation reactions with O=ReCl(2)(OEt)(PPh(3))(2) and O=ReCl(3)(PPh(3))(2) proceed by displacement of one PPh(3) and the subsequent stepwise replacement of the OEt and/or Cl substituents. The new complex Re(O)Cl(2)[kappa(2)-(P,O)-(PhP{O}{OT})](PPh(3)), formed by elimination of Me(3)SiOEt, exists in diastereomeric cis and trans forms. Elimination of a second equivalent of Me(3)SiCl gives Re(O)Cl[kappa(3)-(P,O,O)-(PhP{O}(2))](PPh(3)). Similarly P{OT}(3) converts Re(O)Cl(2)(OEt)(PPh(3))(2) to ReOCl(2)[kappa(2)-(P,O)-(P{O}{OT}(2))](PPh(3)) (5) (structurally characterized as 5.0.875CH(2)Cl(2)): crystal data; triclinic P&onemacr;, a = 14.302(4) Å, b = 18.734(2) Å, c = 17.639(4) Å, alpha = 80.950(12) degrees, beta = 80.12(2) degrees, gamma = 81.76(2) degrees, Z = 4. Final R(1) and wR(2) values are 0.0852 and 0.1525, respectively on F(o)(2) > 2sigma(F(o)(2)) data (or 0.1948 and 0.2019 on all data). The phenoxy phosphine ligand in 5 is bound via P and one O to Re. The P atoms are mutually cis to each other and to the terminal oxygen on Re. Two ortho-trimethylsiloxy substituted phenyl rings dangle from the coordinated phosphorus atom. Complex 5 can be converted to Re(O)Cl[kappa(3)-(P,O,O)-(P{O}(2){OT})](PPh(3)) (6) by treatment with PPN(+) Cl(-) and 6 was also obtained by direct reaction of Re(O)Cl(3)(PPh(3))(2) with P{OT}(3) at higher temperatures. The complex 6 has been structurally characterized: crystal data triclinic, P&onemacr;, a = 10.1509(6) Å, b = 12.1123(8) Å, c = 16.2142(14) Å, alpha = 97.851(7) degrees, beta = 94.852(7) degrees, gamma = 96.889(6) degrees, Z = 2. Final R(1) and wR(2) values were 0.0303 and 0.0721 on F(o)(2) > 2sigma(F(o)(2)) data (or 0.0348 and 0.0742 on all data). The phenoxyphosphine ligand in 6 is bound facially to Re through P and two of the phenoxy oxygens. The Ph(3)P group and terminal oxygen atoms are cis to the oxygen atoms of the phenoxy ligands and the Cl lies trans to P. One trimethylsiloxyphenol group dangles. Careful hydrolysis of 6 gave Re(O)Cl[kappa(3)-(P,O,O)-(P{O}(2){OH})](PPh(3)) which was also formed during complexation reactions in moist solvent. Solution (31)P{(1)H} NMR demonstrated cis- or trans-(P,P) geometry for the complexes, which was confirmed in the two aforementioned cases by structure determinations.

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