31P-31P spin-spin coupling in complexes containing two phosphorus ligands

Hydrogen Bonding in Platinum Indolylphosphine Polyfluorido and Fluorido Complexes

The reaction of the Pt complexes cis-[Pt(CH₃ )(Ar){Ph₂ P(Ind)}₂ ] (Ind=2-(3-methyl)indolyl, Ar=4-tBuC₆ H₄ (1 a)_, 4-CH₃ C₆ H₄ (1 b), Ph (1 c), 4-FC₆ H₄ (1 d), 4-ClC₆ H₄ (1 e), 4-CF₃ C₆ H₄ (1 f)) with HF afforded the polyfluorido complexes trans-[Pt(F(HF)₂ )(Ar){Ph₂ P(Ind)}₂ ] 2 a-f, which can be converted into the fluoride derivatives trans-[Pt(F)(Ar){Ph₂ P(Ind)}₂ ] (3 a-f) by treatment with CsF. The compounds 2 a-f and 3 a-f were characterised thoroughly by multinuclear NMR spectroscopy. The data reveal hydrogen bonding of the fluorido ligand with HF molecules and the indolylphosphine ligand. Polyfluorido complexes 2 a-f show larger |¹ J(F,Pt)|, but lower ¹ J(H,F) coupling constants when compared to the fluorido complexes 3 a-f. Decreasing ¹ J(P,Pt) coupling constants in 2 a-f and 3 a-f suggest a cis influence of the aryl ligands in the following order: 4-tBuC₆ H₄ (a) ≈4-CH₃ C₆ H₄ (b)<Ph (c)≪4-FC₆ H₄ (d)<4-ClC₆ H₄ (e)<4-CF₃ C₆ H₄ (f). In addition, the larger cis influence of aryl ligands bearing electron-withdrawing groups in the para position correlates with decreasing magnitudes of |¹ J(F,Pt)| coupling constants. The interpretation of the experimental data was supported by quantum-chemical DFT calculations.

Tungsten and Molybdenum Dinitrogen Complexes Supported by a Pentadentate Tetrapodal Phosphine Ligand: Comparative Spectroscopic, Electrochemical and Reactivity Studies

The tungsten dinitrogen complex [W(N2)(PMe2PPPh2)] (2) (PMe2PPPh2 = [2-({bis[3-(diphenylphosphino)propyl]-phosphino}methyl)-2-methylpropane-1,3-diyl]bis(dimethylphosphine)]) is synthesized and characterized by X-ray diffraction as well as IR and NMR spectroscopies, showing strong analogies to its molybdenum analogue...

Platinum Indolylphosphine Fluorido and Polyfluorido Complexes: An Interplay between Cyclometallation, Fluoride Migration, and Hydrogen Bonding

The reaction of [PtCl2 (COD)] (COD=1,5-cyclooctadiene) with diisopropyl-2-(3-methyl)indolylphosphine (iPr2 P(C9 H8 N)) led to the formation of the platinum(ii) chlorido complexes, cis-[PtCl2 {iPr2 P(C9 H8 N)}2 ] (1) and trans-[PtCl2 {iPr2 P(C9 H8 N)}2 ] (2). The cis-complex 1 reacted with NEt3 yielding the complex cis-[PtCl{κ2 -(P,N)-iPr2 P(C9 H7 N)}{iPr2 P(C9 H8 N)}] (3) bearing a cyclometalated κ2 -(P,N)-phosphine ligand, while the isomer 2 with a trans-configuration did not show any reactivity towards NEt3 . Treatment of 1 or 3 with (CH3 )4 NF (TMAF) resulted in the formation of the twofold cyclometalated complex cis-[Pt{κ2 -(P,N)-iPr2 P(C9 H7 N)}2 ] (4). The molecular structures of the complexes 1-4 were determined by single-crystal X-ray diffraction. The fluorido complex cis-[PtF{κ2 -(P,N)-iPr2 P(C9 H7 N)}{iPr2 P(C9 H8 N)}] ⋅ (HF)4 (5 ⋅ (HF)4 ) was formed when complex 4 was treated with different hydrogen fluoride sources. The Pt(ii) fluorido complex 5 ⋅ (HF)4 exhibits intramolecular hydrogen bonding in its outer coordination sphere between the fluorido ligand and the NH group of the 3-methylindolyl moiety. In contrast to its chlorido analogue 3, complex 5 ⋅ (HF)4 reacted with CO or the ynamide 1-(2-phenylethynyl)-2-pyrrolidinone to yield the complexes trans-[Pt(CO){κ2 -(P,C)-iPr2 P(C9 H7 NCO)}{iPr2 P(C9 H8 N)}][F(HF)4 ] (7) and a complex, which we suggest to be cis-[Pt{C=C(Ph)OCN(C3 H6 )}{κ2 -(P,N)-iPr2 P(C9 H7 N)}{iPr2 P(C9 H8 N)}][F(HF)4 ] (9), respectively. The structure of 9 was assigned on the basis of DFT calculations as well as NMR and IR data. Hydrogen bonding of HF and NH to fluoride was proven to be crucial for the existence of 7 and 9.

A Study of Through-Space and Through-Bond JPP Coupling in a Rigid Nonsymmetrical Bis(phosphine) and Its Metal Complexes

A series of representative late d-block metal complexes bearing a rigid bis(phosphine) ligand, iPr₂P-Ace-PPh₂ (L, Ace = acenaphthene-5,6-diyl), was prepared and fully characterized by various techniques, including multinuclear NMR and single-crystal X-ray diffraction. The heteroleptic nature of the peri-substituted ligand L allows for the direct observation of the J_PP couplings in the ³¹P{¹H} NMR spectra. Magnitudes of J_PP are correlated with the identity and geometry of the metal and the distortions of the ligand L. The forced overlap of the phosphine lone pairs due to the constraints imposed by the rigid acenaphthene skeleton in L results in a large ⁴ J_PP of 180 Hz. Sequestration of the lone pairs, either via oxidation of the phosphine or via metal chelation, results in distinct changes in the magnitude of J_PP. For tetrahedral d¹⁰ complexes ([LMCl₂], M = Zn, Cd, Hg), the J_PP is comparable to or larger than (193-309 Hz) that in free ligand L, although the P···P separation in these complexes is increased by ca. 0.4 Å (compare to free ligand L). The magnitude of J_PP diminishes to 26-117 Hz in square planar d⁸ complexes ([LMX₂], M = Ni, Pd, Pt; X = Cl, Br) and the octahedral Mo⁰ complex ([LMo(CO)₄], 33 Hz). Coupling deformation density calculations indicate the through-space interaction dominates in free L, while in metal complexes the main coupling pathway is via the metal atom.

Reactions of R(2)P-P(SiMe(3))Li with [(R'(3)P)(2)PtCl(2)]. A general and efficient entry to phosphanylphosphinidene complexes of platinum. Syntheses and structures of [(eta(2)-P=(i)Pr(2))Pt(p-Tol(3)P)(2)], [(eta(2)-P=(t)Bu(2))Pt(p-Tol(3)P)(2)], [{eta(2)-P=(N(i)Pr(2))(2)}Pt(p-Tol(3)P)(2)] and [{(Et(2)PhP)(2)Pt}(2)P(2)]

The reactions of lithium derivatives of diphosphanes R(2)P-P(SiMe(3))Li (R = (t)Bu, (i)Pr, Et(2)N and (i)Pr(2)N) with [(R'(3)P)(2)PtCl(2)] (R'(3)P = Et(3)P, Et(2)PhP, EtPh(2)P and p-Tol(3)P) proceed in a facile manner to afford side-on bonded phosphanylphosphinidene complexes of platinum [(eta(2)-P=R(2))Pt(PR'(3))(2)]. The related reactions of Ph(2)P-P(SiMe(3))Li with [(R'(3)P)(2)PtCl(2)] did not yield [(eta(2)-P=PPh(2))Pt(PR'(3))(2)] and resulted mainly in the formation of [{(R'(3)P)(2)Pt}(2)P(2)], Ph(2)P-PLi-PPh(2), (Me(3)Si)(2)PLi and (Me(3)Si)(3)P. Crystallographic data are reported for the compounds [(eta(2)-P=R(2))Pt(p-Tol(3)P)(2)] (R = (t)Bu, (i)Pr, ((i)Pr(2)N)(2)P) and for [{(Et(2)PhP)(2)Pt}(2)P(2)].

Spectroscopic characterization of molybdenum dinitrogen complexes containing a combination of di- and triphosphine coligands: 31P NMR analysis of five-spin systems

The three molybdenum-N2 complexes [Mo(N2)(dpepp)(depe)] (1), [Mo(N2)(dpepp)(dppe)] (2), and [Mo(N2)(dpepp)(1,2-dppp)] (3), all of which contain a combination of a bi- and a tridentate phosphine ligand, were prepared and investigated by vibrational and (31)P NMR spectroscopy. As a tridentate ligand bis(2-diphenylphosphinoethyl)phenylphosphine (dpepp) has been employed. The three different bidentate ligands are 1,2-bis(diethylphosphino)ethane (depe), 1,2-bis(diphenylphosphino)ethane (dppe), and R-(+)-1,2-bis(diphenylphosphino)propane (1,2-dppp). N-N as well as metal-N vibrations of 1-3 are identified and interpreted in terms of the geometric and electronic structures of the complexes. (31)P NMR spectra are recorded and fully analyzed. Moreover, correlation spectroscopy (COSY)-45 measurements are performed to determine the relative signs of coupling constants. Special attention is directed to a detection of different isomers and their (31)P NMR, as well as vibrational spectroscopic properties. The implications of the results for the area of synthetic nitrogen fixation with phosphine complexes are discussed.

Comparisons of phosphorus ligation properties in P(CH2NR)3P

Bicyclic P(CH2NMe)3P was synthesized, and its reactions with MnO2, elemental sulfur, p-toluenesulfonyl azide, BH3.THF, and W(CO)5(THF) were shown to furnish a variety of products in which the PC3 and/or the PN3 phosphorus are oxidized/coordinated. In contrast, reactions of the previously known P(CH2NPh)3P with Mo(0) and Ru(II) precursors were shown to afford products in which only the PC3 phosphorus is coordinated. The contrast in reactivity of P(CH2NR)3P (R = Me, Ph) with the aforementioned reagents is discussed in terms of steric and electronic factors. The new compounds are characterized by analytical and spectroscopic (IR, 1H, 31P, and 13C NMR) methods. The results of crystal and molecular structure X-ray analyses of the previously known compounds P(CH2O)3P and P(CH2NPh)3P and 6 of the 14 new compounds obtained in this investigation are presented. Salient features of these structures and the analysis of the Tolman cone angles calculated from their structural parameters are discussed in terms of the effects of constraint in the bicyclic moieties. Evidence is presented for greater M-P sigma bonding effects on coordination of the PC3 phosphorus of P(CH2NR)3P (R = Me, Ph) than are present in PMe3 analogues of group 6B metal carbonyls. From 1JBP data on the BH3 adducts of P(CH2NMe)3P, it is suggested that the free bases MeC(CH2NMe)3P < P(CH2NMe)3P < (Me2N)3P < P(MeNCH2CH2)3N increase in Lewis basicity at the PN3 phosphorus in the order shown. Substantial differences in 31P chemical shifts in the bicyclic compounds discussed herein relative to their acyclic analogues do not seem to be associated with the relatively small bond angle changes that occur around either the PN3 or the PC3 trivalent phosphorus atoms.

Tuning of the Structures of Chiral Phosphane-Phosphites: Application to the Highly Enantioselective Synthesis of α-Acyloxy Phosphonates by Catalytic Hydrogenation

A family of new chiral phosphane-phosphites 5 has been prepared and employed in the synthesis of rhodium complexes of formulation [Rh(cod)(5)]BF4 (7). The use of bulky phosphane or phosphite groups in the preparation of 7 avoids the formation of undesired disubstituted complexes, one of which (9 a) has been isolated and characterized. Ligands 5 display important differences from the bulkier phosphane-phosphites 1: complexes 7-unlike their rigid [Rh(cod)(1)]BF4 counterparts-show fluxional behaviour in solution, consistent with backbone oscillation around the coordination plane. A detailed screening of ligands 1 and 5 in catalytic asymmetric hydrogenations of enol phosphonates 12 demonstrated a critical influence of the steric characteristics of the phosphane-phosphite in the course of the reaction, and optimization of the two phosphorus functionalities resulted in the production of versatile and efficient catalysts for this class of hydrogenations: enantioselectivities of up to 98% ee were thus obtained with substrates bearing an alkyl substituent in the beta-position, while for their challenging aryl counterparts values of up to 92% ee were achieved. The coordination mode of phosphonate 12 a towards a Rh phosphane-phosphite fragment has also been investigated and a preference of the olefin fragment to occupy the position cis to the phosphite group has been observed. From this observation an interpretation of the configurations of the hydrogenated phosphonates has also been made.

Synthesis, Structure, and Reactivity of Palladacycles That Contain a Chiral Rhenium Fragment in the Backbone: New Cyclometalation and Catalyst Design Strategies

The bromocyclopentadienyl complex [(eta5-C5H4Br)Re(CO)3] is converted to racemic [(eta5-C5H4Br)Re(NO)(PPh3)(CH2PPh2)] (1 b) similarly to a published sequence for cyclopentadienyl analogues. Treatment of enantiopure (S)-[(eta5-C5H5)Re(NO)(PPh3)(CH3)] with nBuLi and I2 gives (S)-[(eta5-C5H4I)Re(NO)(PPh3)(CH3)] ((S)-6 c; 84 %), which is converted (Ph3C+ PF6 -, PPh2H, tBuOK) to (S)-[(eta5-C5H4I)Re(NO)(PPh3)(CH2PPh2)] ((S)-1 c). Reactions of 1 b and (S)-1 c with Pd[P(tBu)3]2 yield [{(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(mu-X)}2] (10; X = b, Br, rac/meso, 88 %; c, I, S,S, 22 %). Addition of PPh3 to 10 b gives [(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(PPh3)(Br)] (11 b; 92 %). Reaction of (S)-[(eta5-C5H5)Re(NO)(PPh3)(CH2PPh2)] ((S)-2) and Pd(OAc)(2) (1.5 equiv; toluene, RT) affords the novel Pd3(OAc)4-based palladacycle (S,S)-[(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(mu-OAc)2Pd(mu-OAc)2Pd(mu-PPh2CH2)(Ph3P)(ON)Re(eta5-C5H4)] ((S,S)-13; 71-90 %). Addition of LiCl and LiBr yields (S,S)-10 a,b (73 %), and Na(acac-F6) gives (S)-[(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(acac-F6)] ((S)-16, 72 %). Reaction of (S,S)-10 b and pyridine affords (S)-[(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)Pd(NC5H5)(Br)] ((S)-17 b, 72 %); other Lewis bases yield similar adducts. Reaction of (S)-2 and Pd(OAc)2 (0.5 equiv; benzene, 80 degrees C) gives the spiropalladacycle trans-(S,S)-[{(eta5-C5H4)Re(NO)(PPh3)(mu-CH2PPh2)}2Pd] (39 %). The crystal structures of (S)-6 c, 11 b, (S,S)- and (R,R)-132 C7H8, (S,S)-10 b, and (S)-17 b aid the preceding assignments. Both 10 b (racemic or S,S) and (S)-16 are excellent catalyst precursors for Suzuki and Heck couplings.

Spectroscopic Characterization of Primary and Secondary Phosphine Ligation on Ruthenium(II) Complexes

Ruthenium(II) complexes of the primary phosphines PH2Fc and PH2CH2Fc and the secondary phosphine PH(CH2Fc)2, including [(p-cymene)RuCl(L)2](PF6) (p-cymene = p-iPrC6H4Me, L = PH2CH2Fc and PH(CH2Fc)2, 2b and 2c, respectively) and trans-[RuCl2(L)4] (L = PH2Fc, PH2CH2Fc, and PH(CH2Fc)2, 3a-c, respectively) were prepared and characterized by IR, 1H NMR, and 31P NMR spectroscopy. 3b was additionally characterized by X-ray crystallography. The spectroscopic effects of phosphine ligation were determined. Characteristic downfield shifts of the 31P NMR resonances and increases in energy of the nu(P-H) modes were observed in all cases. Iterative fitting of coupling constants to second-order NMR spectra also resulted in a complete elucidation of 31P-1H and 31P-31P couplings. This analysis provides a basis for considering the influence of coordinate bonding on the observed 1J(PH) and 2J(PP) constants.