Anionic Phosphine Research Articles

Substitution of chloride in [PtCl 2(PET 3) 2] by the chiral anionic ligand [Mo(CO) 5(PPhH)] − to give mixed platinum-molybdenum compounds and a 31P∗ 1H∗ NMR analysis of their fluxionality. X-ray crystal structure of [PtCl(PEt 3) 2 (μ-PPhH) ∗Mo(CO) 5∗] and trans-[Pt(PEt 3) 2 (μ-PPH) 2 ∗Mo(CO) 5∗ 2

Deprotonation of the primary phosphine complex [Mo(CO) 5(PPhH 2)] generated [Mo(CO) 5(PPhH)] −, a chiral anionic ligand which reacted readily with cis- or trans-[PtCl 2(PEt 3) 2] via facile nucleophilic substitution of one or both chloride ligands to afford trans-[PtCl(PEt 3) 2(μ-PPhH)∗Mo(CO) 5∗] ( 1) and cis- and trans-[Pt(PEt 3) 2(μ-PPhH) 2∗Mo(CO) 5∗ 2] ( 2), respectively. These are rare examples of heterometallic complexes containing primary phosphido bridges. Compound ( 1) can be described either as the square-planar Pt 11 complex with the anionic ligand PPhH∗Mo(CO) 5∗ − or as the PtMo phosphido-bridged dimer trans-[PtCl(PEt 3) 2(μ-PPhH)∗Mo(CO) 5∗]. As a phosphido-bridged heterobimetallic ( 1) possesses an exceptionally large PtPMo angle [120.9(1) °] reflecting the long PtMo nonbonding interaction (4.5 Å). Compound 2 can correspondingly be described either as a phosphido-bridged PtMo 2 trimer or a square-planar arrangement of two neutral PEt 3 and two anionic PPhH∗Mo(CO) 5∗ ligands at Pt. The low-temperature 31P∗ 1H∗ NMR spectrum of 1 showed several ABXY spin systems together with their associated ABXYM ( M = 195 Pt ) counterparts and variable-temperature studies revealed the dynamic interconversion of several rotametric isomers arising from restricted rotation about the PtPμ bond. The 31P∗ 1H∗ NMR spectrum of trans- 2 shows its two possible RR/SS and meso diastereoisomers, the latter existing in clearly identifiable rotameric forms which interconvert slowly at −75°C. We note very different values between 2J( P P) and 1J( 195 Pt P) for the anionic ligands [PPhH∗Mo(CO) 5∗] − and PEt 3, unattributable to bond length variation but which must reflect reduced s-orbital contribution to the PtP bond of the anionic phosphines PPhH∗Mo(CO) 5∗.

Substitution of chloride in [PtCl 2(dppe)] by the chiral anionic ligand [Mo(CO) 5(PPhH)] − : Synthesis and X-ray structure of [Pt(μ-PPhH) 2{Mo(CO) 5} 2(dppe)] and a 31P{ 1H} NMR analysis of its isomeric products and fluxionality

Reaction of the chiral anionic ligand [Mo(CO) 5(PPhH)] − with [PtCl 2(L-L)] affords the neutral trimetallic monophosphido bridged complexes [Pt(μ-PPhH) 2{Mo-(CO) 5} 2(L-L)] (L-L = dppe, Ph 2PCH 2CH 2PPh 2, 2; dpae, Ph 2AsCH 2CH 2AsPh 2, 3; dppe′, cis-Ph 2PCH=CHPPh 2, 4). Compounds 2–4 are the first examples of heterometallic complexes that contain two chiral primary phosphido bridges existing as pairs of diastereoisomers. [Pt(μ-PPhH) 2{Mo(CO) 5} 2(dppe)] ( 2) has been characterized spectroscopically and by a single-crystal X-ray analysis. The molecular structure of 2 can be considered either as Mo 2Pt phosphido-bridged trimer or a square-planar Pt II complex bonded to one chelating dppe and two anionic phosphine ligands. The latter PtP 4 description successfully accounts for the line broadening observed in the 31P{ 1H} NMR spectra of 2–4, which can be understood in terms of the existence of several interconverting rotameric forms arising from restricted rotation about the Pt-phosphido bond. The PtPMo angles of 122.1(1) and 123.5(1)° are some of the largest ever to be reported for phosphido-bridged heterometallics, reflecting the long PtMo separations [4.349(2) and 4.320(2) Å] and the electronic and structural flexibility of the phosphido bridge. The PtMo compound [Pt(μ-PPhH) 2{Mo-(CO) 4} (dppe)] (5), comprised of one neutral and one dianionic chelate ligand, was prepared from [Li] 2[Mo(CO) 5(PPhH) 2] and [PtCl 2(dppe)] and was shown to contain a conformationally rigid PtP 4 structure with characteristically sharp 31P resonances. The 31P{ 1H} NMR spectrum of 5 is rich with information analysing as two overlapping AA′XX′ spin systems together with their AA′XX′M (M = 195Pt) counterparts. The values of 2 J(P-P) and 1J( 195 Pt-P) are significantly lower for PPhH{Mo(CO) 5}− than dppe, a difference that cannot be accounted for solely on the basis of bond length variations. Meso-[Pt(μ-PPhH) 2{Mo(CO) 5} 2(dppe)] ( 2) is thermodynamically unstable, undergoing a rapid intramolecular elimination of [Mo(CO) 6] to generate [Pt(μ-PPhH) 2{Mo(CO) 4} (dppe)] (5), while its racemic diastereoisomer, that which was observed in the crystal, decomposes to unidentified phosphorus-containing products.

Distortion of OPO bond angles in phosphorus monoanions: Ab initio studies

Results are reported from ab initio studies of phosphinate anion H 2PO 2 − and phosphate anion, (HO) 2PO 2 − and the distortion of these anions by the biochemically important metal cations, Mg ++ and Zn ++. Ab initio results are reported from four basis sets for phosphinate ion and three basis sets for phosphate ion. We find that: 1) the results using the STO-3G ∗ basis set are in reasonable agreement with experimental data and with the calculation done with the large 6−31+ G ∗ basis set and second-order Møller-Plesset perturbation theory; 2) that phosphinate anion is an appropriate analog for studying the interactions of phosphate monoanion; 3) that the interaction with Mg ++ and Zn ++ is enough to cause the deformation previously hypothesized; 4) that correlations we have noted from experimental results are supported by the computational data; 5) that the OPO angle contracts significantly more on metal interactions than we predicted from our previous experimental studies using the one-bond, PH coupling constant; and 6) density matrix elements for interaction of the 3s orbital at phosphorous and 1s orbital at hydrogen correlate with one-bond, PH coupling constants.

Intramolecular nucleophilic substitution by phosphinate and thiophosphinate anions: relative rates of formation of five- and six-membered rings

In CH2Cl2 solution the phosphinate anion BrCH2CH2(CH2)nCH2(Ph)P(O)O– cyclises only 4,3 times faster when n= 0 (five-membered ring product) than when n= 1; for the thiophosphinate anion ClCH2CH2(CH2)nCH2(Ph)P(S)O– cyclisation (via sulfur) is still only 30 times faster when n= 0 than when n= 1.

Vier- und fünffach koordinierte Organometall-Phosphankomplexe von Aluminium, Gallium, Indium und Thallium / Four- and Five-Coordinate Organometal Phosphine Complexes of Aluminum, Gallium, Indium, and Thallium

The organometal phosphine complexes ML3 (L = [o-(Ph2PCH2)C6H4]-; M = Al3+, Ga3+, In3a+) are obtained from MC13 and the lithiated ligand in diethyl ether. Tl[o-(Ph2PCH2)C6H4]3 is prepared from T1C1 by a disproportionation reaction. M1 species could not be detected with L as ligand. Al[o-(Ph2PCH2)C6H4]3 is the first triorganoaluminum bis(phosphine) adduct where C3P2 pentacoordination at aluminum has been definitely proven for both the solution (δ(27Al) =131 ppm, w1/2 = 12 kHz) and the solid state (d(Al–P) = 2.676(3)/2.782(2) A). The trigonal-bipyramidal coordination geometry (C3P2) at Al is achieved by two of the anionic phosphines acting as chelating ligands, spanning equatorial (C atoms) and axial sites (P atoms), while the third phosphine is only carbon-bonded. Like AlL3, the heavier congeners ML3 (M = Ga, In, Tl) are stereochemically nonrigid molecules in solution. Surprisingly, in the solid state only InL3 resembles the aluminum complex (C3P2 penta-coordination) while GaL3 and T1L3 contain four-coordinate metal centers (C3P). This may be rationalized by the noticeably less polar Ga–P bonds as compared to Al–P and In–P bonds, while in T1L3 the span of the ligand is not sufficient to allow for chelating coordination at a five- (or six-)coordinate Tl center.

Sterisch belastete cyclische Phosphanborane / Sterically Crowded Cyclic Phosphine-Boranes

The anionic phosphine o-(diphenylphosphinomethyl)phenyl L has been used to prepare the sterically crowded cyclic phosphine-boranes BL3, tBuBL2, and tBu2BL by reaction of the lithiated ligand LiL with B(OMe)3, tBuB(OMe)2, and tBu2BOMe, respectively. In the new compounds tBuBL2 and tBu2BL one ligand L is bonded to the boron center by both its carbanionic and its phosphino function with formation of five-membered rings. In solution 11B and 31P NMR spectroscopy does not indicate substantial B—P dissociation, i.e., the existence of threecoordinate boron. The steric bulk of L in BL3 leads to the formation of oligomers in solution, presumably by a bridging coordination mode of L to two boron centers. No conclusive evidence as to the monomeric or oligomeric nature of BL3 in the solid state can be given, however. Five-membered ring formation is proven for the solid state by X-ray structure determinations of tBuBL2 and tBu2BL which in addition confirm that the steric bulk of L is superior to that of a tert. butyl group.

Coordination of bis(2-pyridyl)phosphinic acid as a tridentate ligand. Crystal structure of the {bis(2-pyridyl)phosphinato}{tris(2-pyridyl)-phosphine oxide}ruthenium(II) cation, [Ru{py 2P(O)O}{py 3PO}]BF 4·2H 2O

In the synthesis of the bis{tris(2-pyridyl)phosphine oxide}ruthenium(II) cation, [Ru(py 3PO) 2] 2+, the species {bis(2-pyridyl)phosphinato}{tris(2-pyridyl)phosphine oxide}ruthenium(II), [Ru{py 3PO}- {py 2P(O)O}]4 +, was also isolated. The latter cation has been characterized by a structural determination and is the first example of a tridentate phosphinate anion. The electrochemical and spectral properties of both cations are reported. Crystals of [Ru{py 2P(O)O}{py 3PO}]BF 4·H 2O crystallize in the monoclinic space group P2 1/ n with unit cell dimensions a=16.128(7), b=11.493(6), c=17.576(11) Å, β=102.64(4)°, V=3178.9 Å 3, Z=4. The structure was refined by a full-matrix least-squares procedure, and converged with R=0.107 and R w=0.108 for 1172 reflections.

31P NMR Study on the binding isomers of chromium(III) phosphinate complexes in solution

A 31P NMR study on the structure of chromium(III) phosphinate complexes has been made. The formation of the outer-sphere complexes gave a downfield shift of the 31P NMR signal, though the signal could not be separated from that of free phosphinate anion due to their great lability. On the other hand, the inner-sphere complexes gave an upfield shift of the signal separated from that of outer-sphere type. Furthermore, it was found that the signal for the inner-sphere complex has two peaks, one being due to non-chelate binding and the other being due to chelate binding. By distinguishing these binding modes, based on the experimental evidence, a large number of new isomers for chromium(III) phosphinate have been revealed.

A New Heptanuclear Tin Cluster Containing Sulfur and Oxygen in the Framework

Abstract We have recently reported that new structural forms having the cube, (n-BuSn(O)O2PPh2)4, and oxygen-capped, [(n-BuSn(OH)O2PPh2)3O] [O2PPh2], formulations can be prepared by the reaction of n-butylstannonic acid with the corresponding diorganophosphinic acid. In new work exploring the effects of the bulky mesityl group bound to phosphorus, a cube formulation was also obtained. When n-butylstannonic acid was reacted with dicyclohexylphosphinic acid in the presence of nitric acid an oxygen-capped cluster having nitrate as the anion was obtained, demonstrating that the phosphinate anion is not required to stabilize the o-capped cation. In an attempt to generate similar structural forms, with sulfur replacing oxygen in the framework, the reaction of n-butylstannonic acid with diphenylphosphine oxide in the presence of elemental sulfur has been explored. From this reaction, a new structural form, containing seven hexacoordinate tin atoms and incorporating sulfur into the framework, [(n-BuSn(S)O2PPh2)3O...

Synthesis of a lariat ether having a phosphinic acid functional group and the crystal structure of its sodium(1+) complex: sodium sym-[(dibenzo-14-crown-4-oxy)methyl]phenylphosphinate dihydrate diethanolate

A dibenzo-14-crown-4 ether with a pendant arm carrying a phosphinic acid moiety was synthesized and the crystal structure of its sodium salt determined by x-ray diffraction methods. The V-shaped macrocycle is almost identical with the unsubstituted version and has its four ether O atoms oriented to one side in a plane. The Na/sup +/ ion is bonded to these atoms and is 1.5 /angstrom/ above the plane; it is also bonded to the O atom of the oxymethyl side arm and to the O atoms of one water and one ethanol molecule. The phosphinate anion does not coordinate directly to the Na/sup +/ ion but is attached indirectly through an intermediate H/sub 2/O molecule. A hydrogen bonding network joins the complex molecules into dimers that interact with each other in the crystal only through van der Walls contacts. The acid and the salt were also characterized by ir and NMR spectroscopy, and the pK/sub a/ was determined to be 4.5 in 80% methanol-water. Crystallographic data for NaPC/sub 29/H/sub 42/O/sub 11/: monoclinic, a = 18.439 (2) /angstrom/, b = 8.680 (1) /angstrom/, c = 20.606 (1) /angstrom/, /beta/ = 102.95 (1)/degree/, space group P2/sub 1//n, Z = 4. 28 refs., 2more » figs., 5 tabs.« less

Phosphine complexes of main group elements: phosphinomethyl substituted aluminates as anionic phosphine ligands to lithium and X-ray structure of Me2Al(CH2PMe2)2Li(Me2NCH2CH2NMe2)

Anionic aluminates or the type [MexAl(CH2PMe2)4 –x]– were synthesized and shown to co-ordinate to a Li+ ion; according to an X-ray structure determination [Me2Al(CH2PMe2)2Li(Me2NCH2CH2NMe2)] contains a six-membered Al(C–P)2Li heterocycle.