Amido Ln(II) Complexes Coordinated by Bi- and Tridentate Amidinate

Jan 11, 2016 - Heteroleptic Ln(II) and Ca(II) amides coordinated by bi- and tridentate ... Citation data is made available by participants in CrossRef...
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Amido Ln(II) Complexes Coordinated by Bi- and Tridentate Amidinate Ligands: Nonconventional Coordination Modes of Amidinate Ligands and Catalytic Activity in Intermolecular Hydrophosphination of Styrenes and Tolane Ivan V. Basalov, Olga S. Yurova, Anton V. Cherkasov, Georgy K. Fukin, and Alexander A. Trifonov* Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, GSP-445, 630950 Nizhny Novgorod, Russia S Supporting Information *

ABSTRACT: Heteroleptic Ln(II) and Ca(II) amides [tBuC(NC6H3iPr2-2,6)2]MN(SiMe3)2(THF) (M = Yb (1Yb), Ca (1Ca)), [2MeOC6H4NC(tBu)N(C6H3-iPr2-2,6)]LnN(SiMe3)2(THF) (Ln = Sm (2Sm), Yb (2Yb)), and [2-Ph2P(O)C6H4NC(tBu)N(C6H3-Me2-2,6)]YbN(SiMe3)2(THF) (3Yb) coordinated by bi- and tridentate amidinate ligands were obtained by the amine elimination reactions of M[N(SiMe3)2](THF)2 (M = Yb, Sm, Ca) with parent amidines in good yields. Complex [tBuC(NC6H3-iPr2-2,6)2]SmN(SiMe3)2 can be obtained only by a salt metathesis reaction of [tBuC(NC6H3-2,6iPr2)2]SmI(THF)2 with NaN(SiMe3)2. Unlike 1Yb and 1Ca in 1Sm the amidinate ligand is coordinated to metal ion in κ1amido:η6-arene fashion preventing THF coordination. The derivatives of tridentate amidinate ligands bearing pendant donor 2MeOC6H4 or 2-Ph2P(O)C6H4N groups feature nonconventional κ1-N,κ2-O,η6-arene coordination mode. Complexes 1Ca, 1Sm, 1Yb, 2Sm, 2Yb, and 3Yb proved to be efficient catalysts for styrene hydrophosphination with PhPH2 and Ph2PH. In styrene hydrophosphination with PhPH2 all the catalysts perform excellent chemoselectivity and afford a monoaddition product secondary phosphine (PhCH2CH2)PhPH. Moreover, all the catalysts perform hydrophosphination reactions regioselectively with exclusive formation of the anti-Markovnikov addition product. Within the series of complexes coordinated by the same amidinate ligand catalytic activity decreases in the following order 1Ca ≥ 1Sm>1Yb. The turnover frequencies were in the range of TOF ≈ 0.3−0.7 h−1. However, application of tridentate amidinate ligand allowed one to increase catalytic activity significantly: for 2Sm TOF was found to be 8.3 h−1. For the addition of PhPH2 to para-substituted styrenes catalyzed by 2Sm it was found that electron-withdrawing substituents (Cl, F) do not affect the reaction rate while electron-donating groups (tBu, OMe) noticeably slow down the reaction.

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chelating monoanionic amidinate fragment [RC(NR)2]− which forms stable complexes with various metal ions across the periodic table of elements14 presents a useful platform for “tailoring” new versatile ligand systems. Amidinate ligands have been successfully employed in Ln(II) chemistry and allowed for the synthesis and isolation of a series of highly reactive species.13b,15 Herein, we report on the synthesis, structures of new heteroleptic Ln(II) amido species coordinated by bi- and tridentate amidinate ligands, and their catalytic activity in intermolecular olefin hydrophosphination.

INTRODUCTION Despite the progress which has been done in the field of the chemistry of Ln(II) complexes during the past two decades1 their catalytic properties still remain poorly explored. This is somewhat surprising since the large ionic radii of Ln(II) ions2 in combination with their strong reducing properties3 make them promising objects for catalytic applications. Organic derivatives of Ln(III) are well reputed as efficient catalysts (or precatalysts) for various transformations involving unsaturated substrates, e.g., polymerization,4 hydrogenation,5 hydrosilylation,6 hydroamination,7 hydrophosphination,8 hydroalkoxylation,9 hydrothiolation,9 and hydroboration.10 Only recently first reports on catalytic activity of organic derivatives of Ln(II) in olefin polymerization11 and hydrosilylation12 appeared. Hydroelementation reactions consisting in addition of E−H functionalities across C−C multiple bonds are atom-economic processes for the synthesis of valuable compounds that may be one of the prospective application fields of such divalent lanthanide complexes. Recent achievements in intermolecular hydroelementation reactions promoted by Ln(II)13 inspired us to synthesize new heteroleptic Ln(II) amido complexes. The © XXXX American Chemical Society

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RESULTS AND DISCUSSION Synthesis. Am in e elimination reactions from [(Me3Si)2N]2M(THF)2 (M = Yb,16 Sm,17 Ca18) were used as a synthetic approach to a series of heteroleptic M(II)−amido complexes coordinated by amidinate ligands differening in denticity and the nature of pendant donor groups. The reactions of equimolar amounts of [(Me3Si)2N]2M(THF)2 (M Received: October 23, 2015

A

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry Scheme 1. Synthesis of Complexes 1Yb and 1Ca

Scheme 2. Synthesis of Complexes 1SmI and 1Sm

Scheme 3. Synthesis of Complexes 2Sm, 2Yb, and 3Yb

mixture. This can be indicative of two reactions occurring in the mixture: transamination and oxidation of [(Me3Si)2N]2Sm(THF)2 by 1. Unfortunately, all attempts to obtain the reaction products in individual state were unsuccessful. However, we succeeded to synthesize Sm(II) amide 1Sm via the successive salt metathesis reactions starting from SmI2(THF)3 (Scheme 2). It has been reported that the salt metathesis reaction of equivalent amounts of SmI2(THF)3 and potassium amidinate 1K in THF after recrystallization of the reaction product from hexane afforded a dimeric iodoamidinate [{tBuC(NC6H3-2,6iPr2)2}Sm(THF)(μ-I)]2.15b However, when recrystallization of the reaction product was carried out from the THF−hexane mixture we isolated a monomeric Sm(II) complex [tBuC(NC6H3-2,6-iPr2)2]SmI(THF)2 (1SmI, 72% yield) containing one additional THF molecule coordinated to the metal center (Scheme 2). The reaction of 1SmI with NaN(SiMe3)2 was carried out in THF, and recrystallization of the reaction product from hexane allowed for isolation of amido complex [tBuC(NC6H3-2,6-iPr2)2]SmN(SiMe3)2 (1Sm) in 57% yield.

= Yb, Sm, Ca) and proligands 1−3 (Schemes 1 and 3) were carried out in toluene at ambient temperature or under moderate heating (70 °C). Recently, we reported that the reaction of [(Me3Si)2N]2Yb(THF)2 and 1 afforded an Yb(II) amide coordinated by amidinate ligand [tBuC(NC6H3-iPr2-2,6)2]YbN(SiMe3)2(THF) (1Yb) in 60% yield.15 The calcium analogue [tBuC(NC6H3-iPr2-2,6)2]CaN(SiMe3)2(THF) (1Ca) was formerly prepared starting from CaI2 through a series of salt metathesis reactions in 53% yield,19 and its synthesis and structure were published in 2014. At the same time we synthesized complex 1Ca via the amine elimination approach which provided 66% yield (Scheme 1). The attempt of preparation of the samarium analogue via the transamination reaction failed. The reaction of equimolar amounts of [(Me3Si)2N]2Sm(THF)2 and 1 afforded a brown viscous oil after removal of the volatiles in vacuum. The GC analysis of the volatiles determined the presence of ∼20% of the expected amount of (Me3Si)2NH, which should form in the transamination reaction. At the same time no remaining [(Me3Si)2N]2Sm(THF)2 and 1 were found in the reaction B

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry It is noteworthy that unlike 1Yb and 1Ca complex 1Sm despite a larger ion size of Sm2+ (effective ionic radii for CN = 6; Yb2+, 1.02 Å; Sm2+, 1.22 Å; Ca2+ 1.00 Å)2 crystallizes without coordinated THF molecule. For highly oxophilic Ln(II) ion this becomes possible due to κ1-amido:η6-arene coordination of the amidinate ligand. Such a nonconventional coordination mode of the amidinate ligand has been documented for a series of Yb(II) and Sm(II) species.15,20,21 Earlier by the example of a series of Yb(II) and Yb(III) complexes it was demonstrated that the coordination mode of the [tBuC(NC6H3-2,6-iPr2)2]− ligand is dependent on metal ion size: oxidation of Yb(II) to Yb(III) results in the change of coordination mode from κ1amido:η6-arene to a “classical” κ1,κ1-N,N-chelating one.15,20,21 The fact that Sm(II) complexes 1SmI, 1Sm, and [{tBuC(NC6H3-2,6-iPr2)2}Sm(THF)(μ-I)]215b despite the coordination number of the metal ion exhibit κ1-amido:η6-arene coordination is in line with this observation. Recently, two new tridentate amidines bearing in the side chain a pendant Lewis base 2-MeOC6H4NC(tBu)NH(2,6iPr2C6H3) (2)22a and 2-[Ph2P(O)]C6H4NHC(tBu) = N(2,6Me2C6H3) (3)22b were synthesized in our group. We reported on the synthesis and structure of complex 2Yb which was obtained by amine elimination reaction of [(Me3Si)2N]2Yb(THF)2 with amidine 2.13a In this study using the same synthetic approach we succeeded to obtain the Sm(II) analogue 2Sm (Scheme 3). The reaction of [(Me3Si)2N]2Sm(THF)2 with 2 was carried out in toluene at ambient temperature and afforded 2Sm after recrystallization from hexane as black crystals in 50% yield. Amidine 3 also cleanly reacts with [(Me3Si)2N]2Yb(THF)2 under similar conditions, resulting in complex 3Yb in 88% yield. It should be mentioned that despite the difference of the ionic sizes of Yb(II) and Sm(II) complexes 2Sm, 2Yb, and 3Yb feature η6-arene coordination of the aryl substituent to Ln(II) ions. This indicates that the presence of an O-containing donor group in the side chain of the amidinate ligand along with metal ion size are crucial for the coordination mode. X-ray Diffraction Studies of Complexes 1Ca, 1SmI, 1Sm, 2Sm, and 3Yb. Structure of 1Ca. Transparent crystals of 1Ca suitable for X-ray study were obtained by slow concentration of hexane solution at room temperature. The molecular structure of 1Ca is depicted in Figure 1, and the structure refinement data are listed in Table S1 (see ESI). The molecular structure of 1Ca was established by the X-ray diffraction study which revealed that complexes 1Ca and 1Yb are isomorphous. The M−N bond distances in complexes 1Ca (Ca−Namido 2.2778(9) Å; Ca−Namidinate 2.3604(9), 2.3592(8) Å) and 1Yb (Yb−Namido 2.303(3) Å; Yb−Namidinate 2.378(3), 2.377(3) Å)2 have similar values taking into account the difference of ionic radii of these metals. Structure of 1SmI. Crystals of 1SmI suitable for X-ray study were obtained by slow concentration at room temperature of the solution in THF/hexane (1:2) mixture. Complex 1SmI crystallizes as a solvate 1SmI·THF. The molecular structure of complex 1SmI is depicted in Figure 2, and the structure refinement data are listed in Table S1 (see ESI). The X-ray study revealed that unlike most Ln(II) iodo complexes 1SmI adopts a monomeric structure with a terminal iodo ligand. The coordination environment of the Sm(II) ion in 1SmI is set up by a terminal iodo ligand, one nitrogen atom of the amidinate ligand, and two oxygen atoms of THF molecules. Moreover, one of the 2,6-iPr2C6H3 rings is η6coordinated to the Sm ion, resulting in the short Sm−C

Figure 1. Molecular structure of [tBuC(NC6H3-iPr2-2,6)2]CaN(SiMe3)2(THF) (1Ca). Hydrogen atoms, methyl fragments of the iPr groups, and carbon atoms of the THF molecule are omitted for clarity; thermal ellipsoids drawn at the 30% probability level. Bond lengths (Angstroms) and angles (degrees): Ca(1)−N(3) 2.279(2), Ca(1)−O(1) 2.345(2), Ca(1)−N(1) 2.359(1), Ca(1)−N(2) 2.360(2), N(1)−C(1) 1.344(2), N(1)−C(6) 1.419(2), N(2)−C(1) 1.342(2), N(2)−C(18) 1.419(2), N(3)−Ca(1)−O(1) 100.08(6), N(3)−Ca(1)−N(1) 134.61(5), O(1)−Ca(1)−N(1) 114.20(5), N(3)−Ca(1)−N(2) 132.96(5), N(2)−C(1)−N(1) 112.1(1), C(1)− N(1)−C(6) 128.9(2).

Figure 2. Molecular structure of [tBuC(NC6H3-iPr2-2,6)2]SmI(THF)2(1SmI). Hydrogen atoms, methyl fragments of the iPr groups, and carbon atoms of the THF molecules are omitted for clarity; thermal ellipsoids drawn at the 30% probability level. Bond lengths (Angstroms) and angles (degrees): Sm(1)−O(2S) 2.562(2), Sm(1)−O(1S) 2.580(2), Sm(1)−N(2) 2.580(2), Sm(1)−Arcenter 2.676(1), Sm(1)−I(1) 3.2389(3), N(2)−C(1) 1.358(3), N(1)−C(1) 1.311(3), N(2)−Sm(1)−I(1) 131.57(5), O(2S)−Sm(1)−I(1) 80.14(5), O(1S)−Sm(1)−I(1) 96.76(5), O(2S)−Sm(1)−C(6) 159.81(7), O(1S)−Sm(1)−C(6) 114.00(6).

distances. The average Sm−C bond distance (3.021(3) Å) in 1SmI is shorter than that in complex Cp*Sm(BPh4), which also exhibits η6-interaction between Sm(II) ion and a phenyl ring C

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry (3.08 Å)23 but slightly longer compared to a related dimeric complex [{tBuC(NC6H3-2,6-iPr2)2}Sm(THF)(μ-I)]2 (2.997 Å).15b The Sm−I bond in 1SmI exhibits a length (3.2389(3) Å) similar to that in seven-coordinate monomeric Sm(II) iodo complex [(DIP2pyr)LnI(THF)3] (DIP2pyr =2,5-bis{N-(2,6diisopropylphenyl)imino methyl}pyrrolyl (3.2233(9) Å),24 but it is slightly longer than the Sm−I bond in six-coordinate complex [(TptBu,Me)SmI(THF)2] (3.1908(9) Å, TptBu,Me = tris(pyrazolyl)borate).25 The Sm−N bond in 1SmI (2.580(2) Å) is somewhat longer than the appropriate bond in [{tBuC(NC6H3-2,6-iPr2)2}Sm(THF)(μ-I)]2 (2.552(4) Å).15b Coordination of the amidinate ligand in κ1-amido:η6-arene fashion affects the geometric parameters of the NCN fragment in 1SmI. Unlike the κ1,κ1-N,N-chelating coordination featuring similar C−N bond distances in amidinate fragment26 as a result of negative charge delocalization within NCN fragment in 1SmI the amidinate C−N bonds are not equivalent. The length of one bond, 1.311(3) Å, is consistent with its double-bond character,28 while the length of the second one (1.358(3) Å) is close to the length of a single C−N bond.28 Structure of 1Sm. Crystals of 1Sm suitable for X-ray study were obtained by slow concentration at −18 °C from hexane. The molecular structure of complex 1Sm is depicted in Figure 3, and the structure refinement data are listed in Table S1 (see

molecules and the Sm(II). The Sm−Namido bond (2.4370(15) Å) in 1Sm is noticeably shorter than the corresponding bond in seven-coordinate Sm(II) amido phenolate complex {LONO4}Sm(N(SiMe3)2) (2.560(7) Å).13b The bond between Sm(II) ion and the amidinate nitrogen in 1Sm 2.524(3) Å is shorter than that in 1SmI (2.580(2) Å). Structure of 2Sm. Recently, we reported on the synthesis and structural characterization of complex 2Yb.13a The crystals of samarium congener 2Sm suitable for X-ray study were obtained by slow concentration of the hexane solution at room temperature. The molecular structure of complex 2Sm is depicted in Figure 4, and the structure refinement data are

Figure 4. Molecular structure of [2-MeOC6H4NC(tBu)N(C6H3-iPr22,6)]Sm[N(SiMe3)2](THF) (2Sm). Hydrogen atoms, methyl fragments of the iPr groups, and carbon atoms of the THF molecule are omitted for clarity; thermal ellipsoids drawn at the 30% probability level. Bond lengths (Angstroms) and angles (degrees): Sm(1)−N(3) 2.472(2), Sm(1)−N(1) 2.571(2), Sm(1)−O(2) 2.593(2), Sm(1)− O(1) 2.602(2), Sm(1)−Arcenter 2.762(1), N(2)−C(8) 1.301(3), N(1)−C(8) 1.380(3); N(3)− Sm(1)−N(1) 120.85(6), N(3)− Sm(1)−O(2) 108.84(6), N(1)−Sm(1)−O(2) 113.31(5), N(3)− Sm(1)−O(1) 87.23(6), N(1)− Sm(1)−O(1) 62.06(5), O(2)− Sm(1)−O(1) 80.35(5). Figure 3. Molecular structure of [tBuC(NC6H3-iPr2-2,6)2]SmN(SiMe3)2 (1Sm). Hydrogen atoms and methyl fragments of the iPr groups are omitted for clarity; thermal ellipsoids drawn at the 30% probability level. Bond lengths (Angstroms) and angles (degrees): Sm(1)−N(3) 2.437(3), Sm(1)−N(1) 2.524(3), Sm(1)−Arcenter 2.657(2), Sm(1)−C(6) 3.055(4), Sm(1)−Si(2) 3.440(1), N(1)− C(1) 1.353(5), N(1)−C(6) 1.410(5), N(2)−C(1) 1.312(5), N(3)− Sm(1)−N(1) 137.9(1), N(3)−Sm(1)−C(18) 163.7(1), N(1)− Sm(1)−C(18) 56.0(1), N(2)−C(1)−N(1) 119.8(4), N(1)−Sm(1)− C(6) 27.2(1).

listed in Table S1 (see ESI). Complex 2Sm has a structure similar to 2Yb; however, these compounds are not isomorphous (complex 2S crystallizes in P21/c space group, while 2Yb in P−1). Similarly to 2Yb complex, 2Sm is bound to one nitrogen of the N(SiMe3)2− group, one oxygen atom of the THF molecule, and the tridentate amidinate ligand. The monoanionic amidinate ligand in 2Sm is coordinated to the metal center in a rare κ1-N,κ2-O,η6-arene fashion. It should be noted that the range of the Sm−C distances in 2Sm (2.987(2)−3.219(2) Å) is much larger compared to 1Sm (2.957(4)−3.022(4) Å) and 1SmI (2.952(2)−3.055(3) Å). The average Sm−C bond length in 2Sm (3.095(2) Å) is larger than that in 1Sm (3.004(4) Å) and 1SmI (3.021(3) Å). Such a perturbation of the Sm−arene interaction is obviously due to additional coordination of the OMe group to Sm(II) ion. The Sm−Namidinate bond distance in 2Sm (2.571(2) Å) matches that in 1SmI (2.580(2) Å), while the Sm−Namido bond (2.472(2) Å) is expectedly longer than that in 1Sm (2.437(3) Å). Structure of 3Yb. The crystals of 3Yb suitable for X-ray study were obtained by slow concentration of the hexane

ESI). According to the X-ray study heteroleptic amide complex 1Sm adopts a monomeric structure. Similarly to 1SmI, the amidinate ligand in 1Sm is coordinated to the Sm(II) ion in κ1amido:η6-arene fashion. The average Sm−C distance (3.004(4) Å) is slightly shorter than that in 1SmI. Moreover, a short contact (3.055(4) Å) between Sm(II) ion and the ipso-carbon of the second 2,6-iPr2C6H3 ring was detected in 1Sm. It is noteworthy that despite the strong oxophilic nature of lanthanide ions and the fact that the synthesis was carried out in THF complex 1Sm does not contain coordinated THF D

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry solution at room temperature. The molecular structure of complex 3Yb is depicted in Figure 5, and the structure

Scheme 4. Catalytic Hydrophosphination of Styrene with PhPH2

Table 1. Catalytic Hydrophosphination of Styrene with PhPH2 no.

precat.

t [h]

convc [%]

sec-P/tert-Pd [%]

a

3Yb 3Yb 3Yb 2Yb 2Sm 2Sm 2Sm 1Ca 1Yb 1Sm

2 24 2 70 2 6 4 70 70 70

26 30 92 86 63 100 99 100 41 94

98:2 97:3 98:2 95:5 97:3 95:5 97:3 96:4 99:1 95:5

1 2a 3b 4b 5a 6a 7b 8b 9b 10b a

Figure 5. Molecular structure of [2-Ph2POC6H4NC(tBu)N(C6H3Me2-2,6)]Yb[N(SiMe3)2] (3Yb). Hydrogen atoms, methyl fragments of the iPr groups, and carbon atoms of Ph groups are omitted for clarity; thermal ellipsoids drawn at the 30% probability level. Bond lengths (Angstroms) and angles (degrees): Yb(1)−O(1) 2.279(1), Yb(1)−N(3) 2.315(2), Yb(1)−N(1) 2.497(2), Yb(1)−P(1) 3.3120(4), P(1)−O(1) 1.507(1), O(1)−Yb(1)−N(3) 101.29(5), O(1)−Yb(1)−N(1) 78.03(5), N(3)−Yb(1)−N(1) 131.95(5), O(1)−Yb(1)−C(24) 113.69(5).

Reaction[styrene]0/[PhPH2]0/[Precat]0 = 50:50:1 in C6D6, [precat]0 = 17.5 mM, T [°C] = 60 unless otherwise specified. The formation of secondary phosphine was 100% anti-Markovnikov regiospecific, as established by NMR spectroscopy. bReaction in neat substrates with [precat]0 = 80.5 mM, T [°C] = 60. cConversion of styrene, as determined by NMR spectroscopy. dProduct chemoselectivity determined by 31P NMR spectroscopy.

preliminary studies such a high chemoselectivity results from kinetic control due to the large difference in the values of the rate constants of addition of primary PhPH2 and secondary (PhCH2CH2)PhPH phosphines to styrenic substrates. Moreover, all catalysts perform hydrophosphination reactions regioselectively with exclusive formation of the anti-Markovnikov (or 2,1) addition product. As previously demonstrated by Hill29 and Carpentier30 for intermolecular styrene hydroelementations, 2,1-addition to a CC double bond favors stabilization of a polarized four-membered transition state at the alkene insertion step due to delocalization of the anionic charge at benzylic carbon adjacent to the metal ion to the phenyl ring of styrene. We assume that the same scenario operates in our case. Both the metal ion and the ligand were found to affect the catalytic activity. Thus, within the series of complexes coordinated by the same amidinate ligand catalytic activity decreases in the following order 1Ca ≥ 1Sm > 1Yb (Table 1, entries 8−10). The turnover frequencies were in the range of TOF ≈ 0.3−0.7 h−1. However, application of tridentate amidinate ligand allowed one to increase catalytic activity significantly: for 2Sm TOF was found to be 8.3 h−1. To assess the influence of the electronic properties of styrenic substrate on reaction rate a series of catalytic tests of hydrophosphination of styrenes bearing various substituents in the para position of the aromatic ring with PhPH2 was carried out. A number of functional groups were found to be tolerated for the hydrphosphination of styrene. Complex 2Sm which demonstrated the highest catalytic activity in hydrophosphination of unsubstituted styrene was chosen as a catalyst. It was found that electron-withdrawing substituents (Cl, F) do not affect the reaction rate (Table 2, entries 2 and 3), while for styrenes containing electron-donating groups (tBu, OMe) a noticeable decrease of the reaction rate was detected (Table 2, entries 5 and 6). Unexpectedly in the case of p-Me-styrene having an electron-donating Me substituent the reaction rate

refinement data are listed in in Table S1 (see ESI). Complex 3Yb crystallizes as a solvate 3Yb·C6H14. The X-ray study revealed that similarly to 2Yb and 2Sm in complex 3Yb the amidinate ligand is tridentate and coordinated to the Yb(II) ion in κ1-N,κ2-O,η6-arene fashion. However, despite the similar denticity of amidinate ligands in 2Yb and 3Yb the latter does not contain a coordinated THF molecule. Obviously this results from higher degree of steric saturation of the Yb(II) coordination sphere in the case of the six-membered metallacycle 3Yb compared to a five-memebered in 2Yb. Thus, the bite angle N−Yb−O in 3Yb (78.03(5)°) is noticeably larger compared to 2Yb (64.85(3)°). The Yb−C distances in 3Yb fall into a rather narrow range 2.769(2)−2.906(2) Å (compare to 2.886(3)−3.157(3) Å for 2Yb). The average Yb−C (2.844(2) Å) and Yb−Namido (2.315(2) Å) bond distances in 3Yb are expectedly shorter than those in 2Yb (3.034(3) and 2.368(2) Å, respectively) due to different coordination numbers of the metal centers. The same trend was found for the Yb−O bond (3Yb 2.2799(11) Å; 2Yb 2.483(2) Å), while the Yb−Namidinate bond in 3Yb (2.4971(14) Å) is somewhat longer compared to that in 2Yb (2.452(2) Å). Hydrophosphination Catalysis. Complexes 1Ca, 1Sm, 1Yb, 2Sm, 2Yb, and 3Yb were evaluated as precatalysts in intermolecular hydrophosphination of styrene with PhPH2 and Ph2PH. The catalytic tests were performed either in neat substrates ([styrene]:[PhPH2] = 1:1) or in C6D6 solution at 60 °C in the presence of 2 mol % of precatalyst (Scheme 4). The representative results are listed in Table 1. Complexes 1Sm, 1Yb, 1Ca, 2Sm, 2Yb, and 3Yb turned out to be able to mediate styrene hydrophosphination. All catalysts were found to be highly chemoselective and afford a monoaddition productsecondary phosphine (PhCH2CH2)PhPH with selectivity typically over 95%.28 According to our E

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Yb complexes 1Yb, 2Yb, and 3Yb tridentate amidinate ligand with pendant Ph2PO group provides the highest catalytic activity (58%, 26%, and 100% conversions). All catalysts perform hydrophosphination reactions with exceptional regioselectivity, affording exclusively anti-Markovnikov addition product. Complexes 1Sm, 1Yb, 1Ca, 2Sm, 2Yb, and 3Yb enable addition of PhPH2 to the internal triple CC bond of tolane (Scheme 6). The results are presented in Table 4. Complete

Table 2. Catalytic Hydrophosphination of Para-Substituted Styrenes with PhPH2 no.

precat.

t [h]

styrene

convb [%]

sec-P/tert-Pc [%]

1a 2a 3a 4a 5a 6a

2Sm 2Sm 2Sm 2Sm 2Sm 2Sm

4 4 4 4 4 4

p-H-styrene p-F-styrene p-Cl-styrene p-Me-styrene p-tBu-styrene p-OMe-styrene

99 88 99 90 30 14

97:3 98:2 97:3 96:4 100:0 100:0

a

Reaction[styrene]0/[PhPH2]0/[Precat]0 = 50:50:1 in neat substrates with [precat]0 = 80.5 mM. T [°C] = 60. The formation of secondary phosphine was 100% anti-Markovnikov regiospecific, as established by NMR spectroscopy. bConversion of styrene, as determined by NMR spectroscopy. cProduct chemoselectivity determined by 31P NMR spectroscopy.

Scheme 6. Catalytic Hydrophosphination of Tolane with PhPH2

remains comparable to that of unsubstituted styrene (Table 2, entry 4). These results are consistent with the previously reported observations of Hill29 and Carpentier,30 which were rationalized by the stabilization of the partial negative charge on the benzylic carbon atom in polarized four-membered ring at the rate-determining step due to electron-withdrawing para substituents. In contrast the electron-donating para substituents in the phenyl ring tend to destabilize this transition state. Complexes 1Sm, 1Yb, 1Ca, 2Sm, 2Yb, and 3Yb proved to be able to evolve into styrene hydrophosphination not only primary PhPH2 but also secondary phosphine Ph2PH (Scheme 5). The catalytic tests were carried out in neat substrates at

Table 4. Catalytic Hydrophosphination of Tolane with PhPH2

convb [%]

1 2 3 4 5 6

3Yb 2Yb 2Sm 1Ca 1Yb 1Sm

2 2 2 2 2 2

100 26 100 100 58 100

convb [%]

E/Zc [%]

2 3 4 5 6 7

3Yb 2Yb 2Sm 1Ca 1Yb 1Sm

70 70 70 70 70 70

100 37 35 84 56 24

36:64 33:67 28:72 58:42 70:30 83:17

conversion of substrates was reached when complex 3Yb was employed. High conversion (84%) was also detected for complex 1Ca. Surprisingly, in the series of complexes 1Sm, 1Yb, and 1Ca a complex of Sm despite having largest ionic radius displayed the lowest activity (24% vs 56% for 1Yb). Complexes 2Yb and 2Sm had low catalytic activities (37% and 35%, respectively). Tolane hydrophosphinations mediated by all complexes afford mixtures of E- and Z-isomers. The highest selectivity in the formation of E-isomer was observed for 1Sm (E:Z = 83:17).

Table 3. Data for the Hydrophosphination of Styrene with Ph2PH t [h]

t [h]

Reactions were carried out in neat substrates. [Tolane]0/[PhPH2]0/ [Precat]0 = 50:50:1, T [°C] = 60. bConversion of tolane and PhPH2 was determined by 1H and 31P NMR spectroscopy cFormation of E and Z addition products established by 31P NMR spectroscopy. Reaction time is not optimized.

precatalyst concentration 2 mol % at 60 °C. The results of the catalytic tests are compiled in Table 3. Surprisingly, despite the

precat.

precat.

a

Scheme 5. Catalytic Hydrophosphination of Styrene with Ph2PH

no.

no.

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CONCLUSIONS We found that the reactions of M[N(SiMe3)2](THF)2 (M = Yb, Sm, Ca) with amidines 1−3 cleanly occur in toluene under mild conditions and afford in good yields the related heteroleptic amido-amidinates 1Yb, 1Ca, 2Yb, 2Sm, and 3Yb. Exceptionally, complex 1Sm cannot be obtained via an amine elimination reaction but only by successive salt metathesis reactions. Matching our previous observations that bigger ion size favors κ1-amido:η6-arene coordination of the amidinate ligand complexes 1Sm and 1SmI exhibit this coordination mode of [tBuC(NC6H3-iPr2-2,6)2]−. The κ1-amido:η6-arene coordination of the amidinate ligand allows one to prevent THF coordination and isolation of 1Sm as a THF-free complex in contrast to 1Ca and 1Yb. The present study also demonstrated that the coordination mode of the amidinate ligand besides the metal ion size also depends on denticity. Thus, if an amidinate ligand has a pendant donor group (OMe or Ph2PO) for both Sm(II) and Yb(II) κ1-N,κ2-O,η6-arene coordination was detected.

a

Reaction [styrene]0/[Ph2PH]0/[Precat]0 = 50:50:1, T [°C] = 60. The formation of sec-P was 100% anti-Markovnikov regiospecific, as established by NMR spectroscopy. b Conversion of styrene, determined by NMR spectroscopy.

higher steric demand of Ph2PH vs PhPH2 the addition reactions of the former to styrene occur much faster. Thus, for catalysts 1Ca and 1Sm total conversion of substrates in the case of Ph2PH was reached in 2 h, while for PhPH2 it required 70 h. It is noteworthy that for both phosphines complexes 1Ca and 1Sm have higher catalytic activity compared to the Yb compound. Complex 2Sm was much more efficient in styrene hydrophosphination with Ph2PH compared to the ytterbium analogue 2Yb (100% vs 26%). Interestingly, within the series of F

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

57.55; H, 8.41; N, 5.75; Sm, 20.59. Found: C, 57.24; H, 8.19; N, 6.00; Sm, 20.37. Synthesis of [tBuC(NC6H3-iPr2-2,6)2]CaN(SiMe3)2(THF) (1Ca). A solution of [{tBuC(NC6H3-2,6iPr2)2}H] (0.737 g, 1.75 mmol) in toluene (10 mL) was added to a solution of Ca[N(SiMe3)2](THF)2 (0.885 g, 1.75 mmol) in toluene, and the reaction mixture was heated at 70 °C for 70 h. The volatiles were removed in vacuum, and the solid residue was dissolved in hexane. Slow concentration of the hexane solution at room temperature resulted in the formation of yellow crystals. The mother liquid was decanted, and the crystals were washed with cold hexane and dried in a vacuum at room temperature for 30 min. Complex 1Ca was isolated in 66% yield (0.800 g). 1H NMR (400 MHz, C6D6): δ = 0.05 (s,18H, SiMe3), 1.02 (s, 9H, C(CH3)3), 1.27 (m, 4H, β-CH, THF), 1.28 (d, 3JHH = 6.8 Hz, 12H, CH(CH3)2), 1.37 (d, 3JHH = 6.8 Hz, 12H, CH(CH3)2), 3.5 (sept, 3JHH = 6.8 Hz, 4H, CH(CH3)2), 3.7 (m, 4H, α-CH, THF), 7.05−7.15 (complex m, together 6H, CH Ar). 13C NMR (101 MHz, C6D6) δ = 4.8 (SiCH3), 22.6 (C(CH3)3), 25.8 (CH(CH3)2), 28.5 (β-CH2, THF), 30.7 (CH(CH3)2), 45.1 (C(CH3)3), 69.2 (α-CH2, THF), 122.3 (p-CH, C6H3), 123.1 (m-CH, C6H3), 140,1 (o-C, C6H3), 146.3 (ipso-C, C6H3). IR (Nujol, KBr, ν/cm−1): 3335 (m), 1900 (m), 1845 (m), 1790 (m), 1655 (m), 1615 (m), 1585 (m), 1245 (m), 1205 (m), 1170 (m), 1050 (m), 975 (m), 875 (m), 825 (s), 755 (s), 660 (s), 605 (s), 580 (s). Anal. Calcd for C39H69CaN3OSi2 (691.46 g/mol): C, 67.67; H, 10.05; Ca, 5.79; N, 6.07. Found: C, 67.35; H, 10.45; Ca, 5.69; N, 6.27. Synthesis of [2-MeOC 6 H 4 NC(tBu)N(C 6 H 3 -iPr 2 -2,6)]SmN(SiMe3)2(THF) (2Sm). A solution of 2-MeOC6H4NHC(tBu)N(C6H3-iPr2-2,6) (0.200 g, 0.55 mmol) in toluene (10 mL) was added to a solution of [(Me3Si)2N]2Sm(THF)2 (0.335 g, 0.55 mmol) in toluene (10 mL) at room temperature. The reaction mixture was stirred for 1 h, and then volatiles were removed in vacuum. The solid residue was dissolved in hexane (40 mL), and the resulted solution was centrifuged. Slow concentration of the hexane solution at room temperature resulted in the formation of complex 2Sm as black crystals. The mother liquid was decanted; the crystals were washed with cold hexane and dried in a vacuum for 30 min. Complex 2Sm was isolated in 50% yield (0.209 g). IR (Nujol, KBr, ν/cm−1): 2737 (m), 2028 (m), 1790 (m), 1670 (m), 1625 (m), 1584 (m), 1485 (m), 1360 (m), 1245 (m), 1205 (m), 1170 (m), 1110 (m), 1030 (m), 935 (m), 875 (m), 820 (m), 788 (s), 725 (m), 660 (s), 605 (s), 580 (s), 514 (s). Anal. Calcd for C34H59N3O2Si2Sm (762.41 g/mol): C, 54.57; H, 7.93; N, 5.61; Sm, 20.09. Found: C, 54.20; H, 7.66; N, 5.39; Sm, 19.88. Synthesis of [2-Ph2P(O)C6H4NC(tBu)N(C6H3-Me2-2,6)]YbN(SiMe3)2 (3Yb). A solution of 2-[Ph2P(O)]C6H4NHC(tBu)N(2,6-Me2C6H3) (0.360 g, 0.67 mmol) in toluene (10 mL) was added to a solution of [(Me3Si)2N]2Yb(THF)2 (0.428 g, 0.67 mmol) in toluene (10 mL) at room temperature. The reaction mixture was stirred for 1 h, and the volatiles were removed in vacuum. The solid residue was dissolved in hexane (40 mL). Slow concentration of the hexane solution at room temperature resulted in the formation of complex 3Yb as black crystals. The mother liquid was decanted, and the crystals were washed with cold hexane and dried in vacuum for 30 min. Complex was isolated in 84% yield (0.56 g, 0.56 mmol). 1H NMR (400 MHz, C6D6) δ = 0.08, 0.42 (s, together 18H, SiMe3), 1.16 (s, 9H, C(CH3)3), 2.07(s, 3H, CH3), 2.13 (s, 3H, CH3), 6.35−6.37 (m, 1H, C6H4), 6.65−6.69 (m, 1H, C6H4), 7.66−7.68 (m, 1H, C6H4), 7.51−7.54 (m, 1H, C6H4P), 6.94−6.96 (m, 3H, p-CH, Ph, and NC6H3Me2), 7.00−7.03 (m, 4H, o-CH, Ph) 7.08−7.11 (m, 6H, m-CH, Ph, and NC6H3 Me2). 13 C NMR (101 MHz, C6D6) δ = 2.3, 4.9 (SiCH3), 18.0 (CH3), 18.6 (CH3), 32.3 (C(CH3)), 41.1 (C(CH3)), 117.7 (C6H4), 132.2 (C6H4), 132.3 (C6H4), 133.1 (C6H4), 120.0 (C6H3Me2), 128.97 (Ph), 129.02 (Ph), 130.10 (Ph), 130.80 (C6H3Me2), 134.6 (Ph), 134.7 (Ph), 158.33 (C6H4), 158.8 (C6H3Me2), 171.5 (NCN). IR (Nujol, KBr, ν/cm−1): 1900 (s), 1845 (s), 1790 (s), 1669 (s), 1604 (s), 1577 (s), 1538 (s), 1403 (w), 1311 (s), 1265 (w), 1246 (w), 1223 (w), 1203 (w), 1165 (s) (s), 1153 (s), 1133 (m), 1121 (s), 1100 (s), 1092 (s), 1071 (s), 1029 (s), 998 (w), 947 (w), 825 (w), 755 (w), 660 (w), 580 (w). Anal. Calcd for C43H57N3OPSi2Yb (856.08 g/mol): C, 56.12; H, 6.70; N, 4.90; Yb, 20.21. Found: C, 55.84; H, 6.38; N, 4.77; Yb, 20.20.

Complexes 1Sm, 1Yb, 1Ca, 2Sm, 2Yb, and 3Yb proved to be efficicent catalysts for styrene hydrophoshination with both PhPH2 and Ph2PH. They enable addition of PhPH2 to styrene with extremely high chemoselectivity and to afford a monoaddition productsecondary phosphine (PhCH2CH2)PhPH. For both phosphines hydrophosphination reactions are exceptionally regioselective and provide formation only of the anti-Markovnikov addition product. Within the series of complexes coordinated by the same amidinate ligand catalytic activity decreases in the following order 1Ca ≥ 1Sm > 1Yb with TOF ≈ 0.3−0.7 h−1. Application of tridentate amidinate ligand allowed one to increase the catalytic activity vs complexes of the same metals coordinated by bidentate amidinate. Complexes 1Sm, 1Yb, 1Ca, 2Sm, 2Yb, and 3Yb enable addition of PhPH2 to an internal triple CC bond of tolane, affording mixtures of E- and Z-izomers.

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EXPERIMENTAL SECTION

General Considerations. All experiments were performed in evacuated tubes using standard Schlenk-flask or glovebox techniques with rigorous exclusion of traces of moisture and air. After drying over KOH, THF and DME were purified by distillation from sodium/ benzophenone ketyl, hexane, and toluene by distillation from sodium/ triglyme benzophenone ketyl prior to use. C6D6 toluene-d8 and THFd8 were dried with sodium/benzophenone ketyl and condensed in vacuum prior to use. [(Me3Si)2N]2M(THF)2 (M = Yb,16 Sm,17 Ca18), 2-MeOC 6 H 4 NC(tBu)NH(2,6-R 2 C 6 H 3 ), 22a and 2-[Ph 2 P(O)]C6H4NHC(tBu) = N(2,6-Me2C6H3)22b were prepared according to literature procedures. Diphenylphosphine and phenylphosphine were donated by Synor Ltd., vacuum distilled over CaH2, and then degassed by freeze−pump−thaw methods. Instruments and Measurements. NMR spectra were recorded on a Bruker DPX 200 or Bruker Avance DRX-400 spectrometer. Chemical shifts for 1H and 13C1{H} spectra were referenced internally using the residual solvent resonances and are reported relative to TMS. Lanthanide metal analysis was carried out by complexometric titration.31 C, H, N elemental combustion analysis was performed in the microanalytical laboratory of IOMC. Synthesis of [tBuC(NC6H3-2,6-iPr2)2]SmI(THF)2 (1SmI). A solution of tBuC(NC6H3-2,6-iPr2)2K (1.345 g, 2.93 mmol) in THF (15 mL) was added to a solution of SmI2(THF)3 (1.825 g, 2.93 mmol) in THF (20 mL) at room temperature, and the reaction mixture was stirred at 40 °C for 24 h. The precipitate of KI was separated by centrifugation, and the volatiles were removed in vacuum. The solid residue was dissolved in toluene (15 mL), the resulting solution was centrifuged, and toluene was removed in a vacuum. Complex 1SmI was obtained after recrystallization of the remaining solid by slow concentration of the THF/hexane (1:2) solution at room temperature. Complex 1SmI was isolated as brown crystals in 72% yield (1.783 g). IR (Nujol, KBr, ν/cm−1): 1614 (m), 1585 (m), 1259 (m), 1155 (m), 1108 (m), 1027 (m), 926 (s), 767 (s). Anal. Calcd for C41H67IN2O3Sm (913.22 g/ mol): C, 53.92; H, 7.39; N, 3.06; Sm 16.46. Found: C, 53.59; H, 7.02; N, 2.80; Sm, 16.17. Synthesis of [tBuC(NC6H3-2,6-iPr 2)2]SmN(SiMe3 )2 (1Sm). A solution of [tBuC(NC6H3-2,6-iPr2)2SmI(THF)2] (1.302 g, 1.55 mmol) in THF (15 mL) was added to a solution of NaN(SiMe3)2 (0.284 g, 1.55 mmol) in THF (10 mL) at room temperature, and the reaction mixture was stirred at room temperature for 24 h. The precipitate of NaI was separated by centrifugation, and the volatiles were removed in vacuum. The solid residue was dissolved in hexane (15 mL), and the solution was centrifuged. The solution was concentrated, and the resulted viscous oil was cooled at −18 °C to give brown crystals of 1Sm. The crystals were washed with cold hexane and dried in vacuum for 30 min at room temperature. Complex 1Sm was isolated in 57% yield (0.647 g). IR (Nujol, KBr, ν/cm−1): 3334 (m), 1902 (m), 1845 (m), 1655 (m), 1615 (m), 1585 (m), 1245 (m), 1205 (m), 1170 (m), 1050 (m), 975 (m), 875 (m), 825 (s), 755 (s), 660 (s), 580 (s). Anal. Calcd for C35H61N3Si2Sm (730.40 g/mol): C, G

DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry X-ray Crystallography. The X-ray data for 1Ca, 1Sm, 1Yb, 1SmI, 2Sm, and 3Yb were collected on Agilent Xcalibur E (1Ca, 2Sm, 3Yb) and Bruker Smart Apex (1Sm, 1Yb, 1SmI) diffractometers (graphitemonochromated, Mo Kα radiation, ω-scan technique, λ = 0.71073 Å, T = 100(2) K). The systematic pseudomerohedrically twinning of the crystal of 1Ca, 1Sm, and 1Yb afforded an empirical absorption correction using the program TWINABS. 32 SADABS 33 and ABSPACK34 were used to perform area-detector scaling and absorption corrections for 1SmI, 2Sm, and 3Yb. The structures were solved by direct methods and refined on F2 using SHELXTL.35 For the refinements of 1Ca, 1Sm, and 1Yb a HKLF5 formatted data file was used. A batch scaling factor was introduced to describe the twin volume fractions, resulting in a 0.458/0.542 (1Ca), 0.425/0.575 (1Sm), and 0.505/0.495 (1Yb) ratio for the volumes of domains 1 and 2, respectively. All non-hydrogen atoms were found from Fourier syntheses of electron density and refined anisotropically. All hydrogen atoms were placed in geometrically idealized positions and treated as riding with Uiso(H) = 1.2Ueq (Uiso(H) = 1.5 Ueq for the hydrogen atoms in CH3 groups) of their parent atoms. Crystal data and details of data collection and structure refinement for 1Ca, 1Sm, 1Yb, 1SmI, 2Sm, and 3Yb are given in Table S1 (Supporting Information). The CCDC files 1430019−1430024 contain supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via ccdc.cam.ac.uk/products/csd/ request.

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(6) Molander, G. A.; Romero, J. A. C. Chem. Rev. 2002, 102, 2161− 2186. (7) (a) Hong, S.; Marks, T. J. Acc. Chem. Res. 2004, 37, 673−686. (b) Müller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M. Chem. Rev. 2008, 108, 3795−3892. (c) Hultzsch, K. C. Adv. Synth. Catal. 2005, 347, 367−391. (8) (a) Kawaoka, A. M.; Marks, T. J. J. Am. Chem. Soc. 2005, 127, 6311−6324. (b) Kawaoka, A. M.; Marks, T. J. J. Am. Chem. Soc. 2004, 126, 12764−12765. (c) Kawaoka, A. M.; Douglass, M. R.; Marks, T. J. Organometallics 2003, 22, 4630−4632. (d) Douglass, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 2001, 123, 10221−10238. (e) Douglass, M. R.; Marks, T. J. J. Am. Chem. Soc. 2000, 122, 1824−1825. (f) Motta, A.; Fragalà, I. L.; Marks, T. J. Organometallics 2005, 24, 4995−5003. (g) Takaki, K.; Koshoji, G.; Komeyama, K.; Takeda, M.; Shishido, T.; Kitani, A.; Takehira, K. J. Org. Chem. 2003, 68, 6554−6565. (h) Takaki, K.; Takeda, M.; Koshoji, G.; Shishido, T.; Takehira, K. Tetrahedron Lett. 2001, 42, 6357−6360. (i) Hu, H.; Cui, C. Organometallics 2012, 31, 1208−1211. (9) Weiss, C. J.; Marks, T. J. Dalton Trans. 2010, 39, 6576−6588. (10) (a) Harrison, K. N.; Marks, T. J. J. Am. Chem. Soc. 1992, 114, 9220−9221. (b) Bijpost, E. A.; Duchateau, R.; Teuben, J. H. J. Mol. Catal. A: Chem. 1995, 95, 121−128. (11) (a) Harder, S. Angew. Chem., Int. Ed. 2004, 43, 2714−2718. (b) Yasuda, H.; Ihara, E.; Hayakawa, T.; Kakehi, T. J. Macromol. Sci., Part A: Pure Appl.Chem. 1997, 34 (10), 1929−1944. (12) Ruspic, C.; Spielmann, J.; Harder, S. Inorg. Chem. 2007, 46, 5320−5326. (13) (a) Basalov, I. V.; Roşca, S. C.; Lyubov, D. M.; Selikhov, A. N.; Fukin, G. K.; Sarazin, Y.; Carpentier, J.-F.; Trifonov, A. A. Inorg. Chem. 2014, 53, 1654−1661. (b) Basalov, I. V.; Dorcet, V.; Fukin, G. K.; Sarazin, Y.; Carpentier, J.-F.; Trifonov, A. A. Chem. - Eur. J. 2015, 21, 6033−6036. (14) (a) Edelmann, F. T. Coord. Chem. Rev. 1994, 137, 403−481. (b) Barker, J.; Kilner, M. Coord. Chem. Rev. 1994, 133, 219−300. (c) Coles, M. P. Dalton Trans. 2006, 985−1001. (15) (a) Basalov, I. V.; Lyubov, D. M.; Fukin, G. K.; Shavyrin, A. S.; Trifonov, A. A. Angew. Chem., Int. Ed. 2012, 52, 3444−3447. (b) Heitmann, D.; Jones, C.; Mills, D. P.; Stasch, A. Dalton Trans. 2010, 39, 1877−1882. (c) Wedler, M.; Noltemeyer, M.; Pieper, U.; Schmidt, H.-G.; Stalke, D.; Edelmarin, F. T. Angew. Chem., Int. Ed. Engl. 1990, 29, 894−896. (d) Yan, L.; Liu, H.; Wang, J.; Zhang, Y.; Shen, Q. Inorg. Chem. 2012, 51, 4151−4160. (16) Tilley, T. D.; Andersen, R. A.; Zalkin, A. J. Am. Chem. Soc. 1982, 104, 3725−3727. (17) Evans, W. J.; Drummond, D. K.; Zhang, H.; Atwood, J. L. Inorg. Chem. 1988, 27, 575−579. (18) Westerhausen, M.; Hartmann, M.; Makropoulos, N.; Wieneke, B.; Wieneke, M.; Schwarz, W.; Stalkec, D.; Naturforsch, Z. Z. Naturforsch., B: J. Chem. Sci. 1998, 53, 117. (19) Loh, C.; Seupel, S.; Görls, H.; Krieck, S.; Westerhausen, M. Eur. J. Inorg. Chem. 2014, 2014, 1312−1321. (20) Basalov, I. V.; Lyubov, D. M.; Fukin, G. K.; Cherkasov, A. V.; Trifonov, A. A. Organometallics 2013, 32, 1507−1516. (21) Tolpygin, A. O.; Cherkasov, A. V.; Fukin, G. K.; Trifonov, A. A. Inorg. Chem. 2014, 53, 1537−1543. (22) (a) Rad’kov, V. Yu.; Skvortsov, G. G.; Lyubov, D. M.; Cherkasov, A. V.; Fukin, G. K.; Shavyrin, A. S.; Cui, D.; Trifonov, A. A. Eur. J. Inorg. Chem. 2012, 2012, 2289−229. (b) Tolpygin, A. O.; Glukhova, T. A.; Cherkasov, A. V.; Fukin, G. K.; Aleksanyan, D. V.; Cui, D.; Trifonov, A. A. Dalton Trans. 2015, 44, 16465−16474. (23) Evans, W. J.; Champagne, T. M.; Ziller, J. W. Organometallics 2007, 26, 1204−1211. (24) Jenter, J.; Gamer, M. T.; Roesky, P. W. Organometallics 2010, 29, 4410−4413. (25) Zhang, X. W.; Maunder, G. H.; Gieβmann, S.; MacDonald, R.; Ferguson, M. J.; Bond, A. H.; Rogers, R. D.; Sella, A.; Takats, J. Dalton Trans. 2011, 40, 195−210. (26) Edelmann, F. T. Adv. Organomet. Chem. 2008, 57, 183−352.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.5b02450. Crystallographic data for 1Ca, 1Yb, 1Sm, 1SmI, 2Sm, and 3Yb (CIF) Representative 1H and 13C NMR spectra of ytterbium and calcium complexes (PDF)

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AUTHOR INFORMATION

Corresponding Author

*Phone: 007 831 4623532. Fax: 007 831 4627497. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The study was supported by the Russian Foundation for Basic Research . We thank Synor Ltd. and personally Dr. A. Tatarnikov for donation of PhPH2 and Ph2PH.

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REFERENCES

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DOI: 10.1021/acs.inorgchem.5b02450 Inorg. Chem. XXXX, XXX, XXX−XXX