Versatile Coordination Modes of Triphospha-1,4-pentadiene-2,4

Article pubs.acs.org/IC

Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

Versatile Coordination Modes of Triphospha-1,4-pentadiene-2,4diamine Anup K. Adhikari, Toni Grell, Peter Lönnecke, and Evamarie Hey-Hawkins* Faculty of Chemistry and Mineralogy, Institute of Inorganic Chemistry, Johannisallee 29, D-04103 Leipzig, Germany S Supporting Information *

ABSTRACT: 1,3,5-Triphospha-1,4-pentadiene-2,4-diamine reacts with [M(CO)4L] (M = Mo, L = nbd (norbornadiene); M = W, L = 2 CH3CN) to give the chelate complexes [M(CO)4(PMes{C(NHCy)PMes}2-κP1,P3)]. In contrast, an unusual intramolecular rearrangement occurred with [Cu(CH3CN)4]PF6 leading to the dimeric copper(I) complex [Cu(CNCy){PHMesPMesC(NHCy)PMes-κP1,P3}]2(PF6)2. The mechanism of the rearrangement was supported by quantum-mechanical calculations. The transition-metal complexes were characterized by multinuclear NMR spectroscopy, mass spectrometry, infrared spectroscopy, and X-ray crystallography.

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INTRODUCTION Ligands containing soft1 phosphorus and hard nitrogen donor atoms have been investigated intensively over the past decades.2 Among the variety of P,N ligand systems, pincer ligands and their metal complexes have received interest due to their high stability, versatility, and activity.3 The introduction of a PC functionality in a pincer ligand enhances the reactivity remarkably.4 The chemistry of low-coordinate phosphorus compounds, such as phosphinidenes and phosphaalkenes, is an active research area,5 as compounds with PC double bonds possess low-lying π* orbitals, which can act as effective π acceptors in the coordination of transition metals.5g,6 The η1 coordination mode of phosphaalkenes toward metal atoms or ions is common, but the η 2 coordination mode of phosphaalkenes is also known (Figure 1).5v,6 Chelating

RESULTS AND DISCUSSION The reaction of 1,3,5-triphospha-1,4-pentadiene-2,4-diamine (1) with 1 equiv of [M(CO)4L] (M = Mo, L = nbd; M = W, L = 2 CH3CN) gave the corresponding molybdenum(0) and tungsten(0) complexes [M(CO)4(PMes{C(NHCy)PMes}2κP1,P3)] (M = Mo (2), M = W (3)), in which 1 coordinates via the two terminal phosphorus atoms in a cis arrangement resulting in a six-membered ring (Scheme 1). Scheme 1. Synthesis of Mo Complex 2 and W Complex 3

Complexes 2 and 3 were isolated as air- and moisture-stable crystalline orange (2) or dark red (3) solids suitable for singlecrystal X-ray diffraction studies. In both complexes the metal center has an almost perfect octahedral coordination sphere (Figure 2 for 2; Supporting Information for 3). The coordination of the phosphorus atoms is in accordance with the hard-soft acid-base (HSAB) principle, as both the phosphorus atom and the group 6 metal atoms are soft;1 the six-membered rings have a boat conformation (Figure 3). The P−C bond lengths of the central P2 atom from 1.852(2) to 1.872(2) Å correspond to single bonds.5k,8 In contrast, the

Figure 1. Different bonding modes of phosphaalkenes in metal complexes.

phosphaalkene complexes have also been described.7 Recently, we reported the synthesis of 1,3,5-triphospha-1,4-pentadiene2,4-diamine (1) with a PC(N)−P−C(N)P arrangement, which contains P, N, and PC double bonds as potential donors.8 Here, we report the coordination behavior of 1 toward molybdenum(0), tungsten(0), and copper(I). © XXXX American Chemical Society

Received: January 10, 2018

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DOI: 10.1021/acs.inorgchem.8b00067 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

shorter than a carbon−nitrogen single bond.9 Both observations indicate a conjugation of the lone pair of electrons on the nitrogen atoms with the terminal PC bonds. The M−P bond lengths in 2 and 3 are comparable with other reported phosphaalkene complexes, such as cis-[Mo(CO)4(1-PPh2-2CHPMes*-C6H4-κP,P′)] (Mes* = 2,4,6-tBu3C6H2), cis[W(CO) 4(PhPCPh2-κP)2], [W(CO)5(RPCHCHMe2κP)] (R = Ph, tBu, Men (Men = menthyl)), [W(CO)5(RP C(2-C6H4OMe)OEt-κP)] (R = CH(NMe2)2, tBu), [W(CO)5(Me3SiPC(2-C6H4Me)OEt-κP)].10,11 In comparison, the M−P bonds in (diphosphazane)molybdenum(0) tetracarbonyl complexes12 are shorter and in (diphosphinidenecyclobutene)molybdenum(0) tetracarbonyl complexes13 longer than observed for 2 and 3. The M−CO bonds trans to the phosphorus atoms of the bidentate ligand 1 are shorter (∼1.98 Å) than the other two M−CO bonds (∼2.04 Å), which is due to the weaker π-acid character of the phosphaalkene group compared to the carbonyl group. The 31P{1H} NMR spectra display a triplet (14.2 ppm for 2, 17.5 ppm for 3) for the central phosphorus atom (P2) (−10.9 ppm in 1)8 and a doublet (80.5 ppm for 2, 55.8 ppm for 3) for the terminal phosphorus atoms (A2B spin system) (97.0 and 102.4 ppm in 1).8 A similar effect was also observed in inversely polarized phosphaalkenes reported by L. Weber and coworkers.11f The 2JPP coupling constants in 2 and 3 (142 and 141 Hz, respectively) are larger than those in the free ligand 1 (2JPP 9 and 59 Hz).8 For complex 3, satellites due to coupling to 183 W (I = 1/2; natural abundance: 14.31%) are observed for the doublet. The 1JPW coupling constant is 236 Hz, also suggesting a cis coordination of the ligand to the W(CO)4 fragment.14 For local C2v symmetry, four absorptions would be expected in the infrared spectra of complexes 2 and 3; only three intense ν(CO) bands in the region of 1860−2013 cm−1 are observed indicating some overlap of absorptions.15 When [Cu(CH3CN)4]PF6 was reacted with 1, the unusual dimeric copper(I) complex 4 was obtained (Scheme 2). In this reaction, a new P−P bond is created between the two neighboring phosphorus atoms of the starting material 1. As 1,3,5-triphospha-1,4-pentadiene-2,4-diamine (1) is obtained as one of three products by insertion of cyclohexyl isonitrile into the P−P bonds of [P4Mes4]2−,8 the reaction observed here between 1 and [Cu(CH3CN)4]PF6 can be regarded as a partway reverse reaction. The molecular structure of 4 (Figure 4) reveals that a rearrangement of 1 occurred during the reaction. Density functional theory (DFT) calculations were performed to gain

Figure 2. Molecular structure of 2. Thermal ellipsoids are set at 50% probability (H atoms other than N−H and disordered diethyl ether molecule are omitted for clarity). Selected bond lengths [Å] and bond angles [deg] of 2 (values of 3 (molecular structure not shown) in []): P2−C1 1.872(2) [1.872(2)], P2−C2 1.858(2) [1.852(2)], P1−C1 1.709(2) [1.712(2)], P3−C2 1.715(2) [1.714(2)], C1−N1 1.358(2) [1.352(2)], C2−N2 1.353(2) [1.356(2)], P1−M1 2.5121(5) [2.5117(4)], P3−M1 2.5116(5) [2.4921(4)], M1−C43 1.987(2) [1.975(2)], M1−C44 1.972(2) [1.985(2)], M1−C42 2.032(2) [2.028(2)], M1−C45 2.041(2) [2.037(2)], C42−O1 1.144(3) [1.148(2)], C43−O2 1.148(3) [1.155(2)], C44−O3 1.155(3) [1.155(2)], C42−O4 1.145(3) [1.146(2)], N1−C1−P2 111.8(1) [109.9(1)], N2−C2−P2 115.0(1) [114.4(2)], N1−C1−P1 132.2(1) [132.5(1)], N2−C2−P3 130.5(1) [130.0(1)], P2−C1−P1 115.47(9) [117.20(8)], P2−C2−P3 113.59(9) [114.47(8)], C2−P2−C1 109.29(8) [110.65(7)], C1−P1−M1 121.74(6) [119.86(5)], C2− P3−M1 121.61(6) [122.37(5)], P3−M1−P1 86.37(2) [86.47(1)], M1−C42−O1 178.1(2) [177.3(2)], M1−C43−O2 178.5(2) [177.5(2)], M1−C44−O3 178.8(2) [177.4(2)], M1−C45−O4 176.5(2) [178.3(2)].

Figure 3. Boat conformation of the six-membered rings in 2 (left) and 3 (right).

terminal P−C bond lengths (1.709(2) to 1.715(2) Å) indicate double bond character but are yet longer than in reported phosphaalkenes (ca. 1.68 Å).5,6 Furthermore, the C−N bond lengths (ca. 1.35 Å) of the sp2 carbon atoms (C1/C2) are Scheme 2. Synthesis of Copper(I) Complex (4)

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proton to a terminal P atom) to give the intermediate I2 (ΔE = +3.9 kJ/mol). Subsequently, an intramolecular rearrangement takes place that includes the formation of the P−P bond and the elimination of a cyclohexyl isocyanide, which coordinates at the CuI cation leading to I3 (ΔE = +28.4 kJ/mol). Interestingly, the sum of all energies in this process going from 1 to I3 is almost zero. Dimerization of I3 finally gives product 4 (ΔE = −117.6 kJ/mol). However, no transition state was found for the transformation from I2 to I3. We expect that at least two transition states are involved in this reaction step. The copper atom in complex 4 is coordinated in a distorted tetrahedral fashion. The P1−Cu1−P3 bond angle of the fivemembered ring is much smaller (89.04(3)°) than the other bond angles (C1−P3−Cu1 (112.67(9)°), P2−C1−P3 (118.8(1)°), C1−P2−P1 (102.21(9)°) and P2−P1−Cu1 (105.53(3)°). The five-membered ring formed by P2−P1− Cu1−P3−C1 exhibits a twist conformation. The P−P (2.194(1) Å) and the P2−C1 (1.829(3) Å) bonds are in the range of single bonds (P−P 2.21 Å,16 P−C 1.85 Å5k,8), while the P3−C1 bond length of 1.747(3) Å indicates multiple bond character but is longer than reported for phosphaalkenes.5,6 The C1−N1 bond length is 1.328(3) Å, which is shorter than a carbon−nitrogen single bond,9 suggesting conjugation of the lone pair of electrons at nitrogen with the PC bond. The Cu1−P1 (2.2932(7) Å) and the Cu1−P3/Cu1−P3′ bond lengths (2.3380(7) and 2.3756(8) Å) are comparable to other copper(I) phosphine complexes.17 The molecule resides on a crystallographic inversion center, which is located in the center of the central planar Cu2P2 ring. The Cu1···Cu1′ distance (2.7708(6) Å) is shorter than the sum of the van der Waals radii (rCu = 1.96 ± 0.10 Å),8,18a−f and the Cu1−P3−Cu1′ bond angle is very small (72.00(2)°), indicating a weak cuprophilic interaction,8,17,18 which is also supported by the calculated Löwdin and Mayer Cu−Cu bond order of 0.1904 and 0.1947, respectively.8 31 1 P{ H} NMR spectrum of 4 in CDCl3 displays a broad signal (−80.3 ppm at room temperature (RT) and −80.8 ppm at −50 °C), a broad doublet (−45.5 ppm at RT and −47.6 ppm at −50 °C) and a broad triplet (−24.6 ppm at RT and −28.4 ppm at −50 °C) with one sharp septet (−144.3 ppm at RT and −144.5 ppm at −50 °C) for the counterion hexafluorophosphate, at room temperature as well as at lower temperature

Figure 4. Molecular structure of the dication of 4. Thermal ellipsoids are set at 50% probability (two counterions (PF6−), H atoms other than N−H, P−H, and disordered THF molecules are omitted for clarity). Selected bond lengths [Å] and bond angles [deg]: P1−P2 2.194(1), P2−C1 1.829(3), P3−C1 1.747(3), C1−N1 1.328(3), P1− Cu1 2.2932(7), P3−Cu1 2.3380(7), P3−Cu1′ 2.3756(8), Cu1−C35 1.926(3), N2−C35 1.152(3), N1−C1−P2 117.6(2), N1−C1−P3 122.4(2), P2−C1−P3 118.8(1), C1−P2−P1 102.21(9), P2−P1−Cu1 105.53(3), P1−Cu1−P3 89.04(3), C1−P3−Cu1 112.67(9), Cu1− P3−Cu1′ 72.00(2), P3−Cu1−P3′ 108.00(2), P3−Cu1−C35 117.69(8), P1−Cu1−C35 120.26(3), P3′−Cu1−C35 119.09(9), P3′−Cu1−P1 97.45(3).

insight into the mechanism of the unusual rearrangement (for details see the Supporting Information). The formation of 4 can be rationalized as follows (Scheme 3): The first step of the reaction is the coordination of the CuI cation by the terminal phosphorus atoms of 1 leading to the formation of I1 (ΔE = −32.8 kJ/mol), which is analogous to the chelate complexes 2 and 3. The CuI ion facilitates a tautomerization reaction (N−H

Scheme 3. Proposed Mechanism of Formation of Copper(I) Complex 4

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mmol) in THF (15 mL) at −78 °C. The color of the solution changed to dark red after 15 min. The red solution was warmed to room temperature over several hours and stirred overnight. The solvent was removed under vacuum, and the resulting red solid was extracted with Et2O (15 mL). Dark red prisms of 3 appeared after 1 d at room temperature. Yield: 0.255 g (95%). 1H NMR (C6D6, 298 K): δ = 0.26−1.50 (m, 22 H, cyclohexyl protons), 1.95 (s, 3 H, p-CH3 in Mes of P2), 2.02 (s, 6 H, p-CH3 in Mes of P1/P3), 2.72 (br, 6 H, o-CH3 in Mes of P2), 2.83−2.86 (bs, 12 H, o-CH3 in Mes of P1/P3), 4.49 (m, 2 H, NH), 6.75 (s, 4 H, m-H in Mes of P1/P3), 6.78 (s, 2 H, m-H in Mes of P2) ppm. 13C{1H} NMR (C6D6, 298 K): δ = 21.1−23.0 (MesCH3), 25.0−33.8 (cyclohexyl carbons), 56.7 (cyclohexyl carbon, NCH), 129.0−130.5 (m-CH in Mes), 134.6 (ipso-C in Mes), 140.0− 142.2 (C−CH3), 177.6 (t, 2JPC = 6.5 Hz, CO), 178.0 (t, 2JPC = 6.5 Hz, CO), 200.8 (m, PC), 206.3 (m, PC) ppm. 31P{1H} NMR (C6D6, 298 K): δ = 17.5 (t, 1 P, 2JPP = 141 Hz, P2), 55.8 (d, 2 P, 2JPP = 141 Hz, 1JPW = 236 Hz, P1/P3) ppm. FT-IR (KBr, cm−1): ν̃ = 3321 (s, NH), 2922 (m, CH, sp3), 2008 (s, CO), 1891 (s, CO), 1857 (s, CO), 1601 (m, PC). MS (ESI-LRMS, pos, n-hexane/CH3CN): m/z = 966.3 [M]+, 938.3 [M − CO]+. Anal. Calcd: C45H57N2O4P3W (966.72), calcd. C 55.91, H 5.94, N 2.90; found C 56.29, H 6.16, N 2.61%. mp 184−186 °C. 4: A suspension of [Cu(CH3CN)4]PF6 (0.125 g, 0.335 mmol) in THF (15 mL) was added dropwise to a solution of 1 (0.220 g, 0.328 mmol) in THF (15 mL) at −78 °C. The color of the solution changed to bright orange after 15 min. The orange solution was warmed to room temperature over several hours and stirred overnight. The solution was concentrated to 15 mL and layered with n-hexane (5 mL). Orange prisms of 4 appeared after 1 d at room temperature. Yield: 0.272 g (94%). 1H NMR (CDCl3, 298 K): δ = 0.31−3.14 (m, 44 H, cyclohexyl protons), 2.24−2.62 (54 H, CH3 in Mes), 4.27 (bs, 2 H, NH), 6.68 (br, 2 H, PH, 1JPH = 157 Hz), 6.46−7.01 (12 H, m-H in Mes) ppm. 1H NMR (CDCl3, 223 K): δ = 0.36−3.10 (m, 44 H, cyclohexyl protons), 0.95−2.76 (54 H, CH3 in Mes), 4.10 (br, 2 H, NH), 6.45 (bd, 2 H, PH), 6.39−7.04 (12 H, m-H in Mes) ppm. 13 C{1H} NMR (CDCl3, 298 K): δ = 21.1−24.7 (Mes-CH3), 25.6−32.2 (cyclohexyl carbons), 54.4−60.4 (cyclohexyl carbon, NCH), 115.3− 128.5 (ipso-C in Mes), 129.9−131.2 (m-CH in Mes), 137.8−145.3 (C−CH3, CyNC), 195.7 (PC) ppm. 31P{1H} NMR (CDCl3, 298 K): δ = −24.6 (bt, 1 P, P2), −45.5 (bd, 1 P, P1), −80.3 (br, 1 P, P3), −144.3 (sept, 1 P, 1JPF = 712.7 Hz, PF6) ppm. 31P{1H} NMR (CDCl3, 223 K): δ = −28.4 (bt, 1 P, P2), −47.6 (bd, 1 P, P1), −80.8 (br, 1 P, P3), −144.5 sept, 1 P, PF6, 1JPF = 713 Hz) ppm. FT-IR (KBr, cm−1): ν̃ = 3301 (s, NH), 2934 (m, CH, sp3), 2190 (s, CN), 2378 (w, P−H), 1603 (s, PC). MS (ESI-HRMS, pos, CHCl3/CH3CN): m/z = 1185.4956 [M − 2 PF6 − Cu − 2 CyNC]+, 733.3011 [monomer − PF6]+, 624.2120 [monomer − PF6 − CyNC]+. Anal. Calcd: C82H114Cu2F12N4P8·4C4H8O (2047.02), calcd. C 57.51, H 7.19, N 2.74; found C 56.25, H 6.90, N 2.73%. mp 177−180 °C. X-ray data were collected with a Gemini CCD diffractometer (Rigaku Inc.), λ(Mo Kα) = 0.710 73 Å, T = 130(2) K, empirical absorption corrections with SCALE3 ABSPACK.24 The structures were solved by dual space methods with SHELXT-2014. Structure refinement was done with SHELXL-201725 by using full-matrix leastsquares routines against F2. With the exception of NH and PH fragments all hydrogen atoms were calculated on idealized positions. The pictures were generated with the program Diamond.26 CCDC 1814283 (2), CCDC 1814284 (3), and CCDC 1814285 (4) contain the supplementary crystallographic data for this paper. Additional crystallographic information is available in the Accession Codes. Crystal Data for 2. C49H67MoN2O5P3, M = 952.89, triclinic, space group P1̅, a = 12.3053(4) Å, b = 12.7264(4) Å, c = 18.0638(4) Å, α = 99.842(2)°, β = 95.997(2)°, γ = 114.441(3)°, V = 2488.6(1) Å3, Z = 2, ρcalcd = 1.272 Mg·m−3, μ(Mo Kα) = 0.405 mm−1, θmax = 32.68°, R = 0.0589, Rw = 0.1082 (all data), 16 729 independent reflections, 558 parameters, 7 restraints, residual electron density 1.658 and −0.833 e· Å−3. Crystal Data for 3. C45H57N2O4P3W, M = 966.68, monoclinic, space group P21/n, a = 15.4814(1) Å, b = 20.1559(1) Å, c = 15.4985(1) Å, β = 111.699(1)°, V = 4493.48(5) Å3, Z = 4, ρcalcd =

(−50 °C). The 1H NMR spectrum in CDCl3 also displays broad signals for the methyl protons and the aromatic protons at room temperature; however, these signals are getting sharper at lower temperature (−50 °C), which indicates dynamic behavior (monomer−dimer) of complex 4 in solution. The infrared spectrum of 4 shows sharp bands at 3302 cm−1 (ν(N− H)) and 2109 cm−1 (ν(CN)), for the coordinated cyclohexyl isocyanide ligand,19 and at 2378 cm−1 (ν(P−H)) for the secondary phosphine.

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CONCLUSION 1,3,5-Triphospha-1,4-pentadiene-2,4-diamine (1) reacts with group 6 metal(0) carbonyls (metal = molybdenum and tungsten) to give chelate complexes in which only the terminal phosphorus atoms coordinate to the metal center. In contrast, the reaction with copper(I) leads to an intramolecular rearrangement of 1 with P−P bond formation and elimination of cyclohexyl isocyanide. Further reactivity studies of 1 are underway.

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EXPERIMENTAL SECTION

General Remarks. All experiments were performed under dry nitrogen. Only the addition of metal complexes to a solution of 1 was performed in the dark. Solvents (tetrahydrofuran (THF) and Et2O) were dried and freshly distilled under nitrogen and kept over a potassium mirror or molecular sieves (4 Å). The NMR spectra were recorded at 25 °C with a Bruker Avance DRX 400 spectrometer (1H NMR: 400.13 MHz, 13C NMR: 100.16 MHz, 31P NMR: 161.97 MHz). Tetramethylsilane (TMS) was used as internal standard for 1H NMR spectra. 13C and 31P NMR experiments were referenced to TMS on the Ξ scale.20 In all 31P NMR experiments, 85% H3PO4 in water was used as external standard. Electrospray ionization mass spectrometry (ESI-MS) measurements were performed with a Bruker Daltonics FT-ICR-MS spectrometer (Type APEX II, 7 T). Elemental analyses were performed with a Heraeus VARIO EL oven. Infrared spectra were recorded with a spectrometer from PerkinElmer (System 2000) in the range from 4000 to 400 cm−1. The melting points (Gallenkamp) were determined in a capillary tube. Ligand 1,8 [Mo(CO)4(nbd)],21 and [Cu(CH3CN)4]PF622 were synthesized according to the literature. [W(CO)4(CH3CN)2] was synthesized by modification of the known literature procedure.23 2: A solution of [Mo(CO)4(nbd)] (0.091 g, 0.303 mmol) in THF (15 mL) was added dropwise to a solution of 1 (0.200 g, 0.298 mmol) in THF (15 mL) at −78 °C. The color of the solution changed to bright orange after 15 min. The orange solution was warmed to room temperature over several hours and stirred overnight. The solvent was removed under vacuum, and the resulting orange solid was extracted with Et2O (15 mL). Dark orange prisms of 2 appeared after 1 d at room temperature. Yield: 0.255 g (93%). 1H NMR (C6D6, 298 K): δ = 0.26−1.51 (m, 22 H, cyclohexyl protons), 1.95 (s, 3 H, p-CH3 in Mes of P2), 2.02 (s, 6 H, p-CH3 in Mes of P1/P3), 2.71 (br, 6 H, o-CH3 in Mes of P2), 2.83−2.87 (bs, 12 H, o-CH3 in Mes of P1/P3), 4.56 (m, 2 H, NH), 6.76 (s, 4 H, m-H in Mes of P1/P3), 6.78 (s, 2 H, m-H in Mes of P2) ppm. 13C{1H} NMR (C6D6, 298 K): δ = 21.1−23.2 (MesCH3), 25.0−33.8 (cyclohexyl carbons), 56.7 (cyclohexyl carbon, NCH), 129.0−130.4 (m-CH in Mes), 135.4 (m, ipso-C in Mes) 139.8−142.1 (C−CH3), 179.5 (br, CO), 180.0 (br, CO), 208.7 (m, PC), 216.0 (m, PC) ppm. 31P{1H} NMR (C6D6, 298 K): δ = 14.2 (t, 1 P, 2JPP = 142 Hz, P2), 80.5 (d, 2 P, 2JPP = 142 Hz, P1/P3) ppm. FT-IR (KBr, cm−1): ν̃ = 3323 (s, NH), 2923 (m, CH, sp3), 2013 (s, CO), 1902 (s, CO), 1860 (s, CO), 1601 (m, PC). MS (ESI-HRMS, pos, CH3Cl/CH3CN): m/z = 881.3 [M + H]+, 1781.5196 [2 M + Na]+. Anal. Calcd: C45H57MoN2O4P3·C4H10O (952.97), calcd. C 61.76, H 7.09, N 2.94; found C 61.76, H 6.77, N 2.94%. mp 178−181 °C. 3: A solution of [W(CO)4(CH3CN)2] (0.097 g, 0.256 mmol) in THF (15 mL) was added dropwise to a solution of 1 (0.170 g, 0.253 D


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Inorganic Chemistry 1.429 Mg·m−3, μ(Mo Kα) = 2.720 mm−1, θmax = 37.38°, R = 0.0463, Rw = 0.0632 (all data), 22 671 independent reflections, 513 parameters, residual electron density 1.790 and −1.694 e·Å−3. Crystal Data for 4. C98H146Cu2F12N4O4P8, M = 2047.02, monoclinic, space group P21/n, a = 19.0776(5) Å, b = 13.5866(4) Å, c = 20.0700(5) Å, β = 102.835(3)°, V = 5072.2(2) Å3, Z = 2, ρcalcd = 1.340 Mg·m−3, μ(Mo Kα) = 0.618 mm−1, θmax = 30.20°, R = 0.0976, Rw = 0.1445 (all data), 13 935 independent reflections, 635 parameters, 73 restraints, residual electron density 0.754 and −0.583 e·Å−3.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b00067. Molecular structure of 3, detailed theoretical calculations of the reaction mechanism for the formation of complex 4, multinuclear NMR and ESI mass spectra for 2, 3, and 4 (PDF) Reactivity to forming chelate complexes; characterization of transition-metal complexes (PDF) Accession Codes

CCDC 1814283−1814285 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Evamarie Hey-Hawkins: 0000-0003-4267-0603 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Support from the Deutscher Akademischer Austauschdienst (DAAD-GSSP doctoral grant for A.K.A.), the Studienstiftung des deutschen Volkes (doctoral grant for T.G.), and the Graduate School BuildMoNa is gratefully acknowledged. We thank M.Sc. B. Schwarze for measurement of several NMR spectra.

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DEDICATION Dedicated to Prof. Dr. Wolfgang Weigand on the occasion of his 60th birthday. REFERENCES

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