From a PGeP Pincer-Type Germylene to Metal Complexes Featuring Chelating (Ir) and Tripodal (Ir) PGeP Germyl and Bridging (Mn₂) and Chelating (Ru) PGeP Germylene Ligands

Abstract

Different coordination modes of a PGeP chloridogermyl ligand (Ge,P-chelating and P,Ge,P-tripodal) and a PGeP germylene ligand (P,Ge,P-bridging and Ge,P-chelating) have been identified in coordination compounds resulting from reactions of the PGeP pincer-type diphosphane-germylene Ge­(NCH2P t Bu2)2C6H4 (1) with iridium­(I), manganese(0), and ruthenium­(II) complex reagents. Germylene 1 reacted with [Ir2(μ-Cl)2(η4-cod)2] (cod = 1,5-cyclooctadiene) to give [Ir­{κ2 Ge,P-GeCl­(NCH2P t Bu2)2C6H4}­(η4-cod)] (2), which contains a Ge,P-chelating PGeP chloridogermyl ligand and an uncoordinated phosphane group that weakly interacts with the Ge atom. Carbon monoxide readily displaced the cod ligand of 2 to give the dicarbonyl derivative [Ir­{κ3 P,Ge,P-GeCl­(NCH2P t Bu2)2C6H4}­(CO)2] (3), in which the PGeP chloridogermyl ligand displays a P,Ge,P-tripodal coordination mode. A bridging germylene moiety has been identified in the binuclear derivative [Mn2{μ-κ3 P,Ge,P-Ge­(NCH2P t Bu2)2C6H4}­(CO)8] (4), which resulted from the treatment of [Mn2(CO)10] with germylene 1. The ruthenium complex [RuHCl­(CO)­{κ2 Ge,P-Ge­(NCH2P t Bu2)2C6H4}­(P i Pr3)] (5), which was isolated from the reaction of 1 with [RuHCl­(CO)­(P i Pr3)2], is the first transition-metal derivative of 1 in which the germylene moiety has not inserted into an M–M or M–Cl bond (M = transition metal), as it contains germylene 1 coordinated in a Ge,P-chelating mode, the resulting GeNCPRu ring being severely strained due to the short length of the coordinated CH2P t Bu2 arm, which also forces the germanium atom to be in an uncommon T-shaped environment. DFT calculations have been used to shed light on bonding features of complexes 2 and 5. The X-ray structures of 1–5 are also reported.

A Germylene Supported by Two 2‐Pyrrolylphosphane Groups as Precursor to PGeP Pincer Square‐Planar Group 10 Metal(II) and T‐Shaped Gold(I) Complexes

“…Given the ability of variousd eprotonated 2-phosphanylmethylpyrroles to act as chelating ligandsi nt ransition-metal complexes, [17] we decided to preparet he hitherto unknown phosphane-functionalized pyrrole HpyrmPtBu 2 (Scheme 1) with the aim of using it as ap recursor to aP GeP germylene, because the presence of the tBu 2 Pg roups not only would sterically protect the highly reactive Ge atom butc ould also stabilizet he molecule by alleviating the strong Lewis acidity of the divalent Ge atom through P-Ge interactions, as has been previously shown for the only hitherto reported PGeP germylenes Aa nd B ( Figure 1). [11][12][13] We prepared HpyrmPtBu 2 by heating2 -di-methylaminomethylpyrrole (HpyrmNMe 2 )w ith tBu 2 PH in the absence of any solventa t1 35 8C. This synthetic method, which is related to that previouslyu sed to prepare2 ,5-bis(diphenylphosphanylmethyl)pyrrole from 2,5-bis(dimethylaminomethyl)pyrrole and Ph 2 PH, [18] quantitativelyp rovided HpyrmPtBu 2 in one step from HpyrmNMe 2 ,b eing therefore much more convenient than alternative but low-yield methods used to prepare other 2-phosphanylmethylpyrroles (typically involving a LiAlH 4 reduction of the corresponding pyrrole-functionalized phosphane oxide, [17] whose preparation requires several steps [19] )or2,5-bis(diphenylphosphanylmethyl)pyrrole (by treating as olutiono fK PPh 2 in DMSO with 2,5-bis(trimethylammoniomethyl)pyrrole diiodide, [20] which should also be prepared [21] ).…”

“…Regarding metal-free PGeP pincer-type germylenes,o nly two specimens have so far been reported, namely,G e-(NCH 2 PtBu 2 ) 2 C 6 H 4 [11] and Ge(NC 6 H 4 PPh 2 ) 2 C 2 H 4 [12] (compounds A and B in Figure 1) and their transition-metal derivative chemistry has just started to be developed. [12][13][14] Both A and B are very prone to get their Ge atom inserted into MÀCl bonds to give chloridogermyld erivatives. It shouldb en oted that Figure 1.…”

The Transition Metal Chemistry of PGeP and PSnP Pincer Heavier Tetrylenes

“…Interestingly, the X‐ray diffraction (XRD) structures of XXV and XXVI demonstrated that both molecules have the P atoms in the plane defined by the EN 2 C 6 H 4 scaffold, at short distances from the corresponding E atom (3.320(2) Å and 3.320(2) Å for XXV ; 3.277(1) Å and 3.313(1) Å for XXVI ). DFT calculations, indicated a weak (but non‐negligible) overlap between the lone pair of each P atom and an antibonding σ*(E–N) orbital. The particular structures of these tetrylenes seem to be forced by the short length of their CH 2 P t Bu 2 side arms, which prevents a “normal” intramolecular donor–acceptor interaction between the lone pair of one P atom and the empty perpendicular p orbital of the E atom.…”

“…The reactions of germylene XXV with the homoleptic carbonyl dimers [Mn 2 (CO) 10 ] and [Co 2 (CO) 8 ] led to the C 2 ‐symmetric binuclear derivatives [Mn 2 {µ‐κ 3 P,Ge,P ‐Ge{NCH 2 P t Bu 2 } 2 C 6 H 4 }(CO) 8 ] ( 1 ) and [Co 2 {µ‐κ 3 P,Ge,P ‐Ge{NCH 2 P t Bu 2 } 2 (C 6 H 4 )}(CO) 6 ] ( 2 ), respectively (Figure ), in which the metal atoms are not bonded to each other. Therefore, these reactions, which involve an insertion of the Ge atom into the M–M bond of the binuclear reagent, lead to tetravalent germanium derivatives.…”

“…It its noteworthy that they all have been described in the last three years. Our contributions (compounds XXV , XXVI , XXIX and XXX , 2017–2019) have been complemented with results produced by Goicoechea's (compounds XXVII and XXVIII , 2018) and Tobita's (compound XXXI , 2019) research groups.…”